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In situ strength of coal bed based on the size effect study on the uniaxial compressive strength
In the early 1990s, the Foundation for Science and Technology of Rio Grande do Sul State (CIENTEC) developed a pioneering study in Brazil, related to the simultaneous mining of multiple coal seams. One of the activities included detailed studies on the geomechanical characterization of materials present in the Irapua coal seam, under exploitation in the A-Sangao Mine, located near the city of Criciuma-SC, within the South-Catarinense coalfield. The goal of the laboratory tests was to define the behavior of the uniaxial compressive strength of the Irapua coal seam and establish a first approximation for the in situ strength value of this coal seam, since existing knowledge is solely based on practical mining experience over the years. Large samples of the coal seam were collected, using special techniques to maintain the integrity of the material, and a set of 56 uniaxial compression tests in cubic specimens, with side length ranging from 4.5 to 31 cm, were conducted in laboratory. This paper describes the experimen-tal techniques used in the assays, and also presents the uniaxial compression strength results obtained. Moreover, important aspects of this type of study are considered, highlighting the size effect for the carbonaceous bed and the estimation of in situ strength values for the Irapua coal seam....
2020-06-12 16:18:22浏览：1402
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Resarch and Development of Hot Primary Air Heater for Coal-Fired Boilersin Power Plant
The reasons of introducing cold air into pulverizer are analyzed for boilers with large capaciiy and high parameters.The temperature rises of the exhaust gas are calculated when varying the amount of the cold air.The hot primary air heater,a new technology,is developed to eliminate the cold air from the pulverized coal system.The applications,advantages and disadvantages are introduced in detail for the new device and system.It is concluded that introducing cold air into pulverizer is one of the major factors that causes the exhaust gas temperature of boilers with large capacity to be high.The amount of the cold air could be reduced significantly,even to zero in some cases by adopting the hot primary air heater,which drops the exhaust gas temperature of the boiler effectively.The hot primary air heater,which could play part roles of the steam-air heater or the hot air recirculation system,could also be used to adjust the exhaust gas temperature within the range of 20 ℃ by controlling the flow rate of the cooling medium.Moreover,the startup period of the steam-air heater or the hot air recirculation system will be shortened,which is a unique advantage of the hot primary air heater among the measures to drop the exhaust gas temperature....
2020-06-12 16:18:21浏览：1453
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Impact of coal gangue on the level of main trace elements in the shallow groundwater of a mine recla
Coal gangue is the most used filling material during reclamation of areas suffering subsidence from mining.Main trace element levels (F,As,Hg,and Pb) in shallow groundwater in the reclamation area may be affected by leaching from the gangue.This can has an impact on the application of the water for agricultural irrigation or use as drinking water.Therefore,it is of great significance to understand the effect coal gangue has on the shallow groundwater of a reclaimed area.We studied the effect of coal gangue on fluorine,arsenic,mercury,and lead levels in the shallow groundwater of a reclamation area by testing the water and the coal gangue.One well near the reclamation area was used as a control well and element levels in water from this well and from the soil next to the well were also measured.The results show that the levels of these elements are increasing in the reclamation area over time.The increase in fluorine,arsenic,mercury,and lead in monitor wells varies from 7.42％ to 8.26％,from 7.13％ to 7.90％,from 4.85％ to 6.48％,and from 4.69％ to 6.42％,respectively.Fluorine and arsenic levels are lower in monitor wells than in the control water.The other elements are found in greater concentration than in the control.The Nemerow index also indicates that the shallow groundwater in the reclamation area Ⅰ is moderately affected by the back-filling coal gangue,while the shallow groundwater in the reclamation area Ⅱ and Ⅲ are slightly affected by the back-filling coal gangue.This shallow groundwater could be used for agricultural irrigation or for drinking....
2020-06-12 16:18:20浏览：1422
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Possibility of Reducing Formations of NOx and SO2 Simultaneously during Coal Combustion
Comparing with other NOx and SO2 control technologies, in-bed reducing NOx and SO2 simultaneously during coal combustion may lower the investment and operation cost. However, there are several possible contradictions between the reduction of NOx and the capture of SO2 during combustion: 1) CO rich atmosphere is favorable for the reduction of NOx, whereas O2 rich favorable for the capture of SO2; 2) higher preheating temperature of coal is favorable for reducing NOx, but unfavorable for reducing SO2; 3) sulphation of some minerals may deactivate their catalytic effect on the reduction of NOx. The attempts to eliminate such contradictions by coating coal granules with thin layer of monometallic oxides and mixed oxides were proposed. Ni2O3 and Fe2O3 showed high activity on NOx reduction and CaO and Cr2O3 showed good effect on sulfur capture. The mixed metallic oxides, e.g., Fe2O3NiO, etc., showed effective for both NOx reduction and SO2 retention. It is possible to in-bed reduce NOx and SO2 simultaneously if the adhering materials are properly chosen to be difunctional materials of both active catalysts for NOx reduction reactions and better sorbents for SO2 retention....
2020-06-12 16:18:19浏览：1427
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GC/MS Analysis of Fractional Extraction of Fusain from Tongting Bituminous Coal in CS2
Fusain from Tongting (Huaibei, Anhui Province) bituminous (FTTB) coal was fractionally extracted using Soxhlet extractor with CS2. Then the extracts were analyzed with GC/MS. Comparison of experimental data between FTTB coal and clarain from Tongting bituminous (CTTB) coal was carried out. The results show that the kinds of small molecule components detected by GC/MS of FTTB are less than those of CTTB. Long-chain alkanes exist mostly in the extracts of fusain. Macromolecular networks are predominant in the FTTB coal mainly composed of inertinite in the coal petrography. The size of micropores in the FTTB coal is relatively small, and the development of micropores is relatively low. Thus the content of aromatic compounds with affinity for micropores is relative low in FTTB, while the content of long-chain alkanes with affinity for macromolecule networks is relatively high. Sub-components in exinite determine the distribution of long-chain alkanes extracted in the last stage. Odd-numbered carbon distribution appears when resin is most in exinite, while high carbon alkane distribution appears when exinite is dominant in cutinite. Small aromatic molecules are firstly packed in micropores, and exist in a free state after micropores are saturated....
2020-06-12 16:18:17浏览：1428
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Paste-like self-flowing transportation backfilling technology based on coal gangue
A paste-like self-flowing pipeline transportation backfilling technology with coal gangue as aggregate is proposed to remove the potential damage caused by coal gangue piles. As well, the difficult problems of recovering high quality safety coal pillars and deep mining of the Suncun Coal Mine (SCM), Xinwen Coal Group, Shandong are resolved. The physical-chemical properties of coal gangue, optimized proportion of materials, backfilling system and craft in the SCM were studied in the laboratory and then an industrial test was carried out on high quality coal pillars under a town. The results show that finely crushed kaolinized and fresh gangue with granularity less than 5 mm can be used as aggregate with fly ash to replace part of the cement and a compos-ite water reducer as an additive, accounting for 1.0%-1.5% of the total amount of cement and fly ash. The recommended proportion is I(cement):4(fly ash): 15(coal gangue), with a mass fraction of 72%-75%, theological paste-like properties and a strength of more than 0.7 MPa at 7 d. The sequence of adding cement, fly ash, water reducer and then coal gangue ensures that the suspended state of the slurry, reducing the wear and jam of pipelines. The working face is advancing continuously by the alternating craft of building block walls with coal gangue and backfilling mined-out gobs with paste-like slurry. The recovery rate is as high as 90% with a backfilling cost of 36.9 Yuan/t, good utilization of coal gangue and no subsidence on the surface. This technology provides a good theoretical basis and application experience for coal mines, cement backfilling with paste-like slurry....
2020-06-12 16:18:13浏览：1413
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A method for detecting miners based on helmets detection in underground coal mine videos
In order to monitor dangerous areas in coal mines automatically,we propose to detect helmets from underground coal mine videos for detecting miners.This method can overcome the impact of similarity between the targets and their background.We constructed standard images of helmets,extracted four directional features,modeled the distribution of these features using a Gaussian function and separated local images of frames into helmet and non-helmet classes.Out experimental results show that this method can detect helmets effectively.The detection rate was 83.7％....
2020-06-12 16:18:11浏览：1455
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Determining areas in an inclined coal seam floor prone to water-inrush by micro-seismic monitoring
The failure depth of the coal seam floor is one important consideration that must be kept in mind when mining is carried out above a confined aquifer. Determining the floor failure depth is the essential precondition for predicting the water-resisting ability of the floor. We have used a high-precision microseismic monitoring technique to overcome the limited amount of data available from field measurements. The failure depth of a coal seam floor, especially an inclined coal seam floor, may be more accurately estimated by monitoring the continuous, dynamic failure of the floor. The monitoring results indicate the failure depth of the coal seam floor near the workface conveyance roadway (the lower crossheading) is deeper and that the failure range is wider here compared to the coal seam floor near the return airway (the upper crossheading). The results of micro-seismic monitoring show that the dangerous area for water-inrush from the coal seam floor may be identified. This provides an important field measurement that helps ensure safe and highly efficient mining of the inclined coal seam above the confined aquifer at the Taoyuan Coal Mine....
2020-06-12 16:18:09浏览：1422
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New Progress in High-Precision and High-Resolution Seismic Exploration Technique in Coal Industry of
In the past twenty years, the proportion of coal in primary-energy consumption in China is generally between 71.3% and 76.5%. The output of coal was 1.374 billion tons in 1996, and 1.21 tons in 1998, which ranked first in the world. Now coal is mined mainly with mechanization in China, which is planned to reach 80% in major State-owned coal mines in 2000 according to the planning of the government (Li et al., 1998; Tang Dejin, 1998).Compared with the USA and Australia, China has more complex coal geological structures. Based on high-resolution seismic technique in coal exploration, a new seismic technique with high-precision and high-resolution (2-D and 3-D) has been developed for the purpose of detecting small geological structures in coal mine construction and production to meet the needs of large-scale popularization of mechanized coal mining in China. The technique is low in cost and requires a relatively short period of exploration, with high precision and wide-range applications. In the middle of the 1980s, it began to be used in pre-mining coal exploration on a trial basis, and entered the peak of exploration in the 1990s, which has made significant progress in providing high-precision geological results for the construction and production of coal industry in China, and is still in the ascendant.This paper discusses some new progress and the exploration capability and application range of the technique....
2020-06-12 16:18:05浏览：1438
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New taxa of angiosperms from coal-bearing continental deposits in Amur area
Considered the question about stratigraphic position of coal-beating continental deposits of the Amur area, the main attention is paid to the definition of pollen of angiosperms. Khlonova (1960), Zaklinskaya (1963), Bratseva (1969) and other scientists reported a lot about the significance of the pollen. Among the new taxa the special interest represents the first description of Engelhardtia pollen of late Maestrichtian and Paleocene deposits. A new kind of pollen Vacuopollis triplicatus sp. nov. is described....
2020-06-12 16:18:03浏览：1426
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Influence of the Haizhou Open Pit Coal Mine on the atmospheric flow over Fuxin,China
The influence of the Haizhou Open Pit Mine on the atmospheric flow in nearby Fuxin City in China was analyzed with the aid of the steady-state Navier-Stokes equations. The finite element method was used to obtain numerical solutions to these equations. The results showed that the Haizhou Open Pit Coal Mine contributes to the turbulent flow in the Fuxin City and its surroundings. However, when compared with the climatic effects, the open pit mine has a relatively small impact on the atmospheric flow over Fuxin....
2020-06-12 16:18:02浏览：1409
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Damage and deterioration mechanism and curing technique of concrete structure in main coal cleaning
Concrete structures in main coal cleaning plants have been rebuilt and reinforced in the coal mines of the Shanghai Da-tun Energy Sources Co. Ltd., the first colliery of the Pingdingshan Coal Co. Ltd. and the Sanhejian mine of the Xuzhou Mining Group Co. Ltd. In these projects, the operating environment and reliability of concrete structures in the main plants of the three companies were investigated and the safety of the structures inspected. Qualitative and quantitative analyses were made on the spe-cial natural, technological and mechanical environments around the structures. On the basis of these analyses, we discuss the long-term, combined actions of the harsh natural (corrosive gases, liquids and solids) and mechanical environments on concrete structures and further investigated the damage and deteriorating mechanisms and curing techniques of concrete structures in the main coal cleaning plants. Our study can provide a theoretical basis for ensuring the reliability of concrete structures in main coal cleaning plants....
2020-06-12 16:18:00浏览：1420
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Study on Supporting of Seam Roadways in Deeply Inclined Coal Seams
Based on the present problems of the support method of gateways in complex surrounding rock in steeply inclined seams, this paper discusses the support selection of lasting gateways in steeply inclined seams, and evaluates the support effects. It draws the conclusion that the support of bolt-mesh-anchor is the most effective support of this sort of gateways by using scale model simulation in lab and practice application. The support effects of practice application are satisfactory. It will give a beneficial reference to other analogical mine and has an extensive application prospect....
2020-06-12 16:17:59浏览：1425
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Analysis of Nox Emission Characteristics of Pulverized Coal Combustion in Different Atmosphere
Researches on the Nox emission characteristics of HT (Huangtai coal),LC(Laicheng) coal are carried out in different atmosphere. The results show that the Nox emission time is postponed in O2/N2 atmosphere mixed with CO. The releasing times of volatile nitrogen and char nitrogen approach, the amount of Nox reduces. In high O2 concentration atmosphere mixed with CO2, the nitrogen re-leasing times come ahead of time, Nox congregate in the beginning of the combustion. On the contrary, nitrogen releases separately, and the amount of Nox reduces greatly....
2020-06-12 16:17:57浏览：1407
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Cleaning of South African coal using a compound dry cleaning apparatus
The compound dry cleaning principle is briefly described. A beneficiation test on South African coal was conducted using a model compound dry cleaning apparatus. Excellent results were obtained and the optimum operating parameters were determined. They are: an amplitude of 3.0 ram, a motor frequency of 47.5 Hz, an air volume of 50%, a transverse angle of 7°, and a longitudinal angle of -2°. These conditions yield a clean coal containing 11% ash and a coal production of 75%. The organic efficiency, η, is 95.86%. These results show that the South African coal can be separated effectively by compound dry cleaning, which will popularize the compound dry cleaning method....
2020-06-12 16:17:56浏览：1415
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