Raw Coal Research Articles

Orthogonal Experimental Study on the Ratio of Similar Materials of Coal Body

According to the coal samples collected from Zhaogu No.2 Coal Mine as raw coal samples, the similar materials of coal body were studied by using river sand, pulverized coal, Portland cement and calcium carbonate. The orthogonal test method of four factors (bone glue ratio, aggregate ratio, rubber ratio, water mixing rate) and three levels was used to obtain the physical and mechanical parameters such as density, uniaxial compressive strength, elastic modulus, cohesion, internal friction angle and tensile strength of coal similar materials. The range analysis method was used to obtain the key influencing factors and variation rules of the physical and mechanical properties of coal similar materials. Finally, the method of multiple linear regression analysis was used to obtain the similar material ratio that was most consistent with the mechanical properties index of raw coal. The ratio of calcium carbonate: cement: river sand: coal powder: water = 1: 5: 0.9: 5.9: 3.2. The density error, compressive strength error, elastic modulus error and cohesion error of coal sample and raw coal are small, which proves that the similar material is similar to the mechanical properties of raw coal, and provides guidance for subsequent research.

Heat Storage Using Solar Pond Technology and Post-Mining Brine – Preliminary Analysis

This paper presents an analysis of the feasibility of using solar pond technology for thermal energy storage, particularly using post-mining brine water. Solar ponds are not considered as a potential heat/cool storage technology for heating systems mainly because of the requirement to constantly supply the pond with fresh water and salt solutions, which involves significant investment and operating costs. On the other hand, brine water from the dewatering of deep mines is a by-product of the extraction of various raw materials, including copper, iron, non-ferrous metals, and coal. The treatment of these waters yields highly concentrated salt solutions, which, when combined with solar pond technologies, can lead to strong synergies. The article presents preliminary selected simulation results of the solar pond system and presents a proposal for its systemic use. A forecast of the potential energy, environmental, and socio-economic benefits of the technology is also presented.

Interpreting crystallographic and microcrystalline structural effect for demineralization of low-grade thermal coal in multi-stage chemical leaching: A cleaner combustion approach

Chemical leaching is one of the most efficient methods for improving low-grade coal due to its ability to remove both inorganic and organic minerals economically. This study examined the qualitative demineralisation using the XRD and FTIR analyses. Moreover, microcrystalline analysis was investigated by analysing the Micro-Raman spectra, and ash composition was analysed using XRF Spectroscopy analysis for coal samples. Furthermore, a correlation was established between a Raman parameter (AD/AG) and a crystallite parameter (Lc). The demineralisation mechanism was postulated in light of the findings to explain how significant impurities (SiO2 and Al2O3) with iron-bearing elements (Fe2O3 and FeS2) were curtailed during multi-stage leaching. The maximum deashing and demineralisation were obtained by treatment with 40% (w/v), i.e. 10 M NaOH, followed by HCl with HNO3 solution in a 3:1 ratio, with an average particle size of 180 μm. 79% ash reduction and 48% enhancement in GCV were achieved compared to raw coal.

Geochemical Characterization of Sedimentary Materials (Limestone, Gypsum, Coal, and Iron Ore) along the Nile River Basin, South Wollo, Ethiopia

Sedimentary rocks are produced by the weathering of preexisting rocks and the subsequent transportation and deposition of the weathering products. Among the sedimentary rocks, especially limestone is a crucial raw material for cement production. The purpose of this study was to characterize the valuable industrial raw materials, limestone, gypsum, clay, coal, and iron ore, along with the Nile River basin. For sample collection, a random sampling method was applied. Different analytical methods were carried out for complete oxide analysis such as LiBO2 fusion, HF attack, and gravimetric, calorimetric, and atomic absorption spectroscopy (AAS). The percentages of oxides detected in this study are in the range of acceptable values (high content of CaO ranging from 47.3 to 50.4% and less content of SiO2 ranging from 8.72 to 11.24%) for good proposal as a potential raw material for cement production. The most dominant and wide-range coverage of limestone along with the Nile basin, particularly near Arsema Monastery, was found as matured limestone. The petrographic analysis of gypsum, sandstone, and clay samples indicated that all the samples taken from Wegidi revealed that the high percentage of gypsum ranges from 90 to 95%. Sandstone is dominantly preset in Kelala to Jamma road along with Beto River with high content of SiO2 ranging from 61 to 95%. The results of this study indicate that the treated coal samples are relative to high calorific value, fixed carbon, and low ash content. Coal and iron ore from Jamma revealed that high calorific value is 4929.24 and hematite content is 52.2, respectively. The result of this study revealed that a huge amount of limestone reservoir is detected in Borena Wereda, Amhara, Ethiopia.

Study on the oxidized gas production characteristics and spontaneous combustion tendency of pre-oxidized water-soaked coal in lean-oxygen environments.

The oxidation characteristics and spontaneous combustion (SC) tendency of raw long-flame coal (RC), water-soaked 200-day coal (S200), pre-oxidized water-soaked coal at 200°C (O200S200), and pre-oxidized soaked coal at 300°C (O300S200) in an oxygen-poor environment were investigated using a programmed warming system. The results show that pre-oxidation water-soaked treatment (PWT) promotes the coal-oxygen complex reaction and increases the rate of coal oxygen consumption (OCR) and the rate of carbon and oxygen compound production. The rate of CO and CO2 production of the water-soaked (WS) coal increased by 0.329mol·(cm3·s)-1 and 0.922mol·(cm3·s)-1, respectively, compared with that of the original coal sample. PWT reduces the activation energy of coal in the low-temperature oxidation stage (the maximum difference can be up to 110.99kJ/mol) and enhances the oxidizing and heat-releasing capacity. There was a synergistic effect between the pre-oxidation (PO) and WS treatment, and the lowest comprehensive determination index of the SC propensity of coal in O200S200 samples was 831.92 which was 4.72 lower than that of RC samples, presenting a more SC tendency. Low oxygen concentration has an inhibitory effect on the oxidation characteristic parameters of coal, and the apparent activation energy of the low-temperature oxidation stage of pre-oxidized water-soaked coal (PWC) increased to 206.418kJ/mol at 3% oxygen concentration. The lower the oxygen concentration of the anoxic environment, the lower the risk of SC of the coal samples. The results of the study can provide theoretical guidance for the identification and prevention of SC disasters in coal seams with shallow burial and close spacing.

Effects of Adsorption and Desorption of Low-Boiling-Point Total Hydrocarbon Gases on Activated Carbon.

In this study, we selected materials that efficiently adsorb total hydrocarbons (THCs) from petrochemical storage facilities and applied four types of activated carbons to adsorb THCs to evaluate their properties. Four gases with low boiling points, namely, ethylene, ethane, propylene, and propane, generated via petrochemical storage facilities, were selected and mixed to a constant concentration with four types of materials and used to investigate the adsorption capacities and desorption properties. The adsorbents comprised two raw materials and two chemically activated materials. The specific surface areas of activated palm (2085 m2/g) and coal (1752 m2/g), which are chemically activated carbons, exhibited a twofold increase compared to those of raw palm (1232 m2/g) and coal (946 m2/g). Thus, we identified the correlations between the physical properties of the activated carbon adsorption materials and their adsorption capacities for four low-boiling-point THCs generated by petrochemical storage facilities.

Evaluating coal pore structure and gas sorption-diffusion behavior alteration induced by ultrasound stimulation using sorbing tests and matrix diffusion modeling

Coalbed methane development has great significance to ensure the safe and efficient coal mining, clean energy supplementation and carbon emission reduction. Ultrasound stimulation can effectively modify the coal pore/fracture structure and change the gas ad/de-sorption process and diffusion kinetics characteristics, thus altering gas production for coal deformations. This study estimated the pore structure damage and gas sorption-diffusion of coal before and after ultrasound stimulation with gas sorption tests and gas sorption-diffusion modeling. The results show that the maximum nitrogen adsorption capacity increases by 181.2%–218.9% in coal after ultrasound stimulation, and the pore volume and specific surface area of the ultrasound stimulated coals are 1.5–2.0 times and 5.6–7.6 times of those of the raw coals, respectively. Ultrasound stimulation (20 kHz) has a significant modification effect on pores with size of 2∼50 nm. Fractal analysis of pore structure indicates that the pore surface roughness reduces after the ultrasound treatment, and the development of coal pores has become more complex, and the pore heterogeneity has increased with ultrasound stimulation. The sorption tests and gas sorption-diffusion modeling indicate that gas sorption and diffusive transportation increases after the ultrasound treatment, especially in the initial period. In the initial pressure boosting stage (0∼0.5 MPa), the cumulative methane adsorption amount increases by 20.94%, the diffusion coefficient K increases by 17.32%, and the gas adsorption constant b increases by 62.66%, which is attributed to the “pore-forming” and “pore-expanding” effect caused by ultrasound vibration and cavitation. Ultrasonic stimulation technology has a special improvement performance on coal seams with poor matrix gas deliverability, which is beneficial for the life cycle production enhancement of coalbed methane wells.

Forecasting China’s CO2 emissions and identifying key drivers: an application of the improved RFAGM model and LMDI decomposition methods

ABSTRACT China, the world’s largest CO2 emitter, has pledged to reduce its carbon intensity by 18% by 2025, which requires accurate forecasting of its emissions and their drivers. However, existing gray models have limitations in dealing with fluctuating data or long-time series data, and they often suffer from overfitting and poor generalization ability. Moreover, there is a lack of research and judgment on the future changes of emission drivers. To address these issues, this study proposes a fractional order gray adaptive rolling model (RFAGM(1,1)) that optimizes the background generation and incorporates the rolling mechanism. We apply RFAGM(1,1) to forecast China’s emissions, GDP, population, and consumption of raw coal, crude oil, and natural gas from 2020 to 2025. Our results show that RFAGM(1,1) achieves significantly higher accuracy than standard gray models, except for population. The projections indicate that China will meet the 18% carbon intensity reduction target by 2025. Furthermore, the LMDI decomposition reveals that economic growth and population changes have positive cumulative impacts on emission growth (245.68% and 11.95%, respectively), while energy intensity and structural changes have negative cumulative impacts (−151.60% and −6.02%, respectively). The improved forecast enables the evaluation of climate policies, while the factor analysis provides valuable insights for developing evidence-based strategies to achieve China’s carbon peaking and neutrality goals by 2030/2060.

Mechanism of measuring ash with low-energy gamma rays for equal coal seam thickness

ABSTRACT Considering the issues related to significant fluctuations and errors in the measured data of the dual-energy gamma-ray online ash analyzer caused by various external factors, this study investigates the impact of factors such as the distance between the detector and the radioactive source, coal seam thickness, moisture content, and particle size range on ash measurements. Additionally, a novel low-energy gamma-ray online ash measurement device is proposed, which ensures uniform coal seam thickness. By utilizing this device, the coal samples subjected to measurement exhibit characteristics such as small particle size, a narrow range of particle sizes, a smooth coal flow surface, consistent coal flow density, a fixed distance between the coal seam and the detector surface, and constant coal seam thickness. These conditions collectively provide optimal circumstances for accurate low-energy gamma-ray ash content measurement. Experimental results indicate that during the separation of Suntuan: Tongting raw coal, the average discrepancy between the measured ash content and the assay ash content was only 0.33%, and the standard deviation of the measured ash content was significantly lower than that of the assay ash content. Specifically, when separating Suntuan: Tongting raw coal, the standard deviation reached its minimum at 0.16%. Comparatively, the low-energy gamma-ray online ash measurement device outperforms the dual-energy gamma-ray online ash analyzer, exhibiting enhanced accuracy and stability in ash measurements, thereby better fulfilling the requirements of daily production.

Study on the Properties of Proanthocyanidins Modified Temperature Sensitive Gel Composite Inhibitor for Inhibiting Coal Spontaneous Combustion

ABSTRACT To address the disadvantages of the single inhibition effect, poor inhibition effect and short inhibition life of the inhibitors used in coal mining, a temperature-sensitive gel composite inhibitor was developed in this study. Polyacrylic acid (PAA), n-isopropylacrylamide (NIPA) and proanthocyanidin (OPC) were used as raw materials. The inhibition property and mechanism of the temperature-sensitive gel composite inhibitor were studied using scanning electron microscopy (SEM), infrared spectroscopy (IR), temperature sensitivity tests and thermogravimetric analysis (TGA). The results indicate that OPC/P(NIPA-co-AA) is able to fill the coal interstitial space and isolates oxygen to weaken the oxygen-coal reaction. The absorption peak of the chemically stable ether bond increases, and the content of methyl and methylene groups that can easily react with oxygen decreases in the OPC/P(NIPA-co-AA)-inhibited coal sample, indicating that the stability of the inhibited coal sample is improved. The sensitive temperature of OPC/P(NIPA-co-AA) is around 55°C, and the composite inhibitor reduces the temperature of water loss when the coal heat storage reaches the sensitive temperature, which improves the physical inhibitory effect. The ignition temperature of the OPC/P(NIPA-co-AA)-inhibited coal sample is 6.94°C higher than that of the raw coal, whereas the oxidation reaction of the OPC/P(NIPA-co-AA)-inhibited coal sample is more difficult. The temperature-sensitive gel composite inhibitor exhibits good inhibitory performance in both physical and chemical aspects, and it can significantly inhibit the spontaneous combustion of coal.

Deep eutectic solvent assisted swell and highly efficient catalytic pyrolysis of raw coal

The development of catalytic pyrolysis strategy is the key to the efficient utilization of raw coal. Herein, a novel microwave-assisted deep eutectic solvent (DES) swelling strategy was used to catalyze the pyrolysis of Naomaohu coal. The multifunctional FeCl3-Levulinic acid DES was synthesized, it could not only act as the solvent to swell coal, but to highly efficient catalyzed the pyrolysis of the swelled coal. During the process of microwave swelling, DES enhanced the induced polarization of unsaturated bonds, destroyed the weak intermolecular chemical bonds, increased the spacing of aromatic layers and reduced the particle size of raw coal, thus exhibiting a superior swelling effect. Notably, with the catalytic action of DES, it effectively promoted the conversion of coal as well as the escape of light components in the pyrolysis process. Based on the advantages of DES, the pyrolysis tar yield increased significantly (from 11.85% to 17.63%) and the yield of Benzene-Toluene-Xylene was as high as 11.31% in the tar and its content was 14.48 mg g−1. The light component (BP ≤ 360 °C, 67.50%) and light oil (BP ≤ 170 °C, 42.00%) of the tar reached high levels. What’s more, the pyrolysis behavior and kinetics results indicated that the pre-exponential factor was 2.61 × 1016 min−1 and the average apparent activation energy was 267.39 kJ mol−1. The proposed efficient method is expected to provide novel strategy for the swell and catalytic pyrolysis of raw coal using diverse multifunctional DES.

Compositional analysis of dark colored particulates homogeneously emitted with combustion gases (dark plumes) from brick making kilns situated in the area of Khyber Pakhtunkhwa, Pakistan

In Pakistan raw coal and a little quantity of waste plastics are burnt to sustain high temperature inside brick making kilns. The gaseous emissions of the kilns contain a considerable amount of darkish colored particulates. It is currently believed that the plastic burning produces these particulates. Advanced characterization instruments, such as a scanning electron microscope, energy dispersive spectroscopy, X-ray fluorescence, X-ray diffractometer, surface area analyzer using nitrogen gas adsorption isotherms, and thermogravimetric analyzer, were used to find out the chemistry and physics of the particulates. At a magnification of 30,000x, the SEM picture shows masses that are roughly roundish in shape and their size is in between 0.1 to 0.5 microns. The elements detected in these particles are carbon, oxygen, and sulfur (EDS analysis), or in other words, these elements are a typical composition of raw coal. This elemental analysis suggest that fine coal particles come out with usual combustion gases and these emitted particulates are not plastic combustion product. To strengthen this finding, the sample when calcined discarded a significant amount of sulphur oxides species, as determined in the XRF study by noticing a considerable decrease of sulphur content in the calcined particles, suggesting that the particles are actually a coal. The N2 isotherm graph reveals that the light weight flying coal particles has a very low surface area. Additionally, the XRD and TGA studies supports the conclusion that these dark colored particulate emissions are primarily fine coal particles (cenosphere).

Relevance evaluation and spatial differentiation analysis between green development and environmental footprint in China's three typical mega-urban agglomerations

This study constructs a comprehensive framework for exploring the relevance between green development level and environmental footprint in three typical mega-urban agglomerations of Yangtze River Economic Belt (YREB) of China. This framework consists of the three-dimensional ecological footprint (EF3D), carbon footprint (CF), cloud model, and Environmental Kuznets Curve (EKC). Results reveal that there exist an increased EF3D and a decreased ecological carrying capacity in the YREB, with annual change rates of 4.45% and −0.46%, respectively. According to ecological footprint depth, 24.61, 17.59, and 30.89 times of current local land area are required for supporting regional development in the YREB upstream, midstream, and downstream urban agglomerations, respectively. There is an increased tendency in CF, especially in the midstream urban agglomeration with an increased rate of 5.25%. Carbon pressure is mostly contributed by crude oil (34.47%) and raw coal (31.55%). Moreover, green development level in the YREB shows an increased tendency with an annual rate of 0.5%, and that in the downstream urban agglomeration is generally greater than other areas. The relevance between green development level and environmental footprint is mainly inverted U-shaped or inverted N-shaped EKC types. CF in the YREB and its upstream urban agglomeration begins to decline when green development levels are 3.44 in 2020 and 3.26 in 2020, respectively. EF3D in the midstream urban agglomeration starts to fall when green development level reaches 3.36 in 2019. EF3D from cultivated land and fossil fuel land has a positive impact on the improvement of relevance. Overall, the developed framework can be applied to areas where there is a conflict between economic development and environmental protection. Furthermore, dynamic prediction of green development level and environmental footprint as well as their correlation mechanism under different scenarios are still required for enhancing environmental sustainability and promoting regional coordinated development.

DETERMINATION OF THE MASS BALANCE OF HIGH-CARBON FERROCHROME IN A SUBMERGED ARC FURNACE

In this study, it is aimed to establish one-day mass balance of the materials entering into and leaving from a submerged arc furnace (SAF) where high-carbon ferrochrome is produced in it. The SAF is used in a plant located in Elazig, Turkey. For this purpose, measurements were taken from the SAF during one month by obtaining the necessary permits from the plant. In addition to these measurements, chemical reactions in the SAF are defined based on the information obtained from the literature and the plant. Chrome ore and rich slag are raw materials for furnace; as auxiliary raw materials, coke, coal, electrode paste, quartzite, and bauxite are fed. The product and the waste coming out of the SAF are high-carbon ferrochrome, slag, flue gas, and fly ash. Samples were taken from each raw material and auxiliary raw materials fed into the SAF and the products, then the chemical composition analysis was carried out by using an X-ray fluorescence (XRF) device. The reactions that take place in the SAF are carbothermic reduction reactions. Metal oxides (Cr<sub>2</sub>O<sub>3</sub>, Fe<sub>2</sub>O<sub>3</sub>, Al<sub>2</sub>O<sub>3</sub>, etc.) react with carbon and are reduced as MO + C = M + CO (M = metal). As a result of this study, the mass amounts of the materials entering into and leaving from the SAF established a balance.

Enhanced supercapacitor performance of porous carbon through tuning maceral composition proportion of coal.

Porous carbons (PCs) have been widely investigated as electrode materials for supercapacitors. However, during the preparation process, intense pore formation reactions result in an amorphous carbon structure, which limits the rate performance of the electrode material. Herein, coal is chosen as a carbon source and making use of different reaction characteristics of vitrinite and inertinite with a KOH activator, an interconnected porous structure carbon material with an abundant graphite microcrystalline structure is obtained; the organic relationships between the ratio of vitrinite and inertinite, carbonization conditions, material structure and capacity performance were researched. At the ratio of vitrinite to inertinite of 1 : 2, the sample shows a specific surface area of 2507 m2 g-1 and its ID1/IG is 1.31, which is lower than that of raw coal (1.36). Due to the synergistic effect of the pore structure and graphite microcrystals, PC-900-40 exhibits an improved specific capacitance of 229.40 F g-1 at a current density of 1.0 A g-1, and even at a high current density of 10.0 A g-1 it delivers a specific capacitance of 170.04 F g-1. The PC-900-40//PC-900-40 symmetrical capacitor retains 96% of its initial capacitance after 20 000 cycles.

Comparative study on efficiency of surface enhanced coal fly ash and raw coal fly ash for the removal of hazardous dyes in wastewater: optimization through response surface methodology.

Crystal violet (CV) dye, because of its non-biodegradability and harmful effects, poses a significant challenge for wastewater treatment. This study addresses the efficiency of easily accessible coal fly ash (CFA)-based adsorbents such as raw coal fly ash (RCFA) and surface enhanced coal fly ash (SECFA), in removing CV dye from waste effluents. Various analytical techniques such as FTIR, XRD, SEM, TEM, BET, zeta sizer and zeta potential were employed for the characterization of the adsorbents and dye-loaded samples. BET revealed that RCFA possesses a surface area of 19.370 m2 g-1 and SECFA of 27.391 m2 g-1, exhibiting pore volumes of 0.1365 cm3 g-1 and 0.1919 cm3 g-1 respectively. Zeta-sizer and potential analysis showed the static charges of RCFA as -27.3 mV and SECFA as -28.2 mV, with average particle sizes of 346.6 and 315.3 nm, respectively. Langmuir and Freundlich adsorption isotherms were also employed for adsorption studies. Employing central composite design (CCD) of response surface methodology (RSM), the maximum CV removal was 81.52% for RCFA and 97.52% for SECFA, providing one minute contact time, 0.0125 g adsorbent dose and 10 ppm dye concentration. From the thermodynamic studies, all the negative values of ΔG° showed that all the adsorption processes of both adsorbents were spontaneous in nature.

Dual-energy X-ray transmission identification method for coal and gangue with different thicknesses and densities

To reduce the thickness effect influence of dual-energy X-ray transmission (DE-XRT) and solve the problem of identifying coal and gangue with different thicknesses and densities, this paper proposes a method based on the Bayesian optimisation KNN model to classify the pixels of images. The gray feature I and R-values are used to train the classifier to recognize unknown classification pixels. The proportion of classified pixels in the images of a single target is used as the classification parameter. This method reduces the effect of thickness in R-I two-dimensional space. Considering the change in the density of different coal types and taking the density at the boundary between the coal and gangue as 1.8 g/cm3, the recognition rate reached 97.74 %. For raw coal with a 5–150 mm thickness range, the accuracy of identifying predischarged gangue reached 99.16 %. Our study provides a new method and practical guidance for DE-XRT coal preparation.

Study on the inhibitory effect of inhibitor based on the coal molecular structure analysis: A case study of Zhundong coal, Xinjiang, China

The aim of this work is to use the changes in coal molecular structure to study the effect and mechanism of inhibitors, and to provide a reference for better preventing and controlling coal spontaneous combustion. In this study, Xinjiang Zhundong coal was used to construct the macromolecular structure. The changes in the molecular structure of the coal under different inhibitor concentrations and temperature conditions were analyzed by Fourier infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis. ChemDraw and Materials Studio were used to construct a coal molecular structure model with an inhibitor concentration of 20 % at 50 ℃. Results showed that the molecular formula of the ZD2–1 is C222H123O39N. The coal molecule contained a higher number of aliphatic hydrocarbon branches and a lower degree of aromatic ring condensation. When heated to 300 ℃, the proportion of adsorbed oxygen in raw coal decreased obviously, while the reduction of adsorbed oxygen was inhibited under inhibitor conditions. The change of functional groups of coal samples was obvious under 20 % inhibitor concentration, and the dosage was less than that of 30 % inhibitor concentration, revealing the optimal inhibitory effect on coal samples of Zhundong with this concentration.

The impact of pyrolysis temperature on the evolution of the maceral and mineral geochemistry in a subbituminous coal

Temperature has a significant effect on the physical and chemical properties of coal. Based on pyrolysis experiments on subbituminous coals rich in inertinite at the Guanbanwusu Coal Mine on the eastern margin of the Ordos Basin, the effect of thermal maturity on the evolution of macerals and minerals is investigated. The results show that the vitrinite reflectance increases from 0.55 % to 2.58 % with increasing temperature from room temperature to 500 °C. When the temperature exceeded 350 °C, stomas began to appear in the vitrinite, and both pore size and pore complexity increased with increasing temperature. The fluorescent properties of liptinite diminished during pyrolysis and disappeared at temperatures above 350 °C. Liptinite is converted to liquid hydrocarbons when the temperature is below 400 °C and splits to gaseous hydrocarbons when the temperature exceeds 400 °C. Vitrinite and liptinite are the main sources of hydrocarbons, and inertinite remains stable during pyrolysis. The total content of major-element oxides is linearly and positively correlated with the conversion rate of the coal sample during pyrolysis. The composition and content of the major minerals in char are similar to those of raw coal, indicating that the minerals of coal remain stable during low-temperature pyrolysis.

Machine learning prediction of pyrolytic sulfur migration based on coal compositions

Understanding the sulfur migration during pyrolysis of coals especially high-sulfur coals is important. However, structural complexity and diversity of coals make it face huge challenge. In this study, a predictive model for morphological sulfur migration was developed using machine learning based on proximate analysis, ultimate analysis, sulfur forms of raw coal, ash composition, and blending ratio of coal. Three algorithms, i.e., Random Forest, XGBoost, and LightGBM were introduced and compared. The results show that six features are sufficient to accurately predict the products (R2 > 0.9, RMSE < 3.01%). LightGBM model has the advantages of better accuracy, generalization, efficiency, and performance, and Hyperopt has a higher upper limit than Grid-search. H content has a significant effect on S content in chars (St,dchar) and increasing H content from 5.0–5.3 wt% facilitates desulfurization. In addition, CaO, K2O and Fe2O3 also have remarkable effects on St,dchar. Higher H and volatile contents have a greater effect on thiophene removal in char. This work can provide a new approach to explore the sulfur migration in coal blending for coking.