Numerical Simulation Of Biomass Gas Reburning In600MW Supercritical Coal-fired Boiler

The NOX produced during the coal combustion has greatly affected human bodies and the harmonious development of the society. To control NOX emission during coal combustion, many methods are employed, such as air staged combustion, low oxygen combustion, and fuel-staged combustion. With the advantages of small initial investment, low operation cost and good nitrogen removal effect, the reburning technology with biomass gas as the fuel is a promising NOx-control technology. The biomass gas reburning technology has combined energy and environment together. On one hand, with renewable biomass as the fuel, the severe energy situation can be alleviated to some extent. On the other hand, the reburning of biomass gas can reduce the emission of fuel NOX and SOX and make full use of its zero net CO2emission advantage. Therefore, the positive effect of the biomass energy on environment protection and pollution control can be realized.This thesis has illustrated the research background, significance and status quo of the reburning technology, analyzed the important practical significance of the biomass gas reburning technology, and described the formation mechanism, control mechanism and related mathematical models of NOX in reburning boiler. Furthermore, the mathematical models relevant to reburing process are also summarized. Basing on these models, a full-size three dimensional numerical simulation of reburing processing using biomass gasification in coal-fired boilers has been done. A reasonable geometry and mathematical model are established basing on a600MW swirl-opposed boiler of coal combustion. The impact of biomass (rice straw gas, straw gas, corn stalk gas) type, the proportion of reburing biomass gas, and the reburning nozzle position on boiler operation and NOX emission characteristics are studied using FLUENT6.3software. The results show that when the boiler’s load is constant, the excess air coefficient of furnace outlet is1.14, and the excess air coefficient of reburning area is0.8, the denitrification effect of wheat straw gas is the best, and when the reburing ratio is15%, the denitrification effect of which can reach43%; furthermore, the denitrification effect of the other three biomass gases are efficiency, when the ratio of reburning biomass gas is15%. The reburning spout has a better denitrification effect when it lies in the front or rear wall than in the left or right wall. Variation and distribution of each physical parameters during the biomass gas rebuming process in the600MW supercritical coal-fired boiler were obtained through numerical simulation, and will be provided as reliable reference source for biomass gas reburnning in large capacity supercritical or ultra-supercritical coal-fired boilers.