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Removal of alkalies from portland cement kiln dust
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1986
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Description:"Ten to twelve million tons of dust is produced by cement kilns annually in the United States, resulting in a serious waste disposal problem. The Bureau of Mines investigated two alkali volatilization methods for converting this dust into materials for making portland cement and a useful potassium product. Portland cement kiln dust was found to be composed of finely ground cement raw materials (caco3 and sio2) having a layer of alkali sulfate (k2so4 and na2so4). In this form, it cannot be directly recycled to cement kilns because concrete is weakened by a reaction between the alkali and the aggregate. Portland cements with 28-day strengths above 5,000 psi were produced from low-alkali residues using sintering and melting methods. For nearly complete removal of alkalies, primarily potassium sulfate, from cement kiln dust, a temperature above 1,300 deg. C and a reducing atmosphere were required." - NIOSHTIC-2
NIOSHTIC no. 10005361
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