Numerical Simulation Of Using Lignite Coal As Fuel For600MW Bitumite-fired Boiler

With the national economic development, the non-renewable resourcesrepresented by oil, coal and natural gas have been increasingly depleted. Thisproblem seriously restricts the survival and development of mankind. Comparingwith other country, a lot of coal is used in our country every year. About half of thecoal is used to generate electricity in our country. The supply of high quality coal istensioned. So how to improve the consumption of inferior coal and reducedependence on the high quality coal has become an urgent problem. Combining withthe renovation project of bituminous coal boiler changing to burn lignite on600MWultra-supercritical wall-type boiler, in this thesis I will study the combustion conditionin the furnace under different loads using numerical calculation when burning lignite.And then the combustion condition will studied in the furnace under different loadsusing numerical calculation when burning the designed bituminous. The differenceswill be compared and analyzed between the two cases. Combining with field test, thechanging laws of the thermal efficiency of the boiler with lignite blending ratio willbe analyzed. The economical efficiency will be studied when burning mixed-ligniteof this furnace. Through the comparison of the design parameters and the testparameters, the accuracy of the numerical calculation results can be proved.Through the numerical simulation result and the test result, the results will belearned below. When burning the lignite the temperature level of the furnacedecreases obviously and the temperature of the outlet of the furnace decreases, too.However the exhaust temperature of the boiler rises obviously. When the boiler onlyburning lignite coal, the rate of the primary air will be increased. This leads tovariation of the components in the furnace. This also leads to reduce the burnout rateof pulverized coal. With the increasing of the rate of lignite blending, the thermalefficiency of the boiler significantly reduces. When only burning lignite, the thermal efficiency of the boiler reaches the minimum. The heat loss of the flue-gas and themechanical incomplete combustion heat loss increase more obviously. This requiresto re-organize the structure of the combustion furnace to solve it. The coal prices atthe time of test will be used to compute the economic efficiency of burning mixedlignite. Through analyzing the economic efficiency of burning mixed lignite, onlyburning lignite coal the economic efficiency is the best. Compared with the thermaldesign parameters and the test results the accuracy of the numerical results will beimproved.