Disposal of Waste Dust from Cement Kilns

A survey of 101 cement plants in the United States revealed that over one fourth of the dust collected from kiln exhaust gases is discarded because of excessive concentrations of alkalies, predominantly potassium, which makes the dust unsuitable for, return to the cement making process. Leaching of alkalies from kiln dust, either in rainwater percolating through disposal piles, or in dust reclamation processes, causes the most serious water pollution problem faced by the cement industry. Treatment of the leachate by electrodialysis to recover and concentrate alkalies is recommended. A promising alternative to disposal of the dust is utilization in agriculture for neutralizing acidic soils and replenishing potassium removed by crops.