Safety technology for the most typical reaction pr

2022-08-05
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Safety technology of typical reaction process

1 main danger of oxidation reaction

(I) oxidation reaction needs to be heated, and most reactions are exothermic. Therefore, if the reaction heat is not removed in time, the reaction will be out of control and even explode

(2) most of the oxidized substances in the oxidation reaction are flammable and explosive substances, such as ethylene oxidation to ethylene oxide, methanol oxidation to formaldehyde, and toluene oxidation to benzoic acid. Ethylene is a flammable gas, toluene and methanol are flammable liquids

(3) some oxidants in the oxidation reaction are strong oxidants, such as potassium permanganate, potassium chlorate, hydrogen peroxide, benzoyl peroxide, etc., which are very dangerous. If they are exposed to high temperature, impact, friction or contact with organic substances and acids, they are easy to cause combustion or explosion

(4) many oxidation reactions are the reaction of flammable and explosive substances with air or oxygen when considering social trends. The reaction feed ratio is close to the explosion limit. If the material ratio or reaction temperature is not properly controlled, combustion and explosion are very likely to occur

(5) oxidation reaction products also have fire and explosion hazards. Such as ethylene oxide, 36.7% formaldehyde aqueous solution, etc

(6) some oxidation reactions can produce peroxide by-products, which have poor stability and are easy to decompose in case of high temperature, impact and friction, resulting in combustion or explosion. For example, the upsurge of new energy caused by this may start to break out this year. In the process of acetaldehyde oxidation to acetic acid, peracetic acid was produced at the very beginning

2. Safety measures for oxidation process

(1) in the oxidation reaction, the feed ratio of oxidant must be strictly controlled. When air or oxygen is used as oxidant, the feed ratio of reaction should be strictly controlled outside the explosion range

(2) the feeding speed of oxidant should not be too fast to prevent excessive and wrong addition. The reaction process shall be equipped with good mixing and cooling devices, and the reaction temperature and flow shall be strictly controlled to prevent overheating and overpressure

(3) prevent equipment and materials from containing impurities to provide catalysts for oxidants. For example, some oxidants will decompose in the presence of metal impurities. Before entering the reactor, the air must be purified to remove dust, water, oil and impurities that may reduce the activity of the catalyst or poison, so as to reduce the risk of ignition and explosion

(4) flame arresters shall be installed on reactors and pipelines to prevent flame spread and backfire. The contactor shall be equipped with pressure relief device and adopt automatic control and alarm interlocking device as far as possible

(II) reduction reaction

1 Main hazards of reduction reaction

(1) many reduction reactions are carried out under high temperature and high pressure in the presence of hydrogen. If hydrogen leakage occurs due to misoperation or equipment defects, it is very easy to explode

(2) catalysts used in the reduction reaction, such as Rene nickel, palladium carbon, etc., have the risk of spontaneous combustion after moisture absorption in the air. Under the condition that there is no ignition source, the mixture of hydrogen and air can be ignited

(3) the solid reducing agents used in the reduction reaction, such as sodium bicarbonate, lithium aluminum hydride, potassium borohydride, etc., are flammable dangerous goods when exposed to moisture

(4) intermediates of reduction reaction, especially those of nitro compound reduction reaction, also have certain fire hazards. For example, in the process of reducing o-nitroanisole to o-aminoanisole, azoanisole which can spontaneously ignite at 150 ℃ is produced. If the reaction conditions of aniline are not well controlled in the production process, cyclohexylamine with great explosion risk can be generated

(5) hydrogen at high temperature and high pressure has carburizing effect on metal, which is easy to cause hydrogen corrosion

2. Safety measures for reduction reaction process

(1) various reaction parameters and conditions such as temperature, pressure and flow must be strictly controlled during operation

(2) pay attention to the correct use and disposal of catalyst. Raney nickel, palladium carbon and other catalysts shall not be exposed to the air at ordinary times, but shall be immersed in alcohol. Before the reaction, all the air in the reactor must be replaced with nitrogen. After the oxygen content is determined to meet the requirements, hydrogen can be introduced. After the reaction, if you do not purchase the equipment produced by our manufacturer, you should replace the hydrogen with nitrogen before discharging, so as to avoid the explosion in the case of spontaneous combustion of catalyst due to the mixing of air and hydrogen in the reactor

(3) pay attention to the correct use and disposal of reducing agent. For example, lithium aluminum hydride should be stored submerged in kerosene. Nitrogen shall be used to replace it before use, and feeding and reaction shall be carried out under the protection of nitrogen

(4) the material selection of equipment and pipelines shall meet the requirements and be tested regularly to prevent accidents caused by hydrogen corrosion

(5) the electrical equipment in the workshop must meet the explosion-proof requirements. The ventilation of the workshop is good, and the lightweight roof should be used. Skylights or hoods should be set to make it easy for hydrogen to escape. The tail gas discharge pipe should be more than 2 m higher than the roof ridge and equipped with flame arresters

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