SD-80型可伸缩胶带输送机的技术改进

可伸缩胶带输送机是综掘队组使用的主要运输设备。分析了对可伸缩胶带输送机的拦人保护装置、胶带头封煤装置、信号控制系统、防跑偏装置及游动小车的技术改进,指出,通过改进可有效降低胶带输送机的事故率,提高煤矿经济效益。

Anatomically-preserved Lepidodendralean Plants from Permian Coal Balls of China: Sigillariopsis Scott

Three kinds of anatomically_preserved lepidodendralean leaves from Permian coal balls of China were studied. They all have double xylem strands, which is consistent with the genus Sigillariopsis Scott. Compared with the species of Sigillariopsis , they are considered as three new species: S. shanxiensis sp. nov. and S. taiyuanensis sp. nov. from Coal Seam 7 in the upper part of the Taiyuan Formation (lower Lower Permian), Xishan Coal Field, Taiyuan, Shanxi Province and S. guizhouensis sp. nov. from Coal Seam 1 in the Wangjiazhai Formation (upper Upper Permian), Shuicheng Coal Mining District, Guizhou Province. Based on the associated organs of lepidodendraleans other than leaves and the information of the Euramerican lepidodendraleans, the affinities of the three new species of Sigillariopsis are discussed and they are probably leaves of Sigillaria Brongniart. In Euramerican Flora, Sigillaria (including its leaves Sigillariopsis ) mainly lived in the Carboniferous period and in the Cathaysian Flora they lived in the Upper Carboniferous to upper Upper Permian periods in rare localities. The leaves and fertile organs of Sigillaria have not been reported from the Cathaysian Flora to date. Three new species of the Permian anatomically_preserved leaves of Sigillaria not only increase the diversity of the Cathaysian sigillarian but also bear important significance on the evolution of sigillarian plants and the relationship of the Cathaysian and Euramerican lepidodendraleans.

Quick determination of gas pressure before uncovering coal in cross-cuts and shafts

The determination of gas pressure before uncovering coal in cross-cuts and in shafts is one of the important steps in pre- dicting coal and gas outbursts. However, the time spent for testing gas pressure is, at present, very long, seriously affecting the ap- plication of outburst prediction techniques in opening coal seams in cross-cuts and shafts. In order to reduce the time needed in gas pressure tests and to improve the accuracy of tests, we analyzed the process of gas pressure tests and examined the effect of the length of boreholes in coal seams in tests. The result shows that 1) the shorter the borehole, the easier the real pressure value of gas can be obtained and 2) the main factors affecting the time spent in gas pressure tests are the length of the borehole in coal seams, the gas emission time after the borehole has been formed and the quality of the borehole-sealing. The longer the length of the bore- hole, the longer the gas emission time and the larger the pressure-relief circle formed around the borehole, the longer the time needed for pressure tests. By controlling the length of the borehole in a test case in the Huainan mining area, and adopting a quick sealing technique using a sticky liquid method, the sealing quality was clearly improved and the gas emission time as well as the amount of gas discharged greatly decreased. Before the method described, the time required for the gas pressure to increase during the pressure test process, was more than 10 days. With our new method the required time is only 5 hours. In addition, the accuracy of the gas pressure test is greatly improved.

Effects of caprock sealing capacities on coalbed methane preservation:Experimental investigation and case study

Caprocks play an important role in the trapping of coalbed methane(CBM)reservoirs.To study the sealing capacities of caprocks,five samples with different lithologies of Neogene clayrock,Paleogene redbeds,Permian sandstone,Permian mudstone and Permian siltstone were collected and tested using experimental methods of microstructure observation,pore structure measurement and diffusion properties determination.Results indicate that with denser structures,lower porosities,much more developed micropores/transition pores and higher pore/throat ratios,mudstone and siltstone have the more ideal sealing capacities for CBM preservation when comparing to other kinds of caprocks;the methane diffusion coefficients of mudstone/siltstone are about 6 times higher than sandstone and almost 90 times higher than clayrock/redbeds.To further estimate the CBM escape through caprocks,a one-dimensional CBM diffusion model is derived.Modeling calculation result demonstrates that under the same thickness,the CBM sealing abilities of mudstone/siltstone are almost 100 times higher than those of clayrock/redbeds,and nearly 17 times higher than sandstone,which indicates that the coal seam below caprocks like clayrock,redbeds or sandstone may suffer stronger CBM diffusion effect than that below mudstone or siltstone.Such conclusion is verified by the case study from III3 District,Xutuan Colliery,where the coal seam capped by Paleogene redbeds has a much lower CBM content than that capped by the Permian strata like mudstone,siltstone and sandstone.

Rules of variation in hydrogen during reignition of underground fire zones of spontaneous coal combustion

In light of the possibility of reignition when unsealing the closed fire zones, the occurrence of reignition was simulated by a home-made experimental device, hydrogen variety rule from combustion to unsealing was analyzed, the three-stage generation model of hydrogen during reignition in fire zone was put forward and the probability that hydrogen was taken as an indicator gas was discussed. The results show that: when fire zone is ready to unseal, which is filled with hydrogen at a high concentration, it is more prone to reignite.

Assessment of sealed fire states by fire characteristic

The paper presented assessment of sealed fire states in underground coal mines by so-called 'fire characteristic', which graphically described tendencies of fire gas components-oxygen, nitrogen, carbon dioxide, carbon monoxide and hydrocarbons-in time. In order to mark gas components tendencies in time the authors applied the time series analysis. The case studied confirmed, that analysis of fire gas components tendencies in time and their correlation allow to elicit proper conclusions about fire state assessment. Assessment of fire states based on single value of fire indexes without considering their trends in time and correlation between trends of gas components would give wrong results The suggested method can appropriately indicate fire states in a sealed area.

Optimal design of heat exchanger header for coal gasification in supercritical water through CFD simulations

Heat exchangers play an important role in supercritical water coal gasification systems for heating feed and cooling products. However, serious deposition and plugging problems always exist in heat exchangers. CFD modeling was used to simulate the transport characteristics of solid particles in supercdtical water through the shell and tube of heat exchangers to alleviate the problems. In this paper, we discuss seven types of exchangers CA, B, C D, E, F and G）, which vary in inlet nozzle configuration, header height, inlet pipe diameter and tube pass distribution. In the modeling, the possibility of deposition in the header was evaluated by accumulated mass of particles; we used the velocity contour of supercritical water （SCW） to evaluate the uniformity of the velocity dis- tribution among the tube passes. Simulation results indicated that the optimum heat exchanger had structure F, which had a rectangular configuration of tube pass distractions, a bottom inlet, a 200-mm header height and a 10-ram inlet pipe diameter.

New technology of determining coalbed gas content by reversion seal coring

The key of the direct method of determining coalbed gas content is how to shorten the coal core exposure time in the sampling progress and reduce measuring error of gas content which comes from the calculation of losing gas content. The coring tests were carried out in No.24 drilling field of 715 floor gateway in Qinan Coal Mine by using traditional drill core bar- rel sampler and self-designed reversion seal coring equipment. The losing gas content was calculated by power functional method, and the gas content of two coring methods was determined, respectively. Results show that, compared with traditional drill core barrel sampling, the newly seal coring equipment can significantly shorten the coal core exposure time, the 30 min desorption gas content increases obviously, the calculation of losing gas content reduces by 56.99%, the desorption gas content in normal atmosphere increases by 113.24%, and the determining value of gas content increases by 10.06%. The new technol- ogy has much higher accuracy, and it is worthwhile to be popularized.

ANALYSIS OF ABILITY FOR IGNITING METHANE OF WATER-CARRYING EXPLOSIVES

In this paper, the ability to ignite methane of water-carrying explosives is discussed in detail. The difference of the safety towards methane of water- carrying explosives and ammonite is analysed comparatively. lt is shown that the process of detonation reaction, the duration of fIame by combustible residues of detonation and the fineness of cooling salt in detonation products are important factors of the safety of explosive towards methane. Water-carrying explosives are safer than ammonite used in coal mines.

Flue Gas CO_2 Emission Reduction Technologies and Applications

The current status and trend of CO2 emission from coal-fired power plants in China are introduced. Main flue gas decarbonization technologies and their prospective of applications in China are discussed in two separate parts-capture and sequestration. It is stated that the selection of CO2 capture and sequestration technologies relates closely with the geographical location of power plants, with the destination of CO2 being the key. Further, it is suggested that industrialized test centers or test platforms of national or industrial level should be set up.

Self-extinguishing behavior of Kerosene Spray Fire in a Completely Enclosed Compartment

The self-extinguishing behavior of kerosene spray fire was investigated in a completely enclosed compartment with the size of 3 m× 3 m × 3.4 m. The spray was generated by locating one BETE nozzle at the center of the bottom wall. A series of spray fire videos were obtained by changing BETE nozzle type and injecting pressure. The results show that spray ftre undergoes four stages： the growth stage, the quasi-steady stage, the stretch stage and the self-extinguishing stage. Consumption of large quantities of oxygen causes spray fire to first be stretched and then quench. In this process, fire base migrates away from spray region and leads to the emergence of ghost- hag fire. Ghosting fire promotes the instability of spray fire and large fluctuation of its height, which provides help to its self-extinguishing. With increasing the injecting pressure or the nozzle diameter, the self-extinguishing time decreases. It is found that the self-extinguishing time is approximately in inverse relation with injecting flow rate. Additionally, we also observed the occurrence of two-phase de flagration just after ignition, and it accelerates the spray fire growth and induces a larger fire height than the following quasi-steady spray fire. The deflagration turns stronger with increasing the injecting pressure.