Research On Anthracite Changing To Burn Bituminous Coal In A 600MWe Unit Down-Fired Boiler

In order to reduce the cost of purchasing coal and pollutant emission and increase economy,a power plant of 600 MWe unit down-fired boiler would be burned from anthracite to a Southwest bituminous coal.Because the boiler is designed and manufactured according to the specific coal,once the coal is changed,it is necessary to carry out feasibility study,formulate a safe transformation plan and evaluate the effect of the transformation.In this paper,firstly,the furnace outlet gas temperature was caculated by the checking thermal calculation using the original coal and then compare the temperature with the designed value to check the accuracy of the thermal calculation.On this basis,the thermal calculation of HT bituminous coal was carried out.The excess air ratio was 1.15,the exhaust gas temperature was 130℃,and the primary air rate was 20%.By gradually adjusting the area of the refractory belt to keep the furnace outlet gas temperature when burning the bituminous coal was the same as before.The Fluent software was used to simulate the above conditions at the same time,which could be used as the reference value of the thermal calculation.The results of thermal calculation and numerical simulation showed that when burning the HT bituminous coal,the area of refractory belt should be reduced to 400m2 so that the furnace outlet gas temperature was consistent with that of burning the design coal.According to the analysis of the above study,we have worked out the corresponding modification plan: reducing the area of the refractory belt,improving the boiler pulverizing system and burner.Boiler combustion experiment was carried out after the transformation,the results showed that the boiler could be ignited easily and burned stably,and the thermal efficiency could be improved by about 2%,NOx was relatively low,which greatly reduced the cost of desulfurization and denitrification,improving power generation profit,basically reaching the goal of burning bituminous coal;However,due to the low ash melting point of HT coal,the phenomenon of coking existed in the refractory belt and the large platen superheater.And the convection heating area of ash was serious,so that the reheater desuperheating water consumption was relatively large.To sum up,through the transformation of the boiler burning bituminous coal,it can improve the boiler efficiency,reduce the cost of desulfurization and denitrification and improve the power plant economy.Although there are some problems of ash deposition to be further improved,it does not affect the normal operation of the boiler.