An explosion occurred in Kunshan on August 2 , 2014 , killing 75 people and injuring 187 people. Although it was many days later , the explosion sounded as if it was still in the ear. The main cause of the explosion in Kunshan was the dust explosion, and the safety of the chlor-alkali industry. Self-examination, mastering the relevant knowledge of dust explosions, preventing the occurrence of explosions, and in the end, the alarm bells will be able to truly learn from this accident. According to Hu Yongqiang, the leader of the safety expert group of the chlor-alkali association, Zhang Xinli, the leader of the PVC expert group, organized an article on the harm of PVC dust in the calcium carbide method for your reference.
Each workshop in the production of calcium carbide in the calcium carbide process produces dust more or less. The most common amount of dust is the acetylene workshop, and the types of dust generated are also the most.
The acetylene process of calcium carbide method is divided into dry acetylene process and wet acetylene process. In short, in the case of normal production, the main processes for generating dust in the two production processes are three, namely the transportation process of calcium carbide transportation and the disposal of carbide slag. The process and the breaking of large pieces of calcium carbide into a calcium carbide process that meets the particle size requirements. The process of disposal of calcium acetylene process calcium carbide slag refers to the process of concentrated pressure filtration and calcium carbide slag after the calcium carbide slurry is discharged from the generator; the dry acetylene process calcium carbide crushing process increases the small calcium carbide crushing into 3mm or less compared with the wet acetylene process. The process of small particle calcium carbide. The dust in the acetylene workshop is mainly divided into calcium carbide slag dust and calcium carbide dust. The following is mainly for the production process, dust properties, dust hazard and dust treatment analysis of calcium carbide slag dust and calcium carbide dust generated by the acetylene workshop in the dry acetylene production process.
Calcium carbide slag dust
Dust properties, production process, and hazard analysis: The carbide slag dust is generated by the process of discharging the carbide slag from the generator and the transportation process of the carbide slag. The calcium carbide slag discharged from the generator is a powdery substance having a water content of 10% or less, in which acetylene gas, water vapor and trace amounts of other gases are mixed, and the temperature is about 100 degrees. The carbide slag discharged from the generator is high in temperature and mixed with gas. During the discharge generator and conveying process, the gas will diffuse into the space and carry a certain amount of calcium carbide slag powder, which causes the atmosphere around the conveying device to contain calcium carbide slag and acetylene. Gas and other irritating odors. The main component of calcium carbide slag is Ca(OH)2 . Calcium hydroxide is highly alkaline and corrosive. Therefore, the dust scattered in the atmosphere is mainly Ca(OH)2 , which is easily inhaled into the nasal cavity and then enters the respiratory tract and burns. Respiratory system; calcium carbide slag dust floating in the atmosphere, combined with condensed water in the air, water-containing calcium hydroxide and alkaline condensate will corrode pipelines and conveying equipment; acetylene gas diffused into the atmosphere is flammable and explosive gas Mixing with air can form an explosive gas, posing a danger to safe production.
Dust treatment analysis: Since the carbide slag from the generator contains acetylene gas and water vapor, it is easy to diffuse to form explosive gas and corrode equipment, polluting the environment. Therefore, the separation of calcium carbide slag just coming out of the generator and the environment is the primary treatment method. It is also necessary to install a device for exporting explosive gas. For the system that uses FU to transport calcium carbide slag, since the parts of the FU conveying system are all made of steel, it is necessary to completely seal the FU conveying system and carry out nitrogen protection to maintain the conveying system as a micro positive pressure on the equipment for storing the carbide slag. Export of acetylene gas. For the system of conveying calcium carbide slag by belt conveyor, the conveying process of the belt conveyor should be closed to prevent the gas-carrying carbide slag from diffusing into the atmosphere, and the acetylene gas is exported in the middle of the belt conveyor.
Calcium carbide dust
Dust properties, production process, hazard analysis: calcium carbide dust is mainly caused by the unloading of calcium carbide and calcium carbide crushing process. Industrial calcium carbide is a mixture of calcium carbide, quicklime and coke. It easily absorbs moisture from the air and weathers to produce acetylene gas and calcium hydroxide. There is a large amount of dust in the calcium carbide warehouse. Pulling the calcium carbide vehicle into the calcium carbide warehouse, due to the movement of the vehicle, the dust of the calcium carbide scattered on the ground rises and diffuses into the space of the calcium carbide warehouse. When the calcium carbide is discharged, the calcium carbide will impact the ground dust and raise the dust, while the calcium carbide itself The dust generated by the weathered calcium carbide will also diffuse into the space; in the crushing process of calcium carbide, the first-stage and second-stage crushing adopts the jaw crusher, and the calcium carbide is strongly impacted in the crusher, and is broken into small pieces of calcium carbide, resulting in A large number of powdered and small particles of calcium carbide, although there are dust removal devices in the current crushing process, but because of the transmission equipment, there is still a certain amount of calcium carbide dust dispersed into the space, the carbide dust dispersed into the space absorbs the moisture in the air, producing acetylene Gas and Ca(OH)2 dust, calcium carbide dust and Ca(OH)2 dust are easily inhaled into the nasal cavity by the operator, and then enter the respiratory tract, burning the respiratory system, and the carbide dust adheres to the operator's skin. When sweating, it is easy to burn the skin; the acetylene gas produced by the hydrolysis of calcium carbide dust is a flammable and explosive gas, which easily diffuses into the atmosphere and is mixed with air. The formation of explosive gas, pose a threat to safety in production. Ultra-fine breaking is to break small pieces of calcium carbide into calcium carbide below 3mm . The crusher and conveying equipment are completely sealed. At the same time, some nitrogen protection is carried out. As long as the equipment is maintained and maintained regularly, there is basically no dust leakage.
Dust Control Analysis : For the process of producing calcium carbide dust, it is necessary to reduce the diffusion of calcium carbide dust in the atmosphere from the following aspects. The first is to use fixed-point unloading to reduce the operation of vehicles in the calcium carbide warehouse, reduce the disturbance of the vehicle's calcium carbide dust on the ground in the calcium carbide warehouse, and install a dust removal system at the fixed-point unloading point to reduce the diffusion of dust into the warehouse. The second is to regularly clean the dust in the calcium carbide warehouse to reduce the accumulation of dust in the warehouse; the third is to regularly clean the pits of the first and second-stage crushing equipment to reduce the accumulation of calcium carbide dust in the pit; the fourth pair of crushing system The equipment and the calcium carbide feeding and discharging chutes are regularly inspected, and the damaged parts are repaired in time to ensure the normal operation of the equipment and the chute, and the leakage of calcium carbide dust is reduced.
In summary, whether it is calcium carbide slag dust or calcium carbide dust, it will affect the health of operators, causing damage to the environment and posing a threat to safety. In order to eliminate the above effects, it is necessary to protect from the aspects of process, equipment and management. From the process, reduce the generation of dust and the accumulation of acetylene gas, such as the use of pipes and closed chutes for the transport of calcium carbide slag and calcium carbide to reduce the contact of dust with the outside world; the installation of exhaust ducts and the ventilation of the warehouse at the top of the pit cover Install a ventilation fan at the corner to reduce the risk of acetylene gas explosion. On the equipment, increase the inspection intensity and maintenance quality to ensure the normal operation of the equipment, reduce the leakage rate and maintenance frequency of the equipment, and reduce the amount of dust leakage during the operation of the equipment. In management, operators must be strictly required to operate according to the operating procedures, first start the dust removal device, then run other equipment, strengthen the training and management of equipment maintenance personnel, and regularly test and clean the acetylene gas gathering area.
Through the above efforts, the operating environment of the acetylene workshop will be greatly improved, the threat of acetylene gas explosion to the workshop will be eliminated, the impact of dust on the health of the operators will not exist, and the clean and safe working environment will no longer be a dream.
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