Coal Ratio Research Articles

Spatial and temporal trends in δ66Zn and 206Pb/207Pb isotope ratios along a rural transect downwind from the Upper Silesian industrial area: Role of legacy vs. present-day pollution

Transect sampling is an under-exploited tool in isotope studies of atmospheric pollution. Few studies have combined Zn and Pb isotope ratios to investigate whether atmospheric pollution at a receptor site is dominated by a different anthropogenic source of each of these toxic elements. It has been also unclear whether pollution abatement strategies in Central Europe have already resulted in regionally well-mixed background isotope signature of atmospheric Zn and Pb. Zinc and lead isotope ratios were determined in snow collected along a rural transect downwind from the Upper Silesian industrial area (southern Poland). Spatial and temporal gradients in δ66Zn and 206Pb/207Pb ratios at four sites were compared with those of ore and coal collected in eight Czech and Polish mining districts situated at distances of up to 500 km. Snow pollution was extremely high 8 km from Olkusz in 2011 (1670 μg Zn L−1; 240 μg Pb L−1), sharply decreased between 2011 and 2018, and remained low in 2019–2021. Snow pollution was lower at sites situated 28–68 km from Olkusz. Across study sites, mean δ66Zn and 206Pb/207Pb ratios of snow were −0.13‰ and 1.155, respectively. With an increasing distance from Olkusz, the δ66Zn values first increased and then decreased, while the 206Pb/207Pb ratios first decreased and then increased. The δ66Zn values in snow plotted closer to those of Upper Silesian ores (−0.20‰) than to the δ66Zn values of Upper Silesian stone coal (0.52‰), showing predominance of smelter-derived over power-plant derived Zn pollution. The 206Pb/207Pb ratios of Upper Silesian coal (1.171) and Upper Silesian ores (1.180) were higher compared to those of snow. A206Pb/207Pb vs.208Pb/207Pb plot identified legacy pollution from leaded gasoline as the low-radiogenic mixing end-member. Across the transect sites, only the last sampling campaign exhibited a high degree of isotope homogenization for both Zn and Pb.

THE IMPACT OF THE IMPLEMENTATION OF ELECTRIC TRANSPORTATION ON THE UKRAINE’S INTEGRATED POWER SYSTEM FUNCTIONING

The rapid development of electric transportation in the world is due to significant economic and ecological advantages. The Ukrainian government also is planning to develop a national strategy and plans for the implementation of electric transportation. But the additional load poses challenges for Ukraine’s Integrated Power System. The analysis of the influence of electric transportation introduction on Integrated Power System operation would facilitate its effective government implementation. The aim of this paper was to estimate the effect of implementation volumes of electric transportation on the Integrated Power System operation, fossil fuel consumption, greenhouse gases, and pollutant emissions. A set of calculations was carried out for electric transportation volumes from 30 to 420 thousand electric vehicles by step 30 thousand based on a program and information complex simulating the operation of Ukraine's Integrated Power System, which has been developed in the Institute of General Energy of the National Academy of Sciences of Ukraine for the past few years. The calculations show that the share of nuclear power plants in Ukraine’s Integrated Power System increases according to the growth of the electric vehicles fleet. Therefore, it is expected to decrease fuel consumption as well as greenhouse gases and pollutants emissions. Fuel intensity is reduced by approximately 5% for electric transportation volume of 150 thousand and approximately 8% for 300 thousand. Specific emissions decrease faster due to the ratio of coal and gas power plants. Fuel intensity considerably varies from 0.07 (Summer) to 0.15 (Winter) tce/kWh. In general, the additional load from the implementation of electric transportation positively affects the energy system of Ukraine, increasing the efficiency of its operation by reducing specific fuel consumption. It should be noted that such trends are observed exclusively for Ukraine due to the specific structure of Ukraine's Integrated Power System with the large share of nuclear energy. Keywords: electric transportation, Ukraine’s Integrated Power System, greenhouse gas emissions, pollutant emissions.

Measuring carbon emissions performance of Japan's metal industry: Energy inputs, agglomeration, and the potential for green recovery reduction

This study measures the total factor carbnon dioxide (CO2) emissions performance of the metal industry, iron and steel, nonferrous metal, and metal processing industries in 39 Japanese prefectures from 2008 to 2019. The true fixed-effects panel stochastic frontier model identifies regional carbon efficiency as well as the inefficiency determinants. The main results are as follows. First, a decrease in the coal ratio and an increase in the electricity ratio in total energy consumption improves efficiency. This result suggests that electrification in the metal industry, especially conversion from blast furnaces to electric furnaces in the iron and steel industry, contributes to reducing carbon emissions. Second, industrial agglomeration improves carbon emissions performance in the metal industry. This implies that agglomeration and decarbonization policies focusing on there are more effective, rather than a uniform national policy. Third, compared to the cumulative CO2 emissions over the sample period, 49,017 × 103 tons, the cumulative CO2 mitigation potential is 29,703 × 103 tons, indicating that CO2 emissions can be reduced by 60.6% without affecting the output. Forth, to examine the green economic recovery with efficiency in Japan's metal industry after COVID-19, we present a simple scenario analysis where a k% replacement coal ratio with an electricity ratio in total energy consumption, assuming that each prefecture will achieve the maximum CO2 emission amount during the sample period. By replacing 10% of the coal ratio with the electricity ratio, CO2 emissions can be reduced by 23.0%. In the case of a 20% replacement, CO2 emissions can be reduced by 33.0%. Our results show that Japan's targets in the post-COVID-19 green recovery process should be a decrease in coal consumption, an increase in electricity, and industrial agglomeration.

The techno-economic-environmental analysis of a pilot-scale positive pressure biomass gasification coupled with coal-fired power generation system

Biomass gasification coupled with coal-fired power generation (BGCPG) is of great significance for alleviating energy shortages and environmental pollution. Here we propose, analyze and validate a BGCPG system under positive pressure for cleaner applications based on a pilot-scale fluidized bed gasification plant and discussed the possibility of higher economic output and operating stability with reduced pollution emissions. Then the effects of temperature, air equivalence ratio and operating pressure were experimentally investigated for parameter optimization. The processes under positive and negative pressure were simulated and compared based on the pilot-scale experimental data, and the effects of the mixing ratio and operating pressure were investigated. Furthermore, the economic and sensitivity analyses were conducted for both a traditional coal-fired power plant and simulated BGCPG systems. The results demonstrated that the gas calorific value, gas yield, and gasification efficiency increased with the gasification temperature increasing, whereas the opposite trend was observed for the gas calorific value with the air equivalence ratio increasing. The positive pressure operation had little influence on the gasification process. The flue gas flow rate increased, and the furnace temperature decreased with an increase in the mixing ratio of biomass and coal. The reduction in fuel NOx and SOx was caused by the decreasing coal content, whereas the decrease in thermal NOx and boiler thermal efficiency was due to the increasing exhaust temperature. Compared with functioning under negative pressure, operation under positive pressure at a 20% mixing ratio could effectively reduce the pollutant emissions of SOx, NOx and dust by 5.64%, 8.8% and 20%, respectively. The generation costs of the BGCPG system under negative and positive pressure conditions were 0.05593 $/kW·h and 0.05582 $/kW·h respectively, indicating that a positive operating pressure would increase the economic benefit of a 660 MW generator by 5.808 × 105 $/year. These findings suggest the effectiveness of clean power generation with a higher economy and lower pollution emissions.

Improving the top coal recovery ratio in longwall top coal caving mining using drawing balance analysis

ABSTRACT The recovery ratio of longwall top coal caving (LTCC) technology is an important measure of its effectiveness. However, the recovery ratio of single-opening sequential caving technology in thick and extra-thick coal seams needs improvement. To address this, an independent cluster-group caving technology is proposed in this study. Four numerical simulation experiments were conducted to compare the recovery ratio and drawing balance of four-opening independent cluster-group caving technology and single-opening sequential caving technology. Results show that the recovery ratio in four-opening independent cluster-group caving technology is approximately 6% higher than in single-opening sequential caving technology when the thickness of the broken gangue layer and the coal seam are the same. Additionally, a judgment formula for the broken immediate roof thickness is provided when the top coal recovery ratio is seriously affected. The independent cluster-group caving technology demonstrates stronger stability and better adaptability under different conditions, as its caving sequence can prevent larger thickness changes and gangue disturbances during the drawing process. Overall, this study highlights the potential of independent cluster-group caving technology to improve the recovery ratio of LTCC technology in thick and extra-thick coal seams.

A Study on the Co-Combustion Characteristics of Coal and Bio-SRF in CFBC

Bio-SRF based on livestock waste has low heating value and high moisture content. The concentration of toxic gases such as SOx, NOx, and HCl in the flue gas is changed according to the composition of fuel, and it has been reported. Therefore, the study of fuel combustion characteristics is necessary. In this study, we investigated combustion characteristics on the blended firing of coal and Bio-SRF (bio-solid refused fuel) made from livestock waste fuel in CFBC (circulating fluidized bed combustor). The raw materials for manufacturing Bio-SRF include agricultural waste, herbaceous plants, waste wood, and vegetable residues. Bio-SRF, which is formed from organic sludge, has a low heating value and a high moisture content. Bio-SRF of livestock waste fuel is blended with different ratios of coal based on heating values when coal is completely combusted in CFBC. In the result of experiment, the combustor efficiency of calculated unburned carbon concentration in the fly ash shows 98.87%, 99.04%, 99.64%, and 99.71% when the multi co-combustion ratio of livestock waste fuel increased from 100/0 (coal/livestock waste) to 70/30 (coal/livestock waste). In addition, the boiler efficiency is shown to be 86.23%, 86.30%, 87.24% and 87.27%. Through the experimental results, we have identified that co-combustion of livestock waste fuel does not affect boiler efficiency. We have systematically investigated and discussed the temperature changes of the internal combustor, compositions of flue gases, solid ash characteristics, and the efficiency of combustion and of the boiler during co-combustion of coal and Bio-SRF.

One-step preparation of coal-based magnetic activated carbon with hierarchically porous structure and easy magnetic separation capability for adsorption applications

Coal-based magnetic activated carbons (CMACs) were prepared from Zhundong coal in the presence of various Fe-based additives by fast one-step physical activation method. The roles of types and doses of Fe sources for pore structures and magnetic properties of the resulting CMACs were systematically investigated. Fe species in coal promoted the development of mesopore structures, and AC-FC-3 derived from FeCl3-loaded coal (3% Fe content) possessed hierarchical pore structure with highest micropore and mesopore volumes up to 0.282 cm3·g−1 and 0.222 cm3·g−1, respectively. Considering the minimum dose of additives, the CMACs loaded a trace amount of reduced iron powder (0.5% and 1% weight ratios of coal) were prepared, and had improved micropore and mesopore structures compared with AC derived from the demineralized coal. Meanwhile, strong magnetic iron oxides (Fe3O4 and γ-Fe2O3) were generated during CO2 activation process. The CMACs derived from different Fe sources loaded coal samples with same Fe content (3% weight ratio of coal) had saturation magnetizations of 0.55–14.26 emu·g−1. Evaluated as adsorbents for Methylene Blue (MB) removal, the CMACs with hierarchical pore structure exhibited better MB adsorption capacities up to 120.3 mg·g−1. Furthermore, the magnetic properties of CMAC could accelerate the solid–liquid separation with an applied magnetic field and improve recovery efficiency of the adsorbent.

Predictive Modeling of the Hot Metal Sulfur Content in a Blast Furnace Based on Machine Learning

The sulfur content of hot metal in a blast furnace is an important index that reflects the production effects and quality of the hot metal. Establishing an accurate prediction model for hot metal sulfur content can guide the production process. In the present study, the blast furnace production data were collected and then preprocessed using box plotting. Cross-validation was used in the training process of the model to improve the generalization performance and robustness of the model. Two models for predicting the sulfur content in hot metal were established based on extreme gradient boosting (XGBoost) and multilayer perceptron (MLP) algorithms. The results show that coal consumption (CC), coal ratio (CLR), and sinter consumption (SC) are all positively correlated with hot metal sulfur content. The oxygen enrichment rate (OER) was negatively related to hot metal sulfur content. Both the extreme gradient boosting (XGBoost) and multilayer perceptron (MLP) models predicted hot metal sulfur content effectively; however, the extreme gradient boosting (XGBoost) model had a higher hit rate, accuracy, and stability, with the hit rate achieving 95.07%.

Variation laws of CO2/CO and influence of key active groups on it during low-temperature oxidation of coal

The CO2/CO ratio produced by the reaction of active groups in coal with oxygen can truly reflect the state of coal spontaneous combustion. However, there are various paths for coal to produce CO and CO2, including oxidation, pyrolysis, and desorption. Gas production from coal desorption and pyrolysis influences CO and CO2 produced from oxidation, especially pyrolysis manifests as the production of gas and active sites. For this reason, a method that can exclude the interference of gas production from desorption and pyrolysis is designed, and based on this method, the variation of CO2/CO ratio of coal under different pathways is studied. The active sites generated from coal pyrolysis was also investigated using pyrolytic coal, and the intrinsic causes of CO2/CO ratio variation were studied based on microanalysis and model compounds. The experimental results show that the proposed method can effectively eliminate the effect of desorption and pyrolysis, and the CO2/CO ratio produced from oxidation is about 3. The active sites generated from coal pyrolysis strongly affect the concentrations of CO and CO2 at the beginning of oxidation, but they barely influence their ratio which is always about 3. The intermediates product by the oxidation of methylene linked to multiple benzene rings are the same precursor to produce CO and CO2, which are the main cause of a CO2/CO ratio of 3. The gradual involvement of different active groups in the reaction considerably affects the ratio of CO2/CO produced by oxidation path. Therefore, the low-temperature oxidation to produce CO and CO2 can be divided into three stages, which provides theoretical support for predicting the state of coal spontaneous combustion based on the change law of CO2/CO ratio.

Numerical Analysis of Natural Gas Injection in Shougang Jingtang Blast Furnace

A static model of blast furnace operation of natural gas (NG) injection was developed. The effect of NG injection on the raceway adiabatic flame temperature, the amount and composition of bosh gas, the direct reduction degree and fuel ratio were studied. The results showed that under no thermal compensation, the heat loss of the whole blast furnace increases, which means the heat surplus of the whole furnace is sufficient. However, the heat in the high-temperature zone of the blast furnace is insufficient, showing the characteristics of “cold at bottom and hot at the top”. Based on the comparison of heat loss in the high-temperature zone after NG injection with the reference condition, if the heat loss is consistent with the reference case, the suitable NG injection volumes are 17.3, 34.6, 52 and 69.3 m3/t when the coal ratio is reduced by 20, 40, 60 and 80 kg/t, respectively. With the increase of the suitable NG injection volumes, the adiabatic flame temperature gradually decreases, the amount of bosh gas slightly increases, and the overall fuel ratio reduces gradually. The effect of other thermal compensation operations, such as increasing blast temperature and addition of oxygen on the NG injection, were also investigated. The findings of this work can be used as a theoretical basis to guide plant operations for NG injection in blast furnaces.

Bonding mechanism of binder and low-rank coal during carbonization

Low-rank coal is rarely used in the industry of carbonized briquette due to its poor cohesiveness. In order to replace lump coal and utilize low-rank pulverized coal as much as possible in a carbonized briquette process, washing oil residue (WOR) was used as an enhanced binder to enhance the bonding strength of resulted carbonized briquette. The effects of blending ratio and carbonization temperatures on binding strength were investigated, and moreover, a reasonable bonding mechanism was deduced. The results showed that the best crushing strength was obtained when the weight ratio of WOR and low-rank coal is 3:7 at 800 °C, and its crushing strength of M25 (M25) can reach to 97%, while the thermoplastic properties of WOR is thought to be responsible for the obtained good crushing strength, where WOR can be softened and coated on the surface of coal particles during carbonization, and then a coal-binder interface can be formed, resulting in the loose inert coal particles can be combined and the strength of coke is improved significantly.

Investigation of the co-processing technology of crude oil and coal and its deployment

Abstract The effect of process conditions on the co-processing technology of crude oil and coal was investigated. Crude oil/coal matching performance, swelling degree, crude oil/coal slurry viscosity-temperature characteristics and process parameters were obtained via the laboratory scale and pilot scale studies. The optimum reaction temperature of the co-processing was 445~450 oC, the pressure was 19 MPa, the catalyst addition was 3 wt.%, the reaction time was 2 h, and the ratio of hydrogen to crude oil was 1500 (V/V). Furthermore, the co-processing technology including catalyst and corresponding equipment based on the slurry bed hydrogenation were developed. By using this co-processing technology, the feed ratio of crude oil and coal can be 1:1, the coal conversion rate can be over 99%, the light oil (oil and aromatics) yield was over 70%, and the end products were gasoline, diesel, jet fuel, aromatics and LPG. The product quality meets the Euro V standard, whilst aromatics accounted for 48% of the light oil. So it was proved to be feasible to co-refine crude oil and coal at a ratio of 1:1. What’s more, the slurry bed hydrogenation plant and its equipment were tested for long-term operation, and it has been proved that this co-processing technology could be deployed as large-scale industrial application.

Evolution of Chemical Component and Physical Properties of Datong Long-Flame Coal After Superheated Water Vapor Pyrolysis

ABSTRACT Datong long-flame coal from China was pyrolysis with superheated water vapor at 300°C to 536°C. Chemical and physical changes of long flame coal, including composition, weight loss, pore fracture structure, density, and water absorption were tested, and the qualitative and quantitative relationships among these changes were analyzed. superheated water vapor pyrolysis removes moisture and volatile components from long flame coals and increases the fixed carbon content. After superheated water vapor pyrolysis, the O/C and H/C atomic ratios of long flame coal decreased due to the decomposition of oxygen-containing functional groups and chain aliphatic hydrocarbons. superheated water vapor pyrolysis increased the porosity of long flame coal by material removal and matrix fracture. Material removal occurs throughout the pyrolysis process but matrix fracture occurs only at the initial stage of the conversion of solid organic matter to oil and gas products. The expansion of pore fractures in long flame coal caused a significant decrease in apparent density and an increase in water absorption. Quantitative analysis revealed the forced water absorption of long flame coal was quadratically polynomial with respect to porosity.

Molecular dynamics and steady-state process simulation coupled research on CCLG system design for cleaner production of EG

BackgroundThe CO2 capture technologies such as chemical-looping gasification (CLG) and reformation (CLR) receive more and more attention under the globally warming environment. In this paper, the mechanism of coal chemical-looping gasification (CCLG) process with copper-based oxygen carrier is analyzed by molecular dynamics (MD) simulation and steady-state process simulation to produce high purity ethylene glycol (EG). MethodsFirstly, the effect of temperature and mass ratio of coal and CuO on CCLG process are investigated with gasification experiments. Secondly, the MD simulations in ReaxFF force field are performed in purpose of obtaining the micro-level information and cross-reference with experimental results. Finally, an innovative process to produce high purity EG is designed based on CCLG process from the above simulations and experiment results. Significant findingsThe results of gasification experiments show that the optimal reaction temperature is 850°C and the optimal mass ratio of coal to CuO is 1:1.5. The results obtained from the MD simulations are found accordant with the experimental results. The EG targeted CCLG process basically meets the mass ratio required by the production of EG, and the CO2 emissions of the whole process is only 0.018 kg-CO2/kg-EG.

An Experimental Study on CO2 Displacing CH4 Effects of Different Rank Coals

In order to study the effect of different rank coals on the displacement of CH4 by CO2 and prevent the gas-related disasters, a series of experiments were carried out. For this purpose, we selected low-rank lignite raw from Datong coalfield of Shanxi Province, medium-rank bituminous coal raw from Xutuan coalfield of Anhui Province, and high-rank anthracite raw coal from Yangquan coalfield of Shanxi Province. The results showed that (1) the shape of the displacement adsorption curve of the mixed gas and the shape of the single-dimensional adsorption curve of the pure gas are both steep at the beginning, with the increase of the pressure, the curve becomes more and more gentle. The difference is that it is lower than the single-dimensional gas adsorption curve. (2) The separation factor in the coal samples used in the experiment shows a trend of first decreasing and then increasing with the decrease of coal rank. The displacement factor has the same trend as the separation factor of each coal rank, which is Z i j anthracite > Z i j lignite > Z i j bituminous coal . (3) The amount of displaced CH4 in the displacement/adsorption process has enhanced with the increase in pressure, and the trend for different coals is Q Z bituminous coal > Q Z anthracite > Q Z lignite . In addition, displacement showed the order ƞ lignite > ƞ anthracite > ƞ bituminous coal . The injection ratio of bituminous coal and anthracite decrease with the increase in pressure, while that of lignite increase first and later decreased. (4) In gas injection displacement, on the long time, the displacement effect of high coal rank is better than that of low coal rank.

Damage characteristics of pulverized coal under different gas pressures in coal and gas outbursts

ABSTRACT Coal and gas outbursts are complex dynamic phenomena and are highly hazardous. This article established an experimental system to research the damaging effect of gas on particulate coal during coal and gas outbursts, which replicated the outburst scenario by instantaneously releasing different-pressure gas. The results show that the higher the gas pressure is, the larger the new surface area is, and the gas damages the pulverized coal more drastically. The mass ratio of new granular size coal is between 8–27%. The surface area increased significantly (73.0%-245.2%). The mean order of increasing surface area is SC (1.102 m2)> DC (0.9875 m2)> SN (0.8999 m2)> DN (0.8369 m2), which indicates that the extent to which gas destroys particulate coal is inversely proportional to the solidity coefficient and positively proportional to the adsorptivity. The ability of weakly adsorbable gases to break particulate coal is more affected by gas pressure. The degree of breakage of low-firmness coals is more responsive to gas pressure. The percentage of coal mass broken by gas is positively correlated with gas pressure and adsorptivity and negatively correlated with the firmness coefficient. Finally, the quick release of gas occurs in three stages: an acceleration section (0–0.05 s), a high-speed section (0.05–0.15 s), and a deceleration section (after 0.15 s).

Co-firing of high-ash discard coal and refuse-derived fuel - ash and gaseous emissions

This research focuses on the co-firing of discard coal with refuse-derived fuel (RDF) to utilize this abundant resource in South Africa for energy generation and reduce the volume of waste disposed of at landfills. The potential of a coal with a high ash content (> 40%), which is a grade used in some power stations in South Africa, and its combustion compatibility with two different RDFs in terms of emission reductions has been established. Gaseous emissions and ash residues from the combustion and co-combustion of the coal, two different RDFs and coal/RDF blends of different proportion were analysed. One of the RDF samples contained mostly paper (PB) and the other mostly plastic (PL). Co-combustion ash from the discard coal and RDFs showed a decrease in chloride and alkali metal contents as the coal ratio in the blend increased. The slagging propensity of the co-fired blends was found to be very low, while the propensity for fouling decreased from high to medium for all the blends with < 75% RDF. Co-combustion of RDF with coal showed a decrease in SO2 emissions from 387 ppm (discard coal) to 50 ppm for the sample containing 25% coal discard plus 75% PL. A 15% PL to 85% coal blend also reduced NOx emissions from 145 ppm (100% PL) to 88 ppm. The lowest CO2 emission observed was 6000 ppm for the blend of 85% discard coal plus 15% PB. It was established that the most favourable fuel blend that can produce the lowest sulphur emissions if used for power generation is the 25% coal discard plus 75% PL sample.

Eco-Energetic Efficiency – Comparative Analysis of Steam Power Plants Versus Micro Hydropower Plants

Abstract Global warming and climate changes, as well as the contribution of fossil fuel to the accentuation of these phenomena are realities almost unanimously accepted. Therefore, the reduction of the coal ratio in the energy mix and its replacement with forms of energy without emissions is being discussed more and more frequently. Nevertheless, it is important that the impact generated in the environment by the alternative energy sources related to energy production does not exceed the shortcomings created by the steam power plants, as it seems to be the case of micro hydropower plants (MHC) located on the superior flow of mountain rivers. As it is difficult to compare the impact on the environment generated by two completely different energy sources, two indictors were defined and used in this sense that consider their ecological, economic and social performance. As a result of the evaluation of the impact and of the comparison criteria, the two indicators were used in the two chosen case studies, resulting that a steam power plant that operates in cogeneration has a superior eco-energy efficiency to a micro hydropower plant. Thus, following the carried-out studies, we believe that MHC can be recommended only under special circumstances such as providing electric power to areas difficult to reach without them injecting the produced energy into the National Energy System (SEN).

Pollutant emission and attrition performance of low calorific blended coals during co-combustion in fluidized bed

The co-combustion technology in the fluidized bed is usually used for the utilization of low-rank coals. The pollutant emission and attrition of coal particles, which are subject to bed temperature, excess air coefficient, mixture ratio and particle size, cannot be ignored. In this work, a pyrolysis-combustion-fragmentation method was presented to study the attrition and the quantitative fragmentation indexes of different coal blends, followed by the experimental investigation of the blended coal's gaseous pollutant emissions in a fluidized bed combustion reactor. As demonstrated by the experimental results, the emission of N2O decreases with increasing the bed temperature from 800 to 850 °C, while attrition rate increases with the bed temperature. Increasing the excess air coefficient is conducive to reducing CO2 and SO2. Considering the low flue gas emission and the attrition behavior, the mixed ratio of raw coal, coal gangue and coal slime at 20:60:20 may be an appropriate choice for their co-combustion in a fluidized bed reactor. The main reason for the fragmentation of blended-coal particles is the primary fragmentation. This study is useful for optimizing the condition of blended coal’s combustion in CFB boiler.

Evaluation of the Energy Consumption and Fractal Characteristics of Different Length-Diameter Ratios of Coal under Dynamic Impact

Coal samples having the same diameter (50 mm) and different length-diameter ratios (l/d), i.e., 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, and 1.0 were tested under dynamic uniaxial impact compression using the Split Hopkinson Pressure Bar (SHPB) experimental system. This study evaluates: (a) The effects of l/d on the energy consumption law and fractal characteristics of coal crushing; (b) The effects of l/d and stress balance on energy dissipation; (c) The effects of l/d and energy consumption density on the fractal characteristics of coal crushing. The findings under different l/d are as follows: (1) The coal samples show similar stress–strain curve shapes in stages including elastic, plastic, and failure stage, which is an “open” shape, the proportion of plastic stage increases, and strain-softening occurs; (2) The dynamic compression dissipation energy and energy consumption ratio of coal shows the same trend, showing two stages with the increase of length-diameter ratio, which increases linearly in the first stage and overall decreases step-by-step; (3) The average particle size increases while fractal dimension of fragmentation decreases linearly, which endorses the decreasing trend of fragmentation degree; (4) It is determined that there is a power relationship between fractal dimension and energy dissipation density; (5) A new index Crushing Density Energy Efficiency (CDEE) is proposed, which can be used to characterize the rock-breaking efficiency of crushing energy consumption under different conditions. This index is inversely proportional to l/d. The research results can provide a basis for the design of top coal caving mining, and the determination of blasting parameters.