''Effect of auto-oxidation on treatment and disposal properties of lignite derived flue gas desulfurization sludge''
Auto-oxidation or the natural conversion from CaSO/sub 3/ x 1/2 H/sub 2/O to CaSO/sub 4/ x 2H/sub 2/O occurs due to reductions of SO/sub 2/ loadings and the operating pH of lime/limestone FGD systems. Appreciable levels of auto-oxidation are prevalent on low sulfur fuels, e.g., western and lignite coal. Sludge treatment systems designed for maximum design conditions may deleteriously perform unless adequate design provisions are incorporated. Auto-oxidized FGD slurry, containing larger CaSO/sub 4/ particles, settle faster achieving higher densities. Thickener overload and consolidation can be prevented by proper drive mechanism design and underflow solids/density control. Utilization of an underflow surge tank allows a properly designed unit to temporarily store the autooxidized material and to maintain a constant and homogenous filter feed. Filtration rates and cake solids content are improved during auto-oxidation conditions, but provisions to avoid cake-cracking are recommended. The resultant higher filter cake, nonetheless, requires fly ash blending to ensure adequate transportability characteristics. Other areas of concern within the FGD System should be addressed, but these are beyond the scope of this paper. Performing a transportability analysis, for all ash and sulfur levels, identifies significant operating modes. Under some conditions, e.g., minimum sulfur, the combination of available fly ash and higher percent solids of auto-oxidized underflow, permits vacuum filter bypass. Combining fly ash and auto-oxidized material, enhances the blends' landfill suitability. Higher ash/sludge and CaSO/sub 4//SO/sub 3/ ratios increase Unconfined Compressive Strength and reduce the permeability coefficient. Properly designed FGD sludge treatment and fly ash blending systems are well-suited for lime/limestone FGD systems installed on low sulfur western or lignite coal-fired power plants.
- Research Organization:
- Waste Treatment Systems, General Electric Environmental Services
- OSTI ID:
- 5879772
- Report Number(s):
- CONF-831112-
- Journal Information:
- Coal Technol. (Houston); (United States), Journal Name: Coal Technol. (Houston); (United States) Vol. 6; ISSN COATD
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
010800* -- Coal
Lignite
& Peat-- Waste Management
20 FOSSIL-FUELED POWER PLANTS
200200 -- Fossil-Fueled Power Plants-- Waste Management
AEROSOL WASTES
ALKALINE EARTH METAL COMPOUNDS
ASHES
BROWN COAL
CALCIUM COMPOUNDS
CALCIUM SULFATES
CARBONACEOUS MATERIALS
CHEMICAL REACTIONS
COAL
COMBUSTION PRODUCTS
DESULFURIZATION
ENERGY SOURCES
FILTRATION
FLUE GAS
FLY ASH
FOSSIL FUELS
FOSSIL-FUEL POWER PLANTS
FUELS
GASEOUS WASTES
LIGNITE
MANAGEMENT
MATERIALS
MIXING
OXIDATION
OXYGEN COMPOUNDS
POWER PLANTS
PROCESSING
RESIDUES
SEPARATION PROCESSES
SLUDGES
SULFATES
SULFUR COMPOUNDS
THERMAL POWER PLANTS
WASTE DISPOSAL
WASTE MANAGEMENT
WASTE PROCESSING
WASTES