Safety knowledge of dust explosion?

It is very important to know the safety precautions of dust explosion. Only by understanding the knowledge points can we solve practical problems better. Every detail is important and should be taken seriously. Zhong Da Consulting will explain the knowledge of dust explosion safety prevention for you.

Safety knowledge of dust explosion: dust explosion = concentration+open flame

According to experts, when the dust is suspended in the air and reaches the explosion concentration limit, it will explode when it encounters a fire source (including open flame, static electricity, friction, etc.). As for the size of the injury, it is related to the amount of dust, space and the intensity of personnel on the job site.

At the same time, professionals say that dust explosion requires two conditions, one is to reach a certain concentration, and the other is to have an open flame. According to the regulations, the safety requirements of the workshop are extremely high, and strict regulations should be made on dust concentration, ventilation and open flame.

Dust explosion is one of the most harmful explosions in factory explosion accidents, and the more closed the workshop, the greater the explosion power. As early as 1987, a dust explosion occurred in Harbin, Heilongjiang Province, which killed 58 people and injured more than 70 people.

Safety precautions against dust explosion in China.

Since 20 10, dust explosion accidents have occurred frequently in metallurgy, nonferrous metals, building materials, machinery, light industry, textiles, tobacco, commerce and other industries in China, which has become a prominent problem in the safety production of metallurgical and other industrial and commercial enterprises.

At the beginning of 2065438+01May, state administration of work safety issued the Notice on Further Strengthening the Prevention of Dust Explosion Accidents in Metallurgical Commercial Enterprises. The notice clarified four reasons for the dust explosion accident: first, the enterprise did not know enough about the hazards of dust operation, the safety management rules and regulations were not perfect, and the safety management was not in place; Second, the safety investment of enterprises is insufficient, and the safety equipment and facilities such as ventilation, dust removal, fire prevention and explosion prevention at the job site are not perfect; Third, the enterprise safety education and training work is ineffective, and the operators lack relevant safety knowledge; Fourth, some areas have not paid enough attention to the safety production work involving dust operations in metallurgical and other industrial and commercial enterprises, and the supervision and management are not targeted, and there are weak links and loopholes.

On August 20 12, the office of the safety committee of the State Council City, China issued a notice again to carry out special treatment on safety production of aluminum and magnesium products processing enterprises throughout the country.

The harm of dust is not just "explosion"-pneumoconiosis.

After the explosion tragedy, some workers said that the company had not conducted safety knowledge training. "Nobody said that dust would explode." The factory's indifference to safety education is shocking, and the hidden danger of dust explosion cannot be ignored, but in fact, even without such a tragic explosion, isn't such a working environment that can make workers "black" dangerous? The relatively sudden and deadly dust explosion, the "ash" stuck on the skin and inhaled into the body itself is a hidden "killer". There is a data to refer to. Last month's Survey Report on the Living Conditions of Migrant Workers' Pneumoconiosis in China (20 14) pointed out that pneumoconiosis has become the "first killer" of occupational diseases in China. last year

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There were 26,393 cases of occupational diseases reported in China, including 23 cases of pneumoconiosis (KLOC-0/52), accounting for 87.72% of the total reported cases. One message conveyed by the report itself is that whether it is to provide protective facilities for dust workplaces or to provide occupational safety and health training and education for workers and inform them of occupational hazards, it is a serious "debt" state.

Experts believe that the accident revealed that there are still huge loopholes in the protection of workers' occupational safety and health rights. Worryingly, small and medium-sized enterprises and township, private and individual enterprises are the "hardest hit areas" for occupational hazards, but the employees of these enterprises are not within the scope of obtaining health monitoring data from occupational disease statistics in China. Experts conservatively estimate that the actual number of pneumoconiosis patients will exceed 1 ten thousand. At the same time, the number of new cases of pneumoconiosis is increasing at a rate of more than 20,000 per year.

At present, among the workers exposed to dust in China, the number of migrant workers engaged in industries with high incidence of pneumoconiosis such as coal, building materials, metal mines and tunnel construction exceeds 80%. Especially in coal mining or grinding workshops, if dry operation is adopted, the dust concentration can exceed the national standard by hundreds or even thousands of times. In this environment, short-term operation can lead to pneumoconiosis 1 year, and almost no one is spared after exposure to 1~2 years. Workers will not only lose their ability to work, but also have a high mortality rate.

Related topics:

Harm of noise and pneumoconiosis and its protection knowledge

Explosion process

The explosion of dust can be regarded as the development of the following three steps: the first step is the rapid dry distillation or gasification of suspended dust under the action of heat source to produce combustible gas? Step 2: Mixed combustion of combustible gas and air? In the third step, the heat released by dust combustion is transferred to nearby suspended or blown dust by means of heat conduction and flame radiation, and these dust are heated and vaporized, so that the combustion cycle can continue. With the successive progress of each cycle, the reaction speed is gradually accelerated, and finally an explosion is formed through violent combustion. This kind of explosion reaction, as well as the explosion flame velocity, explosion wave velocity and explosion pressure, will be accelerated and increased continuously and develop by leaps and bounds.

Explosion characteristics

(1) Multiple explosions are the biggest characteristics of dust explosion.

(2) The minimum ignition energy required for dust explosion is relatively high, generally above tens of millijoules.

(3) Compared with combustible gas explosion, the pressure of dust explosion rises slowly, the duration of higher pressure is long, the released energy is large, and the destructive power is strong.

Explosion-proof vacuum cleaning equipment is needed to remove accumulated dust.

The management of fire-fighting facilities includes safe and reasonable selection, reasonable quantity allocation, reasonable location, correct storage and maintenance, correct operation and use of fire-fighting equipment. Clear responsibilities according to the production post system, and stick to it, check carefully, explain the basic knowledge of preventing dust explosion to employees, improve their technical quality and safety awareness, and improve their understanding of dust explosion. Don't think that backward production technology and management methods are also an explosion-proof measure. For example, some people think that dust explosion can be prevented by removing the doors and windows of the dust workshop or replacing mechanical equipment with a lot of manpower. These methods are neither scientific nor fundamental methods to eliminate explosions, but backward and negative practices that hinder the development of productive forces.

Explosion venting, explosion suppression and fire prevention measures

For dust explosion: on the one hand, it is to eliminate the factors that form dust explosion and prevent dust explosion. On the other hand, it is to control the explosion range and reduce the losses caused by the explosion. In some circumstances, explosion conditions have been formed or explosion factors can not be eliminated temporarily, explosion venting, explosion suppression and flameproof will reduce or control the losses caused by explosion.

Flameproof is to isolate the explosion through a certain device to prevent the explosion from spreading and spreading. Explosion-proof can use chemicals and chemicals.

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In grain processing, lifting, transportation and production, flameproof or other flameproof devices are usually used to control the entrance and exit of flameproof doors to isolate the explosion air billow, flame and spread, and avoid causing another explosion. & lt& lt What is a dust explosion?

When the dust meets a heat source (open flame or temperature) within the explosion limit, the flame spreads instantly in the whole mixed dust space, and the chemical reaction speed is extremely fast, at the same time, a lot of heat is released, resulting in high temperature and great pressure. The energy of the system is converted into mechanical work and radiation of light and heat, which has strong destructive power.

All solid substances in fine powder form are called dust. Dust that can burn and explode is called combustible dust. Is the dust floating in the air called suspended dust? Dust falling on the solid wall is called deposited dust.

It has been found that the dust of the following seven substances is explosive: metal (such as magnesium powder and aluminum powder)? Coal? Cereals (such as wheat and starch)? Feed (such as blood meal and fish meal)? Agricultural and sideline products (such as cotton and tobacco)? Forest products (such as paper flour and wood flour)? Synthetic materials (such as plastics and dyes).

Main hazards of dust explosion

(1) is extremely destructive. Dust explosion involves a wide range, and occurs from time to time in coal, chemical industry, pharmaceutical processing, wood processing, grain and feed processing and other departments. For example, during the period of 1952- 1979, there were 209 dust explosion accidents in Japan, with 546 casualties, including 46 crushing and pulverizing projects and dust collection and separation projects. 1965- 1980, there were 768 dust explosion accidents in the federal Republic of Germany, among which wood powder and wood products dust and grain feed explosion accidents were more serious, accounting for 32% and 25% respectively. In recent years, the annual frequency of dust explosion in China is: local explosion 150-300 times, system explosion 1-3 times, and it shows an increasing trend. These dust explosions in China, especially system explosions, have caused serious losses. Only Harbin flax factory 1987 flax dust explosion accident killed 58 people and slightly injured 177 people, resulting in a direct economic loss of 8.82 million yuan.

(2) It is easy to produce secondary explosion. In the first explosion, air billow blew up the dust deposited on the equipment or the ground. In a short time after the explosion, negative pressure will be formed in the central area of the explosion, and the surrounding fresh air will be poured in from the outside to form the so-called "return air", which will be mixed with the raised dust and ignited by the residual fire of the first explosion, causing the second explosion. In the second explosion, the dust concentration is generally much higher than that of the first explosion, so the power of the second explosion is much greater than that of the first explosion. For example, in a sulfur powder factory, an explosion occurred in the mill, and the explosion wave spread from the mill to the cyclone separator along the gas pipeline, and the cyclone separator exploded twice. The explosion wave spread to the workshop through the cracks produced in the cyclone separator after the explosion, and the sulfur dust settled on the buildings and process equipment was raised, and the explosion occurred again.

(3) can produce toxic gases. One is carbon monoxide? The other is the toxic gas decomposed by explosives (such as plastics). The production of toxic gases often causes a large number of people and livestock poisoning casualties after the explosion, which must be paid full attention to.

How to prevent dust explosion

One is to reduce the dust concentration in the air. Adopt equipment with good sealing performance to minimize the scattering and escape of dust, and install effective ventilation and dust removal equipment to strengthen cleaning work.

The second is to control the indoor temperature.

The third is to improve the equipment and control the fire source. Explosion-proof motor, explosion-proof lamp and explosion-proof switch should be used in dangerous places of dust explosion. Fourth, the explosion range should be controlled in advance. The fifth is to control the temperature and oxygen content. Where there is dust deposition in the container, cooling measures should be taken, and inert gas can be charged to dilute the oxygen content if necessary.

How to strengthen explosion-proof measures in chemical enterprises

Explosion-proof measures in storage structure design

Dust explosion should be considered in the design of silo workshop, and the silo line should be as far away from the office area and hygiene as possible.

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Living area, the distance is not less than 30m. For workshops smaller than 150m, there are no more than 10 workers, and two safety exits can be set. The width of the evacuation staircase shall be no less than 1. 1m, the width of the corridor shall be no less than 1.4m, and the width of the evacuation door shall be no less than 0.9m Independent manholes and air shall be set at the top of each warehouse.

Reduce dust production and dust collection points, and control environmental dust concentration.

For posts that generate dust or dust during storage and transportation, it is necessary to reduce dust generation and dust points, control dust diffusion, and reduce the dust concentration in the surrounding space so that the dust concentration does not exceed10 mg/m. We control the dust concentration far beyond the explosion limit and naturally control the occurrence of dust explosion.

Explosion-proof measures for dust removal and dust production equipment

For the dust production or dust removal system, we should focus on eliminating the ignition point, increasing the wind speed, or reducing the dust concentration in stages.

What needs to be emphasized here is that some people often think that with ventilation and dust removal system, the harm of dust explosion can be eliminated. This is wrong, because ventilation and dust removal can only change the concentration of dust in the environment, and the danger of dust explosion is transferred to the dust removal system, so the dust removal system is often the hazard source of dust explosion. If the dust removal system does not take effective explosion-proof technical measures, it is difficult to prevent dust explosion only by ventilation and dust removal. This is proved by dust explosion accidents at home and abroad. Because the dust concentration in the dust removal system is basically within the explosion limit, and it is a relatively closed space, the ignition probability of various impacts, friction, static electricity, open flame and smoldering is high.

Under this condition and environment, it is neither objective nor economical to change the dust concentration. We can improve the running wind speed, work under negative pressure, use explosion-proof fans and motors to eliminate ignition points, use flame-retardant antistatic materials in the system, have good grounding, ventilation and cleaning ports, and have danger prediction and monitoring systems such as pressure and temperature. When the system is in danger, the main engine automatically stops working, and all explosion-proof and explosion-suppression systems automatically work and produce.

Remove dust to prevent explosion.

To prevent dust explosion in other parts of the dust-producing workshop, we should mainly strengthen the cleanliness of the workshop and eliminate dust accumulation in equipment and environment. It is best to use negative pressure adsorption cleaning method as a cleaning method, which can avoid dust "moving" or failing to clean dead corners. Wet cleaning such as spraying is not suitable, because combustible dust is easy to produce combustible gas at a certain temperature and volatilize in space.

The harm of dust accumulation can not be underestimated, because it is the most important and dangerous dust source in the explosion. In the dust explosion, the dust accumulation state is more dangerous than the suspended state, and its explosion pressure rises fastest, causing the greatest destructive power.

Therefore, effectively eliminating dust accumulation is one of the main measures to prevent dust explosion.

Popular science: beware of explosive dust

Gas explosion and fireworks explosion are easy to understand, but how can dust explode? In fact, there are countless dusts that will explode, including coal dust, wood dust and plastic dust. Even flour, powdered sugar and starch may explode. Magnesium, aluminum, iron and other metal materials are safe when they are flaky or massive, but they are also easy to burn and explode quickly after turning into dust. Under certain conditions, the explosive power of dust is no less than that of explosives.

But don't worry that a bag of flour in the cupboard will explode one day. Dust explosion needs to meet certain conditions. First of all, the dust itself must be combustible. Secondly, dust must be suspended in the air to a certain concentration. Thirdly, dust must have a considerable specific surface area (total area per unit mass) and sufficient ignition energy.

Dust concentration, particle size, air humidity, oxygen content and other factors will affect the risk of dust explosion. The finer the particles are, the larger the specific surface area is, and the longer they are suspended in the air, the more oxygen they absorb.

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The greater the risk of explosion. The more airtight the space, the greater the explosive force of dust. If combustible gas exists in dusty environment at the same time, the risk of dust explosion will be greatly increased.

At present, it is found that the main industries with dust explosion danger are metal processing, coal, synthetic materials, textile and chemical fiber, grain and agricultural and sideline products processing and feed. On the basis of more than 8,000 sets of data experiments and evaluations on various industries 108 industrial dusts, the German Federal Institute for Materials Research and Audit has compiled an online database of dust parameters for 20 12 years, through which parameters such as minimum energy value, light-off temperature, minimum detonation critical value and pressure generated by explosion of various dusts can be found out under many specific conditions.

Convenient tip: don't let the dust around you become an invisible bomb.

According to experts, the reason for the dust explosion is that the dust suspended in the air reaches a certain concentration, which is caused by the high air pressure formed after the fire on Mars. But dust explosion must meet three conditions at the same time. First, dust must be combustible, and non-combustible dust will not explode; The second condition is to have an accelerant, such as air; The third condition is to have a little fire source to provide heat source for combustion.

Experts remind that industrial dust is far away from the public, but some dust generated in daily life also needs attention, such as flour, cocoa powder, stick powder, etc., which are all defined as combustible dust. Once flour becomes fine dust and flies in the air, every dust can fully contact with the air, and it may ignite and explode when it meets an open flame. However, the probability of dust deflagration in daily life is relatively low, but we should be careful not to spill these dust. If you accidentally spill flour, cocoa powder or sticky powder, be sure to turn off all fire sources first and immediately open the window for ventilation. At the same time, the public should pay special attention when storing flour, cocoa powder and noodles, and it is best not to put them in places that are easy to contact with open flames.

Germany's "Other Stones" to Prevent Dust Explosion

Dust explosion is a potential safety hazard in many industrial fields. In order to help safety assessment institutions and enterprises to efficiently investigate hidden dangers, Germany established an online database of dust parameters related to safety production for the first time at the end of 20 12, which was used by relevant institutions and enterprises nationwide for free.

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