Method and system for producing sodium hydrosulfide by using acid gas

Abstract

The invention relates to the technical field of petrochemical industry waste gas recycling, in particular to a method and system for producing sodium hydrosulfide through acid gas. The method comprises the following steps: reacting an acid gas with a first reaction mixed solution, a second reaction mixed solution and a third reaction mixed solution to sequentially obtain a first reaction alkali liquor, a first reaction purified gas, a second reaction alkali liquor, a second reaction purified gas, a third reaction alkali liquor and a third reaction purified gas; performing steam stripping evaporation on the first reaction alkali liquor to obtain a first product and steam stripping tail gas; judging whether ammonia absorption treatment is needed or not according to the ammonia content in the mixed gas of the third reaction purified gas and the steam stripping tail gas; if the volume fraction of ammonia in the mixed gas is larger than or equal to 5%, ammonia absorption treatment is conducted on the mixed gas, and a second product and exhaust gas are obtained respectively; according to the method, the resource utilization degree of the acid gas can be improved, the obtained sodium hydrosulfide is high in selectivity, and the whole method further has the advantages of being simple in process, flexible to operate and low in equipment and operation cost.

Description

Technical Field

[0001] The present application relates to the technical field of recovery and utilization of petrochemical waste gas, and particularly relates to a method and a system for producing sodium hydrosulfide by using acidic gas. Background Art

[0002] At present, there are mainly three commonly used sulfur-containing waste gas treatment technologies, namely secondary Claus combined with tail gas hydrogenation reduction and solvent absorption technology, wet sulfuric acid production technology (such as WSA process), and catalytic liquid phase oxidation technology (such as LO-CAT process); however, the above technologies either have long process flows and complex operations, or large investments and poor scale benefits, or there are defects that some acidic gases are difficult to treat; for small and medium-sized refineries, chemical plants, and oil and gas field treatment facilities, the treatment volume of sulfur-containing waste gas is relatively small, so there is an urgent need for a treatment process with low equipment and operation costs.

[0003] Using sulfur-containing waste gas to produce sodium hydrosulfide can combine inorganic chemical industry with environmental protection, and can greatly reduce the investment and operation costs of sulfur-containing waste gas treatment, which provides a practical new way to solve the problem of sulfur-containing waste gas pollution for enterprises with small treatment volumes of sulfur-containing waste gas. At present, the principle of amine liquid absorption-regeneration is used to separate hydrogen sulfide from carbon dioxide first (or called purification and purification of sulfide gas), and then the hydrogen sulfide separated from carbon dioxide reacts with sodium hydroxide to generate sodium hydrosulfide. However, the volume fraction of hydrogen sulfide in the tail gas of this process (excluding air) is as high as 22.30% - 66.81%, which cannot meet the discharge standards; in addition, this process will also cause excessive dilution of sodium hydrosulfide products, and the over-diluted sodium hydrosulfide products have no sales value and can only be treated as waste.

[0004] Therefore, it is necessary to provide a method and a system for producing sodium hydrosulfide by using acidic gas, which have the characteristics of high resource utilization degree, high selectivity of sodium hydrosulfide, simple process, flexible operation, and low equipment and operation costs. Summary of the Invention

[0005] The present application provides a method and a system for producing sodium hydrosulfide by using acidic gas, so as to solve the technical problems of poor resource utilization degree, poor selectivity of sodium hydrosulfide, complex process, and high production cost in the existing method for producing sodium hydrosulfide by using acidic gas.

[0006] In the first aspect, the present application provides a method for producing sodium hydrosulfide by using acidic gas, and the method includes:

[0007] Carrying out a first reaction on the acidic gas in a gradient countercurrent contact manner by using a first reaction mixture to absorb the sulfur-containing gas in the acidic gas, and respectively obtaining a first mixture and a first reaction purified gas;

[0008] Perform gas-liquid separation on the first mixture to obtain a first reaction caustic solution;

[0009] Perform stripping evaporation on a part of the first reaction caustic solution to obtain a first product and stripping tail gas respectively;

[0010] Mix the first reaction purified gas with a second reaction mixture and carry out a second reaction to obtain a second mixture;

[0011] Perform gas-liquid separation on the second mixture to obtain a second reaction caustic solution and a second reaction purified gas respectively;

[0012] Carry out a hydrogen sulfide removal reaction on the second reaction purified gas with a third reaction mixture to obtain a third mixture and a third reaction purified gas respectively, and then perform gas-liquid separation on the third mixture to obtain a third reaction caustic solution;

[0013] Mix the third reaction purified gas and the stripping tail gas to obtain a mixed gas;

[0014] Judge whether ammonia absorption treatment is required according to the ammonia content in the mixed gas;

[0015] If the volume fraction of ammonia in the mixed gas ≥ 5%, perform ammonia absorption treatment on the mixed gas to obtain a second product and exhaust gas respectively;

[0016] Output the first product to obtain a sodium hydrosulfide product;

[0017] Wherein, the first reaction mixture includes the other part of the first reaction caustic solution and a part of the second reaction caustic solution, the second reaction mixture includes the other part of the second reaction caustic solution and a second reaction prepared caustic solution, and the third reaction mixture includes the third reaction caustic solution and a third prepared caustic solution;

[0018] The second reaction prepared caustic solution and the third prepared caustic solution are respectively aqueous solutions of alkaline substances.

[0019] Optionally, the step of using the first reaction mixture to carry out a first reaction on the acidic gas in a gradient countercurrent contact manner to absorb the sulfur-containing gas in the acidic gas and obtain a first mixture and a first reaction purified gas, and then performing gas-liquid separation on the first mixture to obtain a first reaction caustic solution includes the steps:

[0020] Perform a first-stage reaction on the acidic gas with a first reaction first-stage mixture in a countercurrent contact manner to obtain a first reaction first-stage mixture and a first reaction first-stage purified gas respectively;

[0021] Perform gas-liquid separation on the first reaction first-stage mixture to obtain a first reaction first-stage caustic solution;

[0022] Increase the pressure of the first-stage reaction primary lye to obtain a first lye and a second lye respectively;

[0023] Use the first-stage reaction secondary mixed liquid to carry out a second-stage reaction on the first-stage reaction primary purified gas in a countercurrent contact manner to obtain a first-stage reaction secondary mixture and a first-stage reaction secondary purified gas respectively;

[0024] Carry out gas-liquid separation on the first-stage reaction secondary mixture to obtain a first-stage reaction secondary lye;

[0025] Increase the pressure and carry out a first cooling on the first-stage reaction secondary lye to obtain a third lye and a fourth lye respectively;

[0026] Use the first-stage reaction tertiary mixed liquid to carry out a third-stage reaction on the first-stage reaction secondary purified gas in a countercurrent contact manner to obtain a first-stage reaction tertiary mixture and a first-stage reaction purified gas respectively;

[0027] Carry out gas-liquid separation on the first-stage reaction tertiary mixture to obtain a first-stage reaction tertiary lye;

[0028] Increase the pressure and carry out a second cooling on the first-stage reaction tertiary lye to obtain a fifth lye and a sixth lye respectively;

[0029] Among them, the first-stage reaction lye includes the first-stage reaction primary lye, the first-stage reaction secondary lye and the first-stage reaction tertiary lye;

[0030] The first-stage reaction primary mixed liquid is a mixed liquid of the second lye and the third lye, the first-stage reaction secondary mixed liquid is a mixed liquid of the fourth lye and the fifth lye, and the first-stage reaction tertiary mixed liquid is a mixed liquid of the sixth lye and a part of the second-stage reaction lye.

[0031] Optionally, the temperature of the first-stage reaction is 50°C to 80°C, and the pressure of the first-stage reaction ≥ 0.10 MPa;

[0032] The temperature of the second-stage reaction is 45°C to 70°C, and the pressure of the second-stage reaction ≥ 0.09 MPa;

[0033] The temperature of the third-stage reaction is 40°C to 65°C, and the pressure of the third-stage reaction ≥ 0.08 MPa.

[0034] Optionally, after carrying out gas-liquid separation on the second mixture to obtain a second-stage reaction lye and a second-stage reaction purified gas respectively, the following steps are included:

[0035] Increase the pressure and carry out a third cooling on the second-stage reaction lye to obtain a seventh lye and an eighth lye respectively;

[0036] Among them, the seventh lye and the sixth lye form the first reaction three-stage mixed liquid after being mixed;

[0037] The eighth lye and the second reaction configured lye form the second reaction mixed liquid after being mixed.

[0038] Optionally, the third reaction mixed liquid is used to carry out a hydrogen sulfide removal reaction on the second reaction purified gas to obtain a third mixture and a third reaction purified gas respectively, and then the third mixture is subjected to gas-liquid separation to obtain a third reaction lye. After that, the steps include:

[0039] The third reaction lye is pressurized and fourth-cooled to obtain a ninth lye, a tenth lye and a third mixed product respectively. Among them,

[0040] The third mixed product includes an eleventh lye and / or a third product;

[0041] The ninth lye and the tenth lye are respectively mixed with the third configured lye to form the third reaction mixed liquid;

[0042] The sum of the flow rates of the eleventh lye and the third product is the same as the flow rate of the third reaction configured lye after the reaction.

[0043] In a second aspect, the present application provides a system for producing sodium hydrosulfide using acidic gas. The system is adapted to the method described in the first aspect. The system includes:

[0044] A reaction section, the reaction section includes a first reactor, a second reactor and a third reactor. The first reactor is provided with an air inlet to enable acidic gas to enter the system. The air outlet of the first reactor is communicated with the second reactor, and the air outlet of the second reactor is communicated with the third reactor;

[0045] A stripping evaporation tower, the liquid inlet of the stripping evaporation tower is communicated with the liquid outlet of the first reactor;

[0046] A reaction pump group, the reaction pump group includes a first reaction pump, a second reaction pump and a third reaction pump. The two ends of the first reaction pump are respectively communicated with the top and the bottom of the first reactor, the two ends of the second reaction pump are respectively communicated with the top and the bottom of the second reactor, and the two ends of the third reaction pump are respectively communicated with the top and the bottom of the third reactor;

[0047] A cooling section, the cooling section is arranged in the first reactor.

[0048] Optionally, the first reactor includes a first reaction column, a second reaction column, a third reaction column, and a first buffer tank; the first reaction column includes a first reaction section and a first connecting pipe, the second reaction column includes a second reaction section and a second connecting pipe, the third reaction column includes a third reaction section and a third connecting pipe, the first reaction column is connected to the first buffer tank through the first connecting pipe, the second reaction column is connected to the first buffer tank through the second connecting pipe, and the third reaction column is connected to the first buffer tank through the third connecting pipe;

[0049] A first partition and a second partition are provided in the first buffer tank to cooperate with the first connecting pipe, the second connecting pipe, and the third connecting pipe to form a first buffer zone, a second buffer zone, and a third buffer zone.

[0050] Optionally, the first reaction pump includes a first-stage reaction pump, a second-stage reaction pump, and a third-stage reaction pump; one end of the first-stage reaction pump is connected to the first buffer tank, and the other end of the first-stage reaction pump is respectively connected to the first reaction section and the stripping evaporation tower;

[0051] One end of the second-stage reaction pump is connected to the first buffer tank, and the other end of the second-stage reaction pump is respectively connected to the first reaction section and the second reaction section;

[0052] One end of the third-stage reaction pump is connected to the first buffer tank, and the other end of the third-stage reaction pump is respectively connected to the second reaction section and the third reaction section.

[0053] Optionally, the cooling section includes a first cooler, a second cooler, a third cooler, and a fourth cooler. The first cooler is provided at the discharge end of the second-stage reaction pump of the first reaction pump, the second cooler is provided at the discharge end of the third-stage reaction pump of the first reaction pump, the third cooler is provided at the discharge end of the second reaction pump, and the fourth cooler is provided at the discharge end of the third reaction pump.

[0054] Optionally, the second reactor includes a fourth reaction section, a fifth reaction section, a second buffer tank, and a valve group. The liquid discharge ends of the fourth reaction section and the fifth reaction section are connected to the second buffer tank, and the fourth reaction section and the fifth reaction section are respectively connected to the gas outlet of the first reactor; the fourth reaction section and the fifth reaction section are connected through the valve group to achieve series connection, parallel connection, or independent operation between the fourth reaction section and the fifth reaction section.

[0055] Optionally, the valve group includes a first valve, a second valve, a third valve, a fourth valve, a fifth valve, and a sixth valve. The tops of the fourth reaction section and the fifth reaction section are connected through the first valve and the second valve. The bottoms of the fourth reaction section and the fifth reaction section are connected through the fifth valve and the sixth valve. The fourth reaction section is connected to the bottom of the fifth reaction section through the third valve. The top of the fifth reaction section is connected to the bottom of the fourth reaction section through the third and fourth valves.

[0056] Optionally, the third reactor includes a sixth reaction section, a seventh reaction section, an eighth reaction section, and a third buffer tank. The gas outlet of the second reactor communicates with the bottom of the eighth reaction section. The liquid inlet end of the third reaction pump communicates with the bottom of the third buffer tank. The liquid outlet end of the third reaction pump is respectively arranged between the sixth reaction section and the seventh reaction section and between the seventh reaction section and the eighth reaction section.

[0057] Optionally, the system further includes:

[0058] An ammonia treatment unit, which includes an ammonia absorption tower, an ammonia rectification tower, and an ammonia water pump. The gas inlet end of the ammonia absorption tower communicates with the gas outlet of the stripping evaporation tower and the gas outlet of the third reactor respectively. The liquid outlet end of the ammonia absorption tower communicates with the liquid inlet end of the ammonia water pump. The liquid outlet end of the ammonia water pump communicates with the liquid inlet ends of the ammonia absorption tower and the ammonia rectification tower respectively.

[0059] Optionally, the ammonia absorption tower sequentially includes a first absorption section, a second absorption section, and an absorption liquid buffer tank from top to bottom. The liquid outlet end of the ammonia water pump is arranged between the first absorption section and the second absorption section. The gas outlet of the stripping evaporation tower communicates with the top of the absorption liquid buffer tank. The bottom of the absorption liquid buffer tank communicates with the liquid inlet end of the ammonia water pump.

[0060] Optionally, the ammonia rectification tower includes a condensation section, a first separation section, a second separation section, and a reboiler from top to bottom. The liquid outlet end of the ammonia water pump is arranged between the first separation section and the second separation section. The reboiler is arranged at the bottom of the ammonia rectification tower.

[0061] The above technical solutions provided by the embodiments of the present application have at least the following advantages compared with the prior art:

[0062] A method for producing sodium hydrosulfide using acidic gas provided by an embodiment of the present application first reacts the acidic gas in a gradient countercurrent contact manner with a first reaction mixture. This can not only extract hydrogen sulfide from the acidic gas but also strip and evaporate the oily components and ammonia impurities in the first reaction alkali solution, thereby obtaining stripping gas and sodium hydrosulfide products. Then, a second reaction mixture is used to further process the treated acidic gas, enabling the hydrogen sulfide in the acidic gas to react with sodium hydroxide to form sodium sulfide, and some sodium sulfide also reacts with hydrogen sulfide to form sodium hydrosulfide. Next, a third reaction mixture is used to further remove hydrogen sulfide from the treated acidic gas, causing the remaining sodium hydrosulfide in the acidic gas to mainly transform into sodium sulfide, thus enabling the hydrogen sulfide in the acidic gas to fully react. Finally, the necessity of ammonia absorption treatment is determined based on the ammonia content in the tail gas and stripping gas, thereby enabling the treatment and full utilization of ammonia impurities in the acidic gas. Moreover, the circulation quantity and temperature of the three reaction mixtures used in this method can also be adjusted according to the quality of the sodium hydrosulfide product and / or purified gas product. By using the method disclosed in the present application, the resource utilization degree of acidic gas can be improved, and the obtained sodium hydrosulfide product has good quality and high yield. At the same time, this method also has the characteristics of simple process, flexible operation, low equipment and operation costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] The accompanying drawings herein are incorporated into the specification and form a part of the specification, showing embodiments consistent with the present application and, together with the specification, used to explain the principles of the present application.

[0064] To more clearly illustrate the technical solutions in the embodiments of the present application or in the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0065] Figure 1 It is a schematic flow chart of a method for producing sodium hydrosulfide using acidic gas provided by an embodiment of the present application;

[0066] Figure 2 It is a detailed schematic flow chart of a method for producing sodium hydrosulfide using acidic gas provided by an embodiment of the present application;

[0067] Figure 3 For Figure 2 continuation;

[0068] Figure 4 It is a schematic structural diagram of a system for producing sodium hydrosulfide using acidic gas provided by an embodiment of the present application;

[0069] Among them, 11 - stripping evaporation tower, 111 - first stripping evaporation section, 112 - second stripping evaporation section, 12 - ammonia absorption tower, 121 - first absorption section, 122 - second absorption section, 123 - absorption liquid buffer tank, 13 - ammonia rectification tower, 131 - condensation section, 132 - first separation section, 133 - second separation section, 134 - reboiler, 21 - first reaction primary pump, 22 - first reaction secondary pump, 23 - first reaction tertiary pump, 24 - second reaction pump, 25 - third reaction pump, 26 - ammonia water pump, 31 - first reactor, 311 - first reaction column, 3111 - first reaction section, 3112 - first connecting pipe, 312 - second reaction column, 3121 - second reaction section, 3122 - second connecting pipe, 313 - third reaction column, 3131 - third reaction section, 3132 - third connecting pipe, 314 - first buffer tank, 3141 - first partition board, 3142 - second partition board, 32 - second reactor, 321 - fourth reaction section, 322 - fifth reaction section, 323 - second buffer tank, 324 - first valve, 325 - second valve, 326 - third valve, 327 - fourth valve, 328 - fifth valve, 329 - sixth valve, 33 - third reactor, 331 - sixth reaction section, 332 - seventh reaction section, 333 - eighth reaction section, 334 - third buffer tank, 41 - first cooler, 42 - second cooler, 43 - third cooler, 44 - fourth cooler. Detailed implementation manners

[0070] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Apparently, the described embodiments are some but not all of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the scope of protection of the present application.

[0071] Unless otherwise specifically stated, all kinds of raw materials, reagents, instruments and equipment used in the present application can be obtained through market purchase or can be prepared by existing methods.

[0072] Existing sodium hydrosulfide production devices generally use the principle of amine liquid absorption - regeneration to first separate hydrogen sulfide from carbon dioxide (or purify and refine hydrogen sulfide), and then react the hydrogen sulfide from which carbon dioxide has been separated with sodium hydroxide to produce sodium hydrosulfide; existing sodium hydrosulfide production devices only disclose methods for pre - treating carbon dioxide in acid gas, but do not disclose methods for treating and recovering other impurities such as ammonia in acid gas, nor do they disclose methods for flexibly adjusting the product indexes or specifications of sodium hydrosulfide, purified gas and ammonia products during the production process to meet different requirements.

[0073] The present application discloses a process method and system for producing sodium hydrosulfide using acidic gas, which can treat and recover ammonia in the acidic gas, and can also flexibly adjust the indicators or specifications of sodium hydrosulfide, purified gas and ammonia products during the production process to meet the indicator requirements of relevant standards or special regulations. For example, it can simultaneously output a liquid sodium hydrosulfide product with a mass fraction of 43% and a purified gas product with a hydrogen sulfide content of less than 20 mg / Nm 3 and an ammonia product with an ammonia mass fraction of not less than 20%.

[0074] As Figure 1 shown, an embodiment of the present application provides a method for producing sodium hydrosulfide using acidic gas, and the method includes:

[0075] S1. Using a first reaction mixture to carry out a first reaction on the acidic gas in a gradient countercurrent contact manner to absorb the sulfur-containing gas in the acidic gas, and respectively obtaining a first mixture and a first reaction purified gas, and then carrying out gas-liquid separation on the first mixture to obtain a first reaction alkali solution;

[0076] S2. Stripping and evaporating a part of the first reaction alkali solution to respectively obtain a first product and a stripping tail gas;

[0077] S3. Mixing the first reaction purified gas with a second reaction mixture and carrying out a second reaction to obtain a second mixture;

[0078] S4. Carrying out gas-liquid separation on the second mixture to respectively obtain a second reaction alkali solution and a second reaction purified gas;

[0079] S5. Using a third reaction mixture to carry out a hydrogen sulfide removal reaction on the second reaction purified gas to respectively obtain a third mixture and a third reaction purified gas, and then carrying out gas-liquid separation on the third mixture to obtain a third reaction alkali solution;

[0080] S6. Mixing the third reaction purified gas and the stripping tail gas to obtain a mixed gas;

[0081] S7. Judging whether ammonia absorption treatment is required according to the ammonia content in the mixed gas;

[0082] If the volume fraction of ammonia in the mixed gas ≥ 5%, then carry out ammonia absorption treatment on the mixed gas to respectively obtain a second product and an exhaust gas;

[0083] S8. Outputting the first product to obtain a sodium hydrosulfide product;

[0084] Among them, the first reaction mixture includes another part of the first reaction alkali solution and a part of the second reaction alkali solution, the second reaction mixture includes another part of the second reaction alkali solution and the second reaction preparation alkali solution, and the third reaction mixture includes the third reaction alkali solution and the third preparation alkali solution;

[0085] The second reaction preparation alkali solution and the third preparation alkali solution are respectively aqueous solutions of alkaline substances.

[0086] Such as Figure 2 And Figure 3 As shown, in some alternative embodiments, the first reaction mixture is used to carry out a first reaction on the acidic gas in a gradient countercurrent contact manner to absorb the sulfur-containing gas in the acidic gas, and a first mixture and a first reaction purified gas are respectively obtained. Then, the first mixture is subjected to gas-liquid separation to obtain the first reaction alkali solution, including the steps of:

[0087] S101. Use the first reaction primary mixture to carry out a first-stage reaction on the acidic gas in a countercurrent contact manner to respectively obtain a first reaction primary mixture and a first reaction primary purified gas;

[0088] S102. Carry out gas-liquid separation on the first reaction primary mixture to obtain the first reaction primary alkali solution;

[0089] S103. Boost the pressure of the first reaction primary alkali solution to respectively obtain a first alkali solution and a second alkali solution;

[0090] S104. Use the first reaction secondary mixture to carry out a second-stage reaction on the first reaction primary purified gas in a countercurrent contact manner to respectively obtain a first reaction secondary mixture and a first reaction secondary purified gas;

[0091] S105. Carry out gas-liquid separation on the first reaction secondary mixture to obtain the first reaction secondary alkali solution;

[0092] S106. Boost the pressure and carry out a first cooling on the first reaction secondary alkali solution to respectively obtain a third alkali solution and a fourth alkali solution;

[0093] S107. Use the first reaction tertiary mixture to carry out a third-stage reaction on the first reaction secondary purified gas in a countercurrent contact manner to respectively obtain a first reaction tertiary mixture and a first reaction purified gas;

[0094] S108. Carry out gas-liquid separation on the first reaction tertiary mixture to obtain the first reaction tertiary alkali solution;

[0095] S109. Boost the pressure and carry out a second cooling on the first reaction tertiary alkali solution to respectively obtain a fifth alkali solution and a sixth alkali solution;

[0096] Among them, the first reaction alkaline solution includes a first-stage reaction primary alkaline solution, a first-stage reaction secondary alkaline solution, and a first-stage reaction tertiary alkaline solution;

[0097] The first-stage reaction primary mixed solution is a mixed solution of the second alkaline solution and the third alkaline solution, the first-stage reaction secondary mixed solution is a mixed solution of the fourth alkaline solution and the fifth alkaline solution, and the first-stage reaction tertiary mixed solution is a mixed solution of the sixth alkaline solution and a part of the second reaction alkaline solution.

[0098] In the embodiments of the present application, the first reaction can be a reaction of one to ten stages. For example, the first reaction can include a first-stage reaction, can also include a third-stage reaction, and can also include a tenth-stage reaction. Correspondingly, the first reaction mixed solution for the first-stage reaction is the first-stage reaction primary mixed solution, the first reaction mixed solution for the third-stage reaction is the first-stage reaction tertiary mixed solution, and the first reaction mixed solution for the tenth-stage reaction is the first-stage reaction tenth mixed solution; the first reaction preferably includes a third-stage reaction. Through the above multi-stage reaction method, hydrogen sulfide in the acidic gas can fully enter the liquid phase for reaction within a short gas-liquid contact time, and carbon dioxide in the acidic gas hardly reacts with the alkaline solution within the short gas-liquid contact time, so that a high-purity sodium hydrosulfide product can be obtained.

[0099] It should be noted that in each of the above gas-liquid separation steps, not only can purified first-stage reaction primary alkaline solution, first-stage reaction secondary alkaline solution, and first-stage reaction tertiary alkaline solution be obtained, but also the gases in the first-stage reaction primary mixture, first-stage reaction secondary mixture, and first-stage reaction tertiary mixture can be gradually introduced from the first buffer tank 314 through the third connecting pipe 3132 into the third reaction column 313 and enter the second reactor 32 together with the first reaction purified gas, reducing the number of gas-liquid separation equipment units, simplifying the process flow, and enabling the gases in the first-stage reaction primary mixture, first-stage reaction secondary mixture, and first-stage reaction tertiary mixture to continue to be purified.

[0100] In some optional embodiments, the temperature of the first-stage reaction is 50°C to 80°C. Exemplarily, the temperature of the first-stage reaction can be 50°C, can also be 55°C, can also be 60°C, can also be 65°C, can also be 70°C, can also be 75°C, or can also be 80°C; the pressure of the first-stage reaction ≥ 0.10 MPa;

[0101] The temperature of the second-stage reaction is 45°C to 70°C. Exemplarily, it can be 45°C, can also be 50°C, can also be 55°C, can also be 60°C, can also be 65°C, or can also be 70°C; the pressure of the second-stage reaction ≥ 0.09 MPa;

[0102] The temperature of the third-stage reaction is 40°C to 65°C. Exemplarily, it can be 40°C, 45°C, 50°C, 55°C, 60°C, or 65°C; the pressure of the third-stage reaction is ≥0.08 MPa.

[0103] In the embodiments of the present application, by defining the specific temperatures and pressures of the first-stage reaction, the second-stage reaction, and the third-stage reaction, the production of by-products such as sodium sulfide, sodium carbonate, and sodium bicarbonate can be reduced, the yield of sodium hydrosulfide can be increased, and the formation of sodium sulfide crystals, sodium carbonate crystals, and sodium bicarbonate crystals can be avoided.

[0104] In some alternative embodiments, after the gas-liquid separation of the second mixture to obtain a second reaction lye and a second reaction purified gas respectively, the following steps are included:

[0105] S401. Boost the pressure and perform a third cooling on the second reaction lye to obtain a seventh lye and an eighth lye respectively;

[0106] Wherein, after the seventh lye and the sixth lye are mixed, the first reaction three-stage mixed liquid is formed;

[0107] After the eighth lye and the second reaction prepared lye are mixed, the second reaction mixed liquid is formed.

[0108] In the embodiments of the present application, by boosting the pressure and performing cooling after gas-liquid separation, the second reaction lye can be divided into a seventh lye and an eighth lye. By mixing and compounding each lye, it is possible to enable the hydrogen sulfide in the acidic gas to fully react with the lye within a short gas-liquid contact time and avoid the generation of excessive sodium carbonate and / or sodium bicarbonate.

[0109] In some alternative embodiments, after using the third reaction mixed liquid to perform a hydrogen sulfide removal reaction on the second reaction purified gas to obtain a third mixture and a third reaction purified gas respectively, and then performing gas-liquid separation on the third mixture to obtain a third reaction lye, the following steps are included:

[0110] S501. Boost the pressure and perform a fourth cooling on the third reaction lye to obtain a ninth lye, a tenth lye, and a third mixed product respectively, where

[0111] The third mixed product includes an eleventh lye and / or a third product;

[0112] After the ninth lye and the tenth lye are respectively mixed with the third prepared lye, the third reaction mixed liquid is formed;

[0113] The sum of the flow rates of the eleventh lye and the third product is the same as the flow rate of the third reaction prepared lye after the reaction.

[0114] In the embodiments of the present application, by boosting the pressure and cooling the third reaction lye after the hydrogen sulfide removal reaction, the ninth lye, the tenth lye, the eleventh lye and / or the third product can be obtained in sequence. By mixing and compounding the ninth lye and the tenth lye, the recycling of the lye can be realized, and hydrogen sulfide in the acidic gas can fully react with the lye within a short gas-liquid contact time, and excessive sodium carbonate and / or sodium bicarbonate can be avoided from being generated. At the same time, it is defined that the sum of the flow rates of the eleventh lye and the third product is the same as the flow rate of the third reaction-configured lye that has absorbed components such as hydrogen sulfide and carbon dioxide after the reaction. Therefore, by adjusting the flow rate of the eleventh lye entering the second reaction mixture, the contents of sodium sulfide, sodium carbonate, and sodium bicarbonate in the sodium hydrosulfide product can be flexibly adjusted, so that as many sodium hydrosulfide products as possible can be obtained on the premise that the indexes such as impurity content and concentration meet the standards such as "Industrial Sodium Hydrosulfide" GB / T 23937-2020.

[0115] It should be noted that the third product may be a mixed product with relatively high contents of sodium sulfide and / or sodium carbonate and / or sodium bicarbonate.

[0116] As Figure 4 shown, based on a general inventive concept, the embodiments of the present application provide a system for producing sodium hydrosulfide using acidic gas. The system is adapted to the method, and the system includes:

[0117] A reaction section, the reaction section includes a first reactor 31, a second reactor 32 and a third reactor 33. The first reactor 31 is provided with an air inlet to allow acidic gas to enter the system. The outlet of the first reactor 31 is communicated with the second reactor 32, and the outlet of the second reactor 32 is communicated with the third reactor 33;

[0118] A stripping evaporation tower 11, the liquid inlet of the stripping evaporation tower 11 is communicated with the liquid outlet of the first reactor 31;

[0119] A reaction pump group, the reaction pump group includes a first reaction pump, a second reaction pump 24 and a third reaction pump 25. Both ends of the first reaction pump are communicated with the top and bottom of the first reactor 31 respectively. Both ends of the second reaction pump 24 are communicated with the top and bottom of the second reactor 32 respectively. Both ends of the third reaction pump 25 are communicated with the top and bottom of the third reactor 33 respectively;

[0120] A cooling section, the cooling section is arranged in the first reactor 31.

[0121] The system is implemented based on the above method. For the specific steps of the method, reference can be made to the above embodiments. Since the system adopts some or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, which will not be elaborated herein one by one.

[0122] It should be noted that the acidic gas entering the system refers to the acidic gas from outside the system, which contains hydrogen sulfide and impurities such as carbon dioxide, water vapor, ammonia, and hydrocarbons.

[0123] To improve the universality of the system, the temperature of the acidic gas entering the system can be limited to 5°C to 100°C, and the pressure of the acidic gas ≥ 0.10 MPa.

[0124] In some alternative embodiments, the first reactor 31 includes a first reaction column 311, a second reaction column 312, a third reaction column 313, and a first buffer tank 314; the first reaction column 311 includes a first reaction section 3111 and a first connecting pipe 3112, the second reaction column 312 includes a second reaction section 3121 and a second connecting pipe 3122, the third reaction column 313 includes a third reaction section 3131 and a third connecting pipe 3132, the first reaction column 311 is connected to the first buffer tank 314 through the first connecting pipe 3112, the second reaction column 312 is connected to the first buffer tank 314 through the second connecting pipe 3122, and the third reaction column 313 is connected to the first buffer tank 314 through the third connecting pipe 3132;

[0125] A first partition 3141 and a second partition 3142 are provided in the first buffer tank 314 to cooperate with the first connecting pipe 3112, the second connecting pipe 3122, and the third connecting pipe 3132 to form a first buffer area, a second buffer area, and a third buffer area.

[0126] In the embodiments of the present application, the first reaction in the method can be carried out in the first reactor 31. By refining the specific composition of the first reactor 31, sufficient space can be provided for mixing between the acidic gas and the reaction mixture through the connection between the reaction section and the connecting pipe, and the mixing time can be made short enough. In addition, each connecting pipe cooperates with the first partition 3141 and the second partition 3142 to form a first buffer area, a second buffer area, and a third buffer area in the first buffer tank 314.

[0127] It should be noted that the first-stage reaction is carried out in the first reaction column 311, the second-stage reaction is carried out in the second reaction column 312, and the third-stage reaction is carried out in the third reaction column 313.

[0128] It should be noted that the first buffer is located directly below the first reaction column 311, the second buffer is located directly below the second reaction column 312, and the third buffer is located directly below the third reaction column 313.

[0129] It should be noted that generally three reaction columns are provided in the first reactor 31, and 1 to 10 reaction columns can be provided according to actual needs. For example, 1 reaction column can be used, 4 reaction columns can be used, 6 reaction columns can be used, or 10 reaction columns can be used.

[0130] In some alternative embodiments, the first reaction pump includes a first-stage reaction pump 21, a second-stage reaction pump 22, and a third-stage reaction pump 23; one end of the first-stage reaction pump 21 communicates with the first buffer tank 314, and the other end of the first-stage reaction pump 21 communicates with the first reaction section 3111 and the stripping evaporation tower 11 respectively;

[0131] One end of the second-stage reaction pump 22 communicates with the first buffer tank 314, and the other end of the second-stage reaction pump 22 communicates with the first reaction section 3111 and the second reaction section 3121 respectively;

[0132] One end of the third-stage reaction pump 23 communicates with the first buffer tank 314, and the other end of the third-stage reaction pump 23 communicates with the second reaction section 3121 and the third reaction section 3131 respectively.

[0133] In the embodiments of the present application, the specific composition of the first reaction pump is refined. By using the first-stage reaction pump 21, the second-stage reaction pump 22, and the third-stage reaction pump 23 to boost the pressure of the first buffer, the second buffer, and the third buffer respectively, it is convenient for subsequent cooling, and the alkali liquor formed by the reaction can be divided into alkali liquor components containing different sodium hydrosulfide and / or sodium sulfide contents, so that it is convenient for the subsequent preparation of the first reaction mixture, the second reaction mixture, and the third reaction mixture, realizing the recycling of the alkali liquor.

[0134] In some alternative embodiments, the cooling section includes a first cooler 41, a second cooler 42, a third cooler 43, and a fourth cooler 44. The first cooler 41 is arranged at the discharge end of the second-stage reaction pump 22, the second cooler 42 is arranged at the discharge end of the third-stage reaction pump 23, the third cooler 43 is arranged at the discharge end of the second reaction pump 24, and the fourth cooler 44 is arranged at the discharge end of the third reaction pump 25.

[0135] In the embodiments of the present application, by specifying the specific type of the cooler, the alkaline solution boosted by each cooler for the first reaction secondary pump 22, the first reaction tertiary pump 23, the second reaction pump 24, and the third reaction pump 25 can be cooled, so that mixed alkaline solutions at different temperatures can be obtained. Exemplarily, first reaction primary mixed solutions, first reaction secondary mixed solutions, and first reaction tertiary mixed solutions at different temperatures can be obtained. At the same time, the alkaline solution boosted by the first reaction primary pump 21 generally has a small temperature rise during the reaction, and a cooler for cooling may not be considered.

[0136] It should be noted that in the first reactor 31, the specific working process is as follows:

[0137] The second alkaline solution from the first reaction primary pump 21 is mixed with the third alkaline solution from the first reaction secondary pump 22, and after mixing, it becomes the first reaction primary mixed solution; this first reaction primary mixed solution contains components such as sodium hydroxide (NaOH), sodium sulfide (Na 2 S), sodium hydrosulfide (NaHS), etc. Generally, it enters the upper part of the first reaction column 311, and at the same time, the acid gas enters the lower part of the first reaction column 311 of the first reactor 31. The first reaction primary mixed solution and the acid gas are in countercurrent contact in the first reaction section 3111. During the contact process, the first reaction primary mixed solution absorbs hydrogen sulfide in the acid gas and undergoes the following reactions:

[0138] H 2 S(aq)+2NaOH(aq)→Na 2 S(aq)+2H 2 O (1),

[0139] Na 2 S(aq) + H 2 S(aq)→2NaHS(aq) (2);

[0140] During the above reaction process, the reaction rate of reaction (1) is relatively fast, while the reaction rate of reaction (2) is relatively slow. When sodium hydrosulfide approaches saturation, the reaction rate of reaction (2) is even slower.

[0141] The main reaction occurring in the first reaction section 3111 in the first reaction column 311 is reaction (2), that is, the reaction of sodium sulfide with hydrogen sulfide to form sodium hydrosulfide (NaHS).

[0142] In addition, when the acid gas contains carbon dioxide, the following side reactions will also occur:

[0143] CO 2 (aq)+NaOH(aq)→NaHCO 3 (aq) (3),

[0144] NaHCO3 (aq) + NaOH(aq) → Na 2 CO 3 (aq) + H2O (4);

[0145] Reactions (3) and (4) will not only lead to an increase in the consumption of lye and the generation of a large amount of waste lye, but also the generated carbonates will contaminate the quality of sodium hydrosulfide products. In addition, carbonates are prone to crystallize into solids, causing blockages in process pipelines and equipment. Therefore, it is very important to improve the absorption selectivity of hydrogen sulfide and reduce the generation of carbonates.

[0146] In the first reaction section 3111 of the first reactor 31 and all subsequent reaction processes, the system disclosed in the present application is not limited to taking the following measures to reduce the generation of carbonates:

[0147] (1) The pH value in the first reactor 31 and the second reactor 32 is maintained between 10.0 and 12.0, the gas-liquid contact time is maintained between 0.05 and 2.0 seconds, and the molar flow rate ratio of sodium hydroxide to hydrogen sulfide for gas-liquid contact and participating in the reaction is between 0.85 and 0.99; the pH value in the third reactor 33 is maintained between 11.5 and 13.5, the gas-liquid contact time is maintained between 0.10 and 3.0 seconds, and the molar flow rate ratio of sodium hydroxide to hydrogen sulfide for gas-liquid contact and participating in the reaction is between 1.05 and 3.50. Under the process flow and operating conditions disclosed in the present application, the absorption rate of hydrogen sulfide through the gas-liquid interface by the second lye and other lye-containing liquids is much faster than that of carbon dioxide. When carbon dioxide has not fully reacted with the second lye and other lye-containing liquids, the gas-liquid has separated, thereby reducing the generation amount of sodium bicarbonate and sodium carbonate.

[0148] (2) The reaction temperature of all the above can be flexibly adjusted. On the premise of meeting the quality requirements of sodium hydrosulfide products and the emission or purification index requirements of the purified gas including the first tail gas, since a higher reaction temperature is not conducive to the generation of sodium carbonate and sodium bicarbonate, the reaction of the present application can be operated at a higher temperature.

[0149] The first-stage reaction primary mixed liquid is called the first-stage reaction primary mixture after absorbing hydrogen sulfide in the acidic gas. The first-stage reaction primary mixture flows by gravity at a flow rate of 0.3 m / s to 0.9 m / s in the first connecting pipe 3112 to the first buffer zone. A liquid seal tray filled with liquid is provided at the lower part of the first connecting pipe 3112. The purpose of setting the liquid seal tray is to prevent the gas in the first buffer tank 314 from flowing into the first reaction column 311 or the gas in the first reaction column 311 from flowing into the first buffer tank 314. At this time, the first-stage reaction primary mixture buffers in the first buffer zone and separates the carried gas (gas-liquid separation) and is then called the first-stage reaction primary lye. Then, after being boosted by the first-stage reaction primary pump 21, it is divided into two parts. One part serves as the first lye (a part of the first-stage reaction lye) to the upper part of the stripping evaporation tower 11, and the other part serves as the second lye and circulates to the upper part of the first reaction column 311.

[0150] In the first reaction section 3111, 10% to 60% of the hydrogen sulfide contained in the acidic gas is absorbed and removed by the first-stage reaction primary mixed liquid, and then exits from the top of the first reaction column 311 as the first-stage reaction primary purified gas and enters the lower part of the second reaction column 312. The fourth lye from the first-stage reaction secondary pump 22 and the fifth lye from the first-stage reaction tertiary pump 23 are mixed and used as the first-stage reaction secondary mixed liquid. The first-stage reaction secondary mixed liquid enters the upper part of the second reaction column 312.

[0151] The first-stage reaction primary purified gas and the first-stage reaction secondary mixed liquid are in countercurrent contact in the second reaction section 3121. During the contact process, the first-stage reaction secondary mixed liquid absorbs the hydrogen sulfide in the first-stage reaction primary purified gas, and the main reaction of sodium sulfide reacting with hydrogen sulfide to form sodium hydrosulfide occurs. In addition, a small amount of sodium carbonate and sodium bicarbonate are also generated.

[0152] The first-stage reaction secondary mixed liquid is called the first-stage reaction secondary mixture after absorbing hydrogen sulfide in the primary purified gas. The first-stage reaction secondary mixture flows by gravity at a flow rate of 0.3 m / s to 0.9 m / s in the second connecting pipe 3122 to the second buffer zone. A liquid seal tray filled with liquid is provided at the lower part of the second connecting pipe 3122. The purpose of setting the liquid seal tray is to prevent the gas in the first buffer tank 314 from flowing into the second reaction column 312 or the gas in the second reaction column 312 from flowing into the first buffer tank 314.

[0153] The first-stage reaction secondary mixture buffers in the second buffer zone and separates the carried gas (gas-liquid separation) and is then called the first-stage reaction secondary lye. Then, after being boosted by the first-stage reaction secondary pump 22 and cooled by the first cooler 41, it is divided into two parts. One part serves as the third lye to the upper part of the first reaction column 311, and the other part serves as the fourth lye to the upper part of the second reaction column 312.

[0154] In the second reaction section 3121, 20% - 80% of the hydrogen sulfide contained in the primary purified gas is absorbed and removed by the first reaction secondary mixed liquid, and then, as the first reaction secondary purified gas, it is discharged from the top of the second reaction column 312 and enters the lower part of the third reaction column 313; the sixth caustic solution from the first reaction tertiary pump 23 and the seventh caustic solution from the second reaction pump 24 are mixed and used as the first reaction tertiary mixed liquid, which enters the upper part of the third reaction column 313. The first reaction secondary purified gas and the first reaction tertiary mixed liquid are in countercurrent contact in the third reaction section 3131. During the contact process, the hydrogen sulfide in the first reaction secondary purified gas is absorbed by the first reaction tertiary mixed liquid, and the main reaction of sodium sulfide reacting with hydrogen sulfide to form sodium hydrosulfide occurs. Additionally, a small amount of sodium carbonate and sodium bicarbonate are formed.

[0155] After absorbing the hydrogen sulfide in the first reaction secondary purified gas, the first reaction tertiary mixed liquid is called the first reaction tertiary mixture. The first reaction tertiary mixture flows by gravity through the third connecting pipe 3132 to the third buffer zone. The diameter of the third connecting pipe 3132 is the same as that of the third reaction section 3131. The gas in the first buffer tank 314 can flow upward through the third connecting pipe 3132 to the top of the third reaction column 313 and be discharged from the top. After buffering in the third buffer zone and separating the carried gas (gas-liquid separation), the first reaction tertiary mixture is called the first reaction tertiary caustic solution, and then it is boosted by the first reaction tertiary pump 23 and cooled by the second cooler 42 and then divided into two parts. One part is used as the fifth caustic solution to the upper part of the second reaction column 312, and the other part is used as the sixth caustic solution to the upper part of the third reaction column 313;

[0156] The first mixture includes the first reaction primary mixture, the first reaction secondary mixture, and the first reaction tertiary mixture.

[0157] In the third reaction section 3131, 20% - 80% of the hydrogen sulfide contained in the secondary purified gas is absorbed and removed by the first reaction tertiary mixed liquid, and then, as the first reaction tertiary purified gas, it is discharged from the top of the third reaction column 313 and enters the second reactor 32 for further reaction.

[0158] It should be noted that the internals for gas-liquid contact, mass transfer, and heat transfer in the first reaction section 3111, the second reaction section 3121, and the third reaction section 3131 can be trays or packings; when they are trays, the number of trays is 4 - 16; when they are packings, the height of the packing section is 0.5m - 6.0m, and the bed diameter is designed based on the treatment of 200 Nm 2 bed cross-sectional area per 1m 3 / h - 2000 Nm 3 / h of acid gas.

[0159] It should be noted that the configured alkali is an aqueous sodium hydroxide solution with a mass fraction of 20% to 50%. The pressure of the configured alkali is 0.4 MPa to 2.2 MPa, and the temperature of the configured alkali is 30 °C to 50 °C. The flow rate of the configured alkali solution is determined in such a way that the molar flow rate of sodium hydroxide in the configured alkali is equal to the molar flow rate of hydrogen sulfide in the acidic gas. After the configured alkali solution enters the system, it is then divided into a second reaction configured alkali solution and a third reaction configured alkali solution, which enter the upper part of the second reactor 32 and the upper part of the third reactor 33 respectively. The ratio of the flow rate of the second reaction configured alkali solution to the flow rate of the configured alkali solution is not less than 0.95, and the ratio of the flow rate of the third reaction configured alkali solution to the flow rate of the configured alkali solution is not greater than 0.05.

[0160] According to the raw material composition of the acidic gas and the different required product qualities, the mass ratios of the flow rates of the second alkali solution, the third alkali solution, the fourth alkali solution, the fifth alkali solution, the sixth alkali solution, and the seventh alkali solution to the flow rate of the configured alkali can be adjusted between 0.5 and 5.0. When the hydrogen sulfide content in the raw material acidic gas is high or the quality requirement of the sodium hydrosulfide product is high, this ratio is correspondingly increased.

[0161] The buffering time of the first reaction primary alkali solution in the first buffer zone, the first reaction secondary alkali solution in the second buffer zone, and the first reaction tertiary alkali solution in the third buffer zone is all 10 min to 40 min.

[0162] In the first reactor 31, by adjusting the flow rates and / or the temperatures of the second alkali solution, the third alkali solution, the fourth alkali solution, the fifth alkali solution, the sixth alkali solution, and the seventh alkali solution, the total removal rate of hydrogen sulfide in the acidic gas can be controlled between 45% and 60%.

[0163] On the other hand, a part of the first reaction alkali solution (the first alkali solution) enters the upper part of the stripping evaporation tower 11, and the heat source enters the lower part of the stripping evaporation tower 11. Under the continuous heating of the heat source, impurities such as ammonia and oil carried by the first reaction alkali solution are stripped out due to heat, and part of the water is also vaporized due to heat. These gases flow upward from the bottom of the stripping evaporation tower 11 and are discharged from the top as stripping tail gas, and can be mixed with the third reaction purified gas from the top of the third reactor 33 as a mixed gas.

[0164] There are two output methods for the mixed gas. One is that when the acidic gas from outside the system does not contain ammonia or the volume fraction of ammonia in the mixed gas < 5%, it is directly output to the outside of the system; the other is that when the volume fraction of ammonia in the mixed gas ≥ 5%, it enters the ammonia absorption tower 12 for treatment. After the ammonia, oil, and part of the water carried by the first reaction alkali solution are removed in the stripping evaporation tower 11, if the impurity content, concentration, etc. of the first reaction alkali solution meet the requirements of the "Industrial Sodium Hydrosulfide" GB / T 23937-2020 standard, it can leave the system as the first product from the bottom of the stripping evaporation tower 11, and this first product is the sodium hydrosulfide product.

[0165] It should be noted that the system disclosed in this application can also extract a part of the bottom liquid in the stripping evaporation tower 11, boost the pressure, and then send it to the top of the first stripping evaporation section 111 and / or the top of the second stripping evaporation section 112. This part of the bottom liquid flows downward by gravity in the tower and contacts the rising steam in a countercurrent manner, which can further reduce the contents of impurities such as ammonia and oil in the first product.

[0166] The above heat source can be steam, or can be heat-conducting oil or a hot process fluid; when the heat source is steam, the steam is 0.8 MPa to 2.0 MPa saturated steam; when the heat source is heat-conducting oil or a hot process fluid, the inlet temperature of the heat-conducting oil or the hot process fluid is not greater than 250 °C, and the outlet temperature is not less than 160 °C.

[0167] When the sum of the mass fractions of ammonia, oil, water, etc. in the acid gas is greater than 30%, an ammonia reboiler and an ammonia condenser can be provided in the stripping evaporation tower 11 to further remove impurities such as ammonia and oil carried by the first reaction lye and further concentrate the first reaction lye.

[0168] It should be noted that although some conventional components such as a boost pump, a heat exchanger, a buffer tank, a control valve, etc. are not described in this application. Specifically, for example, a heat exchanger for cooling the first product is not described or not shown in the drawings, but these components are obviously conventional components well known to those skilled in the art.

[0169] The stripping evaporation tower 11 can be operated under the following conditions: the top temperature is 95 °C to 135 °C, the bottom temperature is 105 °C to 145 °C, and the top pressure is 0.05 MPa to 0.30 MPa; preferably, two sections of packing are provided in the tower, and the height of each packing section is 2 m to 5 m.

[0170] In some alternative embodiments, the second reactor 32 includes a fourth reaction section 321, a fifth reaction section 322, a second buffer tank 323, and a valve group. The liquid outlet ends of the fourth reaction section 321 and the fifth reaction section 322 are connected to the second buffer tank 323, and the fourth reaction section 321 and the fifth reaction section 322 are respectively connected to the gas outlet of the first reactor 31; the fourth reaction section 321 and the fifth reaction section 322 are connected by the valve group to enable series, parallel, or independent operation between the fourth reaction section 321 and the fifth reaction section 322.

[0171] In some alternative embodiments, the valve group includes a first valve 324, a second valve 325, a third valve 326, a fourth valve 327, a fifth valve 328 and a sixth valve 329. The tops of the fourth reaction section 321 and the fifth reaction section 322 are connected by the first valve 324 and the second valve 325. The bottoms of the fourth reaction section 321 and the fifth reaction section 322 are connected by the fifth valve 328 and the sixth valve 329. The fourth reaction section 321 is connected to the bottom of the fifth reaction section 322 by the third valve 326. The top of the fifth reaction section 322 is connected to the bottom of the fourth reaction section 321 by the fourth valve 327.

[0172] In the embodiments of the present application, the specific composition of the second reactor 32 is defined. Through the fourth reaction section 321, the fifth reaction section 322, the second buffer tank 323 and the valve group, the fourth reaction section 321 and the fifth reaction section 322 can be connected in series, in parallel or operated individually according to actual needs. For example, when the first valve 324 is open, the second valve 325 is closed, the third valve 326 is closed, the fourth valve 327 is open, the fifth valve 328 is closed, and the sixth valve 329 is open, the reaction materials are operated in series in the order of first reacting in the fourth reaction section 321 and then reacting in the fifth reaction section 322. This setting can make the operation of the system disclosed in the present application more flexible. For example, when the carbon dioxide content in the feed is high, in order to avoid excessive formation of sodium carbonate or sodium bicarbonate, it is necessary to reduce the reaction time, and individual operation is preferred; when the carbon dioxide content in the feed is low, in order to make the alkaline solution absorb hydrogen sulfide more fully, series operation of two units is preferred; when the flow rate of the tertiary purified gas of the first reaction is the largest, in order to reduce the pressure drop of the second reactor 32, parallel operation of two units is preferred.

[0173] The specific entry position of the tertiary purified gas of the first reaction is on the connecting pipe between the first valve 324 and the second valve 325; the second reaction configured alkali from the configured alkali of the second reaction and the eighth alkali solution from the second reaction pump 24 are mixed and then used as the second reaction mixture. The second reaction mixture also enters the connecting pipe between the first valve 324 and the second valve 325. At the same time, the two materials are fully mixed on the connecting pipe between the first valve 324 and the second valve 325, and then enter the fourth reaction section 321 and / or the fifth reaction section 322 that are connected in series, in parallel or operated individually.

[0174] In the fourth reaction section 321 and / or the fifth reaction section 322, the first reaction three-stage purified gas and the second reaction mixed liquid are further fully mixed, and mainly the reactions of sodium hydroxide with hydrogen sulfide to form sodium sulfide and sodium sulfide with hydrogen sulfide to form sodium bisulfide occur. Additionally, a small amount of sodium carbonate and sodium bicarbonate are generated. The reaction products enter the second buffer tank 323 for gas-liquid separation. The separated liquid phase is discharged from the bottom of the second buffer tank 323 as the second reaction alkali liquid. After being pressurized by the second reaction pump 24 and cooled by the third cooler 43, a part of it returns to the third reaction column 313 as the seventh alkali liquid, and another part returns to the inlets of the fourth reaction section 321 and / or the fifth reaction section 322 as the eighth alkali liquid; the separated gas phase enters the third reactor 33 as the second reaction purified gas to continue the reaction for removing hydrogen sulfide.

[0175] The fourth reaction section 321 and the fifth reaction section 322 can adopt a suitable reactor form. For example, it can be a fixed-bed reactor, a tubular reactor, a static mixer, a stirred tank reactor, a liquid-liquid ejector, etc. Preferably, a tubular reactor or a static mixer is selected; when a tubular reactor is selected, multiple reaction tubes are arranged inside the reactor, fillers or wire meshes are filled inside the reaction tubes, and a cooling and / or heating medium is arranged outside the reaction tubes to cool and / or heat the reaction medium inside the reaction tubes and control the reaction temperature.

[0176] The second reactor 32 can be operated under the following conditions:

[0177] Fourth reaction section 321 and / or fifth reaction section 322: The inlet temperature is 50°C to 60°C, the inlet pressure is 0.07 MPa, and the gas-liquid volume ratio under the operating condition is 1 to 50; the superficial linear velocity of the mixture composed of the first reaction three-stage purified gas and the second reaction mixed liquid is controlled within 4.0 m / s to 12.0 m / s; the gas-liquid two-phase contact time is 0.05 s to 1.50 s; the liquid buffering time in the second buffer tank 323 is 10 min to 40 min.

[0178] According to the content of hydrogen sulfide in the first reaction three-stage purified gas and different required product qualities, the mass ratio of the flow rate of the eighth alkali liquid to the flow rate of the prepared alkali liquid can be adjusted between 0.5 and 5.0. When the content of hydrogen sulfide in the first reaction three-stage purified gas is high or the quality of the sodium bisulfide product required is high, this ratio is correspondingly increased.

[0179] By adjusting the flow rate and / or temperature of the second reaction prepared alkali liquid and the eighth alkali liquid, the total removal rate of hydrogen sulfide in the acid gas can be controlled within 40% to 55% in the second reactor 32.

[0180] In some alternative embodiments, the third reactor 33 includes a sixth reaction section 331, a seventh reaction section 332, an eighth reaction section 333, and a third buffer tank 334. The gas outlet of the second reactor 32 communicates with the bottom of the eighth reaction section 333. The liquid inlet end of the third reaction pump 25 communicates with the bottom of the third buffer tank 334. The liquid outlet end of the third reaction pump 25 is respectively disposed between the sixth reaction section 331 and the seventh reaction section 332 and between the seventh reaction section 332 and the eighth reaction section 333.

[0181] In the embodiment of the present application, the second reaction purified gas is fed into the lower part of the eighth reaction section 333, and sequentially enters the eighth reaction section 333 and the seventh reaction section 332 from bottom to top in the reactor, and respectively countercurrently contacts with the ninth caustic solution and the tenth caustic solution from the third reaction pump 25, and mainly reacts to generate sodium sulfide by the reaction of sodium hydroxide and hydrogen sulfide. In addition, some sodium hydrosulfide, trace amounts of sodium carbonate, and sodium bicarbonate are generated. Then the second reaction purified gas continues to flow upward from the top of the seventh reaction section 332 and enters the sixth reaction section 331, and countercurrently contacts with the third reaction prepared caustic solution from the prepared caustic in the sixth reaction section 331, mainly reacting to generate sodium sulfide. In addition, a small amount of sodium carbonate and sodium bicarbonate are generated. In the third reactor 33, the hydrogen sulfide contained in the second reaction purified gas is removed to not more than 20 mg / m 3 or the required target value, and then continues to flow upward as the third reaction purified gas and leaves the third reactor 33 from the top, and then is mixed with the stripping tail gas from the top of the stripping evaporation tower 11 to form a mixed gas.

[0182] In the third reactor 33, the ninth caustic solution, the tenth caustic solution, and the third reaction prepared caustic solution flow downward respectively, and a third mixture is obtained in the eighth reaction section 333. The third mixture flows to the third buffer tank 334, and after separating the carried gas in the third buffer tank 334, it leaves the third reactor 33 from the bottom as the third reaction caustic solution, and then is boosted by the third reaction pump 25 and cooled by the fourth cooler 44 and then divided into the ninth caustic solution, the tenth caustic solution, the eleventh caustic solution, and / or the third product. The ninth caustic solution and the tenth caustic solution respectively enter the upper part of the eighth reaction section 333 and the upper part of the seventh reaction section 332; the eleventh caustic solution enters the second reaction mixed solution; at the same time, the third product is either output to other devices or conveyed as an intermediate material to a specially provided third product buffer tank.

[0183] It should be noted that the third product is continuously or intermittently withdrawn from the third product buffer tank, mixed with the prepared caustic solution in a very small proportion of 0.01 to 0.05, and input into the system along with the prepared caustic solution, and the sodium sulfide in the third product further reacts with hydrogen sulfide to form sodium hydrosulfide, which can increase the output of sodium hydrosulfide.

[0184] The third reactor 33 can be operated under the following conditions:

[0185] The operating temperature of the sixth reaction section 331 is 45°C to 60°C, and the operating pressure

[0186] The operating temperature of the seventh reaction section 332 is 40°C to 55°C, and the operating pressure

[0187] The operating temperature of the eighth reaction section 333 is 40°C to 55°C, and the operating pressure

[0188] The internals for gas-liquid contact, mass transfer, and heat transfer in the sixth reaction section 331, seventh reaction section 332, and eighth reaction section 333 can be trays or packings; when they are trays, the number of trays per section is 6 to 16; when they are packings, the height of each packing section is 3.0 m to 6.0 m, and the bed diameter is designed based on the cross-sectional area of the bed per 1 m 2 bed cross-sectional area for treating 40 Nm 3 / h to 400 Nm 3 / h of the second reaction purified gas; according to the composition of the second reaction purified gas and different required product qualities, the mass ratio of the ninth caustic solution, tenth caustic solution to the configured caustic flow rate entering the system can be adjusted between 0.1 and 5.0. When the hydrogen sulfide content in the second reaction purified gas is relatively high or the quality of the second product (i.e., ammonia water) is required to be relatively high, this ratio is correspondingly increased.

[0189] Under normal operating conditions, the ratio of the configured caustic flow rate in the third reaction to the configured caustic flow rate is not greater than 0.05. In some special cases, such as when it is required that the hydrogen sulfide content in the first tail gas is not greater than 5 mg / m 3 and the volume fraction of carbon dioxide in the acid gas raw material is greater than or equal to 10%, to meet the quality requirements of each product, the ratio of the configured caustic flow rate in the third reaction to the configured caustic flow rate can be greater than 0.05. The sum of the flow rate of the eleventh caustic solution and the flow rate of the third product is the same as the configured caustic flow rate in the third reaction after absorbing components such as hydrogen sulfide and carbon dioxide; the minimum flow rates of both the eleventh caustic solution and the third product are 0, and the maximum flow rates are the same as the configured caustic flow rate in the third reaction after absorbing components such as hydrogen sulfide and carbon dioxide. And when the flow rate of the eleventh caustic solution is 0, the flow rate of the third product is the largest, and vice versa.

[0190] The flow rate of the eleventh caustic solution or / and the third product is controlled by a liquid level regulator installed in the third buffer tank 334.

[0191] The buffering time of the third reaction caustic solution in the third buffer tank 334 is 10 min to 40 min.

[0192] It should be noted that the operating conditions of the fourth cooler 44 are: the outlet temperature is 40°C to 55°C.

[0193] In summary, the system disclosed in this application highly couples the first reactor 31, the second reactor 32, and the third reactor 33. In this system, 95% or more of the hydrogen sulfide in the acidic gas raw material is removed in the first reactor 31 and the second reactor 32, while only ≤5% of the hydrogen sulfide in the acidic gas raw material is removed in the third reactor 33. By controlling the flow rate of the alkali solution, the hydrogen sulfide participating in the reaction in the first reactor 31 and the second reactor 32 is in an excess state, and the sodium hydroxide participating in the reaction in the third reactor 33 is in an excess state. Therefore, the first reactor 31 and the second reactor 32 provided in the system disclosed in this application are mainly used to reduce the contents of sodium sulfide, sodium carbonate, and sodium bicarbonate in the sodium hydrosulfide product, ensuring that the sodium hydrosulfide product meets the requirements of the "Industrial Sodium Hydrosulfide" GB / T

[0194] 23937-2020 standard requirements, and the specific standard requirements are shown in Table 1. Table 1 Industrial Sodium Hydrosulfide Standard Indexes

[0195]

[0196]

[0197] The third reactor 33 provided in the system disclosed in this application is mainly used to ensure that the purified gas output to the outside of the system meets the emission or purification index requirements. By adjusting the flow rate and / or temperature of the ninth alkali solution, the tenth alkali solution, especially the alkali solution configured for the third reaction, the hydrogen sulfide contained in the purified gas of the third reaction is removed to no more than 20 mg / m 3 or no more than the required target value, enabling the subsequent first tail gas or mixed gas to meet the emission standards or be recycled.

[0198] In addition, the purpose of setting the stripping evaporation tower 11 in the system disclosed in this application is to remove the ammonia, oil, and part of the water carried by the first reaction alkali solution, so that the contents of impurities such as ammonia and oil in the sodium hydrosulfide product are as low as possible, and the mass fraction or concentration of sodium hydrosulfide in the sodium hydrosulfide product meets the requirements of the "Industrial Sodium Hydrosulfide" GB / T 23937-2020 standard.

[0199] Furthermore, the system disclosed in this application can process more odious acidic gas raw materials and / or produce products with higher quality indicators. For example, it can process acidic gas raw materials with a carbon dioxide volume fraction greater than 10%, and / or require the hydrogen sulfide content in the first tail gas to be as low as 5 mg / m 3Under the operating conditions, to simultaneously meet the requirements of tail gas purification indicators and sodium hydrosulfide product and ammonia water indicators, the following measures may be taken in this system: keep the flow rate of the alkali solution in the second reaction configuration unchanged, increase the flow rate of the alkali solution in the third reaction configuration until the hydrogen sulfide contained in the purified gas of the third reaction meets the specific indicator requirements; at this time, due to the excess alkali solution in the third reaction configuration, the product in the third reactor 33 not only contains excessive sodium hydroxide, but also a large amount of sodium sulfide generated by the reaction. If all these reaction materials enter the second reactor 32 as the eleventh alkali solution, it will cause the quality of the sodium hydrosulfide product produced by the entire system to be unqualified. In this case, the system will output all or part of this reaction material as the third product from the system, so as to ensure that the first reactor 31 and the second reactor 32 produce sodium hydrosulfide products that meet the quality requirements at a low pH value.

[0200] Furthermore, the beneficial effects of setting the second alkali solution, the third alkali solution, the fourth alkali solution, the fifth alkali solution, the sixth alkali solution, the seventh alkali solution, the eighth alkali solution, the ninth alkali solution, the tenth alkali solution, and the eleventh alkali solution in this system include the following aspects:

[0201] (1) Ensure sufficient contact between the gas and the liquid in each reaction section, so that sodium hydroxide and hydrogen sulfide in it fully react to form sodium sulfide, and the formed sodium sulfide further reacts with hydrogen sulfide to form sodium hydrosulfide. The above reaction process can reduce the generation amount of sodium sulfide and make the sodium sulfide content in the sodium hydrosulfide product meet the index requirements of relevant specifications;

[0202] (2) Absorb the heat released by the reaction and flexibly adjust the reaction temperature; since the third alkali solution and the fourth alkali solution are cooled by the first cooler 41, the fifth alkali solution and the sixth alkali solution are cooled by the second cooler 42, the seventh alkali solution and the eighth alkali solution are cooled by the third cooler 43, and the ninth alkali solution, the tenth alkali solution, and the eleventh alkali solution are cooled by the fourth cooler 44; the temperatures of these alkali solutions can be flexibly adjusted according to the reaction heat release and the temperature rise of the reactor, so that the reaction proceeds in the direction of increasing the yield of sodium hydrosulfide and decreasing the yields of sodium sulfide, sodium bicarbonate, and sodium carbonate.

[0203] Furthermore, in the system disclosed in this application, an on-line analyzer for sodium sulfide content can also be provided on the first product pipeline, and a supporting flow regulating valve can be provided on the pipeline of the alkali solution in the second reaction configuration. When the on-line analyzer for sodium sulfide content detects that the sodium sulfide content of the first product is greater than 1.0% or the target value set as needed, a signal is output to the flow regulating valve on the pipeline of the alkali solution in the second reaction configuration to reduce the opening of this valve and decrease the flow rate of the alkali solution in the second reaction configuration; an on-line analyzer for hydrogen sulfide content is provided on the mixed gas or the first tail gas pipeline, and a supporting flow regulating valve is provided on the pipeline of the alkali solution in the third reaction configuration. When the on-line analyzer for hydrogen sulfide content detects that the hydrogen sulfide content of the mixed gas or the first tail gas is greater than 20mg / m 3When reaching specific index requirements, an output signal is sent to the flow regulating valve on the alkali pipeline of the third reaction configuration to increase the opening degree of the valve and improve the alkali flow rate of the third reaction configuration.

[0204] In some alternative embodiments, the system further includes:

[0205] An ammonia treatment unit, which includes an ammonia absorption tower 12, an ammonia rectification tower 13, and an ammonia water pump 26. The air inlet end of the ammonia absorption tower 12 is respectively connected to the air outlet of the stripping evaporation tower 11 and the air outlet of the third reactor 33. The liquid outlet end of the ammonia absorption tower 12 is connected to the liquid inlet end of the ammonia water pump 26. The liquid outlet end of the ammonia water pump 26 is respectively connected to the liquid inlet ends of the ammonia absorption tower 12 and the ammonia rectification tower 13.

[0206] In some alternative embodiments, the ammonia absorption tower 12 sequentially includes a first absorption section 121, a second absorption section 122, and an absorption liquid buffer tank 123 from top to bottom. The liquid outlet end of the ammonia water pump 26 is arranged between the first absorption section 121 and the second absorption section 122. The air outlet of the stripping evaporation tower 11 is connected to the top of the absorption liquid buffer tank 123. The bottom of the absorption liquid buffer tank 123 is connected to the liquid inlet end of the ammonia water pump 26.

[0207] In some alternative embodiments, the ammonia rectification tower 13 includes a condensation section 131, a first separation section 132, a second separation section 133, and a reboiler 134 from top to bottom. The liquid outlet end of the ammonia water pump 26 is arranged between the first separation section 132 and the second separation section 133. The reboiler 134 is arranged at the bottom of the ammonia rectification tower 13.

[0208] In the embodiments of the present application, the stripping tail gas and the third reaction purified gas are fully mixed to form a mixed gas, which is then mixed with the second tail gas coming from the top of the ammonia rectification tower 13, and then enters the lower part of the second absorption section 122 of the ammonia absorption tower 12 from bottom to top, and countercurrently contacts the first absorption liquid from the ammonia water pump 26. 80% - 95% of the ammonia in the mixed gas is absorbed by the first absorption liquid, and then the mixed gas enters the first absorption section 121 from bottom to top, and countercurrently contacts the configured water from the boundary area in the first absorption section 121 to remove the contained ammonia gas to no more than 50 mg / m 3 or the required target value, and then leaves the system as the first tail gas.

[0209] This configured water comes from outside the system and can be deoxygenated water or demineralized water, preferably deoxygenated water with a temperature of 5°C - 30°C.

[0210] In the ammonia absorption tower 12, the first absorption liquid and the prepared water flow downward to the absorption liquid buffer tank 123, where they are mixed. After separating the carried gas, the absorption liquid leaves the ammonia absorption tower 12 from the bottom, and then is divided into the first absorption liquid and the second absorption liquid after being pressurized by the ammonia water pump 26. The first absorption liquid enters the upper part of the second absorption section 122, and the second absorption liquid enters the ammonia rectification tower 13.

[0211] Furthermore, a cooler can be provided on the first absorption liquid pipeline as needed to further cool the first absorption liquid to 15°C - 30°C before it enters the second absorption section 122.

[0212] The ammonia absorption tower 12 can be operated under the following conditions: the top operating temperature is 35°C - 45°C, the bottom operating temperature is 40°C - 50°C, and the top operating pressure is ≥0.05 MPa; there are 2 - 4 packing sections in the tower, and the height of each packing section is 2 m - 5 m.

[0213] To ensure that the ammonia contained in the mixed gas is removed to no more than 50 mg / m 3 or the required target value, the gas-liquid volume ratio of the mixed gas to the first absorption liquid is controlled within the range of 1 - 50 under the operating conditions; the gas-liquid volume ratio of the mixed gas to the prepared water is controlled within the range of 2 - 100 under the operating conditions.

[0214] The buffering time of the absorption liquid in the absorption liquid buffer tank 123 is 10 min - 40 min.

[0215] It should be noted that during the process of the second absorption liquid from the ammonia water pump 26 entering the ammonia rectification tower 13, the second absorption liquid is fed at a position between the top of the second separation section 133 and the first separation section 132. The ammonia rectification tower 13 is generally a rectification tower. Under the rectification effect, trace amounts of hydrogen sulfide, light hydrocarbons, carbon dioxide, and part of the water and ammonia contained in the second absorption liquid are separated as light components and flow upward through the first separation section 132. When flowing through the condensation section 131, part of the ammonia water carried is condensed into a liquid and flows downward to the lower part of the tower, while the uncondensed gas continues to flow upward and finally exits from the top of the ammonia rectification tower 13, and then returns to the mixed gas pipeline as the second tail gas and enters the ammonia absorption tower 12 together with the mixed gas, so that the carried ammonia is absorbed again by the first absorption liquid or / and the prepared water; while the second absorption liquid after removing the gas flows downward and enters the tower kettle through the second separation section 133.

[0216] The reboiler 134 provides energy for separation. The gas-liquid two-phase discharged from the reboiler 134 returns to the bottom of the ammonia rectification tower 13 and is separated into gas and liquid at the bottom. The gas flows upward, and the liquid returns to the bottom of the tower. In the bottom of the tower, it is mixed with the second absorbent after removing the gas. A part of the mixed liquid returns to the reboiler 134, and the other part is taken out of the system as the second product. Under the rectification of the ammonia rectification tower 13, the mass fraction of ammonia in the second product is not less than 20%, the hydrogen sulfide content is not more than 10 mg / kg, or it meets other specific indicators, so that the second product can be determined as ammonia water.

[0217] The ammonia rectification tower 13 can be operated under the following conditions: the top operating temperature is -15°C to 45°C, the bottom operating temperature is 120°C to 185°C, and the top operating pressure is 1.0 MPa to 1.8 MPa; two sections of packing are arranged in the tower, and the height of each section of packing is 4 m to 6 m.

[0218] In summary, a system for producing sodium hydrosulfide using acidic gas provided by an embodiment of the present application adopts a technical concept different from that of a conventional process system, which is mainly reflected in:

[0219] ① A highly coupled reaction system including a first reactor 31, a second reactor 32, and a third reactor 33 is set: in this reaction system, 95% or more of the hydrogen sulfide in the acidic gas raw material is removed in the first reactor 31 and the second reactor 32, and only less than 5% of the hydrogen sulfide is removed in the third reactor 33; the hydrogen sulfide participating in the reaction in the first reactor 31 and the second reactor 32 is in an excess state, and the sodium hydroxide participating in the reaction in the third reactor 33 is in an excess state (the excess alkali is used to fully absorb the hydrogen sulfide in the acidic gas and react deeply with the hydrogen sulfide); and through the set third product, the liquid-phase product of the third reactor 33 can be partially or fully output to the outside of the system as the third product;

[0220] ② An ammonia recovery system including an ammonia absorption tower 12 and an ammonia rectification tower 13 is also set. The ammonia absorption tower 12 is mainly used to recover the ammonia component in the mixed gas, and the ammonia rectification tower 13 is mainly used to refine the ammonia water.

[0221] The beneficial effects obtained by this technical concept include but are not limited to the following points:

[0222] ① The generation amount of by-products such as sodium sulfide, sodium carbonate, and sodium bicarbonate in the first reactor 31 and the second reactor 32 can be reduced, ensuring that the contents of sodium sulfide, sodium carbonate, and sodium bicarbonate in the sodium hydrosulfide product meet the requirements of relevant standards;

[0223] ② The hydrogen sulfide in the acidic gas is deeply reacted in the third reactor 33 to ensure that the purified gas output from the system meets the emission or purification index requirements, and to ensure that the ammonia water output from the system meets the relevant index requirements;

[0224] ③ Without setting up an amine solution absorption-regeneration system to purify hydrogen sulfide in the sour gas raw material, it is possible to process more inferior sour gas raw materials and produce tail gas, sodium hydrosulfide and ammonia products that meet the requirements. For example, when processing sour gas raw materials with a carbon dioxide volume fraction greater than 10%, the following measures are not limited in this system: maintaining the flow rate of the lye configured in the second reaction unchanged, increasing the flow rate of the lye configured in the third reaction, and outputting part or all of the liquid phase product of the third reactor 33 as the third product outside the system;

[0225] ④ It is possible to produce ammonia products with a mass fraction of ammonia not less than 20%, a hydrogen sulfide content not greater than 10 mg / kg, or meeting other specific indicators.

[0226] In summary, this application highly couples the sour gas treatment facilities. Without setting up an amine solution absorption-regeneration system to purify hydrogen sulfide, it can ensure that the hydrogen sulfide content in the first tail gas or mixed gas output outside the system is less than 20 mg / Nm 3 or meets the special specified index requirements, can effectively remove impurities such as oils and ammonia in the sodium hydrosulfide product, can produce sodium hydrosulfide liquid products of different specifications, and can also produce ammonia water, with the characteristics of high resource utilization degree, high selectivity of sodium hydrosulfide, simple process, flexible operation, and low equipment and operation costs.

[0227] The following further elaborates on this application in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate this application and not to limit the scope of this application. The experimental methods without specific conditions noted in the following embodiments are usually determined according to national standards. If there is no corresponding national standard, they are carried out according to general international standards, conventional conditions, or the conditions recommended by the manufacturer.

[0228] Example 1

[0229] Using the system as Figure 4 described, at a temperature of 85 °C, a pressure of 0.7 MPa, and 224 Nm 3Taking a certain acidic gas with a flow rate of / h (100 kmol / h) as the raw material to produce sodium hydrosulfide and ammonia water; the volume composition of the acidic gas is as follows: hydrogen: 0.1%, nitrogen: 0.1%, water: 21.0%; hydrogen sulfide: 33.7%, ammonia: 41.5%, carbon dioxide: 3.3%, methane: 0.2%, ethane: 0.1%. The prepared alkali solution comes from outside the system. The prepared alkali solution is an aqueous sodium hydroxide solution with a mass fraction of 30%, at a temperature of 40 °C and a pressure of 0.7 MPa. The mass flow rate of the prepared alkali solution is 4493.0 kg / h. The molar flow rate of sodium hydroxide in the prepared alkali solution and the molar flow rate of hydrogen sulfide in the acidic gas are both 33.7 kmol / h. After the prepared alkali solution enters the system, it is further divided into the second reaction prepared alkali solution and the third reaction prepared alkali solution. The flow rates of the second reaction prepared alkali solution and the third reaction prepared alkali solution are 4290.8 kg / h and 202.2 kg / h respectively, accounting for 95.5% and 4.5% of the total flow rate of the prepared alkali solution respectively.

[0230] The acidic gas first enters the first reactor 31 for reaction. The operating conditions of the first-stage reactor are:

[0231] The operating temperature of the first reaction column 311 is 70 °C and the operating pressure is 0.60 MPa;

[0232] The operating temperature of the second reaction column 312 is 65 °C and the operating pressure is 0.59 MPa;

[0233] The operating temperature of the third reaction column 313 is 60 °C and the operating pressure is 0.58 MPa;

[0234] The flow rates of the second alkali solution, the third alkali solution, the fourth alkali solution, the fifth alkali solution, the sixth alkali solution, and the seventh alkali solution are 6000 kg / h, 4000 kg / h, 6000 kg / h, 4000 kg / h, 6000 kg / h, and 4000 kg / h respectively.

[0235] The total removal rate of hydrogen sulfide in the acidic gas in the first reactor 31 is 51.5%.

[0236] A part of the first reaction caustic solution (the first caustic solution) from the first buffer zone of the first reactor 31 enters the upper part of the stripping and evaporation tower 11 after being pressurized by the first reaction first-stage pump 21. The top temperature of the stripping and evaporation tower 11 is 112 °C, the bottom temperature is 126 °C, and the top pressure is 0.1 MPa. And 1.0 MPa saturated steam is used as the heat source to enter the lower part of the stripping and evaporation tower 11. Under the continuous heating of the heat source, impurities such as ammonia and oil carried by the first reaction caustic solution are stripped out due to heat, and part of the water is also vaporized due to heat. Therefore, the first reaction caustic solution is concentrated, and finally a sodium hydrosulfide liquid product with a mass flow rate of 5622.7 kg / h is obtained at the bottom of the stripping and evaporation tower 11, and the mass fractions of sodium hydrosulfide, sodium sulfide, sodium bicarbonate, and sodium carbonate are 33.6%, 0.6%, 0.2%, and 0.1% respectively. Its concentration, impurities and other indicators meet the requirements of the "32% (liquid)" grade index of the "Industrial Sodium Hydrosulfide" GB / T 23937-2020 standard.

[0237] The first reaction tertiary purified gas and the second reaction mixed liquid from the first reactor 31 respectively enter the connecting pipe between the first valve 324 and the second valve 325 of the second reactor 32. Open the first valve 324, the fourth valve 327, and the sixth valve 329, and close the second valve 325, the third valve 326, and the fifth valve 328. The reaction materials react successively in the fourth reaction section 321 and the fifth reaction section 322. The inlet temperature of the fourth reaction section 321 is 50 °C and the inlet pressure is 0.56 MPa; the inlet temperature of the fifth reaction section 322 is 55 °C and the inlet pressure is 0.55 MPa. The fourth reaction section 321 and the fifth reaction section 322 select SL type static mixers, the length / diameter ratio is set to 9.8, the gas-liquid volume ratio is controlled within the range of 6-12, the pH value is controlled within the range of 10-12, and the apparent linear velocity of the mixture composed of the first reaction tertiary purified gas and the second reaction mixed liquid is controlled within 8.0 m / s - 11.0 m / s; the gas-liquid two-phase contact time is 0.08 s - 1.10 s. In the second reaction mixed liquid, the flow rates of the eighth caustic solution from the second reaction pump 24 and the eleventh caustic solution from the third reaction pump 25 are 6000 kg / h and 200 kg / h respectively. In the second reactor 32, the total removal rate of hydrogen sulfide in the acid gas is 44.5%.

[0238] In the third reactor 33, the second reaction purified gas enters the eighth reaction section 333, the seventh reaction section 332, and the sixth reaction section 331 from bottom to top in turn, and contacts countercurrently with the ninth caustic solution, the tenth caustic solution, and the third reaction prepared caustic solution respectively, and further removes the hydrogen sulfide contained in the second reaction purified gas to 12 mg / m 3 , and then mixes with the stripping tail gas from the top of the stripping and evaporation tower 11 as the third reaction purified gas to enter the ammonia absorption tower 12 as a mixed gas. Operating conditions of the third reactor 33:

[0239] The operating temperature of the sixth reaction section 331 is 55 °C and the operating pressure is 0.53 MPa.

[0240] The operating temperature of the seventh reaction section 332 is 40 °C to 55 °C and the operating pressure is 0.52 MPa.

[0241] The operating temperature of the eighth reaction section 333 is 40 °C to 55 °C and the operating pressure is 0.51 MPa.

[0242] The flow rates of the ninth lye, tenth lye, eleventh lye, and the third product are 3000 kg / h, 3000 kg / h, 200 kg / h, and 0 kg / h respectively.

[0243] The mixed gas obtained by fully mixing the third reaction purified gas from the third reactor 33 and the stripping tail gas from the stripping evaporation tower 11 is further mixed with the second tail gas from the top of the ammonia rectification tower 13, and then enters the lower part of the second absorption section 122 of the ammonia absorption tower 12 from bottom to top, and countercurrently contacts with the first absorption liquid from the ammonia water pump 26. 90% of the ammonia in the mixed gas is absorbed by the first absorption liquid, and then the mixed gas enters the first absorption section 121, where it countercurrently contacts with the deoxygenated water with a temperature of 20 °C from the battery limit, and the contained ammonia gas is removed to 30 mg / m 3 , and then is output as the first tail gas to the outside of the system. The hydrogen sulfide content in the first tail gas is not more than 20 mg / m 3 , meeting the specific index requirements.

[0244] Operating conditions of the ammonia absorption tower 12: the top operating temperature is 40 °C, the bottom operating temperature is 45 °C, and the top operating pressure is 0.50 MPa; the mass flow rate of the first absorption liquid is 3500 kg / h, and the deoxygenated water with a temperature of 20 °C is used as the deoxygenated water for configuration, and the mass flow rate of the deoxygenated water for configuration is 3100 kg / h.

[0245] The second absorption liquid from the ammonia water pump 26 enters the ammonia rectification tower 13. Under the action of rectification, the trace hydrogen sulfide, light hydrocarbons, carbon dioxide, and part of water and ammonia contained in the second absorption liquid move upward as light components to the upper part of the tower and are distilled out at the top of the tower, serving as the second tail gas to enter the mixed gas pipeline and enter the ammonia absorption tower 12 together with the mixed gas; while the remaining ammonia-containing liquid of the second absorption liquid continues to move to the bottom of the tower, and finally a second product with a mass flow rate of 3530 kg / h, an ammonia mass fraction of 20%, and a hydrogen sulfide content of 7.0 mg / kg is obtained at the bottom of the tower. The second product is ammonia water and can be output as a product to the outside.

[0246] Operating conditions of the ammonia rectification tower 13: the top operating temperature is 40 °C, the bottom operating temperature is 156 °C, and the top operating pressure is 1.2 MPa.

[0247] Example 2

[0248] It is required that the hydrogen sulfide content in the first tail gas be reduced from not more than 20 mg / m in Example 1 3 to not more than 5 mg / m 3 , and the others are the same as in Example 1.

[0249] Based on Example 1, the measures taken are as follows: keep the alkali flow rate of the second reaction configuration at 4290.8 kg / h unchanged, increase the alkali flow rate of the third reaction configuration from 202.2 kg / h to 510 kg / h, and at the same time output 300 kg / h of the third product out of the system. The third product is used to transfer excess impurities such as sodium sulfide and sodium carbonate in the system out of the system. After the third product is output from the system, it can be used for alkali injection into the main stripping tower of other systems such as the sour water stripping unit. The effect after the above measures are implemented is that the hydrogen sulfide content in the first tail gas output from the system is reduced to 7.6 mg / m 3 ; in the sodium hydrosulfide product produced, the mass fractions of sodium hydrosulfide, sodium sulfide, sodium bicarbonate, and sodium carbonate are 33.9%, 0.4%, 0.1%, and 0.1% respectively; in the ammonia product produced, the mass fraction of ammonia is 20% and the hydrogen sulfide content is 4.9 mg / kg. All three products output to the outside meet the relevant index requirements.

[0250] Example 3

[0251] The volume content of carbon dioxide in the acid gas is increased from 3.3% in Example 1 to 10%, and the volume content of ammonia is correspondingly reduced, and the others are the same as in Example 1.

[0252] When producing sodium hydrosulfide products according to the operating conditions described in Example 1, due to the significant increase in the volume content of carbon dioxide in the acid gas, the mass fractions of sodium bicarbonate and sodium carbonate in the sodium hydrosulfide product increase to 2.9% and 1.4% respectively. To solve the above problems, the measures taken based on Example 1 are as follows:

[0253] (1) Increase the operating temperatures of the first reaction column 311, the second reaction column 312, and the third reaction column 313 of the first-stage reactor from 70°C, 65°C, and 60°C in Example 1 to 75°C, 70°C, and 65°C respectively;

[0254] (2) In the second reactor 32, only open the first valve 324 and the fifth valve 328, close other valves, and the reaction materials only react in the fourth reaction section 321;

[0255] (3) Change the discharge of the third reactor 33 from all being output as the eleventh alkali solution to the second reactor 32 in Example 1 to all being output as the third product out of the system. After the above measures are implemented, the mass fractions of sodium bicarbonate and sodium carbonate in the sodium hydrosulfide product are reduced to 0.2% and 0.1% respectively.

[0256] In summary, the method for producing sodium hydrosulfide using acidic gas provided by the embodiments of the present application can resourcefully utilize acidic gas, ensure that the hydrogen sulfide content in the purified gas output to the outside of the system is less than 20 mg / Nm 3 or meet the specified index requirements, effectively remove impurities such as oils and ammonia in the liquid sodium hydrosulfide product, and can produce ammonia water. The overall system has the characteristics of high resource utilization degree, high selectivity of sodium hydrosulfide, simple process, flexible operation, and low equipment and operation costs.

[0257] The various embodiments of the present application may exist in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be construed as a rigid limitation on the scope of the present application; therefore, it should be considered that the described range description has specifically disclosed all possible sub-ranges and single values within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within that range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any cited number (fraction or integer) within the indicated range.

[0258] In the present application, unless otherwise stated, the orientation terms such as "upper" and "lower" specifically refer to the drawing direction in the drawings. Additionally, in the description of the specification of the present application, the terms "including", "comprising", etc. mean "including but not limited to". In this document, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this document, "and / or" describes the associated relationship of associated objects and indicates that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. Where A and B can be singular or plural. In this document, "at least one" means one or more, and "a plurality" means two or more. "At least one kind", "at least one of the following (items)", or similar expressions refer to any combination of these items, including any combination of single (item) or plural (items). For example, "at least one of (a, b, or c)", or, "at least one of (a, b, and c)" can both represent: a, b, c, a - b (i.e., a and b), a - c, b - c, or a - b - c, where a, b, and c can be single or multiple respectively.

[0259] The above are only specific embodiments of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but rather to the broadest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for producing sodium hydrosulfide using acidic gas, characterized in that, the method comprises: using a first reaction mixture to conduct a first reaction on acidic gas in a gradient countercurrent contact manner to absorb sulfur-containing gas in the acidic gas, and respectively obtaining a first mixture and a first reaction purified gas, and then performing gas-liquid separation on the first mixture to obtain a first reaction alkali liquor; performing stripping evaporation on a part of the first reaction alkali liquor to respectively obtain a first product and a stripping tail gas; using a second reaction mixture to mix with the first reaction purified gas and conducting a second reaction to obtain a second mixture; performing gas-liquid separation on the second mixture to respectively obtain a second reaction alkali liquor and a second reaction purified gas; using a third reaction mixture to conduct a hydrogen sulfide removal reaction on the second reaction purified gas to respectively obtain a third mixture and a third reaction purified gas, and then performing gas-liquid separation on the third mixture to obtain a third reaction alkali liquor; mixing the third reaction purified gas and the stripping tail gas to obtain a mixed gas; judging whether ammonia absorption treatment is needed according to the ammonia content in the mixed gas; if the volume fraction of ammonia in the mixed gas ≥ 5%, then performing ammonia absorption treatment on the mixed gas to respectively obtain a second product and an exhaust gas; outputting the first product to obtain a sodium hydrosulfide product; wherein, the first reaction mixture comprises another part of the first reaction alkali liquor and a part of the second reaction alkali liquor, the second reaction mixture comprises another part of the second reaction alkali liquor and a second reaction prepared alkali liquor, and the third reaction mixture comprises the third reaction alkali liquor and a third prepared alkali liquor; the second reaction prepared alkali liquor and the third prepared alkali liquor are respectively aqueous solutions of alkaline substances.

2. The method according to claim 1, characterized in that, the step of using a first reaction mixture to conduct a first reaction on acidic gas in a gradient countercurrent contact manner to absorb sulfur-containing gas in the acidic gas, and obtaining a first mixture and a first reaction purified gas, and then performing gas-liquid separation on the first mixture to obtain a first reaction alkali liquor includes the steps: using a first reaction first-stage mixture to conduct a first-stage reaction on acidic gas in a countercurrent contact manner to respectively obtain a first reaction first-stage mixture and a first reaction first-stage purified gas; performing gas-liquid separation on the first reaction first-stage mixture to obtain a first reaction first-stage alkali liquor; boosting the pressure of the first reaction first-stage alkali liquor to respectively obtain a first alkali liquor and a second alkali liquor; using a first reaction second-stage mixture to conduct a second-stage reaction on the first reaction first-stage purified gas in a countercurrent contact manner to respectively obtain a first reaction second-stage mixture and a first reaction second-stage purified gas; performing gas-liquid separation on the first reaction second-stage mixture to obtain a first reaction second-stage alkali liquor; boosting the pressure and performing first cooling on the first reaction second-stage alkali liquor to respectively obtain a third alkali liquor and a fourth alkali liquor; using a first reaction third-stage mixture to conduct a third-stage reaction on the first reaction second-stage purified gas in a countercurrent contact manner to respectively obtain a first reaction third-stage mixture and a first reaction purified gas; performing gas-liquid separation on the first reaction third-stage mixture to obtain a first reaction third-stage alkali liquor; The first reaction tertiary caustic solution is pressurized and secondarily cooled to obtain a fifth caustic solution and a sixth caustic solution respectively; Among them, the first reaction caustic solution includes a first reaction primary caustic solution, a first reaction secondary caustic solution, and a first reaction tertiary caustic solution; The first reaction primary mixed solution is a mixed solution of the second caustic solution and the third caustic solution, the first reaction secondary mixed solution is a mixed solution of the fourth caustic solution and the fifth caustic solution, and the first reaction tertiary mixed solution is a mixed solution of the sixth caustic solution and a part of the second reaction caustic solution.

3. The method according to claim 2, characterized in that, the temperature of the first-stage reaction is 50°C to 80°C, and the pressure of the first-stage reaction ≥ 0.10 MPa; the temperature of the second-stage reaction is 45°C to 70°C, and the pressure of the second-stage reaction ≥ 0.09 MPa; the temperature of the third-stage reaction is 40°C to 65°C, and the pressure of the third-stage reaction ≥ 0.08 MPa.

4. The method according to claim 2, characterized in that, the second mixture is subjected to gas-liquid separation to obtain a second reaction caustic solution and a second reaction purified gas respectively, and then the following steps are included: the second reaction caustic solution is pressurized and thirdly cooled to obtain a seventh caustic solution and an eighth caustic solution respectively; among them, the seventh caustic solution and the sixth caustic solution are mixed to form the first reaction tertiary mixed solution; the eighth caustic solution and the second reaction prepared caustic solution are mixed to form the second reaction mixed solution.

5. The method according to claim 2, characterized in that, the third reaction mixed solution is used to carry out a hydrogen sulfide removal reaction on the second reaction purified gas to obtain a third mixture and a third reaction purified gas respectively, the third mixture is subjected to gas-liquid separation to obtain a third reaction caustic solution, and then the following steps are included: the third reaction caustic solution is pressurized and fourthly cooled to obtain a ninth caustic solution, a tenth caustic solution and a third mixed product respectively, where the third mixed product includes an eleventh caustic solution and / or a third product; the ninth caustic solution and the tenth caustic solution are respectively mixed with the third prepared caustic solution to form the third reaction mixed solution; the sum of the flow rates of the eleventh caustic solution and the third product is the same as the flow rate of the third reaction prepared caustic solution after the reaction.

6. A system for producing sodium hydrosulfide using acidic gas, characterized in that, the system is adapted to the method according to any one of claims 1-5, and the system includes: a reaction section, the reaction section includes a first reactor (31), a second reactor (32) and a third reactor (33), the first reactor (31) is provided with an air inlet to enable acidic gas to enter the system, the air outlet of the first reactor (31) is communicated with the second reactor (32), and the air outlet of the second reactor (32) is communicated with the third reactor (33); a stripping evaporation tower (11), the liquid inlet of the stripping evaporation tower (11) is communicated with the liquid outlet of the first reactor (31); A reaction pump group, the reaction pump group includes a first reaction pump, a second reaction pump (24) and a third reaction pump (25), both ends of the first reaction pump are respectively communicated with the top and bottom of the first reactor (31), both ends of the second reaction pump (24) are respectively communicated with the top and bottom of the second reactor (32), and both ends of the third reaction pump (25) are respectively communicated with the top and bottom of the third reactor (33); A cooling part, the cooling part is arranged in the first reactor (31).

7. The system according to claim 6, characterized in that, the first reactor (31) includes a first reaction column (311), a second reaction column (312), a third reaction column (313) and a first buffer tank (314); the first reaction column (311) includes a first reaction section (3111) and a first connecting pipe (3112), the second reaction column (312) includes a second reaction section (3121) and a second connecting pipe (3122), the third reaction column (313) includes a third reaction section (3131) and a third connecting pipe (3132), the first reaction column (311) is communicated with the first buffer tank (314) through the first connecting pipe (3112), the second reaction column (312) is communicated with the first buffer tank (314) through the second connecting pipe (3122), and the third reaction column (313) is communicated with the first buffer tank (314) through the third connecting pipe (3132); A first partition plate (3141) and a second partition plate (3142) are arranged in the first buffer tank (314) to cooperate with the first connecting pipe (3112), the second connecting pipe (3122) and the third connecting pipe (3132) to form a first buffer area, a second buffer area and a third buffer area.

8. The system according to claim 7, characterized in that, the first reaction pump includes a first reaction primary pump (21), a first reaction secondary pump (22) and a first reaction tertiary pump (23); one end of the first reaction primary pump (21) is communicated with the first buffer area of the first buffer tank (314), and the other end of the first reaction primary pump (21) is respectively communicated with the first reaction section (3111) and the stripping evaporation tower (11); one end of the first reaction secondary pump (22) is communicated with the second buffer area of the first buffer tank (314), and the other end of the first reaction secondary pump (22) is respectively communicated with the first reaction section (3111) and the second reaction section (3121); one end of the first reaction tertiary pump (23) is communicated with the third buffer area of the first buffer tank (314), and the other end of the first reaction tertiary pump (23) is respectively communicated with the second reaction section (3121) and the third reaction section (3131).

9. The system according to claim 8, characterized in that, The cooling section includes a first cooler (41), a second cooler (42), a third cooler (43) and a fourth cooler (44). The first cooler (41) is provided at the discharge end of the first reaction secondary pump (22), the second cooler (42) is provided at the discharge end of the first reaction tertiary pump (23), the third cooler (43) is provided at the discharge end of the second reaction pump (24), and the fourth cooler (44) is provided at the discharge end of the third reaction pump (25).

10. The system according to claim 6, wherein, the second reactor (32) includes a fourth reaction section (321), a fifth reaction section (322), a second buffer tank (323) and a valve group. The liquid discharge ends of the fourth reaction section (321) and the fifth reaction section (322) are connected to the second buffer tank (323), and the fourth reaction section (321) and the fifth reaction section (322) are respectively connected to the gas outlet of the first reactor (31); the fourth reaction section (321) and the fifth reaction section (322) are connected by the valve group to enable series connection, parallel connection or independent operation between the fourth reaction section (321) and the fifth reaction section (322).

11. The system according to claim 10, wherein, the valve group includes a first valve (324), a second valve (325), a third valve (326), a fourth valve (327), a fifth valve (328) and a sixth valve (329). The tops of the fourth reaction section (321) and the fifth reaction section (322) are connected by the first valve (324) and the second valve (325), the bottoms of the fourth reaction section (321) and the fifth reaction section (322) are connected by the fifth valve (328) and the sixth valve (329), the top of the fourth reaction section (321) and the bottom of the fifth reaction section (322) are connected by the third valve (326), and the top of the fifth reaction section (322) and the bottom of the fourth reaction section (321) are connected by the fourth valve (327).

12. The system according to claim 6, wherein, the third reactor (33) includes a sixth reaction section (331), a seventh reaction section (332), an eighth reaction section (333) and a third buffer tank (334). The gas outlet of the second reactor (32) is connected to the bottom of the eighth reaction section (333), the liquid inlet end of the third reaction pump (25) is connected to the bottom of the third buffer tank (334), and the liquid discharge end of the third reaction pump (25) is respectively provided between the sixth reaction section (331) and the seventh reaction section (332) and between the seventh reaction section (332) and the eighth reaction section (333).

13. The system according to claim 6, wherein, the system further includes: An ammonia treatment unit, the ammonia treatment unit includes an ammonia absorption tower (12), an ammonia rectification tower (13) and an ammonia water pump (26). The intake end of the ammonia absorption tower (12) is respectively connected to the outlet of the stripping evaporation tower (11) and the outlet of the third reactor (33). The liquid outlet end of the ammonia absorption tower (12) is connected to the liquid inlet end of the ammonia water pump (26). The liquid outlet end of the ammonia water pump (26) is respectively connected to the liquid inlet ends of the ammonia absorption tower (12) and the ammonia rectification tower (13).

14. The system according to claim 13, wherein, the ammonia absorption tower (12) sequentially includes a first absorption section (121), a second absorption section (122) and an absorption liquid buffer tank (123) from top to bottom. The liquid outlet end of the ammonia water pump (26) is arranged between the first absorption section (121) and the second absorption section (122). The outlet of the stripping evaporation tower (11) is connected to the top of the absorption liquid buffer tank (123). The bottom of the absorption liquid buffer tank (123) is connected to the liquid inlet end of the ammonia water pump (26).

15. The system according to claim 14, wherein, the ammonia rectification tower (13) includes a condensation section (131), a first separation section (132), a second separation section (133) and a reboiler (134) from top to bottom. The liquid outlet end of the ammonia water pump (26) is arranged between the first separation section (132) and the second separation section (133). The reboiler (134) is arranged at the bottom of the ammonia rectification tower (13).

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