Pingshuo Coal Research Articles

Insight into structure features of coals with different metamorphic degrees via step-wise oxidation

A step-wise oxidation method, combining H2O2 oxidation and alkali-oxygen oxidation (AOO), was applied to study the structure features of coals with different metamorphic degrees. The results show that the conversion of Baiyinhua coal, Hongshaquan coal, Pingshuo coal and Hongliulin coal in 30 % H2O2 solution for 10 h at 60 °C are 89.8 wt%, 79.0 wt%, 29.5 wt%, and 14.8 wt%, respectively. The oxygen containing species retrieved from water-soluble product by ethyl acetate extraction are mainly concentrated in O4-O8 class species, including aliphatic carboxylic acids with a carboxylic range of 1–5 and carbon numbers from 3 to 11, and phenols or aromatic carboxylic acids of 1–3 ring. The residues from H2O2 oxidation of four coals can be completely depolymerized through AOO. The maximum benzene carboxylic acid (BCA) yield of RBYH is 7.66 wt%, while that of RHSQ, RPS, and RHLL are 18.24 wt%, 19.52 wt%, and 19.91 wt%, respectively. The AOO products of four residues show the similar BCA distributions, and mellitic acid, benzenepentacarboxylic acid, pyromellitic acid, trimellitic acid, hemimelitic acid, and phthalic acid are the main BCAs. Therefore, step-wise oxidation can be used as an effective method to understand the structural features of coal, including the small molecule structures obtained after breaking weak bonds and the aromatic substitution information in the residue.

Synergistic effect and chlorine migration behavior in co-pyrolysis of Pingshuo coal and polyvinyl chloride and directional chlorine enrichment using calcium oxide

Co-pyrolysis of waste plastics and low-rank coal is an important way to realize the recycling of plastic wastes and the clean and efficient conversion of coal. However, halogens released would cause equipment corrosion and affect tar quality when halogenated plastics were co-pyrolyzed with coal. For this reason, polyvinyl chloride (PVC), as a representative of halogenated plastic, was co-pyrolyzed with Pingshuo coal (PS) in a two-stage fixed-bed reactor. The synergistic effect between PS and PVC and the migration behavior of chlorine were investigated, and the in-situ removal of chlorine during pyrolysis was explored by adding a CaO bed in the second stage of the reactor. The results showed that the addition of PVC in PS has a positive synergistic effect on tar yield with a maximum tar yield increment of 2.30 wt% at 30 wt% PVC, which is related to the negative synergistic effect on gas yield. Furthermore, the addition of PVC increases the content of 1–3 ring aromatics and decreases the content of aliphatics in the tar. The chlorine content in char and tar increases significantly with the increase of PVC addition. The addition of a CaO bed can significantly reduce the yield of HCl and the chlorine content in the tar. At 700 ℃, the dehydrochlorination efficiency of CaO can reach 78.1%. However, the CO2 produced by PS pyrolysis will reduce the dehydrochlorination efficiency of CaO, and this effect of CO2 can be reduced by increasing the temperature of the CaO bed.

Insight into co-pyrolysis interaction of Pingshuo coal and low-density polyethylene under varied mixing configurations via in-situ Py-TOF-MS

The real-time detection of volatiles is crucial for exploring co-pyrolysis mechanisms. In this study, the co-pyrolysis interaction mechanism of Pingshuo coal (PC) and low-density polyethylene (LDPE) with three varied mixing configurations was explored based on the product distribution and stable radicals in char by using in-situ pyrolysis time-of-flight mass spectrometry with vacuum ultraviolet photoionization as well as electron paramagnetic resonance. Total ion currents results show that mixing configurations have an obvious impact on the release of volatiles. In the coal-LDPE test, the volatiles from coal promotes the cracking of long-chain branches in LDPE, resulting in high alkenes content. Meanwhile, the LDPE melts delay the release of coal volatiles causing a higher peak temperature of 478 °C. As for the LDPE-coal configuration, the LDPE volatiles has a better hydrogen-donor effect, which can interact with volatiles and char from coal pyrolysis to facilitate the formation of aromatics and phenols. Comparatively, coal/LDPE configuration prompts the molten LDPE to coat coal particles and exhibits poor synergies between coal and LDPE. In addition, LDPE-coal char has higher spin concentrations of C-, and O-centered radicals, indicating that the released ·H radicals from LDPE pyrolysis can well interact with char and unreleased volatiles in coal.

The Recent Progress China Has Made in Green Mine Construction, Part II: Typical Examples of Green Mines.

This paper (Part II), right after the Part I, also as an information article, introduces the recent progress of “green mine construction” in China. China is a big country in resource exploitation, but there are serious problems such as hidden danger, environmental pollution and resource waste in the exploitation of mineral resources in China. Therefore, the promotion of “green” mining technology, the implementation of “green mine construction” and the promotion of small- and medium-sized mines to green non-waste mining mode transformation and upgrading are crucial measures on the road of China’s mining development, with very important practical significance. Therefore, this information paper of our Chinese mining research mainly reviews the key progress in the construction and development of green mines and introduces four typical green mine examples in China: (1) the mine with the best green environment in China: Jinhui Mining Co., Ltd., Jiuquan, Gansu Province; (2) the most advanced mine in China: Jinchuan Group Company, Jinchang, Gansu Province; (3) the oldest green mine in China: the Suichang gold mine, Lishui, Zhejiang Province; and (4) the most mechanized mine in China: the Pingshuo Coal Co., Ltd., Shuozhou, Shanxi Province. In the abstract, we claim that Part II serves as a guide to begin a conversation and to encourage experts and scholars to engage in the research of this field.

Study on the Effect of Pyrolysis Conditions on the Combustion Behavior and Char Structure Evolution.

Pyrolysis polygeneration technology has been widely applied due to its wide adaptability to coal types and mild reaction conditions. In this paper, the in situ process test combining pyrolysis and combustion of Pingshuo coal was carried out using a thermogravimetric analyzer and a fluidized-bed reactor. The influence of pyrolysis conditions on the combustion behavior and char structure was studied. The reduction of the pyrolysis temperature and the increase in pyrolysis residence time resulted in a lower burnout temperature of char, thereby improving the combustion characteristics of char. Furthermore, the maximum CO2 release rate reached 2.8 mg/(g·s) during the combustion process. The decrease in the pyrolysis temperature was conducive to the increase of CO2 release mass, suggesting a more complete burning of char. The char combustion process was mainly controlled by the chemical reaction according to the reaction kinetics study. The apparent rate constant of the combustion process increased gradually with the decrease in the pyrolysis temperature of char, and the rate of the combustion reaction increased, which contributed to the enhancement of the combustion performance of the char within the range of 850–950 °C. Meanwhile, the crystal structure inside the char changed significantly after different pyrolysis conditions. However, it had little influence on the molar content of carbon structure, which suggested that the amount of CO2 released was mainly caused by the different resistances of oxygen diffusion to the reaction interface.

Occurrence of harmful elements in the ‘high-aluminium coals' from the Pingshuo mining district, Shanxi Province, China

“High-aluminous coal” is an important coal kind and widely distributed in North China in age of Permo-Carboniferous period. To explore their occurrence state, a total of 15 harmful elements (Li, Ga, In, Cd, Cr, Pb, Be, Mn, Zn, Ag, Co, Ni, Cu, Ba and U) in the No.9 coal and No.11 coal collected from Pingshuo mining district were determined by inductively coupled plasma mass spectrometry (ICP-MS) and scanning electron microscope with energy spectrum (SEM-EDX). The results showed that the content of Li, Ga, In, Pb, Ag and U were all exceed the world hard coal. In view of the result of clustering analysis within trace elements, it was found that Co, Ni, Zn, Cu, Ag and Cr were mainly associated with sulfide minerals due to their common sulfophilic property. Manganese was mainly occurred in carbonate minerals, while Ba, Cd and U were mainly associated with total minerals. In addition, Pb was related to sulfides and Be is mainly distributed in clay minerals. The enrichment of such harmful elements in Pingshuo coal was caused by the combined effect of transgression and input of terrestrial materials in the peat accumulation stage. Li, Ga, In and Ag have reached the harmful grade.

Roof deformation characteristics and experimental verification of advanced coupling support system supporting roadway

AbstractThe advanced hydraulic support group combined with bolts (cables) constitutes the advanced coupling support system, which can ensure the stability of coal mine roadway safely and effectively. To explore the influence of the initial bearing capacity of the advanced hydraulic support on roadway roof deformation under anchor bar (cable) action. According to the actual geological conditions and roadway support of the 15106 working faces in Pingshuo Coal Mine, Yangquan, and Shanxi. Based on the change in the stress and displacement of the half‐space body under normal force in elastic theory and combined with the linear superposition principle, the contact mechanics model of the advanced hydraulic support group and roadway roof under anchorage is established. Selecting the measured anchor bar (cable) preload in the coal mine as the input load of the model, the stress and displacement distribution of the roadway roof under different initial bearing capacities are calculated. The calculation results show that the stress and displacement of the roadway roof along the axis exhibit a “symmetrical distribution” and the whole roadway exhibits a “saddle surface” gradient distribution during the active support of advanced hydraulic support under anchorage. The increase in the initial bearing capacity of the advanced hydraulic support has a great influence on the support effect in the middle area of the roadway and has a relatively small influence on the support effect in the surrounding area of the roof. With an increase in an initial support capacity, the stress gradient changes violently but substantially less than it would under the crushing strength of the surrounding rock. Using the similar simulation experiment theory, a similar simulation experiment roadway was established at 1:40, and the simulation experiment of an advanced hydraulic support coupling active support under anchor protection was carried out. The maximum error percentage of the theoretical calculation and experimental results of roof deformation under different initial bearing capacities is 19.51%, and the maximum error percentage of stress is 13.77%. The accuracy of the distribution law of roof stress and displacement under the initial bearing capacity in the process of active support obtained by theoretical calculation is verified. The research results provide a theoretical basis for advanced coupling adaptive support and the control of fully mechanized mining faces.

Optimization of Reclamation Measures in a Mining Area by Analysis of Variations in Soil Nutrient Grades under Different Types of Land Usage—A Case Study of Pingshuo Coal Mine, China

The development of reclaimed mine soils is normally spatially heterogeneous, making the fine management and utilization of reclaimed mined lands difficult. Soil nutrient grading can provide a scientific basis for the precise regulation of soil nutrients, but few related studies are available in reclaimed mined areas. This study aimed to quantify the spatiotemporal variations in soil nutrient grades under different land-use types in a reclaimed mined area on the Loess Plateau, China. The study area was graded by four soil nutrients (soil available potassium (SAK), soil available phosphorus (SAP), soil total nitrogen (STN), and soil organic matter (SOM)), and the variation features of soil nutrient grades in the initial stage of reclamation under four land-use types (i.e., cultivated land, grassland, forestland, and barren land) were systematically characterized by geostatistical analysis, pedodiversity analysis, and correspondence analysis. The results show that during the initial five years after reclamation, the soil nutrient grades of most reclaimed areas increased from Grade V and VI to Grade I–IV, while the improvements were significantly heterogeneous. Notably, the four land-use types had distinct variation characteristics. The barren land had the lowest SAP level, whereas it had the highest proportion, and medium–high grades of SAK, STN, and SOM (88.3, 100.0, and 100.0%, respectively). In terms of quantitative structure, it had the lowest richness index (S′, 2.5) and Shannon’s entropy index (H′, 0.7) and the highest evenness index (E′, 0.8). These results suggest that the barren land had relatively high and balanced nutrients, with the highest homogeneity among the four land-use types. The grassland had considerable improvement in all nutrients (especially SAP; 95.6% of the area had high SAP grades); however, its improvement was the most heterogeneous (S′ = 4.5, E′ = 0.7). As the second-most heterogeneous land-use type (S′ = 4.0, E′ = 0.8), the forestland had relatively low STN, SAP, and SAK levels due to high nutrient uptake and storage by tree species, but it had the highest proportion of area that reached high SOM grades (36.4%) and medium to high SOM grades (100.0%) due to its high community productivity. The cultivated land, which received fertilization for an additional three years, was the most imbalanced in terms of nutrients. It had the highest proportion of area that reached high SAP grades (98.0%); in contrast, its area proportions of low-grade SAK and SOM (69.0 and 32.9%, respectively) were the highest among the four land-use types. Based on the above comprehensive characterization of soil nutrient grade variation, guidance was given for fine management of reclaimed mined land and the optimization of reclamation measures.

Remote-Sensing Evaluation and Temporal and Spatial Change Detection of Ecological Environment Quality in Coal-Mining Areas

The large-scale development and utilization of coal resources have brought great challenges to the ecological environment of coal-mining areas. Therefore, this paper has used scientific and effective methods to monitor and evaluate whether changes in ecological environment quality in coal-mining areas are helpful to alleviate the contradiction between human and nature and realize the sustainable development of such coal-mining areas. Firstly, in order to quantify the degree of coal dust pollution in coal-mining areas, an index-based coal dust index (ICDI) is proposed. Secondly, based on the pressure-state-response (PSR) framework, a new coal-mine ecological index (CMEI) was established by using the principal component analysis (PCA) method. Finally, the coal-mine ecological index (CMEI) was used to evaluate and detect the temporal and spatial changes of the ecological environment quality of the Ningwu Coalfield from 1987 to 2021. The research shows that ICDI has a strong ability to extract coal dust with an overall accuracy of over 96% and a Kappa coefficient of over 0.9. As a normalized difference index, ICDI can better quantify the pollution degree of coal dust. The effectiveness of CMEI was evaluated by four methods: sample image-based, classification-based, correlation-based, and distance-based. From 1987 to 2021, the ecological environment quality of Ningwu Coalfield was improved, and the mean of CMEI increased by 0.1189. The percentages of improvement and degradation of ecological environment quality were 71.85% and 27.01%, respectively. The areas with obvious degradation were mainly concentrated in coal-mining areas and built-up areas. The ecological environment quality of Pingshuo Coal Mine, Shuonan Coal Mine, Xuangang Coal Mine, and Lanxian Coal Mine also showed improvement. The results of Moran’s Index show that CMEI has a strong positive spatial correlation, and its spatial distribution is clustered rather than random. Coal-mining areas and built-up areas showed low–low clustering (LL), while other areas showed high–high clustering (HH). The utilization and popularization of CMEI provides an important reference for decision makers to formulate ecological protection policies and implement regional coordinated development strategies.

The roles of low molecular compounds on the light aromatics formation during different rank coal pyrolysis

Light aromatic hydrocarbons are an important by-product of the coal chemical industry. The structure and properties of low molecular compounds (LMCs) embedded in coal are different from those of coal macromolecular skeleton structure, they have important effects on the coal pyrolysis. In this paper, the roles of LMCs on the formation of light aromatics during coal pyrolysis are investigated. The results show that LMCs have little effect on the thermal weight loss behavior of the three coals, but they can influence the carbon structure distribution of coals. The main source of light aromatics from coal pyrolysis is derived from thermal cracking of the coal macromolecular framework. And also the LMCs will be pyrolyzed to generate light aromatics. The total amount of BTEXN from extracts of Shengli coal (SL), Pingshuo coal (PS) and Hexi coal (HX) pyrolysis was 15%, 91%, and 12% of that of raw coal. The alkylbenzenes, naphthalene series, and PAHs can be cracked to form light aromatics. The long chain and cyclic aliphatic compounds can not only provide hydrogen for the free radical fragment of aromatics but also generate light aromatics. And the content of these compounds in the extracts of PS is higher than that of the other two coals. Due to the complexity of the combination between LMCs and coal structure, the extracts are easier to generate light aromatics than LMCs embedded in coal during pyrolysis. Because the composition and content of low molecules in coal with different metamorphic degrees are different, the effects of LMCs on the pyrolysis of low rank coal are more obvious compared with high rank coal.

Synergistic effect of co-pyrolysis of pre-dechlorination treated PVC residue and Pingshuo coal

Pyrolysis is an effective way for clean and efficient use of coal, as well as an important way for efficient conversion of waste plastics. A two-step treatment scheme was proposed for chlorine-containing plastics that are difficult to be treated harmlessly. Polyvinyl chloride (PVC) and Pingshuo (PS) coal were used in this study. The PVC was preheated to remove most of the chlorine, and then the pretreated PVC residue (DPVC) and coal were co-pyrolyzed. GC, simulated distillation, GC-MS, elemental analysis, FT-IR and Raman spectroscopy were used to analyze and characterize composition and properties of pyrolysis gas, tar and char. The results show that co-pyrolysis process of DPVC and PS coal has a synergistic effect, and has an obvious positive synergistic effect on formation of char and tar. The experimental value of tar yield is higher than theoretical calculation and the maximum increasing value is 3.35%. There is a negative synergistic effect on formation of pyrolysis water and gas, in which CH4 has the largest decrease in yield, meaning the strongest negative synergy. Co-pyrolysis increases content of light tar, significantly increases content of naphthalenes, and reduces that of asphalt. When DPVC addition is 10%, content of light tar increases by 5 percentage points over the theoretical calculation value. In addition, the co-pyrolysis char surface is smoother, its structure becomes more orderly, and graphitization degree increases.

Insight into co-pyrolysis interactions of Pingshuo coal and high-density polyethylene via in-situ Py-TOF-MS and EPR

In-situ detection on primary volatiles interactions and stable radical evolution behaviors during co-pyrolysis of Pingshuo coal (PC) and high-density polyethylene (HDPE) were systematically investigated via a novel in-situ pyrolysis time-of-flight mass spectrometry (in-situ Py-TOF-MS) combined with electron paramagnetic resonance (EPR) spectroscopy. TG results demonstrated that the mixing ratio 7:3 for PC/HDPE has the better positive interaction performances. Accordingly, in-situ Py-TOF-MS results revealed that more short-chain alkenes such as butene and heptadiene are formed in co-pyrolysis, and the addition of HDPE remarkably enhances the transfer of hydrogen (H) to react with the phenoxy group from PC to form diphenol. According to the EPR analysis, HDPE has a remarkable effect on the stable radical concentration (Ng) in PC pyrolysis residue, especially for oxygen (O)-centered and C-centered radicals. Meanwhile, higher temperature is favorable to the generation of O-centered radicals in PC/HDPE (7:3) pyrolysis residue, its radical concentration increases from 3.42 × 1018 to 20.85 × 1018 spins/g. Furthermore, the peak of CO bond exists at a higher temperature, which is consistent with the changes of O-centered radical concentration, and this result can provide effective supplements for understanding the stable radical interactions.

Ecological risk assessment of coal mine area based on “source-sink” landscape theory – A case study of Pingshuo mining area

Coal mining play a fundamental role in promoting economic and social progress. However, intensive mining operations have brought enormous ecological risks, such as landform destruction, vegetation degradation and biodiversity loss. Based on the “source-sink” landscape and ecological risk assessment theories, this study proposes a new methodology to comprehensively analyze the mechanism of ecological risk and makes quantitative evaluation taking Pingshuo coal mine area as an example from 2000 to 2017. The results prove that the “source-sink” landscape theory is more consistent with the nature of ecological process to distinguish the ecological risk in mining area. Within the study period, the main risk source of mining areas is the environmental disturbance brought by mining production with a spreading trend, while the pollution risk caused by residents’ life is relatively low but the scope is large. The ecological niche of risk sink (a place where ecological risks disappear) in the study area improved as a whole, the ecological vulnerability and exposure coefficient of risk sink shows a decreasing trend from core mine area to outside, and the trend was not obvious at the end stage, testifying the protective effect of environmental governance. The striking increase areas of comprehensive ecological risk are mostly concentrated in the surroundings of mining production expansion, testifying mining practice has a significant adverse impact on the contiguous natural ecosystem. Any kind of pressure from coal mine operation, residents’ production and natural erosion in mining area should not be ignored, and the high risk areas are markedly clustered around the risk sources.

Co-pyrolysis behaviors of low-rank coal and polystyrene with in-situ pyrolysis time-of-flight mass spectrometry

In-situ detection of the primary volatiles is vital for co-pyrolysis interactions of coal and waste plastics, and can reveal their interactions based on the primary volatiles distribution and kinetics. In this study, a novel in-situ pyrolysis time-of-flight mass spectrometry (Py-TOF-MS) was applied to analyze primary volatiles distribution and evolved behaviors of co-pyrolysis of a low-rank Pingshuo coal (PC) and polystyrene (PS), and disclose the interaction mechanisms of PC/PS co-pyrolysis combined with different kinetic models. TG results indicated that the blending ratio of PC to PS being 7:3 has the best interaction in improving volatiles evolved performance. According to in-situ Py-TOF-MS analysis, the addition of PS can promote early release of volatiles from the peak of 418 °C (PC) to 389 °C, and dramatically enhance H-transfer. Among them, the increase of monocyclic aromatic hydrocarbons ascribed to the Diels-Alder and dehydration reaction, while the styrene monomer obviously increases from 2.15% to 7.34% due to the co-pyrolysis enhances the cleavage of Car-Cβ bond on the PS main chain. Moreover, kinetics study identified that the variation of activation energy can provide effective supplements to the co-pyrolysis interactions.

Spatial distribution characteristics of soil and vegetation in a reclaimed area in an opencast coalmine

Opencast coal mining activities result in severe damage to soil and vegetation, and the reconstruction of soil and vegetation is critical in opencast coalmine areas. To better understand the spatial distribution characteristics of soil and vegetation in opencast coalmines, a spatial correlation analysis was conducted on the soil and vegetation properties of the Anjialing and Antaibao opencast coalmines in the Pingshuo coal mining area in China. A total of 70 sample points were selected using grid and transect methods, from which the soil and vegetation properties were determined. The spatial autocorrelation, spatial clustering, and spatial variability of the soil and vegetation indicators were analyzed using global Moran’s index, local Moran’s index, and the geostatistics method based on ArcGIS 10.2 or Geoda 7.0 analysis software. The soil and vegetation indicators were divided into three categories, including vegetation indicators (arbor quantity, AQ; average diameter at breast height, ADBH; herb coverage, HC; average tree height, ATH; canopy density, CD), soil physical properties (soil bulk density, BD; clay content; silt content; sand content; gravel content, GC), and soil chemical properties (soil organic matter, SOM; total nitrogen, TN; available phosphorus, AP; available potassium, AK; pH). There was a strong global autocorrelation among ADBH, clay content, AQ, HC, and SOM. Dumping and reclamation activities affected the spatial distribution characteristics of soil and vegetation. The “high-high” and “low-low” types in all the indicators possessed a large spatial distribution, and the soil and vegetation properties had relatively high spatial clustering. This study can provide a reference for the reclamation practice in opencast coalmine areas.

SWOT analysis of industrial site redevelopment in mining area of Resource-based City -- Taking Pingshuo, Shanxi Province as an example

An important problem to be solved in the transformation and development of resource-based cities is the redevelopment and utilization of industrial sites in mining areas. This paper takes Pingshuo Coal Mine as an example, SWOT analysis model is used to analyze the four factors of advantages, disadvantages, opportunities and risks. The result shows that the dominant factors are the existing transportation, electricity, water supply, heating and sewage treatment facilities. The weaknesses are potential pollution risks and difficulties of facility retrofit. The opportunity is brought about by new urbanization and new rural construction. The challenge is how to attract people to the industrial areas with depleted resources.

Effects of minerals and Fe3+ on sulfur removal and its release behavior during coal pyrolysis under different atmospheres

Yunnan anthracite coal (YN) with high FeS2, Pingshuo coal (PS) with high organic sulfur and Duerping coal (DEP) with 33.52% organic and 64.20% inorganic sulfur were selected to investigate the effects of minerals and Fe3+ on sulfur release behavior during coal pyrolysis under Ar and 3% O2–Ar atmospheres by pyrolysis connected with gas chromatogram (Py-GC) combined with pyrolysis coupled with mass spectrometer (Py-MS). It is found that the sulfur removal ratios and the total amount of sulfur-containing gases release of coal samples under 3% O2–Ar atmosphere are higher than those under Ar atmosphere, indicating that O2 participates in coal pyrolysis process. The effects of minerals on sulfur removal are affected by these coals types. However, effects of Fe3+ on sulfur removal are related to atmospheres. During pyrolysis, Fe3+ is beneficial for all sulfur compounds to decompose at lower temperature under 3% O2–Ar atmosphere, while inhibits sulfur removal under Ar atmosphere. The minerals in coals can absorb sulfur gases. However, Fe3+ can significantly promote COS and SO2 release at lower temperatures under both atmospheres. But Fe3+ inhibits H2S release under Ar atmosphere.

Effect of high silicon-aluminum coal ashes on sintering and fusion characteristics of a potassium-rich biomass ash

The effects of high silicon-aluminum coal ashes (Shajuzi coal ash (SJZA) and Pingshuo coal ash (PSA)) on the sintering and fusion behaviors of a potassium-rich biomass ash (cotton stalk ash (CSA)) were investigated by a horizontal tube furnace and an ash fusion temperature (AFT) analyzer. X-ray diffraction (XRD), thermogravimetry and differential scanning calorimetry (TG-DSC) techniques were applied to analyze the mineral transformations and thermal behaviors of the ash samples. As the coal ash mass ratio varied from 0 to 50%, the sintering degree of CSA/SJZA and CSA/PSA mixtures gradually mitigated. The AFTs of the two groups of mixtures all presented parabolic with respect to coal ash ratio. The potassium content in CSA was very high (K2O, 39.55%), and K-containing minerals mainly existed as low melting point (MP) matters, i.e., sylvite (KCl), arcanite (K2SO4), potassium carbonate (K2CO3), and fairchildite (K2Ca(CO3)2). The mitigation of sintering degree was ascribed to a decrease in KCl content with increasing coal ash ratio. When the coal ash ratio was less than 20%, the decrease in AFT was due to the consumption of alkaline earth metal oxide and the formation of K silicate. The conversions of low MP K salts to high MP K–Al silicates (kalsite (KAlSiO4) and nepheline (KNa3Al4Si4O16)) and the formations of other high MP minerals increased the AFTs after adding 20% coal ash. The thermogravimetric analysis showed that the endothermic peak of KCl evaporation weakened to disappear and the exothermic peaks of some reactions enhanced with rising coal ash ratio.

Water abundance analysis of aquifer in coal roof based on grey relational analysis and analytic hierarchy process

As water abundance of aquifer of coal roof significantly influences roof water hazard, evaluating and grading the degree of water abundance are important in practical application. By analyzing the influencing factors of water abundance of aquifer, an evaluation index system and a grading standard for the water abundance were established integrating quantitative and qualitative indexes. Meanwhile, according to the grey relation characteristics of the major factors influencing water abundance, a multi-factor evaluation model for water abundance was constructed based on grey relational analysis and analytic hierarchy process. The model can objectively reveal the influences of the multiple factors on the evaluation of water abundance. Furthermore, the method was verified by comprehensively evaluating the water abundance of the aquifer of coal roof in a working face of Pingshuo Coal Mine in Shanxi, China using the model. The method provides basis for the research on the evaluation of water abundance of aquifer in coal roof.

Improving aromatic hydrocarbons yield from coal pyrolysis volatile products over HZSM-5 and Mo-modified HZSM-5

The effect of Mo/HZSM-5 and HZSM-5 on the yield of aromatic hydrocarbons such as BTEXN (benzene, toluene, ethylbenzene, xylene, naphthalene) during Pingshuo Coal flash pyrolysis at different temperatures was analyzed using Py-GC/MS. It shows that both HZSM-5 and Mo/HZSM-5 can remarkably increase the yield of BTEXN. HZSM-5 shows the highest catalytic activity at 900°C, the total BTEXN yield increases from 116ng/mg at 500°C to a maximum of 7000ng/mg at 900°C, and then decreases with further increase of temperature. The maximum yield with HZSM-5 obtained at 900°C is more than three times that without HZSM-5. However, Mo/HZSM-5 has the potential to yield more BTEXN, as the maximum yield of BTEXN is 7020ng/mg at 800°C. The results indicate that Mo has been loaded on the HZSM-5 zeolite as MoO3. As a result, Mo/HZSM-5 can promote the aromatization of olefins and alkanes, dehydroxylation of phenolic compounds, as well as aromatization of CH4. Thus, Mo/HZSM-5 is more suitable for the catalytic conversion of the gaseous products from coal pyrolysis into BTEXN.