Measures to Prevent Fire and Explosion Accidents of Reactor Vessels

1) Production in strict accordance with safety regulations

The process specification of the reaction vessel needs to be approved by special scientific research and design units. Without the corresponding appraisal of these departments, it is not allowed to change the production process. Production operators must be familiar with the production process regulations, operating conditions, reaction exothermicity and fire and explosion hazard properties of raw materials, products and intermediate products, and prevent operational errors.

2) Maintain the compressive strength of the container

As a pressure-bearing equipment, the reaction vessel should be carried out in strict accordance with the design and manufacturing process of the pressure vessel to eliminate quality defects such as welding. During the use of the container, the wall of the container should be prevented from thinning due to corrosion and other reasons, and the compressive strength is reduced. Therefore, the container should be regularly inspected, maintained, and pressure tested to ensure the pressure resistance of the container.

3) Prevent uncontrolled reactions from occurring

Strictly monitor and control the temperature, pressure, material composition and feeding sequence in the reaction vessel according to regulations, so as to keep the reaction normal. The measures to prevent runaway of the tubular fixed-bed oxidation reactor include: adding a trace inhibitor to the feed gas to partially poison the catalyst; placing some catalysts diluted by an inert carrier or part of the catalyst in the upper layer of the reaction tube near the inlet of the feed gas. Aging catalyst; adopt stage cooling method to improve heat transfer rate. The cooling pipe set in the fluidized bed reactor should have enough cooling area to ensure continuous supply of coolant with stable parameters, and at the same time, the reaction temperature can be finely adjusted by the preheating temperature of the raw material gas. The control of the nitrification reaction speed should pay attention to the following aspects: control the feeding speed well, use double valves to control the feeding of nitrification agent, and prohibit the bulk input of solid materials; red-brown nitrogen oxide gas appears during the nitrification process, which may be caused by temperature rise. If there are signs of danger, the feeding should be stopped immediately; the nitrification reactor should be equipped with a cooling water source backup system; the materials should be mixed evenly, and the reactor should have a backup power supply for automatic start, and auxiliary facilities for protective gas stirring or manual stirring.

The polymerization reaction has the possibility of violent polymerization in the initial stage or during the process. During the reaction, the material should be fed accurately according to the feeding sequence and feeding ratio, and the total material should not be excessive. In the early stage of the reaction, it is necessary to prevent the heating from being too fast. When the reaction is accelerated, the heat release gradually increases, and it is necessary to cool down in time; in the reaction process, pay attention to the temperature and pressure changes. More jacket and tongue cooling area is not enough and is not the best way. At present, in the process, the monomer or solvent is vaporized and refluxed to bring out the reaction heat, and after condensation or compression liquefaction, it is returned to the polymerization kettle to absorb the heat. When the temperature rises greatly, or other dangerous situations occur, a polymerization inhibitor can be added to reduce the activity of the initiator. At the same time, there should be a strict quality inspection system for raw materials, intermediate products and finished products to ensure their purity and content, and to remove harmful impurities.

4) Inhibit the explosion hazard of the material mixture

For the reaction within the explosion limit, the mixer of air or oxygen and the reaction raw materials should be placed near the inlet of the reactor to ensure that the raw material gas enters the reactor immediately after mixing, and reduces the space where explosion may occur. The feed gas and oxygen or air can also be fed separately to avoid the formation of explosive mixtures. For the reaction carried out under the conditions close to the explosion limit, the mixing ratio of raw gas and air or oxygen should be strictly controlled. The production device must have automatic control instruments, component analyzers and safety interlock alarm devices. For example, in the reaction system of ethylene oxidation, the oxygen content is controlled at about 8%, and the ethylene content is controlled at about 65%. If the oxygen content reaches 9% or the ethylene content drops to 60%, it needs to be stopped immediately. Usually three magnetic oxygen analyzers are used to analyze the oxygen content. If two indicators reach this limit, it will alarm and stop immediately: two infrared analyzers are used to analyze the ethylene content, and if one indicator reaches this limit, it will alarm and stop. For reaction vessels with flammable gas or flammable liquid vapor, it must be replaced with an inert gas before feeding. After the reaction is completed, it is also necessary to replace the tender gas or vapor in the container with an inert gas before air can be put in, and the replacement must be thorough.

5) Clean up the coking in the equipment pipeline in time

It is necessary to regularly remove the dirt, coke, and polymer in the equipment to ensure good heat transfer of the equipment and prevent it from clogging the equipment pipes and self-tendering. The cleaning method can be used to flush the wall surface and pipes with water, and use nitrogen or water vapor to purge. Please do not use iron tools or metal strips. The cleaned dirt must be sent to a safe place for disposal.

6) Prevent water from leaking into the reaction vessel

The water level and water pressure of the jacket of the reaction vessel and the coil cooling system should be slightly lower than the liquid level and hydraulic pressure in the vessel. In order to find cracks or holes in the reaction vessel in time, an automatic conductivity oath device can be installed in the drain pipe. When very little material leaks into the pipe, the conductivity of the water will change. Use this change to detect and sound an alarm. .

7) Ensure the safety of materials entering and leaving the reaction vessel

In order to prevent the incoming and outgoing materials from burning and exploding due to static sparks, the reaction vessel, pipes and utensils should be connected by conductors and then grounded. The transportation of liquid materials should also limit the generation of static electricity by controlling the flow rate. When discharging from the reaction vessel, vacuum discharge should be used. When the loading and unloading port is opened, airtight measures should be adopted as far as possible. If this is not possible, a mobile exhaust hood should be installed for ventilation.

The reaction vessel should be equipped with an automatic interlocking system for accident prevention, such as interlocking device for material temperature and catalyst addition amount: pressure or temperature limit adjustment alarm device. When the parameter exceeds the safety regulation range, it can automatically adjust immediately. If the adjustment is ineffective, an alarm signal will be issued, and the operator will be notified to take emergency measures to eliminate the fault. If the troubleshooting is improper or not timely, the automatic control system can issue commands such as switching, venting, and fire extinguishing. Those with greater risk can also use double and triple protection. In order to ensure that the pressure in the reaction vessel can be automatically released when the pressure rises, a safety valve must be installed on the equipment. For equipment that is not suitable for installation of safety valve or is more dangerous, bursting disc can be installed. A one-way valve should be set at the connection between the low-pressure system and the high-pressure reactor to prevent the material in the high-pressure reactor from breaking into the J's jade system and causing an explosion. The reaction vessel should be equipped with an accident discharge tank, or a spare container and a vent pipe for discharging the reaction material. In the event of an emergency when the equipment is out of control, the liquid material in the vessel can be discharged into the accident discharge tank in time; the gaseous material passes through the vent pipe. Drain the container to prevent the accident from expanding. Fire-stopping equipment such as liquid seal or sand seal should be installed on the pipeline before entering the reaction vessel to prevent the spread and expansion of combustion and explosion. Reaction production posts should be equipped with nitrogen and water vapor semi-fixed fire extinguishing devices.

8) Pay attention to the safe discharge of the reaction vessel

The venting pipe of the reaction vessel should generally be installed at the top, and the venting pipe installed in the indoor container should be led out of the room. The venting pipe should be high enough, more than 2m above the highest equipment operated by nearby people, and ensure that the concentration of exhausted combustible gas is within a safe range. After discharge, combustible gas that may burn immediately should be cooled by cooling device and then connected to venting facility. A flame arrester or other flame limiting device should be installed on the vent pipe to prevent the gas from catching fire at the outlet of the pipe and allowing the flame to spread to the process unit. The vent pipe should be well grounded, and the nozzle should be within the scope of lightning protection. The accident storage tank should be set up in a safe area, and the reaction vessel in the factory building, the liquid in it should be discharged to the underground or semi-underground special accident storage tank or discharge tank outside the factory building. The discharge method can use nitrogen, water vapor, carbon dioxide and other inert gases to press release, which can speed up the discharge speed and eliminate the possibility of explosion in the equipment. The accident storage tank should have a large capacity.

9) Master the methods of handling accidents

Take fire knowledge publicity and education as an important part of job training. Special attention should be paid to the training of production operators to deal with emergency situations in production, and to master emergency measures, fire fighting and evacuation methods in case of accidents. Based on the lessons learned from past accidents, operational experience and theoretical reaction heat release characteristics, the possible causes of the accident are put forward, so that accurate judgments can be made and corrective measures can be taken in the event of an accident.