【 Weak current College 】 dust explosion fire of fire---Power By 【 China power house network 】

I. preface
　　
Dust explosion is the industrial enterprises of fire prevention in important issues, China every year, dust explosion occurred and often belong to heavy, heavy fire. In the fire, the most serious is the aluminium dust explosion, other explosion more dust and coal powder, feed powder, plastic powder, titanium anhydride powder, powder, etc.
　　
According to the report of the United States insurance company, each recorded dust explosion caused by the loss of approximately $ 7500. Which in the case of food dust explosion of 30% in the case of plastic dust explosion of 20%. In modern production, the device constantly updated, on dust explosion control measures are continuously enhanced, but there is still a dust explosion. Mainly due to: produce explosive powder solid material handling capacity of a large number of, as the technology and technology of growing some new material, dust and combustible dust, combustion characteristics of the operating characteristics and other factors. Dust explosion not only prone to petroleum, chemical industry, metallurgy, machinery, textile and other industrial enterprises, the coal industry, food processing enterprises are more common.
　　
II. dust explosion potential fire hazard
　　
Dust explosion fire risks mainly by dust combustion characteristics and operating characteristics. Combustible dust, combustion of properties also have explosion characteristics, dust combustion depends largely on the degree of dryness dust and particle size size two factors, the dust is dry, the smaller the particle size, the more prone to combustion and explosion. For example, deposits in the heating surface dust, as high temperatures, over time will occur, and most prone to smoldering smoldering dust layer thickness of 10-20 mm, deposition of dust smoldering negligible even vibration can cause fire and explosion. Certain combustible dust deposition State with spontaneous combustion characteristics are due to certain substances in particle shatter State when in contact with air and oxygen adsorption on the scenario, the powder layer temperature rise, when heat cannot fully distributed, continue to rise in temperature can cause spontaneous combustion. Dust of spontaneous sexual depends not only on the powder layer thickness, airflow direction and wind, air temperature, but also with dust particle fineness and pore structure, inside and outside surface area, and other factors. Various impurities can dust of spontaneous greatly affected. For example, oily and greasy substances admixtures, can promote the dust of spontaneous combustion.
　　
Dust explosion depend enough dust floating or deposit-air mixture and sufficient energy sources of ignition are two necessary conditions.
　　
Typically, there are initial dust explosion at the plant and equipment space in two forms. Device for forming the explosive dust-air mixture exploded, tend to make deposits in floors, walls and a variety of architectural structures and technology equipment dust stirred and fluttering, resulting in a plant in the second, or even three times more plant explosion. Similarly, if the device within the dust leakage to the workshop, reached the explosion risk concentration, yuhuoyuan will also have before the device's dust explosion. In addition, based on dust combustion and explosion of analysis, the explosive dust depends to a great extent and dust exposure and combustion characteristics and energy sources. There are major sources of ignition Sparks, open flame, heating and hot objects, high-temperature surface, fiery space, friction heat, spontaneous, chemical reaction heat, heat rays focused role, burning heat, and so on.
　　
III. strategies for the prevention of dust explosion
　　
It goes without saying that the main dust explosion prevention measures should be excluded form explosive dust-air mixtures of possibility and eliminate the source of fire.
　　
1. Prevention of dust deposition and timely cleaning dust
　　
For processing powders of equipment or premises, to prevent leaks and the dust flying everywhere, and in particular should be easy to produce dust equipment isolation settings in a separate room, and a special protective cover and local exhaust hood or consider cleaning device. In addition, within a time limit to be deposited on plants in the corner, equipment, cables and pipes of dust. In General, this is a technical difficulty, not always able to resolve successfully. Clean-up must be wet dust, where there is no water wet dust, dust removal method should be used machinery, such as the statutory period of clear dust exhaust, maintain operating environment clean. Of course, from improved equipment and production processes, eliminate and reduce the spread of dust within the plant is the most fundamental measures.
　　
2. strengthen the management, eliminating dust explosion of ignition source
　　
From the foregoing analysis, dust explosion there are several sources of ignition, must be based on the operating environment of possible ignition sources type targeted prevention. For example, a flour mill in flourmills in mixed with metal or stone fragments, will play sparks and dust explosion, to this end, the net before treatment processes such as wheat should strengthen operations management, avoid can cause ignition source of metal and other hard objects mixed with grinding process, particular attention magnet failure problem.
　　
3. avoid equipment dust explosion
　　
For devices extremely easy to form an explosive mixture of dust-gas, in the device and in an inert medium, reducing the oxygen content is currently prevent equipment explosion the only reliable method. In this case, the dust-air mixtures in the oxygen content will reduce the propagation of flame not to. Inert media can take nitrogen, carbon dioxide, flue gas and the use of inert dilution to the necessary minimum oxygen content of air or other industrial emissions and inert dust, etc.
　　
Fittings, pipe and equipment of heating surface often combustion sources of ignition, the device's surface temperature is not permitted. The conditions, the device's surface temperature should be slightly lower than the smoldering temperature dust layer. Another Department, combustible dust in the crusher, crushing equipment, air ducts and other devices with stirring device, often out of sparks and detonated, therefore the above equipment parts must not generate sparks.
　　
IV. reduction of dust explosion damage of countermeasures
　　
PowderDust explosion destroyed forcing strong, harmfulness, in order to reduce fire losses, limit the expansion of fire, equipment or plant construction to reduce dust explosion damage.
　　
1. reduce dust explosion on the destructive effect of the production plant
　　
Practice has proved that the factory installed explosive dust-air mixtures in explosion can weaken the pressure of the widget is the loss of effective dust explosion prevention measures. Factory assembled easily thrown light protection structure including: installing window sash or general Windows, doors, double doors, skylights, with light insulation sheet steel, lead plates and asbestos cement roofs widget. In a single plant, if the wall is not possible to assemble the explosion-proof Widget, you can set using the roof venting. Easily thrown light weight roof structure generally lower than the allowed 120Mpa and per cubic metre of the vent area of not less than 0.03 square.
　　
2. reduce equipment explosion damage
　　
When the dust explosion occurred in the internal process equipment, in order to protect the device does not heavily damaged, you can use vacuum vent Assembly (explosion-proof membrane, valves, etc.) to reduce the explosion pressure. Explosion-proof membrane or other vacuum parts require more than the working pressure of 20-30% when the action. Using metal foil, kraft paper, linoleum, impregnated rubber asbestos plate, polyethylene film, citing the Lu as explosion-proof membrane material. Explosion-proof membrane, valid through the cross-sectional area, use the following simplified formula:
¡Ý 0.16 type: F-film area, m ­ 2 V-------device volume, 2 m.
To prevent dust-air explosive mixture when the device is damaged, you may use the blasting plate or blasting door as pressure-relief device, the device has been widely used in pressure is low or normal pressure of the designed under operation. Blasting or explosion doors has the advantage that can be slightly higher than the residual pressure of the atmosphere, or in respect of discharge hole automatically closes, blasting panels and doors available cattle blankets or other sealing material package posted its edge to achieve the purpose.