Carbonation as a binding mechanism for coal/calcium hydroxide pellets. Technical report, December 1, 1991--February 29, 1992

Abstract

In this project supported by the CRSC, the Tennessee Valley Authority (TVA) and the Engineering Research Laboratory (CERL), ISGS is investigating the pelletization of fine coal with calcium hydroxide, a sulfur capturing sorbent. The objective is to produce a readily-transportable fuel which will burn in compliance with the recently passed Clean Air Act Amendments. To improve the economics of pelletization, carbonation, or, the reaction of carbon dioxide with calcium hydroxide to produce a binding matrix of calcium carbonate, is being investigated as a method of hardening pelletized coal fines. Previous results indicate that carbonation significantly improves pellet quality including serving to weatherproof the pellets. During this quarter, work was conducted on several topics. Calcium oxide was investigated as a potentially lower cost binder than calcium hydroxide and was determined to be of comparable effectiveness on a molar basis indicating some potential for an overall cost savings. The effect of pellet size on pellet quality was also investigated. Results indicate that 1/4 and 1/2-inch diameter pellets have similar compressive strengths when compared on the basis of pounds per square inch crushing pressure. Also a low cost starch was tested as an alternative binder. Although cheaper per pound than a starch binder previously tested, it was not less expensive when evaluated on the basis of pellet quality attained.