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PRIORITY POLLUTANTS DM WASTEWATER DISCHARGES FROM A WET LIMESTONE SCRUBBER SYSTEM Harvey Olem, Environmental Engineer John W. Shipp, Environmental Engineer Tien-Yung J. Chu, Environmental Engineer Richard J. Ruane, Program Manager Division of Water Resources Tennessee VaUey Authority Chattanooga, Tennessee 37401 INTRODUCTION Coal contains many forms and types of contaminants, such as trace metals, trace organics, and radionuclides. When coal is burned in a power plant, a high percentage of less volatde forms of the contaminants is generally retained in the fly ash and bottom ash, whereas, a high percentage of the more volatde forms is generaUy emitted to the air environment through the stack. To meet federal clean-air standards, most coal-fired power plants need to control their sulfur dioxide (S02) emissions. Antipollution measures may include substitution of low-sulfur fuels, coal cleaning, coal gasification, changes in combustion equipment, and installation of gas desulfurization (FGD) systems. So far, the use of either low-sulfur fuels or nonregenerable FGD processes has been favored. Wet scrubbing of the flue gases is the most developed post-combustion method for removing S02. Scrubbing these stack gases for control of S02 removes some of the more volatile contaminants from the flue gas. Several of these volatUe constituents are included in the list of 129 toxic (priority) poUu- tants estabUshed by the U. S. Environmental Protection Agency [1]. The fate of the contaminants contained in the liquid and solid scrubber wastes is of concern because of their potential adverse effect on the water environment. This study evaluated the priority pollutants in wastewater discharges from the first full- scale limestone system at a Tennessee Valley Authority coal-fired power plant. The Widows Creek unit 8 limestone scrubber was originally designed and installed as a full-scale research and demonstration facility, but it has now become an integral part of the overall plan to achieve and maintain compliance with Alabama SC^ and emission regulations for the plant. All aspects of this scrubber process are of interest because the installation of 2350 MW of additional FGD equipment is being planned in the TVA system of coal-fired power plants. In addition to evaluation of aU organic and inorganic priority poUutants except asbestos and cyanide, wastewaters were characterized for conventional and nonconventional pollutants and radionucUdes. The hazardous waste potential of scrubber sludge was also evaluated. The slurry from the scrubber is discharged to a pond for settling of solids. The supernatant is returned to the plant for slurrying of limestone and other uses. The system is not a totaUy closed cycle, however, because the water used to eUminate the mist in the stack gas foUowing wet scrubbing is pumped to the plant ash pond which discharges to the Tennessee River. In addition, the mist eUminator system may use either river water or scrubber pond return water. Figure 1 includes an aerial photograph of the scrubber sludge Pond, ash pond, and associated waste streams at the Widows Creek power plant. PROCESS DESCRIPTION The removal of S02 gas from coal-fired power plant stack emissions by wet limestone (CaC03) scrubbing is a chemical process involving a reaction between acid gases and alkaline liquids. The reaction creates soUds crystals (CaS04#nH20 and CaS03*'/2H20) that can be physically or mechanicaUy removed. The relationship between the ash coUection system, limestone scrubber, mist eliminator, and resultant liquid waste streams is shown schematically in Figure 2. Flue gas passes through electrostatic precipitators which currently remove about 293
Object Description
Purdue Identification Number | ETRIWC198028 |
Title | Priority pollutants in wastewater discharges from a wet limestone scrubber system |
Author |
Olem, Harvey Shipp, John W. Chu, Tien-Yung J. Ruane, Richard J. |
Date of Original | 1980 |
Conference Title | Proceedings of the 35th Industrial Waste Conference |
Conference Front Matter (copy and paste) | http://e-archives.lib.purdue.edu/u?/engext,31542 |
Extent of Original | p. 293-306 |
Collection Title | Engineering Technical Reports Collection, Purdue University |
Repository | Purdue University Libraries |
Rights Statement | Digital object copyright Purdue University. All rights reserved. |
Language | eng |
Type (DCMI) | text |
Format | JP2 |
Date Digitized | 2009-10-22 |
Capture Device | Fujitsu fi-5650C |
Capture Details | ScandAll 21 |
Resolution | 300 ppi |
Color Depth | 8 bit |
Description
Title | page 293 |
Collection Title | Engineering Technical Reports Collection, Purdue University |
Repository | Purdue University Libraries |
Rights Statement | Digital copyright Purdue University. All rights reserved. |
Language | eng |
Type (DCMI) | text |
Format | JP2 |
Capture Device | Fujitsu fi-5650C |
Capture Details | ScandAll 21 |
Transcript | PRIORITY POLLUTANTS DM WASTEWATER DISCHARGES FROM A WET LIMESTONE SCRUBBER SYSTEM Harvey Olem, Environmental Engineer John W. Shipp, Environmental Engineer Tien-Yung J. Chu, Environmental Engineer Richard J. Ruane, Program Manager Division of Water Resources Tennessee VaUey Authority Chattanooga, Tennessee 37401 INTRODUCTION Coal contains many forms and types of contaminants, such as trace metals, trace organics, and radionuclides. When coal is burned in a power plant, a high percentage of less volatde forms of the contaminants is generally retained in the fly ash and bottom ash, whereas, a high percentage of the more volatde forms is generaUy emitted to the air environment through the stack. To meet federal clean-air standards, most coal-fired power plants need to control their sulfur dioxide (S02) emissions. Antipollution measures may include substitution of low-sulfur fuels, coal cleaning, coal gasification, changes in combustion equipment, and installation of gas desulfurization (FGD) systems. So far, the use of either low-sulfur fuels or nonregenerable FGD processes has been favored. Wet scrubbing of the flue gases is the most developed post-combustion method for removing S02. Scrubbing these stack gases for control of S02 removes some of the more volatile contaminants from the flue gas. Several of these volatUe constituents are included in the list of 129 toxic (priority) poUu- tants estabUshed by the U. S. Environmental Protection Agency [1]. The fate of the contaminants contained in the liquid and solid scrubber wastes is of concern because of their potential adverse effect on the water environment. This study evaluated the priority pollutants in wastewater discharges from the first full- scale limestone system at a Tennessee Valley Authority coal-fired power plant. The Widows Creek unit 8 limestone scrubber was originally designed and installed as a full-scale research and demonstration facility, but it has now become an integral part of the overall plan to achieve and maintain compliance with Alabama SC^ and emission regulations for the plant. All aspects of this scrubber process are of interest because the installation of 2350 MW of additional FGD equipment is being planned in the TVA system of coal-fired power plants. In addition to evaluation of aU organic and inorganic priority poUutants except asbestos and cyanide, wastewaters were characterized for conventional and nonconventional pollutants and radionucUdes. The hazardous waste potential of scrubber sludge was also evaluated. The slurry from the scrubber is discharged to a pond for settling of solids. The supernatant is returned to the plant for slurrying of limestone and other uses. The system is not a totaUy closed cycle, however, because the water used to eUminate the mist in the stack gas foUowing wet scrubbing is pumped to the plant ash pond which discharges to the Tennessee River. In addition, the mist eUminator system may use either river water or scrubber pond return water. Figure 1 includes an aerial photograph of the scrubber sludge Pond, ash pond, and associated waste streams at the Widows Creek power plant. PROCESS DESCRIPTION The removal of S02 gas from coal-fired power plant stack emissions by wet limestone (CaC03) scrubbing is a chemical process involving a reaction between acid gases and alkaline liquids. The reaction creates soUds crystals (CaS04#nH20 and CaS03*'/2H20) that can be physically or mechanicaUy removed. The relationship between the ash coUection system, limestone scrubber, mist eliminator, and resultant liquid waste streams is shown schematically in Figure 2. Flue gas passes through electrostatic precipitators which currently remove about 293 |
Resolution | 300 ppi |
Color Depth | 8 bit |
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