COMMERCIAL-SCALE RECOVERY OF LIGHTWEIGHT BLOCK SAND FROM STORED COAL COMBUSTION ASH

Coal based electrical generation accounts for over half of the electricity generated in the United States. Advances in coal combustion technology have significantly reduced power plant emissions, however, storage and management of solid by-products remains a significant challenge. One approach to address this challenge is to increase utilization of these materials in high volume applications. Many coal-fired utilities dispose of ash via a series of settling ponds that accumulate settled solids. A high degree of stratification takes place in this depositional environment that results in localized accumulations of coarse ash particles. A technology is described whereby coarse solids are removed from the pond, classified and separated by gravity concentration to produce sand suitable for the manufacture of lightweight masonry blocks. To date, two commercial scale production facilities are in operation utilizing this technology with another scheduled for start-up in the summer of 2001. Each of these installations produce 50,000 to 100,000 tons of block sand per year. This paper describes the processing flowsheet, design considerations and results of block testing.

• INTRODUCTION

• PROCESSING TO CONTROL SIZE DISTRIBUTION

• PROCESSING TO REMOVE IMPURITIES

• COMMERCIAL-SCALE PROCESSING PLANTS

• CONCLUSIONS

• REFERENCES