GDM coal-fired boiler pulse bag filter is a new type of pulse bag filter after years of research and industrial application. The filter is a kind of unit combined-type dedusting equipment, with the characteristics of good ability to handle air volume, high filtration velocity, good deashing effect, high dedusting efficiency, reliable operation, convenient for maintenance, small occupied area, modular production and stable quality. It has been widely used for flue gas dust removal and material recycling, dust control of boiler, furnace, waste incineration in the industries such as electric power, metallurgy, building materials and chemical industry.

  • Operating Principle

Dusty gas enters into each unit ash hopper from the draft. Under the guidance of ash hopper diversion system, larger dust particles directly fall into the ash hopper, and the rest of dust enters in the filtering area of the middle box together with airflow. After filtering, clean gas passes through the filter bag, and is eliminated through the upper box, lift valve and exhaust duct. In the filtering process, when dust accumulation reaches a certain amount on the surface of the filter bag, the deashing control device turns off the lift valve according to the set procedure, opens the electromagnetic pulse valve for injection and shakes off dust on the filter bag. Dust falling into the hopper is eliminated through the discharge valve.

This series of filters is equipped with the bypass gas duct. When the boiler (or incinerator) starts up, the bypass gas duct is opened, in case that fuel oil for ignition cannot be combusted sufficiently. If oil adheres to the filter bag, the filter bag will burn up in the condition of open flame. When an accident happens to the boiler, and the temperature of exhaust gas exceeds the allowable temperature of the filter bag, the bypass is opened.

This series of filters is equipped with the leak detection device, composed of multiple probes (each per chamber) and a turbidity meter. Check whether the filter bag is leaked according to the turbidity of soot; at the same time, an air cannon is set up in the ash hopper.

  • Basic Structure

GDM boiler pulse bag filter is composed of box, filter bag assembly, guiding device, pulse injection system, ash discharge system, control system and offline protection system:

«Filter bag assembly: The connection design of the framework of filter bag, bag and bag hanging tube sheet adopts self-locking device, easy to install and change, effectively prolonging the service life of the filter bag. There are three specifications of the filter bag, i.e. Φ130 x245mm, Φ130x6000mm and Φ 160x6000mm, made of PPS needled felt (imported PPS/PPS504CS17, waterproof and oil-proof processing).

«Guiding device: The filter adopts the international advanced air intake mode, and unique exhaust gas distribution device is designed, for the purpose of distributing dusty gas and separating larger dust particles, to prevent dusty gas washing the filter bag, to further improve the efficiency of the dedusting device, to prolong the service life of the filter bag.

«Pulse injection system: The injection system consists of injection box, electromagnetic pulse, $-shaped valve, pressure-bearing connector, nozzle pipe, support, etc. All HGMD filters with the specifications of below 65 have a compressed air nozzle pipe. In the runtime, the general setting is to remove ash on a row of filter bags by pulse air injection every 10 seconds.

«Ash discharge system: The system is composed of an electric vibrator (or air cannon), electric heater, indicating gauge of hopper shaking position, etc. The electric vibrator (or air cannon) can ensure that ash has a good liquidity.

«Control system: The system consists of a pulse injection controller, computer control cabinet, thermal resistance thermometer and static pressure measuring point.

«Offline protection system: The system is composed of bypass, emergency water spray system, differential pressure device, level indicator, device of detecting temperature level and pressure, pulse controller, device of filter bag leak detection, etc. When the flue gas temperature is too high, the device of filter bag leak detection composed of boiler is used, so that an alarm can be given timely when the filter bag is damaged. In re-ignition, water is sprayed for cooling, to avoid burning out the filter bag. The purification chamber is equipped with differential pressure level, etc. This is because when the ignition and under-load of a large-tonnage boiler need spraying fuel boiler oil, a large amount of oil-containing flue gas is produced and directly enters into the filter, leading to hardening the cloth layer of the filter bag. At this time, the increase of system resistance affects the normal operation, so the system adds the bypass pipe to effectively protect the filter bag.

«The box boy consists of the upper box (wind purification chamber), the middle box (filtration chamber), the lower box (ash hopper), flue gas distributor, tube sheet, platforms, escalators, landing leg, air inlet, air outlet, ash outlet, thermal insulation, color plate, etc.

  • Technical Measures

Powder spraying equipment

Before boiler ignition and fuel oil combustion, measures of power spraying and precoat should be adopted so as to prevent the filter bag bonding with soot, including ash storage tank, filter on the warehouse top, feeder, ash-gathering draught fan, etc.

Bypass device

Under abnormal conditions of boiler ignition, tube explosion, too high or low soot temperature, the bypass gas duct is used, and the bag filter should be protected through separation. In the normal operation of the boiler, the bypass gas duct is closed.

Measures of water spray for cooling 

A temperature sensor, which is installed in the exhaust gas outlet of the boiler and at the inlet of the filter, is detected by the PLC, displaying the analytical judgment and treatment. 2-3 groups of water spray atomization nozzles are installed at the outlet gas duct of the boiler. In the normal operation of the boiler, a trace of compressed gas is required to enter into the nozzle through the bypass pipe, to avoid blocking the nozzle.

Thermal insulation of the dedusting system

Before thermal insulation of air intake tube and the filter box of this dedusting series, the electric hot plate should be set up on the outer wall of the ash hopper for heating.

Automatic detection and control of the dedusting system

☆Temperature detection: A temperature sensor is set up in the outlet of air preheater, at the inlet and outlet of the filter, ash hopper of the filter and induced air outlet device, and it can transfer data remotely. When the temperature of the filter is too high or too low, or the temperature of the ash hopper is too high, the system gives a sound-light alarm and the bypass is automatically switched.

☆Differential pressure detection: The system gives an alarm when pressure at the outlet and inlet of the filter and of air bag display abnormally.

☆Flow detection: The flow measuring device should be set up at the outlet of the filter.

☆Display of ash hopper material level: The high-low material level indicator should be set up in the ash hopper, giving an alarm when abnormal.

Selection of filtration material of the filter

Filtration material is the core of the normal operation of the dedusting system. Amongst a variety of filter materials, except for weak oxidation resistance, PPS filter material has superior properties, suitable for gathering flue gas of the boiler, and has been widely applied in various types of coal-gas-fuel-based boilers. Its characteristics are as follows:

☆It adopts a progressive structure, 1D+2.2DPPs mixed material is used for the dust-falling side, and 2.2D or 7.8D material is used for the other side, not only improving the filtering precision, but reducing differential pressure.

☆It has high permeability. Under the condition of ensuring discharge precision, the filtration velocity can reach 1.5m/min, generally, 0.9-1.2m/min.

☆PTFE12 material is used for special processing, so as to improve temperature resistance and oxidation resistance.