Showing papers in "International Journal of Coal Science & Technology in 2014"

Support technologies for deep and complex roadways in underground coal mines: a review

Abstract: Based on geological and mining characteristics, coal mine roadways under complex conditions were divided into five types, for each type the deformation and damage characteristics of rocks surrounding roadways were analyzed. The recent developments of roadway support technologies were introduced abroad, based on the experiences of supports for deep and complex roadways from Germany, the United States and Australia. The history and achievements of roadway support technologies in China were detailed, including rock bolting, steel supports, grouting reinforcement and combined supports. Four typical support and reinforcement case studies were analyzed, including a high stressed roadway 1,000 m below the surface, a roadway surrounded by severely weak and broken rocks, a chamber surrounded by weak and broken rocks, and a roadway with very soft and swelling rocks. Based on studies and practices in many years, rock bolting has become the mainstream roadway support form in China coal mines, and steel supports, grouting reinforcement and combined supports have also been applied at proper occasions, which have provided reliable technical measures for the safe and high effective construction and mining of underground coal mines.

Research progress of monitoring, forecasting, and prevention of rockburst in underground coal mining in China

Abstract: As one of the dynamic disasters of coal mines, rockburst seriously affects underground safe coal mining. Based on the laboratory test, field test, and theoretical analysis, this study proposed the principle of the rock burst induced by the combination of dynamic and static stresses and divided such rock burst into three types, including induced by primary dynamic stress, mainly induced by dynamic stress, and by dynamic stress in low critical stress state. The expressions of the static stress induced by coal mining and dynamic stress induced by mining tremors were obtained. Moreover, theories and technologies at home and abroad were summarized concerning the monitoring, forecasting, and preventing of rockburst. These mainly include the zoning and leveling forecasting method, electromagnetic radiation technology, elastic wave and seismic wave computed tomography technologies in aspect of rockburst monitoring, as well as the intensity weakening theory, the strong-soft-strong structure effect, the directional hydraulic fracturing technology, the roadway support system in regards of rockburst prevention. The prospect of rockburst development suggested that researches concerning the rockburst mechanism should be quantitatively developed around the roadway and coalface surrounding coal-rock mass. It should be focused on the rockburst mechanism and prevention technology of mining with over 1,000 km deep and mining in large tectonic zone. In addition, the monitoring and prevention of rockburst should be based on rockburst mechanism.

Current status and technical challenges of CO2 storage in coal seams and enhanced coalbed methane recovery: an overview

Abstract: In the past two decades, research on CO2 storage in coal seams and simultaneously enhanced coalbed methane recovery (ECBM) has attracted a lot of attention due to its win–win effect between greenhouse gas (CO2) emission reduction and coalbed methane recovery enhancement. This paper presents an overview on the current status of research on CO2-ECBM in the past two decades, which involves CO2 storage capacity evaluations, laboratory investigations, modelings and pilot tests. The current status shows that we have made great progress in the ECBM technology study, especially in the understanding of the ECBM mechanisms. However, there still have many technical challenges, such as the definition of unmineable coal seams for CO2 storage capacity evaluation and storage site characterization, methods for CO2 injectivity enhancement, etc. The low injectivity of coal seams and injectivity loss with CO2 injection are the major technique challenges of ECBM. We also search several ways to promote the advancement of ECBM technology in the present stage, such as integrating ECBM with hydraulic fracturing, using a gas mixture instead of pure CO2 for injection into coal seams and the application of ECBM to underground coal mines.

Post-mining policies and practices in the Eastern USA coal region

Abstract: Surface coal mines prior to 1950 in the USA were generally left without any reclamation. As government regulations advanced since then, mine operators were required to backfill the area and plant grasses or trees. After the federal Surface Mining Control and Reclamation Act (SMCRA) was passed in 1977 in the USA, mine operators were required to conduct pre-mining analyses of the site and to designate a land use that could be achieved after mining. Successful reclamation, as needed to satisfy today’s societal demands, requires engineering, design, and purposeful reconstruction of the full mining disturbance, not just its surface, and control of waters leaving the mine site. Effective reclamation on modern American coal mines is fully integrated with the mining operation. A suitable and effective post-mining land use that is sustainable for future generations is crucial to the long-term success and profitability of the mining business and to the future economic benefits of the landowner. Accepted post-mining land uses in the USA are: (1) prime farmland, (2) hay land and pasture, (3) biofuel crops, (4) forestry, (5) wildlife habitat, and (6) building site development. Policies and regulations for each post-mining land use were developed and practices to achieve successful and sustainable land uses were established. Post-mining conditions should provide ecosystem services and produce lands capable of supporting societal needs in the future.

Development and prospect on fully mechanized mining in Chinese coal mines

Abstract: Fully mechanized mining (FMM) technology has been applied in Chinese coal mines for more than 40 years. At present, the output of a FMM face has reached 10-million tons with Chinese-made equipment. In this study, the new developments in FMM technology and equipment in Chinese coal mines during past decades are introduced. The automatic FMM technology for thin seams, complete sets of FMM technology with ultra large shear height of 7 m for thick seams, complete sets of fully mechanized top coal caving technology with large shear height for ultra-thick seams of 20 m, complete sets of FMM technology for complex and difficult seams, including steeply inclined seams, soft coal seams with large inclination angle, and the mechanized filling mining technology and equipment are presented. Some typical case studies are also introduced. Finally, the existing problems with the FMM technology are discussed, and prospect of FMM technology and equipment applied in Chinese coal mines is put forward.

Progress of the technique of coal microwave desulfurization

Abstract: With the advantages of its fast speed, effective and moderate controllable conditions, desulfurization of coal by microwave has become research focus in the field of clean coal technology. Coal is a homogeneous mixture which consists of various components with different dielectric properties, so their abilities to absorb microwaves are different, and the sulfur-containing components are better absorbers of microwave, which makes them can be selectively heated and reacted under microwave irradiation. There still remain controversies on the principle of microwave desulfurization at present, thermal effects or non-thermal effects. The point of thermal effects of microwave is mainly base on its characters of rapidly and selectly heating. While, in view of non-thermal effect, direct interactions between the microwave electromagnetic field and sulfur containing components are proposed. It is a fundamental problem to determine the dielectric properties of coal and the sulfur-containing components to reveal the interaction of microwave and sulfur-containing compounds. However, the test of dielectric property of coal is affected by many factors, which makes it difficult to measure dielectric properties accurately. In order to achieve better desulfurization effect, the researchers employ methods of adding chemical additives such as acid, alkali, oxidant, reductant, or changing the reaction atmosphere, or combining with other methods such as magnetic separation, ultrasonic and microorganism. Researchers in this field have also put forward several processes, and have obtained a number of patents. Obscurity of microwave desulfurization mechanism, uncertainties in qualitative and quantitative analysis of sulfur-containing functional groups in coal, and the lack of special microwave equipment have limited further development of microwave desulfurization technology.

Progress in developments of dry coal beneficiation

Abstract: China’s energy supply heavily relies on coal and China’s coal resource and water resource has a reverse distribution. The problem of water shortages restricts the applications of wet coal beneficiation technologies in drought regions. The present situation highlights the significance and urgency of developing dry beneficiation technologies of coal. Besides, other countries that produce large amounts of coal also encounter serious problem of lack of water for coal beneficiation, such as American, Australia, Canada, South Africa, Turkey and India. Thus, dry coal beneficiation becomes the research hot-points in the field of coal cleaning worldwide in recent years. This paper systematically reviewed the promising research efforts on dry coal beneficiation reported in literature in last 5 years and discussed the progress in developments of dry coal beneficiation worldwide. Finally, we also elaborated the prospects and the challenges of the development of dry coal beneficiation.

Zoning of land reclamation in coal mining area and new progresses for the past 10 years

Abstract: Coal mining disturbed land is the main sources of land reclamation in China. With the rapid increase of economy and coal production, more and more land has been disturbed by construction and coal mining; thus, land reclamation has become highlights in the past 10 years, and China is boosting land reclamation in mining areas. Disturbance characteristics vary from region to region, according to natural and geological conditions, coal mining area land reclamation was divided into 3 zones, which are eastern, western and southern. Reclamation strategies are focused on prime farmland protection in eastern and ecological restoration in western and southern zones, respectively. Several innovative reclamation technologies and theories for the past 10 years were introduced in this paper, including concurrent mining and reclamation, Yellow river sediments backfilling, self-reclamation, and topsoil alternatives in opencast mines. Besides, in the government regulation and legal system building respect, several important laws and regulations were issued and implemented in the past 5 years, promoting land reclamation management and supervision greatly. Land reclamation is and will still be one of the most important parts of coal industry in the future, and more efforts and funds are expected to get involved.

Mechanical model of water inrush from coal seam floor based on triaxial seepage experiments

Abstract: In order to study the mechanism of confined water inrush from coal seam floor, the main influences on permeability in the process of triaxial seepage experiments were analyzed with methods such as laboratory experiments, theoretical analysis and mechanical model calculation. The crack extension rule and the ultimate destruction form of the rock specimens were obtained. The mechanism of water inrush was explained reasonably from mechanical point of view. The practical criterion of water inrush was put forward. The results show that the rock permeability “mutation” phenomenon reflects the differences of stress state and cracks extension rate when the rock internal crack begins to extend in large-scale. The rock ultimate destruction form is related to the rock lithology and the angle between crack and principal stress. The necessary condition of floor water inrush is that the mining pressure leads to the extension and transfixion of the crack. The sufficient condition of floor water inrush is that the confined water’s expansionary stress in normal direction and shear stress in tangential direction must be larger than the internal stress in the crack. With the two conditions satisfied at the same time, the floor water inrush accident will occur.

Influence of flue gas cleaning system on characteristics of PM2.5 emission from coal-fired power plants

Abstract: This study investigated the influence of precipitators and wet flue gas desulfurization equipment on characteristics of PM2.5 emission from coal-fired power stations. We measured size distribution and removal efficiencies, including hybrid electrostatic precipitator/bag filters (ESP/BAGs) which have rarely been studied. A bimodal distribution of particle concentrations was observed at the inlet of each precipitator. After the precipitators, particle concentrations were significantly reduced. Although a bimodal distribution was still observed, all peak positions shifted to the smaller end. The removal efficiencies of hybrid ESP/BAGs reached 99 % for PM2.5, which is considerably higher than those for other types of precipitators. In particular, the influence of hybrid ESP/BAG operating conditions on the performance of dust removal was explored. The efficiency of hybrid ESP/BAGs decreased by 1.9 % when the first electrostatic field was shut down. The concentrations and distributions of particulate matter were also measured in three coal-fired power plants before and after desulfurization devices. The results showed diverse removal efficiencies for different desulfurization towers. The reason for the difference requires further research. We estimated the influence of removal technology for particulate matter on total emissions in China. Substituting ESPs with hybrid ESP/BAGs could reduce the total emissions to 104.3 thousand tons, with 47.48 thousand tons of PM2.5.

Micro-structural evolution and their effects on physical properties in different types of tectonically deformed coals

Abstract: The macromolecular structure of tectonically deformed coals (TDC) may be determined by the deformation mechanisms of coal. Alterations of the macromolecular structure change the pore structure of TDC and thereby impact physical properties such as porosity and permeability. This study focuses on structure and properties of TDC from the Huaibei and Huainan coal mining areas of southern North China. Relationships between the macromolecular structure and the pore structure of TDC were analyzed using techniques such as X-ray diffraction, high-resolution transmission electron microcopy, and the low-temperature nitrogen adsorption. The results indicated that the directional stress condition can cause the arrangement of basic structural units (BSU) more serious and closer. And, the orientation is stronger in ductile deformed coal than in brittle deformed coal. Tectonic deformation directly influences the macromolecular structure of coal and consequently results in dynamic metamorphism. Because the size of BSU in brittle deformed coal increases more slowly than in ductile deformed coal, frictional heating and stress-chemistry of shearing areas might play a more important role, locally altering coal structure under stress, in brittle deformed coal. Strain energy is more significant in increasing the ductile deformation of coal. Furthermore, mesopores account for larger percentage of the nano-scale pore volume in brittle deformed coals, while mesopores volume in ductile deformed coal diminishes rapidly along with an increase in the proportion of micropores and sub-micropores. This research also approved that the deformations of macromolecular structures change nano-scale pore structures, which are very important for gas adsorption and pervasion space for gas. Therefore, the exploration and development potential of coal bed methane is promising for reservoirs that are subjected to a certain degree of brittle deformation (such as schistose structure coal, mortar structure coal and cataclastic structure coal). It also holds promise for TDC resulting from wrinkle structure coal of low ductile deformation and later superimposed by brittle deformation. Other kinds of TDC suffering from strong brittle-ductile and ductile deformation, such as scale structure coal and mylonitic structure coal, are difficult problems to resolve.

Dynamic monitoring of soil bulk density and infiltration rate during coal mining in sandy land with different vegetation

Abstract: To investigate the effects of coal mining on soil physical properties, sandy lands with three major vegetation types (Salix psammophila, Populus simonii, and Artemisia ordosica) were investigated by the ring knife method and double-ring infiltrometer. Specifically, variations in soil bulk density and water infiltration rate and the influences of coal mining and vegetation type on the properties during different subsidence stages were studied at the Shendong Bulianta mine. The results showed that, in the period before mining, soil bulk density occurred in the order A. ordosica > P. simonii > S. psammophila, with a negative correlation between the initial infiltration rate and steady infiltration rate being observed. In the period during mining and 3 months after mining, there were no significant differences in soil bulk density and water infiltration rate among vegetation types. At 1 year after mining, the soil bulk density occurred in the order A. ordosica > S. psammophila > P. simonii, having a negative correlation with the steady infiltration rate. The water infiltration depths of the S. psammophila, P. simonii and A. ordosica were 50, 60, and 30 cm, respectively. The infiltration characters were simulated by the Kostiakov equations, and the simulated and experimental results were consistent. Linear regression revealed that vegetation types and soil bulk density had significant effects on soil initial infiltration rate during the four study periods, and the infiltration rate of the period 1 year after mining was mainly influenced by the soil bulk density of the period before mining. The results indicated that vegetation types had significant effects on soil bulk density, and that the tree–shrub–grass mode was better than one single plantation for water conversation and vegetation recovery in sandy land subjected to mining.

Influence of fly ash and sewage sludge application on wheat biomass production, nutrients availability, and soil properties

Abstract: The influence of fly ash (FA) applied alone and/or with sewage sludge (SS) on wheat (Triticum vulgare) grain yield, biomass production and soil properties was studied in a field experiment. The results showed that both FA and SS significantly increased grain yield and plant biomass. FA applied alone increased significantly soil pH and EC while FA applied together with SS did not significantly affect them compared to mono FA treatment. Soil pH and EC values increased with time in FA and FA-SS treatments. SS increased soil organic matter and total N content and SS applied together with FA increased also available soil B. From the plant nutrients tested only tissue N concentration was increased significantly in all treatments compared to control. Copper, Zn, Mn, Ni, and Pb at both available and total concentrations are significantly affected.

Coal waste management practices in the USA: an overview

Abstract: This paper provides an overview of coal waste management practices with two case studies and an estimate of management cost in 2010 US dollars. Processing of as-mined coal typically results in considerable amount of coarse and fine coal processing wastes because of in-seam and out-of-seam dilution mining. Processing plant clean coal recovery values run typically 50 %–80 %. Trace metals and sulfur may be present in waste materials that may result in leachate water with corrosive characteristics. Water discharges may require special measures such as liner and collection systems, and treatment to neutralize acid drainage and/or water quality for trace elements. The potential for variations in coal waste production and quality depends upon mining or processing, plus the long-term methods of waste placement. The changes in waste generation rates and engineering properties of the coal waste during the life of the facility must be considered. Safe, economical and environmentally acceptable management of coal waste involves consideration of geology, soil and rock mechanics, hydrology, hydraulics, geochemistry, soil science, agronomy and environmental sciences. These support all aspects of the regulatory environment including the design and construction of earth and rock embankments and dams, as well as a wide variety of waste disposal structures. Development of impoundments is critical and require considerations of typical water-impounding dams and additional requirements of coal waste disposal impoundments. The primary purpose of a coal waste disposal facility is to dispose of unusable waste materials from mining. However, at some sites coal waste impoundments serve to provide water storage capacity for processing and flood attenuation.

Anomaly and geochemistry of rare earth elements and yttrium in the late Permian coal from the Moxinpo mine, Chongqing, southwestern China

Abstract: The rare earth elements and yttrium (REY) of the K2 coal from the Moxinpo mine, Chongqing, were determined using inductively coupled plasma mass spectrometry (ICP-MS). The results show that REY are enriched in the K2 coal, with the average content up to 462 μg/g, much higher than average values of most coals in the world. The REY distribution patterns indicate that the light REY is enriched and show a well-pronounced Eu minimum. The fractionation of individual light-REY is higher than that of the heavy-REY. The REY distribution through the K2 coal seam shows that the top and bottom portion of the coal seam have a lower content of REY than the middle portion. Goyazite and rhabdophane were identified with a scanning electron microscope equipped with an energy-dispersed X-ray spectrometer (SEM-EDX). The REY distributions through the coal seam, SEM-EDX data and the correlation analysis between ash yields and the concentrations have revealed that the REY mainly occurs in the organic matter. The K2 coal is a potential rare-metal resource due to its high REY contents, and the coal ash could be regarded as a new and promising raw material for recovery of REY as a by-product.

Agricultural impacts of longwall mine subsidence: the experience in Illinois, USA and Queensland, Australia

Abstract: Unlike conventional room and pillar underground coal mining, where subsidence is designed to be prevented, subsidence is a planned outcome of other methodologies. These include high extraction retreat, where the roof supporting pillars are systematically removed, and longwall mining, which employs a machine that mines a continuous strip of coal, thus leaving no roof supports. Both types result in the surface dropping ~70 % of the mined-out thickness. In Illinois there was a concern that farm land thus subsided would be lost to productive agriculture. Consequently, the possibility that planned mine subsidence would be banned in Illinois lead to the creation of the Illinois Mine Subsidence Research Program in 1985 to investigate agricultural impacts of planned mine subsidence and the possibility of mitigating its impact. Its findings established that subsidence was not as detrimental as feared and that the impacts could be mitigated. The project was a successful collaboration of state and federal governments and local Universities. Similarly, in Queensland, longwall mining is opposed by some in the farming community. In response, Bandanna Energy, the company planning the mining, organized the Agricultural Coexistence Research Committee to oversee research into the mitigation of longwall mining impacts. Although the soils, climate, and regulatory regimes are different, concerns of the local communities are similar.

CO2 capture RD&D proceedings in China Huaneng Group

Abstract: CO2 capture is an important carbon management route to mitigate the greenhouse gas emission in power sector. In recent years, China Huaneng Group (CHNG) has paid more attention on CO2 capture technology development and launched a series of R&D and demonstration projects. In the area of pre-combustion CO2 capture technology, GreenGen project initiated by CHNG is the first integrated gasification combined cycle (IGCC) power plant in China. Located in Tianjin, GreenGen aims at the development, demonstration and promotion of a near-zero emissions power plant. An IGCC plant of 250 MW has successfully passed full-scale trial operation. In the next phase, a pre-combustion CO2 capture unit will be integrated into the system. Pre-combustion process based on coal chemical process has been developed with lower costs successfully. Regarding to post-combustion CO2 capture (PCC), in 2008, CHNG built a 3,000 tpa CO2 capture plant, which was the first CO2 capture demonstration plant in China. In 2009, CHNG launched a PCC project in Shanghai with a capture capacity of 120,000 tpa CO2. Recently, Huaneng Clean Energy Research Institute (CERI) and Powerspan formed a joint venture, Huaneng-CERI-Powerspan (HCP). HCP has completed the technology qualification program to supply carbon capture technology for the CO2 capture Mongstad project. Besides these activities mentioned above, feasibility studies and system design for large scale PCC system, have been undertaken by CERI and its partners from Australia, US and Europe.

Influence of pore structures on the mechanical behavior of low-permeability sandstones: numerical reconstruction and analysis

Abstract: The research of rock properties based on its inherent microscopic to mesoscopic porous structure has drawn great attention for its potential in predicting the macroscopic behavior of rocks. An accurate reconstruction of the three-dimensional porous structure is a premise for the related studies of hydraulic and mechanical properties of rocks, such as the transport properties and mechanical responses under pressures. In this paper, we present a computer procedure for reconstructing the 3D porous structure of low-permeability sandstone. Two large-size 3D models are reconstructed based on the information of a reference model which is established from computed tomography (CT) images. A self-developed finite element method is applied to analyze the nonlinear mechanical behavior of the sandstone based on its reconstructed model and to compare the results with those based on the reference model. The good consistency of the obtained mechanical responses indicates the potential of using reconstruction models to predict the influences of porous structure on the mechanical properties of low-permeability sandstone.

Research on coal staged conversion poly-generation system based on fluidized bed

Abstract: A new coal staged conversion poly-generation system combined coal combustion and pyrolysis has been developed for clean and high efficient utilization of coal. Coal is the first pyrolysed in a fluidized pyrolyzer. The pyrolysis gas is then purified and used for chemical product or liquid fuel production. Tar is collected during purification and can be processed to extract high value product and to make liquid fuels by hydro-refining. Semi-coke from the pyrolysis reactor is burned in a circulating fluidized bed (CFB) combustor for heat or power generation. The system can realize coal multi-product generation and has a great potential to increase coal utilization value. A 1 MW poly-generation system pilot plant and a 12 MW CFB gas, tar, heat and power poly-generation system was erected. The experimental study focused on the two fluidized bed operation and characterization of gas, tar and char yields and compositions. The results showed that the system could operate stable, and produce about 0.12 m3/kg gas with 22 MJ/m3 heating value and about 10 wt% tar when using Huainan bituminous coal under pyrolysis temperature between 500 and 600 °C. The produced gases were mainly H2, CH4, CO, CO2, C2H4, C2H6, C3H6 and C3H8. The CFB combustor can burn semi-coke steadily. The application prospect of the new system was discussed.

Simulation of coal char gasification using O2/CO2

Abstract: The authors proposed an integrated gasification fuel cell zero-emission system. The coal char gasification is discussed using high temperature and concentration of CO2 produced by solid oxide fuel cells and oxy-fuel combustion. The gasification is simulated by Aspen plus based on Gibbs free energy minimization method. Gasification model of pulverized coal char is computed and analyzed. Effects of gas flow rate, pressure, preheating temperature, heat losses on syngas composition, reaction temperature, lower heating value and carbon conversion are studied. Results and parameters are determined as following. The optimum O2 flow rate is 20 kg/h. The reaction temperature decreases from 1645 to 1329 °C when the CO2 flow rate increases from 0 to 5 kg/h, the CO2 flow rate should be operated reasonably; lower heating value reduces and reaction temperature increases as the pressure increases; compared to the CO2 preheating, O2 preheating has greater influence on reaction temperature and lower heating value.

Lignite oxidative desulphurization

Abstract: The process of lignite desulphurization via its treatment by an oxidant (air or air–steam mixture) has been studied. The research objective was useful determination of steam application in oxidative lignite desulphurization. It has been proved that the water steam should be included in the oxidant composition to increase the hydrogen sulphide and combustible constituent content in the gases obtained during the processes under research. The impact of factors which affect the reactions between solid (in our case – lignite) and gaseous reagent (oxidant, i.e. air and or air–steam mixture) upon the research process has been investigated, if these reactions occur in the kinetic area. Such factors are linear rate of oxidant movement and coal grain size. The values of oxidant movement linear rate and coal grain size, which the reaction transfer from pyrite sulphur and organic content of lignite from diffusion into kinetic area occurs by, have been determined. Under these “transfer” conditions, the values of coefficients of oxidant mass transfer (β, m/s) as well as Sherwood criteria and boiling layer differences have been calculated.

Innovative backfilling longwall panel layout for better subsidence control effect—separating adjacent subcritical panels with pillars

Abstract: In recent years, field trials of non-pillar longwall mining using complete backfill have been implemented successively in the Chinese coal mining industry. The objective of this paper is to get a scientific understanding of surface subsidence control effect using such techniques. It begins with a brief overview on complete backfill methods primarily used in China, followed by an analysis of collected subsidence factors under mining with complete backfill. It is concluded that non-pillar longwall panel layout cannot protect surface structures against damages at a relatively large mining height, even though complete backfill is conducted. In such cases, separated longwall panel layout should be applied, i.e., panel width should be subcritical and stable coal pillars should be left between the adjacent panels. The proposed method takes the principles of subcritical extraction and partial extraction; in conjunction with gob backfilling, surface subsidence can be effectively mitigated, thus protecting surface buildings against mining-induced damage. A general design principle and method of separated panel layout have also been proposed.

Research on the maceral characteristics of Shenhua coal and efficient and directional direct coal liquefaction technology

Abstract: In this research, molecular structure models were developed respectively for Shenhua coal vitrinite concentrates (SDV) and inertinite concentrates (SDI), on the basis of information on constitutional unit of Shenhau coal and elemental analysis results obtained from 13C-NMR analysis characterization, FTIR analysis characterization, X-ray diffraction XRD and XPS analysis characterization. It can be observed from characterization data and molecular structure models that the structure of SDV and SDI is dominated by aromatic hydrocarbon, with aromaticity of SDI higher than that of SDV; SDV mainly consists of small molecule basic structure unit, while SDI is largely made from macromolecular structure unit. Based on bond-level parameters of the molecular model, the research found through the autoclave experiment that vitrinite liquefaction process goes under thermodynamics control and inertinite liquefaction process under dynamics control. The research developed an efficient directional direct coal liquefaction technology based on the maceral characteristics of Shenhua coal, which can effectively improve oil yield and lower gas yield.

Geochemistry of rare earth elements and yttrium in a Ge-poor coal from the Wulantuga ore deposit, Inner Mongolia, North China

Abstract: This paper reports data of yttrium and rare earth (REY, or REE if Y is considered) in a Ge-poor (the average value of Ge is 0.57 µg/g) coal from the Wulantuga ore deposit, middle Inner Mongolia, northern China. The contents of yttrium and rare earth in six coal samples of the Wulantuga ore deposit were detected by inductively coupled plasma mass spectrometry. The content of yttrium and rare earth in the study area varies from 5.88 to 119.19 μg/g, with an average of 61.85 μg/g, similar to the average value for world coals. The light-REY and heavy-REY enrichments are the two major REY-enrichment types of the Ge-poor coal from the Wulantuga ore deposit, and the top and bottom parts of the coal seam have a higher content of REY than the middle part. The sources of yttrium and rare earth in the Ge-poor coal of Wulantuga may be mainly associated with terrigenous materials and natural waters enriched in yttrium and rare earth.

Predicting release and aquatic effects of total dissolved solids from Appalachian USA coal mines

Abstract: Appalachian USA coal mines have been implicated as major stressors to aquatic life in headwater streams via discharge of total dissolved solids (TDS). This paper summarizes column leaching studies of spoils (n > 50) and refuse and TDS effects on local water quality and biotic response. The initial pH of most materials is near-neutral. Initial specific conductance (SC) values range from 500–1,000 to >3,000 µs/cm, but 2/3 of materials drop below 500 µs/cm after several pore volumes of leaching. Studies of mining-influenced streams have found altered aquatic life, relative to natural conditions with no mining influence, at SC ranging from ~200 to ~700 µs/cm with depressed aquatic life consistently associated with elevated TDS; mechanisms causing such effects are under investigation. We suggest that active mine operations should be modified to place high TDS producing materials in ways that reduce contact with percolating drainage waters.

Role of the different planting age of seabuckthorn forests to soil amelioration in coal mining subsidence land

Abstract: To investigate the effects of seabuckthorn (Hippophae rhamnoides) on soil amelioration, using the space replacement method, soil physical and chemical indexes as well as the microorganism quantity and soil enzyme activities were analyzed. The results showed that: the soil bulk density of surface soil decreased and soil porosity and field capacity increased after afforestation with seabuckthorn. The plant was found to effectively reduce the soil pH, increase the soil conductivity, soil organic matters and available nutrients. Soil microorganism quantity, soil enzyme activities were both higher in 0–20 cm layer than in 20–40 cm layer. With the increase years of remediation with seabuckthorn, the quantity of soil microorganism and enzyme activities were increasing to a higher level 5 to 8 years later. Our study indicates that seabuckthorn can effectively improve soil physical and chemical properties, increase the quantity of soil microorganisms and enzyme activities, which is of great significance for the ecosystem restoration in mining areas.

Conversion of producer gas using NiO/SBA-15 obtained with different synthesis methods

Abstract: In this study, NiO/SBA-15 was prepared by both direct and post synthesis methods. TEM images revealed that NiO particles aggregated in NiO/SBA-15 obtained with post synthesis method, regardless of NiO loading. However, NiO particles were monodispersed in NiO/SBA-15 with a NiO loading of less than 15 wt% by using the direct synthesis method. In this case, NiO particles aggregated when NiO loading was over 20 wt%. TPR analysis verified that with direct synthesis method the location boundary of NiO particles on outer and pore surface could be observed clearly, whereas that could not observed in the case of post synthesis method. This indicates that the type of synthesis method displays significant effect on the location of NiO particles dispersed into the SBA-15. Producer gas conversion was carried out using NiO/SBA-15 as catalysts, which were synthesized with different synthesis methods. The gas conversion including methanation occurred at low temperature (i.e., 300–400 °C) and the reverse water gas shift (RWGS) reaction at high temperature (i.e., 400–900 °C). High temperatures facilitated CO2 conversion to CO with CO selectivity close to 100 %, regardless of the synthesis method of the used catalyst. At low temperatures the dispersion type of NiO particles affected the CO2 conversion reaction, i.e., monodispersed NiO particles gave a CO selectivity of close to 100 %, similar to that obtained at high temperature. The aggregated NiO particles resulted in a CO selectivity of less than 100 % owing to CH4 formation, regardless of synthesis method of catalyst. Therefore, NiO/SBA-15 obtained with direct synthesis method favored RWGS reaction because of high CO selectivity. NiO/SBA-15 obtained with post synthesis method is suited for methanation because of high CH4 selectivity, and the conversion of CO2 to CH4 through methanation increased with increasing NiO loading.

Electrochemical performance and stability of Sr-doped LaMnO3-infiltrated yttria stabilized zirconia oxygen electrode for reversible solid oxide fuel cells

Abstract: Porous Sr-doped lanthanum manganite–yttria stabilized zirconia (LSM–YSZ) oxygen electrode is prepared by an infiltration process for a reversible solid oxide fuel cell (RSOFC). X-ray diffraction and SEM analysis display that perovskite phase LSM submicro particles are evenly distributed in the porous YSZ matrix. Polarization curves and electrochemical impedance spectra are conducted for the RSOFC at 800 and 850 °C under both SOFC and SOEC modes. At 850 °C, the single cell has the maximum power density of ~726 mW/cm2 under SOFC mode, and electrolysis voltage of 1.35 V at 1 A/cm2 under SOEC mode. Fuel cell/water electrolysis cycle shows the cell has good performance stability during 6 cycles, which exhibits the LSM–YSZ oxygen electrode has high electrochemical performance and good stability. The results suggest that network-like LSM–YSZ electrode made by infiltration process could be a promising oxygen electrode for high temperature RSOFCs.

Composition and mode of occurrence of minerals in Late Permian coals from Zhenxiong County, northeastern Yunnan, China

Abstract: Minerals in the Late Permian coals from the Niuchang-Yigu mining area, Zhenxiong County, northeastern Yunnan, China, were investigated using optical microscopy and low temperature ashing plus X-ray diffraction (LTA + XRD). The results showed that minerals in the coal LTAs are mainly quartz, kaolinite, chamosite, mixed-layer illite/smectite (I/S), pyrite, and calcite, with trace amounts of marcasite, dolomite, and bassanite. The authigenic quartz generally occurs in collodetrinite or as a filling in cleats or cell cavities. This silica was mainly derived from aqueous solutions produced by the weathering of basaltic rocks in the Kangdian Upland and from hydrothermal fluids. The presence of β-quartz paramorph grains in collodetrinite probably indicates that these grains were detrital and came from a volcanic ash. Clay minerals are generally embedded in collodetrinite and occur as cell-fillings. Pyrite occurs as framboidal, anhedral, and euhedral grains and a cell-filling. The coals are high in pyrite and the high pyrite content probably results from seawater invading during the stage of peat accumulation. Calcite generally occurs as vein-fillings, indicating an epigenetic origin.

Experimental forward and reverse in situ combustion gasification of lignite with production of hydrogen-rich syngas

Abstract: This research focused on the feasibility of applying the forward and reverse combustion approach to the in situ gasification of lignite with the production of hydrogen-rich syngas (H2 and CO). The so-called forward combustion gasification (FCG) and reverse combustion gasification (RCG) approach in which oxygen and steam are simultaneously fed to the simulated system of underground coal gasification (UCG) was studied. A simulated system of UCG was designed and established. The underground conditions of the coal seam and strata were simulated in the system. The combustion gasification of lignite has been carried out experimentally for almost 6.5 days. The average effective content (H2 + CO) of syngas during the FCG phase was 62.31 % and the maximum content was 70.92 %. For the RCG phase the corresponding figures are 61.33 % and 67.91 %. Thus, the feasibility of using RCG way for UCG has been demonstrated. The temperature profiles have been provided by using of 85 thermocouples during the model experiment, which portrayed the several nephograms of thermal data in the gasifier were of significance for the prospective gasification processes.