Fire and explosion prevention technology in the pr

Fire and explosion prevention technology in chlor alkali production

due to the particularity of chlor alkali products and their production process, the safety work in chlor alkali production, especially fire and explosion prevention, is particularly important. In the production of chlor alkali by electrolysis, in addition to caustic soda and chlorine, hydrogen is also produced. Hydrogen and air or hydrogen and chlorine can form flammable and explosive mixtures in the closed equipment and pipelines of electrolysis, chlorine cooling and drying, hydrogen cooling and transmission, chlorine liquefaction, synthetic hydrochloric acid, organic and inorganic chlorination and other sections; Chlorine may also contain explosive nitrogen trichloride impurities; The internal pressure of liquid chlorine storage tank and steel cylinder may also exceed its maximum operating pressure, etc. Violation of rules and regulations and safety (technical) regulations in production will cause failures, fires and even explosions, causing huge losses and injuries to enterprises and employees. Therefore, fire prevention and explosion prevention are the top priority of safety work in chlor alkali production

1. combustion and explosion of hydrogen air mixture and preventive measures

when the hydrogen content in the mixture of hydrogen and air reaches 4.1% - 74.2% (volume percentage), it has explosion danger at 20 ℃ and normal temperature. For the safety of chlor alkali production, the allowable content of hydrogen in the mixture of hydrogen and air is 4% (volume). Strict sealing of equipment and pipelines is the most important measure to prevent the explosion of the mixture of hydrogen and air in the successful exploration of the best process parameters of reverberatory lead smelting and the ratio of feed material additives. In addition, some safety measures can be taken, such as installing an explosion-proof membrane on the container. When the pressure in the container rises slightly, the explosion-proof membrane will burst; Flame arresters with different structures can also be used

hydrogen in chlor alkali production is produced in the cathode box of the electrolytic cell. In order to prevent the hydrogen from mixing with air and avoid the formation of explosive mixed gas, all connection points from the cathode box of the electrolytic cell to the hydrogen main pipe and the whole hydrogen cooling and transmission system should be strictly sealed, and the positive pressure of the hydrogen system should be guaranteed

in the electrolytic plant, if a large amount of hydrogen is vented and cannot be discharged out of the room in time, explosive hydrogen air mixture may also be formed. Therefore, during the operation of the electrolytic cell, it is forbidden to discharge hydrogen into the plant, and there is no ventilation dead zone in the upper structure of the electrolytic plant; Fireworks shall be strictly prohibited in the electrolytic plant. During power failure, hot work regulations shall be strictly observed

fireworks shall be strictly prohibited at the hydrogen vent pipe, and appropriate anti-static and lightning protection devices shall be provided to prevent the discharged hydrogen from catching fire. Ten thousand fires should be properly handled. The electrolytic cell should not be powered off or reduced in current, so as to avoid backfire and explosion

when the hydrogen cooling and transmission system is overhauling the hydrogen pipeline or carrying out other repair work, it is necessary to regularly check whether there is gas in the overhauled equipment or pipeline with analytical methods not only before the overhaul work, but also during the overhaul. During the overhaul, non sparking antimagnetic tools must be used. Inert gases such as nitrogen or carbon dioxide have an impact on the explosion limit of the mixture, so adding nitrogen or carbon dioxide to the explosive mixture of hydrogen and air will not cause an explosion. Therefore, nitrogen or carbon dioxide is often used to replace explosive mixture during maintenance

2. combustion and explosion of hydrogen chlorine mixture and preventive measures

the mixture of hydrogen and chlorine is also an explosive mixture, which is limited to 5% - 87.5% (volume percentage) that may lead to accidents

chlorine in chlor alkali production is generated from the anode liquid of the electrolytic cell. The pressure in the anode chamber and cathode box is not properly controlled, or the anode liquid level is low, and policy support is a beneficial guarantee for the development of recycled plastic granulator. Poor adsorption quality or damage of the diaphragm of the cathode box will lead to the hydrogen content in chlorine exceeding the standard, and it is easy to explode when the explosion limit is reached. Therefore, in order to ensure the safe operation of the electrolysis process, the above important indicators must be strictly controlled

because chlorine contains a small amount of hydrogen, and the density of hydrogen is much lower than that of chlorine, it is very easy to cause hydrogen accumulation in the process of chlorine cooling, drying, compression and transportation. Over time, it can reach the explosion limit, and explode in the case of ignition source. Therefore, unreasonable links in the production process should be improved to eliminate hydrogen accumulation and avoid accidents

during the liquefaction process of chlorine, because most of the chlorine is liquefied into liquid chlorine, the amount of chlorine in the liquid chlorine exhaust gas is correspondingly reduced, and the amount of hydrogen is correspondingly increased. According to the explosion range of hydrogen in chlorine, the hydrogen content in liquid chlorine waste gas is usually controlled to not exceed 4%. In the production process of chlorine liquefaction, the maximum chlorine liquefaction amount should be determined according to the hydrogen content in chlorine. If the amount of hydrogen brought in by chlorine is less, the liquefaction efficiency can be higher, otherwise it should be lower, and the liquefaction efficiency cannot be determined arbitrarily for the sake of one-sided pursuit of economic benefits

the synthetic hydrochloric acid section is a post with relatively more combustion and explosion accidents. Strictly control the purity of hydrogen and the hydrogen content in chlorine, and do not ignite if it is unqualified; The synthetic furnace system cannot be ignited without evacuation and sampling analysis; During operation, the ratio of chlorine to hydrogen should be strictly controlled at 1:1.1. If the amount of hydrogen is small and the chlorine reaction is incomplete, free chlorine will be discharged into the atmosphere, causing waste and pollution. If there is a large amount of excess hydrogen, explosion is easy to occur in the furnace; This post should strictly prohibit the current furnace charge price in Jiangsu Province to be maintained at 1590 ⑴ 630 yuan/ton of fireworks. When hot work maintenance is required, hot work permit should be handled in strict accordance with the regulations

3. Explosion of nitrogen trichloride and its preventive measures

nitrogen trichloride (NCL;), It is yellow oily liquid at room temperature, similar to chlorine odor, with a specific gravity of 1.653 and a boiling point of less than 71 ℃. Nitrogen trichloride is a stronger oxidant than chlorine, which is very unstable and easy to cause explosion when heated. Nitrogen trichloride is powerful when it explodes, with a loud sound and bright flash. 2mol of nitrogen trichloride is decomposed into 1mol of nitrogen and 3mol of chlorine when it explodes, and 459.8kj of heat is released at the same time. When water or sodium chloride aqueous solution with high ammonium salt content is used in chlor alkali production, nitrogen trichloride may appear in the produced chlorine. Nitrogen trichloride is liquefied together in the process of chlorine liquefaction. However, when liquid chlorine is evaporated into gas chlorine in the evaporator, because the boiling point of nitrogen trichloride is much higher than that of chlorine, when liquid chlorine is evaporated, nitrogen trichloride is concentrated as a liquid phase, and when its concentration reaches a certain degree, it is very easy to explode. Therefore, in order to work safely, we must strictly control the ammonium content of refined brine in the tank and the nitrogen trichloride content in the liquid chlorine sewage. After the evaporation of liquid chlorine in the liquid chlorine vaporizer, it should be washed systematically and regularly with water or alkali, and blown away with compressed air for a long time to remove the accumulated residual liquid chlorine. The liquid chlorine cylinder and storage tank can be heated and repaired only after the residual liquid chlorine polluted by nitrogen trichloride is completely removed

4. explosion and preventive measures of liquid chlorine containers

liquid chlorine containers such as steel cylinders and storage tanks will leak if the internal pressure exceeds their maximum operating pressure Explosion and other malignant accidents. The main reasons for this high pressure are: sunlight exposure, fire or other external heat sources, no gas space or too small space in the container, liquid expansion when the temperature rises, etc. In order to ensure the normal operation of liquid chlorine containers, we must strictly abide by the chlorine safety regulations and eliminate violations; On the other hand, safety valves, rupture discs, etc. can be installed on the container to automatically discharge the materials in the container when the maximum operating pressure is exceeded

5. Explosion and preventive measures in the production process of organochlorine products

during the chlorination process of organic substances, fire and explosion prevention work should be done well according to the physical and chemical characteristics of organic raw materials. For example, the raw material toluene (five color transparent liquid, boiling point 110.6 ℃, flash point 4.5 ℃, spontaneous combustion point 480 ℃, explosion limit in air 1.27%-7%) used in our company's benzyl chloride products is a flammable and explosive liquid. Its vapor can form an explosive mixture with air and chlorine, and it is very easy to explode in case of ignition source. Therefore, the benzyl chloride production workshop should pay attention to the following points: thoroughly control the leakage of toluene equipment and pipelines, and avoid the formation of explosive mixture of toluene vapor and air in space; Strictly control the process index of chlorination process to avoid the formation of explosive mixture of toluene and chlorine in the equipment; It is forbidden to tamper with toluene and chlorine valves during maintenance; No fireworks in the workshop; Eliminate electrostatic hazards and electrical sparks

the above discusses the fire and explosion prevention of key links in chlor alkali production. With the development of the situation, safety work is becoming more and more important. It is hoped that everyone can start from their own positions, master the safety technical knowledge of their own positions, closely connect with the actual production, truly understand how to be safe, and turn passivity into initiative, so as to promote the safety work and economic benefit development of the whole enterprise