Fluidized-Bed Combustion-Industrial Application Demonstration Projects. Battelle's Multisolid Fluidized-Bed Combustion Process, End-of-Phase Final Report

摘要

Successful operation of the Subscale Experimental Unit System has been demonstrated; performance was comparable to that of the 6-inch unit (one-tenth scale), indicating that scale-up problems should be minimal. Combustion of as-received wet lump coal (e.g., 1-1/4 in. top size) has been successfully demonstrated. Combustion performance was independent of feed location; accordingly, feeding from above the dense bed is preferred because of relative simplicity of the feeding system. Comparable combustion efficiency and sulfur retention were obtained using either tan silica pebbles or hematite ore as the dense bed material. Tan silica pebbles are preferred from a cost and availability standpoint. Limestone needs to be well distributed in the dense bed to ensure effective sulfur retention. Excellent sulfur removal and limestone utilization can be achieved in the MSFBC system. Effective freeboard height was found to be one of the most important process variables affecting sulfur retention. Sulfur retention decreases with increasing limestone particle size, but is not significantly dependent on coal size, dense bed height, bed type, or excess air. Good combustion efficiency (up to 98 percent) has been demonstrated for both lump and crushed coals. Carbon recycle in the sand circulation stream and/or the flyash reinjection stream is essential to achievement of such a high overall combustion efficiency. The heat transfer coefficient for the steam tubes located in the entrained bed region ranged from 10 to 16 Btu/ft exp 2 -hr-F (lower-than-expected). Appreciable metal wastage on boiler tubes in the entrained bed zone was observed for the sections not parallel to the flow direction. (ERA citation 05:008996)