Combustion Tests of Beneficiated and Micronized Coal-Water Fuels: Use of Internal-Mix Atomizer and Rotary-Cup Burner

摘要

Combustion tests were conducted in an oil-designed 100-hp firetube boiler using a burner with an internal-mix atomizer to determine the effect of coal beneficiation and coal particle size-consist on combustion properties of coal-water fuels (CWF). Samples of Eastern Kentucky bituminous coal, beneficiated to ash levels of 2.5%, 7.8%, and 10.3%, were used to prepare CWF's containing approx. 90% (by weight) minus 75 microns (200 mesh), and 80 to 90% minus 19 microns (micronized). The viscosity of the micronized CWF increased significantly with shear rate. Combustion test results indicated that the use of the micronized CWF did not result in a significant improvement in either carbon conversion or boiler efficiency compared to the use of the CWF made with coal containing the same percent ash but having the coarser particle size-consist. It appears that atomization quality and the resultant CWF droplet size, and not the coal particle size, determine the rate of fuel burnout and the carbon conversion efficiency. On the other hand, increased levels of coal beneficiation resulted in improvement in the combustion of CWF's. A rotary-cup burner designed and fabricated in-house at PETC was also tested in the 100-hp firetube boiler with both 200-mesh CWF and micronized CWF. Results with both the 200-mesh CWF and the micronized CWF indicate that the rotary-cup burner performs as well as a commercial internal-mix atomizer while giving advantages of lower fuel pressure requirements at the burner, elimination of the need for high pressure atomizing air, and reduced burner erosion problems. (ERA citation 10:033185)