Ammonia-containing tail gas treatment system and method for ultra-pure ammonia production

Abstract

The present invention discloses a treatment system and method for ammonia-containing tail gas in ultra-pure ammonia production, including an ammonia-containing tail gas pretreatment system and an atmospheric-pressure ammonia gas absorption system. The ammonia-containing tail gas pretreatment system includes a high-pressure buffer tank, a low-pressure buffer tank, and an ammonia gas condenser. The high-pressure buffer tank receives ammonia sources of various high-pressure ammonia-containing tail gases in the ultra-pure ammonia production system and is connected to the inlet end of the tube side of the ammonia gas condenser. The liquid outlet end of the tube side of the ammonia gas condenser is connected to the high-pressure buffer tank through a condensate ammonia return pipeline; the low-pressure buffer tank receives ammonia sources of various low-pressure ammonia-containing tail gases in the ultra-pure ammonia production system and is connected to the outlet end of the tube side of the ammonia gas condenser, and the ammonia gas in the low-pressure buffer tank is transported to the atmospheric-pressure ammonia gas absorption system for absorption treatment; the overpressure ammonia gas produced by the high-pressure buffer tank and the low-pressure buffer tank is emergently discharged for system pressure relief, and the liquid ammonia produced is used as a refrigerant for heat exchange. The present invention can fully recover the ammonia-containing tail gas in the ultra-pure ammonia production system, achieving zero emission of ultra-pure ammonia tail gas.

Description

Technical Field

[0001] The present invention belongs to the technical field of ultra-pure ammonia production, and particularly relates to a treatment system and method for ammonia-containing tail gas in ultra-pure ammonia production. Background Art

[0002] The main processes for soda ash manufacturing include the combined soda process, the ammonia-soda process, and the natural soda process. The combined soda process for soda ash production uses the concentrated gas soda-making process. The process description is that carbon dioxide reacts with ammonia, salt, and water in a carbonation tower to generate a crystal slurry of sodium bicarbonate and ammonium chloride, which is filtered and calcined to produce soda ash. The filtrate is subjected to cold crystallization and salt crystallization to produce ammonium chloride, which is then dried to produce dry ammonium. Its raw materials are NaCl (wet salt), NH3 (liquid ammonia), H2O, and CO2 (gas). This process has a single salt addition, two ammonia absorptions, a single carbonation, and a circulating mother liquor system to form a circular reaction system. The single salt addition in the combined soda process means that in the entire circulation process, raw material salt (NaCl) is added only at a specific step, which usually occurs after the carbonation process and is used to produce ammonium chloride. Specifically, during the carbonation process, ammoniated brine (obtained by further treating the reaction product of ammonia, water, and carbon dioxide to form ammonium carbonate) reacts with carbon dioxide to form sodium bicarbonate precipitate and ammonium chloride. At this time, in order to supplement the chloride ions consumed due to the formation of ammonium chloride, raw material salt needs to be added to maintain the ion balance in the solution and ensure the continuous progress of the cycle. The two ammonia absorptions are a key step in the combined soda process, which helps to optimize the reaction conditions and improve the product purity and yield. Specifically, the two ammonia absorptions are carried out in two different stages: the first ammonia absorption is to supplement a part of ammonia gas to the mother liquor before or during the carbonation process. The main purpose of this step is to increase the ammonia concentration in the mother liquor and provide sufficient ammonia source for the subsequent carbonation reaction. By increasing the ammonia concentration in the mother liquor, the formation of ammonium bicarbonate can be promoted, which is beneficial to the precipitation and separation of sodium bicarbonate. The second ammonia absorption is to add ammonia gas again to the mother liquor (which already contains ammonium chloride) obtained after filtration and separation after the carbonation process. The main purpose of this step is to supplement the ammonia consumed due to the formation of ammonium chloride and adjust the ammonia concentration in the mother liquor to prepare for the subsequent cyclic production. By the second ammonia absorption, the ammonia concentration in the mother liquor can be maintained within an appropriate range, thus ensuring the stability and high efficiency of the entire cyclic production.

[0003] The production raw materials for the combined soda process are CO2, NH3, NaCl, and H2O. The main reaction equations are as follows:

[0004] NaCl (liquid) + NH3 (liquid) + H2O (liquid) + CO2 (gas) = NaHCO3 (solid) + NH4Cl (liquid);

[0005] 2NaHCO3 (solid) = Na2CO3 (solid) + CO2 (vapor) + H2O↑ (vapor).

[0006] The combined soda-making process is generally equipped with a thermoelectric system for heat and power supply, a synthetic ammonia system for supplying raw material gas CO2 (gas), raw material NH3, and a vacuum salt-making system for supplying raw material NaCl. Our company deeply processes the raw material NH3 to further extend the industrial chain. The NH3 with a content of 99.9% in the components is further purified to produce electronic-grade ammonia with a raw material NH3 content of more than 99.99999%. Electronic-grade ultra-pure ammonia is an important raw material in optoelectronic and microelectronic fields such as semiconductor lighting, integrated circuits, flat panel display panels, and solar cells. In the process of manufacturing solar cells and LED chips, ultra-pure ammonia is required as a nitrogen source. Especially in the process of growing LED chips, the higher the ammonia purity of the raw material, the lower the power consumption of the prepared LED and the greater the luminous intensity. In addition, ultra-pure ammonia is also an important basic material for preparing gallium nitride (GAN) by MOCVD technology. Gallium nitride, as an important material for the third-generation semiconductors, has a wide range of applications. 7N electronic-grade ultra-pure ammonia is also widely used in optoelectronic fields such as liquid crystal display (LCD) and organic electroluminescent display (OLED). Its quality directly affects the optical and electrical properties of the materials and even the service life of the devices, and is an important link in the development of the industrial chain.

[0007] The existing treatment process for ultra-pure ammonia tail gas: The ammonia-containing tail gas first enters the first tail gas absorption tower and is absorbed by spraying through a circulating pump. The high-concentration (below 20%) ammonia water is pumped into the ammonia water storage tank by the circulating ammonia water pump and then transported to the combined soda ammonia water tank by the transfer pump. The unabsorbed ammonia gas passes through the second tail gas absorption tower. The function of this tower is designed as a packing and spraying group and grading type. The ammonia-containing tail gas first fully contacts and absorbs with the liquid phase in the tower bottom, then enters the first-stage packing function section, and is subjected to the first-stage circulating spraying through the circulating liquid, so that the gas-liquid two phases are in full contact for the third time. Through continuous circulating absorption, at the same time, the low-concentration ammonia water (below 5%) is transported to the first tail gas absorption tower by the circulating ammonia water pump as makeup water. The waste gas after multiple treatments enters the second-stage packing demineralized water spraying function section, so that the waste gas can have more sufficient gas-liquid two-phase contact reaction, and at the same time effectively inhibits the volatilization of ammonia water. The tail gas of the absorption tower is discharged up to standard through the exhaust stack.

[0008] The main problem existing in the above ammonia-containing tail gas treatment process is that both of the two series-connected tail gas absorption towers cool down through circulating water to promote the absorption of ammonia tail gas. The water absorption of ammonia in the tail gas treatment system is an exothermic reaction, and 87.8 kcal (Note: 1 kcal = 4.17 kJ) of dissolution heat will be released for every 1 kg of ammonia absorbed. Therefore, this part of heat must be transferred in time during the treatment process, and the ammonia absorption temperature should be controlled according to the equilibrium curve of water absorption of ammonia to ensure the efficient reaction of ammonia and water and make the ammonia water reach the target concentration. In the current tail gas circulation washing and absorption process, circulating water is used to transfer this part of the dissolution heat through a shell-and-tube heat exchanger, and ammonia water with a concentration of 20% is produced for the desulfurization and denitrification of thermal power plants. The tail gas treatment system requires that the ammonia content in the exhaust gas discharged after the tail gas is treated can meet the national emission standards. According to the Odor Pollutant Emission Standard (GB 14554-93), when the chimney height of the organized emission of ammonia gas is 15 m, the emission standard is ≤ 4.9 kg / h. However, the circulating water temperature is high and the heat exchange effect is poor during the operation of this tail gas treatment system in summer, and the treatment capacity of the two tail gas absorption towers decreases. This requires reducing the treatment intensity of the ammonia absorption tower and increasing the intensity of the heat exchange process to ensure that all indicators meet the process requirements during the operation process. This will greatly increase the energy consumption of the tail gas treatment system and there is a risk of excessive ammonia content in the tail gas being discharged. Summary of the Invention

[0009] Technical problems to be solved: Aiming at the problems existing in the process of treating ammonia-containing tail gas in the background technology, the present invention provides an ammonia-containing tail gas treatment system and method for ultra-pure ammonia production, which fully recovers the ammonia-containing tail gas in the ultra-pure ammonia production system and realizes zero emission of ultra-pure ammonia tail gas.

[0010] Technical solution: An ammonia-containing tail gas treatment system for ultra-pure ammonia production according to the present invention includes an ammonia-containing tail gas pretreatment system and an atmospheric ammonia absorption system;

[0011] The ammonia-containing tail gas pretreatment system includes a high-pressure buffer tank, a low-pressure buffer tank, and an ammonia condenser; a plurality of connection ends communicating with each high-pressure ammonia-containing tail gas ammonia source in the ultra-pure ammonia production system are arranged on the high-pressure buffer tank, and one connection end is communicated with the tube-side inlet end of the ammonia condenser through a high-pressure buffer tank evaporation ammonia gas pipeline, and the tube-side liquid outlet end of the ammonia condenser is connected to one connection end of the high-pressure buffer tank through a condensate ammonia return pipeline;

[0012] A connection end communicating with each low-pressure ammonia-containing tail gas ammonia source in the ultra-pure ammonia production system is arranged on the low-pressure buffer tank, and one connection end is communicated with the tube-side outlet end of the ammonia condenser through an ammonia gas from ammonia condenser to low-pressure buffer tank pipeline, and the ammonia gas in the low-pressure buffer tank is transported to the atmospheric ammonia absorption system for absorption treatment;

[0013] The overpressure gaseous ammonia produced by the high-pressure buffer tank and the low-pressure buffer tank is emergently discharged to the ultra-pure ammonia production system or the soda ash production system as gaseous ammonia raw material, and the liquid ammonia produced by the high-pressure buffer tank and the low-pressure buffer tank is transported to the external cooler of the soda ash crystallization process as a refrigerant for heat exchange.

[0014] Preferably, the atmospheric-pressure gaseous ammonia absorption system includes a jet ammonia absorber, an ammonia induced draft fan, an ammonia II distribution tank, and at least one ammonia II clarification tank;

[0015] The liquid inlet end of the jet ammonia absorber is connected to the mother II conveying pipeline and receives the mother II liquid, and the gas inlet end of the jet ammonia absorber is connected to the ammonia induced draft fan and receives the gaseous ammonia from the low-pressure buffer tank;

[0016] The liquid outlet end of the jet ammonia absorber is connected to the ammonia II distribution tank through a conveying pipeline, and the liquid outlet end of the ammonia II distribution tank is connected to the ammonia II clarification tank through a conveying pipeline.

[0017] Preferably, the atmospheric-pressure gaseous ammonia absorption system includes a first ammonia II clarification tank and a second ammonia II clarification tank. The liquid inlet end of the first ammonia II clarification tank is connected to the liquid outlet end of the ammonia II distribution tank. The liquid inlet end of the first ammonia II clarification tank is connected to the liquid inlet end of the second ammonia II clarification tank through an overflow pipe. The liquid outlet end of the second ammonia II clarification tank is connected to the pipeline for sending ammonia to the carbon filtration process.

[0018] Preferably, the conveying pipeline from the ammonia induced draft fan to the jet ammonia absorber is also connected with the gaseous ammonia source pipeline of the external cooling system of the crystallization process.

[0019] The present invention also discloses a method for treating ammonia-containing tail gas in an ultra-pure ammonia production system. The treatment method includes:

[0020] Step 1: The ammonia source producing high-pressure ammonia-containing tail gas in the ultra-pure ammonia production system is transported to the high-pressure buffer tank through the corresponding conveying pipeline, and the ammonia source producing low-pressure ammonia-containing tail gas in the ultra-pure ammonia production system is transported to the low-pressure buffer tank through the corresponding conveying pipeline for ammonia separation;

[0021] Step 2: The evaporated gaseous ammonia in the high-pressure buffer tank is transported to the ammonia condenser. The condensed liquid ammonia produced after being cooled by the refrigerant returns to the high-pressure buffer tank through the condensed liquid ammonia return pipeline. The gaseous ammonia from the ammonia condenser produced after the pressure reduction in the ammonia condenser is transported to the low-pressure buffer tank through the pipeline from the gaseous ammonia of the ammonia condenser to the low-pressure buffer tank for ammonia separation;

[0022] Step 3: The liquid ammonia separated and produced by the high-pressure buffer tank and the low-pressure buffer tank is pumped by an ammonia pump to the external cooler of the crystallization process of the soda ash plant as a refrigerant for the crystallization system;

[0023] Step 4: The atmospheric and low-pressure buffer tank gaseous ammonia produced by the low-pressure buffer tank is pressurized by an ammonia induced draft fan and then enters the jet ammonia absorber to react with the mother liquor II to form ammonia liquor II. The ammonia liquor II flows through the ammonia liquor II distribution tank, the first ammonia liquor II clarifying tank, the overflow pipe and the second ammonia liquor II clarifying tank in sequence and is transported to the carbon filtration system through the ammonia liquor II feeding carbon filtration process pipeline.

[0024] Preferably, the gaseous ammonia produced by the external cooling system of the crystallization process in Step 4 enters the jet ammonia absorber through the gaseous ammonia source pipeline of the external cooling system of the crystallization process together with the gaseous ammonia of the low-pressure buffer tank for ammonia absorption reaction.

[0025] Preferably, the high-pressure ammonia-containing tail gas ammonia source in Step 1 includes one or more of the ammonia sources of the high-boiling tower receiving tank, the low-boiling tower receiving tank, the high-boiling tower ammonia source, the low-boiling tower ammonia source, and the low-boiling tower condenser ammonia source.

[0026] Preferably, the low-pressure ammonia-containing tail gas ammonia source in Step 1 includes one or more of the ammonia sources of the safety valve, the ammonia buffer tank drain ammonia source, the cylinder tail gas ammonia source, the ammonia recovery tank ammonia source, the workshop on-line analysis tail gas ammonia source, and the tank area on-line analysis tail gas ammonia source.

[0027] Preferably, after being pressurized by the ammonia induced draft fan in Step 4, the pressure of the gaseous ammonia in the low-pressure buffer tank is 0.3 - 0.5 MPa.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. The ultra-pure ammonia production system of the present invention can achieve "zero emission" of ammonia tail gas without additionally installing a tail gas treatment system, there is no longer external discharge of the malodorous pollutant ammonia, and it also reduces the problems that are difficult to control during the summer operation of the traditional double-tower water washing for ammonia water preparation system and the subsequent ammonia water sales problem, and there is no need to explore the process conditions for combining with other uses within the factory.

[0030] 2. On the basis of controlling a reasonable ultra-pure ammonia production rate, the working load of the ammonia condenser can be reduced to reduce the power consumption of the refrigerant circulation system to achieve the purpose of energy conservation.

[0031] 3. The double-tower absorption system for preparing ammonia water for external sale or self-use adopted in the industry is cancelled. Description of the Drawings

[0032] Figure 1 is the ammonia source process schematic diagram of the ammonia-containing tail gas treatment system of the present invention;

[0033] Figure 2 is the absorption section process schematic diagram of the ammonia-containing tail gas treatment system of the present invention;

[0034] Figure 3 is the process schematic diagram of the existing soda ash production process by the combined soda process.

[0035] Reference Numerals: 1, high-pressure buffer tank; 2, ammonia source of high-boiling tower receiving tank; 3, ammonia source of low-boiling tower receiving tank; 4, ammonia source of high-boiling tower; 5, ammonia source of low-boiling tower; 6, ammonia source of low-boiling tower condenser; 7, evaporation gas ammonia pipeline of high-pressure buffer tank; 8, ammonia gas condenser; 9, circulating incoming water pipeline; 10, circulating return water pipeline; 11, condensate ammonia return pipeline; 12, liquid ammonia; 13, overpressure gas ammonia; 14, pipeline from ammonia gas condenser to low-pressure buffer tank; 15, low-pressure buffer tank; 16, ammonia source of safety valve; 17, liquid ammonia drainage source of ammonia buffer tank; 18, ammonia source of cylinder tail gas; 19, ammonia source of ammonia recovery tank; 20, ammonia source of on-line analysis tail gas in workshop; 21, ammonia source of on-line analysis tail gas in tank farm; 22, gas ammonia of low-pressure buffer tank; 23, ammonia induced draft fan; 24, pipeline of gas ammonia source for external cooling system in crystallization process; 25, mother II conveying pipeline; 26, jet ammonia absorber; 27, ammonia II liquid; 28, ammonia II distribution tank; 29, first ammonia II clarification tank; 30, overflow pipe; 31, second ammonia II clarification tank; 32, pipeline for sending ammonia II to carbon filtration process. Detailed Embodiments

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be described clearly and completely below with reference to the Figures 1 to 3 drawings shown. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the described embodiments of the present invention fall within the scope of protection of the present invention.

[0037] Embodiment 1: As Figures 1 to 2 shown, an ammonia-containing tail gas treatment system for ultra-pure ammonia production of the present invention includes an ammonia-containing tail gas pretreatment system and an atmospheric pressure gas ammonia absorption system. The ammonia-containing tail gas pretreatment system includes a high-pressure buffer tank 1, a low-pressure buffer tank 15, and an ammonia gas condenser 8. The high-pressure buffer tank 1 is provided with a plurality of connection ends communicating with various high-pressure ammonia-containing tail gas ammonia sources of the ultra-pure ammonia production system. The high-pressure ammonia-containing tail gas ammonia sources include one or more of the ammonia source 2 of the high-boiling tower receiving tank, the ammonia source 3 of the low-boiling tower receiving tank, the ammonia source 4 of the high-boiling tower, the ammonia source 5 of the low-boiling tower, and the ammonia source 6 of the low-boiling tower condenser, and are specifically regulated according to various types of ammonia-containing tail gases produced by the production system. One connection end of the high-pressure buffer tank 1 is communicated with the tube-side inlet end of the ammonia gas condenser 8 through the evaporation gas ammonia pipeline 7 of the high-pressure buffer tank, and the tube-side outlet end of the ammonia gas condenser 8 is connected to one connection end of the high-pressure buffer tank 1 through the condensate ammonia return pipeline 11. The shell side of the ammonia gas condenser 8 is respectively connected to the cooling circulating water through the circulating incoming water pipeline 9 and the circulating return water pipeline 10 to realize the cooling and liquefaction of the gas ammonia by the ammonia gas condenser 8. The evaporation gas ammonia of the high-pressure buffer tank 1 produced during the ammonia separation process in the high-pressure buffer tank 1 is converted into condensate ammonia after passing through the ammonia gas condenser 8 and returns to the high-pressure buffer tank 1, and the gas ammonia of the ammonia gas condenser enters the low-pressure buffer tank 15 through the conveying pipeline to participate in the ammonia separation.

[0038] The low-pressure buffer tank 15 is provided with connection ends that communicate with the ammonia sources of each low-pressure ammonia-containing tail gas in the ultrapure ammonia production system. The low-pressure ammonia-containing tail gas sources include one or more of the safety valve ammonia source 16, the ammonia buffer tank liquid discharge ammonia source 17, the cylinder tail gas ammonia source 18, the ammonia recovery tank ammonia source 19, the workshop on-line analysis tail gas ammonia source 20, and the tank area on-line analysis tail gas ammonia source 21, and are specifically regulated according to various types of ammonia-containing tail gases produced by the production system. One connection end of the low-pressure buffer tank 15 is communicated with the outlet end of the tube side of the ammonia condenser 8 through the ammonia condenser gas ammonia to low-pressure buffer tank pipeline 14, and receives the low-pressure gaseous ammonia produced by the ammonia condenser 8; the gaseous ammonia produced during the ammonia separation process in the low-pressure buffer tank 15 is transported to the atmospheric-pressure gaseous ammonia absorption system for absorption treatment, thereby realizing the full-process recovery of the ammonia-containing tail gas in the ultrapure ammonia production system and achieving zero emission of the ultrapure ammonia tail gas.

[0039] Among them, the overpressure gaseous ammonia 13 produced by the high-pressure buffer tank 1 and the low-pressure buffer tank 15 is emergently discharged to the ultrapure ammonia production system or the combined soda production system as gaseous ammonia raw material. When the high-pressure buffer tank 1 and the low-pressure buffer tank 15 trip due to overload of the ammonia-containing tail gas load during the treatment process, the overpressure gaseous ammonia can be used as the gaseous ammonia raw material of the ultrapure ammonia production system or the combined soda production system, thereby realizing the full-process recovery of the system. The liquid ammonia 12 produced by the high-pressure buffer tank 1 and the low-pressure buffer tank 15 is transported to the external cooler of the combined soda crystallization process as a refrigerant for heat exchange.

[0040] The atmospheric-pressure gaseous ammonia absorption system includes a jet ammonia absorber 26, an ammonia induced draft fan 23, an ammonia II distribution tank 28, and at least one ammonia II clarification tank; the liquid inlet end of the jet ammonia absorber 26 is connected to the mother II conveying pipeline 25 and receives the mother II liquid, and the gas inlet end of the jet ammonia absorber 26 is communicated with the ammonia induced draft fan 23 and receives the low-pressure buffer tank gaseous ammonia 22; the conveying pipeline from the ammonia induced draft fan 23 to the jet ammonia absorber 26 is also connected with the gaseous ammonia source pipeline 24 of the external cooler system of the crystallization process. The gaseous ammonia produced by the external cooler system of the crystallization process and the gaseous ammonia produced by the low-pressure buffer tank 15 enter the jet ammonia absorber 26 together to participate in the absorption reaction.

[0041] The liquid outlet end of the jet ammonia absorber 26 is communicated with the ammonia II distribution tank 28 through a conveying pipeline, and the liquid outlet end of the ammonia II distribution tank 28 is connected to the ammonia II clarification tank through a conveying pipeline. Specifically, the atmospheric-pressure gaseous ammonia absorption system includes a first ammonia II clarification tank 29 and a second ammonia II clarification tank 31. The liquid inlet end of the first ammonia II clarification tank 29 is connected to the liquid outlet end of the ammonia II distribution tank 28. The liquid inlet end of the first ammonia II clarification tank 29 is connected to the liquid inlet end of the second ammonia II clarification tank 31 through an overflow pipe 30, and the liquid outlet end of the second ammonia II clarification tank 31 is connected to the ammonia II feeding carbon filtration process pipeline 32.

[0042] Example 2: The present invention also discloses a method for treating ammonia-containing tail gas in an ultrapure ammonia production system. The treatment method includes:

[0043] 1. Transfer the ammonia sources of the high-pressure ammonia-containing tail gas produced in the ultra-pure ammonia production system to the high-pressure buffer tank 1 through the corresponding conveying pipelines, and transfer the ammonia sources of the low-pressure ammonia-containing tail gas produced in the ultra-pure ammonia production system to the low-pressure buffer tank 15 through the corresponding conveying pipelines for ammonia separation; the ammonia sources of the high-pressure ammonia-containing tail gas include one or more of the ammonia sources in the high-boiling tower receiving tank 2, the low-boiling tower receiving tank 3, the high-boiling tower ammonia source 4, the low-boiling tower ammonia source 5, and the low-boiling tower condenser ammonia source 6, and the ammonia sources of the low-pressure ammonia-containing tail gas include one or more of the ammonia source of the safety valve 16, the ammonia drainage source of the ammonia buffer tank 17, the cylinder tail gas ammonia source 18, the ammonia recovery tank ammonia source 19, the on-site analysis tail gas ammonia source 20 in the workshop, and the on-site analysis tail gas ammonia source 21 in the tank area. The specific types of ammonia sources are determined by the type of ammonia-containing tail gas produced during the production process.

[0044] 2. The condensed liquid ammonia produced after the evaporation gas ammonia in the high-pressure buffer tank 1 is transported to the ammonia condenser 8 and cooled by the refrigerant returns to the high-pressure buffer tank 1 through the condensed liquid ammonia return pipeline 11. The ammonia condenser gas ammonia produced after the pressure reduction in the ammonia condenser 8 is transported to the low-pressure buffer tank 15 through the ammonia condenser gas ammonia to low-pressure buffer tank pipeline 14 to participate in the ammonia separation process.

[0045] 3. The liquid ammonia 12 separated from the high-pressure buffer tank 1 and the low-pressure buffer tank 15 is pumped by an ammonia pump to the external cooler of the crystallization process in the soda ash plant as the refrigerant of the crystallization system, and can also be used as an ammonia source in the soda ash system or the ultra-pure ammonia system.

[0046] 4. The atmospheric pressure low-pressure buffer tank gas ammonia 22 produced by the low-pressure buffer tank 15 is pressurized by the ammonia induced draft fan 23 and enters the jet ammonia absorber 26 together with the gas ammonia produced by the external cooling system of the crystallization process for ammonia absorption reaction. The pressure of the low-pressure buffer tank gas ammonia 22 after being pressurized by the ammonia induced draft fan 23 is 0.3 - 0.5 MPa; it enters the jet ammonia absorber 26 to react with the mother liquor II to form ammonia II solution 27. The ammonia II solution 27 flows through the ammonia II distribution tank 28, the first ammonia II clarification tank 29, the overflow pipe 30 and the second ammonia II clarification tank 31 in sequence and is transported to the carbon filtration system through the ammonia II to carbon filtration process pipeline 32.

[0047] The ammonia-containing tail gas treatment system and method of the present invention are applicable to the second ammonia absorption in the soda ash system of the ammonia-containing tail gas produced by the ultra-pure ammonia production system. Currently, there are about 17 domestic soda ash manufacturers using the ammonia soda process, and the minimum production capacity is 250,000 tons / year. According to the material balance diagram of the ammonia soda process (as Figure 3 shown in and Table 1) and the actual production situation, the ammonia absorption of mother liquor II is basically the same. Using the data of the material balance diagram of 210.4 kg / t, the minimum ammonia absorption capacity of mother liquor II in the domestic soda ash system is 52,600 tons / year, and its demand for gas ammonia far exceeds the possible output of gas ammonia volume of any domestic ultra-pure ammonia production system, and it fully has the ability to treat the ammonia tail gas produced by the ultra-pure ammonia device system.

[0048] Table 1 Material Balance Table of the Dual Alkali Process:

[0049] 。

[0050] The following gives the operation data of our factory in June, July, and August 2024 to illustrate the technical effects of the implementation of the present invention; among them, the production data in June and July are the production data before the implementation of the ammonia-containing tail gas treatment system of the present invention, and the production data in August are the production data after the implementation of the ammonia-containing tail gas treatment system of the present invention. It can be seen by comparison that significant economic benefits have been generated after the implementation of the treatment system of the present invention.

[0051] In June 2024, it operated for 24 days, with raw ammonia: 344.61t, ultra-pure ammonia output: 234.42t, organized tail gas emission port volume: 5.52t, residual liquid industrial ammonia volume: 57.08t, 20% ammonia water volume (already converted according to the raw ammonia concentration): 47.59t. Among them, the residual liquid industrial ammonia has too many light and heavy component impurities discharged from the system and can no longer be used as raw ammonia to return to the system. It is sent to the thermal power plant together with the 20% ammonia water prepared and the 20% ammonia water in the tail gas treatment part for ammonia method desulfurization and denitrification, with power consumption of 1372.63 KWH / T.

[0052] In July 2024, it operated for 31 days, with raw ammonia: 309.38t, ultra-pure ammonia output: 231.29t, organized tail gas emission port volume: 3.89t, residual liquid industrial ammonia volume: 36.74t, 20% ammonia water volume already converted according to the raw ammonia concentration: 37.46t. Among them, the residual liquid industrial ammonia has too many light and heavy component impurities discharged from the system and can no longer be used as raw ammonia to return to the system. It is sent to the thermal power plant together with the 20% ammonia water prepared and the 20% ammonia water in the tail gas treatment part for ammonia method desulfurization and denitrification, with power consumption of 1069.11 KWH / T.

[0053] In August 2024, it operated for 31 days, with raw ammonia: 396.69t, ultra-pure ammonia output: 341.98t, organized tail gas emission port volume: 0t, residual liquid industrial ammonia volume: 54.71t. After debugging, the gaseous ammonia is directly sent by the ammonia induced draft fan 23 to the jet ammonia absorber in the crystallization process of the dual alkali plant for ammonia absorption. Part of the residual liquid industrial ammonia is directly sent to the dual alkali crystallization process as the cooling ammonia for system temperature reduction, with power consumption of 1033.11 KWH / T.

[0054] According to the operation conditions of the above three months, the output rate of ultra-pure ammonia in June was 68.02%, in July was 74.76%, and in August was 86.21%. After the implementation of the present invention, the output rate of ultra-pure ammonia has been significantly improved, and no more ammonia water is produced. The dual-tower absorption ammonia water preparation system has stopped operating, and the electricity consumption of the entire ultra-pure ammonia production system has decreased from 1372.63 KWH / T in June to 1033.11 KWH / T in August.

[0055] Based on the test and production operation data in August 2023, the operation results under different loads are provided. The produced ultra-pure ammonia products are qualified (as shown in Table 2), and their overall quality is better than the group standard T∕CCGA 30001-2019, meeting the user's requirements and having stable quality.

[0056] Table 2 Ultra-pure ammonia product detection data:

[0057] 。

[0058] According to the on-site measurement data report of a third-party company, Jiangsu Lantian Environmental Detection Technology Company, on July 30, 2024, report number: LTJ24014-3, the emission rates are 0.018 kg / h, 0.020 kg / h, and 0.017 kg / h. The emission rate of the organized ammonia-containing tail gas at the emission port is reduced from 0.018 kg / h before implementation to 0 kg / h after implementation (the "Odor Pollutant Discharge Standard" (GB14554-1993 ≤ 0.6 kg / h, the emission port height is 15 m). Calculated based on the annual operation of the ultra-pure ammonia production system for 8,000 hours, only the recovery of tail gas emissions can achieve an ammonia reduction of 144 Kg / a in the ultra-pure ammonia system.

[0059] The ultra-pure ammonia production system of the present invention can also achieve "zero emission" of ammonia tail gas without additional installation of a tail gas treatment system, no longer having external emissions of the odor pollutant ammonia, and also reducing the problems that are difficult to control during the summer operation of the traditional two-tower water washing ammonia preparation system and the subsequent ammonia water sales problems, without the need to explore the process conditions for other uses within the factory. On the basis of controlling a reasonable ultra-pure ammonia production rate, the working load of the ammonia condenser 8 can be reduced to reduce the power consumption of the refrigerant circulation system to achieve the purpose of energy conservation. In addition, the two-tower absorption ammonia preparation system for external sales or self-use adopted in the industry is cancelled.

[0060] The above is the preferred implementation mode of the present invention. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. An ammonia-containing tail gas treatment system for ultrapure ammonia production, characterized in that: It includes an ammonia-containing tail gas pretreatment system and a normal pressure gas ammonia absorption system; The ammonia-containing tail gas pretreatment system comprises a high-pressure buffer tank (1), a low-pressure buffer tank (15), and an ammonia condenser (8); the high-pressure buffer tank (1) is provided with a plurality of connection ends connected to ammonia sources of high-pressure ammonia-containing tail gases of an ultra-pure ammonia production system, one of the connection ends being connected to a tube-side gas inlet end of an ammonia condenser (8) via a high-pressure buffer tank evaporation gas ammonia pipeline (7), and a tube-side liquid outlet end of the ammonia condenser (8) being connected to a connection end of the high-pressure buffer tank (1) via a condensate ammonia return pipeline (11); The low-pressure buffer tank (15) is provided with a connection end connected to each low-pressure ammonia-containing tail gas ammonia source of the ultra-pure ammonia production system, one of the connection ends is connected to the pipe-side gas outlet end of the ammonia condenser (8) through the ammonia condenser gas ammonia to low-pressure buffer tank pipeline (14), and the low-pressure buffer tank gas ammonia (22) is transported to the atmospheric pressure gas ammonia absorption system for absorption treatment; The overpressure gas ammonia (13) produced by the high-pressure buffer tank (1) and the low-pressure buffer tank (15) is discharged to the ultra-pure ammonia production system or the combined alkali production system as a gas ammonia raw material in an emergency manner, and the liquid ammonia (12) produced by the high-pressure buffer tank (1) and the low-pressure buffer tank (15) is transported to the external cooler of the combined alkali crystallization process as a refrigerant for heat exchange; The atmospheric pressure gas ammonia absorption system comprises a jet ammonia absorber (26), an ammonia induced draft fan (23), an ammonia II distribution tank (28) and at least one ammonia II clarification tank; The liquid inlet end of the jet ammonia absorber (26) is connected to the mother II delivery pipeline (25) and receives the mother II liquid, and the gas inlet end of the jet ammonia absorber (26) is connected to the ammonia induced draft fan (23) and receives the gas ammonia (22) from the low-pressure buffer tank; The liquid outlet end of the jet ammonia absorber (26) is connected to the ammonia II distribution tank (28) through a delivery pipeline, and the liquid outlet end of the ammonia II distribution tank (28) is connected to the ammonia II clarification tank through a delivery pipeline; The atmospheric pressure gas ammonia absorption system comprises a first ammonia II clarification tank (29) and a second ammonia II clarification tank (31), wherein the liquid inlet end of the first ammonia II clarification tank (29) is connected to the liquid outlet end of the ammonia II distribution tank (28), the liquid inlet end of the first ammonia II clarification tank (29) is connected to the liquid inlet end of the second ammonia II clarification tank (31) through an overflow pipe (30), and the liquid outlet end of the second ammonia II clarification tank (31) is connected to the ammonia II carbon filtration process pipeline (32).

2. The ammonia-containing tail gas treatment system for ultrapure ammonia production according to claim 1, characterized in that: The delivery pipeline from the ammonia induced draft fan (23) to the jet ammonia absorber (26) is also connected to the ammonia source pipeline (24) of the crystallization process external cooling system.

3. A method for treating ammonia-containing tail gas in an ultrapure ammonia production system, characterized in that: Using the processing system according to any one of claims 1 to 2, the processing method comprises: Step 1: The ammonia source producing high-pressure ammonia-containing tail gas in the ultra-pure ammonia production system is transported to the high-pressure buffer tank (1) through a corresponding transport pipeline, and the ammonia source producing low-pressure ammonia-containing tail gas in the ultra-pure ammonia production system is transported to the low-pressure buffer tank (15) through a corresponding transport pipeline to separate the ammonia; Step 2: The evaporated gas ammonia in the high-pressure buffer tank (1) is transported to the ammonia condenser (8). The condensed liquid ammonia generated after cooling by the refrigerant is returned to the high-pressure buffer tank (1) through the condensed liquid ammonia return pipe (11). The ammonia condenser gas ammonia generated after the ammonia condenser (8) is depressurized is transported to the low-pressure buffer tank (15) through the ammonia condenser gas ammonia to low-pressure buffer tank pipe (14) for ammonia separation; Step 3: the liquid ammonia (12) separated and produced by the high-pressure buffer tank (1) and the low-pressure buffer tank (15) is pumped to the external cooler of the crystallization process of the alkali plant as a refrigerant for the crystallization system; Step 4: The atmospheric low-pressure buffer tank gas ammonia (22) produced by the low-pressure buffer tank (15) is pressurized by the ammonia induced draft fan (23) and then enters the jet ammonia absorber (26) to react with the mother II liquid to form ammonia II liquid. The ammonia II liquid flows through the ammonia II distribution tank (28), the first ammonia II clarification tank (29), the overflow pipe (30) and the second ammonia II clarification tank (31) in sequence and is transported to the carbon filtration system through the ammonia II carbon filtration process pipeline (32).

4. The method for treating ammonia-containing tail gas of an ultrapure ammonia production system according to claim 3, characterized in that: In step 4, the gaseous ammonia produced by the external cooling system of the crystallization process enters the jet ammonia absorber (26) together with the gaseous ammonia (22) of the low-pressure buffer tank through the gaseous ammonia source pipeline (24) of the external cooling system of the crystallization process to perform an ammonia absorption reaction.

5. The method for treating ammonia-containing tail gas in an ultrapure ammonia production system according to claim 3, characterized in that: In step 1, the ammonia source of the high-pressure ammonia-containing tail gas includes one or more of a high boiling tower receiving tank ammonia source (2), a low boiling tower receiving tank ammonia source (3), a high boiling tower ammonia source (4), a low boiling tower ammonia source (5), and a low boiling tower condenser ammonia source (6).

6. The method for treating ammonia-containing tail gas of an ultrapure ammonia production system according to claim 3, characterized in that: In step 1, the low-pressure ammonia-containing tail gas ammonia source includes one or more of a safety valve ammonia source (16), an ammonia buffer tank discharge ammonia source (17), a cylinder tail gas ammonia source (18), an ammonia recovery tank ammonia source (19), a workshop online analysis tail gas ammonia source (20), and a tank area online analysis tail gas ammonia source (21).

7. The method for treating ammonia-containing tail gas in an ultrapure ammonia production system according to claim 3, characterized in that: In step 4, the pressure of the low-pressure buffer tank gas ammonia (22) is raised by the ammonia induced draft fan (23) to a pressure of 0.3-0.5 MPa.

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