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Title: Flue gas desulfurization wastewater treatment primer

Abstract

Purge water from a typical wet flue gas desulfurization system contains myriad chemical constituents and heavy metals whose mixture is determined by the fuel source and combustion products as well as the stack gas treatment process. A well-designed water treatment system can tolerate upstream fuel and sorbent arranged in just the right order to produce wastewater acceptable for discharge. This article presents state-of-the-art technologies for treating the waste water that is generated by wet FGD systems. 11 figs., 3 tabs.

Authors:
; ;
Publication Date:
OSTI Identifier:
21176748
Resource Type:
Journal Article
Resource Relation:
Journal Name: Power (New York); Journal Volume: 153; Journal Issue: 3
Country of Publication:
United States
Language:
English
Subject:
20 FOSSIL-FUELED POWER PLANTS; 01 COAL, LIGNITE, AND PEAT; FLUE GAS; DESULFURIZATION; WATER TREATMENT; WASTE WATER; WATER TREATMENT PLANTS; DESIGN; METALS; TECHNOLOGY ASSESSMENT; WATER REMOVAL; GYPSUM; SCALING; PRECIPITATION; TRACE AMOUNTS; REMOVAL; SELENIUM

Citation Formats

Higgins, T.E., Sandy, A.T., and Givens, S.W. Flue gas desulfurization wastewater treatment primer. United States: N. p., 2009. Web.
Higgins, T.E., Sandy, A.T., & Givens, S.W. Flue gas desulfurization wastewater treatment primer. United States.
Higgins, T.E., Sandy, A.T., and Givens, S.W. 2009. "Flue gas desulfurization wastewater treatment primer". United States. doi:.
@article{osti_21176748,
title = {Flue gas desulfurization wastewater treatment primer},
author = {Higgins, T.E. and Sandy, A.T. and Givens, S.W.},
abstractNote = {Purge water from a typical wet flue gas desulfurization system contains myriad chemical constituents and heavy metals whose mixture is determined by the fuel source and combustion products as well as the stack gas treatment process. A well-designed water treatment system can tolerate upstream fuel and sorbent arranged in just the right order to produce wastewater acceptable for discharge. This article presents state-of-the-art technologies for treating the waste water that is generated by wet FGD systems. 11 figs., 3 tabs.},
doi = {},
journal = {Power (New York)},
number = 3,
volume = 153,
place = {United States},
year = 2009,
month = 3
}
  • Wastes from a limestone Flue Gas Desulfurization (FGD) system are mainly CaSO/sub 3/ with lesser amounts of CaSO/sub 4/. This thixotropic mixture has a high water content, impeding water conservation, and it exhibits physical properties making landfill applications difficult. Complete oxidation to CaSO/sub 4/ can be achieved in a two stage SO/sub 2/ absorption system at differently maintained pH levels. Forced oxidation converts the flaky CaSO/sub 3/ particles to monoclinic gypsum crystals, thereby eliminating the thixotropic properties of the sludge. Oxidation was completed at a pH of 4.5, at an air stoichiometry of 3(11.8 sec contact time), at a temperaturemore » of 76/sup 0/F, and at a slurry depth of 10 ft. The oxidized slurry, when filtered, yielded greater than 80% solids, with liquid cyclones shown to be acceptable separation devices. Settling tests resulted in sedimentations lasting for minutes, instead of hours as obtained for the unoxidized sludge, and these corresponded well with the decrease in viscosity, measured as 1200 cps for the unoxidized, compared with 1 to 2 cps for the oxidized slurry.« less
  • Magnesium hydroxide, reclaimed from the flue gas desulfurization system (FGD) at the Zimmer Power Plant, Cincinnati, Ohio, is a weak base, in the form of either a slurry or powder. It has many potential applications for wastewater treatment. The objectives of this research are (1) to characterize the reclaimed magnesium hydroxide, e.g., purity, particle size distribution, dissolution kinetics; (2) to evaluate neutralization capacity and buffering intensity of the reclaimed magnesium hydroxide; (3) to study the efficacy of the reclaimed magnesium hydroxide for nutrient removal in wastewater treatment processes; (4) to investigate whether and how the magnesium hydroxide influences the characteristicsmore » of the activated sludge floc; (5) to determine whether magnesium hydroxide improves the anaerobic sludge digestion process and associated mechanisms; and (6) to conduct a cost-benefit analysis for the application of the reclaimed magnesium hydroxide in wastewater treatment and the possibility of marketing this product. Research results to date show that the purity of the reclaimed magnesium hydroxide depends largely on the recovery hydroxide slurry. This product proved to be very effective for wastewater neutralization, compared with other commonly used chemicals, both for its neutralization capacity and its buffering intensity. Due to its relatively low solubility in water and its particle size distribution characteristics, magnesium hydroxide behaves like a weak base, which will be very beneficial for process control. The authors also found that nitrogen and phosphorus could be removed from the wastewater using magnesium hydroxide due to their complexation and precipitation as magnesium ammonium phosphate (struvite). Magnesium hydroxide also greatly enhanced the settleability of the activated sludge. Intensive research on the mechanisms associated with these phenomena reveals that sweep flocculation and magnesium ion bridging between exopolymeric substances (EPS) of the microorganisms are the major contributing factors. Extensive research on the effects of magnesium hydroxide on anaerobic sludge digestion is still underway.« less
  • The Dravo Corp. Thiosorbic flue gas desulfurization process uses lime-containing magnesium oxide to increase the alkalinity of and prevent scaling in lime and limestone-based sulfur dioxide removal systems. Data for a TVA Shawnee pilot plant showed that sulfur dioxide removal efficiency was consistently above 95% with magnesium-containing lime but varied from 70 to 98% with conventional lime. In the magnesium system, sulfur dioxide removal efficiency was independent of sulfur dioxide inlet concentration, whereas with conventional lime, the efficiency varied inversely with sulfur dioxide inlet level. Three full-scale demonstration tests have been operated using the Thiosorbic process. The systems were designedmore » to remove 83% of the sulfur dioxide from the flue gas to meet environmental regulations. A list of the operating and projected full-scale Thiosorbic operations shows that by 1980 the total number of powerplants with Thiosorbic scrubbing units will represent 5955 Mw of power generation. The system is applicable to any type of scrubber configuration.« less
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