Recent Developments in the Utilization of Western U.S. Coal Conversion Ash
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RECENT DEVELOPMENTS IN THE UTILIZATION OF WESTERN U.S. COAL CONVERSION ASH O.E. MANZ* and DENNIS L. LAUDAL** *Coal By-Products Utilization Laboratory, Mining and Mineral Resources Research Institute, **Energy Research Center, University of North Dakota, Grand Forks, ND 58202 Received 21 October,
1986; refereed
ABSTRACT The utilization of ashes from combustion or gasification of western U.S. coals offers many possibilities for useful products. Of the possible uses, the following have been identified in an earlier study [1] as having sufficient potential for laboratory development and testing: mineral wool, sulfur concrete, high flexural-strength ceramics, replacement of cement in concrete, and road stabilization. Three lignite-derived ash products from the Beulah, ND, site were used in the present study: fixed-bed gasification ash; a dry scrubber ash; a combination bottom ash/economizer ash from an electrical power plant, Where possible, ASTM fabrication and testing procedures were used. Mineral wool of similar physical character to commercial wool and at lower potential cost was produced using 100 percent of various western ashes. Sulfur concrete utilizing 80% ash and 20% modified sulfur developed flexural and compressive strengths in excess of 2,250 and 5,000 psi, respectively. An economically competitive vitrified ceramic product with flexural strength above 7,800 psi was produced from a mixture of 50% ash, 45% sand, and 5% clay. By using a total ash mixture of 26% gasifier ash and 74% combustion ash, a very satisfactory, economical and durable roadbed material was developed. The replacement of up to 50% of the cement in concrete with western fly ash produces economical, high strength concrete. INTRODUCTION Coal gasification waste products, including those from fixed-bed gasification, have different properties from the combustion ashes, especially with respect to mineralogy [1,2]. To date, comparatively little effort has been directed toward the investigation of bulk utilization of this class of ash. A Gas Research Institute study [3] was directed toward correction of that deficiency by matching properties of lignite-derived fixed-bed ash from the Beulah, North Dakota, gasification plant (originally known as the Great Plains Gasification Associates (GPGA) plant) and combustion ash from the nearby power plant, the Antelope Valley Station (AVS), with existing practical economic possibilities. Manz [4] and Severson et al. [5] have described some of the possible applica-ations for utilization of western U.S. coal ash, including ash from the Beulah site. This paper summarizes three years of bulk utilization research on the GPGA gasifier ash and the AVS scrubber and bottom ash. The following options were explored: mineral wool, sulfur concrete, high-flexural-strength ceramics, dual concrete replacement, and road stabilization. Where possible, standard ASTM procedures were followed. For most of the options investigated, considerable time was saved by drawing on previous experience at the University of North Dakota (UN
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