Coal-burning Power Plants Research Articles

Formic acid synthesis – a case study of CO2 utilization from coal direct chemical looping combustion power plant

ABSTRACT Chemical looping combustion (CLC) is an encouraging technology for hydrogen and power co-generation with efficient CO2 capture. Utilization of the captured CO2 is a much more important task to realize negative CO2 emissions. The objective of the work is to explore a case study of carbon dioxide utilization (CDU) in the form of formic acid synthesis using the captured CO2 and co-generated H2 from coal direct chemical looping (CDCL) power plant. Steady-state simulations are performed on the power and H2 co-generation CDCL plant integrated with formic acid synthesis and presented a comparison of overall performance of the CDCL plants with and without CDU integration. The simulation results revealed that the formic acid synthesis integrated CDCL plant avoids release of 62.49 kg.CO2/GJ of fuel input into the environment and utilizes the captured CO2 completely with the net electrical efficiency penalty of 5.8%.

Estimating power plant CO2 emission using OCO-2 XCO2 and high resolution WRF-Chem simulations

Anthropogenic CO2 emission from fossil fuel combustion has major impacts on the global climate. The Orbiting Carbon Observatory 2 (OCO-2) observations have previously been used to estimate individual power plant emissions with a Gaussian plume model assuming constant wind fields. The present work assesses the feasibility of estimating power plant CO2 emission using high resolution chemistry transport model simulations with OCO-2 observation data. In the new framework, 1.33 km Weather Research and Forecasting-Chem (WRF)-Chem simulation results are used to calculate the Jacobian matrix, which is then used with the OCO-2 XCO2 data to obtain power plant daily mean emission rates, through a maximum likelihood estimation. We applied the framework to the seven OCO-2 observations of near mid-to-large coal burning power plants identified in Nassar et al (2017 Geophys. Res. Lett. 44, 10045–53). Our estimation results closely match the reported emission rates at the Westar power plant (Kansas, USA), with a reported value of 26.67 ktCO2/day, and our estimated value at 25.82–26.47 ktCO2/day using OCO-2 v8 data, and 22.09–22.80 ktCO2/day using v9 data. At Ghent, KY, USA, our estimations using three versions (v7, v8, and v9) range from 9.84–20.40 ktCO2/day, which are substantially lower than the reported value (29.17 ktCO2/day). We attribute this difference to diminished WRF-Chem wind field simulation accuracy. The results from the seven cases indicate that accurate estimation requires accurate meteorological simulations and high quality XCO2 data. In addition, the strength and orientation (relative to the OCO-2 ground track) of the XCO2 enhancement are important for accurate and reliable estimation. Compared with the Gaussian plume model based approach, the high resolution WRF-Chem simulation based approach provides a framework for addressing varying wind fields, and possible expansion to city level emission estimation.

Health symptoms among adults living near a coal-burning power plant

Coal ash is a waste product generated when coal is burned for energy. The purpose of this study was to assess health symptoms in adults living near a coal-burning power plant and compare the symptoms to a non-exposed population. A community-based mixed methods study was conducted with four neighborhoods adjacent to a coal-burning power plant. The comparison population was not exposed to coal ash and did not live near a coal-burning power plant. Adults who lived near the coal-burning power plant were significantly more likely to suffer from respiratory (AOR = 5.27, 95% CI = 2.16–12.0), gingiva (AOR = 2.46, 95% CI = 1.46–4.15), and skin symptoms (AOR = 3.37, 95% CI = 2.09–5.43). Results suggest that health symptoms may develop in people living near coal-burning power plants.

Assessment of indicators of efficiency of the steam-turbine mini-thermal power plants burning coal

In work results of calculations of main units of steam -turbine mini-thermal power plants of low power: 6, 11,4, 12, 20 and 25 MW intended for work in the autonomous mode are presented. On the basis of material, thermal and the exergy balances efficiency indicators – the exergy efficiency and specific expenses of fuel are defined. With a greatest exergy efficiency at the level of 33% have MW blocks 6, 20 and 25 that testifies to a possibility of effective combination of the boiler and turbine equipment of this power and also completing of technological schemes of mini-thermal power plant on the basis of the released drying and mill equipment, boilers and turbines of low power.

Removal of metals from technogenic waters from abandoned coal mines using geochemical barriers

Abstract A study was made of the possibility of using natural materials (vermiculites, zeolite) and wastes (ash from the Partizansk Coal-Burning Power Plant) as sorbents in geochemical barriers to manage discharges (technogenic waters) from abandoned coal mines and reduce metal concentrations to established, acceptable standards. Vermiculite from the Kovdor deposit was shown to reduce the concentrations of Fe, Co, Ni, Cu, and Zn cations, in both direct and inverse soil column models, by between two and five times.

Effect of Biomass Composition and Co-pyrolysis Retention Time on Reduction of Non-neutral CO2 Emission from Combustion of Hybrid Coal in Power Plant

Indonesia’s lignite coal and sawdust production are 131,05 and 11,82 million tonnes, respectively, which are potential to become raw material of hybrid coal through co-pyrolysis. Hybrid coal utilization will reduce non-neutral CO2 emission, a part of CO2 emission released from combustion of biomass. The aim of this study is to determine the effects on biomass composition and co-pyrolysis retention time on reduction of non-neutral CO2 emission from combustion of hybrid coal in power plant. Co-pyrolysis was conducted in a vertical tubular furnace under an inert condition in atmospheric pressure and temperature 300° C. Biomass composition and co-pyrolysis retention time was varied from 20 to 40 %-mass and from 30 to 90 minutes, respectively. Hybrid coal was characterized with proximate, ultimate and calorific value analysis. The result of analysis was used as an input on simulation to determine reduction of non-neutral CO2 emission on hybrid coal combustion in power plant. An increase in co-pyrolysis retention time (CRT) from 30 to 90 minutes increases the CO2 emission from 13.25 to 13.30 %-vol. While increase in biomass composition from 20 to 40 %-mass reduce CO2 emission from 13.18 to 12.81 %-vol. Non-neutral CO2 emission reduction rises from 24.22 to 26.86 % along with the increased of biomass composition from 20 to 40 %-mass. Average of non-neutral CO2 emission reduction is about 26.30 % in all variation. CO2 emission of hybrid coal as fuel for power plant increased along with the increased of co-pyrolysis retention time (CRT), which was about 780-830 kg CO2/MWh. The highest CO2 emission was achieved from co-pyrolysis product hybrid coal utilization with 30 %-mass of biomass composition.

HUMAN EXPOSURE ASSESSMENT TO MERCURY THROUGH HAIR ANALYSIS IN COASTAL VILLAGES OF THE VALPARAISO REGION (CHILE)

In the present study, we assessed mercury exposure of residents of different sites of Valparaiso Region (Chile) due to fish consumption and atmospheric contamination from coal-burning power plant and copper smelter. Total mercury concentration was determined in 199 hair samples and in 14 species of marine fish, purchased in the supermarket or collected in the studied fishing villages. The total mercury (THg) concentrations ranged from 0.04 to 1.78 μg g-1 in human hair samples and from 0.04 to 3.87 μg g-1 in fish samples. Importantly, hair mercury concentration was significantly higher in the case of population exposed to mercury exclusively by fish consumption (e.g. Quintay and Zapallar), in comparison to the residents exposed to industrial emissions and fish consumption (e.g. Puchuncavi, Las Ventanas, Quintero). Finally, high mercury concentrations were observed in fish types commonly consumed by the residents of the fishing villages, evidencing human exposure to mercury through fish consumption.

Factors influencing concentrations of atmospheric speciated mercury measured at the farthest island West of South Korea

East Asia is the largest emitter of mercury (Hg) in the world, but only a few studies of speciated Hg have been carried out in South Korea. In this study, total gaseous mercury (TGM), gaseous oxidized mercury (GOM), and particulate bound mercury (PBM) were measured at one of the most northwestern islands of South Korea. Concentrations of TGM and GOM were similar to those measured in other regions of Korea; however, PBM was found in much higher concentrations during cold months, most likely from coal and biomass burning in North Korea. Sources outside Korea significantly affected TGM and PBM, and GOM increased as air masses transported from domestic coal-burning power plants. During the warm months, GOM increased as gaseous elemental mercury (GEM) decreased when air masses were confined within the ocean area with minimal influence from anthropogenic emissions. This implies that there is an efficient process for the oxidation of GEM and GOM production in the marine boundary layer. The concentrations of ozone also decreased as an increase in GOM was observed, suggesting that halogens are primarily responsible for GEM oxidation.

Physiochemical Characterization and Dematerialization of Coal Class F Flyash Residues from Thermal Power Plant

Class F flyash has a low percentage content of lime and is considered as a leading category of flyash generated in India with an average utilization of nearly 55% of flyash produced by the coal-burning power plant. The coal Class F flyash residue sample has been collected from Harduaganj, Thermal Power Station India. The paper illustrates the outcome of the study carried out to examine all the relevant features of the chemical and physical properties of Class F flyash sample. Elementary quantitative results from point analysis, SEM/EDS, FTIR, and pH analysis have been done in the chemical analysis of the study. The physical characterization of the sample is done by several experimental approaches to compare all the relevant features of Class F flyash sample and common soil. The main objective of this study is to evaluate whether the locally available Class F flyash from Harduaganj Thermal Power Station India, will provide satisfactory performance in fully or partially replacement of common soil. The performance evaluation of flyash and soil in different test results included bulk density, specific gravity, plasticity, maximum dry density, optimum moisture content, and permeability in accordance with the relevant IS or ASTM standards. Finally, the reported research recommended the selection of Class F flyash sample with low-lime content that provided the close correlation of its physical properties to the common soil.

Fly ash as a sorbent for boron removal from aqueous solutions: Equilibrium and thermodynamic studies

ABSTRACT This study presents the application of fly ash from brown coal and biomass burning power plant as a sorbent for the removal of boron ions from an aqueous solution. The adsorption process efficiency depended on the parameters, such as adsorbent dosage, pH, temperature, agitation time and initial boron concentration. The experimental data fitted well with the Freundlich isotherm model and the maximum capacity was found to be 16.14 mg g−1. The adsorption kinetics followed the pseudo-second-order model. Also, the intra-particle diffusion model parameters were calculated. Thermodynamic parameters such as change in free energy (ΔG°), enthalpy (ΔH°), entropy (ΔS°) revealed on exothermic nature of boron adsorption onto the fly ash.

Classification of coal fly ash based on pH, CaO content, glassy components, and leachability of toxic elements.

Coal fly ash (CFA), a by-product generated from coal-burning power plants, readily leaches toxic elements into aquatic environments. The present study describes a classification system for CFA based on the chemical composition of CFA and leachability of toxic elements, which can promote the safe and effective utilization of CFA for uses such as fly ash cement. To classify CFA samples, the CaO content, leachate pH, leachability of toxic elements such as B, As, and Se, and the acid- and alkali-soluble Si and Al in glassy components were determined for ten types of CFA samples produced in Japan. The results indicated that the CFA samples could be grouped into three groups: group A, which was characterized by low CaO content, low leachate pH, and a relatively high amount of alkaline-soluble Al; group B, which was characterized by low CaO content, low leachate pH, and relatively low amount of alkaline-soluble Al; and group C, which was characterized by high CaO content, high leachate pH, and relatively low amount of alkaline-soluble Al. Characteristic of group A CFA was the simultaneous leaching of Al and the minor elements along with a gradual increase in pH. This type of CFA carries the risk of leaching toxic substances upon contact with alkali solutions. These results can aid the discovery and separation of safe and unsafe CFA, allowing the safe CFA to be used in cement to produce concrete under alkali conditions.

Reducing Water‐Soluble Phosphorus in Soil through Flue Gas Desulfurization Gypsum Application: Year of Application Effects at Multiple Sites in Wisconsin

Phosphorus runoff from agricultural land to surface water bodies, such as the Great Lakes, is an important environmental concern. Soil amendments, such as gypsum, may alter the chemistry of the soil solution to reduce the amount of water-soluble P (WSP) available for loss to runoff, and as such, the NRCS now recommends gypsum application as a Conservation Practice Standard (Code 333) for improving water quality. Interest in gypsum use has also increased as availability has increased from production of flue gas desulfurization (FGD) gypsum at many coal-burning power plants throughout the United States. This study tested three rates of unincorporated, surface-broadcast FGD gypsum application at 23 field sites in Wisconsin. The optimal rate for reducing WSP concentration and the relationship between selected soil properties and the beneficial effect of FGD gypsum application were evaluated. The FGD gypsum reduced WSP ( < 0.0001), with a significant effect compared with the control at the lowest tested rate of 1120 kg ha at 5 of the 23 sites. Few other sites saw a significant benefit. Correlation indicated that sites showing a beneficial reduction of WSP from FGD gypsum application were those with greater soil test P ( = 0.0002) and lower cation exchange capacity ( = 0.0087) values.

Simultaneous NO reduction and Hg0 oxidation over Sb modified Mn/TiO2 catalyst

Sb-modified Mn/TiO2 catalyst synthetized by sol–gel method exhibited outstanding performance in simultaneous Hg0 oxidation and NO reduction under SCR conditions at low temperature. NO removal (>90%) and Hg0 oxidation (>80%) were simultaneously obtained over MnSb/TiO2-0.25 catalyst in 200–300 °C with a GHSV of 54,000 h−1. Moreover, MnSb/TiO2-0.25 catalyst exhibited excellent tolerance to SO2 and H2O. Characterization results suggested that the well-dispersed Mn, Sb and Ti species, along with the enriched Mn4+ and surface oxygen species on Mn-Sb/TiO2-0.25 catalyst should play a critical role in its excellent catalytic performance. The formed HgO had little inhibition effect on NO reduction over MnSb/TiO2-0.25 catalyst. And the coexistence of NO and O2 has a promotion effect on Hg0 oxidation, while NH3 exhibited an inhibition effect on oxidation of Hg0. In SCR reaction process, the Hg0 oxidation efficiency was suppressed, but this effect could be basically eliminated by using a relatively low GHSV value. Thus using MnSb/TiO2-0.25 for simultaneous Hg0 oxidation and NO reduction in SCR reactor may be workable in coal-burning power plants. Based on the results of experiments and characterizations, the mechanism of synchronous removal of Hg0 and NO on MnSb/TiO2-0.25 catalyst could be described as:Hg0(ad)+Oα(Oβ)→HgO(ad), NO(g)+NO2(ad)+NH3(ad)→N2+H2O.

Strength development of recycled concrete aggregate stabilized with fly ash-rice husk ash based geopolymer as pavement base material

This research studies on the usage of fly ash (FA) and rice husk ash (RHA) based geopolymers for improving the compressive strength of recycled concrete aggregate (RCA) to be a lightweight stabilised pavement base material. A mixture of FA from coal-burning power plants and RHA from rice milling process was used as a precursor while the liquid alkaline activator (L) was a mixture of sodium hydroxide solution (NaOH) and sodium silicate solution (Na2SiO3). Various RHA/FA ratios (between 100/0 and 0/100) and NaOH/Na2SiO3 ratios (between 50/50 and 100/0) were used in this study. The FA-RHA-geopolymer stabilised RCA samples, at each NaOH/Na2SiO3 ratio were prepared at the optimum liquid alkaline activator content (OLC) for unconfined compressive strength (UCS) tests. The UCS tests were conducted after 7, 28 and 60 days of curing. The test results indicate that the UCS of FA-RHA-geopolymer stabilised RCA increases as the RHA/FA and NaOH/Na2SiO3 ratios decrease and the curing time increases. Based on the Department of Highways, Thailand, the 60/40 RHA/FA and 60/40 NaOH/Na2SiO3 mix proportions are recommended for both low and high traffic volume roads with a low unit weight of 21.1 kN/m3. This research study confirms the potential of FA-RHA-geopolymer stabilised RCA as an alternative stabilised road base material.

Modeling and optimization of wet flue gas desulfurization system based on a hybrid modeling method

ABSTRACTSulfur dioxide (SO2) is one of the main air pollutants from many industries. Most coal-fired power plants in China use wet flue gas desulfurization (WFGD) as the main method for SO2 removal. Presently, the operating of WFGD lacks accurate modeling method to predict outlet concentration, let alone optimization method. As a result, operating parameters and running status of WFGD are adjusted based on the experience of the experts, which brings about the possibility of material waste and excessive emissions. In this paper, a novel WFGD model combining a mathematical model and an artificial neural network (ANN) was developed to forecast SO2 emissions. Operation data from a 1000-MW coal-fired unit was collected and divided into two separated sets for model training and validation. The hybrid model consisting a mechanism model and a 9-input ANN had the best performance on both training and validation sets in terms of RMSE (root mean square error) and MRE (mean relative error) and was chosen as the model used in optimization. A comprehensive cost model of WFGD was also constructed to estimate real-time operation cost. Based on the hybrid WFGD model and cost model, a particle swarm optimization (PSO)-based solver was designed to derive the cost-effective set points under different operation conditions. The optimization results demonstrated that the optimized operating parameters could effectively keep the SO2 emissions within the standard, whereas the SO2 emissions was decreased by 30.79% with less than 2% increase of total operating cost.Implications: Sulfur dioxide (SO2) is one of the main pollutants generated during coal combustion in power plants, and wet flue gas desulfurization (WFGD) is the main facility for SO2 removal. A hybrid model combining SO2 removal mathematical model with data-driven model achieves more accurate prediction of outlet concentration. Particle swarm optimization with a penalty function efficiently solves the optimization problem of WFGD subject to operation cost under multiple operation conditions. The proposed model and optimization method is able to direct the optimized operation of WFGD with enhanced emission and economic performance.

Research on the Mechanism of Elemental Mercury Removal over Mn-Based SCR Catalysts by a Developed Hg-TPD Method

Using an selective catalytic reduction (SCR) catalyst to oxidize and remove elemental mercury (Hg0) synergistically is a promising method for mercury emission control in coal combustion power plant...

Igniting Soaring Droplets of Promising Fuel Slurries

High rates of environmental pollution by boilers and thermal power plants burning coal of different grades are the main reason for active research in the world aimed at the development of alternative fuels. The solution to the formulated problem acceptable in terms of environmental, technical and economic criteria is the creation of composite slurry fuels with the use of fine coal or coal processing and enrichment waste, water of different quality, and oil sludge additive. This study considers modern technologies of burning slurry fuels as well as perspective research methods of the corresponding processes. A model combustion chamber is developed for the adequate study of ignition processes. The calculation of the basic geometric dimensions is presented. The necessity of manufacturing the combustion chamber in the form of an object of complex geometry is substantiated. With its use, several typical modes of slurry fuel ignition are determined. Principal differences of ignition conditions of a single droplet and group of fuel droplets are shown. Typical vortex structures at the fuel spray injection are shown. A comparison with the trajectories of fuel aerosol droplets in real combustion chambers used for the combustion of slurry fuels is undertaken.

An economical lysimeter setup for fly ash leachate studies

Coal combustion in power plants produces a large amount of fly ash, which can be stored in monofill until further use. The quality of the inorganic leachate produced during storage can be studied by constructing a customised lysimeter setup as per the need of application and pertaining to principles described in ASTM D-4874. Factors affecting the concentration of heavy metals in fly ash leachate are the liquid to solid ratio (L/S ratio), pH of the leachant water, and properties of fly ash. Based on standards and literature survey, an economical lysimeter setup for fly ash leachate studies is developed and results are investigated. The heavy metal concentrations in the leachate extracted are complying with results of laboratory and field analysis concentrations documented in existing literature. Studies performed using the proposed economical setup would provide accelerated results for obtaining trace element concentrations, by which decisions of safe monofilling of fly ash is possible.

δ15N systematics in two minerotrophic peatlands in the eastern U.S.: Insights into nitrogen cycling under moderate pollution

Availability of reactive nitrogen (Nr; mainly ammonium, NH4+, and nitrate, NO3−) via precipitation and upwelling groundwater affects carbon (C) accumulation in peat deposits and biological greenhouse gas emissions. Isotope composition of Nr was studied at Wolf Swamp (WS) and The Glades (GL), two peatlands located in western Maryland (U.S.), to provide a more robust understanding of N cycling at the ecosystem level. In recent years, both sites experienced a moderate atmospheric pollution (3–9 kg of deposited Nr ha−1 yr−1), and possible additional Nr inputs via groundwater contaminated by fertilizers/livestock. Sampling of living Sphagnum, vertical peat profiles, atmospheric deposition, and surface bog water was carried out on October 22–24, 2017. The δ15Nr signatures of vertical precipitation were negative (mass-weighted means of −7.2 and −8.1‰ at WS and GL, respectively) despite reports that NOx emitted by coal-burning power plants, a precursor of deposited nitrate, had been extremely positive (up to +26‰). Mean δ15N values at both sites increased in the order: vertical precipitation < living Sphagnum < atmospheric N2 < surface bog water < maturating peat. Intermediate δ15N values of living Sphagnum (−1.5‰ at both sites) suggested simultaneous incorporation of isotopically light atmospheric Nr and isotopically heavy Nr from bog water in the newly formed biomass. The δ15N values of bulk peat increased downcore by 4.5 and 4.9‰ at WS and GL, respectively. Gradual mineralization of organic N, mainly by nitrification and denitrification, is isotopically selective, leaving behind higher δ15N values of bulk peat at greater peat depths. Nitrogen concentration gradients and δ15N trends in vertical peat profiles at these locations therefore cannot be used as an archive of past changes in pollution levels and N isotope signatures of incoming Nr.

Life Cycle Environmental Impact Assessment of Coupled Underground Coal Gasification and CO2 Capture and Storage: Alternative End Uses for the UCG Product Gases

Underground coal gasification (UCG) has the potential to provide a source of energy or chemical feedstock derived from coal seams, where traditional mining methods are not suitable or are uneconomical. This paper presents and compares the Life Cycle carbon footprints of UCG combined cycle power plant with/without CO2 capture with pulverised coal power plants and pulverised coal oxyfuel combustion power plants with/without CO2 capture and reports on the life cycle CO2 emission rates for the three alternative uses of UCG product gases (power, methanol and ammonia) generated at a commercial scale field operation running at 3,210 tonnes/day coal gasified with the three different coal types.