Gas desulfurization process and system

Abstract

The invention relates to a gas desulfurization process and system, and belongs to the technical field of chemical engineering. The problems that in the existing gas desulfurization process, the desulfurization process is complex, and organic sulfur is difficult to remove are solved. According to the gas desulfurization process, mercaptan is removed from gas through the alkali washing unit, COS is removed through the organic sulfur hydrolysis unit, and H2S generated by the organic sulfur hydrolysis unit is absorbed through the absorption unit. According to the method, mercaptan and COS in the gas can be removed at the same time, and the method is simple in technological operation, high in adaptability and capable of being widely applied to the gas desulfurization process in oil refining, coal chemical industry, petrochemical industry and natural gas processing and production; through verification, the content of H2S in the purified gas obtained through treatment is smaller than 5 mg / m < 3 >, the content of COS is smaller than 5 mg / m < 3 >, and the total sulfur content is smaller than 20 mg / m < 3 >.

Description

Technical Field

[0001] The present invention belongs to the field of chemical technology, and specifically relates to a gas desulfurization process and system, and is particularly suitable for the gas desulfurization process in oil refining, coal chemical industry, petrochemical industry, and natural gas processing and production. Prior art

[0002] A large amount of gas is often produced during the oil processing process. These gas mainly comes from the secondary processing of crude oil, such as dry gas produced by catalytic cracking, delayed coking, hydrocracking and other devices, high and low pressure gas produced by atmospheric and vacuum devices, etc. Gas contains a high content of H2S, so if it is directly vented or burned through a torch, it will not only pollute the environment, but also cause waste of resources and increase safety hazards. Therefore, in refineries, gas is usually used as heating furnace fuel to achieve energy saving and consumption reduction and reduce environmental pollution. However, gas must be desulfurized before use, otherwise, on the one hand, the sulfur dioxide content in the flue gas of the heating furnace will exceed the standard, and on the other hand, the sulfide produced by combustion will cause corrosion of equipment pipelines, forming new safety hazards.

[0003] At present, the alcohol amine desulfurization process is usually used for gas desulfurization in my country. This process uses a weakly alkaline alcohol amine aqueous solution as an absorbent to absorb acid gases such as H2S and CO2 in the gas in the absorption tower, thereby achieving the purpose of gas desulfurization. After absorbing the acid gas, the amine liquid is heated and regenerated to desorb the absorbed acid gas, and then it is recycled. The alcohol amine desulfurization process can effectively remove H2S from the gas to less than 10ppm. After the desulfurized gas is fed into the heating furnace for combustion, the emission of sulfur dioxide in the flue gas can be significantly reduced.

[0004] In recent years, as people's environmental awareness has been increasing, my country's environmental protection laws and regulations have become increasingly stringent. In 2015, my country issued the "Petroleum Refining Industry Pollutant Emission Standard (GB31570-2015)", which stipulates that the emission concentration limit of sulfur dioxide in flue gas from heating furnaces is generally required to reach 100mg / Nm 3 Below, key areas are required to reach 50mg / Nm 3 Although the amine desulfurization method can effectively remove H2S from gas to below 10ppm, the total sulfur content is still relatively high due to the presence of a certain amount of COS and mercaptan in the gas. The total sulfur content in some gas is as high as thousands of mg / m 3, which makes it difficult for the heating furnace to meet the emission standards. In addition, with the development of oil refining technology and the increase in demand for ethylene, China has vigorously developed dry gas to ethylene projects, that is, using catalytic or coking dry gas with a high C2 component content to recover ethylene, propylene and other resources. Compared with conventional gas combustion processes, dry gas to ethylene projects can save more than 4 million tons of light oil products used for ethylene production each year, which can effectively save energy and have good social and economic benefits. However, because the total sulfur content in this type of gas is high, the recovered gas must be deeply desulfurized, otherwise these gases will enter the ethylene unit and cause catalyst poisoning, cold box system blockage, and equipment corrosion, which poses great safety risks. The gas deep desulfurization process is complex and requires high investment. Therefore, if a suitable process can be used to deeply desulfurize gas, the dry gas to ethylene process can be simplified and safety risks can be reduced. In summary, new environmental protection regulations and process technologies have put forward higher requirements for gas desulfurization processes.

[0005] Patent CN202881200U discloses a refinery gas desulfurization device, including an alkali preparation device, a solvent absorption unit and an alkali washing unit, which are connected by pipelines; the solvent absorption unit is connected to the gas input pipeline to be treated, the solvent input pipeline and the sulfur-containing solvent output pipeline; the alkali washing unit is connected to the alkali liquid input pipeline from the alkali preparation device, the treated gas output pipeline and the waste alkali liquid output pipeline through relevant pipelines. The device can effectively remove H2S and some mercaptans from the gas, but it cannot further remove COS with a high residual amount in the gas, so the sulfur content in the gas is still high, which cannot meet the latest environmental protection regulations and dry gas to ethylene requirements.

[0006] Patent CN115138177A discloses a process for desulfurization and decarbonization of dry gas, and the steps are as follows: S1: the gas is separated from liquid and solid impurities by a gravity separator and a filter separator and then sent to the bottom of an absorption tower; S2: the filtered gas is countercurrently contacted from bottom to top with a composite methyldiethanolamine solution from top to bottom in the absorption tower, and the composite methyldiethanolamine solution absorbs CO2 and H2S. This process method uses a composite methyldiethanolamine solution, so there is no problem of chemical degradation, thereby avoiding solution foaming and ensuring that the desulfurization effect can meet the requirements. However, the desulfurization principle of this process is still alcoholamine desulfurization, so the desulfurization accuracy cannot be improved, and there are still high sulfur compounds in the gas.

[0007] In view of this, in order to further reduce the sulfur content in gas, ensure that the heating furnace achieves standard emissions and provide high-quality raw materials for the dry gas to ethylene process, it is necessary to propose a new gas desulfurization process and system. Summary of the invention

[0008] The purpose of the present invention is to provide a gas desulfurization process and system to solve the problems of complex desulfurization process and difficulty in removing organic sulfur in the existing gas desulfurization process. The present invention can simultaneously remove mercaptans and COS in gas. The process operation is simple and has strong adaptability. It can be widely used in gas desulfurization processes in oil refining, coal chemical industry, petrochemical industry, and natural gas processing and production. The H2S content in the gas treated by the present invention is less than 5mg / m 3 , COS content is less than 5mg / m 3 , total sulfur less than 20mg / m 3 .

[0009] The technical solutions adopted by the present invention to achieve the above-mentioned purpose are as follows.

[0010] The present invention provides a gas desulfurization process, wherein the gas is firstly subjected to an alkali washing unit to remove mercaptan, then subjected to an organic sulfur hydrolysis unit to remove COS, and finally subjected to an absorption unit to absorb H2S generated by the organic sulfur hydrolysis unit to obtain purified gas.

[0011] Preferably, the alkali washing unit uses alkali solution to remove mercaptans in gas; more preferably, the alkali washing unit uses a fiber membrane alkali solution desulfurization process; and particularly preferably, the alkali solution is sodium hydroxide.

[0012] Preferably, the organic sulfur hydrolysis unit uses an organic sulfur hydrolysis catalyst to remove COS from gas, and the hydrolysis activity of the organic sulfur hydrolysis catalyst at 60°C is greater than 95%, and the hydrolysis activity at above 80°C is greater than 99.5%; more preferably, the organic sulfur hydrolysis catalyst is an LS-05 catalyst.

[0013] Preferably, the absorption unit uses amine liquid to absorb H2S produced by the organic sulfur hydrolysis unit; more preferably, the amine liquid includes one or more of N-methylcyclohexylamine, triethanolamine, diisopropanolamine, N-methyldiethanolamine, and tert-butyldiglycolamine, with a concentration of 30-60%; especially preferably, the amine liquid is MDEA amine liquid.

[0014] Preferably, the gas desulfurization process comprises the following steps:

[0015] Step 1: After the gas is separated by the gas buffer tank, it is condensed by the first condenser, and then enters the fiber membrane desulfurizer to be mixed with alkali solution to remove mercaptan. After the mercaptan is removed, the gas is washed by water in the washing tank to remove the entrained alkali solution. After washing, the gas enters the organic sulfur hydrolysis unit;

[0016] Step 2: The washed gas is preheated in the first preheater and then enters the hydrolysis reactor, where COS hydrolysis reaction occurs under the action of the organic sulfur hydrolysis catalyst to generate gas containing H2S and CO2, which enters the absorption unit;

[0017] Step 3: After condensation and cooling in the second condenser, the gas containing H2S and CO2 enters the bottom of the absorption tower and countercurrently contacts with the amine liquid entering from the top of the absorption tower. The H2S in the gas containing H2S and CO2 is absorbed by the amine liquid to form rich amine liquid, and purified gas is obtained at the top of the absorption tower.

[0018] More preferably, in step 1, the concentration of mercaptans in the gas entering the gas buffer tank is less than 2000 mg / m 3 .

[0019] More preferably, in step 1, the temperature of the gas after condensation by the first condenser is controlled at 30-40°C.

[0020] More preferably, in step 1, the temperature of the fiber membrane desulfurizer is controlled at 30-50°C, and particularly preferably, 35-45°C.

[0021] More preferably, in step 1, the volume ratio of the gas entering the fiber membrane desulfurizer to the alkali solution is (10-40):1, and particularly preferably, (15-25):1.

[0022] More preferably, in step 1, the concentration of the alkali solution is controlled at 5-15%, and particularly preferably, 7-12%.

[0023] More preferably, in step 1, the operating temperature of the water washing tank is controlled at 30-50°C, and particularly preferably, 40-50°C.

[0024] More preferably, in step 1, the concentration of mercaptans in the gas after water washing is less than 10 mg / m 3 .

[0025] More preferably, in step one, the washing water in the washing tank is circulated by a washing water circulation pump.

[0026] More preferably, in step 2, the concentration of COS in the gas after water washing is less than 1000 mg / m 3 .

[0027] More preferably, in step 2, the temperature of the preheated washed gas is controlled at 65-125°C; particularly preferably, 85-105°C.

[0028] More preferably, in step 2, the bed temperature of the hydrolysis reactor is controlled at 60°C to 120°C; particularly preferably, 80°C to 100°C.

[0029] More preferably, in step three, the temperature of the gas containing H2S and CO2 after condensation and cooling by the second condenser is controlled at 30°C to 50°C.

[0030] More preferably, in step three, the temperature of the absorption tower is controlled at 30°C to 45°C; particularly preferably, 35 to 40°C.

[0031] More preferably, in step 3, the H2S content in the purified gas is less than 5 mg / m 3 , COS content is less than 5mg / m 3 , total sulfur less than 20mg / m 3 .

[0032] More preferably, in step three, the purified gas is introduced from the top of the absorption tower into the gas network or into the dry gas to ethylene unit, and the H2S produced after the rich amine liquid is regenerated is sent to the sulfur recovery unit for recycling.

[0033] The present invention also provides a gas desulfurization system used in the above-mentioned gas desulfurization process, comprising an alkali washing unit, an organic sulfur hydrolysis unit and an absorption unit connected in sequence, the alkali washing unit is used to remove mercaptans in the gas, the organic sulfur hydrolysis unit is used to remove COS in the gas, and the absorption unit is used to recover H2S produced by the organic sulfur hydrolysis unit.

[0034] Preferably, the alkali washing unit comprises a gas buffer tank, a first condenser, a fiber membrane desulfurizer, an alkali liquid tank, an alkali liquid circulation pump, a water washing tank and a water washing water circulation pump; wherein, the inlet of the gas buffer tank is connected to the gas inlet pipeline; the gas outlet of the gas buffer tank is connected to the shell side inlet of the first condenser through a pipeline; the shell side outlet of the first condenser is connected to the top inlet of the fiber membrane desulfurizer through a pipeline; the bottom outlet of the fiber membrane desulfurizer is connected to the inlet of the alkali liquid tank; the top outlet of the alkali liquid tank is connected to the inlet of the water washing tank through a pipeline; the bottom outlet of the alkali liquid tank is connected to the inlet of the alkali liquid circulation pump through a pipeline; the outlet of the alkali liquid circulation pump is connected to the side inlet of the fiber membrane desulfurizer through a pipeline; the top outlet of the water washing tank is connected to the inlet of the first preheater of the organic sulfur hydrolysis unit through a pipeline; the bottom outlet of the water washing tank is connected to the inlet of the water washing water circulation pump through a pipeline; the outlet of the water washing water circulation pump is connected to the side inlet of the water washing tank through a pipeline;

[0035] The organic sulfur hydrolysis unit comprises a first preheater and a hydrolysis reactor; wherein the outlet of the first preheater is connected to the inlet of the hydrolysis reactor through a pipeline; the outlet of the hydrolysis reactor is connected to the shell side inlet of the second condenser of the absorption unit through a pipeline;

[0036] The absorption unit comprises a second condenser and an absorption tower; wherein the shell side outlet of the second condenser is connected to the bottom inlet of the absorption tower through a pipeline; a purified gas outlet is provided at the top of the absorption tower; a lean amine liquid inlet is provided at the upper part of the absorption tower; and a rich amine liquid outlet is provided at the bottom of the absorption tower.

[0037] The gas desulfurization process and system provided by the present invention can realize gas desulfurization, and is suitable for gas desulfurization and refining in oil refining, coal chemical industry, petrochemical industry, and natural gas processing and production. Compared with the existing technology, it has the following positive effects:

[0038] 1. The gas desulfurization process and system provided by the present invention can solve the problem of high sulfur content in gas and realize fine desulfurization of gas, and the process is simple, the number of reactors is small, and the device investment is small.

[0039] 2. The gas desulfurization process and system provided by the present invention adopts a fiber membrane process to remove mercaptans, which can remove mercaptans in gas to 10 mg / m 3 the following.

[0040] 3. The gas desulfurization process and system provided by the present invention can achieve efficient removal of COS in gas at a relatively low temperature by using an organic sulfur hydrolysis catalyst, with low energy consumption, simple process and no need for complex catalyst grading.

[0041] 4. The gas desulfurization process and system provided by the present invention use amine liquid to absorb H2S at the end, and the regenerated H2S can be further recovered as sulfur.

[0042] 5. The gas desulfurization process and system provided by the present invention are simple to operate, highly adaptable, safe and environmentally friendly, and do not produce secondary pollution.

[0043] 6. The H2S content in the purified gas treated by the gas desulfurization process and system provided by the present invention is less than 5 mg / m 3 , COS content is less than 5mg / m 3 , total sulfur less than 10mg / m 3 , which can effectively ensure that the heating furnace achieves standard emissions and provide high-quality raw materials for the dry gas to ethylene process. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solution of the present invention, the drawings required for use in the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0045] Figure 1 It is a structural schematic diagram of the gas desulfurization system of the present invention;

[0046] In the figure, 1. gas buffer tank; 2. first condenser; 3. fiber membrane desulfurizer; 4. alkali liquid tank; 5. alkali liquid circulation pump; 6. water washing tank; 7. water washing water circulation pump; 8. first preheater; 9. hydrolysis reactor; 10. second condenser; 11. absorption tower. DETAILED DESCRIPTION

[0047] In order to further understand the present invention, preferred embodiments of the present invention are described below. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0048] The gas desulfurization process of the present invention comprises the following steps: firstly removing mercaptan from the gas through an alkali washing unit, then removing COS through an organic sulfur hydrolysis unit, and finally absorbing H2S generated by the organic sulfur hydrolysis unit through an absorption unit. The process of the present invention can realize dual treatment of mercaptan and COS in the gas, and can further recover the generated H2S, that is, while reducing the sulfur content in the gas, sulfur resources can also be recovered without secondary pollution. The H2S content in the gas treated by the process of the present invention is less than 5mg / m 3 , COS content is less than 5mg / m 3 , total sulfur less than 20mg / m 3 , which can effectively ensure that the heating furnace achieves standard emissions and provide high-quality raw materials for the dry gas to ethylene process.

[0049] The gas desulfurization process of the present invention preferably comprises the following steps:

[0050] Step 1: The gas is first washed with an alkaline washing unit to remove mercaptans

[0051] 1a) After the gas (with a high sulfur content) is separated from the liquid droplets in the gas buffer tank 1, it is condensed by circulating water in the first condenser 2 and then enters the fiber membrane desulfurizer 3. In the fiber membrane desulfurizer 3, the mercaptan in the gas reacts with the alkali solution (preferably NaOH) on the fiber membrane tow. The alkali solution is stored in the alkali solution tank 4 and transported to the fiber membrane desulfurizer 3 through the alkali solution circulation pump 5 to generate sodium mercaptide. The reaction is shown in formula (1);

[0052] RSH + NaOH = NaSR + H2O (1)

[0053] The temperature of the gas after condensation in the first condenser is controlled at 30-40°C; the temperature of the fiber membrane desulfurizer 3 is controlled at 30-50°C, preferably 35-45°C; the volume ratio of the gas to the alkali solution is (10-40):1, preferably (15-25):1; the concentration of the alkali solution is controlled at 5-15%, preferably 7-12%;

[0054] The fiber membrane desulfurizer 3 is a highly efficient mass transfer device, which provides a large reaction contact area in a small reaction space; its working principle is as follows: after the alkali solution enters the fiber membrane bundle from the top side of the fiber membrane desulfurizer 3, it contacts with the gas and removes the mercaptan in the process of flowing downward along the surface of the fiber membrane bundle; during the reaction process, due to the large number of fiber membrane bundles, the mass transfer area is greatly increased and the mass transfer distance is reduced, thereby greatly improving the mass transfer efficiency and strengthening the chemical reaction between the sulfide and the alkali solution on the liquid membrane, so that the mercaptan in the gas can be effectively removed;

[0055] Preferably, the alkali solution is internally circulated under the action of the alkali solution circulation pump 5; after a certain reaction time, more sodium mercaptide is accumulated in the alkali solution, and the alkali solution needs to be regenerated. The alkali solution regeneration refers to sending the alkali solution containing sodium mercaptide to the alkali solution regeneration unit for air oxidation to generate disulfide and NaOH. The reaction is shown in formula (2), wherein the disulfide is removed by a subsequent extraction process, and the regenerated NaOH is recycled;

[0056] 4NaSR + O2 + 2H2O = 2RSSR + 4NaOH (2)

[0057] 1b) After the mercaptan is removed, the gas enters the water washing tank 6 for water washing to remove the alkali solution carried by the gas. The concentration of mercaptan in the gas after water washing is less than 10 mg / m 3 ;

[0058] The washing water can be circulated by the washing water circulation pump 7; the operating temperature of the washing tank 6 is 30-50°C, preferably 40-50°C;

[0059] Step 2: After being preheated in the first preheater 8, the washed gas enters the hydrolysis reactor 9. Under the action of the organic sulfur hydrolysis catalyst in the hydrolysis reactor 9, COS hydrolysis reaction occurs to generate gas containing H2S and CO2. The COS content in the gas containing H2S and CO2 is less than 5 mg / m 3 , the reaction formula is shown in formula (3), the gas containing H2S and CO2 enters the absorption unit from the bottom outlet of the hydrolysis reactor 9;

[0060] COS + H2O = CO2 + H2S (3)

[0061] The temperature of the washed gas after preheating in the first preheater 8 is controlled to 65-125°C, preferably 85-105°C; the bed temperature of the hydrolysis reactor 9 is controlled to 60-120°C, preferably 80-100°C;

[0062] The hydrolysis reactor 9 is filled with an organic sulfur hydrolysis catalyst having good low temperature activity. The organic sulfur hydrolysis catalyst is preferably the LS-05 hydrolysis catalyst developed by the Research Institute of Sinopec Qilu Branch. The LS-05 catalyst is an alumina-based organic sulfur hydrolysis catalyst, which has high catalytic activity for the hydrolysis reaction of organic sulfides. The catalyst has a slow hydrolysis deactivation rate and can maintain a relatively stable organic sulfur hydrolysis activity throughout the entire service life.

[0063] The hydrolysis reactor 9 converts COS, which is difficult to remove, into H2S, which is easy to remove, through hydrolysis. There is no need to inject water into the hydrolysis reactor 9, because the water carried by the gas after being washed by the water washing tank 6 of the alkali washing unit can fully meet the reaction requirements.

[0064] Step 3: The gas containing H2S and CO2 is cooled by the second condenser 10 and enters the bottom of the absorption tower 11, and is countercurrently contacted with the liquid from the upper liquid inlet of the absorption tower 11 to remove the H2S therein; the purified gas is introduced into the gas pipeline network or the dry gas ethylene production device from the top of the absorption tower 11, and the rich amine liquid enters the regeneration tower from the bottom of the absorption tower 11 for regeneration, and the regenerated gas is sent to the sulfur recovery device to further recover sulfur;

[0065] The temperature of the gas containing H2S and CO2 after condensation and cooling by the second condenser 10 is controlled at 30°C to 50°C; the amine liquid is used as a liquid phase desulfurizer, the main components of which are one or more of N-methylcyclohexylamine, triethanolamine, diisopropanolamine, N-methyldiethanolamine, and tert-butyl diglycolamine, the solvent is water, and the concentration is 30-60%; the amine liquid preferably includes N-methyldiethanolamine (MDEA); the temperature of the absorption tower 11 is controlled at 30°C to 45°C, preferably 35-40°C; the H2S content in the purified gas is less than 5mg / m 3 , COS content is less than 5mg / m 3 , total sulfur less than 20mg / m 3 .

[0066] The gas desulfurization system used in the gas desulfurization process of the present invention comprises an alkali washing unit, an organic sulfur hydrolysis unit and an absorption unit connected in sequence. The alkali washing unit is used to remove mercaptans in the gas, the organic sulfur hydrolysis unit is used to remove COS in the gas, and the absorption unit is used to recover H2S produced by the organic sulfur hydrolysis unit.

[0067] like Figure 1As shown, in the gas desulfurization system of the present invention, the alkali washing unit comprises a gas buffer tank 1, a first condenser 2, a fiber membrane desulfurizer 3, an alkali liquid tank 4, an alkali liquid circulation pump 5, a water washing tank 6 and a water washing water circulation pump 7; wherein, the inlet of the gas buffer tank 1 is connected to the gas inlet pipeline; the gas outlet of the gas buffer tank 1 is connected to the shell side inlet of the first condenser 2 through a pipeline; the shell side outlet of the first condenser 2 is connected to the top inlet of the fiber membrane desulfurizer 3 through a pipeline; the bottom outlet of the fiber membrane desulfurizer 3 is connected to the bottom outlet of the alkali liquid tank 4 The top outlet of the alkali liquid tank 4 is connected to the inlet of the water washing tank 6 through a pipeline; the bottom outlet of the alkali liquid tank 4 is connected to the inlet of the alkali liquid circulation pump 5 through a pipeline; the outlet of the alkali liquid circulation pump 5 is connected to the side inlet of the fiber membrane desulfurizer 3 through a pipeline; the top outlet of the water washing tank 6 is connected to the inlet of the first preheater 8 of the organic sulfur hydrolysis unit through a pipeline; the bottom outlet of the water washing tank 6 is connected to the inlet of the water washing water circulation pump 7 through a pipeline; the outlet of the water washing water circulation pump 7 is connected to the side inlet of the water washing tank 6 through a pipeline;

[0068] The organic sulfur hydrolysis unit comprises a first preheater 8 and a hydrolysis reactor 9; wherein the outlet of the first preheater 8 is connected to the inlet of the hydrolysis reactor 9 through a pipeline; the outlet of the hydrolysis reactor 9 is connected to the shell side inlet of the second condenser 10 of the absorption unit through a pipeline;

[0069] The absorption unit comprises a second condenser 10 and an absorption tower 11; wherein the shell side outlet of the second condenser 10 is connected to the bottom inlet of the absorption tower 11 through a pipeline; a purified gas outlet is provided at the top of the absorption tower 11; a lean amine liquid inlet is provided at the upper part of the absorption tower 11; and a rich amine liquid outlet is provided at the bottom of the absorption tower 11.

[0070] The terms used in the present invention generally have the meanings commonly understood by those of ordinary skill in the art, unless otherwise specified.

[0071] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below in conjunction with embodiments.

[0072] In the following examples, various processes and methods not described in detail are conventional methods known in the art. Unless otherwise specified, the materials, reagents, devices, instruments, equipment, etc. used in the following examples can be obtained from commercial sources.

[0073] Example 1

[0074] use Figure 1 The gas desulfurization system of the present invention is used to refine the gas of a refinery (COS content 35mg / m 3 , mercaptan content 106mg / m 3 ), the steps are as follows:

[0075] Step 1: After the gas is separated from the liquid droplets in the gas buffer tank 1, it is cooled to 35°C by circulating water through the first condenser 2, and then enters the fiber membrane desulfurizer 3 (reaction temperature 38°C, volume ratio 20:1). On the fiber membrane tow in the fiber membrane desulfurizer 3, the mercaptan in the gas reacts with the alkali solution (NaOH concentration 10%) to form sodium mercaptide, thereby removing the mercaptan. The alkali solution is stored in the alkali solution tank 4, and is circulated and used by the alkali solution circulation pump 5, and enters the fiber membrane desulfurizer 3 from the side.

[0076] The gas after mercaptan removal is washed by water washing tank 6 (water washing temperature 40°C) to remove the alkali solution carried by it; the washing water is circulated by the washing water circulation pump 7. The gas after water washing enters the subsequent organic sulfur hydrolysis unit. After the alkali washing unit treatment, the mercaptan content in the gas is 1.5mg / m 3 .

[0077] Step 2: The washed gas enters the first preheater 8 and is preheated to 95°C, and then enters the hydrolysis reactor 9. Under the action of the organic sulfur hydrolysis catalyst in the hydrolysis reactor 9, a COS hydrolysis reaction occurs, and the bed temperature of the hydrolysis reactor 9 is controlled at 90°C. The hydrolysis reactor 9 is filled with the LS-04 low-temperature organic sulfur hydrolysis catalyst developed by the Research Institute of Sinopec Qilu Branch. After removing COS, the gas enters the absorption unit from the bottom outlet of the hydrolysis reactor 9. After being treated by the organic sulfur hydrolysis unit, the COS content in the gas is less than 0.8 mg / m 3 .

[0078] Step 3: The gas after hydrolysis is cooled to 35°C by the second condenser 10 and then enters the bottom of the absorption tower 11, where it is countercurrently contacted with the lean amine liquid (the amine liquid component is MDEA, the concentration is 45%, and the absorption temperature is 38°C) from the upper liquid inlet of the absorption tower 11 to remove H2S therein. The purified gas is merged into the gas pipe network from the top of the absorption tower 11, and the rich amine liquid enters the regeneration tower from the bottom of the absorption tower 11 for regeneration and continued use, and the regenerated gas is sent to the sulfur recovery device to further recover sulfur.

[0079] The H2S content in the gas treated by the process of the present invention is 0.5 mg / m 3 , COS content is 0.8mg / m 3 , total sulfur is 3.2mg / m 3 .

[0080] Example 2

[0081] use Figure 1 The gas desulfurization system of the present invention is used to refine the gas of a refinery (COS content 86mg / m 3 , mercaptan content 296mg / m 3 ), the steps are as follows:

[0082] Step 1: After the gas is separated from the liquid droplets in the gas buffer tank 1, it is cooled to 40°C by circulating water through the first condenser 2, and then enters the fiber membrane desulfurizer 3 (reaction temperature 42°C, volume ratio 30:1). In the fiber membrane desulfurizer 3, the mercaptan in the gas reacts with the alkali solution (NaOH concentration 8%) on the fiber membrane tow to generate sodium mercaptide, thereby removing the mercaptan. The alkali solution is stored in the alkali solution tank 4, and is circulated and used by the alkali solution circulation pump 5, and enters the fiber membrane desulfurizer 3 from the side.

[0083] The gas after mercaptan removal is washed by water washing tank 6 (water washing temperature 38°C) to remove the alkali solution carried by it; the washing water is circulated by the washing water circulation pump 7. The gas after water washing enters the subsequent organic sulfur hydrolysis unit. After the alkali washing unit treatment, the mercaptan content in the gas is 2.2mg / m 3 .

[0084] Step 2: The washed gas enters the first preheater 8 and is preheated to 85°C, and then enters the hydrolysis reactor 9. Under the action of the organic sulfur hydrolysis catalyst in the hydrolysis reactor 9, a COS hydrolysis reaction occurs, and the bed temperature of the hydrolysis reactor 9 is controlled at 80°C. The hydrolysis reactor 9 is filled with the LS-04 low-temperature organic sulfur hydrolysis catalyst developed by the Research Institute of Sinopec Qilu Branch. After removing COS, the gas enters the absorption unit from the bottom outlet of the hydrolysis reactor 9. After being treated by the organic sulfur hydrolysis unit, the COS content in the gas is less than 1.2 mg / m 3 .

[0085] Step 3: The gas after hydrolysis is cooled to 40°C by the second condenser 10 and then enters the bottom of the absorption tower 11, where it is countercurrently contacted with the lean amine liquid (the amine liquid component is MDEA, the concentration is 40%, and the absorption temperature is 42°C) from the upper liquid inlet of the absorption tower 11 to remove H2S therein. The purified gas is merged into the gas pipe network from the top of the absorption tower 11, and the rich amine liquid enters the regeneration tower from the bottom of the absorption tower 11 for regeneration and continued use, and the regenerated gas is sent to the sulfur recovery device to further recover sulfur.

[0086] The H2S content in the gas treated by the process of the present invention is 1.0 mg / m 3 , COS content is 1.2mg / m 3 , total sulfur is 5.8mg / m 3 .

[0087] Example 3

[0088] use Figure 1 The gas desulfurization system of the present invention is used to refine the gas of a refinery (COS content 212mg / m 3 , mercaptan content 816mg / m 3), the steps are as follows:

[0089] Step 1: After the gas is separated from the liquid droplets in the gas buffer tank 1, it is cooled to 35°C by circulating water through the first condenser 2, and then enters the fiber membrane desulfurizer 3 (reaction temperature 38°C, volume ratio 10:1). The mercaptan in the gas reacts with the alkali solution (NaOH concentration 15%) on the fiber membrane tow in the fiber membrane desulfurizer 3 to form sodium mercaptide, thereby removing the mercaptan. The alkali solution is stored in the alkali solution tank 4, and is circulated and used by the alkali solution circulation pump 5, and enters the fiber membrane desulfurizer 3 from the side.

[0090] The gas after mercaptan removal is washed by water in the washing tank 6 (washing temperature 35°C) to remove the alkali solution carried by it; the washing water is circulated by the washing water circulation pump 7. The washed gas enters the subsequent organic sulfur hydrolysis unit. After the alkali washing unit treatment, the mercaptan content in the gas is 2.5mg / m 3 .

[0091] Step 2: The washed gas enters the first preheater 8 and is preheated to 125°C, and then enters the hydrolysis reactor 9. Under the action of the organic sulfur hydrolysis catalyst in the hydrolysis reactor 9, a COS hydrolysis reaction occurs, and the bed temperature of the hydrolysis reactor 9 is controlled at 120°C. The hydrolysis reactor 9 is filled with the LS-04 low-temperature organic sulfur hydrolysis catalyst developed by the Research Institute of Sinopec Qilu Branch. After removing COS, the gas enters the absorption unit from the bottom outlet of the hydrolysis reactor 9. After being treated by the organic sulfur hydrolysis unit, the COS content in the gas is less than 1.8 mg / m 3 .

[0092] Step 3: The gas after hydrolysis is cooled to 30°C by the second condenser 10 and then enters the bottom of the absorption tower 11, where it is countercurrently contacted with the lean amine liquid (the amine liquid component is MDEA, the concentration is 50%, and the absorption temperature is 33°C) from the upper liquid inlet of the absorption tower 11 to remove H2S therein. The purified gas is merged into the gas pipe network from the top of the absorption tower 11, and the rich amine liquid enters the regeneration tower from the bottom of the absorption tower 11 for regeneration and continued use, and the regenerated gas is sent to the sulfur recovery device to further recover sulfur.

[0093] The H2S content in the gas treated by the process of the present invention is 1.1 mg / m 3 , COS content is 1.8mg / m 3 , total sulfur is 8.6mg / m 3 .

[0094] Example 4

[0095] use Figure 1 The gas desulfurization system of the present invention is used to refine the gas of a refinery (COS content 56mg / m 3 , mercaptan content 178mg / m3 ), the steps are as follows:

[0096] Step 1: After the gas is separated from the liquid droplets in the gas buffer tank 1, it is cooled to 45°C by circulating water through the first condenser 2, and then enters the fiber membrane desulfurizer 3 (reaction temperature 48°C, volume ratio 50:1). In the fiber membrane desulfurizer 3, the mercaptan in the gas reacts with the alkali solution (NaOH concentration 5%) on the fiber membrane tow to generate sodium mercaptide, thereby removing the mercaptan. The alkali solution is stored in the alkali solution tank 4, and is circulated and used by the alkali solution circulation pump 5, and enters the fiber membrane desulfurizer 3 from the side.

[0097] The gas after mercaptan removal is washed by water washing tank 6 (water washing temperature 30°C) to remove the alkali solution carried by it; the washing water is circulated by the washing water circulation pump 7. The gas after water washing enters the subsequent organic sulfur hydrolysis unit. After the alkali washing unit treatment, the mercaptan content in the gas is 3.8mg / m 3 .

[0098] Step 2: The washed gas enters the first preheater 8 and is preheated to 65°C, and then enters the hydrolysis reactor 9. Under the action of the organic sulfur hydrolysis catalyst in the hydrolysis reactor 9, a COS hydrolysis reaction occurs, and the bed temperature of the hydrolysis reactor 9 is controlled at 60°C. The hydrolysis reactor 9 is filled with the LS-04 low-temperature organic sulfur hydrolysis catalyst developed by the Research Institute of Sinopec Qilu Branch. After removing COS, the gas enters the absorption unit from the bottom outlet of the hydrolysis reactor 9. After being treated by the organic sulfur hydrolysis unit, the COS content in the gas is less than 3.3 mg / m 3 .

[0099] Step 3: The gas after hydrolysis is cooled to 45°C by the second condenser 10 and then enters the bottom of the absorption tower 11, where it is countercurrently contacted with the lean amine liquid (the amine liquid component is MDEA, the concentration is 30%, and the absorption temperature is 45°C) from the upper liquid inlet of the absorption tower 11 to remove H2S therein. The purified gas is merged into the gas pipe network from the top of the absorption tower 11, and the rich amine liquid enters the regeneration tower from the bottom of the absorption tower 11 for regeneration and continued use, and the regenerated gas is sent to the sulfur recovery device to further recover sulfur.

[0100] The H2S content in the gas treated by the process of the present invention is 1.6 mg / m 3 , COS content is 3.3mg / m 3 , total sulfur is 12.6 mg / m 3 .

[0101] Example 5

[0102] use Figure 1 The gas desulfurization system of the present invention is used to refine the gas of a refinery (COS content 43mg / m 3, mercaptan content 178mg / m 3 ), the steps are as follows:

[0103] Step 1: After the gas is separated from the liquid droplets in the gas buffer tank 1, it is cooled to 33°C by circulating water through the first condenser 2, and then enters the fiber membrane desulfurizer 3 (reaction temperature 36°C, volume ratio 18:1). In the fiber membrane desulfurizer 3, the mercaptan in the gas reacts with the alkali solution (NaOH concentration 8%) on the fiber membrane tow to generate sodium mercaptide, thereby removing the mercaptan. The alkali solution is stored in the alkali solution tank 4, and is circulated and used by the alkali solution circulation pump 5, and enters the fiber membrane desulfurizer 3 from the side.

[0104] The gas after mercaptan removal is washed by water washing tank 6 (water washing temperature 42°C) to remove the alkali solution carried by it; the washing water is circulated by the washing water circulation pump 7. The gas after water washing enters the subsequent organic sulfur hydrolysis unit. After the alkali washing unit treatment, the mercaptan content in the gas is 1.8mg / m 3 .

[0105] Step 2: The washed gas enters the first preheater 8 and is preheated to 105°C, and then enters the hydrolysis reactor 9. Under the action of the organic sulfur hydrolysis catalyst in the hydrolysis reactor 9, a COS hydrolysis reaction occurs, and the bed temperature of the hydrolysis reactor 9 is controlled at 100°C. The hydrolysis reactor 9 is filled with the LS-04 low-temperature organic sulfur hydrolysis catalyst developed by the Research Institute of Sinopec Qilu Branch. After removing COS, the gas enters the absorption unit from the bottom outlet of the hydrolysis reactor 9. After being treated by the organic sulfur hydrolysis unit, the COS content in the gas is less than 0.6 mg / m 3 .

[0106] Step 3: The gas after hydrolysis is cooled to 35°C by the second condenser 10 and then enters the bottom of the absorption tower 11, where it is countercurrently contacted with the lean amine liquid (the amine liquid component is MDEA, the concentration is 38%, and the absorption temperature is 37°C) from the upper liquid inlet of the absorption tower 11 to remove H2S therein. The purified gas is merged into the gas pipe network from the top of the absorption tower 11, and the rich amine liquid enters the regeneration tower from the bottom of the absorption tower 11 for regeneration and continued use, and the regenerated gas is sent to the sulfur recovery device to further recover sulfur.

[0107] The H2S content in the gas treated by the process of the present invention is 0.6 mg / m 3 , COS content is 0.6mg / m 3 , total sulfur is 4.2mg / m 3 .

[0108] Example 6

[0109] use Figure 1 The gas desulfurization system of the present invention is used to refine the gas of a refinery (COS content 63mg / m3 , mercaptan content 156mg / m 3 ), the steps are as follows:

[0110] Step 1: After the gas is separated from the liquid droplets in the gas buffer tank 1, it is cooled to 40°C by circulating water through the first condenser 2, and then enters the fiber membrane desulfurizer 3 (reaction temperature 42°C, volume ratio 25:1). In the fiber membrane desulfurizer 3, the mercaptan in the gas reacts with the alkali solution (NaOH concentration 12%) on the fiber membrane tow to generate sodium mercaptide, thereby removing the mercaptan. The alkali solution is stored in the alkali solution tank 4, and is circulated and used by the alkali solution circulation pump 5, and enters the fiber membrane desulfurizer 3 from the side.

[0111] The gas after mercaptan removal is washed by water washing tank 6 (water washing temperature 45°C) to remove the alkali solution carried by it; the washing water is circulated by the washing water circulation pump 7. The gas after water washing enters the subsequent organic sulfur hydrolysis unit. After the alkali washing unit treatment, the mercaptan content in the gas is 2.5mg / m 3 .

[0112] Step 2: The washed gas enters the first preheater 8 and is preheated to 105°C, and then enters the hydrolysis reactor 9. Under the action of the organic sulfur hydrolysis catalyst in the hydrolysis reactor 9, a COS hydrolysis reaction occurs, and the bed temperature of the hydrolysis reactor 9 is controlled at 100°C. The hydrolysis reactor 9 is filled with the LS-04 low-temperature organic sulfur hydrolysis catalyst developed by the Research Institute of Sinopec Qilu Branch. After removing COS, the gas enters the absorption unit from the bottom outlet of the hydrolysis reactor 9. After being treated by the organic sulfur hydrolysis unit, the COS content in the gas is less than 1.6 mg / m 3 .

[0113] Step 3: The gas after hydrolysis is cooled to 40°C by the second condenser 10 and then enters the bottom of the absorption tower 11, where it is countercurrently contacted with the lean amine liquid (the amine liquid component is MDEA, the concentration is 42%, and the absorption temperature is 42°C) from the upper liquid inlet of the absorption tower 11 to remove H2S therein. The purified gas is merged into the gas pipe network from the top of the absorption tower 11, and the rich amine liquid enters the regeneration tower from the bottom of the absorption tower 11 for regeneration and continued use, and the regenerated gas is sent to the sulfur recovery device to further recover sulfur.

[0114] The H2S content in the gas treated by the process of the present invention is 0.6 mg / m 3 , COS content is 1.6mg / m 3 , total sulfur is 6.5mg / m 3 .

[0115] Comparative Example 1

[0116] A refinery uses alcohol amine desulfurization process to desulfurize gas with amine liquid. The COS content in the gas after desulfurization is 52mg / m 3, mercaptan content is 256mg / m 3 After the gas is burned as the heating furnace fuel gas, the SO2 emission of the heating furnace flue gas is 146mg / m 3 , it cannot meet the requirements of environmental protection regulations and needs to add subsequent flue gas desulfurization facilities, which has a complex process and huge investment.

[0117] Comparative Example 2

[0118] A refinery uses alcohol amine desulfurization process to desulfurize gas with amine liquid. The COS content in the gas after desulfurization is 38mg / m 3 , mercaptan content is 176mg / m 3 As a raw material for producing ethylene from dry gas, this gas requires a series of desulfurization measures due to its high sulfur content. In addition, due to the high sulfur content in the raw material, it causes a great degree of corrosion to the equipment.

[0119] Obviously, the above embodiments are merely examples for clear explanation, and are not intended to limit the embodiments. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. The obvious changes or modifications derived from them are still within the protection scope of the invention.

Claims

1. A gas desulfurization process, characterized in that: The gas is firstly passed through an alkaline washing unit to remove mercaptans, then passed through an organic sulfur hydrolysis unit to remove COS, and finally passed through an absorption unit to absorb the H2S produced by the organic sulfur hydrolysis unit to obtain purified gas.

2. The gas desulfurization process according to claim 1, characterized in that: The alkaline washing unit uses alkaline solution to remove mercaptans from gas; The organic sulfur hydrolysis unit uses an organic sulfur hydrolysis catalyst to remove COS from gas, and the hydrolysis activity of the organic sulfur hydrolysis catalyst at 60° C. is greater than 95%, and the hydrolysis activity at above 80° C. is greater than 99.5%; The absorption unit uses amine liquid to absorb H2S produced by the organic sulfur hydrolysis unit.

3. The gas desulfurization process according to claim 2, characterized in that: The alkali solution is sodium hydroxide; The organic sulfur hydrolysis catalyst is LS-05 hydrolysis catalyst; The amine solution includes one or more of N-methylcyclohexylamine, triethanolamine, diisopropanolamine, N-methyldiethanolamine, and tert-butyldiglycolamine, and the concentration is 30-60%.

4. The gas desulfurization process according to claim 2, characterized in that: The following steps are involved: Step 1: After the gas is separated in the gas buffer tank (1), it is condensed in the first condenser (2) and then enters the fiber membrane desulfurizer (3) to be mixed with alkali solution to remove mercaptan. After the mercaptan is removed, the gas is washed with water in the water washing tank (6) to remove the entrained alkali solution. After the washing, the gas enters the organic sulfur hydrolysis unit; Step 2: The washed gas is preheated in the first preheater (8) and then enters the hydrolysis reactor (9), where a COS hydrolysis reaction occurs under the action of an organic sulfur hydrolysis catalyst to generate gas containing H2S and CO2, which then enters the absorption unit; Step 3: After being condensed and cooled in the second condenser (10), the gas containing H2S and CO2 enters the bottom of the absorption tower (11) and is countercurrently contacted with the amine liquid entering from the upper part of the absorption tower (11). The H2S in the gas containing H2S and CO2 is absorbed by the amine liquid to form a rich amine liquid, and purified gas is obtained at the top of the absorption tower (11).

5. The gas desulfurization process according to claim 4, characterized in that: In step one, The concentration of mercaptan in the gas entering the gas buffer tank (1) is less than 2000 mg / m 3 ; The temperature of the gas after condensation by the first condenser (2) is controlled at 30-40°C; The temperature of the fiber membrane desulfurizer (3) is controlled at 30-50°C; The volume ratio of the gas to the alkali solution entering the fiber membrane desulfurizer (3) is (10-40):

1. The concentration of the alkali solution is controlled at 5-15%; The operating temperature of the water washing tank (6) is 30-50°C; The concentration of mercaptan in the gas after water washing is less than 10 mg / m 3 ; The washing water in the washing tank (6) is circulated through the washing water circulation pump (7).

6. The gas desulfurization process according to claim 4, characterized in that: In step 2, The concentration of COS in the gas after water washing is less than 1000 mg / m 3 ; The temperature of the preheated washed gas is controlled at 65-125°C; The bed temperature of the hydrolysis reactor (9) is controlled at 60°C to 120°C.

7. The gas desulfurization process according to claim 4, characterized in that: In step three, The temperature of the gas containing H2S and CO2 after condensation and cooling in the second condenser (10) is controlled at 30°C to 50°C; The temperature of the absorption tower (11) is controlled at 30°C to 45°C; The H2S content in the purified gas is less than 5 mg / m 3 , COS content is less than 5mg / m 3 , total sulfur less than 20mg / m 3 .

8. The gas desulfurization process according to claim 4, characterized in that: The purified gas is fed into the gas network or into the dry gas ethylene production unit from the top of the absorption tower (11), and the H2S produced after the rich amine liquid is regenerated is sent to the sulfur recovery unit for recycling.

9. The gas desulfurization system used in the gas desulfurization process according to any one of claims 1 to 8, characterized in that: It includes an alkali washing unit, an organic sulfur hydrolysis unit and an absorption unit which are connected in sequence. The alkali washing unit is used to remove mercaptans in the gas, the organic sulfur hydrolysis unit is used to remove COS in the gas, and the absorption unit is used to recover H2S produced by the organic sulfur hydrolysis unit.

10. The gas desulfurization system according to claim 9, characterized in that: The alkali washing unit comprises a gas buffer tank (1), a first condenser (2), a fiber membrane desulfurizer (3), an alkali liquid tank (4), an alkali liquid circulation pump (5), a water washing tank (6) and a water washing water circulation pump (7); wherein the inlet of the gas buffer tank (1) is connected to the gas inlet pipeline; the gas outlet of the gas buffer tank (1) is connected to the shell side inlet of the first condenser (2) through a pipeline; the shell side outlet of the first condenser (2) is connected to the top inlet of the fiber membrane desulfurizer (3) through a pipeline; and the bottom outlet of the fiber membrane desulfurizer (3) is connected to the inlet of the alkali liquid tank (4); The top outlet of the alkali liquid tank (4) is connected to the inlet of the water washing tank (6) through a pipeline; the bottom outlet of the alkali liquid tank (4) is connected to the inlet of the alkali liquid circulation pump (5) through a pipeline; the outlet of the alkali liquid circulation pump (5) is connected to the side inlet of the fiber membrane desulfurizer (3) through a pipeline; the top outlet of the water washing tank (6) is connected to the inlet of the first preheater (8) of the organic sulfur hydrolysis unit through a pipeline; the bottom outlet of the water washing tank (6) is connected to the inlet of the water washing water circulation pump (7) through a pipeline; the outlet of the water washing water circulation pump (7) is connected to the side inlet of the water washing tank (6) through a pipeline; The organic sulfur hydrolysis unit comprises a first preheater (8) and a hydrolysis reactor (9); wherein the outlet of the first preheater (8) is connected to the inlet of the hydrolysis reactor (9) through a pipeline; and the outlet of the hydrolysis reactor (9) is connected to the shell side inlet of the second condenser (10) of the absorption unit through a pipeline; The absorption unit comprises a second condenser (10) and an absorption tower (11); wherein the shell side outlet of the second condenser (10) is connected to the bottom inlet of the absorption tower (11) through a pipeline; the top of the absorption tower (11) is provided with a purified gas outlet; the upper part of the absorption tower (11) is provided with a lean amine liquid inlet; and the bottom of the absorption tower (11) is provided with a rich amine liquid outlet.

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