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FINAL TECHNICAL REPORT September 1, 1989 through August 31, 1990

Project Title: A METHOD FOR IMPROVING SULFUR CAPTURE USING COAL/SORBENT PELLETS

Principle Investigator: David M. Rapp, Illinois State Geological Survey (ISGS)

Other Investigators: J. M. Lytle,- M. Rostam-Abadi, K. C. Hackley, L. B. Kohlenberger, D. L. Moran, M. J. Demers, P. M. Murphy, ISGS

R. L. Berger, University of Illinois (UI-UC)

K. Griggs, Construction Engineering Research Lab

Project Monitor: Dr .. Ken K. Ho, CRSC

ABSTRACT

The objective of this work was to utilize coal fines to economically produce a clean-burning fuel that meets anticipated sulfur dioxide emission levels. To accomplish this, the process of pelletizing fine coal with a sulfur capturing sorbent such as hydrated lime is being studied. Two potential applications are being considered - fluidized bed combustors

-and industrial stokerboilers;- Carbonation is also being investigated as a method for increasing pellet quality and decreasing binder requirements. Carbonation is the reaction of hydrated 1 ime with carbon dioxide to produce a bonding matrix of calcium carbonate.

Test results indicate carbonation significantly improves compressive strength (2 to 3 fold increase), impact and attrition resistance, as well as essentially waterproofs the pellets at 15% lime content. Conventional binders such as corn starch or molasses do not produce waterproof pellets that can withstand r&infall that might come with outdo6r storage.

Combustion testing of the carbonated pellets (IBC-106, 2:1 Ca/S ratio -15% lime) indicate sulfur captures as high as 80% are achievable at 850·C, the approximate operating temperature for fluidized bed combustors. This sulfur capture would allow many high sulfur Illinois coals to be burned at the 2001 compliance S02 emission levels (1.2 lbs S02/106 Btu): Combustion tests at higher temperature (1350·C), using a quadropole gas analyzer to continuously monitor S02 and CO2 emissions, indicate appreCiable initial sul fur captures. However, continued exposure to these temperatures results in rel ease of this sulfur. The higher temperature testing indicat~s sulfur capture for coal/sorbent pellets in stoker boilers can be improved by reducing residence time in the high temperature zone or by low~ring the maximum temperatures the pellets are exposed to.