Sulfur utilization system at NMP. Effective methods of hydrogen sulfide processing at oil refineries (production of sulfuric acid, elemental sulfur, etc.). the latter reacts with nitrogen oxides in the liquid phase

At refineries, sulfur is obtained from technical hydrogen sulfide. At domestic refineries, hydrogen sulfide is mainly isolated using a 15% aqueous solution of monoethanolamine from the corresponding streams from hydrotreatment and hydrocracking units. Hydrogen sulfide regeneration units from saturated solutions of monoethanolamine are mounted at hydrotreatment units for diesel fuel, kerosene or gasoline, hydrocracking or directly at sulfur production units, where monoethanolamine solutions containing hydrogen sulfide are collected from a large group of units. The regenerated monoethanolamine is returned to the hydrotreaters, where it is reused to recover hydrogen sulfide.

At sulfur production units built according to the projects of the Giprogazoochistka Institute, hydrogen sulfide-containing gas is used, in which at least 83.8% (vol.) hydrogen sulfide. The content of hydrocarbon gases in the raw material should be no more than 1.64% (vol.), water vapor (at 40 ° C and 0.05 MPa) no more than 5% (vol.) and carbon dioxide no more than 4.56% (vol. .).

The plants produce high-quality sulfur with its content in accordance with GOST 127-76 of at least 99.98% (mass); other grades contain sulfur not less than 99.0 and 99.85% (wt.). The yield of sulfur from its potential content in hydrogen sulfide is 92–94% (mass). With an increase in the concentration of hydrogen sulfide in the raw material, for example, up to 90% (vol.), the yield of sulfur from the potential increases to 95-96% (mass.).

The main stages of the process of sulfur production from technical hydrogen sulfide: thermal oxidation of hydrogen sulfide with atmospheric oxygen to produce sulfur and sulfur dioxide; interaction of sulfur dioxide with hydrogen sulfide in reactors (converters) loaded with a catalyst.

The thermal oxidation process takes place in the main furnace, mounted in the same unit with the waste heat boiler.

Mixing and heating of hydrogen sulfide and sulfur dioxide is carried out in auxiliary furnaces. Catalytic sulfur production is usually carried out in two stages. Like thermal, catalytic sulfur production is carried out at a slight excess pressure. The technological scheme of the sulfur production unit designed by the Giprogazoochistka Institute is shown in Figure XI 1-4.

Raw material - hydrogen sulfide-containing gas (technical hydrogen sulfide) - is released from entrained monoethanolamine and water in the receiver / and heated to 45-50 ° C in steam heater 2. Then 89% (wt.) Of the total amount of hydrogen sulfide-containing gas is introduced through the guide nozzle into the main furnace 4. Air is supplied to the furnace through the same nozzle by an air blower 5. The consumption of raw materials and the specified volumetric ratio of air: gas, equal to (2-3) : 1, are supported automatically. The temperature at the process gas outlet from the main furnace is measured with a thermocouple or pyrometer. Then the gas is cooled successively inside the first and then the second convective bundle of the waste heat boiler of the main furnace. Condensate (chemically purified water) enters the waste heat boiler from deaerator 3, from the top of which the resulting water vapor is discharged. In the waste heat boiler of the main furnace, steam is generated at a pressure of 0.4–0.5 MPa. This steam is used in the steam tracers of the pipelines of the installation. In the pipelines through which sulfur is transported, as well as in the storage of liquid sulfur, a temperature of 130-150 ° C is maintained. The sulfur condensed in the waste heat boiler flows through the hydraulic valve 7 into the underground storage 20. The process gas enriched with sulfur dioxide from the waste heat boiler is sent to the mixing stage of the auxiliary furnace I of the catalytic stage I, 11. Into the combustion chamber of the furnace on- i - hydrogen sulfide-containing gas steps (^ 6 wt. % of the total) and air from the blower 5.

The volumetric ratio air:gas, equal to (2 - 3) : 1, is also automatically maintained here. The mixture of combustion products from the mixing chamber of the auxiliary furnace 11 enters from top to bottom into the vertical reactor (converter) of stage I 8. In the reactor, a catalyst, active alumina, is loaded onto a perforated grate. As the catalyst passes, the gas temperature increases, which limits the height of the layer, since with an increase in temperature, the probability of catalyst deactivation increases. The process gas from the reactor 8 is sent to a separate section of the condenser-generator 10. The condensed sulfur flows through the hydraulic seal 9 into the underground sulfur storage 20, and the gas is sent to the mixing chamber of the auxiliary furnace II of the catalytic stage 14. The steam generated in the condenser-generator pressure of 0.5 or 1.2 MPa is used at the plant or is discharged into the factory steam pipeline. Hydrogen sulfide-containing gas (5% by weight of the total) and air from blower 5 (in a volume ratio of 1:2–3) enter the combustion chamber of furnace 14. A mixture of combustion products of hydrogen sulfide-containing and process gases from the mixing chamber of the auxiliary furnace 14 enters the reactor (converter) II stage 16, which is also loaded with active alumina. From the reactor, the gas enters the second section of the condenser-generator 10, where the sulfur condenses and flows into the underground storage 20 through the hydraulic seal 17. -lets. Sulfur flows through the hydraulic seal 18 into the storage 20. The gas is sent to the afterburner 12, where it is heated to 580-600 ° C due to the combustion of fuel gas. Air for fuel combustion and afterburning of hydrogen sulfide residues to sulfur dioxide is injected with fuel gas due to the draft of the chimney 13.

Liquid sulfur from underground storage 20 is pumped out by pump 19 to open warehouse lump sulfur, where it solidifies and is stored before being loaded into railway cars. Sometimes liquid sulfur is passed through a special drum, on which flake sulfur is obtained as a result of rapid cooling, then it is poured into wagons.

Technological mode of the sulfur production unit:

The amount of hydrogen sulfide-containing gas supplied to the installation, m 3 / h Overpressure, MPa Hydrogen sulfide-containing gas supplied to the furnaces air from blowers in furnaces in the deaerator Gas temperature, °C in the main furnace at the outlet of the waste heat boiler at the entrance to the reactors (converters) at the outlet of the 1st stage reactor at the outlet of the second stage reactor gas at the outlet of the condenser-generator in the sulfur trap at the outlet of the afterburner Vacuum in the chimney, Pa oxygen sulfur dioxide hydrogen sulfide

360-760 0,04-0,05 0,05-0,06 0,03-0,05 0,4-0,5 1100-1300 155-165 230-250 290-310 240-260 140-160 390-490 4,5-6 1,45 absence

Sulfur is widely used in national economy- in the production of sulfuric acid, dyes, matches, as a vulcanizing agent in the rubber industry, etc. The use of high purity sulfur predetermines and high quality received products. The presence of hydrocarbons in the hydrogen sulfide-containing gas and their incomplete combustion lead to the formation of carbon, while the quality of sulfur deteriorates, and the yield decreases.

Analysis of the composition of process gases at various stages of sulfur production makes it possible to correct the distribution of hydrogen sulfide-containing gas in the furnaces, the ratio of oxygen and raw materials at the inlet to the furnaces. Thus, an increase in the proportion of sulfur dioxide in the flue gases after the dozhnga above 1.45% (vol.) indicates an increased content of unreacted hydrogen sulfide in the process of obtaining sulfur. In this case, the air flow to the main furnace is corrected, or the hydrogen sulfide-containing gas is redistributed among the furnaces.

The most important condition for the uninterrupted operation of the installation is to maintain the temperature ISO -150°C liquid sulfur in pipelines, equipment, underground storage. During melting, sulfur turns into a mobile yellow liquid, but at 160 ° C it turns brown, and at a temperature of about 190 ° C it turns into a viscous dark brown mass, and only with further heating does the viscosity of sulfur decrease.

The principal technological schemes of Claus plants include, as a rule, three different stages: thermal, catalytic and afterburning. The catalytic stage, in turn, can also be divided into several stages that differ temperature regime. The afterburner stage can be either thermal or catalytic. Each of the similar stages of Claus installations, although they have common technological functions, differ from each other both in the design of the apparatus and in the piping of communications. The main indicator that determines the scheme and mode of Claus plants is the composition of acid gases supplied for processing. The acid gas entering the Claus furnaces must contain as little hydrocarbons as possible. During combustion, hydrocarbons form tars and soot, which, when mixed with elemental sulfur, reduce its quality. In addition, these substances, deposited on the surface of the catalyst, reduce their activity. Aromatic hydrocarbons are particularly detrimental to the efficiency of the Claus process.

The water content in acid gases depends on the mode of condensation of the overhead product of the regenerator of the gas treatment plant. Acid gases, in addition to the equilibrium moisture corresponding to the pressure and temperature in the condensation unit, may also contain methanol vapor and droplet moisture. To prevent dropping liquid from entering the reactors of sulfur production units, acid gases are pre-separated.

The cost of sulfur produced at Claus plants primarily depends on the concentration of H 2 S in the acid gas.

Specific capital investments in the Claus plant increase in proportion to the decrease in the content of H 2 S in the acid gas. The cost of treating an acid gas containing 50% H 2 S is 25% higher than that required for treating a gas containing 90% H 2 S.

The gas, before being fed into the combustion chamber of the thermal stage, passes through the inlet separator C-1, where it is separated from the dropping liquid. To control the concentration of H 2 S in the acid gas, an in-line gas analyzer is installed at the outlet of the C-1 separator.

To ensure the combustion of acid gas, atmospheric air is forced into the combustion chamber using a blower, which first passes through a filter and a heater. Air is heated to eliminate impulsive combustion of acid gas and prevent corrosion of pipelines, since the combustion of H 2 S may form SO 3 , which at low temperatures in the presence of water vapor can form sulfuric acid.

The air flow is regulated depending on the amount of acid gas and the ratio of H 2 S: SO 2 in the gas at the outlet of the waste heat boiler.

The combustion gases of the reaction furnace (HR) pass through the tube bundle of the waste heat boiler, where they are cooled to 500 °C. In this case, a partial condensation of sulfur occurs. The resulting sulfur is discharged from the apparatus through the sulfur gate. Due to the partial removal of heat of reaction by water in the boiler, high-pressure steam is obtained (P = 2.1 MPa).

After the boiler, the reaction gases enter the R-1 catalytic converter-reactor, where carbon disulfide and carbon sulfide undergo hydrolysis.

Due to the exothermic nature of the reactions taking place in the converter, the temperature on the catalyst surface rises by approximately 30-60°C. This prevents the formation of a liquid precipitate of sulfur, which, falling on the surface of the catalyst, would reduce its activity. Such a temperature regime in the converter also simultaneously ensures the decomposition of the products of side reactions - COS and CS 2 .

The main part of the gas (about 90%) from the reactor enters the tube space of the X-1 condenser for cooling, and then goes to the R-2 reactor. Heat removal in the X-1 condenser is carried out due to the evaporation of water in its annulus to obtain low-pressure steam (P=0.4 MPa). When gases are cooled in X-1, sulfur condenses. Liquid sulfur is discharged through the sulfur gate to the degassing unit.

Part of the reaction gases (about 10%), bypassing the X-1 condenser, enters for mixing with colder gases leaving the same condenser. The temperature of the mixture before entering the R-1 reactor is about 225°C.

To control the temperature in the R-1, R-2, R-3 reactors (during the start-up period and in the event of a sulfur fire), low-pressure steam and nitrogen are supplied to them.

During normal operation, the temperature of the gases at the outlet of X-2 and R-1 is 191 and 312°C, respectively.

Removal of heat in the apparatus X-2 is carried out due to the evaporation of water in its annulus to obtain low-pressure steam.

Exhaust gases from the R-2 reactor are fed to the third condenser X-3 for cooling, from where they are fed at a temperature of 130°C for post-treatment.

To control the concentration of H 2 S and SO 2 in the exhaust gases, flow gas analyzers are installed at the outlet of X-3.

To prevent the entrainment of liquid sulfur with exhaust gases, a coalescer is installed on their lines.

To prevent solidification of sulfur in the coagulator, periodic supply of water vapor is provided.

The streams of liquid sulfur discharged from the condensers contain 0.02-0.03% (wt.) hydrogen sulfide. After the degassing of sulfur, the concentration of H 2 S in it decreases to 0.0001%.

Sulfur degassing is carried out in a special block - a sulfur pit. This provides normal conditions warehousing, loading and storage of gas sulfur.

The main amount (~98%) of acid gas is fed into the reactor-generator, which is a gas-tube type steam boiler. Process gas - products of combustion - sequentially passes through the pipe part of the boiler and the condenser-generator, where it is cooled down to 350 and 185°C, respectively.

At the same time, due to the heat released in these devices, water vapor is formed with a pressure of 2.2 and 0.48 MPa, respectively.

The degree of conversion of H2S to sulfur in the reactor-generator is 58-63%. Further conversion of sulfur compounds into elemental sulfur is carried out in catalytic converters.

Table 1.1 - Compositions of the flows of the Claus installation,% (vol.):

Table 1.2 - Duration of residence (f S) of process gas in apparatuses at various flow rates of acid gas G:

In table. 1.1 and 1.2 show the results of a survey of the operation of the installation.

The degree of conversion of H2S to sulfur in the furnace of the reactor-generator is 58-63.8, in the first and second converters 64-74 and 43%, respectively. After the last stage of sulfur condensation process gases enter the afterburner.

At a gas flow rate of 43-61 thousand m3/h, the afterburner provided almost complete oxidation of H 2 S to SO 2 . With a long residence time of gas in the furnace, complete conversion of H 2 S to SO 2 is not ensured: at the outlet of the furnace, the concentration of H 2 S in the gas was 0.018-0.033%.

The main indicators of gas sulfur must meet the requirements of GOST 126-76.

At present, dozens of modified variants of the Claus installation schemes have been developed. The scope of these schemes depends both on the content of hydrogen sulfide in acid gases, and on the presence of various impurities in them, which have a negative impact on the operation of sulfur production units.

For gases with a low sulfur content (from 5 to 20%), four options for improved Claus plants were analyzed.

The first option provides for the supply of oxygen to the combustion chamber (CC) of the furnace instead of air according to the standard scheme. To obtain stable flames, as the H2S content in the feed gas decreases, an acid gas stream is introduced into the combustion chamber, bypassing the burners. The flow jets provide good mixing of the combusted gases with the gas supplied to the system, bypassing the burners. Furnace dimensions and flow rates are chosen to provide sufficient contact time for interaction between the components of both gas streams. After the combustion chamber, the further course of the process is similar to the conventional Claus process.

In the second variant, the feed gas is preheated before being fed to combustion due to the partial heat recovery of the gas flow leaving the combustion chamber. In case of insufficient preheating to obtain the required temperature in the combustion chamber, fuel gas is supplied to it.

The third option involves burning sulfur. Part of the feed gas flow is fed into the combustion chamber, pre-mixed with air. The rest of the acid gas is introduced into the combustion chamber in separate jets through bypass lines. To maintain the required temperature and stabilize the process in the combustion chamber, the resulting liquid sulfur is additionally burned in a special burner mounted in the combustor.

In case of insufficient heat in the system, required amount fuel gas.

In the fourth option, unlike the previous options, the process does not require a combustion chamber: the sour gas is heated in a furnace and then fed into the converter. The sulfur dioxide required for the catalytic conversion is obtained in the sulfur combustion chamber, where air is supplied to ensure the combustion process. Sulfur dioxide from the CS passes through the waste heat boiler, then mixes with heated acid gas and enters the catalytic converter.

Analysis of these tables allows us to draw the following conclusions:

• - the use of a process with preheating of the feed gas is preferable at a high cost of oxygen;
• - the use of the oxygen process is beneficial when the price of oxygen is less than 0.1 grades 1 m 3 .

At the same time, the cost of sulfur is also favorably affected by relatively low concentrations of H2S in acid gas;

• - in terms of the cost of sulfur, the best performance has a catalytic process with the production of sulfur dioxide from sulfur;
• - the most expensive is the process of burning sulfur. This process can be used in the complete absence of hydrocarbons in the feed gas, since the presence of hydrocarbons in the gas causes the formation and deposition of carbon and tar on the catalyst, reducing the quality of sulfur.

Figure 1.4 - Influence of the price of oxygen y on the cost of sulfur CS at different concentrations of H2S in the gas:

Table 1.3 - Average indicators of options for processing sweet gas at the Claus plant:

There is a possibility of improving the Claus process due to two-stage conversion of H 2 S into elemental sulfur: part of the gas is supplied to the reactor according to the usual scheme, and the other part, bypassing the reaction furnace, is fed to the second conversion stage.

According to this scheme, it is possible to process acid gases with a hydrogen sulfide concentration of less than 50% (vol.). The lower the content of H 2 S in the raw material, the greater part of it, bypassing the reaction chamber, is fed into the converter stage.

However, one should not get carried away by bypassing a large volume of gas. The greater the amount of bypassed gas, the higher the temperature in the converter, which leads to an increase in the amount of nitrogen oxides and tri - sulfur oxide in the combustion products. The latter, upon hydrolysis, forms sulfuric acid, which reduces the activity of the catalyst due to its sulfation. The amount of nitrogen oxide and SO3 in gases especially increases at temperatures above 1350°C. VNIIGAZ has also developed a technology for producing polymeric sulfur. Polymeric sulfur differs from conventional sulfur modifications in its high molecular weight. In addition, unlike ordinary sulfur, it does not dissolve in carbon disulfide. The latter property serves as the basis for determining the composition of polymeric sulfur, the quality requirements for which are given in Table 1.4. Polymeric sulfur is mainly used in the tire industry.

Properties, application, raw material base and methods for the production of sulfuric acid. Wet Gas Sulfuric Acid Technology WSA and SNOX Control of Sulfur and Nitrogen Oxide Emissions. Development and optimization of technology. Sulfur production by the Claus method.

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MINISTRY OF EDUCATION OF THE REPUBLIC OF BELARUS

EDUCATIONAL INSTITUTION

"POLOTSK STATE UNIVERSITY"

Department of Chemistry and TPNG

Test

On discipline "Industrial ecology"

Effective Ways hydrogen sulfide processing at refineries (production of sulfuric acid, elemental sulfur, etc.)

Novopolotsk

• 1. Properties of sulfuric acid
• 2. Application of sulfuric acid
• 3. Raw material base for the production of sulfuric acid
• 5.1 Roasting of sulfur-containing raw materials
• 5.2 Gas flushing after firing
• 5.3 Oxidation of sulfur dioxide
• 5.4 Absorption of sulfur trioxide
• 5.5 Double contact and double absorption system (DC/DA)
• 6. WSA and SNOX™ Wet Gas Sulfuric Acid Technology - Sulfur and Nitrogen Oxide Control
• 6.1 Basic research
• 6.2 Development and optimization of technology
• 6.3 SNOX™ Technology
• 7. Sulfur production by the Claus method

sulfuric acid release oxide

1. Properties of sulfuric acid

Anhydrous sulfuric acid (monohydrate) is a heavy oily liquid that mixes with water in all proportions to release a large number heat. The density at 0 ° C is 1.85 g / cm 3. It boils at 296°C and freezes at -10°C. Sulfuric acid is called not only monohydrate, but also its aqueous solutions (), as well as solutions of sulfur trioxide in monohydrate (), called oleum. Oleum "smokes" in air due to desorption from it. Pure sulfuric acid is colorless, while commercial acid is dark in color with impurities.

Physical properties sulfuric acid, such as density, crystallization temperature, boiling point, depend on its composition. On fig. 1 shows a crystallization diagram of the system. The maxima in it correspond to the composition of the compounds or, the presence of minima is explained by the fact that the crystallization temperature of mixtures of two substances is lower than the crystallization temperature of each of them.

Rice. 1 Crystallization temperature of sulfuric acid

Anhydrous 100% sulfuric acid has a relatively high crystallization temperature of 10.7 °C. To reduce the possibility of freezing of a commercial product during transportation and storage, the concentration of technical sulfuric acid is chosen such that it has enough low temperature crystallization. The industry produces three types of commercial sulfuric acid.

Sulfuric acid is very active. It dissolves metal oxides and most pure metals; elevated temperature all other acids from salts. Especially greedily sulfuric acid combines with water due to its ability to give hydrates. It takes away water from other acids, from crystalline salts and even oxygen derivatives of hydrocarbons, which contain not water itself, but hydrogen and oxygen in combination H: O = 2. wood and other plant and animal tissues containing cellulose, starch and sugar are destroyed in concentrated sulfuric acid; water binds with acid and only finely dispersed carbon remains from the tissue. In dilute acid, cellulose and starch break down to form sugars. If it comes into contact with human skin, concentrated sulfuric acid causes burns.

2. Application of sulfuric acid

The high activity of sulfuric acid, combined with the relatively low cost of production, predetermined the enormous scale and extreme variety of its application (Fig. 2). It is difficult to find an industry that has not consumed sulfuric acid or products made from it in various quantities.

Rice. 2 Use of sulfuric acid

The largest consumer of sulfuric acid is the production mineral fertilizers: superphosphate, ammonium sulfate, etc. many acids (for example, phosphoric, acetic, hydrochloric) and salts are produced to a large extent with the help of sulfuric acid. Sulfuric acid is widely used in the production of non-ferrous and rare metals. In the metalworking industry, sulfuric acid or its salts are used to pickle steel products before painting, tinning, nickel plating, chromium plating, etc. Significant amounts of sulfuric acid are used to refine petroleum products. Obtaining a number of dyes (for fabrics), varnishes and paints (for buildings and machines), medicinal substances and some plastics is also associated with the use of sulfuric acid. With the help of sulfuric acid, ethyl and other alcohols, some esters, synthetic detergents, a range of pesticides for pest control Agriculture and weeds. Dilute solutions of sulfuric acid and its salts are used in the production of rayon, in the textile industry for processing fibers or fabrics before dyeing them, as well as in other industries. light industry. AT Food Industry sulfuric acid is used in the production of starch, molasses and a number of other products. Transport uses lead sulfuric acid batteries. Sulfuric acid is used for drying gases and for concentrating acids. Finally, sulfuric acid is used in nitration processes and in the manufacture of most explosives.

3. Raw material base for the production of sulfuric acid

The raw material base for the production of sulfuric acid is sulfur-containing compounds, from which sulfur dioxide can be obtained. In industry, about 80% of sulfuric acid is obtained from natural sulfur and iron (sulfuric) pyrites. Sulfur pyrite consists of the mineral pyrite and impurities. Pure pyrite () contains 53.5% sulfur and 46.5% iron. The sulfur content in sulfur pyrites can range from 35 to 50%. A significant place is occupied by waste gases from non-ferrous metallurgy, obtained by roasting non-ferrous metal sulfides and containing sulfur dioxide. Some industries use hydrogen sulfide as a raw material, which is formed during the purification of petroleum products from sulfur.

4. Methods for the production of sulfuric acid

Currently, sulfuric acid is produced in two ways: nitrous, which has existed for more than 20 years, and contact, mastered in industry in the late 19th and early 20th centuries. The contact method displaces the nitrous (tower) method. The first stage of sulfuric acid production by any method is the production of sulfur dioxide by burning sulfurous raw materials. After purification of sulfur dioxide (especially in the contact method), it is oxidized to sulfur trioxide, which combines with water to produce sulfuric acid. Oxidation under normal conditions proceeds extremely slowly. Catalysts are used to speed up the process.

In the contact method for the production of sulfuric acid, the oxidation of sulfur dioxide into trioxide is carried out on solid contact masses. Thanks to the improvement of the contact method of production, the cost of purer and highly concentrated contact sulfuric acid is only slightly higher than that of tower acid. Therefore, only contact shops are being built. Currently, over 80% of all acid is produced by the contact method.

Nitrogen oxides serve as a catalyst in the nitrous process. Oxidation occurs mainly in the liquid phase and is carried out in packed towers. Therefore, the nitrous method is called the tower method on the basis of hardware. The essence of the tower method lies in the fact that the sulfur dioxide obtained by burning sulfurous raw materials, containing approximately 9% and 9-10%, is purified from pyrite cinder particles and enters the tower system, consisting of several (four - seven) towers with a nozzle. Packed towers operate on the principle of ideal displacement in polythermal conditions. The gas temperature at the entrance to the first tower is about 350 °C. A number of absorption-desorption processes, complicated by chemical transformations, take place in the towers. In the first two or three towers, the packing is irrigated with nitrose, in which dissolved nitrogen oxides are chemically bound in the form of nitrosylsulfuric acid. At high temperature, nitrosylsulfuric acid is hydrolyzed according to the equation:

the latter reacts with nitrogen oxides in the liquid phase:

, being absorbed by water, also gives sulfuric acid:

Nitrogen oxides are absorbed by sulfuric acid in the next three to four towers according to the reaction, the reverse of equation 15.1. To do this, chilled sulfuric acid with a low nitrose content, flowing from the first towers, is fed into the towers. When the oxides are absorbed, nitrosylsulfuric acid is obtained, which is involved in the process. Thus, nitrogen oxides make a cycle and theoretically should not be consumed. In practice, due to incomplete absorption, there are losses of nitrogen oxides. the consumption of nitrogen oxides in terms of is 12-20 kg per ton of monohydrate. The nitrous method produces contaminated with impurities and diluted 75-77% sulfuric acid, which is used mainly for the production of mineral fertilizers.

5. Functional diagram of the production of sulfuric acid

The chemical scheme includes the reactions:

If the starting materials (raw materials) contain impurities, then the functional diagram (Fig. 15.4) includes the stage of gas purification after roasting. The first stage - roasting (combustion) - is specific for each type of raw material, and further it will be considered for pyrites and sulfur as the most common starting materials. The oxidation and absorption steps are basically the same in different processes for producing sulfuric acid. We will sequentially consider these stages (CTS subsystems for the production of sulfuric acid) from the standpoint of their fundamental technological, instrumental and regime solutions.

Rice. 4 Functional schemes for the production of sulfuric acid from sulfur (a) and sulfur pyrite (b) 1 - firing of sulfur-containing raw materials; 2 - cleaning and washing of the roasting gas; 3 - oxidation; 4 - absorption

5.1 Roasting of sulfur-containing raw materials

Roasting pyrite (pyrite) is a complex physical and chemical process and includes a number of consecutive or simultaneously occurring reactions:

thermal dissociation
gas-phase combustion of sulfur
burning pyrrhotite

Total reaction:

With a slight excess or lack of oxygen, a mixed iron oxide is formed:

.

Chemical reactions are practically irreversible and highly exothermic.

If it is used as a raw material (oil refining), then gas-phase combustion has the form of a chemical reaction:

,

those. is practically irreversible, exothermic and comes with a decrease in volume.

Thermal decomposition of pyrite begins already at a temperature of about 200 ° C and sulfur ignites at the same time. At temperatures above 680 °C, all three reactions proceed intensively. In industry, firing is carried out at 850-900 ° C. The limiting stage of the process is the mass transfer of the decomposition products into the gas phase and the oxidant to the reaction site. At the same temperatures, the solid component softens, which contributes to the adhesion of the particles. These factors determine the way the process is carried out and the type of reactor.

Initially, a shelf reactor (chamber furnace) was used (Fig. 5a). Pyrite is continuously supplied from above to the shelves, and the air from below passes through the fixed layers. Naturally, pyrite is lumpy (finely crushed would create significant hydraulic resistance and could easily stick together, which would create non-uniform combustion). Firing - continuous process, solid material is moved by special rakes rotating on a shaft located along the axis of the apparatus. The paddles of the rowers move the pieces of pyrite on the plates from top to bottom alternately from the axis of the apparatus to its walls and back, as shown by the arrows in the figure. This mixing prevents the particles from sticking together. The cinder is continuously removed from the bottom of the reactor. The reactor ensures the intensity of the process, measured by the amount of pyrites passing through the unit section of the reactor - no more than 200 kg/(m 2 h). In such a reactor, moving scrapers in the high-temperature zone complicate its design, uneven temperature conditions are created along the shelves, and it is difficult to organize heat removal from the reaction zone. Difficulties in heat removal do not allow obtaining roasting gas with a concentration of more than 8-9%. The main limitation is the impossibility of using small particles, while for a heterogeneous process the main way to accelerate the rate of transformation is particle crushing.

Rice. 5 Pyrite roasting reactors

a - shelf (1 - housing, 2 - shelves for pyrites, 3 - rotating scrapers, 4 - scraper drive axis); b - fluidized bed furnace (1 - body, 2 - heat exchanger). Arrows inside the apparatus - the movement of solid pyrites in reactors.

Small particles can be processed in a fluidized (fluidized) bed, which is implemented in furnaces KS - fluidized bed (Fig. 15.5, b). Pulverized pyrite is fed through a feeder into the reactor. The oxidizer (air) is fed from below through the distribution grate at a rate sufficient to weigh the solids. Their hovering in the bed prevents sticking and promotes good contact with the gas, equalizes the temperature field over the entire bed, ensures the mobility of the solid material and its overflow into the outlet pipe to remove the product from the reactor. In such a layer of moving particles, heat exchange elements can be placed. the heat transfer coefficient from the fluidized bed is comparable with the heat transfer coefficient from the boiling liquid, and thus effective heat removal from the reaction zone, its temperature control and the use of reaction heat are ensured. The intensity of the process increases to 1000 kg/(m 2 ·h), and the concentration in the roasting gas - up to 13-15%. The main disadvantage of KS furnaces is the increased dust content of the roasting gas due to mechanical erosion of moving solid particles. This requires more thorough cleaning of gas from dust - in a cyclone and an electrostatic precipitator. Pyrite firing subsystem is represented by the technological scheme shown in fig. 6.

Rice. 6 Technological scheme of pyrite roasting

1 - plate feeder; 2 - fluidized bed furnace (reactor); 3 - waste heat boiler; 4 - cyclone; 5 - electrostatic precipitator

As mentioned earlier, sulfur can be used as a raw material (native sulfur was previously indicated as a raw material, sulfur () in Fig. 15.6 .. can be used to release from boiling liquid, and thereby ensure). Sulfur is a fusible substance: melting point 113 °C. Before burning, it is melted using steam obtained by utilizing the heat of its combustion. Molten sulfur is settled and filtered to remove impurities present in natural raw materials and is pumped into the combustion furnace. Sulfur burns mainly in the vapor phase. To ensure its rapid evaporation, it must be dispersed in an air stream. For this, nozzle and cyclone furnaces are used.

Rice. 8 Technological scheme of sulfur combustion

1 - sulfur filter; 2 - collection of liquid sulfur; 3 - combustion furnace; 4 - waste heat boiler

During the combustion of sulfur, according to the reaction, part of the oxygen equimolarly passes into sulfur dioxide, and therefore the total concentration is both constant and equal to the concentration of oxygen in the source gas (), so that when sulfur is burned in air.

The gas from burning sulfur is richer in oxygen than from burning pyrites.

5.2 Gas flushing after firing

Pyrite calcination gases contain as impurities compounds of fluorine, selenium, tellurium, arsenic and some others, formed from impurities in the raw material. The natural moisture of the raw material also turns into gas. During combustion, some and possibly oxides of nitrogen are formed. These impurities lead either to corrosion of the equipment, or to poisoning of the catalyst, and also affect the quality of the product - sulfuric acid. They are removed in the washing compartment, a simplified diagram of which is shown in Fig. nine.

Rice. 9 Scheme of the washing section of the production of sulfuric acid

1, 2 - washing towers; 3 - wet filter; 4 - drying tower

5.3 Oxidation of sulfur dioxide

Reaction

According to the law of mass action, at equilibrium

The expression shows the relative change (decrease) in the volume of the reaction mixture. Equation 15.11 defines implicitly and is solved by fitting. The required degrees of conversion (about 99%) are achieved at temperatures of 400-420°C. Pressure does not greatly affect, therefore, in industry, the process is carried out at a pressure close to atmospheric.

Oxidation catalysts are prepared on the basis of vanadium oxide () with the addition of alkali metals deposited on silicon oxide. The reaction rate is described by the Boreskov-Ivanov equation:

where is the reaction rate constant;

=0.8 - constant;

, - partial pressures of the corresponding components, atm.

The temperature limits and their value for different catalysts may vary. For catalysts IK-1-6 and SVD, kJ/mol at K., these are low-temperature catalysts. Activity industrial catalysts at temperatures below 680 K, it is very small, and above 880 K, they are thermally deactivated. Therefore, the operating temperature range for most catalysts is 580-880 K, and the degree of conversion in the reactor, determined by the lower limit of this range, is 98%.

,

Rice. 11 Scheme of the oxidation reactor

1 - catalyst layer; 2 - intermediate heat exchangers; 3 - mixer; 4 - external heat exchanger; X g - cold gas input

The initial concentration of the processed gas is chosen so that the process mode is within the operating temperatures of the catalyst. Great importance at K leads to a sharp decrease in the reaction rate with decreasing temperature. In order for the adiabatic process in the first layer to develop intensively, the initial temperature must be at least 713 K. It is called the "ignition temperature" (it is lower for low-temperature catalysts). In the diagram "" the adiabatic process is represented by a straight line. Its slope is determined by the value of adiabatic heating. For oxidation, approximately 1% deg. The more (or the initial concentration -), the greater the heating. The process can develop to equilibrium, and the maximum (equilibrium) temperature should not exceed the allowable temperature. On fig. 10 this corresponds to an initial concentration of 7-8%. The low-temperature catalyst makes it possible to raise the concentration to 9-10%. The temperatures in the remaining layers are determined from optimization of the reactor regime.

5.4 Absorption of sulfur trioxide

Absorption of sulfur trioxide is the last step in the process in which sulfuric acid is formed. Interaction

proceeds quite intensively both in liquid and gaseous (vapor) phases. In addition, it can dissolve in itself, forming oleum. This product is convenient for transportation as it does not corrode even ordinary steels. Sulfuric acid solutions are extremely aggressive. Oleum is the main product of sulfuric acid production.

The "gas-liquid" equilibrium for the "" system is shown in fig. 3. A feature of this system is that in a wide range of solution concentrations in the vapor phase, almost pure water vapor is present (left side of the graph), and over oleum (solution c) in the gas phase prevails (right side of the graph). the same composition of the liquid and vapor phases (azeotropic point) will be at a sulfuric acid concentration of 98.3%. If it is absorbed with a solution with a lower concentration, then reaction 5 will also proceed in the vapor phase - a mist of sulfuric acid will form, which will leave the absorber with the gas phase. And these are product losses, and equipment corrosion, and emissions into the atmosphere. If absorbed by oleum, the absorption will be incomplete.

From these properties, a two-stage (two-tower) absorption scheme follows (Fig. 12). The gas containing after the reactor passes successively oleum 1 and monohydrate 2 absorbers. The other reaction component () is countercurrently fed into the monohydrate absorber. Due to the intensity of the circulation of the liquid (absorbent), it is possible to maintain a close to optimal concentration in it - 98.3% (an increase in concentration per passage of the liquid is not more than 1-1.5%). The technical name of such an acid is monohydrate, hence the name of the absorber. Absorption concentration conditions ensure complete absorption and minimal formation of sulfuric acid mist. The acid from the monohydrate absorber enters the oleum absorber. A 20% solution circulates in it, which is partially taken as the final product - oleum. Acid from the previous absorber - monohydrate - can also be a product.

The formation of sulfuric acid and the absorption of sulfur trioxide are exothermic processes. Their heat is removed in irrigation heat exchangers 3 on the liquid circulation line in the absorbers. At temperatures below 100 °C, almost 100% is absorbed. Sulfur dioxide is practically not absorbed.

Rice. 12 Scheme of absorption separation in sulfuric acid production

1 - oleum absorber; 2 - monohydrate absorber; 3 - refrigerators; 4 - acid collectors; 5 - spray separators

5.5 Double contact and double absorption system (DC/DA)

Despite the rather high degree of conversion - 98%, powerful sulfuric acid systems, producing up to 540 tons of product per day, emit more than 300 kg of sulfur dioxide into the atmosphere every hour. Based on the data on the equilibrium of the oxidation reaction, the degree of conversion can be increased by lowering the temperature in the last layers below 610 K or by increasing the pressure to more than 1.2 MPa. The possibility of lowering the temperature is limited by the activity of the available catalysts, increasing the pressure complicates the engineering design of the process, and therefore these methods have not yet received industrial application.

An effective way to increase the degree of conversion in a reversible reaction is to remove its product. The technological scheme of such a method is shown in fig. 13. At the first stage of oxidation, a three-layer reactor 1 was used. The concentration in the incoming gas is 9.5-10.5%. The degree of conversion at the outlet of the reactor is 90-95%. Intermediate absorption includes oleum 2 and monohydrate 3 absorbers. After them, the gas contains only 0.6-1%. To heat it up to the reaction temperature (690-695 K), a heat exchanger is used after the second layer of the reactor 1. The reactors of the first and second stages of oxidation are structurally combined in one housing. The degree of conversion of the remaining is approximately 95%, the total degree of conversion is 99.6-99.8%. Compare: if there were no intermediate absorption, then the degree of conversion of the remaining 1-0.6% in the presence would not exceed 50%. A small amount formed is completely absorbed in the second monohydrate absorber 3.

As can be seen, the amount of unconverted (and, consequently, emissions into the atmosphere) in the DC/DA system is reduced by almost 10 times compared to the single contact system. But for this it is necessary to increase the surface of the heat exchangers by 1.5-1.7 times.

Rice. 13 Technological scheme of the stages of contacting and absorption in the system "double contacting - double absorption"

I, III - the first and second stages of oxidation; II, IV - the first and second systems of absorption by water; 1 - reactor (the first and second stages of oxidation, located in the same building, are shown separately); 2 - oleum absorber; 3 - monohydrate absorber; 4 - remote heat exchangers of the reactor; 5 - acid refrigerators

6. WSA and SNOX™ Wet Gas Sulfuric Acid Technology - Sulfur and Nitrogen Oxide Control

The development of Topsoe's WSA technology for the removal of sulfur compounds from flue gases from the production of sulfuric acid began in the late 1970s. WSA technology is built on Topsoe's extensive experience in the sulfuric acid industry and an unwavering determination to move further and further in catalyst and process development. The main areas of research were the oxidation of SO2 on sulfuric acid catalysts and the process of acid condensation.

6.1 Basic Research

The ability to condense sulfuric acid vapor to produce concentrated sulfuric acid without emitting acid mist is a unique feature of the WSA technology, which has been achieved based on fundamental experimental and theoretical works made by Topsoe.

During cooling of the sulfuric acid vapor contained in the gas phase, spontaneous homogeneous formation of condensation centers, heterogeneous condensation and condensation on the walls occur simultaneously. To develop and improve the WSA capacitor, Topsoe's laboratories carry out fundamental research regarding these fundamentally important mechanisms of condensation.

Fig.4. Topsoe's glass tube technology is used in the WSA to condense sulfuric acid vapors

6.2 Development and optimization of technology

Pilot and plant level tests, along with detailed simulations of the WSA capacitor, are used to study the effect of capacitor design and operating conditions on capacitor performance in order to define design criteria and process control.

Another priority area of ​​our technical developments is the improvement of WSA glass tube technology and the continuous improvement of the quality of construction materials. The latter challenge requires our experience in material testing for the harsh conditions of sulfuric acid plants.

In order to fully exploit the potential of WSA technology, we use innovative methods to create process flow diagrams while implementing Topsoe's own calculation tools to optimally solve various industrial problems. One of the drivers for this development is the increasing attention to energy consumption and CO2 emissions around the world, which requires maximum heat recovery.

6.3 SNOX™ Technology

For the removal of sulfur and nitrogen oxides from flue gases, Topsoe has developed the SNOX™ technology, which combines WSA technology with SCR nitrogen oxide removal, providing optimal integration for the power industry.

7. Claus sulfur production

Premium Engineering LLC can offer four main Claus processes for the production of elemental sulfur from the acidic components of natural gas and refinery gases:

Straight-through (flame)

· Branched

Branched heated sour gas and air

Direct oxidation

1. The once-through Claus process (flame method) is used when the volume fractions of hydrogen sulfide in acid gases are above 50% and hydrocarbons are less than 2%. In this case, all acid gas is fed for combustion into the reactor furnace of the thermal stage of the Claus plant, made in the same building as the waste heat boiler. In the reactor furnace, the temperature reaches 1100-1300°C and the sulfur yield is up to 70%. Further conversion of hydrogen sulfide to sulfur is carried out in two or three stages on catalysts at a temperature of 220-260°C. After each stage, the resulting sulfur vapor condenses in surface condensers. The heat released during the combustion of hydrogen sulfide and the condensation of sulfur vapor is used to produce high and low pressure steam. The yield of sulfur in this process reaches 96-97%.

2. With a low volume fraction of hydrogen sulfide in acid gases (30-50%) and a volume fraction of hydrocarbons up to 2%, a branched scheme of the Claus process (one third to two thirds) is used. In this scheme, one third of the acid gas is combusted to produce sulfur dioxide, and two thirds of the acid gas stream enters the catalytic stage, bypassing the reactor furnace. Sulfur is obtained in the catalytic stages of the process by reacting sulfur dioxide with hydrogen sulfide contained in the rest (2/3) of the source acid gas. The sulfur yield is 94-95%.

3. When the volume fraction of hydrogen sulfide in acid gas is 15-30%, when using the third-two-thirds scheme, the minimum allowable temperature in the reactor furnace furnace (930 ° C) is not reached, the scheme with preheating of acid gas or air is used.

4. When the volume fraction of hydrogen sulfide in acid gas is 10-15%, a direct oxidation scheme is used, in which there is no high-temperature gas oxidation (combustion) stage. The acid gas is mixed with a stoichiometric amount of air and fed directly to the catalytic conversion stage. The sulfur yield reaches 86%.

To achieve the degree of sulfur recovery of 99.0-99.7%, three groups of methods for post-treatment of off-gases from the Claus process are used:

· Processes based on the continuation of the Claus reaction, i.e. on the conversion of H2S and SO2 to sulfur on a solid or liquid catalyst.

· Processes based on the reduction of all sulfur compounds into hydrogen sulfide with its subsequent extraction.

· Processes based on the oxidation of all sulfur compounds to SO2 or to elemental sulfur with their subsequent extraction.

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4.1 Installation of ELOU-AVT

The unit is designed to clean oil from moisture and salts, and for the primary distillation of oil into fractions used as raw materials for further processing. In table. 4.1. and 4.2. the material balances of the ELOU and AVT blocks are given, respectively.

The plant consists of three blocks: 1. Demineralization and dehydration. 2. Atmospheric distillation. 3. Vacuum distillation of fuel oil.

The raw material of the process is oil.

Products: Gas, Fractions 28-70 o C, 70-120 o C, 120-180 o C, 180-230 o C, 230-280 o C, 280-350 o C, 350-500 o C, and fraction, boiling over at temperatures above 500 o C.

Table 4.1

Material balance of the ELOU block

Table 4.2

Material balance of the AVT installation

balance sheet items	potential content,	Selection from potential in fractions of unity	actual selection,
				thousand tons/year
received:
Fraction 28-70 °С
Fraction 85-120 °С
Fraction 120-180 °С
Fraction 180-230 °C
Fraction 230-280 °С
Fraction 280-350 °C
Fraction 350-485 °С
Fraction >485 °С

4.2 Catalytic reforming

At the planned refinery, the catalytic reforming process is designed to improve the knock resistance of gasoline.

As a feedstock for reforming, we use a wide straight-run gasoline fraction 70 - 180 ºС from the CDU-AVT unit, as well as visbreaking, coking gasolines and hydrotreated stripping gasolines.

The mode of catalytic reforming installations depends on the type of catalyst, the purpose of the installation, and the type of feedstock. In table. Table 4.3 shows the performance of a selected UOP CCR ​​platform catalytic reformer with continuous catalyst regeneration.

Table 4.3

Technological mode of the installation of catalytic reforming fr. 70 - 180 °С

These installations are more economical in reducing the operating pressure while increasing the depth of conversion of raw materials. Moving bed reforming is the most modern industrial process model and provides consistently high gasoline yield and octane number, as well as maximum hydrogen yield at low process severity.

We will use the Axens HR-526 catalyst at the reformer. The catalyst is chlorine-promoted alumina with platinum (0.23% wt.) and rhenium (0.3% wt.) evenly distributed throughout the volume. The catalyst beads have a diameter of 1.6 mm and a specific surface area of ​​250 m 2 /g.

To ensure a long-term operation cycle of this catalyst, the feedstock must be purified from sulfur, nitrogen and oxygen-containing compounds, which is ensured by the inclusion of a hydrotreatment unit in the reformer.

The products of the catalytic reformer are:

Hydrocarbon gas - contains mainly methane and ethane, serves as fuel for oil refinery furnaces;

Stabilization head (hydrocarbons C 3 - C 4 and C 3 - C 5) - are used as raw materials for HFCs of saturated gases;

The catalyzate, the output of which is 84% ​​wt. used as a component of motor gasolines. It contains 55 - 58% wt. aromatic hydrocarbons and has an octane number (OM) = 100 points;

4.3 Hydrotreating

The process is designed to provide the necessary level of performance characteristics of light distillates, catalytic cracking feedstock, which today is determined mainly by environmental requirements. The quality of hydrotreating products is improved as a result of the use of destructive hydrogenation reactions of sulfur, nitrogen and oxygen-containing compounds and hydrogenation of unsaturated hydrocarbons.

We send a fraction of diesel fuel to the hydrotreatment unit, which boils away in the range of 180 - 350 ºС. The composition of the feedstock of the diesel fuel hydrotreater also includes light coking gas oil. Based on the data in Table. 1.6, the sulfur content in this fraction is taken equal to 0.23% wt. as in the fraction 200 - 350ºС.

The main parameters of the technological regime of the diesel fuel hydrotreater are presented in Table. 4.4.

Table 4.4

Technological mode of the diesel fuel hydrotreater

In world practice, aluminum-cobalt-molybdenum (ACM) and aluminum-nickel-molybdenum (ANM) are most widely used in hydrogenation processes. AKM and ANM hydrotreatment catalysts contain 2–4 wt %. Co or Ni and 9 - 15% wt. MoO 3 on active γ-alumina. At the stage of start-up operations or at the beginning of the raw cycle, they are subjected to sulfidation (sulfurization) in a stream of H 2 S and H 2 , while their catalytic activity increases significantly. In our project, at the diesel fuel hydrotreatment unit, we will use a domestic catalyst of the GS-168sh brand, with the following characteristic:

bulk density ÷ 750 kg/m 3 ;

carrier ÷ aluminosilicate;

granule diameter ÷ 3 – 5 mm;

interregeneration period ÷ 22 months;

total service life ÷36 – 48 months.

The plant's products are:

hydrotreated diesel fuel;

distilled gasoline - used as a raw material for a catalytic reformer, has a low (50 - 55) octane number;

hydrogen sulfide - is sent as raw material to the elemental sulfur production unit;

fuel gas.

The guidelines suggest that 100% of the diesel hydrotreater feedstock has the following yield:

hydrotreated diesel fuel - 97.1% wt;

distilled gasoline - 1.1% wt.

The output of hydrogen sulfide in % wt. on raw materials is determined by the formula

x i is the yield of hydrotreated products in fractions of a unit;

32 is the atomic mass of sulfur.

Fraction 230-350 o C contains sulfur 0.98% wt. The composition of the feedstock of the diesel fuel hydrotreater also includes light coking gas oil. The sulfur content in environmentally friendly diesel fuel is 0.01% wt.

Products output:

H 2 S \u003d 0.98-(0.01 * 0.971 + 0.01 * 0.011) * 34/32 \u003d 0.97%

4.4 Gas fractionation plant (HFC)

The unit is designed to produce individual light hydrocarbons or hydrocarbon fractions high purity from refinery gases.

Gas fractionation plants are subdivided according to the type of processed raw materials into HFCs of saturated and HFCs of unsaturated gases.

The raw material for HFCs of saturated gases is gas and the AVT stabilization head mixed with the stabilization heads for the catalytic reforming of the gasoline fraction and hydrocracking of vacuum gas oil.

In table. 4.5 shows the process mode of HFC saturated gases.

Table 4.5

Technological mode of HFC distillation columns of saturated gases

distillation columns	Shared Components	Bottom temperature, °С	Top temperature, °С	Pressure, MPa
K-1 (deethanizer)	C 2 H 6 / C 3 H 8 +
K-2 (propane)	C 3 H 8 / ΣC 4 H 10 +
K-3 (butane)	ΣC 4 H 10 / ΣC 5 H 12 +
K-4 (isobutane)	iso- C 4 H 10 / n- C 4 H 10
K-5 (pentane)	ΣC 5 H 12 / C 6 H 14 +
K-6 (isopentane)	iso- C 5 H 12 / n- C 5 H 12

HFC products of saturated gases - narrow hydrocarbon fractions:

ethane - used as a raw material for the production of hydrogen, as well as a fuel for process furnaces;

propane - used as a raw material for pyrolysis, household liquefied gas, refrigerant;

isobutane - serves as a raw material for alkylation plants and the production of synthetic rubber;

butane - used as household liquefied gas, a raw material for the production of synthetic rubber, in winter it is added to commercial motor gasoline to provide the required saturated vapor pressure;

isopentane - used as a component of high-octane gasolines;

pentane - is a raw material for catalytic isomerization processes.

When separating unsaturated hydrocarbon gases, AGFU units (absorption-gas fractionation unit) are used. Their distinguishing feature is the use of technology for the absorption of hydrocarbons C 3 and higher by a heavier hydrocarbon component (fractions C 5 +) for the separation of dry gas (C 1 - C 2) in the K-1 column. The use of this technology makes it possible to reduce the temperatures in the columns and thereby reduce the likelihood of polymerization of unsaturated hydrocarbons. The raw materials of AGFU of unsaturated gases are gases of secondary processes, namely: catalytic cracking, visbreaking and coking.

The main parameters of the technological mode of the AGFU installation of unsaturated gases are presented in Table. 4.6.

Table 4.6

Technological mode of distillation columns AGFU of unsaturated gases

distillation columns	Shared Components	Bottom temperature, °С	Supply temperature, °С	Top temperature, °С	Pressure, MPa
K-1 (fractionating absorber)	C 2 - / ΣC 3 +
K-2 (stabilization column)	ΣC 3 - ΣС 5 / ΣC 6 +
K-3 (propane)	ΣC 3 / ΣC 4 +
K-4 (butane)	ΣC 4 / ΣС 5 +

The products of processing of unsaturated hydrocarbon raw materials are the following fractions:

propane-propylene - used as a raw material for polymerization and alkylation plants, production of petrochemical products;

butane-butylene - is used as a feedstock for the alkylation unit in order to produce alkylate (a high-octane component of commercial motor gasoline).

4.5 Catalytic isomerization of light gasoline fractions

The catalytic isomerization unit is designed to increase the octane number of light gasoline fraction 28 - 70ºС of the gasoline secondary distillation unit by converting paraffins of normal structure into their isomers with higher octane numbers.

There are several variants of the process of catalytic isomerization of paraffinic hydrocarbons. Their differences are due to the properties of the catalysts used, the process conditions, as well as the adopted technological scheme (“per pass” or with the recycle of unconverted normal hydrocarbons).

The isomerization of paraffinic hydrocarbons is accompanied by side reactions of cracking and disproportionation. To suppress these reactions and maintain the activity of the catalyst at a constant level, the process is carried out at hydrogen pressures of 2.0–4.0 MPa and circulation of a hydrogen-containing gas.

The projected refinery uses a low-temperature isomerization process. The parameters of the technological mode of fraction isomerization 28 - 70ºС are given in Table. 4.7.

Table 4.7

Technological mode of the catalytic

isomerization of light gasoline fraction

During the isomerization process n- alkanes, modern bifunctional catalysts are used, in which platinum and palladium are used as a metal component, and fluorinated or chlorinated aluminum oxide as a carrier, as well as aluminosilicates or zeolites introduced into the aluminum oxide matrix.

It is proposed to use a low-temperature isomerization catalyst based on sulfated zirconia CI-2 containing platinum 0.3-0.4% wt. deposited on alumina.

The main product of the unit is isomerizate (OCM 82 - 83 points), used as a high-octane component of motor gasoline, responsible for its starting characteristics.

Together with the isomerizate, dry saturated gas is obtained in the process, which is used at the plant as a fuel and raw material for hydrogen production.

4.6 Bitumen production

This unit at the projected refinery is designed to produce road and construction bitumen.

The raw material of the bitumen production plant is the residue of vacuum distillation of fuel oil (tar).

For the production of bitumen, the following methods are used:

deep vacuum distillation (obtaining residual raw materials);

oxidation of petroleum products with air at high temperature (obtaining oxidized bitumen);

compounding of residual and oxidized bitumen.

Table 4.8.

Table 4.8

Technological mode of the bitumen production unit with an oxidizing column

road bitumens used in road construction for the preparation of asphalt concrete mixtures;

construction bitumen used in the performance of various construction works, in particular for waterproofing the foundations of buildings.

4.7 Catalytic cracking with hydrotreating

The catalytic cracking process is one of the most common large-scale deep oil refining processes and to a large extent determines the technical and economic performance of modern and prospective fuel oil refineries.

The process is designed to obtain additional quantities of light oil products - high-octane gasoline and diesel fuel - by decomposition of heavy oil fractions in the presence of a catalyst.

As a raw material for the plant at the projected refinery, vacuum gas oil of direct distillation of oil (fraction 350 - 500ºС) after preliminary upgrading is used, which is used as a catalytic hydrotreatment from harmful impurities - sulfur, nitrogen and metals.

The catalytic cracking process is planned to be carried out on a domestic cracking unit with a G-43-107 riser reactor on a microspherical zeolite-containing catalyst.

The main factors influencing the catalytic cracking process are: the properties of the catalyst, the quality of the feedstock, the temperature, the duration of the contact between the feedstock and the catalyst, the catalyst circulation rate.

The temperature in this process is the regulator of the depth of the catalytic cracking process. As the temperature rises, the yield of gas increases, and the amount of all other products decreases. At the same time, the quality of gasoline is slightly improved due to aromatization.

The pressure in the reactor-regenerator system is maintained almost constant. An increase in pressure somewhat worsens the selectivity of cracking and leads to an increase in gas and coke formation.

In table. 4.9 shows the indicators of the technological mode of the catalytic cracking unit with a riser reactor.

Table 4.9

Technological mode of the catalytic cracking unit

Process conditions	established norm
Temperature, ºС
in the reactor
in the regenerator
Pressure, MPa
in the reactor
in the regenerator
Mass feed rate of raw materials, h -1
Catalyst circulation rate

Catalysts of modern catalytic cracking processes carried out at high temperatures are complex multicomponent systems consisting of a matrix (carrier), an active component - zeolite, and auxiliary active and inactive additives. Synthetic amorphous aluminosilicate with a high specific surface area and optimal pore structure is mainly used as a matrix material for modern catalysts. Usually, in industrial amorphous aluminosilicates, the content of aluminum oxide is in the range of 6–30% wt. The active component of cracking catalysts is a zeolite, which is an aluminosilicate with a three-dimensional crystal structure of the following general formula

Me 2 / n O Al 2 O 3 x SiO 2 at H 2 O,

which allows to carry out secondary catalytic transformations of raw hydrocarbons with the formation of final target products. Auxiliary additives improve or give some specific physico-chemical and mechanical properties to zeolite-containing aluminosilicate catalysts (CSC) cracking. As promoters that intensify the regeneration of a coked catalyst, platinum applied in low concentrations (<0,1 %мас.) непосредственно на ЦСК или на окись алюминия с использованием как самостоятельной добавки к ЦСК.

At the catalytic cracking unit, we will use a domestic catalyst of the KMTs-99 brand, with the following characteristic:

gasoline yield ÷ 52 - 52.5% wt.;

octane number (IM) ÷ 92;

catalyst consumption ÷ 0.4 kg/t of raw material;

average particle size ÷ 72 microns;

bulk density ÷ 720 kg/m 3 .

The products of the catalytic cracking unit are:

In this project, the feedstock of the catalytic cracking unit is a part of the straight-run oil fraction 350 - 500 ° C with a sulfur content of 1.50% wt.

To calculate the yield of hydrogen sulfide in the process of hydrotreating vacuum gas oil, we take the sulfur content in the products and the yield of products as follows:

hydrotreated vacuum gas oil - 94.8% wt;

distilled gasoline - 1.46% wt.

Hydrotreating products also include: fuel gas, hydrogen sulfide and losses.

where S 0 – sulfur content in the feedstock, wt %;

S i– sulfur content in the end products of the process, wt %;

X i is the yield of hydrotreated products in fractions of a unit;

34 – molecular weight of hydrogen sulfide;

32 is the atomic mass of sulfur.

H 2 S \u003d (1.50– (0.2 * 0.948 + 0.2 * 0.014) * 34/32 \u003d 1.26%

4.8 Coking

The unit is designed to produce petroleum coke, to produce additional amounts of light oil products from heavy oil residues.

The raw material of the coking unit is a part of the tar (residue of the vacuum distillation of fuel oil) with a coking capacity of 9.50% wt. and a sulfur content of 0.76% wt.

At the projected refinery, the coking process will be carried out at a delayed (semi-continuous) coking unit (DCU).

In table. 4.10 shows the technological mode of the ultrasonic testing unit.

Table 4.10

Technological mode of the ultrasonic testing unit

The products of the plant are:

petroleum coke - used in the production of anodes for aluminum smelting and graphite electrodes, for the production of electrolytic steel, used in the production of ferroalloys, calcium carbide;

gas and stabilization head - contains mainly unsaturated hydrocarbons and is used as a raw material for HFCs of unsaturated hydrocarbons;

gasoline - contains up to 60% unsaturated hydrocarbons, is not chemically stable enough, RONM = 60 - 66 points, after deep hydrotreating it is used as a feedstock for a catalytic reformer;

light gas oil - serves as a component of diesel fuel;

heavy gas oil is a component of boiler fuel.

4.9 Visbreaking

The unit is designed to reduce the viscosity of heavy oil residues in order to obtain a component of stable boiler fuel.

The raw material for visbreaking is tar (fraction > 500 °C) from the vacuum unit of the CDU-AVT unit.

At the projected refinery, we use a visbreaking unit with an external reaction chamber. In visbreaking of this direction, the required degree of raw material conversion is achieved at a milder temperature regime (430–450 °C), a pressure of no more than 3.5 MPa, and a long residence time (10–15 min).

The products of the plant are:

gas - used as fuel gas;

gasoline - characteristic: OCMM = 66 - 72 points, sulfur content - 0.5 - 1.2% wt, contains many unsaturated hydrocarbons. Used as reforming feedstock;

cracked residue - used as a component of boiler fuel, has a higher calorific value, lower pour point and viscosity than straight-run fuel oil.

4.10 Alkylation

The purpose of the process is to obtain gasoline fractions with high stability and knock resistance using the reaction of isobutane with olefins in the presence of a catalyst.

The feedstock of the plant is isobutane and butate-butylene fraction from the HFC unit of unsaturated gases.

The alkylation process is the addition of butylene to paraffin to form the corresponding higher molecular weight hydrocarbon.

At the projected refinery, we use a sulfuric acid alkylation unit. Thermodynamically, alkylation is a low-temperature reaction. The temperature limits of industrial sulfuric acid alkylation are from 0°С to 10°С, since at temperatures above 10–15 °С, sulfuric acid begins to intensively oxidize hydrocarbons.

The pressure in the reactor is chosen in such a way that all hydrocarbon feedstock or its main part is in the liquid phase. The pressure in industrial reactors is on average 0.3 - 1.2 MPa.

Sulfuric acid is used as an alkylation catalyst. The choice of this substance is due to its good selectivity, ease of handling liquid catalyst, relative cheapness, long cycles of plant operation due to the possibility of regeneration or continuous replenishment of catalyst activity. For alkylation of isobutane with butylenes, we use 96 - 98% H 2 SO 4 . The products of the plant are:

4.11 Sulfur production

Hydrogen sulfide, released from process gases of thermohydrocatalytic processes for processing a given oil, is used at refineries for the production of elemental sulfur. The most common and efficient industrial method for obtaining sulfur is the Claus catalytic oxidative conversion of hydrogen sulfide.

The Claus process is carried out in two stages:

stage of thermal oxidation of hydrogen sulfide to sulfur dioxide in the reactor furnace

stage of catalytic conversion of hydrogen sulfide and sulfur dioxide in the R-1 and R-2 reactors

The technological mode of the installation is presented in table. 4.12.

Table 4.12

Technological mode of the sulfur production unit

Process conditions	established norm
Overpressure, MPa
Temperature, ºС
in the reactor furnace
at the outlet of waste heat boilers
at the entrance to the R-1 reactor
at the outlet of the R-1 reactor
at the R-2 reactor inlet
at the outlet of the R-1 reactor

We use active aluminum oxide as a catalyst, the average service life of which is 4 years.

Sulfur is widely used in the national economy - in the production of sulfuric acid, dyes, matches, as a vulcanizing agent in the rubber industry, etc.

4.12 Hydrogen production

The widespread introduction of hydrogenation and hydrocatalytic processes at the proposed refinery requires a large amount of hydrogen, in addition to that supplied from the catalytic reformer.

The hydrogen balance for the projected refinery with deep processing of Teplovskaya oil is presented in Table. 4.13.

Table 4.13

Hydrogen balance for refineries with deep

processing of Teplovskaya oil of the coal-bearing horizon.

For the production of hydrogen, we use, as the most cost-effective method, the method of steam catalytic conversion of gas raw materials.

The interaction of methane (or its homologues) with water vapor proceeds according to the equations

Table 4.14

Distribution of straight-run fractions of Teplovskaya oil by technological processes, % wt.

Name	Actual selection, % wt. for oil			catalytic isomerization	Catalytic reforming to obtain high octane gasoline		Hydrotreatment of diesel fuel	catalytic cracking	Delayed coking	Visbreaking	Bitumen production
Oil fractions:
gas + reflux
Fraction 28-70 °С
Fraction 70-120 °C
Fraction 120-180 °С
Fraction 180-230 °C
Fraction 230-280 °С
Fraction 280-350 °C
Fraction 350-500 °C
Fraction over 500 °C
Productivity for straight-run raw materials, thousand tons in year

SCHEME OF REFINERY