SBIR-STTR Award

The coalbeds in central and eastern Oklahoma contain over 1.6 billion tons of coal reserves but, because of the high sulfur content, marketing opportunities as a boiler fuel are limited. In the same area there are over 100 sawmills which produce large quantities of sawdust and other wood wastes. Most of this large, renewable wood waste resource is not used in any byproduct recovery operation and is available for utilization as a fuel sourceIn this program it is proposedio investigate the preparation of coal-wood-limestone pellets for use as an industrial fuel source. Limestone is added to the pellets to react with S02 to form calcium sulfate, thus reducing sulfur eniissions. Hydrolyzed cellulose (wood) is used as the binder to form the pellet. The study will involve variation of the coal/wood ratio, the limestone additive as a function of the calcium/sulfur molar ratio, coal and wood particle sizes, and the use of coals with 1.707o, 2.807o, and 4.007o sulfur. The effect of these variables on heating value of the pellet and sulfur trapping capabilities will be determined. The results will provide the basis for a technical and economic analysis to be performed in the Phase I program.AnticipatedResults Potential Commercial Applications as described by the awardee:The significance of this project is that it would utilize high-sulfur coals or fines front abandoned coal mine tailing ponds and wood wastes front sawmills as an industrial fuel. Preliminary economics indicate that a coal/wood pellet would result in an energy cost in eastern Oklahoma of less than $2.50/niillion BTU compared to $7.05 for No. 2 diesel oil, $8.74 for propane, and around $5.00 for natural gas. The process would also be applicable to other coal-niining regions of the United States.

The Phase I program demonstrated the potential technical and economic feasibility of producing coalwood-limestone pellets for use as an industrial fuel source. Waste coal fines from secondary coal recovery operations can be used in the pellets. A potentially inexpensive material made from hydrolyzed wood waste was used as the binder to form the pellets. The addition of waste wood to certain high-sulfur coal fines has the advantage of lowering the sulfur content in the fuel pellet, making it more marketable. By also adding limestone to the pellet, it was shown that S02 emissions were greatly reduced by trapping 80%-95% of the sulfur in the ash. A synergistic sulfur removal effect was found from the limestone and the alkali in the wood ash. The Phase II program is to demonstrate the production of hydrolyzed cellulose for binder and the pelleting of coal-woodlimestone pellets in a pilot plant to obtain plant scale-up and economic data. The program will be carried out in a 10 ton/day pellet pilot plant. A test to study batch versus continuous production of the hydrolyzed binder at a contract facility is proposed before the pilot plant is built. The Phase II program will run in three parts. The hydrolysis of cellulose to produce the binder will be studied first. Next, the pelleting operation, which is to compare the technical and the economic advantages of pelleting versus briquetting, will be studied. In the third part, quantities of pellets will be produced for market testing by potential users. The size of the pilot plant is partially dictated by the requirement to produce substantial quantities of pellets for market evaluation. For example, the minimum quantity of coal pellets required for a cement plant demonstration is 200 tons.Anticipated Results/Potential Commercial Applications as described by the awardee:Successful operation of the pilot plant to confirm the estimated production costs for coal-wood-limestone pellets would create new opportunities to market high-sulfur coal and coal fines from secondary coal recovery operations. It is anticipated that these fuel pellets could result in energy costs to users of less than $2.00/million BTU. The immediate potential commercial application is for a coal pellet for the cement industry. This market can utilize pelleted coal fines with up to 2.5% sulfur. Some cement plants burn 40-70 tons of coal/hr. A second market exists for coal-wood-limestone pellets as stoker fuel for small to medium-size industrial plants.