The core causes of dust collector filter bag burnout can be divided into five categories: excessive high temperature, open flame ignition, dust spontaneous combustion,
electrostatic sparks, and operation and maintenance negligence, and there are significant differences in the specific inducing factors under different working conditions.
Direct Over-Temperature Burnout Caused by High-Temperature Flue Gas
Filter bag materials have a clear temperature resistance upper limit (e.g., 130℃ for polyester, 190℃ for PPS filter bags, 260℃ for PTFE filter bags). When the flue gas
temperature exceeds this limit, the fibers will directly carbonize, melt or even combust.
Common causes: Improper fuel switching of the boiler or sudden load surge leads to a sharp rise in exhaust gas temperature; fouling and clogging of the economizer/
air preheater reduces the heat exchange efficiency by more than 40%, allowing high-temperature flue gas to directly enter the dust collector without being cooled.
Special scenario: Newly replaced filter bags are not pre-coated with dust, resulting in an excessively thin initial dust layer on the surface. The high-temperature airflow
directly scours the filter bags, which can easily burn out holes.
Scorching by Open-Flame Sparks Entrained in Flue Gas
This is the most common cause of filter bag burning in scenarios such as biomass boilers and metallurgical kilns.
Unburned glowing carbon particles and high-temperature sparks directly enter the dust collection box along with the flue gas, instantly burning irregular round holes up
on contact with the filter bags.
If there is a dust layer of a certain thickness on the surface of the filter bag, the sparks will not directly burn through the filter bag, only leaving dark scorch marks; howe
ver, when the number of sparks is large, the filter bag will still be ignited gradually.
Spontaneous Combustion of Accumulated Combustible Dust
When the flue gas contains combustible dust such as coal powder, aluminum powder and biomass fibers, spontaneous combustion will occur once the accumulation me
ets certain conditions.
When the thickness of dust accumulated on the filter bag surface exceeds 5mm, the ambient temperature is above 80℃, and the oxygen concentration is above 15%,
the dust will oxidize slowly and accumulate heat. When the temperature reaches the ignition point (e.g., 250℃ for wood powder, 350℃ for coal powder), spontaneous
combustion takes place, burning out the filter bag from the inside.
Excessive dust accumulation and bridging clogging in the ash hopper lead to poor heat dissipation and continuous rise of local temperature. The high temperature is
conducted to the filter bag and will also cause burnout.
Ignition by Static Electric Sparks
High-speed friction between dry dust and filter bags generates a large amount of static electricity. If the static electricity cannot be released in time, the formed sparks
are sufficient to ignite the combustible dust.
The electrostatic voltage on the surface of insulated filter bags such as polyester and polypropylene can reach over 10,000V. When the dust collector is poorly grounded
(grounding resistance ＞ 10Ω), the sparks generated by electrostatic discharge will directly detonate the dust within the explosive limit, subsequently burning out the filter
bags in a large area.
Omissions in Operation and Maintenance
Improper human management is an indirect cause of many filter bag burnout accidents:
The temperature monitoring sensor fails, and the over-temperature of flue gas cannot be detected in time, resulting in long-term operation of the filter bags in a high-
temperature environment.
The dust cleaning system malfunctions (e.g., pulse valve clogging), causing excessive dust accumulation on the filter bag surface and forming a spontaneous combustion
-prone environment.
When welding and hot work are carried out near the dust collector without isolation measures, sparks enter the filter bag area through ventilation openings and ignite
the residual dust.
The dust is not completely cleaned before the boiler is shut down, and the residual dust oxidizes slowly in the high-temperature box and spontaneously combusts during
unattended periods. Such accidents account for 40% of all fire accidents.
