In the cement industry, coal grinding dust by bag filter has been widely used, but because of the development of coal grinding equipment, coal transportation has been cancelled by the fine powder separator, and bag filter instead, and coal mill bag filter is based on coal dust fire and explosion proof principle, and the bag dust collector. The combination of the successful development of the filtering mechanism. Coal dust in the process of conveying, grinding and dust removal process is the main risk of combustion, explosion. Therefore, fire prevention and explosion protection are the two main factors that must be considered in the design of pulverized coal mill system and dust collector. Coal powder machine specializing in the production of energy-saving equipment.
1 Characteristics of coal mill flue gas
Coal dust in the flue gas is pulverized coal, its concentration is large, the grain size is fine, and it is inflammable and explosive. In
1.1 some properties of coal powder
According to scientific research departments of coal testing, coal has the following characteristics: in
(1) the explosion limit of bituminous coal explosion limit concentration is 110 ~ 335g/m3, explosion limit concentration of 1500g/m3; Anthracite explosion limit concentration is 45 ~ 55g/m3, the explosion limit concentration is 1500 ~ 2000g/m3. In
(2) the particle size of coal dust explosion: the upper limit is 0.5 ~ 0.8mm, and the particle size is less than 75 m. In
(3) the ignition temperature of pulverized coal: 500 ~ 530 degrees C, self ignition temperature: 140 ~ 350.
(4) the coal volatile anthracite volatile: less than 10%, no danger of explosion; coal volatile >10%, the risk of explosion, the percentage of larger, more explosive. In
Only 1.2 of coal have the following three elements, it may be burning and explosion, one can not in
(1) a pulverized coal with a combustible substance;
(2) with oxygen;
(3) there is a light source.
1.3 dust concentration is low
The process of coal mill in the cement plant is that the coal mill exhaust gas flows through the coarse powder separator and then the fine powder separator, and the dust concentration is low, which is about 70g/m3. With the development and progress of technology, the removal of fine powder separator, with the dust of the flue gas through the coarse powder separator directly to the dust collector. At this time, the concentration of pulverized coal is increased to 300 ~ 700g/m3, and the pulverized coal in the dust collector space is in the range of explosion. And the concentration of pulverized coal is very small, large specific surface area, particle size 20%, the risk will be greater. Therefore, it is required to control the exhaust gas temperature of the bag filter dust collector in the following 90. Once the temperature over temperature, sound, light alarm, emergency shutdown system, stop running.
In addition, CO gas monitoring, alarm is also used for coal mill safe operation of a measure. Requires a complete set of cooling, filtering, drying and other devices, the need for strict management and maintenance. So CO automatic monitoring system is able to play the role of early warning. If the conditions permit, the coal mill system uses kiln exhaust gas as a heat source, its oxygen content in 6% ~ 10%, gas temperature between 300 to 340 degrees Celsius, so that the system operating in an inert atmosphere more secure.
In
(3) the use of fire extinguishers
Some cement plants in our country because of the capital and management and many other reasons, the pulverized coal mill system is simply equipped with a few foam fire extinguishers, and some even this can not be done, it is very undesirable. Fire prevention and explosion protection of pulverized coal mill system should be equipped with temperature warning device and CO2 automatic fire extinguishing device. When the concentration of CO2 in the air amounts to 30% ~ 40%, the combustion of the ordinary combustible material can be choked; 40% ~ 50%, can inhibit the explosion of gasoline vapor and other gases. For coal dust, CO2 content in 50% to suppress its explosion. The CO2 automatic fire extinguishing device is provided with a fixed CO2 supply source, and a fixed pipe which is connected with the connecting pipe is provided with a fixed pipe which is connected with the nozzle, and the CO2 fire extinguishing agent is released directly to the protected equipment.
The key tag: coal powder spraying machine, injection machine, coal mill, coal mill