Study And Numerical Simulation Of300MW Blast Furnace Gas And Coal Blended Combustion Boiler

Blast furnace gas (BFG) that a low heat value fuel, its utilization ratio is low. There will be great economic benefits if it was utilized effectively. BFG combined with pulverized coal in boiler is an effective way. But the boiler is easy to excess temperature and hard to burn through. For a300MW blast furnace gas and pulverized coal blended combustion boiler, in this paper, simulations of the different blending rates and different loads conditions by FLUENT and thermodynamic calculations of BFG blending rates10%,20%and30%conditions were used to study the mixed combustion characteristics of BFG and pulverized coal. In addition, economical efficiency analyses of boiler were calculated. For the results of numerical simulation, the temperature level in boiler decline obviously when BFG blended in boiler. The temperature decline as the adding rate increase, but tendency is slowing. After blending BFG the gas output increased as well as the gas speed of boiler export. So the actual time that pulverized coal stay in furnace become shorten which make coal complete combustion difficult. Also, NO emission decrease with more mixed BFG. For analyses of thermodynamic calculations, academic combustion temperature decreases with increase of BFG blending rate. For example, when the blending rate is30%its academic combustion temperature reduces to1635℃which limited BFG blending rate. After blending BFG, the endothermic characters of boiler heating surfaces changed, radiation heat absorption capacity in boiler reduced and convection heat absorption capacity of superheaters and reheaters increased. Also, the gas temperatures of boiler export and convection heating surfaces increased. In final, exhaust gas temperature increased and boiler efficiency decreased. The generating cost of BFG and pulverized coal blended combustion boiler decreased with increase of blending rate. Without BFG cost, the generating cost of BFG blending rates10%,20%and30%conditions were lower RMB0.0223yuan/kWh,0.0408yuan/kWh,0.0585yuan/kWh.