Combustion of briquettes and fuels pellets prepared from blends of biomass and fine coal

Test burns of two briquetted fuels and two pelletized-fuel samples were conducted in a stoker furnace at the East Kentucky Correctional Complex (EKCC) in December, 2008. Four formulations containing fine coal and biomass were tested during a two-day trial; two briquetted fuels produced by the Center for Applied Energy Research (CAER) and two extruded fuel pellets provided by Kela Energy, LLC. Biomass contents ranged from 10 to 17 wt% and included sawdust, sorghum, molasses, and weeds with the latter harvested from reclaimed surface mines and fallow fields located in the Appalachian coal field to demonstrate the potential for energy production from underutilized lands. One of the briquetted and one of the pelletized fuels were prepared from crushed samples of the EKCC stockpile coal permitting for direct comparison of the combustion, handling, and emission characteristics of the engineered fuels to the stoker coal from which they were made. A second briquetted sample was made from lower-quality decanter fines recovered from frothflotation and spiral circuits to demonstrate that an acceptable stoker fuel can be produced from a lower-cost feedstock. The second pelletized sample was prepared from a sample of the low-ash, low-sulfur Blue Gem coal and served to demonstrate the magnitude of reductions in emissions that are possible when a higher-quality feedstock is used. The two engineered fuels prepared from the EKCC stockpile coal exhibited reductions in NO_x ranging from 18% to 35% and reductions in SO2 ranging from 14% to 16% relative to the coal from which they were made. Briquettes prepared with the decanter fines exhibited reductions of 14% NO_x and 11% SO₂ while the pellets prepared with the high-quality Blue Gem fines exhibited reductions of 42% NOx and 39% SO₂. The tests demonstrated that biomass can be added to lower-cost coal fines to produce a premiumquality stoker fuel that behaves in an acceptable manner during feed, combustion, and ash removal while simultaneously providing significant emissions reductions. Importantly, it demonstrated an economical method for moving waste biomass into the energy markets at a potentially meaningful scale.