Evaluation of Potential Uses of AFBC Solid Wastes
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EVALUATION OF POTENTIAL USES OF AFBC SOLID WASTES E.E. BERRY* and E.J. ANTHONY** *P.O. Box 7261, Oakville, Ontario, Canada **CANMET, Energy Mines and Resources Canada, Ottawa, Ontario, Canada Received 19 January,
1987; Communicated by G.J.
McCarthy
ABSTRACT This paper presents a brief review of the literature dealing with utilization of atmospheric-pressure fluidized bed combustion (AFBC) solid wastes. The uses that have been proposed for AFBC residues include the following: agricultural lime, waste neutralization and stabilization, low-strength backfill, soil cementing and asphaltic concrete aggregate. An evaluation of a high-Ca waste from a Canadian AFBC installation is discussed. The waste was found to be unsuitable for applications in Port-land cement concrete because of poor strength development and expansion in mortars. The waste was compatible with Portland cement for soil cementing purposes but the resulting mixes Applications in asphaltic conwere not resistant to freezing and thawing. crete were found to be successful in the laboratory and a small field trial is in progress. INTRODUCTION Atmospheric-pressure fluidized bed combustion is rapidly gaining acceptance in North America as a means to use "problem" fuels, such as low-grade or high-sulphur coals, for thermal power generation. In AFBC, coarsely crushed fuel is suspended in a combustion chamber with a bed-material, such as sand or limestone. The suspension is sustained by fluidizing the mass with air injected from below the bed. Fluidized bed combustion can be conducted in two modes at atmospheric pressure: in a bubbling or dense-phase bed; or in a circulating bed. In a companion paper [1] the authors have reviewed the principal differences between these two systems and the properties of the products This of fluid bed combustion using both limestone and inert bed materials. paper is directed to the potential utilization of high-Ca waste materials from both bubbling and circulating limestone beds typical of the residues expected to be produced by future commercial utility-scale AFBC in North America. Although the authors are not aware of any commercial utilization of highCa AFBC residues, a considerable body of research and demonstration data is available on their potential industrial and agricultural applications. A broad range of proposed industrial and construction uses for high-Ca AFBC residues have been investigated by Minnick [2,3] and others [4-9]. A critical review of these early studies was prepared by Berry [10] in 1984. More recently Rose [11] has conducted new investigations of high-Ca AFBC residues in low performance concretes and Berry [12] reported on the examination of high-Ca residues in soil-cement applications. Boesmans et al. [13-15] and Van er Widjven [16] have conducted general studies of applications for high-Ca residues in construction. For some years, the Tennessee Valley Authority has been involved in studdies of utilization of residues from limestone based AFBC. A summary of the scope of this work was recently presented by
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