Prediction of Mercury Speciation in Coal-Combustion Systems

2006 ◽  
Author(s):  
Neelesh S. Bhopatkar ◽  
Heng Ban ◽  
Thomas K. Gale
Keyword(s):  
Flue Gas ◽  
Power Plants ◽  
Heterogeneous Reaction ◽  
Oxidation Mechanism ◽  
Full Scale ◽  
Carbon Surface ◽  
Unburned Carbon ◽  
Oxidation Reactions ◽  
Mercury Oxidation ◽  
Chemical Kinetic Model

This study is a part of a comprehensive investigation, to conduct bench-, pilot-, and full-scale experiments and theoretical studies to elucidate the fundamental mechanisms associated with mercury oxidation and capture in coal-fired power plants. The objective was to quantitatively describe the mechanisms governing adsorption, desorption, and oxidation of mercury in coal-fired flue gas carbon, and establish reaction-rate constants based on experimental data. A chemical-kinetic model was developed which consists of homogeneous mercury oxidation reactions as well as heterogeneous mercury adsorption reactions on carbon surfaces. The homogeneous mercury oxidation mechanism has eight reactions for mercury oxidation. The homogeneous mercury oxidation mechanism quantitatively predicts the extent of mercury oxidation for some of datasets obtained from synthetic flue gases. However, the homogeneous mechanism alone consistently under predicts the extent of mercury oxidation in full scale and pilot scale units containing actual flue gas. Heterogeneous reaction mechanisms describe how unburned carbon or activated carbon can effectively remove mercury by adsorbing hydrochloric acid (HCI) to form chlorinated carbon sites, releasing the hydrogen. The elemental mercury may react with chlorinated carbon sites to form sorbed HgCl. Thus mercury is removed from the gas-phase and stays adsorbed on the carbon surface. Predictions using this model have very good agreement with experimental results.

Microstructure of trona sorbents from fossil fuel plant full-scale dry injection tests

1984 ◽  
Vol 42 ◽  
pp. 664-665
Author(s):  
R. T. Greer ◽  
D. T. Zhang
Keyword(s):  
Flue Gas ◽  
Power Plants ◽  
Fossil Fuel ◽  
Elevated Temperatures ◽  
Economic Incentives ◽  
Full Scale ◽  
Phase Identification ◽  
Gas Streams ◽  
Injection Process ◽  
Station Unit

The use of dry sorbents for the removal of SO2 from the flue gas of coal-fired power plants is of interest in reducing the complexity of SO2 removal and appears to offer economic incentives. In 1982, the Electric Power Research Institute, Public Service company of Colorado (PSCCO), and Multi-Mineral Corporation co-sponsored a full-scale demonstration of the dry injection process at the Cameo Station, Unit 1, of PSCCO near Grand Junction, Colorado.Laboratory comparative studies of nahcolite (NaHCO3), trona and soda ash Na2CO3) with that exposed to gas streams of air or of SO2 at elevated temperatures have been reported to provide microstructural data (from SEM) for correlation with microchemical information and phase identification for possible reactions of these materials which may occur under conditions for injection of a dry sorbent at the utility plant, and which may bear on the effectiveness of SO2 reaction with sorbents.

The Effect of CaBr2 on Mercury Speciation in Flue Gas: An Experimental and DFT Study

2018 ◽  
Vol 11 (1) ◽  
pp. 1-15
Author(s):  
Jun Zhong ◽  
Fangyong Li ◽  
Weijie Yang
Keyword(s):  
Flue Gas ◽  
Density Functional ◽  
Mercury Speciation ◽  
Carbon Surface ◽  
Unburned Carbon ◽  
Functional Theory ◽  
Covalent Interaction ◽  
Increasing Trend ◽  
Mercury Halide ◽  
Ontario Hydro

Background: Additives affect the formation of different mercury speciation in coal-fired derived flue gas. Objective: In order to study the effect of the additive CaBr2 content, the Ontario Hydro Method (OHM) method has been applied to analyze the mercury speciation at the entrance and export of denitration (SCR). Method: Density Functional Theory (DFT) has been used to study the adsorption of mercury halide on unburned carbon surface. Result: The results show that along with the increasing amount of additive CaBr2, there is an increasing trend of the ratio of Hg2+ in flue gas. Conclusion: CaBr2 addition contributes to oxidize Hg 0 to Hg2+ and increase the mercury concentration through SCR. DFT results indicate that the adsorption of HgBr and HgBr2 on unburned carbon surface is chemisorption, and Br-C bond is stronger than Hg-C bond, both these bonds are covalent interaction.

scholarly journals Experimental Study and Design of Biomass Co-Firing in a Full-Scale Coal-Fired Furnace with Storage Pulverizing System

Agronomy ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 810
Author(s):  
Xuebin Wang ◽  
Zia Ur Rahman ◽  
Zhaomin Lv ◽  
Yiming Zhu ◽  
Renhui Ruan ◽  
...  
Keyword(s):  
Power Plants ◽  
Nox Reduction ◽  
Full Scale ◽  
Pollutant Emissions ◽  
Unburned Carbon ◽  
Renewable Energy Resources ◽  
Furnace Efficiency ◽  
Auto Ignition ◽  
Carbon Emissions Reduction ◽  
Biomass Particles

Co-firing coal and biomass in existing power plants facilitates influential advancement in the use of renewable energy resources and carbon emissions reduction. Biomass is intended as a CO2-zero net emission because, during its rise, it uses the same fraction of CO2 from the air as that released during its combustion. In addition, the content of nitrogen and sulfur in biomass is lower than in coal. Therefore, the emissions of NOx and SOx can be minimized by co-firing it with coal. In general, the effect of biomass direct co-firing on safety, pulverizing system performance, furnace efficiency, and NOx emission in full-scale furnaces is rarely studied. In this study, biomass direct co-firing was carried out in a 55 MW tangentially fired pulverized coal furnace. The effects of biomass co-firing on safety, the performance of the pulverizing system, furnace efficiency, and pollutant emissions (unburned carbon and NOx) are studied. The results show that the blending of biomass fuel with less than 20% of coal has no issue with respect to auto-ignition and safety. The performance of the pulverizing system is affected up to a certain limit due to the difficulty of grinding the biomass particles into required fineness. The biomass co-firing up to 20% is feasible, but greater than this percentage will severely affect the furnace efficiency. The co-firing of biomass enhanced the NOx reduction significantly and further improved the performance of the SNCR process. This study could provide guidance for the application of biomass co-firing in industrial furnaces.

Could biomass-fueled boilers be operated at higher steam temperatures? Part 3: Initial analysis of costs and benefits

TAPPI Journal ◽  
2014 ◽  
Vol 13 (8) ◽  
pp. 65-78 ◽  
Author(s):  
W.B.A. (SANDY) SHARP ◽  
W.J. JIM FREDERICK ◽  
JAMES R. KEISER ◽  
DOUGLAS L. SINGBEIL
Keyword(s):  
Flue Gas ◽  
Power Plants ◽  
Superheated Steam ◽  
Black Liquor ◽  
Simulation Software ◽  
Operating Conditions ◽  
Costs And Benefits ◽  
Steam Generation ◽  
Fireside Corrosion ◽  
Corrosion Resistant

The efficiencies of biomass-fueled power plants are much lower than those of coal-fueled plants because they restrict their exit steam temperatures to inhibit fireside corrosion of superheater tubes. However, restricting the temperature of a given mass of steam produced by a biomass boiler decreases the amount of power that can be generated from this steam in the turbine generator. This paper examines the relationship between the temperature of superheated steam produced by a boiler and the quantity of power that it can generate. The thermodynamic basis for this relationship is presented, and the value of the additional power that could be generated by operating with higher superheated steam temperatures is estimated. Calculations are presented for five plants that produce both steam and power. Two are powered by black liquor recovery boilers and three by wood-fired boilers. Steam generation parameters for these plants were supplied by industrial partners. Calculations using thermodynamics-based plant simulation software show that the value of the increased power that could be generated in these units by increasing superheated steam temperatures 100°C above current operating conditions ranges between US$2,410,000 and US$11,180,000 per year. The costs and benefits of achieving higher superheated steam conditions in an individual boiler depend on local plant conditions and the price of power. However, the magnitude of the increased power that can be generated by increasing superheated steam temperatures is so great that it appears to justify the cost of corrosion-mitigation methods such as installing corrosion-resistant materials costing far more than current superheater alloys; redesigning biomassfueled boilers to remove the superheater from the flue gas path; or adding chemicals to remove corrosive constituents from the flue gas. The most economic pathways to higher steam temperatures will very likely involve combinations of these methods. Particularly attractive approaches include installing more corrosion-resistant alloys in the hottest superheater locations, and relocating the superheater from the flue gas path to an externally-fired location or to the loop seal of a circulating fluidized bed boiler.

"Recent Patents on the Triboelectrostatic Separation of Fly Ash"

2019 ◽  
Vol 13 ◽  
Author(s):  
Haisheng Li ◽  
Wenping Wang ◽  
Yinghua Chen ◽  
Xinxi Zhang ◽  
Chaoyong Li
Keyword(s):  
Fly Ash ◽  
Power Plants ◽  
High Efficiency ◽  
Separation Efficiency ◽  
High Reliability ◽  
Operating Conditions ◽  
Security Requirements ◽  
Unburned Carbon ◽  
Efficient Operation ◽  
Triboelectrostatic Separation

Background: The fly ash produced by coal-fired power plants is an industrial waste. The environmental pollution problems caused by fly ash have been widely of public environmental concern. As a waste of recoverable resources, it can be used in the field of building materials, agricultural fertilizers, environmental materials, new materials, etc. Unburned carbon content in fly ash has an influence on the performance of resource reuse products. Therefore, it is the key to remove unburned carbon from fly ash. As a physical method, triboelectrostatic separation technology has been widely used because of obvious advantages, such as high-efficiency, simple process, high reliability, without water resources consumption and secondary pollution. Objective: The related patents of fly ash triboelectrostatic separation had been reviewed. The structural characteristics and working principle of these patents are analyzed in detail. The results can provide some meaningful references for the improvement of separation efficiency and optimal design. Methods: Based on the comparative analysis for the latest patents related to fly ash triboelectrostatic separation, the future development is presented. Results: The patents focused on the charging efficiency and separation efficiency. Studies show that remarkable improvements have been achieved for the fly ash triboelectrostatic separation. Some patents have been used in industrial production. Conclusion: According to the current technology status, the researches related to process optimization and anti-interference ability will be beneficial to overcome the influence of operating conditions and complex environment, and meet system security requirements. The intelligent control can not only ensure the process continuity and stability, but also realize the efficient operation and management automatically. Meanwhile, the researchers should pay more attention to the resource utilization of fly ash processed by triboelectrostatic separation.

Capturing CO2 in flue gas from fossil fuel-fired power plants using dry regenerable alkali metal-based sorbent

2013 ◽  
Vol 39 (6) ◽  
pp. 515-534 ◽  
Author(s):  
Chuanwen Zhao ◽  
Xiaoping Chen ◽  
Edward J. Anthony ◽  
Xi Jiang ◽  
Lunbo Duan ◽  
...  
Keyword(s):  
Alkali Metal ◽  
Flue Gas ◽  
Power Plants ◽  
Fossil Fuel

scholarly journals Effect of Flue Gases’ Corrosive Components on the Degradation Process of Evaporator Tubes

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 3860
Author(s):  
Mária Hagarová ◽  
Milan Vaško ◽  
Miroslav Pástor ◽  
Gabriela Baranová ◽  
Miloš Matvija
Keyword(s):  
Flue Gas ◽  
Power Plants ◽  
Gas Flow ◽  
Degradation Process ◽  
Flue Gases ◽  
Saturated Steam ◽  
Mineral Salts ◽  
Related Factors ◽  
Local Overheating ◽  
Inner Surface

Corrosion of boiler tubes remains an operational and economic limitation in municipal waste power plants. The understanding of the nature, mechanism, and related factors can help reduce the degradation process caused by corrosion. The chlorine content in the fuel has a significant effect on the production of gaseous components (e.g., HCl) and condensed phases on the chloride base. This study aimed to analyze the effects of flue gases on the outer surface and saturated steam on the inner surface of the evaporator tube. The influence of gaseous chlorides and sulfates or their deposits on the course and intensity of corrosion was observed. The salt melts reacted with the steel surface facing the flue gas flow and increased the thickness of the oxide layer up to a maximum of 30 mm. On the surface not facing the flue gas flow, they disrupted the corrosive layer, reduced its adhesion, and exposed the metal surface. Beneath the massive deposits, a local overheating of the inner surface of the evaporator tubes occurred, which resulted in the release of the protective magnetite layer from the surface. Ash deposits reduce the boiler’s thermal efficiency because they act as a thermal resistor for heat transfer between the flue gases and the working medium in the pipes. The effect of insufficient feedwater treatment was evinced in the presence of mineral salts in the corrosion layer on the inner surface of the tube.

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