Mathematical analysis of physicochemical phenomena in the catalyst during hydrogenating depolymerization of coal extract benzene insoluble fraction

Efficiency and selectivity of hydrogenating depolymerization of the coal extract benzene-insoluble part over the heterogeneous Co–Mo/Al2O3 catalyst were assessed using a mathematical model. The analytical equations of the mathematical model were generated based on material balance incorporating the physico-chemical phenomena(reaction and diffusion) both in the autoclave and the catalyst grain. The equations offer the possibility for predicting changes of the reactants in the autoclave during the process and for determining the distribution of reactant concentrations in the grain as a function of its radius. The analytical equations of the model serve as the basis of the algorithm for assessing the influence of restrictive diffusion on the effectiveness and selectivity of the catalyst, and also for defining the optimal radii of the catalyst's pores to enable free transport of reactants in the grain interior.

Oxidation of Lingwu Coal Extraction Residue in Aqueous Sodium Hypochlorite under Mild Conditions

To investigate the structural features and provide an alternative method for high value-added utilization of coal, Lingwu coal was first extracted with organic solvent at room temperature. Then its extraction residue was oxidized in aqueous sodium hypochlorite(ASHC) under mild conditions. The effects of oxidation conditions, such as temperature, reaction time, the ratio of Lingwu coal extraction residue(LCER, g) to ASHC(m L) and p H value, on the product distributions and compositions were investigated. The results of gas chromatography/mass spectrometry(GC/MS) suggested that 53 kinds of methyl esterified products were detected in total, and benzene carboxylic acids were the main oxidation products, while chloro-substituted benzene carboxylic acids were the main by-products. Higher yield and fewer kinds of organic acids could be obtained at lower p H value, especially for the main objective product, benzene carboxylic acids.

Rib stability: A way forward for safe coal extraction in India

Ensuring rib stability during pillar extraction is of prime importance in bord and pillar(B&P) method of underground coal mining with caving. Rib stability has been assessed here by way of assessing factor of safety(FOS), a ratio of the strength of rib to stress on it. Earlier formulations for rib stability when applied to case studies gave very low FOS value suggesting significant ground control problems, which were contrary to the field observations. This has necessitated the need to revisit the concept of rib stability. The stress coming on the rib is estimated with the use of numerical modeling technique using the FLAC^(3D) software. The methodology of assessing rib-stability with the help of suggested rib-strength formulation has been validated at eight Indian coal mines. The outcome of this study finds relevance and importance in ensuring underground coal liquidation with improved safety and conservation.

Extracting vanadium from stone-coal by oxygen pressure acid leaching and solvent extraction

Vanadium extraction from stone-coal was investigated by oxygen pressure acid leaching and solvent extraction.The mineralogy of the stone-coal from Tongren City of Guizhou Province,China,was investigated by various determination methods. The effects of leaching time,leaching temperature,leaching agent concentration,leaching L/S ratio,granularity of material,additive consumption were investigated based on the mineralogy.The results show that under the conditions of leaching time of 3-4 h, temperature of 150℃,sulfuric acid consumption of 25%?30%,ratio of liquid to solid of 1.2:1,the granularity less than 0.074 mm, additive consumption of 3%-5%,and oxygen pressure of 1.2 MPa,and the vanadium leaching rate can be more than 92%by the method of two-step pressurized acid leaching.The powdery V2O5 product with 99.52%in V2O5 content is obtained by the flowsheet of acid recovery,removing iron by reduction process,solvent extraction,precipitating vanadium with ammonium water,and pyrolysis from the stone-coal oxygen pressure acid-leaching solution.The total recovery efficiency of vanadium is above 85%,which is more than 20%higher than that obtained in the conventional process.Furthermore,the new process does not cause air pollution since no HCl or Cl2 is released by calcination of the raw material.

Definition, theory, methods, and applications of the safe and efficient simultaneous extraction of coal and gas

Simultaneous extraction of the coal and gas is an effective method of eliminating coal mine gas disasters while safely exploiting the coal and achieving efficient gas drainage in China, which is widely accepted by the main coal-producing countries around the world. However, the concrete definition of simultaneous extraction is vague and there is little accurate theoretical support for the simultaneous extraction of coal and gas, which makes it difficult to determine an efficient gas drainage method appropriate to the features of coal seams. Based on theoretical analysis, laboratory tests and field observations, a specific definition of simultaneous extraction of coal and gas is proposed after analyzing the characteristics of coal seam occurrences in China, and we developed the mechanism of mining-enhanced permeability and established the corresponding theoretical model. This comprises a process of fracture network formation, in which the original fractures are opened and new fractures are produced by unloading damage. According to the theoretical model, the engineering approaches and their quantitative parameters of ＇unloading by borehole drilling＇ for single coal seams and ＇unloading by protective seam mining＇ for groups of coal seams are proposed, and the construction principles for coal exploitation and gas-drainage systems for different conditions are given. These methods were applied successfully in the Tunlan Coal Mine in Shanxi Province and the Panyi Coal Mine in Anhui Province and could assure safe and efficient simultaneous extraction of coal and gas in these outburst coal mines.

A new process of extracting vanadium from stone coal

A new process of extracting vanadium from the stone coal vanadium ore in Fangshankou, Dtmhuang area of Gansu Province, China was introduced. Various leaching experiments were carried out, and the results show that the vanadium ore in Fangshankou is difficult to process due to its high consumption of acid and the high leaching rate of impurities. However, the leaching rate can be up to 80% and the content of V2O5 in the residue can be between 0.22%-0.25% in the process of ore fme grinding→oxidation roasting→mixing and ripening→aqueous leaching→P2O4 solvent extraction→sulfuric acid stripping→oxidation and precipitation→decomposition by heat. Also, the quality of flaky V205 produced by this process can meet the requirements of GB3283--87. The total leaching rate of vanadium is 70%. Also, three types of wastes are easy to treat. The vanadium extraction process is better in relation to the aspect of environmental protection than the sodium method.

XPS analysis and combustibility of residues from two coals extraction with sub-and supercritical water

Two kinds of residues,obtained from extraction of one weakly reductive coal,Shenfu-Dongsheng coal(SD),and one reductive coal,Pingshuo coal(PS),with sub-and supercritical water on a semi-continuous apparatus,were characterized by calorific value analysis and XPS analysis,and the combustion behaviors of residues were investigated by thermogravimetric analysis.The results show that the residues have higher calorific value than raw coal samples,and SD residue has higher calorific value than PS residue.C-C,C-O and pyridinic nitrogen,pyrrolic nitrogen are the dominant form of C,O and N on the surface of raw coal samples and their extraction residues.The combustion behaviors of extraction residues show that the SD residue is more reactive and more easily burned than PS residue.

Technique of coal mining and gas extraction without coal pillar in multi-seam with low permeability

Aimed at the low mining efficiency in deep multi-seams because of high crustalstress,high gas content,low permeability,the compound 'three soft' roof and the trouble-somesafety situation encountered in deep level coal exploitation,proposed a new idea ofgob-side retaining without a coal-pillar and Y-style ventilation in the first-mined key pressure-relieved coal seam and a new method of coal mining and gas extraction.The followingwere discovered:the dynamic evolution law of the crannies in the roof is influenced bymining,the formative rule of 'the vertical cranny-abundant area' along the gob-side,thedistribution of air pressure field in the gob,and the flowing rule of pressure-relieved gas ina Y-style ventilation system.The study also established a theoretic basis for a new miningmethod of coal mining and gas extraction which is used to extract the pressure-relievedgas by roadway retaining boreholes instead of roadway boreholes.Studied and resolvedmany difficult key problems,such as,fast roadway retaining at the gob-side without a coalpillar,Y-style ventilation and extraction of pressure-relieved gas by roadway retainingboreholes,and so on.The study innovated and integrated a whole set of technical systemsfor coal and pressure relief gas extraction.The method of the pressure-relieved gasextraction by roadway retaining had been successfully applied in 6 typical working faces inthe Huainan and Huaibei mining areas.The research can provide a scientific and reliabletechnical support and a demonstration for coal mining and gas extraction in gaseous deepmulti-seams with low permeability.

The mechanism and products for co-thermal extraction of biomass and low-rank coal with NMP

The high-value utilization of low-rank coal would allow for expanding energy sources,improving energy efficiencies,and alleviating environmental issues.In order to use low-rank coal effectively,the hypercoals(HPCs)were co-extracted from two types of low-rank coal and biomass via N-methyl-2-purrolidinone(NMP)under mild conditions.The structures of the HPCs and residues were characterized by proximate and ultimate analysis,Raman spectra,and Fourier transform infrared(FT-IR)spectra.The carbon structure changes within the raw coals and HPCs were discussed.The individual thermal dissolution of Xibu(XB)coal,Guandi(GD)coal,and the biomass demonstrated that the biomass provided the lowest thermal dissolution yield Y1 and the highest thermal soluble yield Y2 at 280℃,and the ash content of three HPCs decreased as the extraction temperature rose.Co-thermal extractions in NMP at various coal/biomass mass ratios were performed,demonstrating a positive synergic effect for Y2 in the whole coal/biomass mass ratios.The maximum value of Y2 was 52.25wt% for XB coal obtained with a XB coal/biomass of 50wt% biomass.The maximum value of Y2 was 50.77wt% for GD coal obtained with a GD coal/biomass of 1:4.The difference for the optimal coal/biomass mass ratios between XB and GD coals could be attributed to the different co-extraction mechanisms for this two type coals.

Technical evaluation system of co-extraction of coal and gas

Coal and gas are two important resources in China,and it is an effective way to recycle them with the method of co-extraction of coal and gas.In view of actual situation of China's co-extraction of coal and gas,this research adopts the science evaluation of gas extraction of coal by the method of quantitative evaluation,and preliminarily establishes the technical evaluation system of co-extraction of coal and gas.Technical evaluation system of co-extraction of coal and gas includes safety evaluation,economic evaluation and resource recovery evaluation in the process of mining coal and gas.In addition,this paper results in the selected evaluation parameters and target functions that are used in the three evaluation methods.The establishment of evaluation system for co-extraction of coal and gas plays an important theoretical significance and guiding role in co-extraction of coal and gas for China's coal enterprises.

Comparison of the mechanisms of microwave roasting and conventional roasting and of their effects on vanadium extraction from stone coal

Experiments comparing microwave blank roasting and conventional blank roasting for typical vanadium-bearing stone coal from Hubei Province in central China, in which vanadium is present in muscovite, were conducted to investigate the effects of roasting tempera- ture, roasting time, H2SO4 concentration, and leaching time on vanadium extraction. The results show that the vanadium leaching efficiency is 84% when the sample is roasted at 800℃ for 30 min by microwave irradiation and the H2SO4 concentration, liquid/solid ratio, leaching temperature, and leaching time are set as 20vo1%, 1.5：1 mL.g-1, 95℃, and 8 h, respectively. However, the vanadium leaching efficiency achieved for the sample subjected to conventional roasting at 900℃ for 60 min is just 71% under the same leaching conditions. Scanning electron microscopy （SEM） analysis shows that the microwave roasted samples contain more cracks and that the particles are more porous compared to the conventionally roasted samples. According to the results of X-ray diffraction （XRD） and Fourier-transform infrared （FTIR） analyses, neither of these roasting methods could completely destroy the mica lattice structure under the experimental conditions; however, both methods deformed the muscovite structure and facilitated the leaching process. Comparing with conventional roasting, microwave roasting causes a greater deformation of the mineral structure at a lower temperature for a shorter roasting time.

Effect of vanadium occurrence state on the choice of extracting vanadium technology from stone coal

The extraction technology of vanadium from stone coal by means of no-salt-roasting and dilute acid solution leaching treatment has the advantages of low pollution, low investment, as well as high vanadium leaching efficiency, which makes it the best technology for extending application. In the present study, the effects of vanadium occurrence state in stone coal, roasting temperature and additive agent on the leaching efficiency of vanadium were studied. The results indicate that the effect of vanadium occurrence state on the extracting vanadium technology is obvious. If the vanadium component in stone coal existed in amorphous phase form, this type of stone coal can be treated by no-slat-roasting and dilute acid solution leaching technology; while the vanadium-bearing crystalline phase existed in stone coal, the roasting additive must be added to destroy this crystalline form so as to acquire high vanadium leaching rate.

Supported liquid membrane extraction to treat coal gasification wastewater containing high concentrations phenol

The hollow fiber supported liquid membrane extraction was introduced to treat coal gasification wastewater to recover phenolic compounds,with tributyl phosphate (TBP) as carrier,kerosene as the membrane solvent,sodium hydroxide solution as the stripping agent and PVDF as the membrane material. Factors having strong impact on the extraction efficiency were studied in detail,including the mass transfer mode,twophase flow rate,stripping phase concentration. As extraction system with 20% TBP-kerosene,parallel flow mass transfer,stripping phase concentration 0.1 mol/L,the optimal operating conditions could be obtained. Under the optimum operating conditions,the time required to reach equilibrium for the extraction is 50 min, and extraction efficiency of phenol is 86. 2% and the phenol concentration of effluent is 98.64 mg/L.

Current situation of simultaneous coal and methane extraction tech- nology in pressure-relieved coalbed group

The importance of simultaneous coal and methane extraction and its significance on green exploitation is stated, and current research situation of simultaneous coal and methane and faced new problems are introduced. The research progress on movement of overlying strata and stresses change in them, cracks development during mining in overlying strata and meth- ane emission under disturbance of mining as well as the changing rules of permeability and methane flow under the disturbance of mining is analyzed. The progress on practice of simultaneous coal and methane extraction is analyzed. The deficiencies of current research and further researching fields on simultaneous coal and methane extraction are pointed out.

Effect of Temperature on Phase and Alumina Extraction Efficiency of the Product from Sintering Coal Fly Ash with Ammonium Sulfate

A new developed technology for extracting alumina from coal fly ash was studied in this paper. In this technology, coal fly ash is first sintered with ammonium sulfate, forming ammonium aluminum sulfate in the resultant product, where alumina can be easily leached without using any strong acid or alkali. The products obtained under different sintering conditions were characterized by X-ray diffractometry. Alumina extraction efficiency of these products was also investigated. The results show that the sintering temperature and time substantially influence the phase composition and alumina extraction efficiency of sintered products, while the heating rate has little influence. The optimal sintering condition is 400 °C for 3 h in air with a heating rate of 6 °C·min-1.Under the optimal sintering condition, the alumina extraction efficiency from as-sintered coal fly ash can reach 85% or more.

Influence of Water Injection Fracturing on Crack Damage in Soft Coal and Application in Gas Extraction

In order to study the hypotonic and rheological particularity of “three soft” coal seam in west Henan, China, this paper explored the stress and damage characteristics of crack in coal under condition of water injection fracturing based on ABAQUS platform;The cohesive element in T-P damage evolution criterion was used to describe the approximately linear relationship between crack width and extending distance in soft coal. The simulation results show that stress evolution and crack damage in soft coal is a gradually developing process under condition of water injection fracturing. When the static pressure is 4 - 10 MPa, and the injection time is about 1 - 2 hours, the damage range of crack in soft coal can basically reach an ideal data of 80 - 100 m, and then greatly improve the hypotonic performance of “three soft” coal seam.

Characteristics and applications of gas desorption with excavation disturbances in coal mining

According to the deficiency of experiment system for gas adsorption and desorption in coal mass, a large scale experiment system is developed independently by researchers. This experiment system is composed of primary and auxiliary boxes, power transmission system, mining system, loading system, gas charging system, data monitoring and intelligent acquisition system. The maximum experiment coal consumption is 1200 kg, the mining system is developed to conduct experiment for gas desorption under excavating disturbance, and the plane-charging cribriform ventilation device is developed to realize uniform ventilation for experiment coal sample, which is accord with the actual gas source situation of coal bed. The desorption characteristics of gas in coal are experimentally studied under the conditions of nature and mining using the experiment system. The results show that, compare with nature condition, the permeability of coal and the velocity of gas desorption could significantly increase under the influence of coal pressure relief and destruction caused by mining, and the degree of gas desorption could somewhat increase too. Finally, pressure relief gas extraction of current seam and adjacent seams after mining in a certain coal mine of Yangquan mining area are introduced, and the gas desorption experiment results is verified by analyzing the effect of gas extraction.

中国HyperCoal清洁高值化应用研究现状与展望

作为一个煤炭大国,煤炭在我国的能源结构中占据重要地位.然而,煤炭的过度使用不可避免的造成了环境污染和温室效应等问题.因此发展洁净煤技术是解决煤炭利用问题的重要方式,对于我国经济的可持续发展至关重要.HyperCoal(HPC)是通过溶剂萃取技术得到的一种煤衍生物,由于具有低灰、低水、高热值、高反应性、良好热塑性、环境友好等特性,在洁净煤技术中有着重要的应用.基于此,本文指出了目前我国对HPC的应用研究现状,并详细阐述了本研究团队在配煤炼焦和制备石墨电极领域的突破性研究进展.然而,目前HPC在推广和应用过程中还存在一些问题.在未来,还亟需解决HPC的规模化生产问题,并对HPC的萃取机理和作用机制开展更加深入的研究.

Hydraulic drill hole reaming technology with large flow and draining of coal mine gas

This paper takes Zhaozhuang mine in Shanxi province as an example to study the technology of hydraulic reaming drill hole for improving the gas extraction.The influence of the physical properties of coal seam on the hydraulic reaming drill holes and the draining of coal mine gas were analyzed and discussed for different coal structure areas,and the following conclusions were made.Hydraulic drill hole reaming has had a positive impact in Zhaozhuang Mine,and can improve the efficiency of gas extraction to different degrees.The water jet pressure used in hydraulic drill hole reaming mainly depends on the structure of the coal.When the coal seam basically becomes integrated,the critical water jet pressure increases,the discharge becomes relatively easy to achieve,the blocking effect on the gas extraction decreases,and the gas extraction significantly increases after the reaming process.When the coal seam is broken,the critical water jet pressure decreases,the discharge becomes difficult to achieve,the blocking effect on the gas extraction becomes obvious,and the gas extraction changes slightly after reaming.

Underground mining of thick coal seams

This paper reviews underground mining methods for total thickness of a thick coal seam in single lift （TI＇rCSSL）. Review shows the required engineering for extraction of thick seams needs to be fitted with thickness of the seam, behavior of rock-mass and surrounding stress conditions for efficient mining. Variants of TI＇rCSSL are able to extract a maximum 10-12 m thickness only. An improvement in bending moment of the overlying coal band in longwall top coal caving （LTCC） provides better under-winning opportunity for the roof coal band. An acceptable limit of 25 MPa compressive strength of coal for the success of LTCC may be increased under favorable geo-technical conditions. Bord and pillar in India adopted induced caving of roof coal band for single lift depillaring of total thickness （SLDTr） of a compe- tent thick coal seam developed along floor. Case studies are given to arrest the adverse effects of extrac- tion height on pillars.