Safety knowledge - dust explosion how to do?

Dust Explosion Safety Knowledge: Dust explosion = concentration + open fire

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

At the same time, professionals said 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 accident workshop are extremely high, and strict regulations should be imposed on dust concentration, ventilation, and open flame.

Dust explosion is one of the most hazardous explosions in a factory explosion. The more powerful the operation workshop is, the more explosive it is. As early as 1987 , a dust explosion occurred in Harbin City, Heilongjiang, which caused 58 deaths and injured more than 170 people.

China's dust explosion safety precautions

Since 2010 , dust explosion accidents have occurred in China's enterprises in the metallurgy, non-ferrous metals, building materials, machinery, light industry, textiles, tobacco, and commerce industries. This has become a prominent issue in the safety production of metallurgy and other industrial and commercial enterprises.

In early May 2011, China's State Administration of Work Safety issued a "further strengthen the notice metallurgical and other industrial and commercial enterprises dust explosion prevention work." Four reasons for the clear cause of dust explosions in the notification:

The first is the lack of understanding of dust hazards by companies and the inadequate safety management rules and regulations. Safety management is not in place;

Second, the company's investment in safety is insufficient, and workplace safety, facilities such as ventilation, dust removal, and fire and explosion protection are not perfect.

Third, corporate safety education and training work is ineffective; workers lack relevant safety knowledge;

Fourth, in some regions, attention has not been paid to the safety production of industrial dusts and dusts in metallurgy and other industrial and commercial enterprises. Supervision and management are not well-targeted, and weak links and loopholes exist.

August 2012, China Office of the State Security Committee again issued a notice in the country carry out machining aluminum and magnesium products production safety special treatment.

The danger of dust is not only explosive - pneumoconiosis

After the tragedy of the explosion, some workers said that the company had not trained safety knowledge and no one said that the dust would explode. The factory’s disregard for safety education is shocking. The hidden dangers of dust explosion cannot be ignored. In fact, even without such a fierce explosion, such a work environment that can make workers darken is not dangerous. The relatively sudden and fatal dust explosion, the ash sticking to the skin and being inhaled, is itself a hidden killer. According to the Survey Report on the Status of Migrant Workers Living in China with Pneumoconiosis (2014) , pneumoconiosis has become the number one killer of occupational diseases in China. 2013 full

Relevant experts believe that there are still huge loopholes in the protection of workers’ occupational safety and health rights. 　　

It is anxious that SMEs and township, private, and individual enterprises are the occupational hazards, but these employees are not within the scope of the health monitoring data of occupational disease statistics in China. The relevant experts have conservatively estimated that the actual number of pneumoconiosis patients will exceed 1 million cases. At the same time, new cases of pneumoconiosis is growing at more than 20,000 cases per year rate.

At present, of the workers exposed to dust in the country, more than 80 % of the peasant workers engaged in the high incidence of pneumoconiosis, such as coal, building materials, metal mines, and tunnel construction . Especially in coal mining or grinding workshops, if dry operations are used, the dust concentration can be several hundred times or even thousands of times higher than the national standard. In this environment, a short period of 1 year can cause pneumoconiosis, and it is almost inactive for 1 to 2 years. Fortunately, workers will not only lose their ability to work, but also have a high mortality rate.

Related topics:

Noise, pneumoconiosis hazards and protection knowledge

Explosion process

Dust explosion visualized by development are formed three steps: The first step is suspended dust or carbonized rapidly vaporized under the action of heat to produce a combustible gas the second step is mixed with the air and the combustible gas combustion section?? Three steps are the heat released by the dust combustion, which is transmitted to the nearby suspended or blown dust in the form of heat conduction and flame radiation. The dust is heated and vaporized and the combustion cycle proceeds. As each cycle proceeds progressively, its reaction speed is gradually accelerated, and explosive combustion is eventually formed. This explosion reaction and explosion flame speed, explosion wave velocity, explosion pressure, etc. will continue to accelerate and increase, and show a leaping development.

Explosive features

(1) multiple explosions is the most important feature dust explosion.?

( 2 ) The minimum ignition energy required for dust explosion is generally higher than tens of millijoules.

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

To remove dust, use explosion-proof vacuum cleaner

Fire-fighting facilities management, safe and reasonable selection of fire-fighting equipment, reasonable allocation of quantity, reasonable position, proper storage and maintenance, and correct operation and use. According to the production position system, we have clearly defined our responsibilities, persisted in implementation, carefully examined, explained to the employees the basic knowledge of preventing dust explosions, improved their technical quality and safety awareness, and raised awareness of dust explosions. Do not mistakenly think that the backward production process and management method is also an explosion-proof measure. For example, some people think that the removal of doors and windows of dust-producing workshops can prevent dust explosions, or use a lot of manual instead of mechanical equipment to prevent dust explosions. These methods are neither scientific nor a fundamental way to eliminate the explosion, but rather are backward and negative approaches that hinder the development of the productive forces.

Explosion, explosion suppression and explosion protection measures

For dust explosions, on the one hand, the formation of dust explosions is eliminated and dust explosions are prevented. The other is to control the scope of the explosion and reduce the damage caused by the explosion. In those circumstances where an environment has already formed an explosive condition or temporarily cannot eliminate the explosion factor, venting, detonating, and flameproofing will reduce or control the damage caused by the explosion.

Explosion-proof is to cut the explosion through a certain device to prevent the spread and spread of the explosion. Flameproof can be used chemical and

What is a dust explosion?

Dust in the explosion limit range, encountered heat (open flame or temperature), the flame spreads instantaneously throughout the mixed dust space, the chemical reaction speed is extremely fast, while releasing a lot of heat, forming a very high temperature and a lot of pressure, the system's The energy is converted into mechanical work as well as light and heat radiation, which has a strong destructive power.

Any solid substance that is in a fine powder state is called dust. The dust that can burn and explode is called combustible dust . The dust floating in the air is called suspended dust . The dust that settles on the solid wall surface is called deposition dust.

Dust has been found that the following seven types of explosive substances:????? Metals (e.g., magnesium, aluminum) coal grain (e.g. wheat starch) feed (e.g., blood meal, fish meal) agricultural products (such as cotton, tobacco) Lin Products (such as paper powder, wood flour) • Synthetic materials (such as plastics, dyes).

The main hazards of dust explosion

( 1 ) Extremely destructive. Dust explosions cover a wide range of areas. Coal, chemical, pharmaceutical processing, wood processing, food, and feed processing sectors all occur from time to time. Such as between 1952-1979, Japan for various types of dust explosion 209, a total of 546 casualties, of which crushing and milling dust separation engineering projects more prominent, each starting 46. In the Federal Republic of Germany , 768 dust explosions of various types occurred from 1965 to 1980. The most serious ones were wood flour and wood product dust and food feed explosion accidents, accounting for 32% and 25% respectively . In recent years, the frequency of dust explosions in China each year has been as follows: Local explosions have occurred between 1-3 times in 150-300 system explosions , and have shown an increasing trend. The dust explosions that occurred in China, especially systemic explosions, caused serious losses. In the linen flue explosion accident at the Harbin flax plant in 1987 , there were 58 dead , 177 were injured , and the direct economic loss was 8.82 million yuan.

( 2 ) It is prone to secondary explosions. The first explosion air blast blows up the dust deposited on the equipment or the ground. In the short time after the explosion, a negative pressure will be formed in the central area of ​​the explosion. The surrounding fresh air will be filled in from the outside to the inside, forming a so-called return wind. , Mixed with the raised dust, caused a second explosion under the ignition of the first explosion. In the second explosion, the dust concentration is generally much higher than that of an explosion, so the power of the second explosion is much greater than the first time. For example, in a sulfur powder plant, an explosion occurs inside an attrition mill. The explosion wave propagates along the gas pipeline from the attrition mill to the cyclone separator. A secondary explosion occurs at the cyclone separator. The blast wave is generated at the cyclone separator after the explosion. The cracks spread to the workshop, causing sulphur dust that settled on buildings and process equipment, and exploded.

( 3 ) Can produce toxic gases. One is carbon monoxide? Other explosives (such as plastic) decomposing toxic gas itself. The generation of poisonous gas often causes a large number of human and livestock poisoning after the explosion, and must be given full attention.

How to prevent dust explosion

The first is to reduce the concentration of dust in the air. Use well-sealed equipment to minimize dust emission, and install effective ventilation and dust removal equipment to enhance cleaning.

The second is to control the indoor temperature.

The third is to improve the equipment and control the fire source. Where there is a danger of dust explosion, explosion-proof motors, explosion-proof lights and explosion-proof switches shall be used. Fourth, the scope of the explosion should be controlled in advance. The fifth is to control the temperature and oxygen level. Where there is a container for dust deposition, there must be cooling measures, and if necessary, inert gas can be filled to dilute the oxygen content.

How Chemical Enterprises Strengthen Anti-explosion Measures

Explosion protection measures in storage structure design

When designing the silo workshop, consider dust explosion issues and try to keep the silo line away from the office area and

Reduce production and dust points and control environmental dust concentration

For dust-producing or dust-raising positions during storage and transportation production, dust production and dust raising points should be reduced, dust diffusion should be controlled, and the dust concentration in the surrounding space should be reduced so that the dust concentration does not exceed 10 mg/m . We controlled the dust concentration far beyond the explosion limit. In addition, it naturally controls the occurrence of dust explosions.

Anti-explosion measures for dust removal and dust production equipment

For dust production or dust removal systems, emphasis should be placed on eliminating priming points, increasing wind speed, or reducing dust concentration in stages.

It should be emphasized here that some people often think that with the ventilation and dust removal system, dust explosion hazards can be eliminated. This is wrong, because ventilation dust can only change the concentration of dust in the environment, and the harmfulness of dust explosion is transferred to the dust removal system. Therefore, the dust removal system is often a dangerous source of dust explosion, if not in the dust removal system. Effective explosion-proof technical measures rely solely on ventilation dust removal is difficult to prevent dust explosion. This is a proof of the dust explosion accident at home and abroad. Because the dust concentration in the dust removal system is basically within the explosion limit, it is also a relatively closed space, and there is a high probability of ignition due to various impacts, friction, static electricity, open flames, and smoldering.

In such conditions and environments, changing the dust concentration is not objective and economical. We can increase the operating wind speed and work under negative pressure, adopt explosion-proof fans and explosion-proof motors, eliminate ignition points, and use fire-retardant and anti-explosion systems. Electrostatic materials, with good grounding, with explosion vents and purge ports, and pressure, temperature and other dangerous forecast and monitoring system, will automatically stop the host work when the system occurs dangerous, explosion-proof explosion suppression system automatically work, The dust removal system was started 10 minutes before the start-up of the production equipment, and the dust removal system was stopped after the production equipment stopped working for 10 minutes.

Remove dust and prevent explosion

To prevent dust explosions in other parts of the dust production plant, the cleaning of the workshop should be strengthened to eliminate equipment and environmental dust. Clearance method is best to adopt negative pressure adsorption cleaning method, which can prevent dust from moving, or there is no corner cleaning. We should not use wet cleaning methods such as spraying, because combustible dust can easily generate flammable gas and evaporate in space at a certain temperature.

The damage to dust can not be underestimated, because it is the most important and most dangerous dust source for explosions. It is more dangerous for the state of dust and dust accumulation than suspension, and the maximum increase in explosive pressure and the greatest destructive power.

Therefore, the effective elimination of dust is one of the main measures to prevent dust explosion.

Science: alert to the explosion of dust

Gas explosions and explosions are easy to understand. How can dust explode? In fact, the dust that can explode is too numerous to mention, including coal dust, wood dust, plastic dust, etc. Even flour, sugar powder, and starch may explode. Metal materials such as magnesium, aluminum, and iron are safe when they are in the form of flakes or blocks, but they can easily burn and explode after they become dust. Under certain conditions, the power of dust explosion is no less than that of explosives.

However, there is no need to worry about a bag of flour in the cupboard exploding someday. Dust explosion needs to meet certain conditions. First, the dust itself must be flammable. Secondly, the dust must be suspended in the air and reach a certain concentration. The dust again must have a large specific surface area (the total area per unit mass), and it must be sufficient. Ignition energy.

Dust concentration, particle size, air humidity, and oxygen content all affect the risk of dust explosions. The finer the particles, the larger the specific surface area, and the longer the suspension time in the air, the greater the oxygen adsorption.

At present, there are mainly metal processing, coal, synthetic materials, light-spinning chemical fiber, grain and agricultural and sideline products processing and feed industries. The German Federal Institute of Materials Research and Review has compiled an on-line database of dust parameters in 2012 , based on more than 8,000 data sets of 108 industrial dust experiments and evaluations in various industries . Through it, it can be found that in a variety of specific situations, various dusts can be found. The minimum energy required to start the ignition, the light-off temperature, the minimum explosion threshold, and the pressure generated by the explosion.

Convenient reminder: Do not let the dust be a stealth bomb

According to experts, the reason for dust explosion is that the dust suspended in the air reaches a certain concentration, which is caused by the high pressure formed after Mars causes combustion. However, dust explosions must meet three conditions at the same time. First, the dust must be flammable; the dust of incombustibles cannot explode; the second condition is that there is an oxidant, such as air; and the third condition is that there must be an ignition source to provide combustion. The heat source.

Experts remind that industrial dust is far away from the public, but some dust produced in daily life also needs attention. For example, flour, cocoa powder, and cornmeal are defined as combustible dust. Once the flour has become very fine dust flying in the air, each particle can have full contact with the air, in the face of an open flame may ignite and may explode. However, the frequency of dust explosions in daily life is relatively low. However, it is still necessary not to scatter these dusts. If you accidentally spill flour, cocoa powder, and sticks, you must first turn off all the fire sources and immediately open the window. ventilation. At the same time, the public should pay special attention when storing flour, cocoa, and sticks, and it is best not to place them in places that are easily exposed to open flames.

German prevention of dust blasts

Dust explosion is a safety hazard in many industrial fields. In order to help safety assessment agencies and companies efficiently investigate hidden dangers, Germany has established an on-line database of dust parameters related to safety production for the first time at the end of 2012 for free use by relevant institutions and enterprises throughout the country.

According to German media reports, even in developed regions in Europe and America, many dust explosions of different sizes occur each year. Between 1980 and 2005 , there were records of dust explosions in the United States that caused more than 100 deaths and more than 700 injuries.

In order to clarify the complex data on dust explosions, the German Federal Research Institute for Materials Research and Auditors compiled and published in 2012 , based on experiments and assessments of more than 8,000 sets of data on a total of 108 industrial dusts in the sugar, metal, coal, and plastics industries. Dust parameters online database. It can be used to find out the minimum energy value, ignition temperature, initiation minimum threshold value and explosion pressure and other parameters required for ignition of various dusts in many specific situations. Using this database, safety assessment agencies and accident investigation agencies can quickly analyze key processes of dust burning and explosion.

The information in this article comes from the Internet and was reorganized and edited by China Rescue Equipment Network.