Performance of a small scale boiler burner in the firing of fuel blends

Abstract

Power plants spend nearly 50 billion dollars a year on fuel cost. Presently coal accounts for over 75% of the electricity generated in this country. Due to increasingly harsh environmental regulations, the demand for low sulfur (S) coal has dramatically increased. This increase in demand is expected to cause the price of coal to rise. Such a senario has caused the utilities to explore the possibilities of supplementing coal with fuel alternatives such as the byproducts of process industries. The supplemental fuel for utilities located near feedlots (e.g. Northwest Texas) happens to be feedlot manure. Feedlot manure is attractive because it is nearly ten times cheaper than coal and is relatively inexpensive to transport. There exists nearly six million head of cattle in Northwest Texas which produce 25,000 tons of manure each day. Feedlot manure presents water and air pollution concerns if not disposed of properly. As such, the feedlot operators are eager to find methods of safely disposing of the feedlot manure. A small scale boiler burner facility has been constructed to simulate a utility class boiler. Experiments were conducted with coal only and then for coal/feedlot manure. Three types of feedlot manure are examined; raw feedlot manure, partially composted feedlot manure, and finished composted feedlot manure. Performance characteristics and emission data were taken for each case. A summary of the results is as follows: (I) sulfur Wyoming coal was fired and a gasification efficiency of 66% was measured. (i I) Emissions measurements were recorded and it was seen that emissions of NO,, and S02 increased as the burnt mass fraction increased. However, all emissions were within NSPS guidelines. (iii) The successful firing of coal and feedlot manure was achieved, a gasification efficiency in the range of 86% was measured, which is higher than 66% obtained when firing coal alone. (iv) When the fuel blend is fully burnt, the NO,, emissions with the blend firing was lower than the firing of coal alone.