Oxidation of North Dakota scrubber sludge for soil amendment and production of gypsum. Final report

Cooperative Power`s Coal Creek Station (CCS) the North Dakota Industrial Commission, and the US Department of Energy provided funds for a research project at the Energy and Environmental Research Center. The goals of the project were (1) to determine conditions for the conversion of scrubber sludge to gypsum simulating an ex situ process on the laboratory scale; (2) to determine the feasibility of scaleup of the process; (3) if warranted, to demonstrate the ex situ process for conversion on the pilot scale; and (4) to evaluate the quality and handling characteristics of the gypsum produced on the pilot scale. The process development and demonstration phases of this project were successfully completed focusing on ex situ oxidation using air at low pH. The potential to produce a high-purity gypsum on a commercial scale is excellent. The results of this project demonstrate the feasibility of converting CCS scrubber sludge to gypsum exhibiting characteristics appropriate for agricultural application as soil amendment as well as for use in gypsum wallboard production. Gypsum of a purity of over 98% containing acceptable levels of potentially problematic constituents was produced in the laboratory and in a pilot-scale demonstration.