Taking the project using semi-coke to replace coal as fuel in a circulating fluidized bed boiler in Hebei province,China as an example,the combustion system adopts the method of co-burning semi-coke and ash together,which solves the problems of large mechanical incomplete combustion loss and unstable material circulation after changing the fuels.The optimum mixing ratio of semi-coke to ash is 9∶1.The air distribution system adopts the methods of controlling the total air volume and reducing the primary air rate to solve the problem that semi-coke is difficult to ignite,and the optimal primary air ratio is determined as 55%.The heating surface at the tail of the boiler is increased to solve the problems of steam overheating and boiler efficiency declining caused by the large increase of fuel calorific value.The soot,SO2 and NOx emissions of the boiler after changing the fuels are reduced by 73%,94%and 55%,respectively compared with the original boiler,and the hourly fuel cost will reduce by 5.51%under the original boiler's rated power.
circulating fluidized bed boilersemi-cokecombustionair distributionheat transfer
NETL
NSTL
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