Clean Coal Research Articles

Energy structure transformation in the context of carbon neutralization: Evolutionary game analysis based on inclusive development of coal and clean energy

Efficient utilization of the clean coal and adoption of clean energy are key points to promote energy structure transformation in the context of carbon neutrality. Considering the influence of decision makers' subjective preferences on energy structure transformation, we introduce prospect theory and psychological account theory into the evolutionary game analysis, construct an evolutionary game model with the participation of government regulators and energy consumers, and analyze the dynamic evolution of each game subject. The results of the study show that the share of coal and clean energy in energy consumption significantly affects the strategy choice of energy consumers and government regulators. The impact of the intensity of subsidies on coal and clean energy and the resulting positive externalities on the inclusive development of coal and clean energy is nonlinear. More interestingly, the strategy combination of green regulation by government regulators and integrated energy use by energy consumers is not optimal in practice due to subjective factors such as reference effects, risk preferences, and loss aversion. This study provides a new perspective on the energy mix transition based on the current situation in China.

Experimental study on treatment of high ash coal slime by three-products flotation

ABSTRACT In this work, a three-product slime flotation experiment was conducted utilizing a two-stage direct flotation method with the BS collector and dodecane reagent system to maximize the flotation efficiency and reduce the flotation tailings along with an increase in its ash content. Modern analytical methods, such as X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) were used for analyzing the surface characteristics of the samples and their interaction with collectors. The results demonstrated a significantly higher ash content of secondary flotation tail coal compared to the primary one with increasing reagent dose. Ash content for clean coal ranges from 8.00% to 9.00% when the overall net coal output surpasses 85%, and it rises to 30.00% to 50.00% for flotation tail coal. The surface hydration membrane and BS collector form a hydrogen bond through the -OH functional group, which results in increased hydrophobicity and effectiveness of flotation.

Fuel adoption in rural heating: a field study on northern China

PurposePromoting clean heating in rural areas is crucial for achieving a low-carbon transition of energy consumption and China's dual-carbon target. The study aims to consider the energy stacking behavior in heating energy use, reveals the determinants that affect household cleaner heating choices under the winter clean heating plan (WCHP), and proposes policy recommendations for the sustainable promotion of clean heating.Design/methodology/approachWith unique rural household survey data covering the clean heating pilot regions in northern China in 2020, this study estimates the relationship between driving factors and heating energy choices through binary and multivariate probit models.FindingsThe regression estimates show that the main drivers of heating energy choices include household income per capita, education level of household head, knowledge of the WCHP, access to heating subsidies and perception of indoor air pollution. There is energy stacking behavior in rural household heating energy use. Household decisions to adopt electricity or clean coal heating are correlated with firewood or soft coal use.Originality/valueThis study is one of the few to investigate the heating energy use of rural households by allowing for the adoption of multiple energy types. Combined with a unique microsurvey dataset, it could provide rich information for formulating proper energy transition planning. The findings also shed light on the importance of heating subsidies, households' knowledge of WCHP and awareness of environmental health in choosing clean heating energy, which has not been fully valued in related research.

Preparation of a novel silica-polyvinylpyrrolidone hybrid regulator and its role in ultrafine low-rank coal flotation

ABSTRACT In upgrading low-rank coal, various promoters have been employed with their fascinating abilities to alter the surface properties of particles. For decades, regulators have been proven as effective promotors in flotation. In recent years, coal flotation has benefited from the development of hybrid regulators. The interaction between coal and gangue particles can be regulated through the adjustable properties of hybrid regulators. However, when it comes to ultrafine low-rank coal (ULC), flotation becomes more difficult. The performance of micromolecule surfactants and oily collectors is not obvious when the grain size becomes finer and the coal rank becomes lower. The polymers and nanoparticles are valued for their performance. The emphasis of this study is on the preparation of silica-polyvinylpyrrolidone hybrid regulator (SiO2-PVP) and its role in low-rank coal flotation. The effect of the hybrid regulators on ULC is revealed by surface properties and chemical interactions. The contact angle, floc size, functional group, and surface topography of ULC were regulated by SiO2-PVP. The flotation response proved the benefits of SiO2-PVP to combustible recovery and clean coal. Thus, SiO2-PVP is a reliable hybrid promoter for ULC flotation. This study will be helpful to understand the effect of the polymer-nanoparticle regulator on low-rank coal flotation.

Bioprocess development and optimization of parameters for enhancing bio-assisted method for sulfur removal from lakhra coal using rhodococcus sp SL-9

ABSTRACT The burning of coal releases toxic gases that disturb the environmental conditions. It is imperative to use this energy as much as possible. Due to its characteristics, it is possible to manipulate unused loss reserves. In this case, it is necessary to continue research emphasizing clean coal technology from an energy perspective, safety, and environmental sustainability problem. It wants to be implemented that 50% of the world’s coal reserves are low grades. In this regard, the current work is related to removing sulfur obtained from coal using newly isolated bacteria sl-9. It was determined that different process parameters might be used to remove Sulfur. There is a reduction of 45% of the total Sulfur in unprocessed coal when several parameters are controlled, such as 20% (w/v) pulp density, 180 rpm, 20 mesh (850 microns), and pH 7. So, Sl-9 has the potential to lower coal’s sulfate content.

Cleaning of Thar coal by froth flotation and water washing

The demand for a constant supply of energy is increasing day by day. To meet these increasing demands the natural resources must be utilized smartly. Coal can be a promising fuel due to its large reserves available in Pakistan. About 175 billion tons of coal reserves are found in Thar region of Sindh province. The major issue is the pre-processing cleaning of coal after it is mined out. A number of methods have been adopted to clean coal.
 Presently, cleaning of Thar coal was carried out using froth flotation and water washing techniques. Three different particle sizes (-60#, -100# and -150#) were employed to study the effect of froth flotation on ash and sulfur reduction. Experiments were carried out in laboratory flotation cell and beakers under different set of conditions (i.e., flotation with and without collector and frother and by simple water washing). Kerosene oil was used as a collector and pine oil as a frother. Characterization of raw and treated Thar coal samples was carried out by ASTM standards. The results exhibited an inverse relationship of particle size towards efficiency of the cleaning process; thus, the optimal combustible recovery was attained at -150# particle size. Furthermore, FTIR results disclosed the presence of aromatic and aliphatic structure in treated coal samples. Thermo-gravimetric analysis was also made to determine the weight loss in raw and treated samples and observed increased combustion efficiency and reactivity of Coal.

A Comprehensive Assessment of Clean Coal Fuels for Residential Use to Replace Bituminous Raw Coal

Residential coal combustion is a major source of air pollution in developing countries, including China. Indeed, precisely measuring the real-time emission of major air pollutants is often challenging and can hardly be repeated at a lab-scale. In this study, for the first time, two clean coals initiated from raw bituminous coal were burned for real-time estimation of air pollution characteristics and their thermal efficiencies in different stoves. Moreover, thermodynamic equilibrium simulations were investigated for slagging parameters using Factsage 7.1 at reaction temperature 800~1600 °C. Results revealed that the firepower of clean coals (Briquetted coal and Semi-coke) was much higher (2.2 kW and 2.1 kW) than raw coal (1.8 kW) in a traditional stove. However, the thermal efficiencies were remarkably increased (13.3% and 13.5%) in an improved stove for briquetted coal and semi-coke, respectively. The emission of major air pollutants including carbon monoxide (CO), sulfur dioxide (SO2), particulate matter (PM), polycyclic aromatic hydrocarbons (PAHs), non-methane hydrocarbons (NMHCs) from both coal and semi-coke was significantly reduced. Thermodynamic equilibrium calculations indicate that briquetted coal is not susceptible to slagging under the reaction conditions in the household stove. The current study provides guidance for the selection of alternative and efficient clean coal fuels in rural areas for household purposes coupled with public health and safety.

Experimental investigation of the desulfurization of a high sulfur coal with multi-ring sulfurous

ABSTRACT Coal desulfurization is imperative to produce clean coal and reduce the emission of harmful gas during combustion. However, organic multi-ring sulfurous in coal is more difficult to remove than inorganic sulfur. Therefore, in this paper, two desulfurization methods, traditional oxidation desulfurization method nitric acid leaching (NAL) and novel reduction potassium tert-butoxide and hydrogen silane desulfurization system (KOSi), were compared to remove the organic multi-ring sulfurous in raw coal sample. The results showed that the total sulfur content reductions of NAL and KOSi were 45.21% and 31.51%, corresponding to the loss rates of calorific value were 10.32% and 5.45%, respectively. The critical factors for the higher desulfurization rate of NAL than KOSi were the decreased particle size, the generation of cracks on the coal sample and the effective removal of sulfones (SN) from thiophene (TP) oxidation. In addition, the carbon macromolecular framework of coal particles could be destroyed in NAL system, resulting in a decrease in C-C and C-H content. This was the main reason that the calorific value loss of NAL was greater than that of KOSi. The consequence of this paper would provide data support for the selection of the desulfurization method for high sulfur coal, especially consisting of multi-ring sulfurous, in terms of indicators and mechanisms.

Study on integration of drying and separation for lignite by hot airflow gas–solid fluidized bed

With the continuous consumption of high-quality coal, the efficient development of lignite resources is an important guarantee for the stable and sustainable development of coal industry. Due to the characteristics of lignite with high moisture content, its efficient separation is still a great challenge faced by the current industry. In this study, to improve the dry beneficiation efficiency of lignite, hot airflow and impeller were introduced into the gas–solid fluidized bed to achieve the integration of drying and separation for lignite. Effects of the impeller diameter, airflow velocity, airflow temperature and impeller speed on the drying features and the fluidization characteristics of hot airflow gas–solid fluidized bed were investigated. Drying and fluidization tests indicated that the appropriate operational factors of impeller diameter of 61 mm, airflow velocity of 1.2Umf (that is, Umf is the minimum fluidizing airflow velocity), airflow temperature of 110 °C and impeller speed of 60 r/min should be adjusted to obtain the optimum fluidization environment for the drying and separation of lignite. Under the optimal operating conditions, a high-quality clean coal with ash content of 9.72 %, moisture content of 13.13 %, and calorific value of 4318.33 cal/g was obtained for 25–13 mm lignite, while that with ash content of 13.41 %, moisture content of 12.70 %, and calorific value of 4120.22 cal/g was obtained for 13–6 mm lignite. Efficient drying and separation of lignite could be realized by using the hot airflow gas–solid fluidized bed. This study provides theoretical guidance for efficient beneficiation of lignite resources with high moisture content by hot airflow gas–solid fluidized bed.

Separation performance of –0.5 mm fine coal in enhanced gravity field before and after desliming

ABSTRACT This study focused on the separation performance of a typical high-ash coal with high-mud content in the enhanced gravity field from the viewpoint of desliming. After necessity analysis of desliming, the EGS results of fine coal before and after desliming were examined. The EGS separation indicators and products were analyzed, and its separation characteristics were compared with FF and STS. The EGS results are unsatisfactory without desliming, and the sorting effect of −0.045 mm PS is inferior to other PSs. After desliming, the EGS performance of fine coal has been improved obviously. The optimal η a of 97.93%, η t of 85.99%, η c of 90.50%, and η d of 34.67% can be obtained through adjusting RF and RWP. In terms of deashing effect, FF > EGS > STS, but EGS can obtain the lowest clean coal ash of 3.02%, which reflects its advantages of preparing ultra-low ash coal. In terms of desulfurization effect, EGS > STS > FF. EGS is a clean and efficient method on fine coal deashing and desulfurization, and pre-desliming can significantly improve its separation performance. Pre-desliming EGS technology provides a new way for the sorting of fine coal with high-mud content.

The use of the Roben Jig for preparation of clean coal samples of Western Canadian coals via density separation

ABSTRACT This study compared a water-based and a solvent-based method for removing ash (washing) from coal: jigging coal in water using the Roben Jig and the float/sink method using conventional organic liquids (naphtha, perchloroethylene, methylene bromide), respectively. Clean coal curves from the two processes were compared for six coal types from British Columbia, Canada. The clean coal curve for the Roben Jig deviated from that of the organic liquids when the near-density material content was high. Also, particles were misplaced within the jigging column; however, a simple “rejig” process was capable of further cleaning the coal. The Roben Jig was used to create a clean coal sample of at least 400 kg by washing coal in batches. The clean coal curves for the jig were similar. Minor differences could be attributed to the occurrence of misplaced particles. Although the Roben Jig does not provide perfect separation of coal based on density for use in wash plant design studies, previous work has established that it is capable of creating representative clean coal composites without the use of organic liquids.

Flotation response of coal washery reject fines: Characteristics, process optimization, and oxidation

AbstractThe present paper outlines the characterization, electrokinetic behaviour, and flotation response of rejected coking coal fines with 32.5% ash generated in a coal washery in Eastern India. The response methodology and central composite rotatable design (RSM‐CCRD) were used for the process modelling and optimization of the flotation process using diesel, methyl isobutyl carbinol (MIBC), and sodium hexametaphosphate as a collector, frother, and depressant to maximize ash reduction, yield, and combustible recovery. At optimum condition, a 9.7% clean ash coal was achieved with a 63% yield at collector, frother, and depressant dosages of 0.78, 0.31, and 0.80 kg/ton, respectively. The model prediction and experimental data corroborated sufficiently. Subsequently, within 1 year, the fines oxidized and did not float with the collector. Fourier‐transform infrared spectroscopy (FTIR) confirmed surface oxidation on oxidized coal. The oxidized coal responded favourably to acid oil, a vegetable oil refinery waste. With acid oil as a collector, the oxidized coal can upgrade to 12% clean ash coal with a 60% yield; the combustible recovered is 80%. The work indicates successful upgradation of fresh and oxidized coal using the froth flotation process.

The causal links between long-term exposure to major PM2.5 components and the burden of tuberculosis in China

BackgroundWe aimed to estimate the causal impacts of long-term exposure to major PM2.5 components - including black carbon, organic matter, sulfate, nitrate, and ammonium - on the incidence and mortality of tuberculosis in China. MethodsWe collected annual and provincial-level tuberculosis incidence and mortality, concentrations of PM2.5 components, and socioeconomic indicators from between 2004 and 2018 in mainland China. We used the difference-in-differences (DID) causal inference approach with a generalized weighted quantile sum (gWQS) regression model to estimate the long-term effects and relative contributions of PM2.5 components' exposure on tuberculosis incidence and mortality. ResultsWe found that long-term multi-components exposure was significantly associated with tuberculosis incidence (WQS index IR%:8.34 %, 95 % CI:4.54 %–12.27 %) and mortality (WQS index IR%:19.49 %, 95 % CI: 9.72 %–30.13 %). Primary pollutants, black carbon and organic matter, contributed most of the overall mixture effect (over 85 %). Nitrate showed a critical role in tuberculosis burden in not-aging provinces and in regions at the Q3 stratum (i.e., the 3rd quartile) of GDP per capita and urbanization rate. Meanwhile the contribution of sulfate to tuberculosis burden in regions at the Q1 stratum of GDP per capita and urbanization rate was the largest among the effect of secondary pollutants (i.e., sulfate, nitrate, and ammonium). ConclusionThe mitigation of black carbon and organic matter pollution may significantly reduce the tuberculosis burden in China. Controlling nitrate emissions and increasing clean energy (i.e., energy sources with limited pollution emissions, such as natural gas and clean coal) may also be effective in certain regions.

Effect of 3–0 mm fine coal migration characteristics on high sulfur lignite separation in compound dry cleaning apparatus

Coal is the significant basic energy to promote the national economic development. Promoting the energy development is of great significant to realizing the energy strategic goals of Carbon Peak and Carbon Neutrality. In this paper, the influence of the migration behavior of 3–0 mm pulverized coal in the bed space on the separation of high-sulfur lignite using compound dry separation bed was mainly investigated. The migration characteristics of differentiated density and size particles in the bed space was emphatically analyzed and the optimum leading density and particle size composition to form autogenous medium bed were determined. The influence of vibration intensity and airflow velocity on the spatial stability of bed density was systematically investigated. The distribution law of low-grade high-sulfur lignite in compound dry separation bed was analyzed and the distribution area of bed products was determined. The experimental results show that when ρ = 1.8–2.0 g/cm3, d = 0.5–0.25 mm, the pulverized coal particles are distributed uniformly along bed height direction and the fluidization quality of bed reaches the optimum and they are the optimum leading particle size and density composition for forming autogenous medium bed. As the vibration amplitude and frequency increase, the density standard deviation decreases firstly and then increases. When A = 2.4 mm, f = 21 Hz, the density stability of bed space reaches the best and the influence of vibration frequency on the spatial stability of bed density is more sensitive compared with the influence of vibration amplitude. Under the condition (A = 2.4 mm, f = 21 Hz), when the airflow velocity range is Uv = 0.112–0.203 m/s, the bed density could keep being distributed uniformly and stably. Under the optimum operating conditions, the compound dry separation tests for low-grade high-sulfur lignite was conducted. The distribution law of sulfur content in the bed was analyzed and the distribution area of bed products was determined. Area Ⅰ is the low density material separation area; Area Ⅱ is the middle and high density product transition and separation area; Area III is the high density product migration area. The yield of clean coal is 73.06 % and the sulfur content, ash content and caloric value are 0.96 %、9.37 % and 12.38 MJ/Kg, respectively. The probable value (Ep) is 0.08 g/cm3 and the high-precision separation of low-grade high-sulfur lignite using compound dry separation bed has been realized.

Gas Particle Partitioning of PAHs Emissions from Typical Solid Fuel Combustions as Well as Their Health Risk Assessment in Rural Guanzhong Plain, China.

Air pollutants from the incomplete combustion of rural solid fuels are seriously harmful to both air quality and human health. To quantify the health effects of different fuel-stove combinations, gas and particle partitioning of twenty-nine species of polycyclic aromatic hydrocarbons (PAHs) emitted from seven fuel-stove combinations were examined in this study, and the benzo (a) pyrene toxicity equivalent (BaPeq) and cancer risks were estimated accordingly. The results showed that the gas phase PAHs (accounting for 68-78% of the total PAHs) had higher emission factors (EFs) than particulate ones. For all combustion combinations, pPAHs accounted for the highest proportion (84.5% to 99.3%) in both the gas and particulate phases, followed by aPAHs (0.63-14.7%), while the proportions of nPAHs and oPAHs were much lower (2-4 orders of magnitude) than pPAHs. For BaPeq, particulate phase PAHs dominated the BaPeq rather than gas ones, which may be due to the greater abundance of 5-ring particle PAHs. Gas and particle pPAHs were both predominant in the BaPeq, with proportions of 95.2-98.6% for all combustion combinations. Cancer risk results showed a descending order of bituminous coal combustion (0.003-0.05), biomass burning (0.002-0.01), and clean briquette coal combustion (10-5-0.001), indicating that local residents caused a severe health threat by solid fuel combustion (the threshold: 10-4). The results also highlighted that clean briquette coal could reduce cancer risks by 1-2 orders of magnitude compared to bulk coal and biomass. For oPAH, BcdPQ (6H-benzo(c,d)pyrene-6-one) had the highest cancer risk, ranging from 4.83 × 10-5 to 2.45 × 10-4, which were even higher than the total of aPAHs and nPAHs. The dramatically high toxicity and cancer risk of PAHs from solid fuel combustion strengthened the necessity and urgency of clean heating innovation in Guanzhong Plain and in similar places.

Pulverized Coal-Fired Boilers: Future Directions of Scientific Research

The paper provides an outlook on future directions of research and the possible applications for pulverized coal-fired boilers. One potential direction for future research is to focus on the ways to improve the efficiency of pulverized coal-fired boilers. This could involve developing new combustion technologies that are able to more thoroughly burn the coal and produce less waste or finding ways to capture and use the excess heat that is generated during the combustion process. The pulverized coal combustion process in power boilers is still being improved by the preliminary cleaning of coal and the use of various catalytic additives. Another area of research that could be valuable is the development of advanced control systems and monitoring technologies for pulverized coal-fired boilers. These systems could be used to optimize the performance of the boiler and ensure that it is operating at maximum efficiency while also providing real-time data on the condition of the boiler and any potential problems that may arise. The analysis of literature shows that several future paths of development and scientific research related to the technology of pulverized coal combustion in boilers can be distinguished.

Insights into the interaction of polycarboxylate with coal and kaolinite and their application in flotation

Kaolinite-rich coal slurries suffer from a low yield and high ash content owing to the easy mudification of kaolinite in water during flotation. This study investigates the efficient recycling of a kaolinite-rich coal slurry using sodium polycarboxylate flotation pretreatment. The differences in the mechanism of action of sodium polycarboxylate on coal and kaolinite were investigated using high-sensitivity microelectromechanical balancer (DCAT), Fourier infrared spectroscopy (FTIR), and scanning electron microscope (SEM). The results show that sodium polycarboxylate reduces the adhesion of the coal slurry and increases the adhesion of kaolinite. Sodium polycarboxylate can cover the hydrophilic groups of –OH by binding to the hydroxyl groups on the coal surface at multiple points via the polyhydroxy structure on the molecular chain. Covering the hydrophobic potential of kaolinite increases the percentages of hydrophilic groups such as Si-O and OH in FTIR. The above findings help to elucidate the separation mechanism of sodium polycarboxylate on carbon ash and improve the flotation separation effect. The optimum dosage of sodium polycarboxylate is 4 kg/t, kerosene, and 2-octanol are 10 kg/t and 12 kg/t, respectively. The yield of clean coal is 70.43 %, ash content of clean coal is 12.62 %, which increases the yield of clean coal by 40.89 % and decreases the ash content of clean coal by 8.56 % compared to the optimum dosage of froth flotation.

A distinctive determination of circular nozzles in downcomer for column flotation

This study aims to recover clean coal from valuable hard coal tailings (HCT), which have been used as solid fuels in a thermal power plant, through convenient conditions. The effective diameters of circular nozzles on the recovery of HCT were investigated by using the Jameson cell (JC) as the main purpose. Preliminary tests were conducted to determine the type and dosages of the collector and frother. The JC test results were evaluated by Yates and Box Behnken based on ANOVA analysis, statistically. It was observed that 3,000 g/ton of diesel oil, 300 g/ton of MIBC, 100 g/ton of Na2SiO3, and 60 cm of downcomer depth were found applicable levels of parameters. The decrease of the diameter increased the venturi effect of downcomer which provided the best recovery ratio of 97.79%. Besides, the results of kinetic models were obtained with desired efficiencies (CR∞ = 94.77%, k coal = 1.20, R 2 = 0.98 and SI = 2.40). The best diameter was 5 cm supplied a short time and high carrying capacity (CC) for concentrate.

Washability Study using Float-Sink Test Method of Coal from Paludda, Barru Regency, South Sulawesi, Indonesia

South Sulawesi’s coal quality is still relatively low so that its utilization is still limited, such as for fuel in cement factories and some other local industries. One of the locations for coal deposits in South Sulawesi is in the Paludda area, Pujananting District, Barru Regency. To increase the economic value of low-grade coal, special treatment is needed in the form of beneficiation before the coal is used, one of which is the Float-Sink Test method to separate clean coal from impurities. Coal samples that have been taken from the outcrop are then comminuted to produce a size of 1 to 5 mm. Coal washing was carried out using a mixed heavy liquid of perchloroethylene (1.62 g/cm3) and wash benzene (0.68 g/cm3) and produced a heavy liquid fraction ranging from 1.2 to 1.6 g/cm3. Results based on the washing yield curve, if an ash content below 4% is required, clean coal can be obtained at a fraction of 1.45 g/cm3 with a net coal recovery of up to 94%.

Research on the Impact of the “Coal to Gas” and “Coal to Electricity” Policies on Urban Air Quality

Heating in winter in the north has a significant negative impact on the quality of the atmospheric environment. The coal used for heating emits substances such as PM2.5, PM10, sulfur dioxide, carbon dioxide, etc., exacerbating atmospheric environmental pollution. Air pollution seriously affects the physical health and safety of residents, reduces their sense of happiness, brings about significant environmental pollution costs, and increases the actual level of economic inequality. In response to this situation, this article aims to improve urban air quality through the policies of “coal to gas” and “coal to electricity”, and further studies the impact of this policy. To provide empirical evidence and decision-making reference for deepening the “coal to gas, electricity” policy, and to reduce atmospheric environmental pollution, it is necessary to actively adjust the heating plan, increase the central heating area, and construct different heating scales according to different needs. It is necessary to vigorously develop clean coal technology, reduce pollutant emissions, actively explore clean energy, and fundamentally change the problem of air pollution. Therefore, the policies of “coal to gas” and “coal to electricity” can effectively improve the pollution of coal on urban air quality.