[Request for Upload Summary] Operating Plan for Ammonia Synthesis Tower Position
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Operation plan for the ammonia synthesis tower post. I’m a beginner; please give me lots of guidance. This post was last edited by jyr on 2009-3-13 at 11:37.]
Some concepts regarding the ammonia synthesis tower: internal components, outer cylinder, four layers of packing, packing between the catalyst basket’s central tube and the outer cylinder’s lid; packing between the upper sleeve of the secondary gas inlet gap and the tee fitting; packing between the upper sleeve of the secondary gas outlet gap and the tee fitting; packing between the bypass cold air inlet pipe and the tee fitting; cooling pipe; outer cylinder lid. Last edited by snowdfr on 2009-3-13 20:13.]
Operating Procedures for Synthesis Postion; Operating Procedures for Synthesis Tower Postion. I. Position Operation Method (1) Tasks of this Position: This position represents the final stage in ammonia synthesis production, where a hydrogen-nitrogen mixture of specific proportions, after being purified and refined, is synthesized into ammonia under high temperature and pressure through the catalytic action of a catalyst. (II) Brief description of the process flow: The gas is supplied by a circulation machine; it is cooled in Tower No. 1 before entering the new ammonia cooler. After that, it passes through the original ammonia cooler for further cooling, and then merges with fresh gas to enter Tower No. 2. There, residual liquid ammonia is separated, after which the gas enters Tower No. 1 for heat exchange. As the temperature rises, the gas splits into two streams – one stream exits to an external heat exchanger, while the other stream enters the synthesis tower. The synthetic gas exits the tower through its secondary outlet and goes to an intermediate boiler for heat exchange. From there, it proceeds to another external heat exchanger and then to a water cooler for cooling. After cooling, the gas enters an ammonia separation unit where most of the liquid ammonia is separated out. The resulting liquid ammonia then passes through a manual (or automatic) control valve regulated by a level gauge, before being sent to the main ammonia pipeline and stored in the ammonia tank for measurement. (III) Chemical reaction takes place in the synthesis tower: 3H + N2 → NH3 + Q (high temperature, high pressure, catalyst, exothermic, reversible).
(IV) Specifications of main equipment
| Serial No. | Name | Specifications | Remarks |
|-------------|------|---------------|---------|
| 1 | Synthesis tower | Outer diameter: Φ1000 mm; effective height: 13800 mm. Diameter of catalyst basket: Φ934×16. Upper catalyst height: 5582 mm; lower height: 578 mm. Number of cooling tubes: 62 each of Φ44×2.5, Φ29×2.5, and Φ22×1. Heat exchange area: E = 40 m². Heat exchange height: 236 mm. Number of tubes of Φ10×1.5: 3084; heat exchange area: 224 m². Power of pressure regulator: 650 V, 710 A, 800 KVA. Catalyst loading capacity: 15 t, 3 m³. |
| 2 | Condenser | Outer diameter: Φ900 mm; height: 8210 mm. Double-layer shell-and-tube heat exchanger with a heat exchange area of F = 165 m². 1st condenser; 2nd one is used only for separation. |
| 3 | Ammonia cooler | 628 tubes of Φ25×4; shell-and-tube type with a heat exchange area of F = 226 m². 2 units available. |
| 4 | Ammonia separator | Outer diameter: Φ1000 mm; height: H = 4625 mm. 1 unit. |
| 5 | Water cooler | Horizontal shell-and-tube heat exchanger with a heat exchange area of F = 199 m². 3 units. |
(V) Operating procedures
1. Normal startup
(1) Preparation work: Check whether the system equipment, pipes, and valve connections are secure, whether the blind plates have been installed correctly, and whether water, electricity, and gas supply are functioning properly. Contact the electrician and instrument technician to check whether the electrical equipment and instruments are in good condition and ready for use. Check the protective measures, ensure that the fire-fighting equipment is complete and functional, and that the lighting is suitable for driving. (2) Exhaust replacement: Check the valves: the large valve at the filter outlet, the inlet and outlet valves of the first-stage water cooler of the compressor (for two or more valves), the valve for ammonia production, the large valve on the main pipeline, and the fresh gas vent valve. Valves to be closed: fresh gas ball valve, fresh gas main valve, system bypass valve, main and auxiliary valves at the inlet of the synthesis tower, ball valve at the inlet of the ammonia separator, inlet and outlet main valves of #1, #2, and #3 circulators, vent valves before and after the tower, as well as all ammonia transfer valves and ammonia addition valves. Contact the high-pressure compressor and send air to Section 6 at 8.13; first exhaust the air from the fresh gas main, then close the fresh gas vent valve completely. Open the fresh gas valve, the fresh gas main valve, and the vent valve at the front of the tower to exhaust gas from there; ensure that the O2 concentration is ≤0.2%, which meets the requirements, and then close the vent valve at the front of the tower. Open the main valve at the inlet of the synthesis tower, the ball valve at the inlet of the ammonia separator, and the vent valve at the back of the tower to vent air from behind the tower; the pressure during venting shall not exceed 2.0 Mpa, and the venting time shall be 5 minutes. During pressurized exhaust, when the pressure exceeds 2.1 Mpa, open the ammonia transfer ball valve and inform the ammonia storage facility to open the main ammonia inlet. Check for any gaps at the same time. (3) Leak testing: After the exhaust replacement is successful, close all vent valves and use fresh gas to conduct a leak test across the entire system. Leak testing is carried out at pressures of 10, 20, 25, and 31.5 Mpa, with the pressure being increased by 4 Mpa per minute. If a leak is detected, the pressure must be reduced to below 5 Mpa before the maintenance workshop’s fitter can tighten the bolts; thereafter, leak testing is repeated until the system is leak-free. After the leak test is successful, the rear vent valve on the same tower is used to reduce the system pressure to 6–8 Mpa, in preparation for using the circulation pump and electric furnace to raise the temperature. (4) Increase the temperature to bring the valves to the following states: Valves that should be closed include the valve at the inlet of the synthesis tower, the main valve for fresh gas and the ball valve, all ammonia transfer stop valves, the ammonia addition valve, all vent valves as well as the oil and water release valves, and the ball valve of the circulator. Valves to be opened: main valve at the inlet of the synthesis tower, system bypass valve, ball valve at the ammonia inlet, inlet and outlet valves of the circulator, and auxiliary valve of the circulator. Open the inlet and outlet ball valves of the circulation pump, connect it to the system, and use the bypass valve of the circulation pump as well as the system’s bypass valve to check the circulation rate. The electrician turns on the electric furnace; the first voltage increase should be less than 50V, and subsequent increases must not exceed 20V each time. During the operation of the electric furnace, pay attention to issues such as grounding and short circuits. Stay in touch with the electrical personnel at any time. If any abnormality is detected in the electric furnace, the voltage should be stopped immediately, or the voltage reduced until the furnace is shut down. It is absolutely necessary to ensure that the electric furnace has sufficient supply of air to prevent the heating filaments from overheating and getting damaged. When the circulation machine trips, immediately cut off the power to the electric furnace. Strictly control the heating rate within the specified range. The temperature difference across the catalyst plane must not exceed 10°C. For the temperature rise of the electric furnace, in principle, an operation method with a high furnace power and large circulation volume should be used to ensure an adequate amount of safety air flow. Water is added to the water cooler when the hot spot temperature reaches 100°C, and ammonia is added to the ammonia cooler when the hot spot temperature reaches 350°C. At the same time, it is important to ensure that the liquid ammonia level in the ammonia cooler does not exceed the specified limits. After the temperature rises to 400°C, a compressor can be used to supply air, or the valve labeled “69” connected to 8.13 can be slowly opened until pressure is balanced, after which it can be fully opened to start production. During the valve opening process, the catalyst temperature rose sharply above the specified limit, so the circulation rate was used for control. While pressurizing, start reducing the load on the electric furnace; after the reduction is complete, and once the catalyst and temperature are both back to normal and normal production has resumed, then shut down the electric furnace. (5) Pressurization and temperature rise procedure: In the case of a short-term shutdown with a hotspot temperature above 380°C, depending on the catalyst’s activity, fresh gas can be used for pressurization, utilizing the heat of reaction to raise the catalyst temperature to normal levels. (If the tower is stopped due to mild poisoning, pressurization and temperature increase are prohibited.) The valves in the system are in the following states: Valves that should be open: the ball valve at the fresh gas inlet, the main valve on the ammonia pipeline, and the ammonia transfer valve (this ball valve should be opened when the system pressure reaches 2.0 Mpa; meanwhile, the ammonia storage facility should be informed to open the main inlet valve for ammonia transfer). The inlet and outlet valves of the water coolers for the first stage of the high-pressure compressor (for two or more compressors), as well as the inlet and outlet ball valves of the circulation pump. Valves to be closed: main fresh gas valve, main and auxiliary valves of the synthesis tower, system bypass valves, fresh gas vent valve, inlet and outlet valves of the circulator, ball valve at the inlet of the ammonia separator, vent valves before and after the tower, as well as all ammonia transfer valves and ammonia addition valves. Fill the water cooler with water, and fill the ammonia cooler with ammonia. Open the fresh gas main valve to pressurize the area in front of the tower; once the pressure there is higher than that inside the tower, slightly open the main valve on the tower’s control panel and gradually increase the pressure inside the tower. Prepare the circulation pump and start it to bring the pressure up to match the pressure inside the tower; keep the bypass valve fully open, and keep the inlet and outlet ball valves fully closed. When the rise in temperature stalls, slightly open the ball valve at the inlet of the ammonia separator; depending on the operating conditions, slightly open the vent valve at the back of the tower as well to release some gas, thereby allowing the temperature inside the tower to continue rising steadily. When the catalyst hotspot temperature approaches the target value, the circulator can be introduced into the system, and the load can be increased gradually; subsequently, the circulation rate can be increased step by step based on the catalyst temperature, allowing normal production to resume. Control the ammonia transfer pressure properly. 2. Shutdown (1) Short-term shutdown (planning to resume production in the near future). Before shutting down, raise the catalyst temperature to the upper limit specified; inform the high-pressure compressor to gradually reduce its load, and at the same time close the auxiliary valves. Reduce the circulation rate to the minimum possible, while striving to keep the catalyst temperature from dropping, and pay attention to the ammonia level and the level of the secondary cooling liquid. After the supply of fresh gas has been completely stopped, the circulation machine is disconnected from the system, and the following valves are closed: the main and auxiliary valves at the inlet of the synthesis tower, the ball valve at the inlet of the ammonia separator, the fresh gas valve, the vent valves before and after the tower, as well as all the ammonia transfer valves and ammonia addition valves. The ammonia supply ball valve may be closed only when the system pressure is less than 2.5 MPa; in such cases, the main inlet valve of the ammonia storage tank should also be closed. Otherwise, the aforementioned valves must not be closed completely. (2) Long-term shutdown (production cannot be resumed immediately and the equipment in this system requires maintenance): Ammonia supply to the ammonia cooler should be stopped 4 hours before the shutdown. The high-pressure compressor gradually reduces its load, while controlling the flow rate to facilitate cooling, with the cooling rate being strictly kept within the specified limits. After the high-pressure compressor stops supplying gas, the circulation pump continues to assist with cooling, while pushing the liquid ammonia from the ammonia separator and condenser tower into the ammonia storage tank. When the temperature is reduced to 100°C, the circulation pump can be shut off, water supply to the water cooler is stopped, and the pressure is released through the vent valve at the back of the tower. If the synthesis tower itself is disassembled for inspection, catalyst passivation or pressurization with gaseous ammonia is required. (3) Emergency stop: Command the high-pressure compressor to cease gas supply and shut down the circulation pump. The following valves must be closed promptly in sequence: the line connected to the synthesis tower, the main valve, the ball valve at the inlet of the ammonia separator, all ammonia addition valves and ammonia release valves, the system bypass valve, and the fresh gas valve. Carry out the necessary post-parking procedures, including pushing the condenser tower, ammonia fractions, and liquid ammonia into the ammonia storage facility. 3. Operational precautions: (1) The synthesis tower unit is one of the most important units in production; it is essential to maintain proper control over the temperature of the synthesis tower to prevent drops in temperature as well as overheating. (2) Pay attention to the ammonia level and the liquid level in the condenser tower to prevent damage to the circulation pump due to ammonia presence or a drop in temperature in the synthesis tower. (3) To ensure the safety of the electric furnace during heating, its circulation rate must be adjusted according to the furnace’s power level. It is strictly prohibited to use a high circulation rate when heating a furnace with high power. If the circulation stops (for example, if the circulation pump fails completely), the furnace must be shut down immediately to prevent damage to the furnace components. (4) Communication has been established with the ammonia storage facility; when the system pressure is greater than 2.5 Mpa, the ammonia transfer ball valve and the main ammonia inlet cannot be in a closed state. (5) Coordinate well with 8.13; be absolutely clear about the operating status of the “69” connection valve. (6) Control the ammonia transfer pressure carefully to prevent high pressure from leaking into the low-pressure system. (VII) Accident Handling Sequence Number Phenomenon Cause Handling Method Remarks 1 Drop in catalyst bed temperature 1. Excessive circulation rate 2. Too high ammonia content in the material entering the synthesis tower: A. Insufficient amount of ammonia added to the ammonia cooler. B. Excessively high pressure in the main ammonia pipeline. C. Excessive oil and water in the ammonia cooler. D. Low cooling efficiency of the water cooler. E. High level of the secondary cooling fluid. 3. Too high hydrogen-to-nitrogen ratio. 4. Too high content of inert gas. 5. The main valve of the tower is opened too little or the auxiliary valves are opened too much. 1. Open a bypass in the system or reduce the circulation volume using the auxiliary valves of the circulator. 2. Reduce the amount of ammonia entering the system. A. Increase the ammonia addition valve. B. Add more ice makers. C. Remove oil and water. D. Increase the amount of cooling water used appropriately. E. Lower the liquid level. 3. Reflect the temperature. 4. Release the inert gas or send hydrogen for recovery. 5. Gradually increase the opening of the main valve while reducing the opening of the auxiliary valves. The valve opening degree should not be too large, and the operating intervals should be 3–5 minutes. 2. The temperature of the catalyst layer rises due to: 1. Insufficient circulation volume of gas; 2. The main valve of the synthesis tower being opened too wide or the auxiliary valves being opened too narrow. 3. Increase in fresh air volume. 1. Reduce the valve on the system’s bypass or circulation pump. 2. Reduce the main valve or increase the auxiliary valve. 3. Adjust according to the dosage; if it is already at full load, reduce the amount appropriately. 3. Drop in pressure in the synthesis tower: 1. Insufficient air volume from the compressor; 2. Leaks in the system; 3. Excessive exhaust gas; 4. Low liquid level causing gas leakage. 1. Contact the compressor for inspection; 2. Shut down the system for repairs if the issue is severe; 3. Control the amount of exhaust gas; 4. Maintain an appropriate liquid level. 4. Rise in pressure in the synthesis tower: 1. Decreased catalyst temperature; 2. Too low circulation volume of gas; 3. High ammonia content in the gas entering the tower; 4. High load; 5. Imbalanced hydrogen-to-nitrogen ratio; 6. High level of inert gases. 1. Contact the compressor for inspection; 2. Shut down the system for repairs if the issue is severe; 3. Control the amount of exhaust gas; 4. Maintain an appropriate liquid level. 5. Excessive system resistance: 1. Inaccurate pressure gauges; 2. Blocked pipes or valves that are not in proper position; 3. Excessive circulation volume; 4. High nitrogen content. 1. Reduce the circulation volume and create alternative routes for the gas flow; 2. Increase the circulation volume of gas; 3. Reduce the ammonia content in the gas; 4. Reduce the load if levels exceed specifications; 5. Notify the dispatch team; 6. Send the gas to hydrogen recovery or discharge it. 6. High wall temperature in the synthesis tower: 1. Too low circulation volume and valves being opened too wide; 2. Damage to the internal components of the tower. 1. Increase the circulation volume; 2. Shut down the system for repairs if necessary. 7. Too high exit temperature from the synthesis tower: 1. Too low circulation volume; 2. Main valves of the tower being opened too little while auxiliary valves are opened too wide; 3. Low level of inert gases; 4. High load. 1. Increase the circulation volume; 2. Open the main valves slightly more and close the auxiliary valves; 3. Reduce or stop gas leakage, as well as emissions, and send the gas to hydrogen recovery; 4. Reduce the load as appropriate. 8. Decrease in catalyst layer temperature with a sudden rise in tower pressure: 1. High levels of CO+CO2, causing catalyst poisoning; 2. Copper solution or ammonia entering the tower, causing catalyst poisoning; 3. High level of secondary cooling liquid, allowing liquid and gas to enter the tower. 1. Reduce the output of the compressor as specified; control the circulation volume to maintain temperature. If pressure rises too high, discharge gas from behind the tower. If CO+CO2 levels reach 100 PPm, shut down the tower for repairs. 2. Emergency shutdown of the tower. 3. Control the liquid level properly. 9 Water supply interruption: 1. Soft water supply interrupted in the intermediate tank; 2. Water supply interrupted to the water cooler. 1. The control cycle for the secondary inlet temperature of the sight tower is to either reduce the load or shut down the tower. 2. Lower the temperature of the ammonia cooler; if the inlet temperature of the circulation pump does not remain within the specified limits, shut down the tower urgently if the water supply interruption lasts for a long time. 10 Power outage: Interruption of power supply or malfunction of electrical equipment – Treat as an emergency stop. 11 Circulation pump shuts down or emergency stop occurs: 1. Fault in the power distribution station or interlock mechanism; 2. Pump failure leading to emergency stop. 1. Reduce flow rate as appropriate; 2. Shut down the tower completely in case of an emergency. 12 Explosion or fire, severe gas leakage, or other similar situations – Shut down the tower immediately. 13 Supply of fresh gas is interrupted: 1. Gas supply system fault; 2. Failure of the high-pressure compressor; 3. Faults in the purification or copper washing systems – Shut down the tower. 14 Sudden increase in system pressure: 1. Damaged, detached, or loosely connected valves within the system; 2. Valves installed in the wrong direction, airflow blockage, or other reasons. 1. Reduce the circulation volume, maintain temperature, keep the system pressure within specified limits, and reduce the high-pressure compressor’s output accordingly; 2. Identify the cause of the problem. 15 All or some instruments fail: Interruption or malfunction of instruments – Maintain the current operating conditions, contact the instrument maintenance team, or shut down the tower. VIII. Communication during operation: 1. Maintain close communication with the circulation pump operator to adjust the circulation volume. 2. The amount of addition and subtraction is closely related to the high-pressure machine operator’s role. 3. It is closely related to copper washing based on temperature changes. 4. Controlling ammonia feeding and ammonia addition pressure is closely linked to the ammonia storage tank. 5. In case of an emergency when the foreman and the on-duty shift supervisor are not present, it is possible to contact the control room directly for prompt handling, with a follow-up report to be submitted afterwards. II. Equipment Maintenance System (I) Scope of Management 1. The synthesis tower, as well as its connected pipelines, fittings, valves, etc. 2. 1# and 2# condensation towers and their connecting fittings, etc. 3. Water condensation towers 1#, 2#, 3# and their connecting fittings, etc. 4. New and original ammonia coolers, gaseous ammonia demisters, as well as their connecting fittings, valves, etc. 5. Ammonia separator and its connecting fittings, valves, etc. 6. The external heat exchanger, as well as its connecting fittings, valves, etc. 7. Centralized boiler and its connecting fittings, valves, etc. 8. Ammonia transfer and addition pipelines, etc. (II) Equipment maintenance 1. Strictly implement the post responsibility system and technical operating procedures to prevent operation under conditions of excessive temperature, pressure, or load. 2. The pressure and temperature in the synthesis tower should be adjusted at strictly specified rates; load changes must be made gradually to avoid sharp fluctuations. During normal operation, it is necessary to maintain stability in the temperature of the catalyst layer, with fluctuations not exceeding acceptable limits. 3. After the catalyst is installed in the synthesis tower, backflow of gas inside the tower is strictly prohibited; therefore, care must be taken when opening the inlet and outlet valves of the synthesis tower. (1) When the pressure inside the tower is high, open the outlet valve first; when the pressure outside the tower is high, open the inlet valve first. (2) If the main valve and auxiliary valves of the tower are not fully closed, venting before starting the tower is not possible. 4. When using an electric furnace, it is necessary to first turn on the circulation machine to supply air; only once the air supply volume from the circulation machine reaches a certain level can the electric furnace be turned on. The operation of electric furnaces should be carried out in accordance with the regulations for their use. 5. When shutting down the synthesis tower, it is necessary to maintain a positive pressure inside the tower to prevent air from entering and damaging or burning the catalyst. 6. In the event of a shutdown caused by copper-containing liquid entering the tower or minor poisoning, the method of pressurizing and raising temperature shall not be used. 7. No random striking of any equipment, pipes, instruments, etc. is allowed. It is necessary to regularly check the vibration of high-pressure pipelines, as well as for any leaks or ruptures in various equipment and valves, to report such issues promptly and address them right away. 8. Eliminate running, leaking, dripping, and seeping wherever possible. 9. Conduct thorough inspections as required and install signs. 10. Carry out cleaning as required. 11. Control the liquid level properly to prevent high levels from flowing into lower levels, as well as accidents involving liquid entering the tower or cylinders. This post was last edited by Huang Xinhui on 2009-3-17 18:26]
(IV) Specifications of main equipment
| Serial No. | Name | Specifications | Remarks |
|-------------|------|---------------|---------|
| 1 | Synthesis tower | Outer diameter: Φ1000 mm; effective height: 13800 mm. Diameter of catalyst basket: Φ934×16. Upper catalyst height: 5582 mm; lower height: 578 mm. Number of cooling tubes: 62 each of Φ44×2.5, Φ29×2.5, and Φ22×1. Heat exchange area: E = 40 m². Heat exchange height: 236 mm. Number of tubes of Φ10×1.5: 3084; heat exchange area: 224 m². Power of pressure regulator: 650 V, 710 A, 800 KVA. Catalyst loading capacity: 15 t, 3 m³. |
| 2 | Condenser | Outer diameter: Φ900 mm; height: 8210 mm. Double-layer shell-and-tube heat exchanger with a heat exchange area of F = 165 m². 1st condenser; 2nd one is used only for separation. |
| 3 | Ammonia cooler | 628 tubes of Φ25×4; shell-and-tube type with a heat exchange area of F = 226 m². 2 units available. |
| 4 | Ammonia separator | Outer diameter: Φ1000 mm; height: H = 4625 mm. 1 unit. |
| 5 | Water cooler | Horizontal shell-and-tube heat exchanger with a heat exchange area of F = 199 m². 3 units. |
(V) Operating procedures
1. Normal startup
(1) Preparation work: Check whether the system equipment, pipes, and valve connections are secure, whether the blind plates have been installed correctly, and whether water, electricity, and gas supply are functioning properly. Contact the electrician and instrument technician to check whether the electrical equipment and instruments are in good condition and ready for use. Check the protective measures, ensure that the fire-fighting equipment is complete and functional, and that the lighting is suitable for driving. (2) Exhaust replacement: Check the valves: the large valve at the filter outlet, the inlet and outlet valves of the first-stage water cooler of the compressor (for two or more valves), the valve for ammonia production, the large valve on the main pipeline, and the fresh gas vent valve. Valves to be closed: fresh gas ball valve, fresh gas main valve, system bypass valve, main and auxiliary valves at the inlet of the synthesis tower, ball valve at the inlet of the ammonia separator, inlet and outlet main valves of #1, #2, and #3 circulators, vent valves before and after the tower, as well as all ammonia transfer valves and ammonia addition valves. Contact the high-pressure compressor and send air to Section 6 at 8.13; first exhaust the air from the fresh gas main, then close the fresh gas vent valve completely. Open the fresh gas valve, the fresh gas main valve, and the vent valve at the front of the tower to exhaust gas from there; ensure that the O2 concentration is ≤0.2%, which meets the requirements, and then close the vent valve at the front of the tower. Open the main valve at the inlet of the synthesis tower, the ball valve at the inlet of the ammonia separator, and the vent valve at the back of the tower to vent air from behind the tower; the pressure during venting shall not exceed 2.0 Mpa, and the venting time shall be 5 minutes. During pressurized exhaust, when the pressure exceeds 2.1 Mpa, open the ammonia transfer ball valve and inform the ammonia storage facility to open the main ammonia inlet. Check for any gaps at the same time. (3) Leak testing: After the exhaust replacement is successful, close all vent valves and use fresh gas to conduct a leak test across the entire system. Leak testing is carried out at pressures of 10, 20, 25, and 31.5 Mpa, with the pressure being increased by 4 Mpa per minute. If a leak is detected, the pressure must be reduced to below 5 Mpa before the maintenance workshop’s fitter can tighten the bolts; thereafter, leak testing is repeated until the system is leak-free. After the leak test is successful, the rear vent valve on the same tower is used to reduce the system pressure to 6–8 Mpa, in preparation for using the circulation pump and electric furnace to raise the temperature. (4) Increase the temperature to bring the valves to the following states: Valves that should be closed include the valve at the inlet of the synthesis tower, the main valve for fresh gas and the ball valve, all ammonia transfer stop valves, the ammonia addition valve, all vent valves as well as the oil and water release valves, and the ball valve of the circulator. Valves to be opened: main valve at the inlet of the synthesis tower, system bypass valve, ball valve at the ammonia inlet, inlet and outlet valves of the circulator, and auxiliary valve of the circulator. Open the inlet and outlet ball valves of the circulation pump, connect it to the system, and use the bypass valve of the circulation pump as well as the system’s bypass valve to check the circulation rate. The electrician turns on the electric furnace; the first voltage increase should be less than 50V, and subsequent increases must not exceed 20V each time. During the operation of the electric furnace, pay attention to issues such as grounding and short circuits. Stay in touch with the electrical personnel at any time. If any abnormality is detected in the electric furnace, the voltage should be stopped immediately, or the voltage reduced until the furnace is shut down. It is absolutely necessary to ensure that the electric furnace has sufficient supply of air to prevent the heating filaments from overheating and getting damaged. When the circulation machine trips, immediately cut off the power to the electric furnace. Strictly control the heating rate within the specified range. The temperature difference across the catalyst plane must not exceed 10°C. For the temperature rise of the electric furnace, in principle, an operation method with a high furnace power and large circulation volume should be used to ensure an adequate amount of safety air flow. Water is added to the water cooler when the hot spot temperature reaches 100°C, and ammonia is added to the ammonia cooler when the hot spot temperature reaches 350°C. At the same time, it is important to ensure that the liquid ammonia level in the ammonia cooler does not exceed the specified limits. After the temperature rises to 400°C, a compressor can be used to supply air, or the valve labeled “69” connected to 8.13 can be slowly opened until pressure is balanced, after which it can be fully opened to start production. During the valve opening process, the catalyst temperature rose sharply above the specified limit, so the circulation rate was used for control. While pressurizing, start reducing the load on the electric furnace; after the reduction is complete, and once the catalyst and temperature are both back to normal and normal production has resumed, then shut down the electric furnace. (5) Pressurization and temperature rise procedure: In the case of a short-term shutdown with a hotspot temperature above 380°C, depending on the catalyst’s activity, fresh gas can be used for pressurization, utilizing the heat of reaction to raise the catalyst temperature to normal levels. (If the tower is stopped due to mild poisoning, pressurization and temperature increase are prohibited.) The valves in the system are in the following states: Valves that should be open: the ball valve at the fresh gas inlet, the main valve on the ammonia pipeline, and the ammonia transfer valve (this ball valve should be opened when the system pressure reaches 2.0 Mpa; meanwhile, the ammonia storage facility should be informed to open the main inlet valve for ammonia transfer). The inlet and outlet valves of the water coolers for the first stage of the high-pressure compressor (for two or more compressors), as well as the inlet and outlet ball valves of the circulation pump. Valves to be closed: main fresh gas valve, main and auxiliary valves of the synthesis tower, system bypass valves, fresh gas vent valve, inlet and outlet valves of the circulator, ball valve at the inlet of the ammonia separator, vent valves before and after the tower, as well as all ammonia transfer valves and ammonia addition valves. Fill the water cooler with water, and fill the ammonia cooler with ammonia. Open the fresh gas main valve to pressurize the area in front of the tower; once the pressure there is higher than that inside the tower, slightly open the main valve on the tower’s control panel and gradually increase the pressure inside the tower. Prepare the circulation pump and start it to bring the pressure up to match the pressure inside the tower; keep the bypass valve fully open, and keep the inlet and outlet ball valves fully closed. When the rise in temperature stalls, slightly open the ball valve at the inlet of the ammonia separator; depending on the operating conditions, slightly open the vent valve at the back of the tower as well to release some gas, thereby allowing the temperature inside the tower to continue rising steadily. When the catalyst hotspot temperature approaches the target value, the circulator can be introduced into the system, and the load can be increased gradually; subsequently, the circulation rate can be increased step by step based on the catalyst temperature, allowing normal production to resume. Control the ammonia transfer pressure properly. 2. Shutdown (1) Short-term shutdown (planning to resume production in the near future). Before shutting down, raise the catalyst temperature to the upper limit specified; inform the high-pressure compressor to gradually reduce its load, and at the same time close the auxiliary valves. Reduce the circulation rate to the minimum possible, while striving to keep the catalyst temperature from dropping, and pay attention to the ammonia level and the level of the secondary cooling liquid. After the supply of fresh gas has been completely stopped, the circulation machine is disconnected from the system, and the following valves are closed: the main and auxiliary valves at the inlet of the synthesis tower, the ball valve at the inlet of the ammonia separator, the fresh gas valve, the vent valves before and after the tower, as well as all the ammonia transfer valves and ammonia addition valves. The ammonia supply ball valve may be closed only when the system pressure is less than 2.5 MPa; in such cases, the main inlet valve of the ammonia storage tank should also be closed. Otherwise, the aforementioned valves must not be closed completely. (2) Long-term shutdown (production cannot be resumed immediately and the equipment in this system requires maintenance): Ammonia supply to the ammonia cooler should be stopped 4 hours before the shutdown. The high-pressure compressor gradually reduces its load, while controlling the flow rate to facilitate cooling, with the cooling rate being strictly kept within the specified limits. After the high-pressure compressor stops supplying gas, the circulation pump continues to assist with cooling, while pushing the liquid ammonia from the ammonia separator and condenser tower into the ammonia storage tank. When the temperature is reduced to 100°C, the circulation pump can be shut off, water supply to the water cooler is stopped, and the pressure is released through the vent valve at the back of the tower. If the synthesis tower itself is disassembled for inspection, catalyst passivation or pressurization with gaseous ammonia is required. (3) Emergency stop: Command the high-pressure compressor to cease gas supply and shut down the circulation pump. The following valves must be closed promptly in sequence: the line connected to the synthesis tower, the main valve, the ball valve at the inlet of the ammonia separator, all ammonia addition valves and ammonia release valves, the system bypass valve, and the fresh gas valve. Carry out the necessary post-parking procedures, including pushing the condenser tower, ammonia fractions, and liquid ammonia into the ammonia storage facility. 3. Operational precautions: (1) The synthesis tower unit is one of the most important units in production; it is essential to maintain proper control over the temperature of the synthesis tower to prevent drops in temperature as well as overheating. (2) Pay attention to the ammonia level and the liquid level in the condenser tower to prevent damage to the circulation pump due to ammonia presence or a drop in temperature in the synthesis tower. (3) To ensure the safety of the electric furnace during heating, its circulation rate must be adjusted according to the furnace’s power level. It is strictly prohibited to use a high circulation rate when heating a furnace with high power. If the circulation stops (for example, if the circulation pump fails completely), the furnace must be shut down immediately to prevent damage to the furnace components. (4) Communication has been established with the ammonia storage facility; when the system pressure is greater than 2.5 Mpa, the ammonia transfer ball valve and the main ammonia inlet cannot be in a closed state. (5) Coordinate well with 8.13; be absolutely clear about the operating status of the “69” connection valve. (6) Control the ammonia transfer pressure carefully to prevent high pressure from leaking into the low-pressure system. (VII) Accident Handling Sequence Number Phenomenon Cause Handling Method Remarks 1 Drop in catalyst bed temperature 1. Excessive circulation rate 2. Too high ammonia content in the material entering the synthesis tower: A. Insufficient amount of ammonia added to the ammonia cooler. B. Excessively high pressure in the main ammonia pipeline. C. Excessive oil and water in the ammonia cooler. D. Low cooling efficiency of the water cooler. E. High level of the secondary cooling fluid. 3. Too high hydrogen-to-nitrogen ratio. 4. Too high content of inert gas. 5. The main valve of the tower is opened too little or the auxiliary valves are opened too much. 1. Open a bypass in the system or reduce the circulation volume using the auxiliary valves of the circulator. 2. Reduce the amount of ammonia entering the system. A. Increase the ammonia addition valve. B. Add more ice makers. C. Remove oil and water. D. Increase the amount of cooling water used appropriately. E. Lower the liquid level. 3. Reflect the temperature. 4. Release the inert gas or send hydrogen for recovery. 5. Gradually increase the opening of the main valve while reducing the opening of the auxiliary valves. The valve opening degree should not be too large, and the operating intervals should be 3–5 minutes. 2. The temperature of the catalyst layer rises due to: 1. Insufficient circulation volume of gas; 2. The main valve of the synthesis tower being opened too wide or the auxiliary valves being opened too narrow. 3. Increase in fresh air volume. 1. Reduce the valve on the system’s bypass or circulation pump. 2. Reduce the main valve or increase the auxiliary valve. 3. Adjust according to the dosage; if it is already at full load, reduce the amount appropriately. 3. Drop in pressure in the synthesis tower: 1. Insufficient air volume from the compressor; 2. Leaks in the system; 3. Excessive exhaust gas; 4. Low liquid level causing gas leakage. 1. Contact the compressor for inspection; 2. Shut down the system for repairs if the issue is severe; 3. Control the amount of exhaust gas; 4. Maintain an appropriate liquid level. 4. Rise in pressure in the synthesis tower: 1. Decreased catalyst temperature; 2. Too low circulation volume of gas; 3. High ammonia content in the gas entering the tower; 4. High load; 5. Imbalanced hydrogen-to-nitrogen ratio; 6. High level of inert gases. 1. Contact the compressor for inspection; 2. Shut down the system for repairs if the issue is severe; 3. Control the amount of exhaust gas; 4. Maintain an appropriate liquid level. 5. Excessive system resistance: 1. Inaccurate pressure gauges; 2. Blocked pipes or valves that are not in proper position; 3. Excessive circulation volume; 4. High nitrogen content. 1. Reduce the circulation volume and create alternative routes for the gas flow; 2. Increase the circulation volume of gas; 3. Reduce the ammonia content in the gas; 4. Reduce the load if levels exceed specifications; 5. Notify the dispatch team; 6. Send the gas to hydrogen recovery or discharge it. 6. High wall temperature in the synthesis tower: 1. Too low circulation volume and valves being opened too wide; 2. Damage to the internal components of the tower. 1. Increase the circulation volume; 2. Shut down the system for repairs if necessary. 7. Too high exit temperature from the synthesis tower: 1. Too low circulation volume; 2. Main valves of the tower being opened too little while auxiliary valves are opened too wide; 3. Low level of inert gases; 4. High load. 1. Increase the circulation volume; 2. Open the main valves slightly more and close the auxiliary valves; 3. Reduce or stop gas leakage, as well as emissions, and send the gas to hydrogen recovery; 4. Reduce the load as appropriate. 8. Decrease in catalyst layer temperature with a sudden rise in tower pressure: 1. High levels of CO+CO2, causing catalyst poisoning; 2. Copper solution or ammonia entering the tower, causing catalyst poisoning; 3. High level of secondary cooling liquid, allowing liquid and gas to enter the tower. 1. Reduce the output of the compressor as specified; control the circulation volume to maintain temperature. If pressure rises too high, discharge gas from behind the tower. If CO+CO2 levels reach 100 PPm, shut down the tower for repairs. 2. Emergency shutdown of the tower. 3. Control the liquid level properly. 9 Water supply interruption: 1. Soft water supply interrupted in the intermediate tank; 2. Water supply interrupted to the water cooler. 1. The control cycle for the secondary inlet temperature of the sight tower is to either reduce the load or shut down the tower. 2. Lower the temperature of the ammonia cooler; if the inlet temperature of the circulation pump does not remain within the specified limits, shut down the tower urgently if the water supply interruption lasts for a long time. 10 Power outage: Interruption of power supply or malfunction of electrical equipment – Treat as an emergency stop. 11 Circulation pump shuts down or emergency stop occurs: 1. Fault in the power distribution station or interlock mechanism; 2. Pump failure leading to emergency stop. 1. Reduce flow rate as appropriate; 2. Shut down the tower completely in case of an emergency. 12 Explosion or fire, severe gas leakage, or other similar situations – Shut down the tower immediately. 13 Supply of fresh gas is interrupted: 1. Gas supply system fault; 2. Failure of the high-pressure compressor; 3. Faults in the purification or copper washing systems – Shut down the tower. 14 Sudden increase in system pressure: 1. Damaged, detached, or loosely connected valves within the system; 2. Valves installed in the wrong direction, airflow blockage, or other reasons. 1. Reduce the circulation volume, maintain temperature, keep the system pressure within specified limits, and reduce the high-pressure compressor’s output accordingly; 2. Identify the cause of the problem. 15 All or some instruments fail: Interruption or malfunction of instruments – Maintain the current operating conditions, contact the instrument maintenance team, or shut down the tower. VIII. Communication during operation: 1. Maintain close communication with the circulation pump operator to adjust the circulation volume. 2. The amount of addition and subtraction is closely related to the high-pressure machine operator’s role. 3. It is closely related to copper washing based on temperature changes. 4. Controlling ammonia feeding and ammonia addition pressure is closely linked to the ammonia storage tank. 5. In case of an emergency when the foreman and the on-duty shift supervisor are not present, it is possible to contact the control room directly for prompt handling, with a follow-up report to be submitted afterwards. II. Equipment Maintenance System (I) Scope of Management 1. The synthesis tower, as well as its connected pipelines, fittings, valves, etc. 2. 1# and 2# condensation towers and their connecting fittings, etc. 3. Water condensation towers 1#, 2#, 3# and their connecting fittings, etc. 4. New and original ammonia coolers, gaseous ammonia demisters, as well as their connecting fittings, valves, etc. 5. Ammonia separator and its connecting fittings, valves, etc. 6. The external heat exchanger, as well as its connecting fittings, valves, etc. 7. Centralized boiler and its connecting fittings, valves, etc. 8. Ammonia transfer and addition pipelines, etc. (II) Equipment maintenance 1. Strictly implement the post responsibility system and technical operating procedures to prevent operation under conditions of excessive temperature, pressure, or load. 2. The pressure and temperature in the synthesis tower should be adjusted at strictly specified rates; load changes must be made gradually to avoid sharp fluctuations. During normal operation, it is necessary to maintain stability in the temperature of the catalyst layer, with fluctuations not exceeding acceptable limits. 3. After the catalyst is installed in the synthesis tower, backflow of gas inside the tower is strictly prohibited; therefore, care must be taken when opening the inlet and outlet valves of the synthesis tower. (1) When the pressure inside the tower is high, open the outlet valve first; when the pressure outside the tower is high, open the inlet valve first. (2) If the main valve and auxiliary valves of the tower are not fully closed, venting before starting the tower is not possible. 4. When using an electric furnace, it is necessary to first turn on the circulation machine to supply air; only once the air supply volume from the circulation machine reaches a certain level can the electric furnace be turned on. The operation of electric furnaces should be carried out in accordance with the regulations for their use. 5. When shutting down the synthesis tower, it is necessary to maintain a positive pressure inside the tower to prevent air from entering and damaging or burning the catalyst. 6. In the event of a shutdown caused by copper-containing liquid entering the tower or minor poisoning, the method of pressurizing and raising temperature shall not be used. 7. No random striking of any equipment, pipes, instruments, etc. is allowed. It is necessary to regularly check the vibration of high-pressure pipelines, as well as for any leaks or ruptures in various equipment and valves, to report such issues promptly and address them right away. 8. Eliminate running, leaking, dripping, and seeping wherever possible. 9. Conduct thorough inspections as required and install signs. 10. Carry out cleaning as required. 11. Control the liquid level properly to prevent high levels from flowing into lower levels, as well as accidents involving liquid entering the tower or cylinders. This post was last edited by Huang Xinhui on 2009-3-17 18:26]