Issues related to flue gas system resistance and induced draft fans
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Our plant’s circulating fluidized bed boilers have had their flue dust removal systems modified, which increased the resistance by around 600 Pa. After one day of operation, the negative pressure in the boiler furnace could no longer be maintained. What are the main reasons for this? I suspect that the output of the exhaust fan is not sufficient. If indeed the fan’s output is inadequate, is it necessary to replace it?
It’s also possible that the ash removal system focuses only on ash removal and ignores the flow capacity; it seems that more attention should be paid to this aspect of the system, with the induced draft fan being a secondary consideration
The reasons for the increased resistance may include: 1. Dust accumulation and coking. 2. For the position of the baffles, it is best to check on-site to ensure that none of the baffles on the flue gas side are not fully open. 3. Flue gas ash content. 4. An increase in the primary air flow of the boiler leads to an increase in the amount of fly ash. 5. The most suspicious part is still the ash removal system, after all, it has just been renovated. Check if there is a problem, and see if the differential pressure has increased since startup. 6. Influence of exhaust gas temperature: An increase in exhaust gas temperature reduces the output of the induced draft fan.
Improving the dust removal system increases resistance losses, resulting in the boiler being unable to operate under negative pressure. First, check whether there are any changes in the system during the inspection and renovation process, such as any changes in the position of the flue dampers. Next, conduct a detailed calculation of the system’s loss, to determine whether the fan’s capacity is sufficient. The amounts of other fly ash and the flue gas temperature should remain unchanged, as these factors do not increase throughout the entire operation process!
I’m not very familiar with the situation on site. \"The flue dust removal system was modified, which increased its resistance by about 600 Pa.\" Was it the fly ash separation device that was modified? What form is it adopted?