Coal mill explosion - proof problem sharingDate: 2019-07-12 Views:
The spontaneous combustion and explosion accidents of pulverized coal preparation system in cement production enterprises occur frequently, and the equipment and personal safety are seriously threatened.How to improve the flame-proof and explosion-proof ability of pulverized coal preparation system has become the focus of cement production enterprises' safety production.
1. Combustion characteristics of pulverized coal
(1) pulverized coal is a tiny particle of coal. Its surface area is much larger than that of the same amount of coal, and it is easier to oxidize and spontaneously ignite after contact with air than coal.
(2) when coal powder is suspended in the air and reaches a certain explosion limit, explosive mixture is formed.According to the determination of the coal department, the explosion limit of various coal dust is 45g/m3 at the lower limit and 2000g/m3 at the upper limit, which is quite large, and the explosion intensity is the highest at 300-400s /m3.Reach the limit of coal, even in closed space, such as coal warehouse as long as the encounter of open fire, will cause the explosion of combustion.
2. Explosion conditions of pulverized coal
Dust explosion is a kind of special combustion phenomenon, which also needs three conditions: combustible, combustion assistant and ignition source.
(1) the dust itself is combustible dust.Organic dusts such as flour, wood powder and chemical fiber dusts are combustible.Inorganic dust includes metallic dust and some mineral dust (e.g. coal,
And so on), are also combustible dust.
(2) dust is suspended in combustion supporting gas (such as air) and mixed to reach the explosion limit of dust concentration.Dust suspension in combustion supporting gas is due to crushing, grinding, transportation, ventilation and other mechanical effects.Dust with large particle size generally settles into dust with combustion capacity, and only dust with small particle size can be suspended in combustion supporting gas.
(3) there is enough ignition source to cause dust explosion.Dust has a small spontaneous ignition point and minimum ignition energy, as long as the outside energy exceeds the minimum ignition energy or temperature beyond its spontaneous ignition point
(most are between 400°C and 500°C).
When the above three conditions are satisfied at the same time, dust fire and explosion accidents may occur.
3. Safe operation
(1) power on
1. Before starting up the pulverized coal preparation system, the system shall be comprehensively checked to ensure that the production equipment and fire fighting facilities are in good condition, and the temperature and CO concentration at each measuring point are normal and qualified for starting up;
2. When the coal powder preparation system directly USES the kiln head or kiln tail waste gas as the drying heat source, stop the operation of the coal powder preparation system and close the hot air valve leading to the coal mill if the pre-decomposition system is used for blocking removal;
3. Before starting the coal mill, the dust removal system of the coal mill should be started.
1. When pulverizing bituminous coal, the temperature of the grinding gas should not exceed 260°C, and the temperature of the grinding gas, the coal silo, the inlet gas of the coal mill dust collector and the dust bucket should not exceed 70°C;
2. When grinding anthracite, the temperature of the grinding gas should not exceed 300°C, and the temperature of the grinding gas, the coal silo, the gas inlet of the coal mill dust collector and the dust bucket should not exceed 75°C;
3. The CO concentration in pulverized coal warehouse and coal mill dust collector shall not exceed 800ppm.
(2) requirements for patrol inspection:
1) regularly determine the route and do patrol inspection;In order to find and eliminate the hidden danger of air leakage and coal leakage in time;
2) if any abnormality is found in the equipment, process parameters and safety facilities of the coal mill system, the main operation of the coal mill should be reported immediately;
3) the surface of the equipment and pipes of the pulverized coal preparation system should be cleaned regularly to prevent dust accumulation;
4) the fire extinguishing device of pulverized coal preparation system should be checked frequently to prevent it from being put into use.
1. Dust separator, dust collector and conveying equipment should be emptied before stopping;
2. When the shutdown is planned for more than 3 days, the coal dust in the coal dust warehouse shall be emptied.When cannot discharge for some reason, measures such as bedding raw material powder should be taken inside the coal bunker.When the planned