Non-steady heat transfer analysis of poisonous solid waste combustion in circulating fluidized boiler

Incineration is the comparatively ideal way to dispose of poisonous solid waste (PSW). Using basic theory and methods of combustion, the physical and mathematical models, based on circulating fluidized boiler (CFB), are setup to study and discover the mechanism of PSW combustion. The results show that the steady temperature in the center of PSW lump is closely related to that of the flow in the heat exchange boundary while considering the porous features and the non-steady temperature ascending in CFB. Under the condition of high temperature flow heat exchange, the temperature inner the lump can reach that of the flow. And the more the exchange planes are, the higher the steady temperature inner lump is. The shape of lump has serious influence on the temperature ascending in CFB. At the save characteristic size (CS) or L=V/F, the temperature ascending of ball lump is the fastest, the cylinder the second, and the rectangular the slowest. With the increasing of CS, the time of the temperature reaching steady in lump will be obviously longer. Especially, the steady time increment is larger while CS is more than 10. The larger CS is, the lower the temperature reaching steady is, which, at the same time, is not appropriate to the precipitation of volatile matter and burnout of lump. It is concluded that, if making the PSW lump temperature (reaching 1073 K) ascent fastest during heat exchange in CFB, the shape of lump should be ball alike. The CS of lump should be small as soon as possible and the lump should be flipped continually to approve the lump in heating by high temperature airflow and burning out finally.