Technological scheme for the production of sulfuric acid by the contact method according to the "DK - DA" method

To comply with sanitary standards for large sulfuric acid plants, it is necessary to achieve an oxidation state of 99.5%. This degree is achieved on systems operating according to the scheme, called "double contact - double absorption" - DC - YES. Its essence lies in the fact that at the first stage of contacting the degree of conversion is about 90%. Before the gas is sent to the second stage of contacting, the main amount of SO3 is absorbed from the gas in the absorber, which, in accordance with the Le Chatelier principle, shifts the oxidation equilibrium towards the reaction product - sulfur trioxide and the degree of conversion of the remaining dioxide reaches 0.95 - 0.97. The overall degree of conversion is 99.5 - 99.7%, and the content of SO2 in the exhaust gases is reduced to a sanitary standard.

According to the scheme (see appendices), the roasting gas after coarse cleaning from dust in dry electrostatic precipitators at a temperature of about 300 ° C enters for fine cleaning in a hollow washing tower, which is irrigated with cold 75% sulfuric acid. When the gas is cooled, sulfur trioxide present in a small amount and water vapor condense in the form of tiny droplets. Arsenic oxides are dissolved in these drops, and a mist of sulfuric acid and arsenic is formed, which is partially captured in towers 1 and 2, filled with a packing of ceramic Raschig rings. In the same towers, dust residues, selenium and other impurities are simultaneously trapped. This produces contaminated sulfuric acid (about 8% of the total output), which is issued as non-standard products. The final purification of gas from the mist of sulfuric acid and arsenic is carried out in wet electrostatic precipitators 3. The preparation of gas for oxidation ends with drying it from water vapor with vitriol in towers with packing 4. A large number of equipment and gas ducts creates resistance in the system up to 2 * 10-2 MPa, therefore, to transport gas, a turbocompressor 5 is installed behind the drying section, which sucks gases from the furnace section through the gas purification and drying system and pumps it into the contact section of the shop.

The contact section consists of tubular heat exchangers 6 for heating the reaction gases and cooling the contacted gas and a contact apparatus 7. The gas cooled after the contact apparatus enters the absorption section of the workshop.

Sulfur trioxide absorption according to the reaction equation

SO3 + H2O > H2SO4 + 92000 J

carried out in towers packed with concentrated sulfuric acid. If absorption is carried out with water or dilute sulfuric acid, then over the absorbent, due to the high elasticity of water vapor, the interaction of SO3 and H2O occurs in the gas phase with the formation of tiny droplets of sulfuric acid mist, which is very difficult to capture.

The best in terms of absorption capacity is 98.3% sulfuric acid, which is characterized by negligible vapor pressure of H2O and SO3. Absorption towers 8 and 9 are irrigated with such acid, obtaining H2SO4 monohydrate as a product. If it is necessary to obtain oleum, then two towers are installed in series, and the monohydrate obtained in one tower is concentrated to oleum in the second.

Cooling of the acid heated during absorption is carried out in acid refrigerators 11. Further, from the receiving collectors 12, the acid is supplied by pumps 13 for irrigation of the towers and is partially pumped out to the finished product warehouse.

Settlement part

Drawing up a material balance

4 FeS2 + 11 O2 = 2 Fe2O3 + 8 SO2

We calculate for 1 ton of sulfur pyrite

2 SO2 + O2 > 2 SO3 SO3 + H2O > H2SO4

one). We calculate the mass of water in 1 ton of sulfur pyrite:

Dry pyrites: 1000 - 46 = 954 (kg)

2). We calculate the volume of air required for the combustion of pyrites:

a). We determine the sulfur content in dry pyrites:

b). We calculate the yield of cinder per 1 ton of dry pyrite:

160 is the stoichiometric amount of cinder obtained from the stoichiometric amount of pyrites.

in). We calculate the percentage of burnt sulfur:

G). We calculate the volume of air per 1 ton of dry pyrite:

where 700 and 7 are the coefficients derived from the stoichiometric equations for pyrite combustion;

m is the stoichiometric ratio of the number of oxygen molecules to the number of sulfur dioxide molecules.

We do not take into account the air consumption for the oxidation of SO2 to SO3, since the error is less than 1%.

e). We calculate the air consumption per 1 ton of wet pyrites:

3). We calculate the volume and mass of oxygen and nitrogen coming from the air. We assume that air contains 21% oxygen and 79% nitrogen:

1 mol = 22.4 l;

Similarly, we find nitrogen:

We calculate the amount of moisture supplied with air, assuming that the air enters at a temperature of 20 ° C and the degree of saturation with moisture is 0.5 (u = 0.5).

According to the reference book, with these parameters, the content of water vapor in the air is:

Calculate the amount of moisture brought with air into the furnace:

one). We calculate the mass of the resulting cinder per 1 ton of wet pyrites:

2). We calculate the amount of dry roasting gas formed:

This is the gas that comes out of the kiln after firing.

3). We calculate the content of the main components in the gas:

Amount of non-reacting component

4). We calculate the total amount of moisture coming from pyrite and air:

5). We calculate the volume and mass of the components of dry furnace gas:

We draw up the material balance of firing 1 ton of wet pyrite

FeS2 (dry)			Fe2O3 (cinder)
H2O with pyrites			Roasting gas
dry air
H2O (with air)

Productivity is 350t/day

FeS2 (dry)			Fe2O3 (cinder)
H2O with pyrites			Roasting gas
dry air
H2O (with air)

Weight balance discrepancy:

Compilation of the heat balance of the furnace for roasting sulfur pyrite

Heat input:

one). Heat supplied with dry pyrites:

• 2). Heat with dry air:
• 3). Heat supplied with pyrite moisture:

4). Heat supplied with air moisture:

• 5). Thermal effect of pyrite combustion reaction:
• 4 FeS2 + 11 O2 = 2 Fe2O3 + 8 SO2 + 13320 * CS burn.
• 13320 * CS burnout - the amount of heat released during the combustion of 1 kg of dry raw materials, taking into account burnt sulfur.

Heat consumption:

one). With cinder

It must be taken into account that only 10% of the cinder leaves the fluidized bed at a temperature of 748°C, and 90% of the cinder is carried away by gas at a temperature of 835°C.

Sogarka \u003d 0.84 kJ / kg * deg

• 2). With firing gas:
• 3). Heat loss:

taken equal to 3% of the heat input

4). Calculate the amount of heat that will go

a) for heating water in pyrites to a temperature of 24 to 100 ° C

b) to evaporate this water and heat the steam from 100°C to 835°C

c) for heating water vapor entering the furnace with air from 24 to 835 ° C

sulfuric acid production

5). We calculate the amount of heat that must be removed from the furnace using heat exchangers:

Thermal balance of the furnace

• 2.3 Calculation of furnace parameters
• one). Determine the intensity of the fluidized bed furnace:

Shows how many tons per day of dry ore is passed through 1 m2 of the furnace hearth.

W is the linear speed of the gas under operating conditions, m/s;

h is the degree of sulfur burnout in fractions;

TOG - the temperature of the roasting gas in K.

The practical intensity is taken for flotation pyrites from 9 to 10 tons, for crushed pyrites from 17 to 22 tons.

2). We calculate the volumetric intensity of the fluidized bed furnace:

H1 - approximate height of the cylindrical part of the furnace in m (8m).

3). We calculate the area of ​​the hearth of the furnace and its diameter:

П - productivity, t/day.

We accept the area of ​​the forechamber for loading pyrite: Ff = 3m2 and calculate the total area of ​​the hearth of the furnace:

4). We calculate the internal volume of the furnace:

Then the actual height of the cylindrical part will be equal to:

5). We calculate the volume of air required to burn 350 tons/day of pyrites.

To do this, from the previous calculations, we take the volume of air for burning 1 ton of dry pyrite (Vv (s) = 1789 m3), then the air consumption per hour, taking into account productivity, will be equal to:

6). We calculate the volume of roasting gas, taking into account the performance:

from the previous calculation we take the volume of roasting gas per 1 ton of dry pyrite

VG = 1595 m3, then the gas consumption at a capacity of 350 tons / day for 1 hour will be equal to:

7). We calculate the actual gas velocity in the furnace under operating conditions:

This value corresponds to the one specified in the calculation condition (the discrepancy is allowed up to 10%).

• eight). We determine the number and size of blowing devices. To do this, we take the number of blast fungi per 1m2 of the grate = 30, then the total number of fungi will be equal to:
• nine). The air flow rate on the grate in the prechamber is taken equal to 20% of the total amount of air, then the air flow rate per one fungus will be equal to:

ten). We calculate the cross-sectional area of ​​​​the central channel of the fungus:

To do this, we take the air speed in it 12 m / s

The diameter of the fungus channel will be equal to:

Under the cap of the fungus, eight holes are drilled on the central rod (no = 8). The air speed in them is assumed to be 10 m/s (Wom = 10 m/s).

Then the diameter of one hole will be equal to:

The grate in the forechamber is made of pipes. Holes are drilled in the pipes through which air enters. We accept the diameter of one hole = 10mm, and the air speed in them is 10m/s. Then the total area of ​​the holes will be equal to:

eleven). Calculate the number of holes:

We accept nf = 1847 pcs.

12). We calculate the cross-sectional area of ​​the flue for the removal of roasting gas from the furnace. We accept the gas velocity Wg = 10m/s.

Most sulfuric acid plants use sulfur as a feedstock. Sulfur is a by-product of natural gas processing and some other industrial gases (generator, refinery lawn). Such gases always contain some amount of sulfur compounds. Combustion of crude natural gas from sulfur will lead to environmental pollution with sulfur oxides. Therefore, sulfur compounds are usually first removed in the form of hydrogen sulfide, which is then partially burned to SO2, after which the mixture of hydrogen sulfide and sulfur dioxide interacts on a layer of bauxite at 270-300 ºC, turning as a result of this interaction into S and H2O. The sulfur obtained in this way is called "gas". In addition to "gas", native sulfur can be used as a raw material.

Sulfur as a raw material for the production of sulfuric acid has a number of advantages. First, unlike sulfur pyrites, it contains almost no impurities that could be catalytic poisons at the stage of contact oxidation of sulfur dioxide, for example, arsenic compounds. Secondly, when it is burned, no solid and other wastes are generated that would require storage or search for methods for their further processing (when pyrites are fired, almost the same amount of solid waste is formed per 1 ton of initial pyrite - cinder). Thirdly, sulfur is much cheaper to transport than pyrites, since it is a concentrated raw material.

Let us consider a "short" scheme for obtaining sulfuric acid from sulfur by the DCDA method (Fig. 2).

Rice. 2.

1 -- furnace for burning sulfur; 2 - waste heat boiler; 3 - economizer 4 - starting furnace: 5. 6 - starting furnace heat exchangers. 7 - contact device: 8 - heat exchangers 9 - drying tower. 10, 11 - the first and second monohydrate absorbers. 12 - acid collectors: 13 - exhaust pipe.

Molten sulfur is passed through mesh filters to remove possible mechanical impurities (sulfur melts at a temperature slightly above 100 °C, so this method of purification is the simplest) and sent to furnace 1, into which air, previously dried with production sulfuric acid, is supplied as an oxidizing agent in the drying tower 9. The roasting gas leaving the furnace is cooled in the waste heat boiler 2 from 1100-1200 ºС to 440-450 ºС and sent with this temperature, equal to the ignition temperature of industrial catalysts based on vanadium pentoxide, to the first layer of the shelf-contact apparatus 7 .

The temperature regime necessary to bring the working line of the process closer to the line of optimal temperatures is controlled by passing flows of partially reacted roasting gas through heat exchangers 8, where it is cooled by heated gas flows after absorption (or dried air). After the third stage of contacting, the roasting gas is cooled in heat exchangers 8 and sent to an intermediate monohydrate absorber 10, sprayed with sulfuric acid circulating through the acid collector 12 with a concentration close to 98.3%. After the removal of sulfur trioxide in the absorber 10 and the resulting deviation from the almost reached equilibrium, the gas is again heated to the ignition temperature in the heat exchangers 8 and sent to the fourth contact stage.

In this scheme, in order to cool the gas after the fourth stage and additionally mix the equilibrium, a part of the dried air is added to it. The gases that have reacted in the contact apparatus are passed for cooling through the economizer 3 and sent to the final 11 monohydrate absorber 11, from which gases that do not contain sulfur oxides are emitted through the exhaust pipe 13 into the atmosphere.

To start the installation (bring it to a given technological, in particular temperature, mode), a starting furnace 4 and starting furnace heat exchangers 5 and 6 are provided. These devices are turned off after the installation is put into operation.

1. Introduction

2. General characteristics of the sulfuric acid plant

3. Raw sources of sulfuric acid production

4. Brief description of industrial methods for producing sulfuric acid

5.Catalyst selection

6. Justification of the production method

7. Stages and chemistry of the process

8. Thermodynamic analysis

9. Kinetics of the SO 2 oxidation process

10. Condensation of sulfuric acid

11. Thermodynamic analysis of the condensation process

12. Description of the technological scheme of the process

13. Calculation of the material balance

14. Calculation of heat balance

15. Calculation of the contact device

16. Safety measures during the operation of the production facility

17. References

1. Introduction

Sulfuric acid is one of the main large-tonnage products of the chemical industry. It is used in various sectors of the national economy, since it has a set of special properties that facilitate its technological use. Sulfuric acid does not smoke, has no color and odor, is in a liquid state at ordinary temperatures, and in concentrated form does not corrode ferrous metals. At the same time, sulfuric acid is one of the strong mineral acids, forms numerous stable salts and is cheap.

In technology, sulfuric acid is understood as systems consisting of sulfur oxide (VI) and water of various compositions: p SO 3 t H 2 O.

Sulfuric acid monohydrate is a colorless oily liquid with a crystallization temperature of 10.37 o C, a boiling point of 296.2 o C and a density of 1.85 t/m 3 . It mixes with water and sulfur oxide (VI) in all respects, forming hydrates of the composition H 2 SO 4 H 2 O, H 2 SO 4 2H 2 O, H 2 SO 4 4H 2 O and compounds with sulfur oxide H 2 SO 4 SO 3 and H 2 SO 4 2SO 3.

These hydrates and sulfur oxide compounds have different crystallization temperatures and form a range of eutectics. Some of these eutectics have crystallization temperatures below or close to zero. These features of sulfuric acid solutions are taken into account when choosing its commercial grades, which, according to the conditions of production and storage, must have a low crystallization temperature.

The boiling point of sulfuric acid also depends on its concentration, that is, the composition of the "sulfur oxide (VI) - water" system. With an increase in the concentration of aqueous sulfuric acid, its boiling point increases and reaches a maximum of 336.5 ° C at a concentration of 98.3%, which corresponds to the azeotropic composition, and then decreases. The boiling point of oleum with an increase in the content of free sulfur oxide (VI) decreases from 296.2 o C (boiling point of monohydrate) to 44.7 o C, corresponding to the boiling point of 100% sulfur oxide (VI).

When sulfuric acid vapor is heated above 400 ° C, it undergoes thermal dissociation according to the scheme:

400 o C 700 o C

2 H 2 SO 4<=>2H 2 O + 2SO 3<=>2H 2 O + 2SO 2 + O 2.

Among mineral acids, sulfuric acid ranks first in terms of production and consumption. Its world production has more than tripled over the past 25 years and currently stands at more than 160 million tons per year.

The fields of application of sulfuric acid and oleum are very diverse. A significant part of it is used in the production of mineral fertilizers (from 30 to 60%), as well as in the production of dyes (from 2 to 16%), chemical fibers (from 5 to 15%) and metallurgy (from 2 to 3%). It is used for various technological purposes in the textile, food and other industries.

2. General characteristics of the sulfuric acid plant

The unit is designed to produce technical sulfuric acid from hydrogen sulfide-containing gas. Hydrogen sulfide gas comes from hydrotreating units, gas desulphurization unit, amine regeneration unit and acid waste stripping.

Commissioning of the plant - 1999

The sulfuric acid production unit is designed to process 24 thousand tons of hydrogen sulfide-containing gas per year.

The design capacity of the plant for sulfuric acid is 65 thousand tons per year.

The design of the installation was carried out by JSC "VNIPIneft" on the basis of the technology of the Danish company "Haldor Topsoe AS" and JSC "NIUIF", Moscow.

The Russian part of the unit is represented by the raw material preparation section, waste heat boilers KU-A, V, S for burning hydrogen sulfide-containing gas, blocks for deaeration of desalted water, neutralization of sulfuric acid discharges and providing the unit with instrumentation air.

The Danish side provided the WSA block consisting of:

contact apparatus (converter);

a condenser

· system of circulation and pumping out of sulfuric acid;

· a system of blowers for supplying air for H 2 S combustion, cooling and diluting the process gas;

· a system for supplying silicone oil (acid vapor control unit) to the process gas in order to reduce SOx emissions into the atmosphere.

3. Raw sources of sulfuric acid production

The raw material in the production of sulfuric acid can be elemental sulfur and various sulfur-containing compounds, from which sulfur or directly sulfur oxide (IV) can be obtained.

Natural deposits of native sulfur are small, although its clarke is 0.1%. Most often, sulfur is found in nature in the form of metal sulfides and metal sulfates, and is also part of oil, coal, natural and associated gases. Significant amounts of sulfur are contained in the form of sulfur oxide in flue gases and non-ferrous metallurgy gases and in the form of hydrogen sulfide released during the purification of combustible gases.

Thus, the raw materials for the production of sulfuric acid are quite diverse, although until now, elemental sulfur and iron pyrites are mainly used as raw materials. The limited use of such raw materials as flue gases from thermal power plants and gases from copper smelting is explained by the low concentration of sulfur oxide (IV) in them.

At the same time, the share of pyrites in the balance of raw materials decreases, and the share of sulfur increases.

In the general scheme of sulfuric acid production, the first two stages are essential - the preparation of raw materials and their combustion or roasting. Their content and instrumentation significantly depend on the nature of the raw material, which to a large extent determines the complexity of the technological production of sulfuric acid.

4. Brief description of industrial processes for the production of sulfuric acid

The production of sulfuric acid from sulfur-containing raw materials involves several chemical processes in which the oxidation state of raw materials and intermediate products changes. This can be represented as the following diagram:

where I is the stage of production of furnace gas (sulfur oxide (IV)),

II - the stage of catalytic oxidation of sulfur oxide (IV) to sulfur oxide (VI) and its absorption (processing into sulfuric acid).

In real production, these chemical processes are supplemented by the processes of preparing raw materials, cleaning furnace gas, and other mechanical and physicochemical operations.

In general, the production of sulfuric acid can be expressed as:

Raw materials Preparation of raw materials Burning (roasting) of raw materials

flue gas cleaning contact absorption

contacted gas SULFURIC ACID

The specific technological scheme of production depends on the type of raw material, the characteristics of the catalytic oxidation of sulfur oxide (IV), the presence or absence of the stage of absorption of sulfur oxide (VI).

Depending on how the process of oxidation of SO 2 to SO 3 is carried out, there are two main methods for producing sulfuric acid.

In the contact method for obtaining sulfuric acid, the process of oxidation of SO 2 to SO 3 is carried out on solid catalysts.

Sulfur trioxide is converted into sulfuric acid at the last stage of the process - the absorption of sulfur trioxide, which can be simplified by the reaction equation:

SO 3 + H 2 O H 2 SO 4

When carrying out the process according to the nitrous (tower) method, nitrogen oxides are used as an oxygen carrier.

The oxidation of sulfur dioxide is carried out in the liquid phase and the end product is sulfuric acid:

SO 3 + N 2 O 3 + H 2 O H 2 SO 4 + 2NO

At present, the industry mainly uses the contact method for obtaining sulfuric acid, which makes it possible to use apparatuses with greater intensity.

1) The chemical scheme for obtaining sulfuric acid from pyrites includes three successive stages:

Oxidation of iron disulfide of pyrite concentrate with atmospheric oxygen:

4FeS 2 + 11O 2 \u003d 2Fe 2 S 3 + 8SO 2,

Catalytic oxidation of sulfur oxide (IV) with an excess of furnace gas oxygen:

2SO 2 + O 2 2SO 3

Absorption of sulfur oxide (VI) with the formation of sulfuric acid:

SO 3 + H 2 O H 2 SO 4

In terms of technological design, the production of sulfuric acid from iron pyrites is the most complex and consists of several successive stages.

2) The technological process for the production of sulfuric acid from elemental sulfur by the contact method differs from the production process from pyrite by a number of features. These include:

- a special design of furnaces for the production of furnace gas;

– increased content of sulfur oxide (IV) in furnace gas;

– no stage of pre-treatment of furnace gas.

The subsequent operations of contacting sulfur oxide (IV) in terms of physical and chemical principles and instrumentation do not differ from those for the process based on pyrites and are usually executed according to the DKDA scheme. Temperature control of the gas in the contact apparatus in this method is usually carried out by introducing cold air between the catalyst layers.

3) There is also a method for the production of sulfuric acid from hydrogen sulfide, called "wet" catalysis, which consists in the fact that a mixture of sulfur oxide (IV) and water vapor, obtained by burning hydrogen sulfide in an air stream, is supplied without separation to contacting, where sulfur oxide ( IV) is oxidized on a solid vanadium catalyst to sulfur oxide (VI). The gas mixture is then cooled in a condenser, where the vapors of the resulting sulfuric acid are converted into a liquid product.

Thus, in contrast to the methods of production of sulfuric acid from pyrites and sulfur, in the process of wet catalysis there is no special stage of absorption of sulfur oxide (VI) and the whole process includes only three successive stages:

1. Combustion of hydrogen sulfide:

H 2 S + 1.5O 2 \u003d SO 2 + H 2 O

with the formation of a mixture of sulfur oxide (IV) and water vapor of equimolecular composition (1: 1).

2. Oxidation of sulfur oxide (IV) to sulfur oxide (VI):

SO 2 + 0.5O 2<=>SO 3

while maintaining the equimolecular composition of the mixture of sulfur oxide (IV) and water vapor (1: 1).

3. Vapor condensation and formation of sulfuric acid:

SO 3 + H 2 O<=>H 2 SO 4

thus, the process of wet catalysis is described by the overall equation:

H 2 S + 2O 2 \u003d H 2 SO 4

There is a scheme for producing sulfuric acid at elevated pressure. The influence of pressure on the rate of the process can be estimated in the kinetic region, where there is practically no influence of physical factors. An increase in pressure affects both the rate of the process and the state of equilibrium. The reaction rate and product yield increase with increasing pressure by increasing the effective concentrations of SO 2 and O 2 and increasing the driving force of the process. But with increasing pressure, the production costs for compressing inert nitrogen also increase. The temperature in the contact device also increases, because. at high pressure and low temperature, the value of the equilibrium constant is small compared to the scheme under atmospheric pressure.

The large scale of production of sulfuric acid poses a particularly acute problem of its improvement. The following main areas can be distinguished here:

1. Expansion of the raw material base through the use of waste gases from boiler houses of combined heat and power plants and various industries.

2. Increasing the unit capacity of installations. An increase in power by two or three times reduces the cost of production by 25 - 30%.

3. Intensification of the burning process of raw materials by using oxygen or air enriched with oxygen. This reduces the volume of gas passing through the apparatus and improves its performance.

4. Increasing the pressure in the process, which contributes to an increase in the intensity of the main equipment.

5. Application of new catalysts with increased activity and low ignition temperature.

6. Increasing the concentration of sulfur oxide (IV) in the furnace gas supplied to the contact.

7. The introduction of fluidized bed reactors at the stages of burning raw materials and contacting.

8. Use of the thermal effects of chemical reactions at all stages of production, including for the generation of power steam.

The most important task in the production of sulfuric acid is to increase the degree of conversion of SO 2 to SO 3. In addition to increasing the productivity of sulfuric acid, the fulfillment of this task also makes it possible to solve environmental problems - to reduce emissions of the harmful component SO 2 into the environment.

To solve this problem, many different studies have been carried out in various fields: SO 2 absorption, adsorption, studies in changing the design of the contact apparatus.

There are various designs of contact devices:

Single Contact Apparatus: This apparatus is characterized by a low degree of conversion of sulfur dioxide to trioxide. The disadvantage of this apparatus is that the gas leaving the contact apparatus has a high content of sulfur dioxide, which has a negative impact from an environmental point of view. Using this apparatus, the exhaust gases must be purified from SO 2 . There are many different ways to dispose of SO 2: absorption, adsorption,…. This, of course, reduces the amount of SO 2 emissions into the atmosphere, but this, in turn, increases the number of devices in the process, the high content of SO 2 in the gas after the contact device shows a low degree of SO 2 utilization, therefore these devices in the production of sulfuric acid do not are used.

Contact device with double contact: DK allows to achieve the same minimum content of SO 2 in the exhaust gases as after chemical cleaning. The method is based on the well-known Le Chatelier principle, according to which the removal of one of the components of the reaction mixture shifts the equilibrium towards the formation of this component. The essence of the method lies in carrying out the process of sulfur dioxide oxidation with the release of sulfur trioxide in an additional absorber. The DC method makes it possible to process concentrated gases.

Contact device with intermediate cooling. The essence of the method lies in the fact that the gas entering the contact apparatus, having passed through the catalyst layer, enters the heat exchanger, where the gas is cooled, then enters the next catalyst layer. This method also increases the utilization of SO 2 and its content in the exhaust gases.

5 . Catalyst selection

The most active catalyst is platinum, but it has fallen into disuse due to high cost and easy poisoning by impurities in the roasting gas, especially arsenic. Iron oxide is cheap, but with the usual gas composition - 7% SO2 and 11% O2, it exhibits catalytic activity only at temperatures above 625 ° C, i.e. when xp 70%, and therefore used only for the initial oxidation of SO2 until reaching xp 50-60%. The vanadium catalyst is less active than the platinum one, but it is cheaper and is poisoned by arsenic compounds several thousand times less than platinum; it turned out to be the most rational and it is the only one used in the production of sulfuric acid. Vanadium contact mass contains on average 7% V2O5; activators are oxides of alkali metals, the K2O activator is usually used; the carrier is porous aluminosilicates. Currently, the catalyst is used in the form of a compound of SiO2, K and/or Cs, V in various proportions. Such a compound turned out to be the most resistant to acid and the most stable. All over the world its more correct name is "vanadium-containing". Such a catalyst is designed specifically to operate at low temperatures, which results in lower emissions into the atmosphere. In addition, such catalysis is cheaper than potassium / vanadium. Conventional vanadium contact masses are porous granules, tablets or rings.

6. Justification of the production method

The production of sulfuric acid from hydrogen sulfide (wet catalysis) at the Perm refinery is a small-scale production (65 thousand tons per year). Basically, this production was created in order to reduce emissions of sulfur-containing gases and maximize the processing of raw materials, which in this case is a waste from the oil hydrotreatment process.

In addition to the use of hydrogen sulfide, 3 reactions occur in the process of obtaining sulfuric acid:

H 2 S + 1.5O 2 \u003d SO 2 + H 2 O

SO 2 + 0.5O 2<=>SO 3

SO 3 + H 2 O<=>H 2 SO 4

These three reactions proceed with the release of a significant amount of heat, which is used for various needs of the sulfuric acid plant and for various purposes of the enterprise: obtaining steam, which is used in this production, obtaining high-pressure steam, which is used by other installations, and heating the air entering the boilers for burning hydrogen sulfide and into the contact apparatus.

The advantage of obtaining sulfuric acid from hydrogen sulfide is that this process makes maximum use of both hydrogen sulfide and sulfur dioxide, which greatly reduces emissions into the atmosphere, the 3-reaction process uses low temperatures and atmospheric pressure, which significantly reduces energy cost compared to a circuit that applies high pressure. Taking into account the fact that a large amount of heat is released as a result of the technological process, the process, due to this, proceeds autothermally.

7. Stages and chemistry of the process

The process of obtaining sulfuric acid by the method of "wet" catalysis consists of the following main stages.

1. Obtaining sulfur dioxide (SO 2) by burning hydrogen sulfide-containing gas according to the following reaction:

2H 2 S+ 3O 2 = 2SO 2 + 2 H 2 O

2. Cooling of flue gases and utilization of the reaction heat of hydrogen sulfide combustion in the waste heat boiler to produce steam.

3. Oxidation of sulfurous anhydride to sulfuric anhydride (SO 3) on a vanadium catalyst in a contact apparatus (converter) R-104 according to the following reaction:

2SO 2 + O 3 \u003d 2 SO 3

4. Obtaining sulfuric acid (H 2 SO 4) by condensation in a WSA U-109 condenser according to the reaction:

SO 3 + H 2 O \u003d H 2 SO 4

5. To obtain improved sulfuric acid (the content of nitrogen oxides N 2 O 3 is less than 0.5 ppm), a scheme is provided for supplying hydrazine hydrate to the sulfuric acid stream entering the sulfuric acid concentration section.

Hydrazine sulfate, obtained by adding hydrazine to sulfuric acid, interacts with nitrosyl sulphurous acid, which determines the content of N 2 O 3 in the product acid:

4NOSO 3 H+ N 2 H 4 H 2 SO 4 3N2 + 5H 2 SO 4

Excess hydrazine is oxidized to form elemental nitrogen:

N 2 H 4 H 2 SO 4 + O 2 N2 + 2H 2 O + H 2 SO 4

The chemical composition of sulfuric acid is expressed by the formula H 2 SO 4 . The structural formula of sulfuric acid is as follows:

The relative molecular weight of sulfuric acid is 98.08 kg/kmol.

Anhydrous sulfuric acid contains 100% H 2 SO 4 or 81.63% SO 3 and 18.37% wt. H 2 O. It is a colorless, odorless oily liquid with a crystallization temperature of 10.37 ºС. The boiling point of anhydrous sulfuric acid at a pressure of 1.01 10 5 Pa (760 mm Hg) is 298.2 ºС. Density at 20 ºС is 1830.5 kg/m 3 .

Sulfuric acid is miscible with water and sulfur dioxide in any proportion.

In the production of sulfuric acid, a vanadium catalyst is used to oxidize sulfur dioxide to sulfur dioxide. It is a porous substance coated with an active complex compound containing vanadium pentoxide V 2 O 5 .

In this case, a VK-WSA catalyst from Haldor Topsoe is used.

The ignition temperature of the catalyst is 400-430 ºС. At temperatures above 620 ºС, the activity of the catalyst decreases rapidly, because in this case, the active complex containing vanadium pentoxide (V 2 O 5) decomposes, and the support structure is also destroyed, which leads to the destruction of the catalyst and the formation of dust.

The service life of the catalyst is at least 4 years.

8. Thermodynamic analysis

Calculation of the thermal effect of the oxidation reaction SO 2 in SO 3 :

2SO 2 + O 2 \u003d 2 SO 3

Q=-ΔН=196.6 kJ

The reaction is exothermic - it proceeds with the release of heat.

ΔG=ΔH-TΔS=-196.6-298*17.66=-5459.28

SO 3 :

SO 3 + H 2 O \u003d H 2 SO 4

Q=-ΔH=174.26 kJ

The Gibbs energy is much less than zero. This means that the reaction is thermodynamically possible.

Table 1

Conclusion: the oxidation reaction of SO 2 proceeds most fully at low temperatures. It follows from this that it is expedient to carry out the SO 2 oxidation reaction at low temperatures. An increase in pressure, according to the principle of Le Chatelier, has a positive effect.

9. Kinetics of the process of sulfur dioxide oxidation

Reaction rate constant: determined from the Arrhenius equation.

K \u003d K 0 * e (-Ea / RT) \u003d 9.3 *10 5 *e (-79000 / 430 * 8.31) \u003d 0.13

Ea - activation energy (79000 J / mol)

R is the gas constant (8.31)

E- temperature

K 0 - pre-exponential multiplier (9.3 * 10 5 sec)

Calculation of the equilibrium degree of conversion

Table 3

Equilibrium conversion values ​​at different temperatures

Based on the data obtained in tables 3 and 4, the following conclusion can be drawn: from the point of view of the equilibrium degree of conversion, the process of sulfur dioxide oxidation must be carried out at a low content of SO 2 in the gas mixture and at low temperatures.

Calculation of the contact time of the gas mixture in the contact apparatus

Table 5

Gas contact time on the first catalyst layer

τ = ∑Δτ =3.188 sec

The total contact time on the first layer of the catalyst τ = 3.188 sec.

Table 5

Gas contact time on the second catalyst bed

τ = ∑Δτ = 6.38 sec

Temperature increase calculation

T k \u003d Tn + λΔx \u003d 787.26 K

T n, T k - initial and final temperatures, K

λ is the coefficient of gas temperature increase when the degree of conversion changes by 1% under adiabatic conditions

Δx - increase in the degree of conversion

10. Condensation of sulfuric acid

Condensation with a pair of sulfuric acid. In some cases, the gas used to produce sulfuric acid does not contain harmful impurities (arsenic, fluorine). Then it is economically expedient not to subject such gas to washing in special equipment, but to transfer it immediately for contacting. Usually it is also not subjected to drying, so this process is called wet catalysis (for example, obtaining sulfuric acid from hydrogen sulfide). The gas entering the sulfuric acid production stage contains SO 3 and H 2 0, and the formation of sulfuric acid does not occur as a result of the absorption of sulfuric anhydride by acid solutions, but due to the formation of H2SO4 vapor and their condensation in a tower with a nozzle or other equipment designed for this process.

The condensation process is more intense (goes at a high speed) than the absorption process. In addition, condensation proceeds at a high temperature, which facilitates the removal and use of heat.

With slow cooling of a gas containing SO3 and H 2 O, it is possible to carry out the process of condensation of sulfuric acid vapors without the formation of fog. However, the rate of the process is low, and it is often more economical to cool at a higher rate, allowing some mist to form, and then separating this mist from the gas mixture. To make the mist easier to settle in the filters, the process is carried out under conditions in which large droplets are formed. This corresponds to a low supersaturation that occurs and a higher temperature of the reflux acid than in a conventional absorption process ("hot" absorption).

Acid condensation takes place inside glass tubes into which process gas containing acid vapor enters. Inside the glass tubes are spirals that serve as centers for the precipitation of sulfuric acid. At the end of each tube there is a cartridge filter (drip eliminator) designed to trap the sulfuric acid mist. The outer surface of the pipes (annulus) is cooled by atmospheric air. Purified gas with a residual concentration of sulfuric acid less than 20 ppm and a temperature not exceeding 120 degrees Celsius is discharged into the chimney.

About 35% (wt.) of sulfuric acid condenses in volume, while the vapors turn into liquid droplets, turn into fog and are carried away by the gas flow.

The steam pressure in the waste heat boiler is maintained high enough to keep the temperature of the heat exchange surfaces. boiler was above the dew point of sulfuric acid (275 °C).

Uncondensed gas from the condenser tower through a lined gas duct through a hydraulic seal enters wet electrostatic precipitators. The latter are designed to capture sulfuric acid mist from gases with a concentration of 93-94% (mass.). The hydraulic seal can also serve as a mist trap. The purified gas is released into the atmosphere. For the initial heating of the catalyst in the contact apparatus, a starting heater is used, in which the air is heated by burning fuel gas.

The use of a condenser tower in the production of sulfuric acid makes it possible to reduce the number of stages: instead of 4 stages, the process proceeds in 3.

Stage 1 is the combustion of hydrogen sulfide in waste heat boilers;

Stage 2 is the oxidation of sulfur dioxide in the contact apparatus

Stage 3 is the condensation of sulfuric acid vapors in the condenser.

This device avoids the absorption process, which, in turn, reduces the number of devices

11. Thermodynamic analysis of the condensation process

Calculation of the thermal effect of the condensation reaction SO 3 :

SO 3 + H 2 O \u003d H 2 SO 4

Q=-ΔH=174.26 kJ

The reaction is exothermic - proceeds with the release of heat.

ΔG=ΔH-TΔS=-174.26-298*-288.07=-86019.12

The Gibbs energy is much less than zero. This means that the reaction is thermodynamically possible.

H 2 O g \u003d H 2 O f

Table 3

Values ​​of thermodynamic quantities

Under standard conditions, the water condensation reaction is thermodynamically possible.

The condensation reaction of sulfuric acid is thermodynamically possible.

Calculation of the equilibrium constant

D G =- R * T * lnKp

lgKp =- D G /2.3*8.31*T

Kp =10 - D G /19.113*T

Table 5

Values ​​of equilibrium constants depending on temperature

T, 0 C	T,K	DG	Kp
100	373	-84989,9	5,8*10 -4
200	473	-61056,9	0,528
300	573	-49090,4	45,43
400	673	-37123,9	1,043*10 3

Table 5 shows that with an increase in the temperature of the condensation reaction, the equilibrium constant Kp decreases.

Therefore, it is expedient to carry out the condensation process at elevated temperatures.

12. Description of the technological scheme of the process

Raw material enters the plant in two streams:

Hydrogen sulfide gas from L-24-6, L-24-7, L-24-9, HFC units under pressure from 0.35 to 0.6 kg/cm 2 ;

Sour gas from the amine regeneration unit of the RAiOKS unit (titer 520) at a pressure of 0.6 kg/cm 2 .

At the inlet of the installation, the flows are combined and sent to the separator to separate the liquid phase from it. A mixer for injection of demineralized water for absorption of ammonia and MEA is installed on the hydrogen sulfide gas pipeline before the separator. The consumption of demineralized water is controlled by the FI-211 rotameter.

The liquid phase from the level separator, pos. LISA-320, is pumped by pump R-207A, C to the HFC desulphurization unit or the amine regeneration and acid waste stripping unit.

Hydrogen sulfide pressure on the unit is regulated by a pressure regulator pos. PIC-165, the valve of which is installed on the H 2 S discharge pipeline to the flare.

The consumption of hydrogen sulfide for the installation is recorded by the device pos.FIQ-210, the temperature - by the device pos.TI-039.

The level in the separator is equipped with low and high level alarms pos.LISA-320.

From the separator, hydrogen sulfide is supplied for combustion to waste heat boilers KU-A, V, S through flow regulators pos. FIC-404 (KU-A), FIC-405 (KU-V), FIC-406 (KU-S) with valves - cut-offs USY-401 (KU-A), USY-402 (KU-B), USY-403 (KU-S).

Hydrogen sulfide pressure to waste heat boilers is regulated by devices pos. PISA-401 (KU-A), pos. PICA-402 (KU-V), pos. PICA-403 (KU-S) with alarm and blocking by the minimum pressure in the hydrogen sulfide line at the inlet to the waste heat boiler.

Combustion of hydrogen sulfide in the furnace of waste heat boilers KU-A, V, S to sulfur dioxide (SO 2) occurs in the air flow supplied from the blower K-131.

Ignition, heating and putting into operation of waste heat boilers is carried out using fuel gas.

The total consumption of fuel gas for the installation is recorded by the device pos.FIQ-632, the fuel gas pressure - by the device pos.PI-622, the temperature - pos.TI-603.

Fuel gas from the factory network through the MO-019 electric valve enters the fuel gas separator, where the gas is separated from the condensate.

The level of condensate in the B-211 separator is recorded by the device pos.LISA-999 with low and high level alarms pos.LISA-999 and blocking by the minimum level.

The condensate from V-211 is automatically pumped out by the pump R-211A, B according to the maximum level pos. LISA-999 (the pump stops at the minimum level) into the gas condensate line from the flare facility to AT-6.

After the separator, fuel gas is heated in a steam heater and fed to waste heat boilers KU-A, V, C.

The pressure in the fuel gas line is regulated by the PICA-176 device, the valve of which is installed on the fuel gas line after.

Fuel gas flow to each waste heat boiler is regulated by devices pos. recyclers.

Cut-off valves USY-416 (KU-A), USY-417 (KU-V), USY-418 (KU-S), which are part of the waste heat boiler blocking system, are installed at the fuel gas inlet to each waste heat boiler.

Blocking is provided for the minimum pressure of fuel gas at the gas supply to the injectors of the waste heat boiler - pos. PSA-416 (KU-A), PSA-417 (KU-B), PSA-418 (KU-S).

The scheme provides for the supply of nitrogen to the fuel gas line to purge the system before ignition of the boiler and in preparation for repair.

The waste heat boiler KU-A, B, C consists of a cyclone furnace where H 2 S is burned, a cooling chamber, a steam generation system by utilizing the heat of combustion of gases, which includes: a double-drum (upper and lower) boiler, a convective bundle and superheater.

Cyclone furnace consists of a double metal skin formed by two concentric cylinders of sheet steel. Hot air circulates in the cavity between the skins, which comes from the space between the skins of the boiler.

A hot mixture of hydrogen sulfide and air is supplied tangentially through a nozzle device at the front end of the cyclone. The nozzle device is an air channel passing through the boiler lining at an angle of 40 º to the horizontal axis.

Hydrogen sulfide enters the air channel through holes in the upper wall of the channel with a pressure greater than the air pressure, and mixes with it.

Ignition of the mixture occurs at the cut of the channel, combustion occurs inside the cyclone during the rotational movement of the gas flow.

To eliminate incomplete combustion of hydrogen sulfide, a small amount of secondary air is supplied to the pinch area of ​​the cyclone furnace.

Ignition of hydrogen sulfide is carried out with the help of fuel gas entering the furnace through the ignition device.

Cooling chamber formed by the left and right side screens and the rear wall. It has three diaphragm-type explosive safety valves.

Superheater serpentine type is located behind the convective beam.

The upper drum with an intra-drum device is designed to separate the steam-water mixture into saturated steam and boiler water, feed the lower drum with water and remove saturated steam.

The lower drum is designed to supply water to all lifting pipes of the boiler.

The casing of the boiler is double. Combustion air passes between the inner and outer skins. The air pressure between the cladding sheets in all modes of the boiler is higher than the gas pressure in the boiler, which ensures the gas density of the boiler.

The lining of the front wall, the ceiling of the boiler block and the lining of the cyclone furnace are made of refractory concrete.

The air flow into the furnace of the waste heat boiler KU-A, B, C is regulated by the devices pos. FIC-422, respectively, the valves of which are installed on the air supply to the waste heat boiler. The air flow control is included in the cascade control scheme for the combustion of hydrogen sulfide and maintains the air-hydrogen sulfide ratio in the range (10-12):1.

The air pressure at the inlet to the waste heat boiler KU-A, V, C is recorded by the device pos. PISA-420, PISA-421, PISA-422, respectively. An alarm and blocking is provided for the minimum pressure at the inlet to each waste heat boiler.

There is a blocking "flame presence control" pos.BSA-401 (KU-A), pos.BSA-402 (KU-B), pos.BSA-403 (KU-S), when triggered, the waste heat boiler stops.

Ignition of the waste-heat boiler KU-A,V,S on fuel gas and warming up before switching to hydrogen sulfide combustion is carried out with the removal of flue gases into the atmosphere through a candle at the outlet of the process gas from the boiler to the gate MO-22 (KU-A), MO-23 (KU-V), MO-24 (KU-S).

The temperature of the process gas at the outlet of KU-A, B, C is controlled by the device pos. TICSA-407,408,409 by changing the air flow rate for the combustion of hydrogen sulfide, maintaining the specified air / gas ratio. If the air/gas ratio is not maintained and the temperature goes beyond the specified temperature range, then there is a decrease (with an increase in temperature) and an increase (with a decrease in temperature) of the flow of hydrogen sulfide into the waste heat boiler.

The input of feed water coming from the pumps R-201A, B, C is carried out into the upper drum of the boiler using a distribution pipe on a submerged perforated sheet.

The level of feed water in the upper drum of the waste heat boiler is regulated by devices pos. waste heat boiler.

Feed water consumption in waste heat boilers KU-A, B, C is recorded by devices pos. FI-214,215,216 installed on the feed water supply line to waste heat boilers, respectively.

Feed water pressure at the inlet to waste heat boilers is recorded by devices pos.PI-115,116,117; temperature - with devices pos.TI-016,019,026 installed at the feed water inlet to the boiler.

The pressure in the drum of the waste heat boiler is recorded by the device pos. PIA-155 (KU-A), PIA-157 (KU-V), PIA-159 (KU-C) with low and high pressure alarms.

The water level in the upper drum of the boiler is equipped with low and high alarms; blocking on the minimum and maximum water level poz.LSA-306, LSA-307 (KU-A); LSA-310, LSA-311 (KU-V); LSA-314, LSA-315 (KU-S).

Water from the upper drum of the boiler descends into the lower one through five unheated pipes (four from the clean and one from the salt compartment), at the outlet of which grates are installed to prevent steam from being trapped in the downpipes. Then the boiler water from the lower drum enters the evaporator tubes of the radiant screen and the convection beam. The steam-water mixture from the evaporator tubes enters the baffles of the upper drum, which ensure the separation of steam from water droplets. Saturated steam from the upper part of the drum, passing through the separation device, enters the superheater, where it is heated to a temperature of 354 ºС. The steam from the superheater enters the reducing device ROU-40/15 to reduce the pressure from 34.0-38.5 kgf/cm 2 to 15 kgf/cm 2 .

The pressure in the steam system of waste heat boilers KU-A, V, C is regulated by the device pos. PIKA-160, the regulator valve of which is installed on the steam outlet line in ROU-40/15.

The continuous blowdown water from the salt compartments of the upper drum of the boiler enters the blowdown tanks.

Periodic blowdown water during boiler drainage also enters the barbater expander of periodic blowdowns.

From the tanks, water, having cooled in the heat exchanger, where it heats the feed water of the B-201 deaerator, enters the tank. Water is pumped from the tank to the ELOU installation.

Sampling of boiler water from the continuous blowdown line is carried out through the sampling cooler.

Process gas from the waste heat boiler KU-A, V, S with a temperature of 530-650 ºС with a volume fraction of SO 2 in the range of 7.5-8.5% enters the X-103 mixer, where it mixes with air and superheated steam.

To dilute the process gas, the air escaping after the condenser has cooled and forced by the blower is used. Dilution of the process gas with air is carried out to a volume fraction of SO 2 3.5-4.5%, which is necessary to reduce the dew point of the acid contained in it and to increase the degree of oxidation of SO 2 to SO 3.

Steam is supplied to the process gas from a medium pressure steam system, preheated in an E-163 electric heater to a temperature of 250-300 ºС, and serves to maintain the humidity of the process gas in order to ensure sufficient condensation of sulfuric acid in the WSA E-109 condenser.

The total consumption of process gas before mixing with air and steam is recorded by the device pos.FI-702, the temperature - by the device pos.TIА-1103, the volume fraction of SO 2 - by the automatic gas analyzer AIA-501.

Steam consumption for mixing is regulated by the FIC-701 device, the regulator valve of which is installed on the steam line in the electric heater.

The steam temperature after the electric heater is recorded by the device pos. TICA-1101 and is regulated by the electric heater heating elements control system.

The air consumption for mixing is regulated by the FIC-703 device, the valve of which controls the blades of the intake gate of the blower.

Air and steam flow devices are connected in a cascade circuit for temperature control pos.TICA-1105 of the process gas at the inlet to the contact apparatus (converter) to maintain the temperature within 385-430 ºС.

The process gas from the mixer at a temperature of 400-430 ºС is sent to the contact apparatus (converter), where the catalytic conversion of sulfur dioxide (sulphurous anhydride) into sulfuric anhydride takes place on two layers of the VK-WSA vanadium catalyst with interlayer cooling of the contact gas.

contact device is a cylindrical apparatus made of stainless steel, with two layers of catalyst 820 mm and 1640 mm high, respectively.

On the first catalyst layer, approximately 90-93% of SO 2 is converted into SO 3, while the temperature at the outlet of the 1st layer rises to 500-550 ºС. To remove the heat of reaction, the gas from the 1st layer is cooled in the E-105 reboiler-gas cooler to a temperature of 380–410 ºС, where steam of 62 kgf/cm2 is produced, then it enters the mixer, and from there to the second catalyst layer c. On the second layer, the final transformation of SO 2 into SO 3 takes place, while the outlet temperature rises to 410–430 ºС.

The gas temperature at the outlet of the gas cooler is controlled by the TICA-1107 device, the regulator valve of which controls the gates on the gas bypass of the gas cooler tube bundle.

Blocking is provided for the maximum gas temperature at the inlet to the contact apparatus - pos.TISA-1104; high gas temperature alarm at the exit of the first layer - pos.TIА-1106; low and high temperature alarm at the outlet of the gas cooler - item TICA-1107, low and high temperature alarm at the inlet to E-108 - item TIA-1109.

The gas after the contact apparatus, having been pre-cooled in the riboiler-gas cooler, is sent to the WSA condenser to condense sulfuric acid from the gas.

The temperature of the total flow at the inlet to the condenser is recorded by the device pos.TIА-1111 with low and high temperature alarms. Blocking on the maximum temperature pos.TISA-1110 of gas on an entrance to the condenser is provided.

To reduce SO 3 emissions into the atmosphere along with the exhaust gas, an acid vapor control unit is provided at the outlet of the WSA condenser. The reduction of SO 3 emissions is achieved by introducing silicone oil vapor into the gas stream at the reboiler inlet, which serves as condensation centers for sulfuric acid in the gas and thereby enhances acid condensation in the WSA condenser.

The supply of boiler water to the riboilers-gas coolers is ensured by the natural circulation of water from the drum-steam collector

By utilizing the heat of the gas flow in the reboilers, steam is generated with a pressure of 62 kgf/cm 2 , which is discharged from the drum-steam collector to ROU-40/15 through the pressure regulator pos.PICSA-902.

Feed water is supplied by the R-161A, B pump from the deaerator.

The water level is regulated by the device pos.LICA-801, the regulator valve of which is installed on the feed water line from the R-161A, B pump, with high and low level alarms. There is a lock on the minimum level poz.LSA-802 in the drum-steam collector B-162.

To increase the reliability of the steam collector, an additional level gauge pos.LIА-803 was installed.

To maintain the chemical composition of the boiler water (reduce salinity), the system provides for automatic purging from the lowest points through the valves:

· HIC-753 type "НЗ" - В-162;

· HV-791 - E-105;

· HV-792, HV-793, HV-794, HV-795 - E-108.

Blowdown water from V-162, E-105, E-108 enters the B-206A blowdown tank, from where, together with the blowdown water of waste heat boilers KU-A, V, C, it is discharged through the E-202 heat exchanger into the B-203 tank and the pump Р-203А,В is pumped out to the CDU unit.

The gas in E-109 is supplied by two streams.

The temperature of the surface of the gas inlet pipelines is recorded by devices pos.TIА-1112, TIA-1113 installed at the inlet of each flow in E-109, the decrease in readings of which determines the level of sulfuric acid in E-109 and possible clogging of the apparatus pipes.

The WSA E-109 condenser is a vertical apparatus consisting of 5 modules, each of which contains 720 glass tubes, 6.8 m long and 40 mm in diameter. Inside the glass tubes are metal spirals that serve as centers for the precipitation of sulfuric acid. At the end of each tube there is a cartridge filter (drip eliminator) designed to trap the sulfuric acid mist. The acid collector is located at the bottom of the WSA condenser. The E-109 body is lined with acid-resistant bricks and tiles.

In the E-109 condenser, the gas rises up inside the glass tubes, on the inner surfaces of which sulfuric acid condenses due to cooling by air coming from the K-130A, B blower between the tubes.

Purified gas with a residual mass fraction of SO 3 less than 20 ppm and a temperature of not more than 120 ºС is discharged into the chimney.

The mass fraction of SO 3 in the purified gas is measured by the AIA-652 instrument with high SO 3 content alarm.

The temperature of the purified gas is regulated by the device pos. TICA-1115, the valve-regulator of which is installed on the cooling air line to the HOB heater E-133 (venting air in addition to E-109).

Blocking is provided for the maximum gas temperature at the outlet of E-109 pos.TISA-1116.

The difference between the gas inlet and outlet of the condenser E-109 is measured by the instrument pos.PDI-903.

The air for cooling the WSA E-109 condenser is taken from the atmosphere through the air filter A-133A, B by the blower K-130A, B and fed into the annulus E-109 counterflow to the purified gas.

After the E-109 condenser, the cooling air is divided into flows:

· one stream goes to the intake of the blower K-131, which supplies air for dilution of the process gas after KU-A, B, C;

· the second flow - blower K-132 is fed into the furnace of waste heat boilers KU-A, V, C for hydrogen sulfide combustion;

· a part of the flow is discharged to the intake of the blower K-130A, B to maintain the air temperature at the blower discharge within 20–35 ºС;

· Excess air is discharged to the spark plug through the HOV E-133 heater, which utilizes the heat of the cooling air.

The air temperature at the E-109 inlet is controlled by the device pos.TIC-1117, a pneumatically actuated damper is installed on the hot air supply line to the intake of the K-130A, B blower.

The air temperature after the filter A-133A, B is measured by the device pos.TIA-1123.

An alarm is provided for low air pressure at the intake of blowers K-130A, B - pos. PIA-911,912, respectively.

To prevent leakage of process gas into the cooling air, a differential pressure between the cooling air and process gas system is maintained within 10–41 mm w.c. device pos.PDICSA-904, which controls the intake gates of blowers K-130A, B. Low pressure alarm and low differential pressure lockout between the cooling air and condenser process gas system E-109 is provided.

The condensed sulfuric acid from the WSA E-109 condenser flows down the apparatus and is directed to the acid tank B-120.

To reduce the temperature of the acid coming from E-109 from 270 to 65 ºС, a cold flow of circulating acid from pump Р-121А,В is added to the hot acid stream.

The acid from the tank V-120 is pumped by the pump R-121A, B through the plate acid cooler E-122, where it is cooled by circulating water. and sent to:

the main part - as a recirculation for mixing with hot acid from E-109,

· the balance amount of sulfuric acid pumps R-123A, B is pumped out of the plant.

The temperature of sulfuric acid at the intake of pumps R-121A, B is recorded by the device pos.TIA-1119 with a high temperature alarm. Blocking on the maximum temperature pos.TISA-1120 of the sulfuric acid arriving on reception of the pumps R-121A, B is provided.

The level of acid in the tank B-120 is regulated by devices pos.LICA-804, LISA-805 , the valve is installed on the acid pumping line by R-123A, B pumps from the unit to the sulfuric acid concentration section tit.75-11 and to the chemical water treatment unit tit.517 PGPN. There are two pipelines for pumping sulfuric acid to Park 75-11, one of which is in reserve.

Low and high level alarm is provided - pos.LICA-804 and blocking by minimum and maximum levels - pos.LISA-805 of V-120 tank.

A low pressure alarm and a minimum pressure blocking are provided - pos.PICSА-906 in the sulfuric acid recirculation line.

The mass fraction of circulating acid in the range of 93–98% is controlled by the analyzer pos. AICA-653 and is maintained by automatic water supply from the B-150 tank to the acid circulation line using the USV 1207 shut-off valve.

The water level in the B-150 tank is maintained by the LIA-803 device, the regulator valve of which is installed on the water line to the B-150 tank. Low and high level alarm pos.LIА-803 in B-150 tank is provided.

The consumption of sulfuric acid from the plant is recorded by the device pos.FIQ-635.

The pressure in the sulfuric acid pumping line is recorded by the PISA-907 device. In the event of a pressure drop in the line of less than 0.2 kgf / cm 2, the standby pump R-123A, B is switched on according to the device pos. PICSА-906 .In PbiS it is written that the BCA block is stopping.

To reduce the content of nitrogen oxides (N 2 O 3) in commercial sulfuric acid (less than 0.5 ppm), a 64% aqueous solution of hydrazine hydrate is supplied by a dosing pump R-124 from a tank V-160 to the pipeline for supplying sulfuric acid to the site concentration tit.75-11. A ready-made 64% aqueous solution of hydrazine hydrate is supplied to the plant in a container with a volume of 200 liters, from which it is pumped into the V-160 tank by a pneumatically driven pump.

To collect accidental acid spills, the plant is provided with a buried reinforced concrete tank V-209, in which sulfuric acid is neutralized with a 15% NaOH solution to a pH value in the range of 7.0–8.0 according to the AA-505 analyzer.

The alkaline solution during neutralization in V-209 is supplied by gravity from the alkali tank V-208, into which alkali is periodically pumped from the reagent facilities.

Before the alkali is supplied to E-209, the R-209 pump is turned on for circulation through the tank, and sulfuric acid is neutralized by slowly supplying alkali to the B-209 tank.

The neutralization of sulfuric acid in B-209 with soda ash is provided. According to the analyzer readings and when checking with a litmus test pH = 7, the neutralized solution is pumped out by the R-209 pump to the PLC in agreement with the UVKiOSV.

13. Calculation of the material balance

2H 2 S + 3O 2 \u003d 2SO 2 + 2 H 2 O

Gas capacity 1749.8 m 3 /h degree of conversion of H 2 S = 99.9

Coming						Consumption
Mr	kg	% mass	m3	% about	kmol	Mr	kg	% mass	m3	% about	kmol
58,00	45,31	0,23	17,50	0,12	0,78	SO2	64,00	4944,48	25,64	1730,57	12,53	77,26
34,00	2629,39	13,63	1732,30	11,82	77,33	H2O	18,00	1460,94	7,57	1818,06	13,16	81,16
32,00	3870,85	20,07	2709,59	18,49	120,96	N2	28,00	12741,53	66,06	10193,23	73,79	455,05
28,00	12741,53	66,06	10193,23	69,57	455,05	H2S	34,00	2,63	0,01	1,73	0,01	0,08
-	19287,07	100,00	14652,62	100,00	654,13	CO2	44,00	137,48	0,71	69,99	0,51	3,12
∑	-	19287,07	100,00	13813,58	100,00	616,68

SO 2 + 0.5O 2<=>SO 3

Degree of conversion SO 2 = 98.5

Coming						Consumption
Mr	kg	% mass	m3	% about	kmol	Mr	kg	% mass	m3	% about	kmol
64,00	4944,48	46,03	1730,57	27,70	77,26	SO3	80,00	6087,90	56,67	1704,61	31,60	76,10
32,00	1217,58	11,33	852,31	13,64	38,05	SO2	64,00	74,17	0,69	25,96	0,48	1,16
28,00	4580,42	42,64	3664,33	58,66	163,59	N2	28,00	4580,42	42,64	3664,33	67,92	163,59
-	10742,48	100,00	6247,21	100,00	278,89	∑	-	10742,48	100,00	5394,90	100,00	240,84

SO 3 + H 2 O \u003d H 2 SO 4

SO 3 conversion = 99.5%

Coming						Consumption
Mr	kg	% mass	m3	% about	kmol	Mr	kg	% mass	m3	% about	kmol
SO3	80,00	6087,90	80,90	1704,61	49,75	76,10	H2SO4	98,00	7420,39	98,61	1696,09	98,06	75,72
H2O	18,00	1362,93	18,11	1696,09	49,50	75,72	SO3	90,00	30,44	0,40	7,58	0,44	0,34
SO2	64,00	74,17	0,99	25,96	0,76	1,16	SO2	64,00	74,17	0,99	25,96	1,50	1,16
∑	7524,99	100,00	3426,66	100,00	152,98	∑	7524,99	100,00	1729,62	100,00	77,22

14. Calculation of heat balance

Standard enthalpy of formation ΔH (298 K, kJ/mol)	Standard molar heat capacity Cp (298 K, J/mol K)	Specific heat C (kJ/kg K)
			SO2	-296,90	39,90	0,62
O2	0,00	29,35	0,92
N2	0,00	29,10	1,04
SO3	-439,00	180,00	2,25
H2O	-241,82	33,58	1,87
H2SO4	-814,20	138,90	1,42
C4H10	-124,70	97,78	1,69
CO2	-393,51	37,11

Heat balance of the sulfur dioxide oxidation reaction

SO 2 +1/2 O 2 = SO 3

Heat balance of the sulfuric acid condensation reaction

SO 3 + H 2 O = H 2 SO 4

From the calculations of the heat balance of the reactions of sulfur dioxide oxidation and condensation of sulfuric acid, it can be seen that during these reactions a significant amount of heat is released, which must be removed, which is done in a real technological process to increase the degree of conversion of these reactions, and the heat is utilized for various purposes as process and enterprise.

15. Calculation of the contact device

Calculation of the contact time (given in the kinetics of the oxidation of sulfur dioxide)

τ 1 \u003d ∑Δτ \u003d 3.188 sec

τ 2 \u003d ∑Δτ \u003d 6.38 sec

The total time of contacting the gas in the contact apparatus is

τ = 3.188 + 6.38 = 9.568

m 2

Calculation of the diameter of the contact device

Contact device diameter is 8 m

16. Safety measures during the operation of the production facility

Safety requirements when starting and stopping technological systems and certain types of equipment, putting them into reserve, being in reserve and when putting them into operation from reserve

The main safety requirement when starting and stopping technological equipment is strict adherence to the procedure for starting and stopping the installation, set out in section 6 of this regulation.

Start-up or decommissioning of technological systems is carried out on the basis of a written order of the chief engineer of the PPGN, which indicates the person responsible for the safe conduct of work and the procedure for organizing start-up or decommissioning of the technological system.

Start-up or decommissioning of individual equipment is carried out by order of the head of the installation.

The equipment is considered to be standby when it is in good condition, fully equipped with control and measuring instruments, signaling devices and ESD, tested in working conditions, there is a conclusion from the mechanic of the installation or workshop about its readiness for operation.

In winter, all backup equipment must be warmed up.

The equipment being in reserve should be subjected to daily visual inspection, and the dynamic equipment – ​​to inspection and running-in with the established frequency, but at least once a month. For centrifugal pumps, the shaft must be rotated by hand every shift.

Before putting into operation, the technological system must be purged with nitrogen with the control of the residual oxygen content no more than 0.5% vol. The output of the technological system to the normal technological mode is carried out in accordance with Section 6 of this Regulation.

Before each start-up of standby pumps, check their serviceability and the position of shut-off valves at the suction and discharge of the pump.

Repair of a hot pump allocated to the reserve should be started only after its casing temperature does not exceed 45 ºС.

The R-104 contact device is blown off sulfuric acid vapors with hot air through the WSA E-109 condenser and further into the chimney. To carry out work inside the R-104 during shutdown, the catalyst and the contact apparatus are cooled by air from the K-132 blower according to the process gas scheme. If the catalyst is not unloaded from the apparatus, the R-104 is pressurized with air supplied to the apparatus through the hose jumper to prevent contact of the catalyst with atmospheric air.

Requirements for ensuring the explosion safety of the technological process: the accepted boundaries of technological blocks, the values ​​of energy indicators and the explosion hazard categories of blocks, the boundaries of possible damage during explosions, the provided safety and emergency protection measures

In order to increase safety and limit the mass of products that can leak into the environment as a result of accidents, the plant is provided with: high-speed shut-off valves on the lines in front of the pumps, a 100% reserve for pumps, self-starting systems for pumps and ATS; piping of heat exchangers has bypasses and shut-off valves.

The unit is equipped with a distributed process control system (DCS) and an emergency protection system (ESD). Light and sound alarms are triggered at the maximum permissible values ​​of technological parameters.

There is one explosive technological block at the plant - the separation block.

The assessment of the explosion hazard of the technological block was carried out in accordance with the requirements of the General Rules for the Explosivity of Chemical, Petrochemical and Oil Refining Industries "(PB 09-540-03). At the same time, the technological blocks include the apparatus necessary for the implementation of the main technological process. The pipelines between the apparatuses are included in the blocks block, as well as fittings and instrumentation.

The safety measures taken in the course of the technological process with the performance of routine operations must meet the requirements of the regulatory and technical documentation that determines the procedure and conditions for the safe conduct of the production process, the actions of personnel in emergency situations and the implementation of repair work. The list of specified technical documentation must be approved by the Chief Engineer of PPGN.

In order to ensure the safety of the process, the following measures were taken:

All equipment and pipelines outdoors, having a wall temperature of more than 60 ºС, and in rooms of more than 45 ºС, are thermally insulated;

All equipment and pipelines for protection against static electricity are grounded. The installation has lightning protection;

All moving parts of mechanisms are protected;

The B-120 tank is equipped with upper and lower level alarms.

The mandatory scope of periodic monitoring of the state and operation parameters of the installation by bypassing personnel, as well as its maintenance includes:

· control of temperatures and pressures in apparatuses by instruments installed on site;

Checking centrifugal pumps for the absence of vibration and extraneous noise (for serviceability);

· check of tightness of flange connections, omental seals of stop valves and face seals of centrifugal pumps;

· visual control over the absence of vibration of technological pipelines, especially at the discharge of pumps;

Checking the availability and serviceability of standard instrumentation;

visual control over the presence and good condition of the guards of the moving parts of mechanisms, service platforms;

Visual control of the proper condition of ventilation systems;

visual control of the serviceable condition of the lifting equipment;

Checking sampling devices for product leakage.

In winter, the following additional operations must be performed:

· control over the functioning of low-pressure steam heating of apparatuses, technological pipelines, instrumentation and control devices;

· control over the functioning of heating with heating water of instrumentation and control equipment, air heaters for supply ventilation and technological pipelines;

control over the cooling systems of centrifugal pumps, ensuring a constant flow of water;

control of the patency of drains and drainage lines;

Control over the operation of condensate drains.

It is forbidden to remove interlocks in automatic process control systems.

In the event of emergencies caused by deviations of the plant operation parameters from the requirements of the technological regime standards set forth in Section 4 of this regulation, act in accordance with the "Emergency Localization Plan" (PLAS).

All types of repair work must be carried out in accordance with the annual and monthly "Schedules for scheduled preventive maintenance". Repair work must be carried out in accordance with the requirements of the instructions approved by the Chief Engineer of the Company:

Instruction on the procedure for safe repair work in OOO LUKOIL-PNOS (IB-025-003-2005);

Instruction on the procedure for the safe conduct of hot work at the facilities of OOO LUKOIL-PNOS (PB-0001-1-2005);

Instruction on the procedure for the safe conduct of gas-hazardous work at the facilities of OOO LUKOIL-PNOS (B-025-002-2005);

Instructions on the procedure for safe earthworks on the territory of OOO LUKOIL-PNOS (IB-255-004-2005).

Sampling of hydrogen sulfide and drainage of separators and containers should be carried out in a gas mask standing with your back to the wind with an understudy in a gas mask.

Safety measures in the conduct of the technological process, the performance of routine operations

The safe operation of the unit depends on the qualifications of the operating personnel, compliance with safety regulations, fire and gas safety, rules for the technical operation of equipment and communications, and compliance with the norms of technological regulations.

Persons who have reached the age of 18, who have been instructed in industrial safety and labor protection, theoretical and practical training in safe methods and methods of work, and who have passed the exam for admission to independent work, who do not have medical contraindications, are allowed to work.

All the necessary regulatory and technical documentation that determines the procedure and conditions for the safe conduct of the production process, the actions of personnel in emergency situations and the implementation of repair work, according to the list approved by the chief engineer of the PPGN, must be available at the facility, its knowledge and observance by the personnel is mandatory.

You can only work on working equipment. Constantly monitor the operation of control and automation devices, alarm systems and interlocks. Strictly adhere to all parameters of the technological mode.

In order to avoid gas contamination in industrial premises, excess air overpressure is created in the operator, pumping, transformer substation, switchboards with an air exchange rate of 5.

The pumps are equipped with mechanical seals.

All pressurized devices are equipped with safety valves. Combustible gases are discharged from safety valves into the flare line; the valve on the flare line must be open during the operation of the unit.

The lighting of the installation is made in accordance with the current regulations, the lighting fittings are explosion-proof.

Measures to ensure fire safety during the technological process

The fire safety of the installation is achieved by a system for preventing the formation of a combustible environment, preventing the formation of ignition sources in a combustible environment, maximum automation of the technological process, the use of fire extinguishing equipment and fire alarms, the use of basic building structures with regulated fire resistance limits and fire distribution limits, compliance with instructions and fire safety rules when operation of buildings, structures and equipment.

The territory of the production facility, as well as production facilities and equipment, must be kept clean and tidy at all times.

Smoking on the installation forbidden. Smoking is allowed in a specially designated area (in agreement with the fire brigade), equipped with a bin for cigarette butts and a fire extinguisher.

The tightness of the equipment, especially flange connections and stuffing boxes, requires strict control by the operating personnel. If a pass is detected, it is necessary to immediately supply water vapor to the pass and take measures to disable the emergency section or apparatus from operation.

In winter conditions, it is allowed to warm up frozen equipment, pipelines, valves only with steam or hot water. The use of open fire is prohibited.

In the event of a fire in the production premises, the possibility of safe evacuation of people is provided.

In the event of a fire or an accident at the facility, personnel not involved in the elimination of a fire or an emergency situation are evacuated from the territory of the facility.

The location of equipment and buildings provides for the observance of appropriate fire breaks.

The unit is equipped with the following fire extinguishers:

5 fixed fire monitors protecting the equipment at the outdoor installation;

Fire-fighting water is supplied to fire monitors from the company's fire-fighting water supply network;

Steam risers are provided for local extinguishing of the source of fire in the industrial premises and at the outdoor installation;

The unit is provided with rubber hoses for supplying steam or nitrogen to places of possible fire;

Air-foam and powder fire extinguishers, boxes with sand, felt, asbestos cloth are provided at the installation in the established places;

Protection of premises by automatic fire alarm;

Manual call points for fire alarms are provided, located outside the building and along the perimeter of the installation;

The placement of structures, equipment, apparatus, evacuation routes and exits are carried out taking into account the norms and rules of fire safety and ensure the evacuation of people from buildings and premises before the maximum allowable values ​​of dangerous fire factors.

Safe Methods for Handling Pyrophoric Deposits

Apparatus and pipelines after the withdrawal of equipment from operation and their release from products should be steamed with water vapor.

After the apparatus is freed from condensate, the lower fitting or hatch must be opened and an air sample taken to analyze the content of dangerous concentrations of product vapors in it (should be no more than 20% of the lower concentration limit of flame propagation NKRP).

When cleaning the apparatus, it is necessary to moisten the deposits on the walls of the apparatus. When cleaning the apparatus, spark-proof tools are used. A work permit is issued for the performance of these works in accordance with the established procedure.

Pyrophoric deposits removed from equipment must be kept moist until destroyed. Remove pyrophoric deposits for storage in the UVKiOSV sludge accumulator.

Methods for neutralizing production products in case of spills and accidents

In the event of a spill of sulfuric acid in the pump room, immediately arrange a dike of sand to prevent further spreading of the product. Before cleaning up spilled product, neutralize with soda or lime.

Removal of sulfuric acid during the release of filters, repair of acid pumps R-121A, B, R-123A, B or sampling takes place in a buried container and is neutralized with a 10% alkali solution.

When neutralizing spilled sulfuric acid, work in overalls and use a gas mask.

A safe method for removing production products from technological systems and certain types of equipment

When the installation is stopped for repairs, hydrogen sulfide gas is sent to the flare.

The contact apparatus (converter) R-104 is initially blown with flue gases from sulfuric acid vapor through the WSA E-109 condenser, then with hot air in a normal manner into the chimney.

Sulfuric acid is pumped to the goods park 75-11. The acid residues are drained into a buried tank B-209 and neutralized with a 10% alkali solution, or filled with soda ash (up to pH = 7), then pumped out to the PLC, in agreement with the UVKiOSV.

The main potential hazards of the equipment and pipelines used, their critical components and measures to prevent emergency depressurization of technological systems

The main potential hazards of the process equipment and pipelines used, their critical units at the plant are:

· Hydrogen sulfide-containing gas processed at the plant is explosive, flammable and toxic;

· hydrogen sulfide in the presence of water vapor is a strong corrosive substance that affects the metal, resulting in depressurization of process equipment;

· the presence of excess pressure (up to 15 kgf/cm 2 - medium pressure steam) and high temperatures in apparatuses and pipelines creates a threat of their rupture;

· in case of violation of the operating modes of the equipment or in cases of its mechanical or corrosive wear, depressurization is possible with the occurrence of explosive and toxic concentrations of gases, which can lead to explosions and / or fires, as well as poisoning of personnel;

electric shock in case of failure of the grounding of current-carrying parts of the equipment or breakdown of electrical insulation;

· the possibility of falling service personnel when servicing apparatus and pipelines located at a height of more than one meter, in the absence of a fence or its malfunction;

· the possibility of obtaining a thermal burn in case of contact of unprotected parts of the body with heated surfaces of apparatus and pipelines with broken insulation;

The presence of rotating mechanisms creates a risk of injury from them;

· the possibility of depressurization or destruction of devices and pipelines under the influence of external force factors.

Measures to prevent emergency depressurization of technological systems are:

· heat treatment of the main technological equipment and welded sections of pipelines in media that cause corrosion cracking;

· Ensuring compliance of pipeline equipment, shut-off valves, safety devices, protective automation systems, alarm systems with the requirements of current NTD;

assessment of the technical condition of devices, equipment, pipelines and other elements of the installation;

operation of only serviceable equipment and timely implementation of scheduled preventive maintenance;

Timely inspection of equipment;

Ensuring high-quality repair and cleaning of devices, pipelines;

· conducting the technological process without violating the norms of this technological regulation, excluding the output of the parameters of the apparatus and equipment for critical values.

17. List of used literature

1. Technological regulations of the sulfuric acid plant

2. B.T.Vasiliev, M.I.Otvagina; Sulfuric acid technology. Moscow: Chemistry 1985. 386 pages

3. A.M. Kutepov; General chemical technology. Moscow: Higher School, 1990. 520 pp.

4. Amelin A.G. Sulfuric acid production. Moscow 1983

“There is hardly any other, artificially produced substance, so often used in technology, as sulfuric acid.

Where there are no factories for its extraction, the profitable production of many other substances of great technical importance is unthinkable”

DI. Mendeleev

Sulfuric acid is used in a variety of chemical industries:

• mineral fertilizers, plastics, dyes, artificial fibers, mineral acids, detergents;
• in the oil and petrochemical industry:

for oil refining, obtaining paraffins;

• in non-ferrous metallurgy:

for the production of non-ferrous metals - zinc, copper, nickel, etc.

• in ferrous metallurgy:

for pickling metals;

• in the pulp and paper, food and light industries (for the production of starch, molasses, fabric bleaching), etc.

Sulfuric acid production

Sulfuric acid is produced in industry in two ways: contact and nitrous.

Contact method for the production of sulfuric acid

Sulfuric acid is produced by the contact method in large quantities at sulfuric acid plants.

Currently, the main method for the production of sulfuric acid is contact, because. this method has advantages over others:

Obtaining a product in the form of a pure concentrated acid acceptable to all consumers;

- reduction of emissions of harmful substances into the atmosphere with exhaust gases

I. Raw materials used for the production of sulfuric acid.

Main raw material

sulfur - S

sulfur pyrite (pyrite) - FeS 2

non-ferrous metal sulfides - Cu2S, ZnS, PbS

hydrogen sulfide - H 2 S

Auxiliary material

Catalyst - vanadium oxide - V 2 O 5

II. Preparation of raw materials.

Let's analyze the production of sulfuric acid from pyrite FeS 2.

1) Grinding of pyrite. Before use, large pieces of pyrite are crushed in crushers. You know that when a substance is crushed, the reaction rate increases, because. the surface area of ​​contact of the reactants increases.

2) Purification of pyrite. After crushing pyrite, it is purified from impurities (waste rock and earth) by flotation. To do this, crushed pyrite is lowered into huge vats of water, mixed, the waste rock floats up, then the waste rock is removed.

III. Basic chemical processes:

4 FeS 2 + 11 O 2 t = 800°C→ 2 Fe 2 O 3 + 8 SO 2 + Q or burning sulfur S+O2 t ° C→ SO2

2SO2 + O2 400-500° With,V2O5 , p↔ 2SO 3 + Q

SO 3 + H 2 O → H 2 SO 4 + Q

IV . Technological principles:

The principle of continuity;

The principle of integrated use of raw materials,use of waste from other production;

The principle of non-waste production;

The principle of heat transfer;

Counterflow principle (“fluidized bed”);

The principle of automation and mechanization of production processes.

V . Technological processes:

Continuity principle: roasting pyrite in a kiln → supply of sulfur oxide ( IV ) and oxygen into the purification system → into the contact apparatus → supply of sulfur oxide ( VI ) into the absorption tower.

VI . Environmental protection:

1) tightness of pipelines and equipment

2) gas cleaning filters

VII. Chemistry of production :

FIRST STAGE - roasting pyrite in a furnace for roasting in a "fluidized bed".

Sulfuric acid is mainly used flotation pyrites- production waste during the enrichment of copper ores containing mixtures of sulfur compounds of copper and iron. The process of enrichment of these ores takes place at the Norilsk and Talnakh enrichment plants, which are the main suppliers of raw materials. This raw material is more profitable, because. sulfur pyrite is mined mainly in the Urals, and, naturally, its delivery can be very expensive. Possible use sulfur, which is also formed during the enrichment of non-ferrous metal ores mined in mines. Sulfur is also supplied by the Pacific Fleet and the NOF. (concentrating factories).

First stage reaction equation

4FeS2 + 11O2 t = 800°C → 2Fe 2 O 3 + 8SO 2 + Q

Crushed, cleaned, wet (after flotation) pyrite is poured from above into a furnace for firing in a "fluidized bed". From below (counterflow principle) air enriched with oxygen is passed through for a more complete firing of pyrite. The temperature in the kiln reaches 800°C. Pyrite is heated to red and is in a "suspended state" due to the air blown from below. It all looks like a boiling red hot liquid. Even the smallest particles of pyrite do not cake in the “fluidized bed”. Therefore, the firing process is very fast. If earlier it took 5-6 hours to burn pyrite, now it takes only a few seconds. Moreover, in the "fluidized bed" it is possible to maintain a temperature of 800°C.

Due to the heat released as a result of the reaction, the temperature in the furnace is maintained. Excess heat is removed: pipes with water run along the perimeter of the furnace, which is heated. Hot water is used further for central heating of adjacent premises.

The resulting iron oxide Fe 2 O 3 (cinder) is not used in the production of sulfuric acid. But it is collected and sent to a metallurgical plant, where iron metal and its alloys with carbon are obtained from iron oxide - steel (2% carbon C in the alloy) and cast iron (4% carbon C in the alloy).

Thus, principle of chemical production- non-waste production.

Coming out of the oven furnace gas , the composition of which: SO 2, O 2, water vapor (pyrite was wet!) And the smallest particles of cinder (iron oxide). Such furnace gas must be cleaned from impurities of solid particles of cinder and water vapor.

Purification of furnace gas from solid particles of cinder is carried out in two stages - in a cyclone (centrifugal force is used, solid particles of cinder hit the walls of the cyclone and fall down). To remove small particles, the mixture is sent to electrostatic precipitators, where it is cleaned under the action of a high voltage current of ~ 60,000 V (electrostatic attraction is used, cinder particles stick to the electrified plates of the electrostatic precipitator, with sufficient accumulation under their own weight, they fall down), to remove water vapor in the furnace gas (drying furnace gas) use concentrated sulfuric acid, which is a very good desiccant because it absorbs water.

Drying of furnace gas is carried out in a drying tower - furnace gas rises from bottom to top, and concentrated sulfuric acid flows from top to bottom. To increase the contact surface of gas and liquid, the tower is filled with ceramic rings.

At the outlet of the drying tower, the kiln gas no longer contains any cinder particles or water vapor. Furnace gas is now a mixture of sulfur oxide SO 2 and oxygen O 2 .

SECOND STAGE - catalytic oxidation of SO 2 to SO 3 with oxygen in a contact device.

The reaction equation for this stage is:

2SO2 + O2 400-500°С, V 2 O 5 ,p ↔ 2 SO 3 + Q

The complexity of the second stage lies in the fact that the process of oxidation of one oxide into another is reversible. Therefore, it is necessary to choose the optimal conditions for the flow of the direct reaction (obtaining SO 3).

It follows from the equation that the reaction is reversible, which means that at this stage it is necessary to maintain such conditions that the equilibrium shifts towards the exit SO 3 otherwise the whole process will be broken. Because the reaction proceeds with a decrease in volume (3 V↔2V ), an increased pressure is required. Increase the pressure to 7-12 atmospheres. The reaction is exothermic, therefore, taking into account the Le Chatelier principle, this process cannot be carried out at a high temperature, because. the balance will shift to the left. The reaction starts at a temperature = 420 degrees, but due to the multi-layer catalyst (5 layers), we can increase it to 550 degrees, which greatly speeds up the process. The catalyst used is vanadium (V 2 O 5). It is cheap and lasts a long time (5-6 years). the most resistant to the action of toxic impurities. In addition, it contributes to the shift of balance to the right.

The mixture (SO 2 and O 2) is heated in a heat exchanger and moves through pipes, between which a cold mixture passes in the opposite direction, which must be heated. As a result, there heat exchange: the starting materials are heated, and the reaction products are cooled to the desired temperatures.

THIRD STAGE - absorption of SO 3 by sulfuric acid in the absorption tower.

Why sulfur oxide SO 3 do not absorb water? After all, it would be possible to dissolve sulfur oxide in water: SO 3 + H 2 O → H 2 SO 4 . But the fact is that if water is used to absorb sulfur oxide, sulfuric acid is formed in the form of a mist consisting of tiny droplets of sulfuric acid (sulfur oxide dissolves in water with the release of a large amount of heat, sulfuric acid is so hot that it boils and turns into steam ). In order to avoid the formation of sulfuric acid mist, use 98% concentrated sulfuric acid. Two percent water is so small that heating the liquid will be weak and harmless. Sulfur oxide dissolves very well in such an acid, forming oleum: H 2 SO 4 nSO 3 .

The reaction equation for this process is:

NSO 3 + H 2 SO 4 → H 2 SO 4 nSO 3

The resulting oleum is poured into metal tanks and sent to the warehouse. Then tanks are filled with oleum, trains are formed and sent to the consumer.

1. Introduction

2. General characteristics of the sulfuric acid plant

3. Raw sources of sulfuric acid production

4. Brief description of industrial methods for producing sulfuric acid

5.Catalyst selection

6. Justification of the production method

7. Stages and chemistry of the process

8. Thermodynamic analysis

9. Kinetics of the SO 2 oxidation process

10. Condensation of sulfuric acid

11. Thermodynamic analysis of the condensation process

12. Description of the technological scheme of the process

13. Calculation of the material balance

14. Calculation of heat balance

15. Calculation of the contact device

16. Safety measures during the operation of the production facility

17. References

1. Introduction

Sulfuric acid is one of the main large-tonnage products of the chemical industry. It is used in various sectors of the national economy, since it has a set of special properties that facilitate its technological use. Sulfuric acid does not smoke, has no color and odor, is in a liquid state at ordinary temperatures, and in concentrated form does not corrode ferrous metals. At the same time, sulfuric acid is one of the strong mineral acids, forms numerous stable salts and is cheap.

In technology, sulfuric acid is understood as systems consisting of sulfur oxide (VI) and water of various compositions: p SO 3 t H 2 O.

Sulfuric acid monohydrate is a colorless oily liquid with a crystallization temperature of 10.37 o C, a boiling point of 296.2 o C and a density of 1.85 t/m 3 . It mixes with water and sulfur oxide (VI) in all respects, forming hydrates of the composition H 2 SO 4 H 2 O, H 2 SO 4 2H 2 O, H 2 SO 4 4H 2 O and compounds with sulfur oxide H 2 SO 4 SO 3 and H 2 SO 4 2SO 3.

These hydrates and sulfur oxide compounds have different crystallization temperatures and form a range of eutectics. Some of these eutectics have crystallization temperatures below or close to zero. These features of sulfuric acid solutions are taken into account when choosing its commercial grades, which, according to the conditions of production and storage, must have a low crystallization temperature.

The boiling point of sulfuric acid also depends on its concentration, that is, the composition of the "sulfur oxide (VI) - water" system. With an increase in the concentration of aqueous sulfuric acid, its boiling point increases and reaches a maximum of 336.5 ° C at a concentration of 98.3%, which corresponds to the azeotropic composition, and then decreases. The boiling point of oleum with an increase in the content of free sulfur oxide (VI) decreases from 296.2 o C (boiling point of monohydrate) to 44.7 o C, corresponding to the boiling point of 100% sulfur oxide (VI).

When sulfuric acid vapor is heated above 400 ° C, it undergoes thermal dissociation according to the scheme:

400 o C 700 o C

2 H 2 SO 4<=>2H 2 O + 2SO 3<=>2H 2 O + 2SO 2 + O 2.

Among mineral acids, sulfuric acid ranks first in terms of production and consumption. Its world production has more than tripled over the past 25 years and currently stands at more than 160 million tons per year.

The fields of application of sulfuric acid and oleum are very diverse. A significant part of it is used in the production of mineral fertilizers (from 30 to 60%), as well as in the production of dyes (from 2 to 16%), chemical fibers (from 5 to 15%) and metallurgy (from 2 to 3%). It is used for various technological purposes in the textile, food and other industries.

2. General characteristics of the sulfuric acid plant

The unit is designed to produce technical sulfuric acid from hydrogen sulfide-containing gas. Hydrogen sulfide gas comes from hydrotreating units, gas desulphurization unit, amine regeneration unit and acid waste stripping.

Commissioning of the plant - 1999

The sulfuric acid production unit is designed to process 24 thousand tons of hydrogen sulfide-containing gas per year.

The design capacity of the plant for sulfuric acid is 65 thousand tons per year.

The design of the installation was carried out by JSC "VNIPIneft" on the basis of the technology of the Danish company "Haldor Topsoe AS" and JSC "NIUIF", Moscow.

The Russian part of the unit is represented by the raw material preparation section, waste heat boilers KU-A, V, S for burning hydrogen sulfide-containing gas, blocks for deaeration of desalted water, neutralization of sulfuric acid discharges and providing the unit with instrumentation air.

The Danish side provided the WSA block consisting of:

contact apparatus (converter);

a condenser

· system of circulation and pumping out of sulfuric acid;

· a system of blowers for supplying air for H 2 S combustion, cooling and diluting the process gas;

· a system for supplying silicone oil (acid vapor control unit) to the process gas in order to reduce SOx emissions into the atmosphere.

3. Raw sources of sulfuric acid production

The raw material in the production of sulfuric acid can be elemental sulfur and various sulfur-containing compounds, from which sulfur or directly sulfur oxide (IV) can be obtained.

Natural deposits of native sulfur are small, although its clarke is 0.1%. Most often, sulfur is found in nature in the form of metal sulfides and metal sulfates, and is also part of oil, coal, natural and associated gases. Significant amounts of sulfur are contained in the form of sulfur oxide in flue gases and non-ferrous metallurgy gases and in the form of hydrogen sulfide released during the purification of combustible gases.

Thus, the raw materials for the production of sulfuric acid are quite diverse, although until now, elemental sulfur and iron pyrites are mainly used as raw materials. The limited use of such raw materials as flue gases from thermal power plants and gases from copper smelting is explained by the low concentration of sulfur oxide (IV) in them.

At the same time, the share of pyrites in the balance of raw materials decreases, and the share of sulfur increases.

In the general scheme of sulfuric acid production, the first two stages are essential - the preparation of raw materials and their combustion or roasting. Their content and instrumentation significantly depend on the nature of the raw material, which to a large extent determines the complexity of the technological production of sulfuric acid.

4. Brief description of industrial processes for the production of sulfuric acid

The production of sulfuric acid from sulfur-containing raw materials involves several chemical processes in which the oxidation state of raw materials and intermediate products changes. This can be represented as the following diagram:

where I is the stage of production of furnace gas (sulfur oxide (IV)),

II - the stage of catalytic oxidation of sulfur oxide (IV) to sulfur oxide (VI) and its absorption (processing into sulfuric acid).

In real production, these chemical processes are supplemented by the processes of preparing raw materials, cleaning furnace gas, and other mechanical and physicochemical operations.

In general, the production of sulfuric acid can be expressed as:

preparation of raw materials combustion (roasting) of raw materials cleaning of furnace gas contacting absorption

contacted gas

SULFURIC ACID

The specific technological scheme of production depends on the type of raw material, the characteristics of the catalytic oxidation of sulfur oxide (IV), the presence or absence of the stage of absorption of sulfur oxide (VI).

Depending on how the process of oxidation of SO 2 to SO 3 is carried out, there are two main methods for producing sulfuric acid.

In the contact method for obtaining sulfuric acid, the process of oxidation of SO 2 to SO 3 is carried out on solid catalysts.

Sulfur trioxide is converted into sulfuric acid at the last stage of the process - the absorption of sulfur trioxide, which can be simplified by the reaction equation:

SO 3 + H 2 O

H 2 SO 4

When carrying out the process according to the nitrous (tower) method, nitrogen oxides are used as an oxygen carrier.

The oxidation of sulfur dioxide is carried out in the liquid phase and the end product is sulfuric acid:

SO 3 + N 2 O 3 + H 2 O

H 2 SO 4 + 2NO

At present, the industry mainly uses the contact method for obtaining sulfuric acid, which makes it possible to use apparatuses with greater intensity.

1) The chemical scheme for obtaining sulfuric acid from pyrites includes three successive stages:

Oxidation of iron disulfide of pyrite concentrate with atmospheric oxygen:

4FeS 2 + 11O 2 \u003d 2Fe 2 S 3 + 8SO 2,

Catalytic oxidation of sulfur oxide (IV) with an excess of furnace gas oxygen:

2SO 3

Absorption of sulfur oxide (VI) with the formation of sulfuric acid:

SO 3 + H 2 O

H 2 SO 4

In terms of technological design, the production of sulfuric acid from iron pyrites is the most complex and consists of several successive stages.