Citation:

Dastgheib, S., J. Mock, H. Salih, AND C. Patterson. Utilization of Water Utility Lime Sludge for Flue Gas Desulfurization in Coal-Fired Power Plants: Part III. Testing at a Higher Scale and Assessment of Selected Potential Operational Issues. ENERGY AND FUELS. American Chemical Society, Washington, DC, 33(11):11536-11543, (2019). https://doi.org/10.1021/acs.energyfuels.9b03132

Impact/Purpose:

Water utilities across the United States are currently generating approximately 3.2 million tons of lime sludge per year at an estimated disposal cost of approximately US$90 million, whereas power utilities are using approximately 6.3 million tons of limestone per year. The potential savings that would result from partial replacement of limestone with lime sludge was estimated to be approximately US$97 million per year. The life cycle analysis study showed that the environmental impact of lime sludge utilization in power plants under different scenarios was 2 orders of magnitude lower than that of the landfill disposal option.

Description:

The feasibility of utilizing lime sludge in the coal-fired power plants’ flue gas desulfurization process was evaluated through scale up of the previously reported laboratory-scale studies and investigating two potential operational issues, namely viscosity and metal corrosion. Two lime sludge samples and a baseline limestone sample that were previously characterized and tested for SO2 capture from a simulated flue gas at a laboratory scale, were first tested at a tenfold scale using a simulated flue gas, then tested using a slip-stream of flue gas from a coal-fired power plant. Tested lime sludge and limestone slurries reduced the SO2 concentration of the simulated flue gas from 2,000 to <1 ppm, and they demonstrated similar Hg reemission profiles. Field testing results revealed that the limestone and lime sludge slurries reduced the flue gas SO2 concentration from ~1,500 ppm to below 1 ppm. Two operational issues, namely viscosity and metal corrosion, were investigated to evaluate some of practical issues for transition from limestone to lime sludge at power plants. Based on Marsh funnel viscosity experiments conducted using slurries with different solid contents at different temperatures, flow characteristics of the limestone, lime sludge slurries and their gypsum counterparts were similar. Carbon steel, stainless steel, and Hastelloy coupons were tested for corrosion when they were in contact with lime sludge and limestone slurries at typical SO2 scrubber’s temperature. Both stainless steel and Hastelloy were resistive to corrosion when exposed to all tested slurries. A considerable but similar corrosion was observed for carbon steel coupons exposed to lime sludge and limestone slurries. Addition of 5,000 ppm chloride to slurries, increased the corrosion rate of CS considerably.

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