Explosion-proof dust collector for medium speed coal mill bagDate: 2019-07-04 Views:
I. conditions of explosion
1. Temperature of pulverized coal
Different types of detonation have different ignition temperatures, but the finer pulverized coal, due to the increase of specific surface area, the explosion temperature is much lower than its ignition point.
2, the volatile content of coal
The combustible gas produced by pulverized coal when heated is prior to coke combustion.
Under the same conditions, the higher the fraction, the more violent the explosion.
3, the concentration of pulverized coal
Only when the concentration of pulverized coal in the air reaches a certain level can an explosion occur. The lower limit of the concentration of pulverized coal and air mixture is 20~30g/m cubed and the upper limit is 2000~7000g/m cubed.
There was no explosion risk beyond the two limits.
4. Particle size of pulverized coal
The finer the pulverized coal, the more likely it is to explode.
5. Ash and water content of pulverized coal
The higher the ash content in pulverized coal, the weaker the explosive content.
The more water there is, the less likely it is to explode.
(1) coal accumulation spontaneous combustion
(2) Mars is included in the system
(3) in the system pulverized coal particles and tube wall, box collision, generating electrostatic sparks.
II. Explosion protection measures
1. Explosion-proof design of process system
(1) process pipeline
Avoid laying pipes horizontally.
In general, the pipe inclination shall be at least 70° in the ascending pipe and 45° in the descending pipe (25° ~ 30° in the stationary coal accumulation Angle). The pipe shall be smooth.
Gate valves in the air inlet duct shall be in pneumatic form.
(2) bag dust collector temperature
The coal mill bag dust collector has strict restrictions on the inlet air temperature, not only to prevent excessive temperature caused by coal combustion and explosion, but also to prevent low temperature caused by condensation, the appropriate use temperature range is 55 ~ 75℃.
When the temperature of the inlet is too high, the temperature of the outlet should be appropriately reduced, and when the temperature of the inlet is too low, the temperature of the outlet should be appropriately raised.
(3) technological layout
Preheater exhaust gas should be used as a hot gas source if possible.
The exhaust gas of the preheater has very low oxygen content, usually 8% ~ 10%. In this inert atmosphere, the coal will not burn.
If the pulverized coal preparation system is a dual fan system, when the main fan stops and the dust removal fan runs, the heat engine can directly enter the coal mill dust collector by connecting the pipe short circuit, making the dust collector temperature rise quickly beyond the warning temperature.
In order to avoid hot air short circuit into the dust collector, the main fan and dust fan must be linked together, so that the dust fan can not operate alone.
(4) reasonable design of the air volume of the bag dust collector
Before selecting the coal grinding bag dust collector, the air volume of the treatment should be calculated strictly, and the air volume of the dust collector may be increased due to factors such as production increase, so that the air volume of the dust collector can fully meet the needs of the system, and avoid increasing the resistance of the equipment due to exceeding the treatment capacity, and causing ash accumulation due to insufficient dust cleaning capacity.
2. Explosion-proof design of dust remover
(1) anti-static filter bag
Anti-static filter bag is adopted, and its friction potential is lower than that of general filter material.
Anti-static filter material can be divided into: woven conductive yarn filter material, carbon fiber blended filter material, stainless steel fiber blended filter material.
In addition, according to the post-treatment mode can be divided into: common type, oil-proof and waterproof type, common film covered type.
Because the coal mill system operation rate is relatively low, often on and off, especially sometimes the raw coal moisture is high, easy to cause smoke condensation, so it is recommended to use oil-proof and water-proof or film-coated anti-static filter material.
(2) ontology design
A dust baffle board is installed in the dust collector to eliminate all the dust accumulation surfaces inside the dust collector and inhibit the spontaneous combustion of pulverized coal.
The running Angle of the gray hopper is more than 70°. In order to prevent ash accumulation due to too small valley Angle between the walls of the two gray buckets, two adjacent side plates are added with sliding material plate to increase the valley Angle and eliminate coal dust deposition.
Attention should also be paid to ensure thorough ash cleaning in the design of filter bag length, bag spacing and ash cleaning system, so as to avoid excessive density between bags or long filter bags caused by blindly reducing the size of the equipment, so that the ash cleaning cannot be thorough, and the formation of ash accumulation on the surface of filter bags, or even between bags.
If negative pressure operation is adopted, the whole air tightness of dust collector should be ensured.
(3) the valve
Explosion-proof valve is mainly divided into three types: adjustable explosion-proof door with safety lock, heavy hammer explosion-proof door, explosion-proof diaphragm.
The adjustable explosion-proof door with the safety lock adjusts the pressure of the explosion-proof door by adjusting the safety lock.
The hammer type explosion-proof door can release pressure by adjusting the position of the hammer. The explosion-proof door can be used repeatedly after releasing pressure.
The explosion-proof diaphragm corresponds to different pressure release according to its material, size and treatment method, and shall be installed separately after the explosion and pressure relief.
The bag dust collector is equipped with explosion-proof doors according to its explosion-proof ventilation area and explosion-relief pressure. Under the circumstance of the same explosion-proof requirements, the above three types of explosion-proof doors can meet the explosion-proof requirements.
Automatic fire extinguishing device
Coal mill bag dust collector should configure corresponding automatic fire extinguishing device, once an explosion in the dust collector bag room, ash hopper CO ₂ and nitrogen injection in areas such as the fire extinguishing gas, to avoid greater losses.
5. Temperature measuring components
The dust bucket and air inlet pipe of coal grinding bag dust collector must be equipped with temperature measuring components, which can transmit temperature signal of air inlet and dust hopper to electric control cabinet or central control room.
And the upper and lower limits of alarm should be set, and should be connected with the automatic fire extinguishing system.
The central control room should be able to record the temperature and pressure curves of each part automatically and continuously, so as to analyze and summarize the production process parameters and find out the cause after the accident.
6. Dust bucket heating and vibration device
According to the climate and other conditions can choose the configuration of gray bucket electric heater, vibration motor and material level meter and other facilities.
In the northern cold region, the gray bucket electric heater is needed, when the gray bucket temperature is too low, prevent the coal in the shell wall condensation bond;
They don't have to be in the south.
Dust bucket dust discharging device such as double-layer pneumatic dust discharging valve, do not need to be equipped with vibration motor;
But if the selection of the feeder, it should be equipped with vibration motor, avoid dust bin wall awning.
In addition, when choosing blanking and ash conveying device, attention should be paid to avoid sparks caused by material friction during transportation. It is suggested to choose explosion-proof blanking device or flap valve.
7) enclosure grounding
The shell of coal mill bag dust collector should be grounded to eliminate electrostatic spark.
III Operation and maintenance
1. Before stopping the machine, a thorough ash cleaning operation must be carried out to remove dust from the surface of the filter bag, and the machine can stop after the dust is discharged by the dust bucket.
2. Reasonable maintenance procedures and records should be made to ensure the stable and reliable operation of explosion-proof valve and discharging device of dust collector.
Once a fault is found in the feeder, it should be repaired imme