Effect of Temperature on the Molecular Weight Distribution in the Different Ranks of Coal during the On-Line Investigation of Coal Pyrolysis Gas Using Direct Photoionization Mass Spectroscopy

Coal pyrolysis gas from different ranks of coal was monitored on real time basis using photoionization mass spectroscopy. The molecular weight distribution of different products as a function of temperature from various coal ranks studied was observed. It was noted that the release of different classes of compounds like phenols, alkenes, alkylated aromatics and aromatic skeletons was temperature dependent. For all the coal ranks at lower temperatures phenols were the main component, with alkenes and alkylated aromatics at slight higher temperatures and aromatic skeletons were released at the highest temperatures studied.

Experimental study on the infrared precursor characteristics of gas-bearing coal failure under loading

The stress and gas pressure in deep coal seams are very high,and instability and failure rapidly and intensely occur.It is important to study the infrared precursor characteristics of gas-bearing coal instability and failure.In this paper,a self-developed stress-gas coupling failure infrared experimental system was used to analyse the infrared radiation temperature(IRT)and infrared thermal image precursor characteristics of gas-free coal and gas-bearing coal.The changes in the areas of the infrared temperature anomalous precursor regions and the effect of the gas on the infrared precursors were examined.The results show that high-temperature anomalous precursors arise mainly when the gas-free coal fails under loading,whereas the gas-bearing coal has high-temperature and low-temperature anomalous precursors.The area of the high-temperature anomalous precursor is approximately 30%–40%under gasbearing coal unstable failure,which is lower than the 60%–70%of the gas-free coal.The area of the low-temperature abnormal precursor is approximately 3%–6%,which is higher than the 1%–2%of the gas-free coal.With increasing gas pressure,the area of the high-temperature anomalous precursor gradually decreases,and the area of the low-temperature anomalous precursor gradually increases.The highand low-temperature anomalous precursors of gas-bearing coal are mainly caused by gas desorption,volume expansion,and thermal friction.The presence of gas inhibits the increase in IRT on the coal surface and increases the difficulty of infrared radiation(IR)monitoring and early warning for gas-bearing coal.

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.

Experimental study on the variation law of coal temperature during excavation in coal mines

By testing the temperature of the coal and the stress of the working surface, we got the variation law of coal temperature and coal stress during the excavation. The result shows that the activities of mining affect the coal temperature, the fluctuation of coal temperature and the coal stress is synchronous. During the smooth change of crustal stress, the coal temperature basically keeps unchanged, when the dynamic phenomenon appears, the coal temperature changes, as well the coal stress. Therefore, we can use the online coal temperature monitoring system to test the coal temperature of the working surface continuously, and it can provide basic information for forecasting coal mine power disaster before it happens.

Calculation of gas content in coal seam influenced by in-situ stress grads and ground temperature

On the basis of the analysis of coal bed gas pressure in deep mine, and the coal bed permeability ( k ) and the characteristic of adsorption parameter ( b ) changing with temperature, the author puts forward a new calculating method of gas content in coal seam influenced by in situ stress grads and ground temperature. At the same time, the contrast of the measuring results of coal bed gas pressure with the computing results of coal bed gas pressure and gas content in coal seam in theory indicate that the computing method can well reflect the authenticity of gas content in coal seam,and will further perfect the computing method of gas content in coal seam in theory,and have important value in theory on analyzing gas content in coal seam and forecasting distribution law of gas content in coal seam in deep mine.

Experiment of gas diffusion and its diffusion mechanism in coal

In coal,the gas mainly exists in a free or an adsorption state.When the coal containing gas is damaged,gas desorption and diffusion will occur which can result in gas disaster.This research on gas desorption and diffusion provides a theoretical basis for gas disaster mechanism and prevention.The influence of pressure and temperature on gas diffusion is studied by the experiment.And the mechanism of pressure and temperature on gas diffusion is also analysed.The research results indicate that gas diffusion capacity increases with increasing temperature under the same pressure for the same coal sample.This is mainly because the temperature increases,gas molecular hot motion is severer,kinetic energy of gas molecular increases,and gas desorption quickens,therefore gas diffusion capacity changes stronger.Under other unchanged conditions,the greater gas adsorption balance pressure,the more gas adsorption content,and the higher the initial gas concentration.When gas diffusion begins,the greater the gas concentration gradient,the faster the gas diffusion speeds.

Gas seepage equation of deep mined coal seams and its application

In order to obtain a gas seepage law of deep mined coal seams, according to the properties of coalbed methane seepage in in-situ stress and geothermal temperature fields, the gas seepage equation of deep mined coal seams with the Klinkenberg effect was obtained by confirming the coatbed methane permeability in in-situ stress and geothermal temperature fields. Aimed at the condition in which the coal seams have or do not have an outcrop and outlet on the ground, the application of the gas seepage equation of deep mined coal seams in in-situ stress and geothermal temperature fields on the gas pressure calculation of deep mined coal seams was investigated. The comparison between calculated and measured results indicates that the calculation method of gas pressure, based on the gas seepage equation of deep mined coal seams in in-situ stress and geothermal temperature fields can accu- rately be identical with the measured values and theoretically perfect the calculation method of gas pressure of deep mined coal seams.

Preventing Coal and Gas Outburst Using Methane Hydration

According to the characteristics of the methane hydrate condensing and accumulating methane, authors put forward a new technique thought way to prevent the accident of coal and gas outburst by urging the methane in the coal seams to form hydrate. The paper analyzes the feasibility of forming the methane hydrate in the coal seam from the several sides, such as, temperature,pressure, and gas components, and the primary trial results indicate the problems should be settled before the industrialization appliance realized.

Research and Development of Hot Primary Air Heater for Coal-Fired Boilers in Power Plant

The reasons of introducing cold air into pulverizer are analyzed for boilers with large capacity 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 signif icantly, 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.

Natural gas releasing simulation experiment of coal in process of temperature decreasing and decompression and preliminary application in Ordos Basin

Natural gas releasing simulation experiments were carried out in laboratory for researching the gas storage capacity in state of high temperature and high pressure and its gas releasing potential in process of temperature decreasing and decompression. The exiting phase state was studied through measuring gas adsorption of coal and PVT phase calculating of natural gas. Gas volume, gas molecular and isotope compositions in process of temperature decreasing and decompression were measured, natural-gas yields released from the Upper Paleozoic coal strata after later Cretaceous (K3) were calculated and the formation of the reservoir was studied combining with the geological background. The results indicate that natural gas stored in coal has still bigger releasing potential after the uplift of Upper Paleozoic strata. There exists a weak gas supply-effluent equilibrium in the reservoir of Ordos Basin, which is another possible evidence that the Upper Paleozoic gas reservoir may be a deep basin gas reservoir.

Computer Analysis of a Methane Fired Crucible Furnace

Two design factors and one operation parameter of a methane fired crucible furnace are numerically explored in this work. These are the number of burners, the location of the exhaust gas exit, and the air-fuel ratio, respectively. Three dimensional steady state Computational Fluid Dynamics simulations are carried out in order to analyze the influence of the above factors on the mean cavity temperature in absence of thermal load, the methane content and the oxygen content of the exit gas.

灰色预测法在磨煤机出口温度预测中的应用

状态趋势预测是状态监测与故障诊断中的一个重要环节.探讨了灰色预测模型GM(1,1)在磨煤机出口温度预测中的应用.实例证明预测结果是可信的.

PKM炉运行工况异常分析

介绍了PKM炉生产过程中炉内各层的作用及其原理,分析了工况恶化的原因、危害及预防措施。

一种参数自适应模糊PI控制器在超临界磨煤机出口温度控制系统的应用研究

针对磨煤机出口温度难于控制的缺点,提出一种参数自适应模糊比例-积分(proportional-integral,PI)控制策略,该控制策略利用控制过程中的实时趋势结合模糊控制规则库,可以对自适应模糊PI控制器输出部分的比例因子进行在线调整。当入口温度发生变化时,动态地控制冷风门挡板的开度,使系统输出与给定温度相等,改善了磨煤机出口温度控制系统的动态特性。通过超临界机组投运试验数据及相关变化曲线,证明此优化控制策略具有抗干扰能力强、适应变工况能力强以及跟随能力强的优点,比常规控制策略具有较强的适应性和鲁棒性。

煤粉炉排烟温度高的原因分析及运行中可采取的措施

对燃煤锅炉排烟温度高的主要原因进行了分析 ,并根椐洛河电厂 # 3、4炉降低排烟温度的经验 。

磨煤机出口温度偏低对制粉系统的影响

磨煤机是发电厂重要的辅机设备,沙角C电厂燃用印尼A煤时,发现磨煤机内出现煤粉结块的现象,影响了机组的正常出力。文章分析认为磨煤机出口温度设置偏低是引起煤粉结块的主要原因,并通过煤质分析与计算,在保证制粉系统安全的前提下,适当提高磨煤机出口温度以解决煤粉结块的问题,运行表明取得了较好的效果。

降低排烟温度的措施

排烟热损失是发电厂锅炉各项损失中最大的一项。文章分析了影响邹县电厂排烟温度高的主要因素,即炉膛、水平烟道积灰,制粉系统运行方式的变化,一、二次风配比及制粉用热风量等,根据这些因素采取了相应的改进措施(如将次声波吹灰器改为蒸汽吹灰器,防止锅炉结焦,合理运用制粉系统再循环风门的作用,合理安排制粉系统运行方式、保持合适的过量空气系数等)后,取得了较好的效果,如排烟温度约下降5℃,排烟损失约减少0.5%。

六级预分解系统煤粉配比计算研究

以六级预热顸分解系统为模板，通过物料和热量平衡计算，分析了增加入炉燃料量对系统参数的影响。结果表明，随着分解炉喂煤比例的逐渐增大。各级预热器和分解炉出口的气体温度及八窑物料温度逐渐升高。炉中煤粉燃烧率和碳酸盐分解率随炉煤比例的增大而提高，炉煤比例超过73％后，碳酸盐分解基本完成。随炉煤比例的增大，熟料产量大幅提高，热耗有所下降。但考虑到系统的稳定性，炉煤比例控制在71％～73％较为合理。

隔声罩法在降低钢球磨煤机噪声中的应用

分析钢球磨煤机噪声来源及影响因素,依据合理有效的隔声原理,介绍了隔声罩在内江发电总厂钢球磨煤机噪声治理中的应用情况。

国阳新能第三热电厂3号锅炉燃烧特性试验研究

针对目前山西省大多数电厂存在着灰渣含碳量高、排烟温度高的问题,尤其对燃用无烟煤种的锅炉问题显得更加突出。为此,于2004年12月完成了国阳新能第三热电厂3号锅炉燃烧特性试验研究,试验结果表明,在适当调整运行方式下,对降低灰渣含碳量,降低排烟温度和低负荷稳燃方面均取得了良好的效果,从而为解决其他电厂类似问题上奠定了良好的基础。