Method and plant for producing ammonia

Abstract

The group of inventions relates to a method and plant for producing ammonia from by-products of oil or gas refining and can be used in the chemical industry and in the production of fertilizers. What is proposed is a method for producing ammonia which includes a) a stage of steam-air reforming a hydrogen-containing gas to produce a converted gas; b) a stage of converting carbon monoxide and separating carbon dioxide from the converted gas to produce a synthesis gas; and c) a stage of producing ammonia from the synthesis gas produced in stage b), wherein the hydrogen-containing gas fed to stage a) is a product of hydrocarbon dehydrogenation processes performed at oil or gas refining facilities. Also proposed is a plant for producing ammonia. The technical result of the group of inventions is an increase in the energy efficiency and environmental friendliness of technology for producing ammonia from by-products of oil and gas refining, together with a reduction in metal consumption, specific energy consumption and specific fuel gas consumption, in addition to which, the residual content of unconverted hydrocarbons after steam-air reforming is not more than 1 vol.%.

Description

[0001] METHOD FOR PRODUCING AMMONIA AND AN INSTALLATION FOR ITS IMPLEMENTATION

[0002] Field of technology

[0003] The group of inventions relates to a method and installation for obtaining ammonia from by-products of oil or gas processing and can be used in the chemical industry and in the production of fertilizers.

[0004] Prior art

[0005] The main traditional source of raw materials for obtaining ammonia and, subsequently, urea, is natural gas (NG).

[0006] The classical method of obtaining ammonia from natural gas includes purification of natural gas from sulfur compounds, two-stage steam (stage I) and steam-air (stage II) conversion of natural gas in a tubular furnace and in a shaft reactor, respectively, two-stage conversion of carbon monoxide, purification of the converted gas from carbon dioxide, methanation of monoxide and carbon dioxide, compression of the nitrogen-hydrogen mixture, synthesis of ammonia at a pressure above 30 MPa (Azotchik Handbook. - M., Chemistry, 1986, v.1, pp.83, 84, IZ, 213, 222, 360-364).

[0007] A disadvantage of using natural gas as a feedstock for ammonia production is the need for efficient conversion of natural gas into carbon oxides, which necessitates the use of a primary reformer—a metal-intensive piece of equipment that consumes large amounts of fuel gas. On average, 290 Nm is fed to the reformer for combustion. 3Fuel gas per ton of ammonia. Burning large quantities of natural gas increases greenhouse gas emissions, reducing the environmental friendliness of the technology. Furthermore, natural gas is a primary source of raw materials: saved natural gas can be usefully used as fuel in other technological processes.

[0008] Thus, the problem of finding alternative sources of raw materials suitable for producing ammonia arises.

[0009] It is widely known that hydrogen-containing gas (HCG) is a byproduct of hydrocarbon dehydrogenation processes at oil and gas refineries. At most refineries, HCG is sent to a PSA, where hydrogen is recovered and then burned as fuel. Such technologies are characterized by low energy efficiency and environmental friendliness. However, technical solutions are known that allow the use of HCG as a feedstock for ammonia production.

[0010] Thus, US Patent No. US8932456B2, published on January 13, 2015, discloses a method for producing ammonia from hydrogen-containing off-gas from petroleum refining products. In the proposed method, hydrogen-containing gas is obtained from petroleum fractions and then sent to a steam reformer and a hydrogen recovery unit. The resulting hydrogen stream, along with a nitrogen stream obtained from an air separation unit, is sent to ammonia synthesis.

[0011] The disadvantages of the proposed invention include the production of ammonia from hydrogen and nitrogen streams obtained in complex hydrogen extraction and air separation units, which increases the metal consumption of the technology. In hydrogen extraction units (such as PSA), some of the hydrogen is consumed in regeneration processes, reducing the efficiency of the technology. Furthermore, steam reforming, used to increase the hydrogen content in hydrogen-containing gas, is carried out at low temperatures, reducing the degree of conversion of hydrocarbons to hydrogen, reducing the energy efficiency of the technology and reducing ammonia yield. Steam reforming also requires the use of a primary reforming furnace—a metal-intensive piece of equipment that consumes large quantities of fuel gas. Combustion of large quantities of natural gas leads to increased greenhouse gas emissions, reducing the environmental friendliness of the technology.In addition, natural gas is a primary source of raw materials: saved natural gas can be usefully used in other technological processes as fuel.

[0012] The closest analogue (prototype) of the invention is the method for producing ammonia from hydrogen-containing gas formed as a byproduct of the pyrolysis of an ethanepropane fraction, as described in Russian patent RU2710228C1, published on December 25, 2019. The resulting hydrogen-containing gas, consisting of methane and hydrogen, is fed to a PSA, where hydrogen is recovered, some of which is used for ammonia synthesis. Nitrogen for ammonia production is obtained in an air separation unit. The proposed method does not require a metal-intensive steam reforming furnace.

[0013] The disadvantages of the proposed invention include the production of ammonia from hydrogen and nitrogen streams obtained in complex hydrogen extraction and air separation units, which increases the metal consumption of the technology and reduces energy efficiency. In hydrogen extraction units (such as PSA), some of the hydrogen is consumed in regeneration processes, reducing the efficiency of the technology. Furthermore, the proposed method does not convert the methane remaining in the hydrogen sulfide gas at all; it is sent for combustion, which reduces the production of the valuable product—hydrogen—and, consequently, reduces the yield of ammonia.

[0014] Disclosure of invention

[0015] The objective and technical result of the proposed invention is to increase the energy efficiency and environmental friendliness of the technology for obtaining ammonia from by-products of oil and gas processing while reducing metal consumption, specific energy consumption, specific fuel gas consumption, and also with a residual content of unconverted hydrocarbons after steam-air reforming not exceeding 1 vol.%.Additionally, there is no need for a metal-intensive air separation unit and a metal-intensive primary reforming furnace that consumes large amounts of fuel gas; the technology is more environmentally friendly due to the beneficial use of carbon dioxide from flue gases; the ability to flexibly regulate the hydrogen content in ammonia synthesis gas; the ability to produce urea from flexibly regulated amounts of ammonia and carbon dioxide; an increase in the productivity of the ammonia production technology by 57.2%; the specific fuel gas consumption for combustion does not exceed 100 Nm. 3 per ton of ammonia.

[0016] In order to solve the stated problem and achieve the technical result, a method for producing ammonia is proposed, which includes a) a stage of steam-air reforming of hydrogen-containing gas to obtain converted gas; b) a stage of converting carbon monoxide and separating carbon dioxide from the converted gas to obtain synthesis gas; c) a stage of obtaining ammonia from the synthesis gas obtained in stage b), wherein the hydrogen-containing gas fed to stage a) is a by-product of hydrocarbon dehydrogenation processes at oil or gas processing plants.

[0017] Hydrogen-containing gas (HCG) is a gas with a high hydrogen content (10% or more) that is formed in various industrial processes, particularly through the dehydrogenation of hydrocarbons. Examples of such processes include pyrolysis and catalytic reforming (aromatization) of hydrocarbon fractions entering oil or gas refineries.

[0018] Dehydrogenation is the reaction of hydrogen separation from an organic compound molecule. Steam-air reforming is the production of gas with a high H2 and CO2 content by converting hydrocarbons with oxidizing agents: air and steam.

[0019] It will be obvious to a specialist that steam-air reforming is a special case of autothermal reforming (ATR) - in the case when air is used as an oxidizer in ATR.

[0020] Using waste from gas and petrochemical production as feedstock leads to more environmentally friendly processes. The hydrogen sulfide gas (H2S), a byproduct of dehydrogenation processes, is not burned, creating toxic emissions, but is effectively used to produce valuable products such as ammonia. Furthermore, the ammonia production process does not consume natural gas, which can be effectively used in other processes.

[0021] Steam-air reforming of HSG allows for the introduction of nitrogen, also present in the air, into the process flow along with the oxygen oxidizer, eliminating the need for a metal- and energy-intensive air separation unit. Furthermore, steam-air reforming facilitates the most efficient oxidation of hydrocarbons contained in HSG. In the present invention, the residual amount of hydrocarbons after steam-air reforming does not exceed 1 vol.%. Furthermore, the selected reforming type consumes less fuel gas for steam generation—only 98.5 Nm. 3per ton of ammonia, which is almost three times less than the natural gas consumption for steam generation in primary reformers. Furthermore, the hydrogen needed for ammonia production is generated by converting hydrogen-rich gas during the reforming stage, rather than by separation in a PSA, eliminating the need for a metal-intensive, energy-consuming pressure swing adsorption unit and avoiding the loss of hydrogen used in the PSA for regeneration processes.

[0022] Preferably, the dehydrogenation of hydrocarbons in oil or gas refining plants includes pyrolysis of the ethane-propane fraction and / or pyrolysis of the gasoline fraction and / or pyrolysis of the ligroin fraction (naphtha) and / or catalytic reforming of the gasoline fraction and / or catalytic reforming of the ligroin fraction (naphtha).

[0023] During pyrolysis the following reaction occurs:

[0024] С211Н4П+2 — ШС2Н4 + Нг

[0025] During the aromatization process (catalytic reforming), the following reaction occurs:

[0026] SgpNgp+g SpNgp-b + 4Ng

[0027] Pyrolysis of the ethane-propane fraction occurs with the release of the main products - ethylene and propylene, as well as a by-product - hydrogen-containing gas, which, in addition to hydrogen, also contains methane and, in some cases, impurity amounts of Cr+ hydrocarbons.

[0028] In this application, gasoline fractions (gasoline) are understood to mean petroleum fractions with a boiling point of up to 140°C. Predominantly, a mixture of Cs-Cii hydrocarbons.

[0029] In this application, the ligroin fraction (naphtha) refers to petroleum fractions with a boiling point of 140-180°C, primarily a mixture of CS-CM hydrocarbons.

[0030] Catalytic reforming and pyrolysis of gasoline and ligroin fractions occurs with the release of the main products - unsaturated hydrocarbons, in particular aromatic ones, as well as with the formation of a by-product - hydrogen-containing gas, which, in addition to hydrogen, also contains methane and, in some cases, impurity quantities of Cr+ hydrocarbons.

[0031] The processes of pyrolysis and catalytic reforming proceed with the release of unsaturated hydrocarbons - the main product, as well as with the release of a large amount of H2S as a by-product, which can be effectively used to produce ammonia.

[0032] Preferably, at the stage of dehydrogenation of hydrocarbons, CO2 is separated from the flue gases leaving the furnaces of the dehydrogenation processes.

[0033] The extraction of carbon dioxide from flue gases prevents their emission into the atmosphere and further improves the environmental friendliness of the technology.

[0034] Preferably, CO2 is separated from flue gases emitted from pyrolysis furnaces or catalytic reforming furnaces.

[0035] The extraction of carbon dioxide from flue gases prevents their emission into the atmosphere and further improves the environmental friendliness of the technology.

[0036] Preferably, the ammonia obtained in step c) together with the CO2 obtained in step b) and separated from the flue gas are sent to the synthesis of urea.

[0037] The possibility of isolating carbon dioxide during the ammonia production process makes it possible to obtain urea exclusively from industrial waste.

[0038] Preferably, the amount of CO2 supplied to the urea synthesis from flue gases is adjusted based on the amount of ammonia obtained in step c) and the CO2 obtained in step b) such that the molar ratio of ammonia to the total amount of carbon dioxide approaches the stoichiometric ratio required for urea production. During ammonia production, the carbon dioxide released in step b) is obtained in a deficit relative to ammonia, relative to the stoichiometric ratio (1:2) required for urea production. Flue gases are an additional source of carbon dioxide; its addition allows for flexible adjustment of the amount of urea produced. That is, either two products, ammonia and urea, or only urea, can be obtained, depending on the consumer's needs.

[0039] Preferably, step c) comprises removing purge gas from the ammonia synthesis loop.

[0040] Purge gas is a portion of the recycle gas withdrawn from the ammonia synthesis circuit (ammonia production unit) after the product ammonia separator. Purge gases, in addition to N2, H2, and NH3, contain inert impurities (CH4, Ar, He). Their presence negatively impacts the ammonia synthesis process.

[0041] Removing purge gas from the synthesis circuit reduces the amount of inerts in the circulation circuit and, as a consequence, reduces the pressure in the circulation circuit and reduces the metal consumption of the equipment (lower pressure requires equipment with thinner walls).

[0042] Preferably, the purge gas is directed to a hydrogen recovery unit.

[0043] The purge gas contains hydrogen, which can be used in the technology, further increasing its energy efficiency.

[0044] Preferably, the hydrogen separated from the purge gas is added to the synthesis gas obtained in step b).

[0045] If the hydrogen-containing gas entering the reformer has a high hydrocarbon content, excess air is added to maximize hydrocarbon oxidation. Consequently, more nitrogen is introduced into the system than is necessary to maintain the stoichiometry of the ammonia production reaction in the synthesis loop. The missing hydrogen can be obtained from the purge gas, further increasing the energy efficiency of the process.

[0046] Preferably, the amount of hydrogen added to the synthesis gas obtained in step b) is adjusted so that the ratio of hydrogen to nitrogen in the synthesis gas sent to step c) tends to the stoichiometric ratio required to produce ammonia.

[0047] The ability to flexibly regulate the hydrogen content in the syngas allows for further improvements in the energy efficiency of the technology. Preferably, cryogenic purification of the resulting syngas is performed at stage b).

[0048] Cryogenic purification removes excess nitrogen from syngas, thereby ensuring a hydrogen-to-ammonia ratio in the syngas that approaches stoichiometric values. Furthermore, cryogenic purification removes inerts from the syngas, which reduces the pressure in the circulation loop and the metal requirements of the equipment (lower pressures require equipment with thinner walls).

[0049] Preferably, step b) of separating carbon dioxide comprises amine scrubbing.

[0050] Amine purification is carried out at process pressure, which further reduces energy consumption. Furthermore, conducting the process at pressures above atmospheric pressure reduces the consumption of absorbent for purification.

[0051] Preferably, hydrogen-containing gas is fed to stage a) of steam-air reforming at a temperature of at least 650°C and a pressure of 2-5 MPa; air is fed at a temperature of 450-650°C and a pressure of 2-5 MPa; and converted gas is obtained at a temperature of 900-1050°C at a pressure of 2-5 MPa.

[0052] The above parameters are the most preferable for the reforming processes.

[0053] Also, in order to solve the above-mentioned problem and achieve the claimed technical result, an ammonia production unit is proposed, comprising a steam-air reforming unit connected to a hydrogen-containing gas supply line and a converted gas removal line; a carbon monoxide conversion and carbon dioxide extraction unit connected to a converted gas supply line, a synthesis gas removal line L1 and a carbon dioxide removal line L2; an ammonia production unit connected to the synthesis gas supply line and the ammonia removal line; wherein the hydrogen-containing gas supply line is configured to feed a product from a hydrocarbon dehydrogenation unit at oil or gas processing plants to the steam-air reforming unit.

[0054] In this application, a "line" refers to a means for delivering flow from one location to another, which includes, in particular, the necessary pipes and connecting elements, as well as, if necessary, control devices and equipment. In this application, a "unit" refers to a device or set of devices that ensures the implementation of the function specified for that unit.

[0055] All advantages of the present invention stated in relation to the method for producing ammonia are equally applicable to the claimed installation and are not repeated here in order to avoid unnecessary duplication.

[0056] Preferably, the hydrocarbon dehydrogenation unit at oil or gas refining plants includes an ethane-propane fraction pyrolysis unit and / or a gasoline fraction pyrolysis unit and / or a ligroin fraction (naphtha) pyrolysis unit and / or a gasoline fraction catalytic reforming unit and / or a ligroin fraction (naphtha) catalytic reforming unit.

[0057] Preferably, the hydrocarbon dehydrogenation unit includes a dehydrogenation process furnace configured to separate and remove a stream of carbon dioxide along line L3 from flue gases generated in the dehydrogenation process furnace.

[0058] Preferably, the pyrolysis units of the ethane-propane fraction and / or the gasoline fraction and / or the ligroin fraction include a pyrolysis furnace, and the catalytic reforming units of the gasoline fraction and / or the ligroin fraction include a catalytic reforming furnace, wherein the pyrolysis and / or catalytic reforming furnaces are configured to separate and remove a stream of carbon dioxide along line L3 from the flue gases formed in the pyrolysis and catalytic reforming furnaces.

[0059] Preferably, the installation includes a urea production unit connected to an ammonia supply line, a carbon dioxide supply line L2 and a carbon dioxide supply line L3.

[0060] Preferably, the ammonia feed line, lines L2, L3 are equipped with volumetric flow rate control means designed to control the amount of urea produced and to ensure that the molar ratio of the amount of ammonia to the total amount of carbon dioxide is maintained, tending to the stoichiometric ratio required to produce urea.

[0061] Preferably, the ammonia production unit is configured to divert a purge gas flow from the ammonia synthesis circuit.

[0062] Preferably, the installation includes a unit for separating hydrogen from the purge gas, connected to the purge gas supply line, and the hydrogen removal line L4.

[0063] Preferably, the synthesis gas outlet line L1 is connected to the hydrogen supply line L4. Preferably, the lines LI and L4 are equipped with volumetric flow rate control means designed to ensure that the molar ratio of hydrogen to nitrogen in the synthesis gas sent to the ammonia production unit is maintained at the stoichiometric ratio required for ammonia production.

[0064] Preferably, the installation includes a cryogenic purification unit connected to the synthesis gas discharge line L1.

[0065] Preferably, the carbon dioxide separation unit includes an amine purification unit.

[0066] Brief description of the drawings

[0067] The drawings are presented for a better understanding of the invention, however, it will be obvious to a person skilled in the art that the disclosed invention is not limited to the embodiment shown in them.

[0068] Fig. 1-2 show block diagrams of the best embodiments of the invention.

[0069] The best embodiment of the invention

[0070] The described embodiments are provided for illustrative purposes only. Those skilled in the art will readily recognize that other embodiments are possible without changing the essence of the invention.

[0071] Example 1

[0072] In Fig. 1, hydrogen-containing gas is fed into compression and desulfurization unit 1 via line 100.

[0073] Hydrogen-containing gas (HCG) is a gas with a high hydrogen content (10% or more) that is formed in various industrial processes, particularly through the dehydrogenation of hydrocarbons. Examples of such processes include: pyrolysis of the ethanepropane fraction at a gas processing plant, pyrolysis of the gasoline or naphtha fraction in oil refining processes, aromatization (catalytic reforming) of the gasoline or naphtha fraction in oil refining processes, etc.

[0074] During pyrolysis the following reaction occurs:

[0075] SgpN4p+2 - ShS2N4 + Ng

[0076] During the aromatization process (catalytic reforming), the following reaction occurs:

[0077] СгпНгп+г Снгп-б + 4Нг In addition to hydrogen, VSH also contains methane and, in some cases, impurity amounts of hydrocarbons Сг+.

[0078] Next, the hydrogen-containing gas is fed to the pre-reforming unit 2 via line 102, where steam from the fired heater (not shown) is also fed via line 200. The resulting stream of partially converted gas is fed via line 203 to the autothermal reforming (ATR) unit 3, where air is also fed via line 300. The resulting converted gas is fed via line 304 to the carbon monoxide conversion unit 4, where the carbon monoxide is converted into carbon dioxide. The gas obtained in unit 4 is fed via line 405 to the amine purification unit 5, the carbon dioxide from unit 5 is removed via line 510 (L2) as a finished product, and can also be sent to the urea production unit 10. The synthesis gas purified from carbon dioxide is fed via line 506 (L1) to the methanation and compression unit 6. Next, gas from block 6 enters ammonia synthesis block 7 via line 607.From the ammonia synthesis circuit, a purge gas stream is removed via line 708, which is diverted for combustion in the fire heater via line 708. From the ammonia synthesis unit 7, a product ammonia stream is removed via line 710, which can be sent to the consumer or to the urea synthesis unit 10.

[0079] In the case where the final product is urea, the resulting carbon dioxide and ammonia are fed to the urea production unit 10 via lines 510 and 710, respectively. For optimal performance of the urea synthesis stages, ammonia and carbon dioxide should be fed to the urea synthesis unit 10 in a molar ratio approaching the stoichiometric ratio, namely -2:1. However, it is well known that the carbon dioxide released from the reformed gas is obtained in insufficient quantities relative to ammonia. The missing amount of carbon dioxide is obtained from the flue gases of hydrocarbon fraction dehydrogenation furnaces (not shown) - in particular, pyrolysis furnaces and aromatization furnaces (catalytic reforming).

[0080] Lines 510 and 710 are equipped with carbon dioxide and ammonia measuring devices 12 and 13, respectively. Signals from the measuring devices are sent to the control unit, where the missing amount of carbon dioxide is calculated. Carbon dioxide separated from the flue gases enters the urea production unit 10 via line HO (L3), equipped with regulator R2, the signal to which comes from the control unit. Example 2

[0081] Fig. 2 shows another preferred embodiment of the invention.

[0082] Hydrogen-containing gas is fed to compression and desulfurization unit 1 via line 100. The gas is then fed via line 203 to ATR unit 3, which also receives steam from the fired heater (not shown) via line 200 and air via line 300.

[0083] The resulting converted gas is fed via line 304 to carbon monoxide conversion unit 4, where carbon monoxide is converted to carbon dioxide. The gas obtained in unit 4 is fed via line 405 to amine purification unit 5, carbon dioxide from unit 5 is removed via line 510 (L2) as a finished product and can also be sent to urea production unit 10. The synthesis gas, purified from carbon dioxide, is fed via line 506 (L1) to methanation and compression unit 6. Next, the gas from unit 6 is fed via line 607 to ammonia synthesis unit 7. From ammonia synthesis unit 7, a product ammonia stream is removed via line 710, which can be sent to the consumer or to urea synthesis unit 10.

[0084] In the case where the final product is urea, the resulting carbon dioxide and ammonia are fed to the urea production unit 10 via lines 510 and 710, respectively. For optimal performance of the urea synthesis stages, ammonia and carbon dioxide should be fed to the urea synthesis unit 10 in a molar ratio approaching the stoichiometric ratio, namely -2:1. However, it is well known that the carbon dioxide released from the reformed gas is obtained in insufficient quantities relative to ammonia. The missing amount of carbon dioxide is obtained from the flue gases of hydrocarbon fraction dehydrogenation furnaces (not shown) - in particular, pyrolysis furnaces and aromatization furnaces (catalytic reforming).

[0085] Lines 510 and 710 are equipped with carbon dioxide and ammonia measuring devices 12 and 13, respectively. Signals from the measuring devices are sent to the control unit, where the missing amount of carbon dioxide is calculated. Carbon dioxide separated from the flue gases enters the urea production unit 10 via line HO (L3), equipped with regulator R2, which receives a signal from the control unit.

[0086] Air is supplied to the ATR unit 3 via line 300 in such a quantity that oxygen oxidizes the hydrocarbons remaining in the hydrogen sulfide gas to carbon oxides, with a residual content in the gas not exceeding 1 vol.%. Nitrogen is obviously supplied to the system along with atmospheric oxygen. For optimal performance of the ammonia production process, hydrogen and nitrogen should be supplied to unit 7 via line 607 in a ratio tending to the stoichiometric ratio, namely 3:1. In the case of a high hydrocarbon content in the hydrogen sulfide gas entering the ATR unit, an excess amount of air is supplied via line 300 in order to maximize the oxidation of hydrocarbons: as a result, a greater amount of nitrogen is introduced into the system than is necessary to maintain the stoichiometry of the ammonia production reaction in the synthesis loop.

[0087] A purge gas stream is withdrawn from the ammonia synthesis circuit via line 708 and fed to unit 8 for separating ammonia from purge gases. The liquid ammonia obtained in unit 8 is returned to ammonia synthesis unit 7 via line 807.

[0088] The purge gas flow enters the hydrogen recovery unit 9, the hydrogen flow is removed via line 906 (L4), and the waste gas is removed via line 900 for combustion in the combustion heater (not shown).

[0089] Line 506 is equipped with a measuring device II for measuring the amount of hydrogen and nitrogen in the flow. The signal from measuring device II is fed to the control unit, where the required amount of hydrogen is calculated (to achieve a hydrogen to nitrogen ratio of 3:1). The signal from the control unit is then sent to regulator R1, and the required amount of hydrogen, extracted from the purge gas, is sent to unit 6 for the compression stage.

[0090] It will be obvious to the skilled person that an alternative way to achieve a hydrogen to nitrogen ratio of 3:1 is to cryogenically clean the gas in line 506 in the cryogenic cleaning unit and then feed the resulting synthesis gas to the ammonia synthesis unit 7.

[0091] Prototype

[0092] Fig. 3 shows a method for producing ammonia according to the prototype.

[0093] The hydrogen gas enters compression and desulfurization unit 1 via line 100. Next, the gas enters the PSA unit 12 via line 112, where hydrogen is recovered and sent via line 213 to compression unit 13. Waste gas, containing a large amount of methane, is sent via line 120 for combustion. Nitrogen obtained in unit 15 (the air separation unit) is also fed to compression unit 13. The resulting gas enters the ammonia synthesis unit via line 134. The resulting ammonia is sent via line 710 to urea production unit 10, where carbon dioxide is also fed via line 110.

[0094] Tables 1-2 below show the experimental results. Table 1. Compositions of the VSH and its sources.

[0095] Table 2. Parameters for the implementation of ammonia and urea production processes.

[0096] As can be seen from Table 2, the ammonia yield in Example 2 was 4917.21 kmol / h, while in the prototype, the ammonia yield was 3145.94 kmol / h. This means that the efficiency of the proposed ammonia production method is 57.2% higher than that of the prototype. Furthermore, the residual content of unconverted hydrocarbons in Example 2 was 0.76%, while in the prototype, all 15% of the residual methane was sent for combustion.

[0097] Thus, the proposed group of inventions made it possible to ensure

[0098] - increasing the energy efficiency and environmental friendliness of the technology for obtaining ammonia from by-products of oil and gas processing while reducing metal consumption, specific energy consumption, specific fuel gas consumption, and with a residual content of unconverted hydrocarbons after steam-air reforming not exceeding 1 vol.%

[0099] - no need to use a metal-intensive air separation unit and a metal-intensive primary reforming furnace that consumes a large amount of fuel gas;

[0100] - improving the environmental friendliness of the technology by using carbon dioxide from flue gases for the synthesis of urea;

[0101] - the possibility of flexible regulation of the hydrogen content in ammonia synthesis gas;

[0102] - the possibility of obtaining urea from flexibly controlled quantities of ammonia and carbon dioxide,

[0103] - increase in the productivity of ammonia production technology by 57.2%,

[0104] - specific fuel gas consumption for combustion not exceeding 100 Nm 3 per ton of ammonia.

Claims

Invention formula 1. A method for producing ammonia, comprising a) a stage of steam-air reforming of hydrogen-containing gas to obtain converted gas; b) a stage of converting carbon monoxide and separating carbon dioxide from the converted gas to obtain synthesis gas; c) a stage of obtaining ammonia from the synthesis gas obtained in stage b), wherein the hydrogen-containing gas fed to stage a) is a product of hydrocarbon dehydrogenation processes at oil or gas processing plants.

2. The method according to item 1, characterized in that the dehydrogenation of hydrocarbons at oil or gas processing plants includes the pyrolysis of the ethane-propane fraction and / or the pyrolysis of the gasoline fraction and / or the pyrolysis of the ligroin fraction (naphtha) and / or the catalytic reforming of the gasoline fraction and / or the catalytic reforming of the ligroin fraction (naphtha).

3. The method according to claim 1, characterized in that during the process of dehydrogenation of hydrocarbons, CO2 is separated from the flue gases leaving the furnaces of the dehydrogenation processes.

4. The method according to item 2, characterized in that CO2 is separated from flue gases leaving pyrolysis furnaces or catalytic reforming furnaces.

5. The method according to item 3 or 4, characterized in that the ammonia obtained in step c) together with the CO2 obtained in step b) and separated from the flue gas are sent to the synthesis of urea.

6. The method according to item 5, characterized in that the amount of CO2 supplied for the synthesis of urea from flue gases is regulated depending on the amount of ammonia obtained in step c) and CO2 obtained in step b), so that the molar ratio of the amount of ammonia to the total amount of carbon dioxide tends to the stoichiometric ratio required for obtaining urea.

7. The method according to claim 1, characterized in that step c) includes removing purge gas from the ammonia synthesis circuit.

8. The method according to item 7, characterized in that the purge gas is directed to a hydrogen extraction unit.

9. The method according to item 8, characterized in that the hydrogen separated from the purge gas is added to the synthesis gas obtained in step b).

10. The method according to claim 9, characterized in that the amount of hydrogen added to the synthesis gas obtained in step b) is adjusted so that the ratio of hydrogen to nitrogen in the synthesis gas sent to step c) tends to the stoichiometric ratio required to obtain ammonia.

11. The method according to item 1, characterized in that at stage b) cryogenic purification of the obtained synthesis gas is carried out.

12. The method according to item 1, characterized in that stage b) of isolating carbon dioxide includes amine purification.

13. The method according to item 1, characterized in that at stage a) of steam-air reforming, hydrogen-containing gas is fed at a temperature of at least 650°C and a pressure of 2-5 MPa; air is fed at a temperature of 450-650°C and a pressure of 2-5 MPa; and converted gas is obtained at a temperature of 900-1050°C at a pressure of 2-5 MPa.

14. An ammonia production unit comprising a steam-air reforming unit connected to a hydrogen-containing gas supply line and a converted gas removal line; a carbon monoxide conversion and carbon dioxide extraction unit connected to the converted gas supply line, a synthesis gas removal line L1 and a carbon dioxide removal line L2; an ammonia production unit connected to the synthesis gas supply line and the ammonia removal line; wherein the hydrogen-containing gas supply line is configured to feed the product from a hydrocarbon dehydrogenation unit at oil or gas processing plants to the steam-air reforming unit.

15. The installation according to item 14, characterized in that the hydrocarbon dehydrogenation unit at oil or gas refining plants includes an ethane-propane fraction pyrolysis unit and / or a gasoline fraction pyrolysis unit and / or a ligroin fraction (naphtha) pyrolysis unit and / or a gasoline fraction catalytic reforming unit and / or a ligroin fraction (naphtha) catalytic reforming unit.

16. The installation according to item 14, characterized in that the hydrocarbon dehydrogenation unit includes a dehydrogenation process furnace designed with the possibility of isolating and removing a flow of carbon dioxide along line L3 from the flue gases generated in the dehydrogenation process furnace.

17. The installation according to paragraph 15, characterized in that the units for pyrolysis of the ethane-propane fraction and / or gasoline fraction and / or ligroin fraction include a pyrolysis furnace, and the units for catalytic reforming of the gasoline fraction and / or ligroin fraction include a catalytic reforming furnace, wherein the pyrolysis and / or catalytic reforming furnaces are designed with the possibility of isolating and removing a stream of carbon dioxide along line L3 from the flue gases formed in the pyrolysis and catalytic reforming furnaces.

18. The plant according to item 16 or item 17, characterized in that it includes a urea production unit connected to an ammonia supply line, a carbon dioxide supply line L2, and a carbon dioxide supply line L3.

19. The plant according to item 18, characterized in that the ammonia supply line, lines L2, L3 are equipped with volumetric flow rate control means designed in such a way as to control the amount of urea obtained and ensure maintenance of the molar ratio of the amount of ammonia to the total amount of carbon dioxide, tending to the stoichiometric ratio required for obtaining urea.

20. The installation according to item 14, characterized in that the ammonia production unit is designed with the possibility of removing the purge gas flow from the ammonia synthesis circuit.

21. The installation according to item 20, characterized in that it includes a unit for separating hydrogen from the purge gas, connected to the purge gas supply line, and the hydrogen removal line L4.

22. The installation according to item 21, characterized in that the synthesis gas discharge line L1 is connected to the hydrogen supply line L4.

23. The installation according to item 22, characterized in that lines LI, L4 are equipped with means for regulating the volumetric flow rate, designed in such a way as to ensure the maintenance of the molar ratio of hydrogen to nitrogen in the synthesis gas sent to the ammonia production unit, tending to the stoichiometric ratio required for the production of ammonia.

24. The installation according to item 14, characterized in that it includes a cryogenic purification unit connected to the synthesis gas discharge line L1.

25. The installation according to item 14, characterized in that the carbon dioxide extraction unit includes an amine purification unit.

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