For purpose of grabbing the influence of coal blending ratio on the performance of supercritical monotube boilers,three schemes to improve the coal blending ratio were proposed by the field tests,and the boiler operating performance,combustion state and performance indexes of the three schemes were ex-plored.The results show that,the highest boiler efficiency under wide load becomes decreasing with the in-crease of coal blending ratio of A and D mills;and the load corresponding to the highest boiler efficiency gets increased.The likelihood of coking in the screen superheater and the final reheater at the test load is small for each mode.However,a risk of coking in the upper and middle heating surfaces of the furnace above a certain load will exist.At loads below 400 MW,the use of 50%lignite blending in B mill,40%blending in A and D,and 10%blending in C and F has a significant effect on reducing operating costs of the enterprise.In the load above 400 MW,in order to avoid any coking on the heating surface of the fur-nace outlet and affect the capacity of the unit,the scheme of mixing 50%lignite with B coal mill,30%with A and D coal mill and 15%with C and F coal mill can be adopted.
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