The effect of dust removal equipment is to reduce the dust emission concentration, protect the atmospheric environment. Asphalt concrete mixing equipment with dust collector has a primary flow and secondary filter. General level filter is the only place for small mixing equipment; Large mixing equipment to achieve environmental protection requirement, using two levels of dust removal, the level is usually done by gravity and centrifugal separator, the second stage often use wet dust removal or bag dust removal. The wet dust removal back dust capacity of up to 400 mg/m3, the back of bag-type dust collector dust quantity can reach 50 mg/m3.
Early asphalt mixing equipment is dry type cyclone to filter out dust.
Because of the dry type cyclone dust removal can only remove large particles (> 5 microns) dust, but seldom from the content of large particle of dust in the dust. A large amount of emissions is less than 5 microns fine dust. With the improvement of environment protection and the dust removal technology development, bitumen mixture equipments only take secondary dedusting can achieve emissions requirements. Secondary dedusting way has a wet dust removal and two kinds of bag-type dust collector, adopt different ways of dust removal according to different requirements.
Level of dust collector cyclone, and the two gravity filter. Cyclone dust extractor has simple structure, and its dust collecting device for cylinder type, cut air to enter, the dust under the action of centrifugal force is separated. Cyclone to collect dust particle size of more than 5 microns, the dust removal efficiency is commonly 5% ~ 85%.
Use gravity precipitator is expansion tank to reduce air flow speed, large particles dust fall by gravity, capture more than 40 microns particles.
Bag filter is a highly efficient dust removal device, the use of organic or inorganic fiber fabrics made of filter bag, dust filter out from the flue gas, can capture size 0.3 microns above dust, dust removal efficiency can reach 95% ~ 99%. Dust concentration can be up to 50 mg/Nm3.
There is an air blowback bag filter, blower counter blowing and pulse injection three types. Air blow is to use the system of negative pressure and differential pressure of the atmosphere, make air into the bag for soot cleaning job. Due to the pressure difference is small, clear ash disturbing force is small, and therefore have to prolong the ashes of time, at the same time increase the filter area, so as to meet the needs of the dust, therefore the volume of air blow dust collector is generally larger. Pulse blowing dust is the use of high pressure air injection bag inside short time, make its jitter and cleaning the dust adhesion on the bag. Due to the injection time is short, and the injection force, adhesion on the cloth bag dust is easy to drop, short of blowing ash removal almost does not affect the filter's homework. Volume of pulse injection filter generally smaller, but need to configure the high pressure gas source and the pulse valve device, etc.
Asphalt concrete mixing equipment using bag filter by enclosure, baffle plate, filter bag, bag of skeleton, throat, tube plate, spray torch, pulse valve, differential pressure gauge, screw conveyor and controller, etc.
Bag filter, in the role of the suction fan, protecting gas into the box 1, under the baffle plate cutting block is separately flue gas flow, large particles from export 2, used as aggregate, from each of the filter bag dust gas lateral within 3 4 into filter bag, the filter bag screening, grille, impact, interception, diffusion and electrostatic attraction, the dust attached with a gap between the filter cloth, dust separation from flue gas. With the accumulation of dust on the filter bag, form a certain thickness of the dust layer, lower the permeability of the filter cloth, interfere with the normal work of the dust collector. So the bag filter in the process of work must often clear the dust on the filter bag in a timely manner. Remove dust with mechanical vibration and injection, injection mode and pulse of high pressure injection and blow different ways, such as atmosphere.
Air blow way: the controller control pulse valve timing interval to open the vent above the filter pocket, the filter bag produced inside and outside differential pressure, filter bag, shaking and vibration caused by the dust on the bag fell to the bottom, then through in the bottom of the screw conveyor sent outside the box. In order to ensure the filter bag filter effect, protecting gas and the purification of the filtered gas must be maintained between certain differential pressure, differential pressure gauge for this bag filter. Such as pressure difference is too large, it shows that filter bag dust is overmuch, filtration resistance is too large; Differential pressure is too small, it shows that filter bag has been damaged. Fan using suction arrangement in the chimney mouth, in order to avoid dust accelerated wear of the fan.
As the main component of bag filter bag work long time under the condition of high temperature, also because the sulfur content in fuel in the combustion process forming acid corrosion bag, so the bag must be able to heat resistance of acid. In addition, dust collection box rust is also very important. Fuels, such as sulfur, nitrogen element in the acidic content, in the process of combustion oxidation corrosion enclosure wall easily after into the dust collection box, so the requirement on the inner wall of the box body, daub coating or made of anti-corrosion materials. New type bag filter technology improves, more focused on how to improve the bag, the effect such as disturbance position change cloth and increase the pulse nozzle to volume, etc.