Thread Content
Urea general control post operating procedures 1. The main task of the position is to send the liquid ammonia, CO2 and recycled ammonium carbamate solution delivered from the synthesis workshop into the synthesis tower in a certain proportion, and synthesize urea under the conditions of 19.6MPa and 180~190℃. The unreacted ammonia, CO2 and unreacted ammonium carbamate solution are The ammonium carbamate converted into urea is decomposed and recovered in the first and second stages and returned to the synthesis tower. The urea solution is evaporated and concentrated to a molten state and granulated to make urea products. This position provides centralized control and adjustment of the entire workshop equipment, main process conditions and instruments. 2. External contact 2.1. Regularly contact various positions in the urea workshop and issue corresponding operating instructions. 2.2. Regularly contact the branch factory production dispatch to determine or adjust the production load, and supply production raw materials, water, electricity, steam, etc. through dispatch contact. 2.3. Under the leadership of the workshop and squad leader, in special circumstances (such as power outage, serious accidents involving CO2, steam cooling water and equipment, etc.), each position should be notified of emergency shutdown and reported to the relevant departments in a timely manner. 3. Process indicators 3.1. Temperature ⑴ The temperature of the top of the synthesis tower is 185~189℃ and the bottom is 174~180℃ ⑵ The temperature of urine at the outlet of the one-part heater TRC-301 145~165℃ ⑶ The temperature of urine at the outlet of the two-part tower TRC-303 125~142℃ ⑷ The temperature at the bottom of the first-absorption tower TRC-304 85~100℃ ⑸Ammonia cooler outlet gas temperature TRCA-305 20~40℃ ⑹Inert scrubber outlet ammonia water temperature TRCA-306 30~45℃ ⑺Dimethyl liquid temperature 35~45℃ ⑻Ammonia water temperature 20~40℃ ⑼First absorption tower outlet gas temperature ≤50℃ ⑽Desorption tower bottom temperature 142~147℃ 3.2. Pressure ⑴Synthesis tower pressure PRCA-204 19.3~19.9MPa ⑵First-stage circulation system pressure PRC-301 1.6~1.8MPa ⑶Second-stage circulation system pressure PRC-302 0.15~0.25MPa ⑷Desorption tower pressure PRC-701 ≤0.40MPa ⑸Inlet workshop steam pressure PRC-901 0.8～1.3MPa ⑹ Cooling water pressure (12.00m floor) ≥0.25MPa 1.1. Flow rate ⑴ Ammonia flow rate into urea synthesis tower FI/HIC-202 2.0～2.2 m3/tur ⑵ Air flow rate into one-point heater FR-301 1.5～2 Nm3/tur ⑶Reflux ammonia flow rate at the top of the first absorption tower FR/HIC-302 0.3～0.7 m3/tur ⑷Second cycle and one cooler inlet liquid flow rate FI/HIC-304 0.05～0.15 m3/tur ⑸Second cycle and secondary cooler inlet liquid flow rate FI/HIC-305 0.05～0.1 m3/tur ⑹Desorption ammonium bicarbonate liquid flow rate FI/HIC-701 0.4～0.65m3/tur ⑺Desalted water flow rate entering the workshop FR-903～2.5m3/tur ⑻Steam condensate flow rate FR-904 leaving the workshop 1.0～1.8 m3/tur 1.2. Liquid level ⑴Liquid ammonia buffer tank level LRCA-301 30～60% ⑵Pre-distillation tower liquid level LRC-302 10~30% ⑶Two-part tower liquid level LRC-303 5~30% ⑷First-suction tower liquid level LRC-304 30~50% ⑸One-part heater liquid level tank LRC-305 30~80% ⑹Two-circulation and one-cooler liquid level LRCA-306 Middle part of sight glass 50-95% ⑺Two-cycle and two-cooler liquid level LRCA-307 50~95% ⑻Desorption tower liquid level LICA-701 20~50% ⑼Condensate tank liquid level ≤90% 1.3. Components ⑴Synthesis tower feed NH3/CO2 3.7~4.2 H2O/CO2 0.5~0.8 ⑵First liquid component NH3 42~44% CO2 32~34% ⑶Dimethyl liquid component NH3 38~42% CO2 17~19% ⑷Ammonia water NH3 at the outlet of the second circulation and secondary cooling 30~35% CO2 ≤3% ⑸Waste liquid NH3 at the outlet of the desorption tower ≤0.05% ⑹Gas phase NH3 at the outlet of the desorption tower condensate 50% CO2 10% ⑺CO2 in the gas phase at the outlet of the first absorption tower ≤100ppm ⑻ CO2 ≥ 95.7% (v) O2 0.4~0.6% (v) H2S ≤ 10mg/m3 in the CO2 gas entering the urea synthesis tower (9) Urine tower leak detection steam ammonia content ≤ 0.01% (Wt) (10) Nickel content of finished urea ≤ 0.2PPm 1. Operation method 1.1. Normal start-up 1.1.1. General preparations 1.1.1.1 . Check whether the equipment, reports, fire protection and protective equipment of this position are complete, complete and usable. 1.1.1.2 . Contact dispatch to learn about the supply of water, electricity, gas (steam), instrument air and the production of ammonia. Contact the instrument engineer to activate and check all instruments and automatic control valves. The audible and visual alarm signals should be in good condition. 1.1.2. Steam induction 1.1.2.1 . Contact the circulation, evaporation, and pump room positions to make preparations for receiving steam. 1.1.2.2 . Contact dispatch to send steam. 1.1.2.3 . Assist the circulation in all tasks of introducing steam into the system. 1.1.2.4 . Preheat pipes and equipment. 1.1.3. Heating of synthesis tower 1.1.3.1 . After receiving the operation notice from the dispatcher about the temperature rise of the synthesis tower, contact the circulation position to prepare for the temperature rise. 1.1.3.2 . Open the diversion valve at the bottom of the synthesis tower and the stop valve in front of the PV-204 pressure regulating valve at the top. Open the steam main valve. After draining the liquid in the channel, introduce the steam to the top of the synthesis tower. 1.1.3.3 . Close contact with the circulation position, pay attention to controlling the amount of steam entering the synthesis tower, and strictly control the heating rate at 6~8℃/h according to the temperature at the top of the tower. When the temperature at the bottom of the synthesis tower begins to rise, use the bottom temperature as a reference to control the heating rate, and keep the temperature difference between the tower and the tower wall within 50℃. 1.1.3.4 . When the temperature at the top and bottom of the synthesis tower rises to 150°C, you can close the steam inlet valve at the top of the tower to maintain the temperature, notify the maintenance worker to tighten the large cover of the synthesis tower and the upper and lower pipe flanges evenly, and wait for the start of the operation. 1.1.4. Preparation for original drive 1.1.4.1 . Understand the pressure test conditions after maintenance of synthesis, decomposition recovery, desorption and other systems and whether the tower preheating temperature rise reaches 150°C. Contact the instrument technician to turn on all instruments, and cooperate with the circulation staff to check whether each regulating valve is functioning properly. 1.1.1.1 . It is easy to use. After inspection, put the regulating valve in manual closed state. 1.1.1.2 . Check the sound and light alarm signals and start and stop signals. 1.1.1.3 . Check whether the PV-204 pressure regulating valve at the outlet of the synthesis tower is leaking. 1.1.2. Pressurization 1.1.2.1 . Contact dispatch to send air to the urea workshop. 1.1.2.2 . Contact the circulation station to pressurize one section with air, and open the top and bottom return ammonia diversion valves to drain away the accumulated water. Contact the pump room station to open the ammonia pump discharge valve, and drain away the accumulated water in the ammonia pump inlet pipe and the pump body. 1.1.2.3 . Contact the circulation station to pressurize the second stage. 1.1.2.4 . When the pressure in the first stage reaches 0.3~0.5MPa, and when the pressure in the second stage reaches 0.15MPa, pressurization stops. 1.1.3. Filling 1.1.3.1 . Contact the dispatcher to send desalted water into the boundary area, notify the pump room, and the circulating evaporation post to make preparations for filling the post. 1.1.3.2 . Notify the pump room to start the evaporative condensate pump, fill the second circulation and one cooling, and the second circulation and the second cooling. 1.1.3.3 . Contact the pump room and circulation station to start the ammonia water pump to fill the first suction tower. 1.1.4. Lead cooling water 1.1.4.1 . Contact dispatch to deliver cooling water, and notify each post to make preparations for diverting cooling water. 1.1.4.2 . Supply water to each cooler and condenser, and adjust the cooling water volume of each cooler. 1.1.5. System ammonia introduction 1.1.5.1 . Notify the pump room post to start the tail suction pump and deliver liquid to the tail suction tower. 1.1.5.2 . After receiving the notice from the squad leader, notify the circulation station to open the stop valves before and after the ammonia filter and the stop valve of the liquid level regulating valve LV-301, and slowly open the LV-301 to introduce ammonia into the system. When the ammonia buffer tank liquid level stabilizes at 40-50%, and compare it with the on-site liquid level. Put the regulating valve into automatic control, and gradually increase the pressure to 1.3MPa, then put the pressure regulating valve (PV-301) into automatic control. 1.1.6. Synthesis tower ammonia pressure boost 1.1.6.1 . When the synthesis tower is preheated to 150°C, contact the circulation and pump room posts to close the synthesis tower heating steam valve and the condensate discharge valve at the bottom of the tower. 1.1.6.2 . Contact the circulation and pump room positions to start the liquid ammonia pump and fully open the ammonia pump auxiliary line. 1.1.6.3 . Contact the circulation post to open the medium-pressure steam inlet valve of the ammonia preheater and the front and rear stop valves of the ammonia preheater trap. When ammonia enters the tower, use the ammonia pump frequency converter to adjust the ammonia flow into the tower to maintain the temperature of the ammonia preheater and the combined 1.1.1.1 . The tower temperature is 150℃. 1.1.1.2 . Control the pressure of the synthesis tower to rise slowly, open the PV-204 regulating valve at the outlet of the synthesis tower, and replace the steam in the tower. After the steam conversion in the tower is completed, close the synthesis tower outlet regulating valve PV-204. When the pressure of the synthesis tower rises to 8.0MPa, contact the circulation station to detect steam leaks. 1.1.2. Feeding 1.1.2.1 . After receiving the feed notification, contact the No. 1 pump in the pump room to send the No. 1 liquid into the tower at a low speed. At the same time, notify the circulation post to turn off the medium-pressure steam of the ammonia preheater and use steam condensate to reduce the temperature of the ammonia preheater to 40~60°C. Depending on the liquid level in the No. 1 suction tower, switch the No. 2 pump to the main line. 1.1.2.2 . Contact the pump room to send CO2 into the tower, and adjust the amount of ammonia into the tower according to the CO2 compressor air volume and the temperature at the bottom of the synthesis tower. 1.1.2.3 . Turn off PV-204 and gradually increase the synthesis tower pressure. When the pressure of the synthesis tower reaches 18MPa, turn on the PV-204 appropriately and slow down the pressure increase. After confirming the discharge from the synthesis tower, raise the pressure to 19.6MPa. After the manual control is stable, put the regulating valve into automatic control and put the external cooler circulation pump into operation. Use HIC-301 to control the temperature of the gas-liquid mixture at the outlet of the external cooler to be between 90 and 100°C. Use top ammonia and ammonia water to adjust the temperature of the fine washing section of the first absorption tower to ≤55°C. 1.1.3. Discharge from synthesis tower 1.1.3.1 . When the output from the synthesis tower is stable and the liquid level in the pre-distillation tower reaches the liquid level, the circulation post is notified to open the front and rear stop valves of TRC-301, TRC-303, LRC-302, LRC-303 and other regulating valves, and the evaporation post is notified to send the urine to the urine tank through flash evaporation, and gradually raise the temperatures of the first heater, the second tower, the second circulation and one cooling, and the second circulation and two cooling to the target. The temperature increase of the first heater should be carried out slowly depending on the temperature of the first absorption tower. After the temperature is normal, the temperature regulating valve of the first heater and the regulating valve of the second heater should be put into automatic control. Control the liquid levels of the pre-distillation tower, bisection tower, two-circulation and one-cooling, and two-circulation and two-cooling to the normal position. 1.1.3.2 . Connect the cycle and add anti-corrosion air to the first heater. Before the air is sent, the temperature of the first heater shall not exceed 155℃. 1.1.3.3 . Control the first-stage pressure (PRC-301) at 1.6MPa and the second-stage pressure (PRC-302) at 0.15MPa. After stabilization, turn on automatic control. 1.1.3.4 . After discharging, adjust and control the corresponding revolutions of the first-A pump, the second-A pump, and the ammonia water pump according to the production load to keep the liquid level of the first suction tower stable. By adjusting the top and bottom reflux ammonia flow and HIC-301, the temperature of the first suction tower is controlled and the pressure of one section is raised to 1.65MPa. 1.1.3.5 . Gradually top up the load according to the situation. 1.2. Driving after a short-term parking 1.2.1. Preparation for driving after a short-term parking 1.1.1.1 . The synthesis tower is insulated with heat and pressure, and the decomposition and recovery system is started after emptying and maintenance. In this case, in addition to checking whether the outlet regulating valve of the synthesis tower is in the automatic control position and flexible and easy to use, and whether the discharge pipe of the synthesis tower is unobstructed, the rest can be carried out according to the original start-up preparation steps. 1.1.1.2 . Both the synthesis and decomposition recovery systems are kept warm and pressure before starting. ⑴ Contact the dispatcher to deliver ammonia, contact the circulation post to control the liquid level in the first absorption tower, and check whether the PV-204 regulating valve at the outlet of the synthesis tower is flexible and easy to use and whether the outlet pipe of the synthesis tower is smooth. ⑵Check whether the reflux ammonia pipeline at the top and bottom of the first absorption tower is smooth. ⑶Inform the pump room staff to start the evaporative condensate pump to fill the second circulation and one cooling, and the second circulation and the second cooling to maintain a low liquid level. If necessary, start the ammonia water pump to fill the first suction tower with liquid to maintain a low liquid level. Start a pump cycle. ⑷Turn on the steam preheating equipment of the first heater and the second tower slightly. 1.1.2. Start feeding after short-term parking 1.1.2.1 . After being notified by the shift leader or after the start signal, the synthesis tower first adds ammonia and then CO2. Adjust the ammonia-carbon ratio according to the CO2 gas volume and control the temperature of the synthesis tower. At the same time, pay close attention to the pressure of the synthesis tower to prevent over-temperature and over-pressure. After the pressure of the synthesis tower stabilizes, put the PV-204 pressure regulating valve of the synthesis tower into automatic control. 1.1.2.2 . After feeding, the first pump is transferred to the main line, and the speed of the first and second pumps is adjusted according to the liquid level in the first suction tower. 1.1.2.3 . Other steps can be carried out according to the original start-up and feeding steps. 1.1.2.4 . The operation steps after discharging can be carried out according to the original start-up and discharging operation steps, but the liquid level in the first suction tower must be strictly controlled to prevent the fine washing section of the first suction tower from being filled with liquid due to high liquid level. 1.2. Start up the desorption system 1.2.1. After the system is stable, contact the pump room according to the liquid level of the ammonium bicarbonate tank, and the circulation station is ready for startup. 1.2.2. Contact the circulation station to open the steam inlet valve of the desorption tower, open the vent valve of the desorption gas outlet, and pass steam to preheat the desorption tower. 1.2.3. After preheating is completed, contact the circulation station to open the desorption tower liquid level regulating valve LV-701 front and rear stop valves, the desorption tower ammonium bicarbonate liquid inlet valve and the desorption tower pressure regulating valve PIC-701 front and rear stop valves. 1.2.4. The station in the pump room starts the desorption pump to deliver liquid to the desorption tower. After adjusting the desorption volume and the temperature in the middle of the desorption tower to the process indicators, TIC-701 and PV-701 are put into automatic control. After the liquid level in the desorption tower is stabilized, LV-701 is put into automatic control. 1.2.5. After desorption and feeding, pay attention to the changes in the components and liquid level of the second circulation and one cooling, and promptly adjust the amount of water added to the second circulation and one cooling. 1.3. Parking 1.3.1. Long-term parking. After receiving the long-term parking notice from the shift leader, contact the circulation station to stop the desorption system and the evaporation station to stop evaporation. 1.1.1.1 . Hair system, increase the amount of air entering the synthesis tower. ⑴Manually close the steam regulating valve entering the desorption tower, the ammonium bicarbonate liquid flow remote control valve, and open the gas phase vent valve. ⑵Notify the cycle to close the TIC-701, PV-701, and LV-701 shut-off valves. ⑶Drain the liquid in the desorption tower. 1.1.1.2 . A stop signal will be issued after the desorption system is stopped. 1.1.1.3 . Manually close the ammonia buffer tank inlet liquid level regulating valve (LV-301). 1.1.1.4 . The synthesis tower outlet pressure regulating valve (PV-204) was changed to manual control to maintain the original valve opening. 1.1.1.5 . After the liquid ammonia stops entering the tower, the ammonia pump is stopped, the CO2 compressor is stopped, and the first pump starts circulating. 1.1.1.6 . Appropriately increase the amount of ammonia entering the first suction tower for dilution, and discharge from the first suction tower to maintain the liquid level. Reduce the amount of ammonia returning from the top and bottom, and stop the external cooler circulation pump as appropriate. 1.1.1.7 . When the pressure of the synthesis tower drops to 8.0MPa, the system is redirected to the second stage for discharge through the circulation and pump room stations, and the pipeline from the top of the synthesis tower in front of the PV-204 valve to the first stage of the decomposition system is flushed until the liquid level is visible on the pre-distillation sight glass. At the same time, notify the circulation post to close the leak detection steam and close the PRC-204, LRC-302, and TIC-301 shut-off valves. 1.1.1.8 . Cut a section of anti-corrosion air. 1.1.1.9 . Depending on the dilution situation of the first suction tower, stop the first and second pumps (or switch to circulation), and finally stop the ammonia water pump and relieve the pressure for a period. 1.1.1.10 . After the synthesis tower is diverted to the second stage for discharge, the discharge valve at the bottom of the tower is used to control the discharge volume. 1.1.1.11 . When the pressure of the synthesis tower drops to 0.3~0.5MPa, the discharge is redirected to the ammonium bicarbonate liquid tank, and the circulation is notified to close the two-stage tower heating steam valve (TV-303), the two-stage tower liquid level regulating valve (LV-303), and the two-stage pressure regulating valve cut-off valve. Stop adding water to the second circulation and one cooling, and the second circulation and secondary cooling. Contact the evaporation station and the pump room station to stop the evaporation condensate pump, and contact the circulation station to flush the urine inlet and outlet lines of the two-phase tower. 1.1.1.12 . When the synthesis tower is emptied and the first stage of pressure relief is completed, contact the circulation and pump room posts to send steam into the tower for replacement. 1.1.1.13 . Stop the tail suction pump at the pump station. 1.1.1.14 . Contact dispatch to stop cooling water, steam, and soft water. Depending on maintenance needs, contact the circulation station to drain the synthesis, decomposition, recycling, and desorption systems cleanly, and replace and clean them with steam or condensate. 1.1.2. Short-term parking 1.1.2.1 . After receiving the short-term parking notice from the shift leader, contact the evaporation station to stop evaporation, and contact the circulating pump room station to stop the desorption system (for parking steps, see desorption parking for long-term parking. After desorption is stopped, a parking signal will be sent. After the three materials stop entering the tower, manually close the outlet regulating valve (PV-204) and ammonia buffer tank of the synthesis tower. 1.1.1.1 . Inlet liquid level regulating valve (LV-301), pre-distillation tower outlet liquid level regulating valve (LV-302), one-stage heater temperature regulating valve (TV-301), two-stage tower outlet liquid level and temperature regulating valve (LV-303 and TV-303), one-stage decomposition and two-stage decomposition pressure regulating valves (PV-301 and PV-302). 1.1.1.2 . Contact the circulation station to flush the discharge pipe of the synthesis tower, and open the pressure regulating valve (PV-204) at the outlet of the synthesis tower before flushing. Add one and two parts water to dilute. 1.1.1.3 . Dilute the first absorption tower, the second circulation and one cooling, and the second circulation and secondary cooling. When the CO2 in the first liquid A is ≤ 10%, contact the pump room to stop the first A pump, the second A pump, the ammonia water pump and the evaporation condensate pump. 1.1.1.4 . The heat preservation and pressure holding time of the synthesis tower during short-term shutdown shall not exceed 24 hours, and the pressure shall not be less than 12.0MPa. Otherwise, the squad leader, dispatcher and relevant leaders should be asked to discharge the synthesis tower. 1.1.1.5 . According to the maintenance needs, contact the recycling station to discharge the first or second section of the decomposition and recovery system, clean it with water and hand it over for maintenance. 1.1.2. Emergency shutdown In the event of ammonia cutoff, CO2 cutoff, power cutoff, water cutoff, steam cutoff, instrument air cutoff, severe overpressure, fire, explosion, etc., emergency shutdown should be adopted and the pump room, compression, evaporation and other positions should be notified quickly. 1.1.2.1 . Power off ⑴ Immediately manually close the pressure regulating valve at the outlet of the synthesis tower (PV-204) and the liquid level regulating valve at the inlet of the ammonia buffer tank (LV-301). ⑵Contact the circulation and pump room positions to activate the backup power supply of the steam condensate pump and flushing water pump, flush the three material pipes and discharge pipes at the inlet of the synthesis tower, and at the same time dilute the first suction tower, and the first and second points of water inlet. After power is turned on, pump A is turned on for circulation. ⑶Other procedures will be followed for short-term parking. 1.1.2.2 . Cut off the cooling water ⑴ Press the emergency stop button and close the PRC-204 regulating valve. ⑵Pay attention to the circulating pressure of the first and second stages, and open manual venting when necessary to prevent overpressure. ⑶Others will be handled according to short-term parking procedures. 1.1.2.3 . Cut off the instrument air ⑴ Press the emergency stop button. ⑵In cooperation with the circulation position, first close the front and rear stop valves of the synthesis tower outlet control valve (PV-204), then close the front and rear stop valves of all control valves with secondary lines, and use the secondary lines to adjust. For control valves with handwheels, use the handwheel to manually control the opening of the control valve. ⑶Others will be handled according to short-term parking procedures. 1.1.1.1 . Cut off steam ⑴ Follow the steps of short-term shutdown step by step according to the temperature conditions of each section. ⑵The system must be properly diluted to prevent pipe blockage. 1.1.1.2 . Fire and explosion ⑴ First press the emergency stop button and manually close PRC-204 and LRC-301. ⑵Assist the squad leader to quickly stop the system, cut off the power supply and explosive gas sources, and use corresponding fire extinguishers to extinguish open flames according to the fire category to prevent the development of accidents. ⑶Others are handled according to short-term parking or long-term parking procedures. 1.1.1.3 . Cut off ammonia ⑴ Immediately stop the ammonia pump with load. ⑵Immediately stop the flow of CO2 and A liquid into the synthesis tower. ⑶According to the dispatching instructions, it will be processed according to short-term parking or long-term parking steps. 1.1.1.4 . Cut off CO2 ⑴ Immediately send an accident stop signal, and the CO2 compressor stops with load. ⑵Stop ammonia and ammonia liquid from entering the urea synthesis tower. ⑶According to the dispatching instructions, it will be processed according to short-term parking or long-term parking steps. 2. Common accident phenomena, causes and treatment methods Causes and treatment methods 1. Overpressure in the synthesis tower ⑴ The tower outlet shut-off valve is not opened or opened too small ⑵ The tower outlet regulating valve head is off or blocked by crystals ⑶ The tower outlet pipe is blocked ⑷ Poor coordination between various positions when turning down the pump ⑸ The regulating valve is malfunctioning (the gas source pipe is broken or leaking) ⑹ CO2 purity drops or too much oxygen is added ⑴ Open the valve quickly or fully open the valve. If the pressure is still too high, stop the operation ⑵ Stop the operation ⑶ Stop the operation ⑷ Pay attention to the tower pressure at each position and cooperate closely ⑸ Contact the instrument for shutdown ⑹ Reduce the load and adjust the CO2 purity degree, adjust the amount of anti-corrosion air 2. The pressure of the synthesis tower is too low ⑴ Significant load reduction ⑵ The internal leakage of the regulating valve is serious ⑴ Adjust as soon as possible to restore the pressure index ⑵ Stop and replace the regulating valve 3. The top of the synthesis tower is over-temperature ⑴ The synthesis tower is over-pressured ⑵ The ammonia preheating temperature is too high ⑶ Enter the tower NH3/ CO2, H2O/CO2 molecular ratio is low ⑴ Process as soon as possible, if the pressure is still too high, stop the treatment ⑵ Reduce the preheating temperature ⑶ Adjust the NH3/CO2 entering the tower, H2O/CO2 molecular ratio 4, the temperature at the top of the synthesis section is too low ⑴ The H2O/CO2 of the synthesis tower is too high ⑵ The ammonia preheating temperature is too low ⑶ Enter the tower NH3/ CO2 is too high ⑷ The purity of CO2 entering the tower is too low ⑴ Reduce the amount of liquid A entering the tower ⑵ Increase the ammonia preheating temperature ⑶ Adjust NH3/CO2 ⑷ Improve CO2 purity