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Title: Potential flue gas impurities in carbon dioxide streams separated from coal-fired power plants

Abstract

This study estimated the flue gas impurities to be included in the CO{sub 2} stream separated from a CO{sub 2} control unit for a different combination of air pollution control devices and different flue gas compositions. Specifically, the levels of acid gases and mercury vapor were estimated for the monoethanolamine (MEA)-based absorption process on the basis of published performance parameters of existing systems. Among the flue gas constituents considered, sulfur dioxide (SO{sub 2}) is known to have the most adverse impact on MEA absorption. When a flue gas contains 3000 parts per million by volume (ppmv) SO{sub 2} and a wet flue gas desulfurization system achieves its 95% removal, approximately 2400 parts per million by weight (ppmw) SO{sub 2} could be included in the separated CO{sub 2} stream. In addition, the estimated concentration level was reduced to as low as 135 ppmw for the SO{sub 2} of less than 10 ppmv in the flue gas entering the MEA unit. Furthermore, heat-stable salt formation could further reduce the SO{sub 2} concentration below 40 ppmw in the separated CO{sub 2} stream. In this study, it is realized that the formation rates of heat-stable salts in MEA solution are not readily available inmore » the literature and are critical to estimating the levels and compositions of flue gas impurities in sequestered CO{sub 2} streams. In addition to SO{sub 2}, mercury, and other impurities in separated CO{sub 2} streams could vary depending on pollutant removal at the power plants and impose potential impacts on groundwater. Such a variation and related process control in the upstream management of carbon separation have implications for groundwater protection at carbon sequestration sites and warrant necessary considerations in overall sequestration planning, engineering, and management. 63 refs., 1 fig., 3 tabs.« less

Authors:
; ;  [1]
  1. University of Cincinnati, Cincinnati, OH (United States). Department of Chemical and Materials Engineering
Publication Date:
OSTI Identifier:
21233529
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of the Air and Waste Management Association; Journal Volume: 59; Journal Issue: 6
Country of Publication:
United States
Language:
English
Subject:
01 COAL, LIGNITE, AND PEAT; 20 FOSSIL-FUELED POWER PLANTS; 54 ENVIRONMENTAL SCIENCES; FLUE GAS; CARBON DIOXIDE; COAL; FOSSIL-FUEL POWER PLANTS; SULFUR DIOXIDE; MERCURY; GROUND WATER; AQUIFERS; CARBON SEQUESTRATION; UNDERGROUND STORAGE; WATER POLLUTION; IMPURITIES; MEA PROCESS

Citation Formats

Joo-Youp Lee, Tim C. Keener, and Y. Jeffery Yang. Potential flue gas impurities in carbon dioxide streams separated from coal-fired power plants. United States: N. p., 2009. Web.
Joo-Youp Lee, Tim C. Keener, & Y. Jeffery Yang. Potential flue gas impurities in carbon dioxide streams separated from coal-fired power plants. United States.
Joo-Youp Lee, Tim C. Keener, and Y. Jeffery Yang. Mon . "Potential flue gas impurities in carbon dioxide streams separated from coal-fired power plants". United States. doi:.
@article{osti_21233529,
title = {Potential flue gas impurities in carbon dioxide streams separated from coal-fired power plants},
author = {Joo-Youp Lee and Tim C. Keener and Y. Jeffery Yang},
abstractNote = {This study estimated the flue gas impurities to be included in the CO{sub 2} stream separated from a CO{sub 2} control unit for a different combination of air pollution control devices and different flue gas compositions. Specifically, the levels of acid gases and mercury vapor were estimated for the monoethanolamine (MEA)-based absorption process on the basis of published performance parameters of existing systems. Among the flue gas constituents considered, sulfur dioxide (SO{sub 2}) is known to have the most adverse impact on MEA absorption. When a flue gas contains 3000 parts per million by volume (ppmv) SO{sub 2} and a wet flue gas desulfurization system achieves its 95% removal, approximately 2400 parts per million by weight (ppmw) SO{sub 2} could be included in the separated CO{sub 2} stream. In addition, the estimated concentration level was reduced to as low as 135 ppmw for the SO{sub 2} of less than 10 ppmv in the flue gas entering the MEA unit. Furthermore, heat-stable salt formation could further reduce the SO{sub 2} concentration below 40 ppmw in the separated CO{sub 2} stream. In this study, it is realized that the formation rates of heat-stable salts in MEA solution are not readily available in the literature and are critical to estimating the levels and compositions of flue gas impurities in sequestered CO{sub 2} streams. In addition to SO{sub 2}, mercury, and other impurities in separated CO{sub 2} streams could vary depending on pollutant removal at the power plants and impose potential impacts on groundwater. Such a variation and related process control in the upstream management of carbon separation have implications for groundwater protection at carbon sequestration sites and warrant necessary considerations in overall sequestration planning, engineering, and management. 63 refs., 1 fig., 3 tabs.},
doi = {},
journal = {Journal of the Air and Waste Management Association},
number = 6,
volume = 59,
place = {United States},
year = {Mon Jun 15 00:00:00 EDT 2009},
month = {Mon Jun 15 00:00:00 EDT 2009}
}
  • An efficient chemical absorption method capable of cyclic fixed-bed operations under moist conditions for the recovery of carbon dioxide from flue gases has been proposed employing K{sub 2}CO{sub 3}-on-carbon. Carbon dioxide was chemically absorbed by the reaction K{sub 2}CO{sub 3} + CO{sub 2} + H{sub 2}O {r_equilibrium} 2KHCO{sub 3} to form potassium hydrogen carbonate. Moisture, usually contained as high as 8--17% in flue gases, badly affects the capacity of conventional adsorbents such as zeolites, but the present technology has no concern with moisture; water is rather necessary in principle as shown in the equation above. Deliquescent potassium carbonate should bemore » supported on an appropriate porous material to adapt for fixed-bed operations. After breakthrough of carbon dioxide, the entrapped carbon dioxide was released by the decomposition of hydrogen carbonate to shift the reaction in reverse on flushing with steam, which could be condensed by cooling to afford carbon dioxide in high purity. Among various preparations of alkaline-earth carbonates (X{sub 2}CO{sub 3}, X = Li, Na, K) on porous materials, K{sub 2}CO{sub 3}-on-activated carbon revealed excellent properties for the present purpose. Preparation and characterization of K{sub 2}CO{sub 3}-on-carbon and illustrative fixed-bed operations under flue gas conditions in laboratory columns and a bench-scale plant are described.« less
  • Bromine gas was evaluated for converting elemental mercury (Hg{sup 0} to oxidized mercury, a form that can readily be captured by the existing air pollution control device. The gas-phase oxidation rates of Hg{sup 0} by Br{sub 2} decreased with increasing temperatures. SO{sub 2}, CO, HCl, and H{sub 2}O had insignificant effect, while NO exhibited a reverse course of effect on the Hg{sup 0} oxidation: promotion at low NO concentrations and inhibition at high NO concentrations. A reaction mechanism involving the formation of van der Waals clusters is proposed to account for NO's reverse effect. The apparent gas-phase oxidation rate constant,more » obtained under conditions simulating a flue gas without flyash, was 3.61 x 10{sup -17} cm{sup 3}molecule{sup -1}s{sup -1} at 410 K corresponding to a 50% Hg{sup 0} oxidation using 52 ppm Br{sub 2} in a reaction time of 15 s. Flyash in flue gas significantly promoted the oxidation of Hg{sup 0} by Br{sub 2}, and the unburned carbon component played a major role in the promotion primarily through the rapid adsorption of Br{sub 2} which effectively removed Hg{sup 0} from the gas phase. At a typical flue gas temperature, SO{sub 2} slightly inhibited the flyash-induced Hg{sup 0} removal. Conversely, NO slightly promoted the flyash induced Hg{sup 0} removal by Br{sub 2}. Norit Darco-Hg-LH and Darco-Hg powder activated carbons, which have been demonstrated in field tests, were inferred for estimating the flyash induced Hg{sup 0} oxidation by Br{sub 2}. Approximately 60% of Hg{sup 0} is estimated to be oxidized with the addition of 0.4 ppm of gaseous Br{sub 2} into full scale power plant flue gas. 21 refs., 4 figs., 2 tabs.« less
  • Recent advances have been made in hydrotreating of power plant boiler flue gases to reduce SO{sub x} and NO{sub x}, the major components of acid rain, to hydrogen sulfide and nitrogen, and to convert excess oxygen to water. The sulfur pollutants in the form of H{sub 2}S can be recovered and converted to elemental sulfur by a selective amine unit and a Recycle Seletox sulfur recovery unit. This combination of units, the Parsons Flue Gas Cleanup (FGC) Process, shows great promise in abating the SO{sub x} and NO{sub x} pollutants from coal-fired power plants and provides a novel use formore » selective amines. This paper reviews some of the earlier applications of amine in flue gas treating and the recent development of the Parsons FGC Process for over 99% removal of both SO{sub x} and NO{sub x}.« less
  • In-duct mercury capture efficiency by activated carbon from coal-combustion flue gas was investigated. To this end, elemental mercury capture experiments were conducted at 100 C in a purposely designed 65-mm ID labscale pyrex apparatus operated as an entrained flow reactor. Gas residence times were varied between 0.7 and 2.0 s. Commercial-powdered activated carbon was continuously injected in the reactor and both mercury concentration and carbon elutriation rate were followed at the outlet. Transient mercury concentration profiles at the outlet showed that steady-state conditions were reached in a time interval of 15-20 min, much longer than the gas residence time inmore » the reactor. Results indicate that the influence of the walls is non-negligible in determining the residence time of fine carbon particles in the adsorption zone, because of surface deposition and/or the establishment of a fluid-dynamic boundary layer near the walls. Total mercury capture efficiencies of 20-50% were obtained with carbon injection rates in the range 0.07-0.25 g/min. However, only a fraction of this capture was attributable to free-flowing carbon particles, a significant contribution coming from activated carbon staying near the reactor walls. Entrained bed experiments at lab-scale conditions are probably not properly representative of full-scale conditions, where the influence of wall interactions is lower. Moreover, previously reported entrained flow lab-scale mercury capture data should be reconsidered by taking into account the influence of particle-wall interactions.« less