Coal Capacity Research Articles

Influence of Coal Properties on the Gross Calorific Value and Moisture-Holding Capacity

Analysis of the composition, structure, and properties of 63 samples of Ukrainian, Russian, and United States coal clarifies their influence on the gross calorific value in the wet and dry ash-free states and the maximum moisture content. Quantitative formulas are obtained for the influence of the petrographic characteristics on the gross calorific value and moisture-holding capacity of coal from different sources. On that basis, those parameters may be calculated with high precision. The proposed formulas permit methodological recommendations in calculating the gross calorific value in the wet ash-free state. This is important in speeding the passage of imported coal through customs.

A Permit Trading Scheme for Capping Issues in Energy Transition: Case Study of Coal Capacity Control in China

The energy transition often includes capping policies on fossil fuel production or consumption but little attention in the literature has been paid to introduce a permit trading scheme to minimize the cost of such a cap. In this paper, we propose a permit trading mechanism for capping issues and apply this proposal to studying China’s coal capacity control. Theoretically, we argue that the benefits of such a trading scheme comes from rescuing high-efficiency mines being administratively closed and relocation of capacity from lower to higher efficiency mines. Using a non-parametric frontier method and more than 1100 firm-level data merged from financial data and capacity data, we estimated the benefits from a capacity permit trading could lead to more than 30% input saving and additional 26% income boost. The results also demonstrate that the economic benefits rise in a larger trading zone and the permit trading is a Pareto improvement for all participated province when compared with command and control policy. The study suggests that adopting permit trading schemes for capping policies is economically beneficial and politically feasible, and a large trading zone is preferred to a small one. Such permit concept could be used to facilitate energy transition in other countries.

Exploring the role of natural gas power plants with carbon capture and storage as a bridge to a low-carbon future.

Natural gas combined-cycle (NGCC) turbines with carbon capture and storage (CCS) could be an important source of low-carbon electricity in the future. Factors affecting the market competitiveness of NGCC-CCS are examined by conducting a sensitivity analysis using the MARKet ALlocation energy system optimization model. The results indicate that widespread deployment of NGCC-CCS is better suited for a 30% energy system greenhouse gas (GHG) reduction trajectory than for a more stringent 50% reduction trajectory. Methane leakage rate, efficiency penalty, carbon dioxide (CO2) capture rate, and natural gas price are found to be the strongest factors influencing optimal NGCC-CCS deployment, in that order. NGCC plays an important role in meeting mid-term GHG targets across all model runs. A large portion of NGCC capacity is later retrofit with CCS, indicating that NGCC can be both a bridge to a low-carbon future and an integral part of that future. Thus, retrofitability and siting near CO2storage should be considerations as new NGCC capacity is built. Regional results indicate that NGCC-CCS deployment would be greatest in the West South Central region, followed by the East North Central region. In a business-as-usual scenario, both regions have considerable electricity production from fossil fuels. Conventional coal and gas capacity are displaced under a GHG reduction target, opening the door for NGCC-CCS in these regions. NGCC-CCS market penetration is projected to have a mixed impact on air pollutant emissions and energy-related water consumption. Whether impacts are positive or negative depends on the technologies displaced by NGCC-CCS.

Experimental investigation on variation of physical properties of coal samples subjected to microwave irradiation

The gas drainage rate of low-permeability coal seam is generally less than satisfactory. This leads to the gas disaster of coal mine, and largely restricts the extraction of coalbed methane (CBM), and increases the emission of greenhouse gases in the mining area. Consequently, enhancing the gas drainage rate is an urgent challenge. To solve this problem, a new approach of using microwave irradiation (MWR) as a non-contact physical field excitation method to enhance gas drainage has been attempted. In order to evaluate the feasibility of this method, the methane adsorption, diffusion and penetrability of coal subjected to MWR were experimentally investigated. The variation of methane adsorbed amount, methane diffusion speed and absorption loop for the coal sample before and after MWR were obtained. The findings show that the MWR can change the adsorption property and reduce the methane adsorption capacity of coal. Moreover, the methane diffusion characteristic curves for both the irradiated coal samples and theoriginal coal samples present the same trend. The irradiated coal samples have better methane diffusion ability than the original ones. As the adsorbed methane decreases, the methane diffusion speed increases or remain the same for the sample subjected to MWR. Furthermore, compared to the original coal samples, the area of the absorption loop for irradiated samples increases, especially for the micro-pore and medium-pore stage. This leads to the increase of open pores in the coal, thus improving the gas penetrability of coal. This study provides supports for positive MWR effects on changing the methane adsorption and improving the methane diffusion and the gas penetrability properties of coal samples.

The 1.5°C target and coal sector transition: at the limits of societal feasibility

ABSTRACTNational and global mitigation scenarios consistent with 1.5°C require an early phase-out of coal in major coal-dependent countries, compared to standard technical and economic lifetimes. This appears particularly apparent in the light of recent massive investments in coal power capacity, the significant pipeline of coal power capacity coming online, as well as upstream supporting infrastructure. This article analyses the existing and planned capital stock in the coal power sector in the light of scenarios consistent with 1.5°C. The article analyses the political economy and labour aspects of this abrupt and significant transition, in the light of domestic equity and development objectives. Firstly, the article examines employment issues and reviews the existing literature and practice with support schemes for regional and sectoral structural adjustment for the reduction of coal sector activity. Secondly, the paper surveys the domestic political economy of coal sector transition in major coal using countries, namely Australia, South Africa, China and India. A final section provides conclusions and policy recommendations.Key policy insightsAchieving mitigation pathways in line with limiting warming to 1.5°C, or even well-below 2°C, would require the early retirement of coal sector assets in production and consumption.Historically, coal sector transition has often been associated with prolonged socio-economic dislocation in affected regions.Policies to accompany affected regions are thus a crucial part of policy mixes to limit warming to 1.5°C and even 2°C.Such policies should be anticipatory and long-term, as opposed to reactive policies focused on short-term measures to smooth the transition.A survey of major coal using countries shows that each is a long way from putting in place a long-term framework to transition the coal sector.

Efficiency of Carbon Dioxide Storage and Enhanced Methane Recovery in a High Rank Coal

The high affinity and adsorption capacity of coal to carbon dioxide provides an alternative approach for the enhanced recovery of methane from unminable coalfields (CO2-ECBM) by which a potential solution for long-term CO2 sequestration in deep geological formations can also be achieved. However, due to chemomechanical effects induced by the interactions between CO2 and coal, the effective methane production and carbon dioxide storage can be degraded which has caused uncertainties about the techno-economic feasibility of the CO2-ECBM process. This study presents an experimental investigation that aims to address key knowledge gaps related to the efficiency of CO2 storage and CH4 recovery in high rank coals for which a comprehensive experimental data set and analysis are largely missing. Competitive displacements of CH4 with N2 or CO2 in an anthracite coal sample from a South Wales coalfield have been studies, based on a series of core flooding experiments. The results show that the N2 breakthrough time (t...

Cadmium and arsenic adsorption in aqueous systems in the presence of monosilicic acid

The effect of different concentrations of monosilicic acid on the sorption capacity of quartz sand, diatomite, zeolite, and brown coal with respect to cadmium and arsenic has been studied in laboratory conditions. The applicability of different adsorption models, including exponential, semilogarithmic, and linear dependences, as well as the Langmuir and Freundlich equations, has been compared. An increase in monosilicic acid concentration from 0 to 2 mM increased the sorption capacity of all materials. It has been suggested that either the interaction of monosilicic acid with a pollutant takes place directly in the solution followed by sorption of the reaction products on the surface or in the pores of the sorbent, or first adsorption of the monosilicic acid by the sorbent occurs followed by interaction of the sorbed silicic acid with cadmium and arsenic; it is also possible that both process proceed in parallel.

Unintended consequences of China’s coal capacity cut policy

In early 2016, China introduced additional capacity cut policies to rebalance supply in the coal market to match demand that had been reduced by slow economic growth and strict environmental regulation. Ensuing disruptions to the coal market caused these policies to be revised and, subsequently, discarded as decision makers tried to find a balance between efficient supply, economic and social stability and environmental sustainability. This paper explores the causes of these unintended consequences using an extended version of the KEM-China model. The results reveal that full and partial compliance with the capacity cut policies results in a significant gap between supply and demand. This suggests that implementation of the policy was technically infeasible, even allowing for a significant increase in coal prices and economic costs. Besides, significant differences in coal prices and output profiles are registered across the country. We argue that the heterogeneous nature of the Chinese coal market and policy compliance was a major factor leading to the unintended consequences rendering a single national price benchmark inappropriate as a policy gauge. We propose that the capacity cut policy should be differentiated across regions and even types of coalmines, market approaches would be preferable to the command-and-control instruments, and policy distortions that cause excess capacity should be removed.

Effect of Coal Grain Size on Sorption Capacity with Respect to Propylene and Acetylene

Propylene and acetylene are released to mine air with the increase in the temperature of self-heating coal. Concentrations of these gases in mine air are applied as indicators of the progress of the self-heating process. Hydrocarbons emitted from the self-ignition center are sorbed on coal, while migrating through the mine workings. Coal crushed during the mining process is characterized by a high sorption capacity, which facilitates the sorption phenomena. This results in the decrease in hydrocarbons content in mine air, and in the subsequent incorrect assessment of the development of the self-heating process. The results of the experimental study on propylene and acetylene sorption on Polish coals acquired from operating coal mines are presented in this paper. Bituminous coal is characterized by a high sorption capacity with respect to unsaturated hydrocarbons, like propylene and acetylene. The sorbed volumes depend on the grade of metamorphism, porosity, and chemical characteristics of coal. Low level of metamorphism, increased porosity, and oxygen content result in higher sorption capacity of coals. The reduction in grain size of coals also results in the increased sorption capacity with respect to hydrocarbons. The most significant increase in the volumes of sorbed propylene and acetylene with the decrease in grain class was observed for coals of low porosity, high grade of metamorphism, and low to medium sorption capacities. The 10-fold decrease in coal grain size resulted in the 3 to 6-fold increase in the volume of sorbed propylene, and 2-fold increase for acetylene. The decrease in grain size results in higher accessibility of pore structure, increased pore volume and area, and higher number of active centers interacting with hydrocarbons of dipole characteristics. For coals with low grade metamorphism, high porosity, and high sorption capacity the volumes of sorbed propylene and acetylene increased only slightly with the decrease in coal grain size.

Pressurized gasification of lignite in a pilot scale bubbling fluidized bed reactor with air, oxygen, steam and CO2 agents

In this study, 80 h continuously operated gasification experiment was carried out with pilot scale pressurized bubbling fluidized bed gasifier which was operated with the coal feed capacity of 500–520 kWth (80–83 kg/h coal feed rate). The mixture of air, steam, oxygen and CO2 was used as gasification agent with different ratios. The operating pressure of gasifier in this experiment was between 2.4 and 2.7 barg. The effects of ER, steam/carbon ratios and CO2/carbon ratios on syngas composition, carbon conversion ratios and cold gas efficiencies were investigated. According to the results, using CO2 or H2O as gasification agent, may have both advantages and disadvantages for the operation. If CO2 was increased in gasification agent, shift reaction was effected negatively and H2 products were decreased. If steam was increased, cold gas efficiency was slightly decreased.

Moisture-holding capacity of coals

As a result of a comprehensive study of 63 samples of coal concentrates (from Ukraine, Russia and countries outside the former Soviet Union), it was established that the prediction of the moisture-holding capacity of coals can be appropriately performed according to their values of W a, R 0, O d daf , and O s daf . It was found that the oxidation of coal increased its moisture-holding capacity; however, in this case, the absolute change in this parameter was smaller than the error of its determination (0.5%). Therefore, upon the oxidation of almost 30% of the organic matter of coal, the moisture-holding capacity increased by only 0.4%. There is a close correlation between the maximum moisture capacity of coals and the water pore volume, and this correlation was described by a linear equation in the studies.

Evaluating the CO2 emissions reduction potential and cost of power sector re-dispatch

Prior studies of the U.S. electricity sector have recognized the potential to reduce carbon dioxide (CO2) emissions by substituting generation from coal-fired units with generation from under-utilized and lower-emitting natural gas-fired units; in fact, this type of “re-dispatch” was invoked as one of the three building blocks used to set the emissions targets under the Environmental Protection Agency's Clean Power Plan. Despite the existence of surplus natural gas capacity in the U.S., power system operational constraints not often considered in power sector policy analyses, such as transmission congestion, generator ramping constraints, minimum generation constraints, planned and unplanned generator outages, and ancillary service requirements, could limit the potential and increase the cost of coal-to-gas re-dispatch. Using a highly detailed power system unit commitment and dispatch model, we estimate the maximum potential for re-dispatch in the Eastern Interconnection, which accounts for the majority of coal capacity and generation in the U.S. Under our reference assumptions, we find that maximizing coal-to-gas re-dispatch yields emissions reductions of 230 million metric tons (Mt), or 13% of power sector emissions in the Eastern Interconnection, with a corresponding average abatement cost of $15–$44 per metric ton of CO2, depending on the assumed supply elasticity of natural gas.

Material composition, pore structure and adsorption capacity of low-rank coals around the first coalification jump: A case of eastern Junggar Basin, China

The first coalification jump (FCJ) has a significant impact on low-rank coal reservoir heterogeneity, and is of great importance for coalbed methane (CBM) development. Here, a series of experiments were performed for 10 coal samples collected from eastern Junggar Basin, to compare the material composition, pore structure and adsorption capacity of lignite and candle coal. Contrast with the candle coal, the lignite has a higher inertinite content, larger pore volume, better connectivity, and greater specific surface area (SSA). During the process of FCJ, the polycondensation of coal molecules and the compaction of coal matrix occur, leading to a rapid decline of moisture, porosity and permeability, and the cell wall in the candle coal is badly crushed with clay minerals filled from optical microscopy. In general, the larger total pore volume (1.7–300 nm, measured by N2 adsorption) contributes to the larger SSA. The SSA of candle coal mainly comes from the contribution of micropore (<10 nm), especially the 2–3 nm pores, while the micropore and transition pore (10–100 nm) contribute to most of SSA of lignite. However, though the SSA of the candle coal is largely lower than that of the lignite, the CH4 adsorption capacity tends to decrease from the lignite to the candle coal due to material composition difference. Low-field NMR was used to determine the pore and fracture system by analyzing the transverse relaxation time, which showed that only two obvious peaks could be identified in lignite and three peaks at about 0.25 ms, 30 ms and 200 ms are present in the candle coal. The fractal results indicate that the pore surface and complexity inside the coal increase gradually from lignite to candle coal. These observations could deepen awareness and understanding of low-rank coal reservoir heterogeneity and the influence of FCJ on reservoir property.

Pyrolysis characteristic of coals with different metamorphic grades and its instruction to coalbed methane development

PurposePyrolysis for coal gas generation changes the composition, pore structure, permeability and adsorption capacity of coal. This work aims to discuss the utilization of coal pyrolysis on enhancing coalbed methane (CBM) production in the Gujiao area, Shanxi province, China.Design/methodology/approachThis research was conducted mainly by the methods of thermogravimetry mass spectrometry (TG-MS) analysis, liquid nitrogen adsorption experiment and methane isothermal adsorption measurement.FindingsThe results can be concluded as that 400-700°C is the main temperature range for generating CH4. Pore volume and specific surface area increase with increasing temperature; however, the proportion of micro pore, transition pore and macro pore has no difference. The optimum temperature for enhancing CBM production should be letter than 600°C because the sedimentation of tar and other products will occupy some pores and fissures after 600°C.Originality/valueHere in, to accurately recognize the suitable maximum temperature for heating development, a method enhancing CBM production, TG-MS, was adopted to analyze the products and the weight loss of coals with different ranks in the Gujiao area at temperature of 30-1,100°C. And then the pore structure, porosity, permeability, methane adsorption capacity and thermal maturity of coals during pyrolysis were investigated with increased temperature from 30°C to 750°C. On these bases, the favorable condition for enhancing CBM production and the thermal evolution of coal were recognized.

Experimental study of the adsorption-induced coal matrix swelling and its impact on ECBM

Carbon dioxide (CO2) enhanced coalbed methane (ECBM) is an effective method to improve methane (CH4) production and this technology has already been used to increase gas production in several field trials worldwide. One major problem is the injection drop in the later period due to permeability decrease caused by coal matrix swelling induced by CO2 injection. In order to quantify the swelling effect, in this work, coal samples were collected from the Bulli coal seam, Sydney Basin and adsorption tests with simultaneous matrix swelling measurement were conducted. The adsorption and swelling characteristics were analyzed by measuring the adsorption mass simultaneously with the strain measurement. Then experiments were conducted to replicate the ECBM process using the indirect gravity method to obtain the swelling strain change with CO2 injection. The results show that the coal adsorption capacity in CO2 is almost two times greater than that in CH4, and nitrogen adsorption is the least among these gases. A Langmuir-like model can be used to describe the strain with the gas pressure and the swelling strain induced by gas adsorption has a linear relationship with gas adsorption quantity. Moreover, swelling strain increase was observed when CO2 was injected into the sample cell and the swelling strain was almost the sum of the strains induced by different gases at corresponding partial gas pressure.

The temperature effect on the methane and CO2 adsorption capacities of Illinois coal

The sorption capacity of coal is influenced by temperature, coal rank, mineral composition and moisture content. In the study, we experimentally measure the methane and carbon dioxide sorption capacity at various temperature for Illinois coal. A volumetric adsorption apparatus was employed to determine the excess gas adsorption capacity, and then the absolute adsorption capacity was estimated through the adsorbed gas phase density correction at each tested pressure. The adsorption isotherms were estimated for various temperatures from 283.15K to 343.15K. The experimental results indicated that both the methane and carbon dioxide adsorption capacities decrease linearly with an increase in temperature from 283.15K up to 323.15K, and the adsorption capacity reduction for CO2 is more significant than that for methane. When the temperature is equal to or greater than 323.15K, the adsorption capacities are independent of the temperature and remain constant for both gases. This means that there is a “critical temperature point” at which the influence of the temperature on the adsorption capacity vanishes, and the adsorption isotherms are very similar when the temperature is beyond the critical temperature point. The ratios of the CO2/CH4 absolute adsorption capacities vary from 2.62 and 3.80 with the tested pressures and temperatures.

Predictive models for thermal diffusivity and specific heat capacity of coals in Huainan mining area, China

Thermal properties of coal govern the thermal transfer in coal mass. Taking coal samples from Huainan mining area as the objects, thermophysical parameters (thermal diffusivity, specific heat capacity, and thermal conductivity) were measured from 30 to 300°C by LFA457 laser-flash apparatus. Predictive models for thermal diffusivity and specific heat capacity were then established. The results indicate that the thermal diffusivity of coal samples in Huainan mining area decreases with increased temperature, whereas specific heat capacity and thermal conductivity rise. The predictive models could accurately forecast the values and variations of thermophysical parameters for coal samples in Huainan mining area below 300°C. Furthermore, the modeling method is suitable for the establishment of models for coal samples in other areas. These will be beneficial for the understanding of thermal transfer in coal mass and shorten the testing time in the laboratory.

Early action on Paris Agreement allows for more time to change energy systems

The IMAGE integrated assessment model was used to develop a set of scenarios to evaluate the Nationally Determined Contributions (NDCs) submitted by Parties under the Paris Agreement. The scenarios project emissions and energy system changes under (i) current policies, (ii) implementation of the NDCs, and (iii) various trajectories to a radiative forcing level of 2.8 W/m2 in 2100, which gives a probability of about two thirds to limit warming to below 2 °C. The scenarios show that a cost-optimal pathway from 2020 onwards towards 2.8 W/m2 leads to a global greenhouse gas emission level of 38 gigatonne CO2 equivalent (GtCO2eq) by 2030, equal to a reduction of 20% compared to the 2010 level. The NDCs are projected to lead to 2030 emission levels of 50 GtCO2eq, which is still an increase compared to the 2010 level. A scenario that achieves the 2.8 W/m2 forcing level in 2100 from the 2030 NDC level requires more rapid transitions after 2030 to meet the forcing target. It shows an annual reduction rate in greenhouse gas emissions of 4.7% between 2030 and 2050, rapidly phasing out unabated coal-fired power plant capacity, more rapid scale-up of low-carbon energy, and higher mitigation costs. A bridge scenario shows that enhancing the ambition level of NDCs before 2030 allows for a smoother energy system transition, with average annual emission reduction rates of 4.5% between 2030 and 2050, and more time to phase out coal capacity.

How clean energy and efficiency can replace coal for a reliable, modern electricity grid

Aging coal-fired power plants are retiring all over the country, presenting the U.S. with an exciting opportunity to lead a global transition to a clean energy economy. The move away from coal begs the question: What will replace it? Energy efficiency, renewable energy and electric grid modernization should play an important part in replacing retiring coal capacity, and thereby mitigate the rush to build new natural gas plants.

Fractal analysis of high rank coal from southeast Qinshui basin by using gas adsorption and mercury porosimetry

In order to better understand the pore structure of high rank coal, low-temperature N2 isotherm adsorption/desorption and mercury porosimetry experiments were conducted on 20 coal samples from the southeast Qinshui basin. Fractal analysis was used to characterize the heterogeneity of pore structure. To obtain credible fractal dimension of pores, several models for calculating the fractal dimension were used and their calculation results were compared. The results show that fractal dimensions of pore surface and structure in adsorption pores can be obtain by Frenkel-Halsey-Hill (FHH) model from type A of N2 adsorption isotherms. The mercury intrusion data reflect the fractal information about seepage pores and partial transition pores. Because sensitivities of various models on pores with different widths are different, fractal dimensions obtained from different models based on mercury intrusion data are inconsistent. The coal samples can be divided into three types according to the crossplot of the volume percentage of seepage pore and the ratio of fixed carbon content and volatile content. For type I and II, Langmuir volume is positively correlated with the pore structure fractal dimension of transition pores and micropores. This shows that high pore structure fractal dimension of adsorption pores related to more small pores is conducive to coalbed methane (CBM) enrichment. The relationships between fractal dimension and permeability in type I and II are different, which may be related to volume and connectivity of mesopores and macropores. For type III, high ash content greatly reduces the adsorption and seepage capacity of coal.