隔爆面三要素审查分析

结合国家标准GB3836.2-2010对隔爆型电气设备的要求,介绍了隔爆外壳的防爆原理,指出了隔爆面审查中容易疏忽的问题,分析了隔爆三要素的审查方法,并以电动机为例进行详细阐述,为隔爆型产品的设计和审查人员提供参考。1.引言煤矿瓦斯气体环境中采用Ⅰ类电气设备;除煤矿瓦斯气体外的其他爆炸性气体环境采用Ⅱ类电气设备,其中Ⅱ类电气设备,可以进一步细分为ⅡA类、ⅡB类、ⅡC类(中华人民共和国国家质量监督检验检疫总局;中国国家标准化委员会,GB 3836.1-2010,爆炸性环境第1部分:设备通用要求[S].北京:中国标准出版社,2011)。

各有所得 中美签326亿美元协议

第二次中美战略经济对话后,美国财政部从扩大市场准入、开放金融部门、增进能源安全、保护环境、强化法制等5个方面总结了此次对话的成果。在此次对话期间,中国方面为了在“

Prevention of explosion in coal mine and management of coal mine gas

There are many problems in terms of safe coal production and the sound developmentof the coal industry.Accompanying the intensification and increasing efficiencyof coal production and the conducting of mining operations at deeper and more remoteareas of mines,the efficient recovery and utilization of Coal Mine Methane:(CMM) is animportant issue in improving and stabilizing the productivity in the coal mining industry withhigh levels of gas,where the incidence of gas outbursts is increasing.We plan to studyvarious aspects of the development of production technology and characteristics of themine site.This is to establish the technology for highly efficient coproduction coal and gasoperation rate.As a result,the productivity at the coal mine face will increase due to thereduction in gas emissions in the mining face.Effective use of recovered gas can be expectedto reduce global warming by reducing the amount of coal mine methane gas emissionin the air.

Study of 3-D Numerical Simulation for Gas Transfer in the Goaf of the Coal Mining

In order to simulate field distribution rules,mathematical models for 3-D air flows and gas transfer in the goaf of the coal mining are established,based on theories of permeability and dynamic dispersion through porous media. A gas dispersion equation in a 3-D field is calculated by use of numerical method on a weighted upstream multi-element balance. Based on data of an example with a U type ventilation mode,surface charts of air pressure distribution and gas concentration are drawn by Graphtool software. Finally,a comparison between actually measured results in the model test and the numerical simulation results is made to proves the numerical implementation feasible.

CONTROL OF GAS EMISSION AT COAL FACE IN CHINA

All the underground coal mines in China are gassy mines. The gas emission at coal face increasingly grows with the increase of working depth and coal output, for example, the gas emission at a full mechanized coal face of mine No. 2 at Yongquan with a daily output of 2. 000t/d is up to 66-72m2/min. Special gas emission phenomena such as gas blowout, gas and coal outburst etc. have occurred at some faces, which threatens the safe production of face. obstructs the growth of productivity and limits the full play of mechanized equipment.In this paper, gas at face is divided, according to its origin, into three constituents, namely , coming from the coal wall, mined coal and goaf;and a formula for calculation is given. Also , the characteristics of the variation of gas emission at coal face, and the influence of mining sequence of a group of seams and supplied air quantity on the gas emission are discussed. Furthermore . based on the regularity of gas emission at coal face from the above three sources, and on the experiences of years, three principles on controlling gas emission at coal face are presented, that are managing the gas on classification basis, harnessing each source separately and comprehensive prevention and control. Finally, technical measures for prevention and treatment of the accumulation of gas in the upper corner of face, at the working place of coal-winning machine and in the bottom trough of conveyor are introduced.

Application of causality diagram in system safety analysis

Causality Diagram (CD) is a new graphical knowledge representation based on probability theory. The application of this methodology in the safety analysis of the gas explosion in collieries was discussed in this paper, and the Minimal Cut Set, the Minimal Path Set and the Importance were introduced to develop the methodology. These concepts are employed to analyze the influence each event has on the top event ? the gas explosion, so as to find out about the defects of the system and accordingly help to work out the emphasis of the precautionary work and some preventive measures as well. The results of the safety analysis are in accordance with the practical requirements; therefore the preventive measures are certain to work effectively. In brief, according to the research CD is so effective in the safety analysis and the safety assessment that it can be a qualitative and quantitative method to predict the accident as well as offer some effective measures for the investigation, the prevention and the control of the accident.

Sponge Effect on Coal Mine Methane Separation Based on Clathrate Hydrate Method

The findings were presented from laboratory investigations on the hydrate formation and dissociation processes employed to recover methane from coal mine gas.The separation process of coal mine methane(CMM) was carried out at 273.15K under 4.00 MPa.The key process variables of gas formation rate,gas volume stored in hydrate and separation concentration were closely investigated in twelve THF-SDS-sponge-gas systems to verify the sponge effect in these hydrate-based separation processes.The gas volume stored in hydrate is calculated based on the measured gas pressure.The CH4 mole fraction in hydrate phase is measured by gas chromatography to confirm the separation efficiency.Through close examination of the overall results,it was clearly verified that sponges with volumes of 40,60 and 80 cm 3 significantly increase gas hydrate formation rate and the gas volume stored in hydrate,and have little effect on the CH4 mole fraction in hydrate phase.The present study provides references for the application of the kinetic effect of porous sponge media in hydrate-based technology.This will contribute to CMM utilization and to benefit for local and global environment.

STUDY ON THE METHOD FOR FORECASTING DANGEROUSNESS OF COAL FACE AND HEADING FACE OUTBURST BY TWO TEMPERATURE INDEXES

In line with the sensitivity of coal drillings temperature and coalbed temperature to the dangerous zone of coal and gas outburst, two temperature sensitive indexes (△Tm, △tm) for forecasting dangerousness of coal face and heading face outburst are defined, and deal with the foundation on drillings and coalbed temperatures used as sensitive indexes and the principle and method of determining drillings and coalbed temperatures. On the basis of this, we put forward the method for forecasting dangerousness of coal face and heading face outburst by two temperature sensitive indexes and determine the critical values of two temperature sensitive indexes (△Tm= 5.5℃, △tm = 4.5℃) by in-situ observation and requirement for determining sensitive index.

Influence of magma intrusion on gas outburst in a low rank coal mine

The effect of magma intrusion on gas outburst is illustrated by a case study of the exposed magma intru- sion in the 313 mining area, upper coal seam Number 3, in the Qiwu Mine located in Shandong province. Vitrinite reflectance, mercury injection, and maceral statistical analysis are used to characterize the coal. The aspects of coal metamorphism include changes in micro-components as well as in coal structure, the formation of new substances, and changes in gas absorption and storage. The results show that vitrinite reflectance increases within the region influenced by magma intrusion. The metamorphosed region may be divided into a weakly affected belt, a medium affected belt, a strongly affected belt, and a completely affected belt. Compared to the unaffected coal the total pore volume, as well as the amount of big and middle sized holes, increases while the number of transition holes and micro-pores decreases. This diminishes the absorption capacity of the matrix but enlarges the total gas storage space. Vitrinite con- tent initially decreases slightly but then increases rapidly while the inertinite content increases at first but then decreases. Exinite content decreases, then increases, and finally drops to zero. Higher vitrinite, and a lower inertinite, content increase gas absorption ability. This balances reduced adsorption caused by changes to pore structure. Consequently, gas adsorption capacity is not substantially reduced as the coal rank increases. Thermal metamorphism of the coal produces CH4 and other hydrocarbons that increase the total gas content in the coal seam. Asphaltene migrates into the medium and weakly affected regions filling in the pores and fractures there. This plugs the pathway for gas transport. A barrier is formed that hinders gas flow. C02, H2S, N2, and other gases carried in by the magma react to produce C02, which increases in relative concentration and enhances the risk of gas outburst. The two barriers, magma intrusion on one side and the medium and weakly affected belts on the other, as well as the unaf- fected coal seam itself, trap a large amount of gas during the thermal activity. This is the basic reason for gas outburst. These conclusions can enlighten activities related to gas prevention and control in a low rank coal mine affected by ma^ma intrusion.

The control of coal mine gas and coordinated exploitation of coal bed methane in China

Based on the characteristics of the coalfield geology and the distribution of coalbed methane (CBM) in China,the geological conditions for exploiting the CBM and drainingthe coal mine gas were analyzed,as well as the characteristics of CBM production.Bycomparing the current situation of CBM exploitation in China with that in the United States,the current technology and characteristics of the CBM exploitation in China were summarizedand the major technical problems of coal mine gas control and CBM exploitationanalyzed.It was emphasized that the CBM exploitation in China should adopt the coalmine gas drainage method coordinated with coal mine exploitation as the main model.Itwas proposed that coal mine gas control should be coordinated with coal mine gas exploitation.The technical countermeasure should be integrating the exploitation of coal andCBM and draining gas before coal mining.

STUDY ON MATHEMATICAL MODEL OF GAS EXPLOSION IN COAL MINE

Based on the principle of gas explosion in underground coal mine, mutation theory and mathematic method were adopted to establish" Mathematical model of coal mine gas explosion"and advanced some new concepts and ideas. The model can simply and precisely indicates underground air status and conforms to part of experimental data, provided a new method for research and experiment of explosion disaster theory.

Study on comprehensive gas control techniques and practice in coal mines

The origins and main control methods of gas in coal seams were introduced cursorily, and the processes that need to be done in controlling gas, which includes prediction of gas emissions, drainage systems, the means of prevention of gas outbursts, and some suggestions were put forward. The characteristic of different gas emissions and the corresponding counter measures were presented, and ＆ case study of simultaneous extraction of coal and gas in Xieyi Coal Mine was carried out by coal mining and gas extraction without coal-pillar. The field application shows that gas drainage ratio in panel 5121（0） averages about 90% and reaches as high as 95~/0, which will give beneficial references to gas control in coal mines.

Modeling and prediction of daily gas concentration variation at a mining face based on the elliptic orbit model: A case study

Monitoring and analysis of daily gas concentrations at a mining face is a vital task on safety production and security management in the coal-mining industry. This study addresses modeling and prediction of daily gas concentration variations based on the elliptic orbit model. The model describes the hourly variation in daily gas concentration by mapping its time-series into the polar coordinates to create its elliptic orbit trace for further analysis. Experiments show workability of the proposed method that daily gas concentration variation at a mining face of one coal mine in China is well described by the elliptic orbit model. Result analysis and performance comparison of the proposed elliptic orbit model with the classical AR model on the same prediction tasks indicate potentiality of the proposed elliptic orbit model,which presents a vivid approach for modeling and forecasting daily gas concentration variations in an intuitive and concise way.

Research on time structure characteristic of gas concentration sequence in the working face

In the procedure of coal industry production, the losses of the persons and economy caused by the gas explosion accidents are most serious, therefore, prevention and control of the gas explosion accident of the coal mines is an important issue needed to be solved urgently in the safety production work of our coal mines. The characteristic of time structure variation index characteristic was analyzed about gas concentration sequence of three measure points in the NO. 1I 1024 working face. It was found that the value of time variation about three measure points was mostly 1〈δ≤1.5, and gas emission presented consistently strong-clustering state twice, and the value of time variation presented continuous variation state in the active stage of gas concentration. Complex characteristics of the value indicated gas emission was continuously variable in time or space and presented the complex nonlinear characteristics. So the characteristic about gas emission system was correctly depicted and analyzed to gas emission system according to the relation of its state variation and essential of nonlinear system. The result also provided reliable warranty for its continued nonlinear research on gas emission.