Stoker Combustion

The Energy Institute has experience in determining the combustion behavior of coals and blends on stokers. Fuels tested include bituminous coal, anthracite, briquettes, and agricultural plastics.

Examples of three types of testing are described. In one program, The Energy Institute evaluated the combustion behavior and determine the economics of firing various blends of anthracite with the bituminous coals used at the Jennison and Hickling generating stations of the New York State Electric & Gas Company (NYSEG). Results of the program include:

• Blends of anthracite and bituminous coals displayed better combustion behavior in a bench-scale stoker simulator than the bituminous coals alone, due to reduced caking of the bed and enhanced air flow through the bed;
• Tempering the bed with water was more effective than manipulating the initial particle size distribution for decreasing the bulk density of the bed and improving combustion performance; and
• Partly as a result of this program, NYSEG burned blends of 10-15% anthracite by-products with bituminous coals at their Jennison Station.

The combustion performance and emissions generated during the combustion of agricultural waste plastics, which were densified into fuel nuggets, blended with coal were evaluated for the National Watermelon Promotion Board. The waste plastics were obtained from three locations around the country with different soil conditions, growing seasons, and pesticide/herbicide usage. The flue gas from the stoker simulator was sampled and analyzed, per EPA test protocol, for CO₂, CO, SO₂, NO_x, O₂, polycyclic aromatic hydrocarbons (PAHs), and polychlorinated dibenzodioxins and polychlorinated dibenzofurans (PCDD/Fs) toxic equivalent emissions. Results from the testing include:

• There were many non-detects for PAH and PCDD/Fs when performing baseline coal tests;
• Complex PAHs and dioxin TEQ emissions were elevated when burning two of the three plastics; and
• The PAH emissions were quite elevated with one plastic.

The Energy Institute performed a series of combustion tests firing three different briquettes in the stoker simulator for the University of Kentucky Center for Applied Energy Research. The objectives were to note the combustion stability and emissions when firing the briquettes, which were produced from a parent coal with two produced using additives for SO2 and NOx reduction. The testing documented combustion stability and emissions of CO, SO₂, and NO_x.