Georgetown University Atmospheric Fluidized Bed. Report on Boiler Thermal-Efficiency Test

摘要

The thermal efficiency of the Georgetown University atmospheric fluidized bed boiler is discussed. Based on the results of the tests, conclusions pertaining to the goal of improving this efficiency will be made. The predicted design efficiency base was 82.5% (which includes the customary 1% manufacturer's margin) at 100% load. However, it should be recognized that the divergence of the test parameters from those of the design base contribute to the disparity. A conservative conversion of the calculated test efficiency to the design base conditions resulted in an efficiency of 79.8% at 100% load, which is 2.7% below the predicted 82.5%. The short fall in efficiency is attributed to several factors, e.g., test coal analysis and sizing, test limestone characteristics and control of limestone feed, and high rate of recycled solids. Improvements in these three areas should significantly increase the unit efficiency. Recommendations are as follows: the coal specification should be revised to provide a tighter size distribution, that has a limited fines content of 20% less than 1/4 inch; a limestone that has a better reactivity and a lower attrition rate should be used; the test procedure could be revised to maintain constant or automatic limestone feedrate; and the solids recirculation rate should be reduced. These actions should have the effect of increasing the overall efficiency by increasing both fuel burn-up and limestone utilization to the levels attained in pilot plant tests, and by lowering the average stack gas temperature. (ERA citation 07:054788)