What is the reason for severe dust accumulation at the tail?
Thread Content
What is the reason for severe dust accumulation at the tail? Our plant’s 410-ton fluidized bed operated at low load throughout the trial operation period. After shutting down the furnace for inspection, it was found that there was severe ash accumulation from the furnace outlet to the cyclone separator outlet, including in the rear heating areas. In particular, the depth of ash accumulation at the separator outlet exceeded one meter. Is this due to too low wind speed during operation or an excessive amount of ash? If it’s due to other reasons, please advise, experts.
The 75t/h fluidized bed boiler that I was responsible for tuning also exhibited the same problem you mentioned – severe ash accumulation, especially in the heating surface section of the superheater at the outlet of the separator; the ash accumulation there was over half a meter thick (it was less in the 75t/h boiler). There are several possible reasons for this: 1. The flow cross-section of the flue gas at the outlet of the separator increases suddenly, which reduces the flow velocity of the gas. This makes it impossible for the gas to carry away the fly ash, so some of the fly ash inevitably accumulates in the dead zones within the flow, and this amount gradually increases； 2. The inclination angle of the horizontal section is designed to be gentle, allowing fly ash to accumulate to quite thick layers; it is therefore not possible to rely on gravity to prevent or reduce ash accumulation ； 3. When the ash accumulation reaches a certain thickness, on the horizontal flue near the vertical flue at the tail end, the thick layer of ash will, due to gravity, fall in large quantities and intermittently onto the heating surfaces inside the vertical flue. Since only a certain amount of fly ash can accumulate on the economizer, the impact is not significant ； However, when fly ash falls on the preheater (where flue gas flows inside the preheater tubes), it can easily block some of the flue gas flow tubes. As this accumulation increases, it eventually leads to problems such as insufficient output from the exhaust fan and increased wear on the air preheater.
This post was last edited by zgj2405 on 2010-7-30 23:19. Ash accumulation is related to factors such as boiler combustion, fuel, and flue gas flow velocity, and needs to be considered comprehensively. If other operating conditions cannot be changed, considering the use of an effective soot blower is an option. We can deal with the dust accumulation issue first, and then talk about other things.
It is possible that the furnace load is too low, resulting in flue gas volume and flow velocity not meeting the design requirements. Dust tends to settle and accumulate. Additionally, if the flue gas temperature is too low, it may result in excessive condensation water in the flue gas, facilitating dust accumulation.
It has something to do with the gas velocity; also, check whether there are any leaks in the system.
No special treatment is usually required, unless it is coal with strong adhesiveness； Once it reaches full load and the flue gas velocity increases, ash accumulation naturally decreases
What was said on the 2nd and 6th floors is completely correct. It is recommended that the poster install a boiler soot blower, as ash accumulation severely affects the boiler’s performance
Our company has encountered the same problem as well; it’s a good opportunity to learn from it, hehe