Circulating fluidized bed boilers have only 2% combustible content in their fly ash
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Dear fellow marine engineer, I recently encountered a circulating fluidized bed boiler of the DHFX120-1.5 model that uses 4800-kcal Mongolian coal as fuel. What puzzles me is the fact that the carbon content in its fly ash is only 2%, while the operating load is around 67%. Has anyone ever come across a stove like this? I find it amazing; maybe it’s just because I haven’t seen much.
Does anyone have any experience to share on this topic?
Looking at the other test results for the coal fed into the furnace, it seems that the ash content is relatively low.
The ash carbon content is 2.5%, and for coal, it is 16% in terms of ash content and 36% in terms of volatiles
It would be best to send a diagram of the DCS smoke and air handling system!
Is the load that low? What is the thermal efficiency?
I’ve never used this type of coal; 2% fly ash and residual carbon is indeed a bit high – I didn’t expect it to be so low. With a volatile matter content as high as 36%, it is already classified as lignite (such coal requires proper ventilation during storage, as it may catch fire on its own in the storage bins). Its ignition temperature and burnout temperature are both relatively low; the residual carbon in the fly ash is reduced when secondary air is introduced. It is estimated that the particle size characteristics of this coal are also good, and a larger furnace height also helps to control the residual carbon in the fly ash.