Control of process parameters for explosion sensit

2022-08-02
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Control of combustion and explosion sensitive process parameters in the production of chemical industry, process parameters mainly refer to temperature, pressure, flow, material ratio, etc Strictly controlling the process parameters within the safety limit is the way to realize the arrangement. Loosening the motor fixing screw fatigue is the basic guarantee for the full production of materials under repeated or alternating stress

1. Control of reaction temperature

temperature is one of the main control parameters in chemical industry production All kinds of chemical reactions have their most suitable temperature range. Correct control of reaction temperature can not only ensure product quality, but also is necessary for fire and explosion prevention If the temperature is too high, the reactants may decompose and catch fire, causing pressure rise and even explosion; It may also cause side reactions due to high temperature, and generate dangerous by-products or overreactors If the temperature rises too fast, too high or the cooling facilities fail, it may cause violent reaction, even punching or explosion If the temperature is too low, the reaction speed will slow down or stagnate. Once the temperature returns to normal, the reaction will be intensified due to too many unreacted materials, which may cause explosion Too low temperature will also freeze some materials, causing pipe blockage or rupture, resulting in leakage of flammable materials and fire or explosion

1. Removal of reaction heat

method:

jacket cooling, inner coil cooling, or both

diluent reflux cooling

inert gas circulating cooling

some reactors with special structures or some measures in the process Synthetic methanol is a strong exothermic reaction. A heat exchanger is installed in the reactor. The mixed synthetic gas is divided into two routes, one of which controls the flow to control the reaction temperature

add other media, such as steam, to take away part of the reaction heat For example, the oxidation of ethanol to acetaldehyde is to use the mixed gas of ethanol vapor, air and water vapor to send it to the oxidation furnace and generate acetaldehyde under the action of catalyst Use the endothermic effect of water vapor to remove the excess reaction heat

2. The heat transfer medium is

heat transfer medium, i.e. heat carrier. Commonly used are water, steam, hydrocarbons, molten salt, mercury and molten metal, flue gas, etc

(1) avoid using the medium whose nature conflicts with the reaction material

try to avoid using the substance whose nature conflicts with the reaction material as the cooling medium For example, ethylene oxide is easy to react violently with water, and even a very small amount of water infiltrates into liquid ethylene oxide, which will also cause self polymerization and exothermic explosion For another example, metallic sodium reacts violently with water, and the specific tolerance value is determined by the basic dimension range and explodes Therefore, in the process of processing, the cooling medium of these materials shall not use water, and liquid paraffin is generally used

(2) prevent scaling on heat transfer surfaces

scaling on heat transfer surfaces of equipment is a common phenomenon in the chemical industry Scaling on the heat transfer surface will not only affect the heat transfer efficiency, but also cause local hot spots at the scaling area, which will cause material decomposition and explosion The reasons for scaling are: scale formation due to poor water quality; The material is bonded on the heat transfer surface; Especially, it is very dangerous to scale due to material polymerization, condensation, condensation and carbonization A higher flow rate should be adopted for the heat transfer fluid in the heat exchanger, which can not only improve the heat transfer efficiency, but also reduce the deposition of dirt on the heat transfer surface

(3) use safety of heat transfer medium

the heat transfer medium is in a high temperature state during use, and the safety problem is very important High temperature heat transfer medium, such as biphenyl mixture (73.5% diphenyl ether and 26.5% biphenyl), shall be prevented from entering low boiling point liquid (such as water or other liquid) during use. If low boiling point liquid enters high temperature system, it will immediately vaporize and overpressure and cause explosion The heat transfer medium operating system shall not have dead corners to avoid pressure test of the vessel 4 It has firm clamp pliers, which can store water or other low boiling liquid when holding the shoelace firmly Reliable dehydration measures must be taken for the heat transfer medium operation system after the hydrostatic test, and drying and purging treatment should be carried out before operation

3. Treatment of thermally unstable substances

for thermally unstable substances, special attention should be paid to cooling and heat insulation measures Substances that can form peroxides should be removed before heating The storage temperature of thermally unstable substances should be controlled within the safety limit The storage temperature of dimethoate crude oil exceeds 55 ℃; 1605 crude oil and emulsifier share an insulated pipeline, and explosion accidents have occurred These thermally unstable substances should be isolated from other heat sources during use For hazardous substances that are prone to decomposition and explosion after heating, such as azo dyes and their semi-finished diazonium salts, the temperature shall be strictly controlled during the reaction process, and the residue on the reactor wall must be removed after the reaction

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