Ammonia water preparation tail gas recovery and combined generation system

Abstract

The invention discloses an ammonia water preparation tail gas recovery and combined generation system, belongs to the technical field of ammonia synthesis in the coal chemical industry, and aims to solve the technical problems of how to ensure all effective gases in the ammonia water preparation process to be recycled, realize the environment-friendly target of zero discharge of a torch and meet the environment-friendly generation requirement of zero discharge of the ammonia torch. According to the technical scheme, the device structurally comprises an ammonia absorber, an ammonia water intermediate tank, a tail gas absorption tank and a gas holder, a gas ammonia input pipeline is arranged at a gas ammonia inlet in the lower position of the middle of one side of the ammonia absorber, and a gas ammonia flow regulating valve is arranged on the gas ammonia input pipeline; a desalted water input pipeline is arranged at the upper position of the middle part of the other side of the ammonia absorber, a soft water flow regulating valve is arranged on the desalted water input pipeline, and an ammonia water circulating pipeline is arranged at the lower position of the middle part of the other side of the ammonia absorber; a bottom outlet of the ammonia absorber is communicated with the ammonia water intermediate tank through an ammonia water output pipeline.

Description

Technical Field

[0001] This invention relates to the field of coal chemical ammonia synthesis technology, specifically to a combined system for recovering tail gas from ammonia water preparation. Background Technology

[0002] Ammonia water plays an important role in modern agricultural nitrogen fertilizer, the production of various chemicals in the industrial sector, and daily life. It is also widely used in environmentally friendly coal chemical production, such as in flue gas desulfurization and denitrification of power boilers and wastewater neutralization treatment. In the current technology for preparing 5%-28% concentration ammonia water, the ammonia water stored in the intermediate tank undergoes flash evaporation, releasing some dissolved hydrogen, nitrogen, and ammonia gas, influenced by temperature and pressure. Furthermore, the existing ammonia water production process involves combustion of the purge gas / tail gas in the intermediate tank's piping area via the flare network. The high ammonia content in the tail gas results in high levels of nitrogen oxides in the combustion gas, impacting environmentally friendly production. Simultaneously, the combustion of effective gases such as hydrogen and ammonia leads to waste and increases product energy consumption.

[0003] In the existing ammonia preparation process, the ammonia concentration fluctuates greatly due to the inaccuracy and control of the feed flow regulating valve, requiring manual intervention and adjustment. This results in numerous ammonia quality issues affecting the use of downstream processes. Additionally, the large temperature fluctuations of the ammonia cause fluctuations in ammonia concentration, flash vapor, and release gas volume, increasing circulating water consumption and impacting the stable operation of the unit.

[0004] Therefore, how to ensure that all effective gases are recovered and reused during the ammonia preparation process, achieve the environmental protection goal of zero emissions from the flare, meet the environmental protection requirements for zero emissions from the ammonia flare, and at the same time reduce the waste of effective gases and reduce fuel coal consumption are the technical problems that urgently need to be solved. Summary of the Invention

[0005] The technical objective of this invention is to provide a combined system for recovering and generating tail gas from ammonia preparation, in order to address the issues of ensuring the complete recovery and utilization of effective gases during ammonia preparation, achieving the environmental goal of zero emissions from the flare, meeting the environmental generation requirements for zero emissions from the ammonia flare, while simultaneously reducing the waste of effective gases and lowering fuel coal consumption.

[0006] The technical objective of this invention is achieved as follows: a combined system for recovering ammonia water preparation tail gas, comprising an ammonia absorber, an ammonia water intermediate tank, a tail gas absorption tank, and a gas holder. An ammonia inlet pipe is located at the lower center of one side of the ammonia absorber, and an ammonia flow regulating valve is installed on the ammonia inlet pipe. A demineralized water inlet pipe is located at the upper center of the other side of the ammonia absorber, and a soft water flow regulating valve is installed on the demineralized water inlet pipe. An ammonia water circulation pipe is located at the lower center of the other side of the ammonia absorber. The bottom outlet of the ammonia absorber is connected to the ammonia water intermediate tank via an ammonia water outlet pipe. An ammonia water cooler is installed on the ammonia water outlet pipe, and the ammonia water outlet pipe is connected to the shell-side inlet of the ammonia water cooler. A circulating cooling water outlet regulating valve is installed on the tube-side pipe of the ammonia water cooler, and an ammonia water thermometer is installed on the ammonia water outlet pipe. The connection between the ammonia intermediate tank and the ammonia output pipeline is located at the upper-middle position on one side of the ammonia intermediate tank. The ammonia output pipeline is located at the lower-middle position on the other side of the ammonia intermediate tank. One end of the output pipeline is connected to the ammonia intermediate tank, and the other end splits into two paths: one is an ammonia circulation pipeline connected to the ammonia absorber and equipped with an ammonia circulation regulating valve; the other is an ammonia external delivery pipeline equipped with an ammonia external delivery valve. A tail gas pipeline is installed at the tail gas outlet at the top of the ammonia water intermediate tank. One end of the tail gas pipeline is connected to the ammonia water intermediate tank, and the other end is inserted into the bottom of the tail gas absorption tank. A demineralized water inlet pipeline is installed at the upper middle part of one side of the tail gas absorption tank, and a demineralized water regulating valve is installed on the demineralized water inlet pipeline. The top of the tail gas absorption tank is connected to the gas holder through an air venting pipeline. An air venting pipeline is installed at the lower middle part of one side of the gas holder, and an air venting regulating valve is installed on the air venting pipeline.

[0007] Preferably, an ammonia flow meter is installed on the ammonia input pipeline; A demineralized water flow meter is installed on the demineralized water input pipeline.

[0008] More preferably, an ammonia water intermediate tank level gauge is installed at a lower position in the middle of one side of the ammonia water intermediate tank, and an ammonia water concentration gauge is installed at a lower position in the middle of the other side of the ammonia water intermediate tank. The ammonia water concentration gauge is located above the ammonia water intermediate tank output pipe, and an ammonia water circulation pump is installed on the ammonia water intermediate tank output pipe; an ammonia water intermediate tank pressure gauge is installed on one side of the top of the ammonia water intermediate tank.

[0009] More preferably, a dilute ammonia water output pipe is provided at a lower position in the middle of one side of the tail gas absorption tank. The dilute ammonia water output pipe is arranged opposite to the demineralized water inlet pipe, and one end of the dilute ammonia water output pipe is connected to the tail gas absorption tank. The other end of the dilute ammonia water output pipe is connected to the ammonia water intermediate tank in sequence through a dilute ammonia water pump, a dilute ammonia water pressure gauge, and a dilute ammonia water external delivery regulating valve. A tail gas absorption tank level gauge is provided on the tail gas absorption tank.

[0010] More preferably, an air venting flow meter is installed on the ammonia tail gas pipeline.

[0011] More preferably, a gas holder height gauge is installed at the middle of one side of the gas holder; a gas holder pressure gauge is installed at one side of the top of the gas holder; and a venting flare pipe is installed at the other side of the top of the gas holder, with a venting valve installed on the venting flare pipe.

[0012] More preferably, in the ammonia water production process, the gaseous ammonia is supplied by the third stage of the coal chemical ammonia synthesis machine. The gaseous ammonia pressure is 0.45 MPa and the temperature is 8℃. Detected by a gaseous ammonia flow meter, the gaseous ammonia flow regulating valve sends the gaseous ammonia into the lower ammonia inlet of the ammonia absorber through the gaseous ammonia input pipeline. In the ammonia absorber, it comes into counter-current contact with dilute ammonia water from the ammonia water circulation pipeline and demineralized water metered by a demineralized water flow meter and input through the demineralized water input pipeline and soft water flow regulating valve. The ammonia absorber is equipped with structured stainless steel packing to achieve uniform contact and absorption of gaseous ammonia with dilute ammonia water and demineralized water, producing ammonia water. The ammonia water then enters the ammonia water output pipeline... The shell-side inlet of the ammonia water cooler exchanges heat with the circulating water flowing into the tube-side of the ammonia water cooler through the tube-side pipes and the circulating cooling water inlet control valve. After the dilute ammonia water is cooled, it is sent to the upper inlet of the ammonia water intermediate tank through the ammonia water output pipe. After buffering and flash evaporation, the dilute ammonia water is mixed with the dilute ammonia water produced by the ammonia gas recovered and absorbed by the tail gas absorption tank. After being pressurized by the dilute ammonia water pump, the mixed ammonia water is pressed by the ammonia water circulation pump. The ammonia water that does not meet the standard is sent to the upper inlet of the ammonia absorber through the ammonia water circulation pipe to enter the next ammonia water preparation cycle. The ammonia water that meets the standard is sent to the next section for use through the ammonia water external delivery regulating valve. The ammonia- and hydrogen-containing tail gas from the flash evaporation of the ammonia water intermediate tank is inserted into the bottom of the tail gas absorption tank through the tail gas outlet at the top of the ammonia water intermediate tank and the tail gas pipeline. The tail gas absorption tank is filled to the preset liquid level by the demineralized water supplied by the demineralized water regulating valve. The gaseous ammonia in the tail gas is gradually absorbed by the demineralized water in the tail gas absorption tank from the bottom to the top. After the ammonia is purified, the hydrogen- and nitrogen-containing vented air is sent to the gas inlet through the vented air pipeline. The gas is buffered and separated by the gas holder. The hydrogen-containing vented air is sent to the boiler for combustion through the vented air external valve.

[0013] More preferably, when the system is in steady-state operation, the target of a stable ammonia concentration of 25% is achieved by setting the ratio of gaseous ammonia to demineralized water at the ammonia absorber inlet to 1:4. The opening of the soft water flow regulating valve is controlled by the demineralized water flow meter, and the opening of the gaseous ammonia flow regulating valve is controlled by the gaseous ammonia flow meter; specifically: When the ammonia concentration meter is within the set target of 25±0.2%, the ratio of gaseous ammonia to demineralized water should be set to 1:4 as much as possible according to the load. When the ammonia concentration meter is lower than 24.8% or higher than 25.2%, the opening of the ammonia circulation regulating valve should be adjusted through cascade control to keep the ammonia concentration accuracy within the set target.

[0014] Ideally, the ammonia water temperature output by the ammonia absorber is 50-70℃, and the ammonia water thermometer reading is kept stable at 35-40℃. The flow rate of the circulating cooling water is controlled by adjusting the flow rate of the circulating cooling water outlet valve, keeping the temperature of the ammonia water entering the intermediate tank within the set range. When the winter temperature is low and the ammonia water thermometer reading is below 35℃, the opening of the circulating cooling water outlet valve is reduced to decrease the circulating cooling water flow rate, thereby reducing circulating water replenishment and consumption. When the summer temperature causes the ammonia water thermometer reading to be above 40℃, the opening of the circulating cooling water outlet valve is increased to increase the circulating cooling water flow rate, keeping the ammonia water temperature between 35-40℃. The ammonia water supply regulating valve is used to control the level gauge reading in the intermediate ammonia tank between 25% and 80%. When the level gauge reading is below 25%, the ammonia water supply regulating valve is adjusted downwards to raise the level in the intermediate ammonia tank; when the level gauge reading is above 80%, the ammonia water supply regulating valve is adjusted upwards to increase the ammonia water supply.

[0015] More preferably, the system ensures that the dilute ammonia water pressure gauge at the outlet of the dilute ammonia water pump is higher than the pressure gauge of the ammonia water intermediate tank, and controls the pressure difference to exceed 0.1 MPa, thereby ensuring that the dilute ammonia water is normally delivered into the ammonia water intermediate tank and thus ensuring the stable operation of the tail gas absorption tank. The opening of the demineralized water regulating valve is set by the air venting flow meter to control the demineralized water flow at the inlet of the tail gas absorption tank, and the index of the dilute ammonia concentration meter is controlled between 10% and 15%. Keep the level gauge reading of the exhaust gas absorption tank between 25% and 80%. When the level gauge reading is below 25%, reduce the dilute ammonia water supply regulating valve; when the level gauge reading is above 80%, increase the dilute ammonia water supply regulating valve. Adjust the amount of vented air by using the venting valve to control the pressure gauge reading between 10 and 15 kPa. Monitor the pressure gauge reading. When the pressure gauge reading is less than 10 kPa, fully close the venting valve at the top of the gas holder and reduce the venting valve. When the pressure gauge reading is higher than 15 kPa, first open the venting valve and then gradually open it fully. If the pressure gauge reading is still higher than 15 kPa, then increase the venting valve and gradually open it fully to control the gas holder pressure within the specified range. The readings of the gas holder height gauge should be between 30% and 75%. When the readings are below 30%, adjust the venting valve to reduce the amount of vented air. When the readings are above 75%, adjust the venting valve to increase the amount of vented air sent to the boiler.

[0016] The ammonia water preparation tail gas recovery and combined generation system of the present invention has the following advantages: (i) This invention adds an automatic regulating valve for ammonia water circulation based on the ammonia water process flow. The valve automatically adjusts the ammonia water circulation volume according to the concentration in the intermediate ammonia water tank, thereby improving the accuracy of ammonia water concentration and the quality of ammonia water. A new regulating valve for the cooler outlet is added to automatically adjust and stabilize the ammonia water outlet temperature according to temperature changes, thereby reducing the consumption of circulating water and stabilizing the ammonia water temperature. At the same time, it also stabilizes the flash vapor volume in the intermediate ammonia water tank. The new ammonia water preparation tail gas recovery system recovers and utilizes all effective gases such as purge gas, ammonia, and hydrogen released from the intermediate ammonia water tank during the ammonia water preparation process. This achieves the environmental protection goal of zero emissions from the flare and meets the environmental protection production requirements of zero emissions from the ammonia flare. At the same time, it reduces the waste of effective gases, lowers the consumption of fuel coal, and improves the economic benefits of the product. (II) In the continuous production of ammonia water, the high-concentration ammonia water is cooled by a cooler and then temporarily stored in an intermediate ammonia water tank. The high-concentration ammonia water will flash evaporate a certain amount of ammonia, hydrogen, nitrogen and other gases to produce 25% concentration ammonia water. The flash vapor / tail gas pressure in the intermediate ammonia water tank is about 50 kPa. This part of the flash vapor / tail gas is purified by secondary soft water absorption to recover the flash vapor ammonia loss and produce dilute ammonia water as a by-product, thereby reducing system consumption. (III) The vented air after the ammonia is purified by the second absorption of the present invention is rich in hydrogen and high calorific value combustible gas. The purified hydrogen is sent to the vented air tank for buffering and then sent to the hazardous waste boiler or power boiler to recover the combustible gas heat energy, replace fuel coal, and achieve the purpose of reducing fuel coal consumption again. (iv) This invention, by adding a tail gas absorption tank, recovers and reuses all the flash ammonia in the intermediate ammonia tank, increasing ammonia production and reducing gaseous ammonia consumption by 3-5%; (v) This invention collects the tail gas / vented air (effective gas hydrogen or a small amount of ammonia) after ammonia purification by adding a venting gas holder and sends it to a power boiler to recover combustible gas heat energy, produce steam as a by-product, and reduce the coal consumption for production power. (vi) This invention improves the quality of ammonia water by adding an ammonia water circulation regulating valve, stabilizing the concentration of ammonia water delivered to the outside by ±0.2%, reducing manual adjustment intervention; (vii) By designing and adding a regulating valve for the circulating cooling water outlet, the present invention can adjust the flow rate of the circulating cooling water in the cooler in a timely and effective manner according to the air temperature and temperature changes, thereby reducing the consumption of circulating water, stabilizing the temperature of ammonia water and the amount of flash vapor and tail gas generated, and improving the safe and stable operation of the system.

[0017] Therefore, this invention has the characteristics of reasonable design, simple structure, easy processing, small size, convenient use, and multiple uses, and thus has great value for promotion and use. Attached Figure Description

[0018] The invention will be further described below with reference to the accompanying drawings.

[0019] Appendix Figure 1 A schematic diagram of the combined system for recovering tail gas from ammonia water preparation.

[0020] In the diagram: 1. Ammonia absorber; 2. Soft water flow regulating valve; 3. Gaseous ammonia flow regulating valve; 4. Ammonia water external supply valve; 5. Ammonia water cooler; 6. Ammonia water intermediate tank; 7. Ammonia water intermediate tank pressure gauge; 8. Ammonia water concentration meter; 9. Ammonia water tail gas pipeline; 10. Tail gas absorption tank; 11. Tail gas absorption tank level gauge; 12. Air vent pipeline; 13. Gas holder; 14. Vent valve; 15. Gas holder pressure gauge; 16. Air vent external supply regulating valve; 17. Ammonia water circulation pump; 18. Dilute ammonia water pump; 19. Ammonia water intermediate tank level gauge; 20. Ammonia water circulation pipeline; 21. Circulating cooling water outlet regulating valve. 2. Dilute ammonia water pressure gauge; 23. Demineralized water flow meter; 24. Gaseous ammonia flow meter; 25. Ammonia water thermometer; 26. Vent air flow meter; 27. Demineralized water regulating valve; 28. Dilute ammonia water concentration meter; 29. ​​Dilute ammonia water external supply regulating valve; 30. Gas holder height gauge; 31. Ammonia water circulation regulating valve; 32. Demineralized water input pipeline; 33. Gaseous ammonia input pipeline; 34. Ammonia water output pipeline; 35. Ammonia water external supply pipeline; 36. Ammonia water intermediate tank output pipeline; 37. Demineralized water inlet pipeline; 38. Dilute ammonia water output pipeline; 39. Vent air supply to flare pipeline; 40. Vent air supply to boiler pipeline. Detailed Implementation

[0021] The following detailed description of an ammonia preparation tail gas recovery and combined generation system of the present invention is provided with reference to the accompanying drawings and specific embodiments.

[0022] In the description of this invention, it should be understood that the terms "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0023] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. Example

[0024] As attached Figure 1As shown, this embodiment provides a combined system for recovering ammonia water preparation tail gas. Its structure includes an ammonia absorber 1, an ammonia water intermediate tank 6, a tail gas absorption tank 10, and a gas holder 13. An ammonia inlet pipe 33 is installed at the ammonia inlet located slightly below the center on one side of the ammonia absorber 1. An ammonia flow regulating valve 3 and an ammonia flow meter 24 are installed on the ammonia inlet pipe 33. A demineralized water inlet pipe 32 is installed at the upper center on the other side of the ammonia absorber 1. A soft water flow regulating valve 2 and a demineralized water inlet pipe 32 are installed on the soft water inlet pipe 32. A demineralized water flow meter 23 is installed on channel 32; an ammonia water circulation pipe 20 is installed on the other side of the ammonia absorber 1, near the lower middle position; the bottom outlet of the ammonia absorber 1 is connected to the ammonia water intermediate tank 6 via an ammonia water output pipe 34, an ammonia water cooler 5 is installed on the ammonia water output pipe 34, the ammonia water output pipe 34 is connected to the shell-side inlet of the ammonia water cooler 5, a circulating cooling water outlet regulating valve 21 is installed on the tube-side pipe of the ammonia water cooler 5, and an ammonia water thermometer 25 is installed on the ammonia water output pipe 34; the connection between the ammonia water intermediate tank 6 and the ammonia water output pipe 34 is located at the ammonia water... An ammonia water intermediate tank output pipe 36 is installed at the upper middle position on one side of the intermediate tank 6 and at the lower middle position on the other side of the ammonia water intermediate tank 6. One end of the ammonia water intermediate tank output pipe 36 is connected to the ammonia water intermediate tank 6, and the other end of the ammonia water intermediate tank output pipe 36 splits into two paths: one path is connected to the ammonia water circulation pipe 20, which is connected to the ammonia absorber 1 and is equipped with an ammonia water circulation regulating valve 31; the other path is connected to the ammonia water external delivery pipe 35, which is equipped with an ammonia water external delivery valve 4; the top of the ammonia water intermediate tank 6... An ammonia water tail gas pipe 9 is installed at the tail gas outlet. One end of the ammonia water tail gas pipe 9 is connected to the ammonia water intermediate tank 6, and the other end of the ammonia water tail gas pipe 9 is inserted into the bottom of the tail gas absorption tank 10. A demineralized water inlet pipe 37 is installed at the upper middle part of one side of the tail gas absorption tank 10. A demineralized water regulating valve 27 is installed on the demineralized water inlet pipe 37. The top of the tail gas absorption tank 10 is connected to the gas holder 13 through an air release pipe 12. An air release pipe 40 is installed at the lower middle part of one side of the gas holder 13. An air release regulating valve 16 is installed on the air release pipe 40.

[0025] In this embodiment, an ammonia water intermediate tank level gauge 19 is installed at the lower center of one side of the ammonia water intermediate tank 6, and an ammonia water concentration gauge 28 is installed at the lower center of the other side of the ammonia water intermediate tank 6. The ammonia water concentration gauge 28 is located above the ammonia water intermediate tank output pipe 36, and an ammonia water circulation pump 17 is installed on the ammonia water intermediate tank output pipe 36. An ammonia water intermediate tank pressure gauge 7 is installed on one side of the top of the ammonia water intermediate tank 6.

[0026] In this embodiment, a dilute ammonia water output pipe 38 is installed at the lower middle position on one side of the tail gas absorption tank 10. The dilute ammonia water output pipe 38 is arranged opposite to the demineralized water inlet pipe 37, and one end of the dilute ammonia water output pipe 38 is connected to the tail gas absorption tank 10. The other end of the dilute ammonia water output pipe 38 is connected to the ammonia water intermediate tank 6 through a dilute ammonia water pump 18, a dilute ammonia water pressure gauge 22, and a dilute ammonia water external delivery regulating valve 29 in sequence. A tail gas absorption tank level gauge 11 is installed on the tail gas absorption tank 10.

[0027] In this embodiment, an air flow meter 26 is installed on the ammonia tail gas pipeline 9.

[0028] In this embodiment, a gas holder height gauge 30 is installed at the middle of one side of the gas holder 13; a gas holder pressure gauge 15 is installed at one side of the top of the gas holder 13; and a venting flare pipe 39 is installed on the other side of the top of the gas holder 13, with a venting valve 14 installed on the venting flare pipe 39.

[0029] In this embodiment, during the ammonia water preparation process, gaseous ammonia is supplied as raw material from the third stage of the coal chemical ammonia synthesis machine. The gaseous ammonia pressure is 0.45 MPa and the temperature is 8°C. Detected by a gaseous ammonia flow meter, the gaseous ammonia flow regulating valve 3 sends the gaseous ammonia into the lower ammonia inlet of the ammonia absorber 1 via the gaseous ammonia input pipe 33. In the ammonia absorber 1, it comes into reverse contact with dilute ammonia water from the ammonia water circulation pipe 20 and demineralized water, measured by the demineralized water flow meter 23 and input through the demineralized water input pipe 32 and the soft water flow regulating valve 2. The ammonia absorber 1 is equipped with structured stainless steel packing to achieve uniform contact and absorption of gaseous ammonia with dilute ammonia water and demineralized water, producing ammonia water. The ammonia water then enters the ammonia water output pipe 34. The shell-side inlet of cooler 5 is in a wall-type heat exchange with the circulating water flowing into the tube side of ammonia cooler 5 through the tube side pipes of ammonia cooler 5 and the circulating cooling water outlet regulating valve 3. After the dilute ammonia water is cooled, it is sent to the upper inlet of ammonia water intermediate tank 6 through ammonia water output pipe 34. After buffering and flash evaporation, the dilute ammonia water is mixed with the dilute ammonia water produced by the tail gas absorption tank 10 after being pressurized by dilute ammonia water pump 18. The mixed ammonia water is pressurized by ammonia water circulation pump 17. The ammonia water that does not meet the standard is sent to the upper inlet of ammonia absorber 1 through ammonia water circulation pipe 20 to enter the next ammonia water preparation cycle. The ammonia water that meets the standard is sent to the next section for use through ammonia water external delivery regulating valve 4.

[0030] In this embodiment, the ammonia- and hydrogen-containing tail gas from the flash evaporation of the ammonia intermediate tank 6 is inserted into the bottom of the tail gas absorption tank 10 through the tail gas outlet at the top of the ammonia intermediate tank 6 and the ammonia tail gas pipe 9. The tail gas absorption tank 10 is filled to the preset liquid level by the demineralized water supplied by the demineralized water regulating valve 27. The gaseous ammonia in the tail gas is gradually absorbed by the demineralized water in the tail gas absorption tank 10 from the bottom up. After the ammonia is purified, the hydrogen- and nitrogen-containing vented air is sent into the gas inlet through the vented air pipe 12. The gas is buffered and separated by the gas holder 13. The hydrogen-containing vented air is sent to the boiler for combustion through the vented air external supply regulating valve 16.

[0031] In this embodiment, under steady-state operating conditions, the target of a stable ammonia concentration of 25% is achieved by setting the ratio of gaseous ammonia to demineralized water at the inlet of ammonia absorber 1 to 1:4. The opening of soft water flow regulating valve 2 is controlled by demineralized water flow meter 23, and the opening of gaseous ammonia flow regulating valve 3 is controlled by gaseous ammonia flow meter 24; specifically: The ammonia concentration meter is monitored to be within the set target of 25±0.2%. The ratio of gaseous ammonia to demineralized water is set to 1:4 as much as possible according to the load. When the ammonia concentration meter is lower than 24.8% or higher than 25.2%, the opening of the ammonia circulation regulating valve 31 is adjusted by cascade control to keep the ammonia concentration accuracy within the set target.

[0032] In this embodiment, the ammonia water temperature output by the ammonia absorber 1 is 50-70℃. The ammonia water thermometer 25 is monitored to ensure that the temperature is stable at 35-40℃. The flow rate of the circulating cooling water is controlled by adjusting the flow rate of the circulating cooling water outlet valve 21 to keep the temperature of the ammonia water entering the intermediate ammonia water tank 6 within the set range. When the winter temperature is low and the ammonia water thermometer is below 35℃, the opening of the circulating cooling water outlet valve 21 is reduced to decrease the circulating cooling water flow rate and reduce the replenishment and consumption of circulating water. When the summer temperature causes the ammonia water thermometer to exceed 40℃, the opening of the circulating cooling water outlet valve 21 is increased to increase the circulating cooling water flow rate and keep the ammonia water temperature between 35-40℃.

[0033] In this embodiment, the level gauge 19 of the ammonia intermediate tank is controlled between 25% and 80% by the ammonia supply valve 4. When the ammonia intermediate tank level gauge 19 shows below 25%, the ammonia supply valve 4 is adjusted to lower the level, thereby raising the level of the ammonia intermediate tank 6; when the ammonia intermediate tank level gauge 19 shows above 80%, the ammonia supply valve 4 is adjusted to increase the ammonia supply.

[0034] In this embodiment, by controlling the index of the dilute ammonia water pressure gauge 22 at the outlet of the dilute ammonia water pump 18 to be higher than the index of the pressure gauge 7 of the ammonia water intermediate tank, and controlling the pressure difference to exceed 0.1 MPa, the dilute ammonia water is ensured to be normally delivered into the ammonia water intermediate tank 6, thereby ensuring the stable operation of the tail gas absorption tank 10.

[0035] In this embodiment, the opening of the demineralized water regulating valve 27 is set by the venting air flow meter 26 to control the demineralized water flow rate at the inlet of the tail gas absorption tank 10, and the index of the dilute ammonia concentration meter 28 is controlled between 10% and 15%.

[0036] In this embodiment, the level gauge 11 of the tail gas absorption tank is controlled between 25% and 80%. When the level gauge 11 of the tail gas absorption tank indicates less than 25%, the dilute ammonia water supply regulating valve 29 is adjusted to a smaller value; when the level gauge 11 of the tail gas absorption tank indicates more than 80%, the dilute ammonia water supply regulating valve 29 is adjusted to a larger value.

[0037] In this embodiment, the amount of vented air is adjusted by the venting regulating valve 16 to control the index of the gas holder pressure gauge 15 between 10 and 15 kPa. The index of the gas holder pressure gauge 15 is monitored. When the pressure of the gas holder pressure gauge 15 is less than 10 kPa, the vent valve 14 at the top of the gas holder 13 is fully closed, and the venting regulating valve 16 is adjusted to a smaller value. When the pressure of the gas holder pressure gauge 15 is higher than 15 kPa, the venting regulating valve 16 is first opened and then gradually opened to a larger value. When the pressure of the gas holder pressure gauge 15 is still higher than 15 kPa, the vent valve 14 is then adjusted to a larger value and gradually opened to a larger value, so that the pressure of the gas holder 13 is controlled within the specified range.

[0038] In this embodiment, the indicator of the gas holder height gauge 30 is monitored to be between 30% and 75%. When the indicator of the gas holder height gauge 30 is lower than 30%, the venting air supply regulating valve 16 is adjusted to reduce the amount of venting air supplied. When the indicator of the gas holder height gauge 30 is higher than 75%, the venting air supply regulating valve 16 is adjusted to increase the amount of venting air supplied to the boiler.

[0039] In this embodiment, the ammonia concentration is the controlled variable, and the flow rates of the demineralized water and gaseous ammonia pipelines are secondary variables in the cascade control system. The flow rate is introduced as a feedforward signal, thus forming a dual-impulse control system. By setting the action index of the ammonia water circulation regulating valve 31, the ammonia water concentration accuracy is stabilized at ±0.2%. Based on the concentration index, the ratio of the demineralized water flow rate to the gaseous ammonia flow rate is set. When the detected ammonia water concentration is higher than the set concentration deviation within 0.3%, the opening of the ammonia water circulation regulating valve 31 and the external ammonia water regulating valve 4 remains unchanged. When the detected concentration index is below the negative deviation or greater than -0.3%, the opening of the ammonia water circulation regulating valve 31 is gradually adjusted from 0% to 30%, and the opening of the external ammonia water regulating valve 4 is gradually reduced from 70% to 40%. When the detected concentration index is above the positive deviation or greater than +0.3%, the opening of the ammonia water circulation regulating valve 31 is gradually adjusted from 30% to 0%, and the opening of the external ammonia water regulating valve 4 is gradually reduced from 40% to 70%. Through the split-range control of the regulating valves, detection and action errors caused by large fluctuations in flow rate due to changes in system operating conditions are reduced, ensuring that the ammonia water preparation tail gas green recovery production unit can operate in a safe and stable state.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A combined system for recovering and generating ammonia water preparation tail gas, characterized in that, The system includes an ammonia absorber, an intermediate ammonia tank, a tail gas absorption tank, and a gas holder. An ammonia inlet pipe with a flow regulating valve is located at the ammonia inlet on one side of the ammonia absorber, near the lower center. A demineralized water inlet pipe with a soft water flow regulating valve is located on the other side of the ammonia absorber, near the upper center. An ammonia circulation pipe is located on the other side of the ammonia absorber, near the lower center. The ammonia outlet at the bottom of the ammonia absorber is connected to the intermediate ammonia tank via an ammonia outlet pipe. An ammonia cooler is installed on the ammonia outlet pipe, which is connected to the shell-side inlet of the ammonia cooler. A circulating cooling water outlet regulating valve is installed on the tube-side pipe of the ammonia cooler, and an ammonia thermometer is installed on the ammonia outlet pipe. The connection between the ammonia intermediate tank and the ammonia output pipeline is located at the upper-middle position on one side of the ammonia intermediate tank. The ammonia output pipeline is located at the lower-middle position on the other side of the ammonia intermediate tank. One end of the output pipeline is connected to the ammonia intermediate tank, and the other end splits into two paths: one is an ammonia circulation pipeline connected to the ammonia absorber and equipped with an ammonia circulation regulating valve; the other is an ammonia external delivery pipeline equipped with an ammonia external delivery valve. A tail gas pipeline is installed at the tail gas outlet at the top of the ammonia water intermediate tank. One end of the tail gas pipeline is connected to the ammonia water intermediate tank, and the other end is inserted into the bottom of the tail gas absorption tank. A demineralized water inlet pipeline is installed at the upper middle part of one side of the tail gas absorption tank, and a demineralized water regulating valve is installed on the demineralized water inlet pipeline. The top of the tail gas absorption tank is connected to the gas holder through an air venting pipeline. An air venting pipeline is installed at the lower middle part of one side of the gas holder, and an air venting regulating valve is installed on the air venting pipeline.

2. The ammonia water preparation tail gas recovery and combined generation system according to claim 1, characterized in that, A gaseous ammonia flow meter is installed on the gaseous ammonia input pipeline; A demineralized water flow meter is installed on the demineralized water input pipeline.

3. The ammonia water preparation tail gas recovery and combined generation system according to claim 1 or 2, characterized in that, An ammonia water intermediate tank level gauge is installed at the lower center of one side of the ammonia water intermediate tank, and an ammonia water concentration gauge is installed at the lower center of the other side of the ammonia water intermediate tank. The ammonia water concentration gauge is located above the ammonia water intermediate tank output pipe, and an ammonia water circulation pump is installed on the ammonia water intermediate tank output pipe. An ammonia water intermediate tank pressure gauge is installed on one side of the top of the ammonia water intermediate tank.

4. The ammonia water preparation tail gas recovery and combined generation system according to claim 3, characterized in that, A dilute ammonia water output pipe is installed on one side of the tail gas absorption tank, near the lower center. The dilute ammonia water output pipe is positioned opposite the demineralized water inlet pipe, with one end of the dilute ammonia water output pipe connected to the tail gas absorption tank. The other end of the dilute ammonia water output pipe is connected to the ammonia water intermediate tank via a dilute ammonia water pump, a dilute ammonia water pressure gauge, and a dilute ammonia water external delivery regulating valve. A tail gas absorption tank level gauge is installed on the tail gas absorption tank.

5. The ammonia water preparation tail gas recovery and combined generation system according to claim 4, characterized in that, An air flow meter is installed on the ammonia tail gas pipeline.

6. The ammonia water preparation tail gas recovery and combined generation system according to claim 5, characterized in that, A gas holder height gauge is installed at the middle of one side of the gas holder; a gas holder pressure gauge is installed at one side of the top of the gas holder; and a venting flare pipe is installed on the other side of the top of the gas holder, with a venting valve installed on the venting flare pipe.

7. The ammonia water preparation tail gas recovery and combined generation system according to claim 6, characterized in that, In the ammonia production process, gaseous ammonia is supplied as raw material from the third stage of the coal chemical ammonia synthesis machine. The gaseous ammonia pressure is 0.45 MPa and the temperature is 8℃. Detected by a gaseous ammonia flow meter, the gaseous ammonia flow regulating valve sends the gaseous ammonia into the lower ammonia inlet of the ammonia absorber through the gaseous ammonia input pipeline. In the ammonia absorber, it comes into counter-current contact with dilute ammonia water from the ammonia water circulation pipeline and demineralized water water measured by a demineralized water flow meter and input through the demineralized water input pipeline and soft water flow regulating valve. The ammonia absorber is equipped with structured stainless steel packing to achieve uniform contact and absorption of gaseous ammonia with dilute ammonia water and demineralized water, producing ammonia water. The ammonia water then enters the ammonia water output pipeline. The shell-side inlet of the cooler exchanges heat with the circulating water flowing into the tube side of the ammonia cooler through the tube side pipes of the ammonia cooler and the circulating cooling water inlet control valve. After the dilute ammonia water is cooled, it is sent to the upper inlet of the ammonia water intermediate tank through the ammonia water output pipe. After buffering and flash evaporation, the dilute ammonia water is mixed with the dilute ammonia water produced by the ammonia gas recovered and absorbed by the tail gas absorption tank. After being pressurized by the dilute ammonia water pump, the mixed ammonia water is pressed by the ammonia water circulation pump. The ammonia water that does not meet the standard is sent to the upper inlet of the ammonia absorber through the ammonia water circulation pipe to enter the next ammonia water preparation cycle. The ammonia water that meets the standard is sent to the next section for use through the ammonia water external delivery regulating valve. The ammonia- and hydrogen-containing tail gas from the flash evaporation of the ammonia water intermediate tank is inserted into the bottom of the tail gas absorption tank through the tail gas outlet at the top of the ammonia water intermediate tank and the tail gas pipeline. The tail gas absorption tank is filled to the preset liquid level by the demineralized water supplied by the demineralized water regulating valve. The gaseous ammonia in the tail gas is gradually absorbed by the demineralized water in the tail gas absorption tank from the bottom to the top. After the ammonia is purified, the hydrogen- and nitrogen-containing vented air is sent to the gas inlet through the vented air pipeline. The gas is buffered and separated by the gas holder. The hydrogen-containing vented air is sent to the boiler for combustion through the vented air external valve.

8. The ammonia water preparation tail gas recovery and combined generation system according to claim 7, characterized in that, When the system is in steady-state operation, the target ammonia concentration of 25% is achieved by setting the ratio of gaseous ammonia to demineralized water at the ammonia absorber inlet to 1:

4. The opening of the soft water flow regulating valve is controlled by the demineralized water flow meter, and the opening of the gaseous ammonia flow regulating valve is controlled by the gaseous ammonia flow meter; specifically: When the ammonia concentration meter is within the set target of 25±0.2%, the ratio of gaseous ammonia to demineralized water should be set to 1:4 as much as possible according to the load. When the ammonia concentration meter is lower than 24.8% or higher than 25.2%, the opening of the ammonia circulation regulating valve should be adjusted through cascade control to keep the ammonia concentration accuracy within the set target.

9. The ammonia water preparation tail gas recovery and combined generation system according to claim 8, characterized in that, The ammonia water temperature output by the ammonia absorber is 50-70℃. The ammonia water thermometer reading is monitored to ensure it remains stable at 35-40℃. The flow rate of the circulating cooling water is controlled by adjusting the flow rate of the circulating cooling water outlet valve to keep the temperature of the ammonia water entering the intermediate tank within the set range. When the winter temperature is low and the ammonia water thermometer reading is below 35℃, the opening of the circulating cooling water outlet valve is reduced to decrease the circulating cooling water flow rate and reduce circulating water replenishment and consumption. When the summer temperature causes the ammonia water thermometer reading to exceed 40℃, the opening of the circulating cooling water outlet valve is increased to increase the circulating cooling water flow rate and keep the ammonia water temperature between 35-40℃. The ammonia water supply regulating valve is used to control the level gauge reading in the intermediate ammonia tank between 25% and 80%. When the level gauge reading is below 25%, the ammonia water supply regulating valve is adjusted downwards to raise the level in the intermediate ammonia tank; when the level gauge reading is above 80%, the ammonia water supply regulating valve is adjusted upwards to increase the ammonia water supply.

10. The ammonia water preparation tail gas recovery and combined generation system according to claim 9, characterized in that, The system ensures that the dilute ammonia water pressure gauge at the outlet of the dilute ammonia water pump is higher than the pressure gauge at the intermediate ammonia water tank, and that the pressure difference exceeds 0.1 MPa, thereby ensuring that the dilute ammonia water is normally delivered into the intermediate ammonia water tank and thus ensuring the stable operation of the tail gas absorption tank. The opening of the demineralized water regulating valve is set by the air venting flow meter to control the demineralized water flow at the inlet of the tail gas absorption tank, and the index of the dilute ammonia concentration meter is controlled between 10% and 15%. Keep the level gauge reading of the exhaust gas absorption tank between 25% and 80%. When the level gauge reading is below 25%, reduce the dilute ammonia water supply regulating valve; when the level gauge reading is above 80%, increase the dilute ammonia water supply regulating valve. Adjust the amount of vented air by using the venting valve to control the pressure gauge reading between 10 and 15 kPa. Monitor the pressure gauge reading. When the pressure gauge reading is less than 10 kPa, fully close the venting valve at the top of the gas holder and reduce the venting valve. When the pressure gauge reading is higher than 15 kPa, first open the venting valve and then gradually open it fully. If the pressure gauge reading is still higher than 15 kPa, then increase the venting valve and gradually open it fully to control the gas holder pressure within the specified range. The readings of the gas holder height gauge should be between 30% and 75%. When the readings are below 30%, adjust the venting valve to reduce the amount of vented air. When the readings are above 75%, adjust the venting valve to increase the amount of vented air sent to the boiler.

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