Description, risk factors and preventive measures of ethylbenzene and styrene devices
1. device development
waterproof, moisture-proof and corrosion-proof obligations since Dow Chemical Company of the United States and BASF company of Germany simultaneously realized the industrial production of ethylbenzene dehydrogenation to styrene in 1937, styrene has a history of industrial production for more than 50 years
styrene is an important organic chemical raw material. As an important synthetic monomer, it can copolymerize with other olefin monomers to produce styrene butadiene rubber, polystyrene resin, ABS and San resin, ion exchange resin and unsaturated polyester resin; In addition, it is also used in the pharmaceutical and dye industries, or in the preparation of pesticide emulsifiers and beneficiation agents
the main production methods of styrene are ethylbenzene dehydrogenation and propylene oxide CO oxidation. The former accounts for about 90% of the production capacity of styrene. The processes of ethylbenzene catalytic dehydrogenation to styrene include Monsanto/rums method, BASF method, fina/badger method, CDF method and Mitsubishi oiling/cycloglobular chemical method. The CO oxidation method has many steps, long process, and the co production of propylene oxide. Therefore, the production and research at home and abroad focus on ethylbenzene dehydrogenation
in recent years, many companies have studied the method of replacing benzene with toluene to produce styrene, such as the direct synthesis of styrene from toluene methanol and toluene methane by Monsanto and Mitsubishi Petrochemical Company, which is a new process route. In the special report of the 10th International catalyst conference in 1992, the development and research of this process was listed as one of the four major contemporary alkylation technologies, which deserves the attention of styrene technology researchers
at present, ethylbenzene catalytic dehydrogenation is mostly used in the production of styrene in China. The small devices built in the 1960s and 1970s have high energy and material consumption and lack market competitiveness. With the introduction of foreign technology, most of them have been discontinued. The remaining sets have been subject to many technical transformations, and the energy and material consumption have decreased. At the same time, the production is still maintained by taking advantage of the regional price difference and the demand for downstream products of the enterprise
II. Key parts and equipment
the reaction post in the styrene production unit is produced in the environment of high temperature, high pressure, flammable, explosive, toxic and harmful materials, and the distillation post also has a similar situation. Therefore, safety technical regulations should be observed in the production process of styrene
1. furnace area
(1) before ignition of steam superheater, open the air valve for ventilation, and analyze the furnace and operating environment for hot work. All relevant locks should be hung, the oxygen content in the fuel gas should be analyzed to be less than 2%, and it is strictly forbidden to carry liquid (heat preservation and condensate drainage should be carried out in winter to prevent deflagration damage to the furnace body caused by liquid). During shutdown, the fuel system shall be equipped with a cut-off blind plate to prevent fuel leakage into the furnace and the surrounding environment from causing accidents.
(2) temperature rise, constant temperature and temperature drop shall be strictly controlled according to the temperature curve during startup and shutdown. During normal production, all process parameters should be strictly controlled within the range of process indicators.
(3) after the ignition of the steam superheater (including normal 1. Simple interface production), check whether the combustion condition in the furnace is normal.
(4) when the steam superheater is shut down for maintenance, blind plates must be added to the fuel, raw materials, steam (including fire-extinguishing steam) to prevent accidents caused by channeling into the maintenance site.
(5) check the quench boiler and drum for external leakage and normal blowdown to ensure the quality of boiler water. At the same time, it is necessary to regularly check and calibrate whether the drum liquid level gauge is accurate, so as to prevent shutdown or accident caused by false liquid level.
(6) it is strictly forbidden to stack combustibles around the furnace area, and the scaffold should be removed in time after the maintenance. When a large amount of hydrocarbon is released from the device, the furnace area may become its fire source, so the steam superheater water curtain should be opened for protection, and the boiler should be shut down at the same time.
(7) in case of furnace tube rupture, stop the furnace immediately and put out the fire (but remember that the furnace tube steam cannot be stopped and it needs to be increased appropriately) turn on the fire extinguishing steam (condensate should be discharged, otherwise the condensate will damage the furnace tube) and take corresponding measures for all systems of the whole device.
2. Compression area
this area is equipped with fire water facilities, automatic combustible gas detection and alarm facilities.
(1) fire water facilities: each compressor is equipped with two streams of fire water, which supply the fire sprinkler on the upper part of the compressor at the same time, forming a water curtain.
(2) automatic combustible gas detection and alarm facilities: there are 7 automatic combustible gas detection points around the compressor in this area, and the automatic combustible gas detection alarm is installed on the dashboard in the instrument control room. When the concentration of combustible gas reaches a certain value, the cutting alarm will sound.
(3) safety valve: there is a safety valve on the top of each compressor tail gas discharge system, which will automatically start and trip under overpressure.
(4) interlocking: in order to prevent the post personnel from misoperation, an instrument interlocking alarm system is set. When the post personnel misoperate, the indoor DCS will send an alarm, and the indoor personnel can notify the post personnel in time.
3. Reactor area
(1) the reactor includes alkylation reactor and dehydrogenation reactor. These two reactors are exothermic reaction and endothermic reaction. The introduction of poisons must be strictly controlled to prevent coking and deactivation of the catalyst
(2) pay special attention to the leakage of hydrogen. The fire flame of hydrogen leakage is light blue and is not easy to be found
(3) during normal production, due to the high pressure and temperature of the reactor, it should be strictly controlled
(4) when each reactor is shut down, it is necessary to discharge the liquid first and then release the pressure, so as to prevent the low boiling point liquid phase materials from being gasified in the equipment after releasing the pressure first, resulting in low-temperature cold quenching damage to the equipment. The company aims to build a high-quality project and cause accidents
(5) always check the leakage caused by corrosion at the manhole, valve, instrument connector, liquid level gauge, flange elbow, etc. of the reactor.
(6) the reactor safety valve and emergency vent valve must be calibrated regularly to keep them in good condition and play their due role in the event of an accident
(7) in case of fire in the reactor, in addition to giving an alarm and putting out the fire immediately, an emergency shutdown shall be carried out at the same time, and the materials shall be sent out or discharged into the flare. Actively assist professional firefighters to cut off the source of materials (especially the storage tank) and other measures, and take key breakthroughs against the fire points and eliminate them one by one. After the fire is extinguished, pay attention to check the ignition point to prevent energy, complete the test of various mechanical performance indexes such as compression spring, tension spring and torsion spring, and stop re ignition
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