One-dimensional model of coal gangue combustion in circulating flu-idized bed boiler

In order to study the combustion performance of coal gangue in circulating fluidized bed boiler,a one-dimen- sional model of coal gangue combustion process was established to predict the residence carbon in fly ash and bottom slag. A set of mass conservation equations,momentum conservation equations and species mass conservation equations are calculated in a cell model along the height dimension of active furnace area and the results of one-dimension distri- bution of coal gangue combustion parameters along the height are obtained. Unlike other combustion models,this model contains three periods including gas-solid flowing,mass transferring in porous media and chemical reactions. In addi- tion,the model couples the one-dimension model of particle residence time in CFB boiler which simulates the internal circulating behavior. The calculating results include the key controlling factor of coal gangue combustion rate,and the relationship among the residence carbon of fly ash and bottom slag,the physical parameters of coal gangue and the boiler operation parameters. By data processing and analyzing the results,some conclusions are made:the controlling factor of combustion is the grieshoch mass transfer process. The following operating conditions shall improve the com- bustion efficiency and decrease the residual carbon fraction:putting into larger porosity coal gangue,increasing the boiler maximum continuous rating,keeping the boiler wind speed as 7 m / s,and maintaining the diameters of particle as 100-1 000 μm.