Weekly Topic 11.01.15 Issue 11: What are the adjustment methods and reasons for various processes in case of an emergency during methanol production?
Thread Content
Let’s discuss the adjustment methods and reasons for various processes in the event of an emergency in methanol production For example, in the case of a shutdown of the synthesis compressor: 1. If it is a short-term process interlock shutdown, the synthesis system maintains its temperature, the water circulation continues, the purification unit operates at reduced capacity, and the load level of the distillation unit is determined by the amount of crude methanol in the storage tank; the synthesis compressor should be restarted as soon as possible. 2. If the long-term shutdown is caused by equipment issues, it involves pressure holding during the replacement of the synthesis tower, shutdown of the synthesis process, shutdown of the purification process, and shutdown of the distillation process.
Emergency response plan for sudden cessation of circulating water supply: When the supply of circulating water is suddenly interrupted, all water coolers will lose their cooling function. The synthesis machine and the circulation pump will shut down automatically due to low water pressure, and overpressure will occur at the top of the distillation tower. Emergency response: a. The shift leader shall immediately report to the control room and the relevant supervisors at the branch plant or the on-duty supervisors, in order to coordinate and direct all teams in handling the accident. b. Compression unit: Quickly go to the site and close the outlet valve of the synthesizer in sequence, slightly open the vent valve, and close the primary inlet valve to prevent the primary safety valve from activating or the inlet pipeline from overpressuring; close the vent valve when the pressure in the synthesizer drops to 0.5 Mpa. c. In the synthesis unit, monitor the pressure in the drum promptly, control the temperature of the catalyst bed in the synthesis tower, release pressure to 0.35 Mpa via the flare, and purge with nitrogen until it reaches the specified standard. After the inlet valve of the synthesizer is closed, close the bleed valve. d. In the distillation section, close the manual valves at the inlets of the reboilers in both towers, close the outlet valves of each pump, and intermittently pump methanol from the reflux tank back into the towers. e. Tank area station: Close the refined methanol receiving valve, divert the refined methanol to the crude tank receiving location, and close the outlet valves of all pumps.
Emergency response plan for sudden cessation of nitrogen supply: When the nitrogen supply is suddenly interrupted, the electric heater loses its protection against nitrogen, as does the compressor’s sealing mechanism; in such an emergency situation, there is no protection against nitrogen. Emergency measures: If the supply of nitrogen is suddenly interrupted, apart from the inability to use electric heaters, it will not affect the normal operation of various production units. Therefore, when the nitrogen supply is halted, inspections should be intensified, the use of electric heaters should be stopped, and the area where welding or maintenance work is being carried out should be purged with nitrogen as a form of protection, with operations in that area being suspended. In areas where nitrogen is used to maintain pressure while vehicles are parked, such as the desulfurization section, compression section, and synthesis section, an appropriate amount of gas can be introduced into the system to prevent a drop in pressure that could result in a vacuum and the entry of air, which could pose a danger. In the distillation section, steam can be added to the system to maintain pressure. If the nitrogen supply cannot be restored for an extended period, the plant can be shut down under the unified arrangement of the scheduling department. Nitrogen can be used only after it has been analyzed and found to be of satisfactory quality following the resumption of supply.
Handling of the incident involving the interruption of water supply to the boiler in the synthesis tower: Hazards: There is a risk of the synthesis tower running dry. Actions to take: 1. Contact the dispatch team to determine how long the water supply will be interrupted. 2. The compressor operator should immediately stop the supply of fresh gas and increase the amount of circulating gas. 3. The synthesis team must maintain pressure in the boiler; once the CO+CO2 content in the gas within the synthesis system is below 0.2%, the gas phase from the separator should be vented to the flare. Once the system pressure drops to 0.3 MPa, nitrogen should be introduced to purge the synthesis system. 4. After the water supply is restored, first check whether the liquid level in the boiler is sufficient; if there is enough liquid, proceed with normal operation. If the boiler is dry, follow the emergency procedures by lowering the tower temperature before gradually adding water again.
Poster: For some reason, all the units in the gas chemical section suddenly stopped operating. What should be done after the supply of methanol is interrupted? The purification section operates in a separate circulation mode; synthesis is stopped, the cold box is shut down, and propylene production is halted. Distillation continues to draw crude methanol from the crude methanol tank, and if there isn’t enough methanol in that tank, operation must be stopped. I wonder if the above steps are reasonable? Please let the original poster know, thank you
Reply to 5# Huayi Person: After vaporization parking, does your factory have boilers? If distillation isn’t carried out, the plant has to be shut down – there isn’t enough steam available. Depending on the duration of the shutdown due to vaporization, it’s necessary to check whether the methanol washing cycle is still functioning; in the absence of steam, the methanol-rich liquid can easily get contaminated. Continuous cycling can easily carry away the cold energy.
Reply to 6# Shouhou: Hello, the factory has boilers; during normal production, steam generated by the synthetic drum is primarily used
Accident of low steam output due to boiler trip: 1. Contact the dispatch team, identify the cause, and determine how long it will take to restart the boiler. 2. For the distillation system to reduce its load, it is necessary to determine based on actual conditions whether to completely stop steam supply and transfer crude methanol to the tank area. 3. Increase the steam production of each waste heat boiler, while reducing the areas where steam is not needed. 4. Reduce the flow of steam drains at the site.
Treatment methods for the conversion unit when the syngas compressor fails in methanol production from coke oven gas: 1. The conversion unit must detect the failure as soon as possible, because the pressure rise due to the failure of the syngas compressor is extremely rapid; delays could lead to an explosion! Quickly open the vent; while doing so, pay attention to the pressure in the drum. 2. Instruct the coke oven gas compressor to reduce its output, lowering it to the lowest level permitted for operation, so that gas can be supplied once the synthesis compressor starts up. When reducing the load, pay attention to the temperature at the furnace outlet and regulate the boiler feedwater pressure.
Treatment for methanol production using coke oven gas (when the coke oven gas compressor fails and cannot be restarted immediately): 1. Cut off oxygen supply. 2. Inform the synthesis unit and disconnect it from the system. 3. Maintain the insulation and pressure in the precision desulfurization system of the conversion section. 4. Due to the lack of coke oven gas, pay attention to the temperature at the outlet of the preheater and reduce the amount of fuel gas used accordingly. 5. Steam is supplied to the converter for cooling based on the drum pressure. If there is not enough steam, notify the boiler room to supply additional steam to cool the converter. 6. In short, it’s all about handling parking