Combined alkali production tail gas treatment device
By designing a combined alkali production tail gas treatment unit, the tail gas is reverse-absorbed and compressed to generate cleaning gas, which solves the problems of scaling and blockage in the carbonization tower and insufficient cleaning gas. This achieves effective cleaning and equipment protection in the cleaning tower, and reduces production costs and tail gas emissions.
Patent Information
- Application Number
- CN202423020759.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-09
- Publication Date
- 2025-12-12
- Estimated Expiration
- 2034-12-09
AI Technical Summary
In the combined alkali production process, scaling in the carbonization tower leads to channel blockage. Existing cleaning methods increase production costs or corrode equipment. Furthermore, the natural gas-to-ammonia synthesis process lacks cleaning gas, resulting in a high risk of equipment corrosion.
Design a combined alkali production tail gas treatment device, including a cleaning tower, an alkali production tower, an absorption tower, and a compression device. The tail gas is reverse absorbed and compressed to generate cleaning gas for cleaning the carbonization tower. Ammonia gas in the tail gas is absorbed stepwise by ammonia mother liquor and washing water, reducing mother liquor loss and lowering production costs.
It effectively removes scale buildup inside the cleaning tower, reduces production costs, minimizes exhaust emissions and equipment corrosion risks, and improves raw material utilization and purification efficiency.
Smart Images
Figure CN223654730U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of alkali production technology, specifically to a combined alkali production tail gas treatment device. Background Technology
[0002] Soda ash (sodium carbonate, Na2CO3) is an important organic chemical raw material, mainly used in the production of glass products and ceramic glazes, and also widely used in papermaking, textiles, daily chemicals, and food processing industries. With the continuous development of domestic and international markets, the demand for soda ash products is increasing, and the market prospects are broad.
[0003] The combined soda ash production process, also known as the Hou's process, is a method for simultaneously producing soda ash and ammonium chloride. The main raw materials are salt, ammonia, and carbon dioxide. The specific process is as follows: First, ammonia and mother liquor are ammonified to prepare ammonia mother liquor. Then, carbon dioxide is introduced, and a carbonation reaction is carried out to produce sodium bicarbonate and ammonium chloride. Ammonium chloride can be used as a nitrogen fertilizer commonly used in agricultural production. Sodium bicarbonate is filtered and washed to obtain pure sodium bicarbonate crystals. Finally, soda ash is produced through calcination. This process combines the ammonia synthesis industry with the soda ash production industry, utilizing carbon dioxide, a byproduct of the ammonia synthesis plant, as one of the raw materials, thereby improving raw material utilization, reducing environmental pollution, and lowering production costs.
[0004] In the combined alkali production process, the carbonation reaction of ammonia mother liquor with carbon dioxide to produce sodium bicarbonate and ammonium chloride mainly takes place in the carbonation tower. Because sodium bicarbonate accumulates and forms scale inside the carbonation tower, prolonged neglect will lead to blockage of the tower channels, thus reducing the carbonation efficiency. Therefore, periodic cleaning of the carbonation tower is necessary. Conventional cleaning methods primarily utilize ammonia mother liquor and cleaning gas to remove scale buildup within the tower. The cleaning gas consumed during this process generally comes from the ammonia synthesis unit. In coal-to-ammonia synthesis processes, cleaning gas is a byproduct. However, in regions with scarce coal resources and abundant natural gas, natural gas is often used for ammonia synthesis. This process differs from coal-to-ammonia synthesis and does not produce cleaning gas as a byproduct. The cleaning gas needs to be produced by a separate nitrogen generator or directly using air as the cleaning gas. Using a separate nitrogen generator to produce nitrogen as the cleaning gas would increase production costs. If air is used as the cleaning gas, its high oxygen content would exacerbate corrosion of the carbonation tower's inner walls and internal components, affecting the normal operation of the equipment. Utility Model Content
[0005] To address the shortcomings of existing technologies, this utility model discloses a combined alkali production tail gas treatment device, including a scrubbing tower, an alkali production tower, an absorption tower, and a compression device, wherein the absorption tower includes an upper section and a lower section.
[0006] The side inlet of the cleaning tower is connected to the ammonia mother liquor supply pipeline. The bottom of the cleaning tower is provided with an inlet for inputting cleaning gas. The bottom outlet of the cleaning tower is connected to the inlet of the alkali production tower. The bottom inlet of the alkali production tower is connected to the raw material gas pipeline, and the bottom of the alkali production tower is provided with an outlet. The top exhaust outlets of the cleaning tower and the top exhaust outlets of the alkali production tower are connected to the inlet of the lower section of the absorption tower through a tail gas pipeline.
[0007] The inlet of the lower section of the absorption tower is connected to the mother liquor supply pipeline, the outlet of the lower section of the absorption tower is connected to the mother liquor outlet pipeline, the outlet of the lower section of the absorption tower is connected to the inlet of the upper section of the absorption tower, the inlet of the upper section of the absorption tower is connected to the wash water supply pipeline, the outlet of the upper section of the absorption tower is connected to the wash water outlet pipeline, and the outlet of the upper section of the absorption tower is connected to the bottom inlet of the cleaning tower via a compression device.
[0008] In this utility model, the combined alkali production tail gas treatment device separates the tail gas generated from the cleaning tower and the tail gas generated from the alkali production tower into the absorption tower. After being absorbed by the absorption tower, the tail gas is compressed and pressurized by the compression equipment and used as the cleaning gas for the cleaning tower. It also cleans the scale in the cleaning tower together with the ammonia mother liquor.
[0009] This invention achieves the purpose of fully absorbing ammonia and carbon dioxide in the tail gas by having the tail gas and absorbent come into countercurrent contact. In the lower section of the absorption tower, the liquid inlet of the lower section of the absorption tower is located at the upper part of the lower section of the absorption tower. The absorbent mother liquor is input from the liquid inlet of the lower section of the absorption tower, and the first-stage tail gas is input from the gas inlet of the lower section of the absorption tower. After countercurrent absorption in the lower section of the absorption tower, the absorbed mother liquor is discharged from the liquid outlet located at the lower part of the lower section of the absorption tower. The gas discharged from the exhaust port located at the upper part of the lower section of the absorption tower is the second-stage tail gas after absorbing ammonia.
[0010] In the upper section of the absorption tower, the liquid inlet is located at the top of the upper section of the absorption tower. The absorbent wash water is input from the liquid inlet of the upper section of the absorption tower, and the secondary tail gas is input from the gas inlet of the upper section of the absorption tower. After reverse absorption in the upper section of the absorption tower, the mother liquor entrained in the tail gas is washed. The absorbed wash water is discharged from the liquid outlet located at the bottom of the upper section of the absorption tower. The tail gas that has absorbed ammonia and carbon dioxide is connected to the bottom gas inlet of the cleaning tower through the cleaning gas pipeline of the internal compression equipment from the gas outlet of the upper section of the absorption tower.
[0011] Optionally, the compression equipment includes either a screw compressor or a centrifugal compressor.
[0012] Furthermore, a vent branch is provided on the pipeline connecting the absorption tower and the compression equipment; an inert gas replenishment branch is provided on the pipeline connecting the compression equipment and the cleaning tower. The circulating cleaning gas from the absorption tower is used as the main component of the cleaning gas source by the compression equipment, and the excess tail gas is normally vented. In normal production processes, only a small amount of low-pressure nitrogen needs to be added, reducing the cost of low-pressure nitrogen consumption. Moreover, the NH3 in the circulating cleaning gas is absorbed and utilized during the circulation process, thereby reducing the ammonia content in the tail gas.
[0013] Furthermore, the combined alkali production tail gas treatment unit also includes a gas-liquid separation device. The gas outlet of the lower section of the absorption tower is connected to the gas-liquid separation device, the gas outlet of the gas-liquid separation device is connected to the gas inlet of the upper section of the absorption tower, and the liquid outlet of the gas-liquid separation device is connected to the lower section of the absorption tower. The tail gas after absorption in the lower part of the absorption tower will carry some mother liquor. After separation by the gas-liquid separation device, the mother liquor returns to the lower section of the absorption tower. This reduces the loss of mother liquor in the lower section of the absorption tower and prevents excessive mother liquor from entering the upper section of the absorption tower and affecting it.
[0014] Gas-liquid separation equipment includes any one of gravity separators, filter separators, and high-efficiency blade separators.
[0015] Furthermore, the combined alkali production tail gas treatment unit also includes a heat exchanger, with the liquid outlet of the upper section of the absorption tower connected to the inlet of the heat exchanger, and the outlet of the heat exchanger connected to the liquid inlet of the upper section of the absorption tower.
[0016] Optionally, the heat exchanger may include any one of shell-and-tube heat exchangers, plate heat exchangers, or two-tube heat exchangers.
[0017] Optionally, the absorption tower further includes a middle section, wherein the gas outlet of the lower section of the absorption tower is connected to the gas inlet of the middle section of the absorption tower, the liquid inlet of the middle section of the absorption tower is connected to the acid supply pipeline, the liquid outlet of the middle section of the absorption tower is connected to the acid outlet pipeline, and the gas outlet of the middle section of the absorption tower is connected to the gas inlet of the upper section of the absorption tower.
[0018] The process of the combined alkali production tail gas treatment device of this utility model includes an alkali production process and a tail gas treatment process. The alkali production process includes an alkali production tower and a washing tower. The tail gas treatment process includes an absorption operation and a compression operation. The absorption operation is a multi-stage absorption, which includes mother liquor absorption and wash water absorption. The primary tail gas obtained from the alkali production tower and the washing tower is subjected to mother liquor absorption to obtain secondary tail gas. The secondary tail gas is subjected to wash water absorption to obtain tertiary tail gas. The tertiary tail gas is compressed and returned to the washing tower as washing gas.
[0019] The absorption operation includes mother liquor absorption and wash water absorption, which allows for segmented treatment of the primary tail gas generated in the alkali production process. The absorbent for mother liquor absorption is mother liquor (mainly composed of NH3 2-8%, NH4Cl 15-30%, NaCl 5-15%, CO2 2-8%, with the remainder being water), which can absorb ammonia from the primary tail gas. Using mother liquor also improves raw material utilization and reduces production costs. The absorbent for wash water absorption is wash water, used to further wash and absorb ammonia and any entrained mother liquor from the secondary tail gas, ensuring that the ammonia content in the tertiary tail gas is below 1000 ppm, meeting tail gas emission requirements and improving purification efficiency. This invention utilizes different absorption media to absorb ammonia from the tail gas in stages, making the absorption process more thorough and improving overall treatment efficiency.
[0020] The exhaust gas after washing and absorption by this invention is a three-stage exhaust gas, whose main component is nitrogen, containing a small amount of oxygen and water vapor, and basically free of ammonia and carbon dioxide.
[0021] The process of the combined alkali production tail gas treatment device of this utility model treats the tail gas generated in the alkali production process through absorption and compression operations, both of which are indispensable. If the tail gas generated in the alkali production process is mixed and sent to the absorption unit, ideally, the ammonia will be absorbed after absorption, and the remaining gas will mainly consist of nitrogen and a small amount of oxygen, which can be directly discharged into the atmosphere. However, in actual production, ammonia still exists in the tail gas after absorption treatment. If it is directly discharged into the atmosphere, it will cause air pollution. If the tail gas generated in the alkali production process is directly compressed and recycled without absorption, the tail gas from the alkali production process will carry mother liquor, which contains chloride ions and other substances that will corrode compressors and other related equipment. If the absorption process is replaced with a gas-liquid separation process, since gas-liquid separation can only perform simple gas-liquid separation, the separation capacity in the soda ash industry is limited, and a small amount of mother liquor will still enter the compression process with the tail gas, causing corrosion of the compression equipment. Therefore, the tail gas generated in the alkali production process of this utility model is absorbed and washed before being compressed, which can reduce the corrosion of the compression equipment by the tail gas. At the same time, the three-stage tail gas is compressed and returned to the cleaning tower in the alkali production process to be used as cleaning gas in the cleaning section, reducing production costs and reducing tail gas emissions.
[0022] The process of the combined alkali production tail gas treatment device of this utility model includes a cleaning tower in which ammonia mother liquor enters from the top and cleaning gas enters from the bottom. The ammonia mother liquor and cleaning gas flow counterclockwise within the tower to perform cleaning. This achieves the function of cleaning the inner wall of the carbonization tower and its internal components. The principle is based on the interaction between NH3·H2O in the ammonia mother liquor and HCO3 in the crystalline components. － The reaction produces NH4 + and CO3 2-This process converts low-soluble hydrocarbons into highly soluble carbonates, thereby removing scale buildup. The exhaust gas from the cleaning tower is then discharged from the top of the tower.
[0023] In the process of the combined alkali production tail gas treatment device of this utility model, the alkali production tower includes an ammonia mother liquor entering the tower from the top and carbon dioxide entering the tower from the bottom. The mother liquor and carbon dioxide flow counterclockwise within the tower. The sodium bicarbonate produced by the reaction is removed from the bottom of the tower, and the tail gas generated by the alkali production tower is discharged from the top of the tower. The tail gas generated by the cleaning tower and the alkali production tower are mixed to form the primary tail gas of this utility model. The main component of the primary tail gas is nitrogen, containing small amounts of ammonia, carbon dioxide, oxygen, and water vapor.
[0024] Furthermore, the volume fraction of inert gas in the cleaning gas is not less than 80%. Nitrogen is typically used as an inert gas in the cleaning tower, as it can effectively prevent oxidation reactions caused by other reactive gases (such as oxygen), thereby protecting the cleaned equipment or materials from damage. Inert gases include nitrogen, argon, and other inert gases, with nitrogen playing a dominant role in the cleaning process and effectively exerting its protective function. Optionally, nitrogen can be supplemented according to the nitrogen content in the third-stage tail gas to ensure that the volume fraction of inert gas is above 90%.
[0025] Furthermore, a portion of the tertiary tail gas is vented. The amount of tail gas entering the compressor can be adjusted according to the operating conditions of the alkali production tower and the cleaning tower; excess tail gas can be vented. Optionally, if the amount of tertiary tail gas from the absorption operation exceeds the cleaning gas volume required by the cleaning tower, the venting rate can be adjusted based on the cleaning effect of the cleaning tower. Each ton of alkali requires 100–170 Nm³ of cleaning gas. 3 If the air volume exceeds this range, the venting volume can be adjusted for venting.
[0026] Furthermore, the secondary exhaust gas undergoes gas-liquid separation before being absorbed by washing water. The secondary exhaust gas contains mother liquor; therefore, through gas-liquid separation, the separated gas is further absorbed by washing water, while the separated liquid is returned to mother liquor absorption for reuse. This process reduces mother liquor loss during absorption and prevents excessive mother liquor from entering the washing water absorption process, thus minimizing its impact.
[0027] Furthermore, the wash water output from the wash water absorption process is cooled and then recycled. The temperature of the absorbed wash water is lowered using a heat exchanger or other cooling equipment, allowing it to be reused.
[0028] Furthermore, the temperature for absorption of the mother liquor is 25–45°C, and the pressure is 0–0.1 MPaG;
[0029] And / or, the temperature of the wash water is 25-45°C and the pressure is 0-0.1 MPaG.
[0030] Preferably, the temperature of the mother liquor absorption is 30–40°C, and the pressure is 0.02–0.05 MPaG; and / or, the temperature of the wash water absorption is 25–35°C, and the pressure is 0.01–0.03 MPaG. The temperature of the mother liquor absorption is controlled at 30–40°C. Within this temperature range, the mother liquor can effectively react with the ammonia in the primary tail gas, thereby achieving a high absorption efficiency. The pressure of the mother liquor absorption is set to 0.02–0.05 MPaG. Appropriate pressure helps to increase the contact area and contact time between the primary tail gas and the mother liquor, thereby improving the absorption efficiency. The temperature and pressure of the wash water absorption are lower than those of the mother liquor absorption, with the temperature controlled at 25–35°C and the pressure at 0.01–0.03 MPaG.
[0031] Optionally, the multi-stage absorption also includes acid absorption, wherein the acid absorption temperature is 25–45°C and the pressure is 0–0.1 MPaG. The primary tail gas is sequentially absorbed by mother liquor, acid, and wash water to obtain tertiary tail gas. The acid used in the acid absorption can be inorganic acids such as hydrochloric acid and sulfuric acid. Further acid absorption after mother liquor absorption can further absorb ammonia in the tail gas. Depending on the specific operating conditions, if it is necessary to control the ammonia content in the tertiary tail gas to below 100 ppm, a multi-stage absorption method of sequential mother liquor absorption, acid absorption, and wash water absorption can be used. If it is necessary to control the ammonia content in the tertiary tail gas to below 1000 ppm, a multi-stage absorption method of sequential mother liquor absorption and wash water absorption can be used.
[0032] Compared with the prior art, the beneficial effects of this utility model are as follows:
[0033] (1) In the case of no by-product cleaning gas in the natural gas to ammonia synthesis process, the combined alkali tail gas treatment device of this utility model does not require an additional nitrogen production device for producing nitrogen as the cleaning gas for the cleaning tower, which reduces production costs and also reduces tail gas emissions.
[0034] (2) The combined alkali production tail gas treatment device of this utility model reuses the tail gas generated by the cleaning tower and the alkali production tower through the absorption tower and the compression equipment, thereby increasing the raw material utilization rate and reducing the amount of waste gas emissions. Attached Figure Description
[0035] The accompanying drawings, which form part of this application, are used to provide a further understanding of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an undue limitation of the present invention. In the drawings:
[0036] Figure 1 This diagram shows a combined alkali production tail gas treatment device according to the present invention.
[0037] The above figures include the following reference numerals:
[0038] 1. Cleaning tower; 2. Alkali production tower; 3. Absorption tower; 31. Lower section of absorption tower; 32. Upper section of absorption tower; 4. Compression equipment; 5. Gas-liquid separation equipment; 6. Heat exchanger; 7. Ammonia mother liquor supply pipeline; 8. Raw material gas pipeline; 9. Tail gas pipeline; 10. Mother liquor supply pipeline; 11. Mother liquor outlet pipeline; 12. Wash water supply pipeline; 13. Wash water outlet pipeline; 14. Vent branch; 15. Inert gas replenishment branch. Detailed Implementation
[0039] To facilitate understanding of this utility model, a more comprehensive description of it is provided below, along with preferred embodiments. However, it should be understood that these embodiments are for more detailed explanation only and should not be construed as limiting the utility model in any way, i.e., they do not limit the scope of protection of this utility model. Unless otherwise defined, the technical terms used in the following embodiments have the same meaning as commonly understood by those skilled in the art to which this utility model pertains.
[0040] Example 1
[0041] A combined alkali production tail gas treatment device, such as Figure 1 As shown, it includes a washing tower 1, an alkali production tower 2, an absorption tower 3, and a compression device 4. The absorption tower includes an upper section 32 and a lower section 31.
[0042] The side inlet of the cleaning tower 1 is connected to the ammonia mother liquor supply pipeline 7. The bottom of the cleaning tower 1 is provided with an inlet for inputting cleaning gas. The bottom outlet of the cleaning tower 1 is connected to the inlet of the alkali production tower 2. The bottom inlet of the alkali production tower 2 is connected to the raw material gas pipeline 8, and the bottom of the alkali production tower 2 is provided with an outlet. The top exhaust ports of the cleaning tower 1 and the top exhaust ports of the alkali production tower 2 are connected to the inlet of the lower section 31 of the absorption tower through the tail gas pipeline 9.
[0043] The inlet of the lower section 31 of the absorption tower is connected to the mother liquor supply pipeline 10, the outlet of the lower section 31 of the absorption tower is connected to the mother liquor outlet pipeline 11, the outlet of the lower section 31 of the absorption tower is connected to the inlet of the upper section 32 of the absorption tower, the inlet of the upper section 32 of the absorption tower is connected to the wash water supply pipeline 12, the outlet of the upper section 32 of the absorption tower is connected to the wash water outlet pipeline 13, and the outlet of the upper section 32 of the absorption tower is connected to the bottom inlet of the cleaning tower 1 via the compression device 4.
[0044] The compression device 4 can be any known device with gas compression function, such as a screw compressor or a centrifugal compressor.
[0045] Example 2
[0046] Based on the combined alkali production tail gas treatment device shown in Example 1, this is a preferred embodiment. A vent branch 14 is installed on the pipeline connecting the absorption tower 3 and the compression device 4; an inert gas replenishment branch 15 is installed on the pipeline connecting the compression device 4 and the cleaning tower. When the amount of tail gas collected from the absorption tower 3 is greater than the amount of cleaning gas required by the cleaning tower 1, the excess tail gas can be normally vented through the vent branch 14; inert gas can be replenished through the inert gas replenishment branch 15 according to the nitrogen content in the three-stage tail gas to ensure that the volume fraction of inert gas in the cleaning gas is not less than 80%.
[0047] Example 3
[0048] Based on the combined alkali production tail gas treatment device shown in Embodiment 1, this embodiment is a preferred embodiment. The combined alkali production tail gas treatment device of this utility model further includes a gas-liquid separation device 5. The outlet of the lower section 31 of the absorption tower is connected to the gas-liquid separation device 5, the outlet of the gas-liquid separation device 5 is connected to the inlet of the upper section 32 of the absorption tower, and the outlet of the gas-liquid separation device 5 is connected to the lower section 32 of the absorption tower. The tail gas absorbed by the lower section 31 of the absorption tower will carry some mother liquor. After separation by the gas-liquid separation device 5, the mother liquor returns to the lower section 31 of the absorption tower. The gas-liquid separation device can be any known device with gas-liquid separation function. Optionally, the gas-liquid separation device includes a gravity separator, a filter separator, or a high-efficiency blade separator.
[0049] Optionally, the combined alkali production tail gas treatment device of this utility model further includes a heat exchanger 6, with the liquid outlet of the upper section 32 of the absorption tower connected to the inlet of the heat exchanger 6, and the outlet of the heat exchanger 6 connected to the upper section 32 of the absorption tower. The heat exchanger can be any known device with heat exchange function; optionally, the heat exchanger includes a shell-and-tube heat exchanger, a plate heat exchanger, or a double-tube heat exchanger.
[0050] Example 4
[0051] Based on the combined alkali production tail gas treatment device shown in Example 1, this example is a preferred embodiment. In the combined alkali production tail gas treatment device of this utility model, the absorption tower also includes a middle section of the absorption tower. The gas outlet of the lower section of the absorption tower is connected to the gas inlet of the middle section of the absorption tower. The liquid inlet of the middle section of the absorption tower is connected to the acid supply pipeline. The liquid outlet of the middle section of the absorption tower is connected to the acid outlet pipeline. The gas outlet of the middle section of the absorption tower is connected to the gas inlet of the upper section of the absorption tower.
[0052] Example 5
[0053] This embodiment demonstrates a combined alkali production tail gas treatment process under specific operating conditions. It should be noted that this process is merely a demonstration of a preferred method and does not limit the scope of protection of this utility model.
[0054] A combined alkali production tail gas treatment process specifically includes: Ammonia mother liquor, prepared by ammoniation reaction of ammonia and mother liquor during the combined alkali production process, enters the cleaning tower through the side inlet of the cleaning tower via an ammonia mother liquor supply pipeline. Cleaning gas, transported via a cleaning gas pipeline, enters the cleaning tower from the bottom. The ammonia mother liquor and cleaning gas flow counter-currently within the cleaning tower. The tail gas generated by the cleaning tower is discharged from the top of the tower. The ammonia mother liquor cleaned by the cleaning tower is discharged from the bottom of the cleaning tower and transported to the inlet of the alkali production tower. Carbon dioxide enters the tower from the bottom inlet of the alkali production tower. The mother liquor and carbon dioxide flow counter-currently within the alkali production tower. The sodium bicarbonate produced by the reaction is removed from the bottom of the tower. The tail gas generated by the alkali production tower is discharged from the top of the tower. The primary tail gas generated by the alkali production tower and the cleaning tower is mixed (primary tail gas composition and content: nitrogen 74%, ammonia 11%, carbon dioxide 5%, oxygen 4%, water vapor 6%) and transported to the lower section of the absorption tower.
[0055] The temperature of the lower section of the absorber is 30–40℃, and the pressure is 0.02–0.05 MPaG. After the primary tail gas and mother liquor are reverse-absorbed, the absorbed mother liquor is output from the lower part of the lower section of the absorber. The secondary tail gas (the composition and content of the secondary tail gas are: nitrogen 85%, ammonia 1%, carbon dioxide 6%, oxygen 4%, and water vapor 4%) absorbed by the lower section of the absorber is transported to the upper section of the absorber via a gas-liquid separator. The absorbent in the upper section of the absorber is wash water, and the temperature of the upper section of the absorber is 25–35℃, and the pressure is 0.01–0.03 MPaG. After the secondary tail gas and wash water are reverse-absorbed, the wash water is output from the lower part of the upper section of the absorption tower. The tertiary tail gas (composed of 90% nitrogen, 5% oxygen, and 5% water vapor) after absorption in the lower section of the absorption tower is output from the upper part of the upper section of the absorption tower, pressurized by a centrifugal compressor, and returned to the lower part of the cleaning tower as cleaning gas for recycling. If the amount of tail gas from the absorption tower is greater than the amount of cleaning gas required by the cleaning tower, the excess tail gas is vented normally. The vented tail gas meets the tail gas emission index requirements, and a small amount of nitrogen is added periodically. A nitrogen analyzer is installed on the tail gas pipeline entering the cleaning tower, and nitrogen is added according to the nitrogen content in the tail gas to ensure that the nitrogen integral is above 90%.
[0056] Example 6
[0057] Based on the combined alkali production tail gas treatment process shown in Example 5, this example is a preferred embodiment. The multi-stage absorption also includes acid absorption, with the acid absorption temperature being 25–45°C and the pressure being 0–0.1 MPaG. The first-stage tail gas is sequentially absorbed by mother liquor, acid, and wash water to obtain the third-stage tail gas. The acid that can be selected in the acid absorption is inorganic acid such as hydrochloric acid and sulfuric acid. After the mother liquor absorption, further acid absorption can be used to further absorb the ammonia in the tail gas. Depending on the specific operating conditions, if it is necessary to control the ammonia content in the third-stage tail gas to below 100 ppm, a multi-stage absorption method of sequential mother liquor absorption, acid absorption, and wash water absorption can be used. If it is necessary to control the ammonia content in the third-stage tail gas to below 1000 ppm, a multi-stage absorption method of sequential mother liquor absorption and wash water absorption can be used.
[0058] It should be noted that the above description is a further detailed explanation of the present invention in conjunction with specific embodiments, and it should not be considered that the specific implementation of the present invention is limited to these descriptions; for those skilled in the art to which the present invention pertains, several simple improvements and modifications can be made without departing from the concept of the present invention, and all such improvements and modifications should be considered to fall within the scope of protection of the present invention.
Claims
1. A combined alkali production tail gas treatment device, characterized in that, It includes a washing tower, an alkali production tower, an absorption tower, and a compression device, wherein the absorption tower includes an upper section and a lower section. The side inlet of the cleaning tower is connected to the ammonia mother liquor supply pipeline. The bottom of the cleaning tower is provided with an inlet for inputting cleaning gas. The bottom outlet of the cleaning tower is connected to the inlet of the alkali production tower. The bottom inlet of the alkali production tower is connected to the raw material gas pipeline, and the bottom of the alkali production tower is provided with an outlet. The top exhaust outlets of the cleaning tower and the top exhaust outlets of the alkali production tower are connected to the inlet of the lower section of the absorption tower through a tail gas pipeline. The inlet of the lower section of the absorption tower is connected to the mother liquor supply pipeline, the outlet of the lower section of the absorption tower is connected to the mother liquor outlet pipeline, the outlet of the lower section of the absorption tower is connected to the inlet of the upper section of the absorption tower, the inlet of the upper section of the absorption tower is connected to the wash water supply pipeline, the outlet of the upper section of the absorption tower is connected to the wash water outlet pipeline, and the outlet of the upper section of the absorption tower is connected to the bottom inlet of the cleaning tower via a compression device.
2. The combined alkali production tail gas treatment device according to claim 1, characterized in that, A vent branch is provided on the pipeline connecting the absorption tower and the compression equipment.
3. The combined alkali production tail gas treatment device according to claim 1, characterized in that, An inert gas replenishment branch is provided on the pipeline connecting the compression device and the cleaning tower.
4. The combined alkali production tail gas treatment device according to claim 1, characterized in that, The device also includes a gas-liquid separation device, the gas outlet of the lower section of the absorption tower is connected to the gas-liquid separation device, the gas outlet of the gas-liquid separation device is connected to the gas inlet of the upper section of the absorption tower, and the liquid outlet of the gas-liquid separation device is connected to the lower section of the absorption tower.
5. The combined alkali production tail gas treatment device according to claim 1, characterized in that, The device also includes a heat exchanger, with the liquid outlet of the upper section of the absorption tower connected to the inlet of the heat exchanger, and the outlet of the heat exchanger connected to the liquid inlet of the upper section of the absorption tower.
6. The combined alkali production tail gas treatment device according to claim 1, characterized in that, The compression equipment includes any one of a screw compressor and a centrifugal compressor.
7. The combined alkali production tail gas treatment device according to claim 4, characterized in that, The gas-liquid separation equipment includes any one of gravity separators, filter separators, and high-efficiency blade separators.
8. The combined alkali production tail gas treatment device according to claim 5, characterized in that, The heat exchanger includes any one of shell-and-tube heat exchangers, plate heat exchangers, and double-tube heat exchangers.
9. The combined alkali production tail gas treatment device according to claim 1, characterized in that, The absorption tower also includes a middle section, the gas outlet of the lower section of the absorption tower is connected to the gas inlet of the middle section of the absorption tower, the liquid inlet of the middle section of the absorption tower is connected to the acid supply pipeline, the liquid outlet of the middle section of the absorption tower is connected to the acid outlet pipeline, and the gas outlet of the middle section of the absorption tower is connected to the gas inlet of the upper section of the absorption tower.