复杂漏风条件下煤体反复氧化与温升特性实验研究

为研究复杂漏风条件下煤矿井下密闭区内煤氧化温升特性,利用大煤堆自然发火实验台,开展了持续漏风(风量0.6 m^3/h)、微漏风(风量0.6 m^3/h→0)及间断漏风(风量0.4,1.2,0.4 m^3/h)条件下煤氧化过程与温度变化特性的研究。实验结果得到了持续漏风条件下风流的散热及供氧能力对煤自燃温升的影响特性,表明密闭区的"呼吸"漏风现象是引发煤氧化温升突变的原因,尤其是密闭区内注氮灭火后,煤体氧化温度的变化对"呼吸"漏风非常敏感。从理论上分析了复杂漏风环境下高温点的形成条件和演化规律。通过实验,获得了密闭区煤氧化高温点形成的判断依据,为密闭区煤自燃防治技术提供了理论依据。

七号平峒+1405 m西翼工作面采空区自燃“三带”分布规律研究

煤矿火灾事故多由于采空区遗煤自燃引起,而“三带”之中的氧化带是自燃现象发生频率最高的区域。为掌握综采放顶煤工作面采空区自燃“三带”分布规律,以四棵树煤炭有限责任公司七号平硐+1405 m西翼工作面为研究对象,通过现场实测工作面遗煤自燃因素,研究分析了A5煤层采空区自燃“三带”分布规律,并进行总结分析,合理确定了该工作面进风侧、回风侧采空区自燃“三带”的范围。

煤矿井下CO气体区域综合治理实践研究

为防止采空区漏风导致煤体氧化自燃产生火灾或其他灾害的发生,通过现场检测与地面化验得到王台铺煤矿15#煤二盘区采空区CO气体参数变化情况,结合采空区煤体自燃理论,现场实施了均压调风、堵漏、注氮气等防治煤体进一步氧化措施,最终使CO、O2气体浓度降到临界值以下,阻止了次生灾害的发生。

厚煤层综放工作面采空区自燃“三带”分布及安全推进速度研究

煤矿中的火灾事故多发生于采空区自燃“三带”之中的氧化升温带,为掌握园丰煤矿1401综采放顶煤工作面采空区自燃“三带”分布规律,以通过考察获得的采空区浮煤自燃极限参数进行总结分析,合理确定了该工作面进风侧、回风侧采空区自燃“三带”的范围及工作面最小安全推进速度。

Kerosene-alumina nanofluid flow and heat transfer for cooling application

Kerosene-alumina nanofluid flow and heat transfer in the presence of magnetic field are studied. The basic partial differential equations are reduced to ordinary differential equations which are solved semi analytically using differential transformation method. Velocity and temperature profiles as well as the skin friction coefficient and the Nusselt number are determined analytically. The influence of pertinent parameters such as magnetic parameter, nanofluid volume fraction, viscosity parameter and Eckert number on the flow and heat transfer characteristics is discussed. Results indicate that skin friction coefficient decreases with increase of magnetic parameter, nanofluid volume fraction and viscosity parameter. Nusselt number increases with increase of magnetic parameter and nanofluid volume fraction while it decreases with increase of Eckert number and viscosity parameter.

An Axial Dispersion Model for Evaporating Bubble Column Reactor

Evaporating bubble column reactor (EBCR) is a kind of aerated reactor in which the reaction heat is removed by the evaporation of volatile reaction mixture. In this paper, a mathematical model that accounts for the gas-liquid exothermic reaction and axial dispersions of both gas and liquid phase is employed to study the performance of EBCR for the process of p-xylene(PX) oxidation. The computational results show that there are remarkable concentration and temperature gradients in EBCR for high ratio of height to diameter (H/DT). The temperature is lower at the bottom of column and higher at the top, due to rapid evaporation induced by the feed gas near the bottom. The concentration profiles in the gas phase are more nonuniform than those (except PX) in the liquid phase, which causes more solvent burning consumption at high H/DT ratio. For p-xylene oxidation, theo ptimal H/DT is around 5.

Experiment study of optimization on prediction index gases of coal spontaneous combustion

The coal of Anyuan Mine has the characteristic of easy spontaneous combustion. Conventional method is difficult to predict it. Coal samples from this mine were tested in laboratory. The data obtained from laboratory determination were initialized for the value which was defined as "K". The ratio of each index gas and value of "K", and the ratio of combination index gases and value of "K", were analyzed simultaneously. The research results show that for this coal mine, if there is carbon monoxide in the gas sample, the phenomenon of oxidation and temperature rising for coal exists in this mine; if there is C_2H_4 in the gas sample, the temperature of coal perhaps exceeds 130 °C. If the coal temperature is between 35 °C and 130 °C, prediction and forecast for coal spontaneous combustion depend on the value of Φ(CO)/K mainly; if the temperature of coal is between 130 °C and 300 °C, prediction and forecast for coal spontaneous combustion depend on the value of Φ(C_2H_6)/Φ(C_2H_2) and Φ(C_2H_6)/K. The research results provide experimental basis for the prediction of coal spontaneous combustion in Anyuan coal mine, and have better guidance on safe production of this coal mine.

Seepage laws of two kinds of disastrous gas in complete stress-strain process of coal

The similarities and differences in seepage flow evolution laws of CH4 and CO2 during complete stress- strain process of samples were comparatively analyzed. The results show that the seepage flow evolution laws of CH4 and CO2 are extremely similar during the stress-strain process, showing that the character- istic first decreased and then increased. A mathematical model was also established according to the rela- tionship of seepage velocity and axial strain. However, due to the strong adsorption ability of CO2, the coal samples generated a more serious ''Klinkenberg effect'' under the condition of CO2. Owing to this, the CO2 seepage flow resulted into occurrence of ''stagnation'' phenomenon during the late linear elastic stage II. In the strain consolidation stage III, the increment rate of CH4 seepage velocity was significantly greater than that of CO2. In the stress descent stage IV, when the axial load reached the peak pressure of coal, the increment rates of CH4 seepage velocity presented a turning point. But the changing rate of CO2 seepage velocity still remained slow and a turning point was presented at one time after the peak of thestrain pressure, which showed an obvious feature of hysteresis.

Spontaneous coal combustion producing carbon dioxide and water

Gas products from the process of coal oxidization and spontaneous combustion have been studied at different temperatures with FTI spectroscopic tests. With temperatures rising to about 30~100 ℃, water and carbon dioxide gas were formed and from about 105~150 ℃, carbon monoxide was produced. Using the DFT B3LYP method with a 6-311G basis set, the reaction system, where spontaneous combustion between coal and oxygen occurs and produces water and monoxide, has been studied, with the geometric configuration for all stagnation points on the potential reaction energy surface optimized. With a frequency analysis and an IRC method, transient formations were tested. Our results indicate that in the reaction of coal oxidization and spontaneous com-bustion producing carbon dioxide and water, oxygen molecules attack carbon atoms of the terminal of the propyl alcohol group on the lateral chain of benzene rings, which causes this propyl alcohol group to produce the acid (-CH2-CH2-COOH) group and water. This acid group continues its break up into carbon dioxide and the (-CH2-CH3) ethyl group. We have come to the conclusion that this water-and-carbon dioxide-production reaction is spontaneous, based on the observation of the energy released by the reaction.

△P index with different gas compositions for instantaneous outburst prediction in coal mines

In this study we measured the △P(initial speed of gas emission) index with different gas concentrations of carbon dioxide(pure CO2,90% CO2+10% CH4,67% CO2+33% CH4,50% CO2+50% CH4,30% CO2+10% CH4 and pure CH4) of coal samples from the No.2 coal seam in the Yaojie Coal Mine,Gansu province,China.The effect of carbon dioxide concentration,gas composition,coal strength and particle size of coal samples on the △P index was investigated.The experimental results show that with gas of various compositions,the △P value of three samples were clearly different.The △P index of coal samples A,B and C(0.2～0.25 mm) were 4,6 and 7 with pure CH4 and 22,30 and 21 when pure CH4 was used.Carbon dioxide concentration affects the △P index markedly.The △P index increases with an increase in carbon dioxide concentration,especially for coal B.Hence,the △P index and K(another outburst index) values tested only with pure CH4 for prediction of the danger of outburst is not accurate.It is important to determine the initial speed of gas emission given the gas composition of the coal seam to be tested for exact outburst prediction.

System Validation Tests for an SOFC Power System at INER

This research presents the results of system validation tests for an SOFC power system. In the study, the system was heated up without electric device, i.e., the fuel providing the required thermal energy through an integrated BOP （balance of plant）. The ex-situ experiments, without an SOFC stack installed in the system, were fast conducted to investigate the operability of a BOP apparatus. It was found that the BOP possessed high conversion rates for both steam reforming and water gas shift reactions. The total fuel concentration of hydrogen and carbon monoxide from the reformer was around 91.2%. The system validation tests showed that, with the natural gas as fuel, the output power from the stack reached to 1,060 W, while the fuel utilization efficiency and electrical efficiency were 67.16% and 45.0%, respectively. A steady 600-hour system operation test was carried out at an average system temperature of 694℃. Of which, a 36-cell stack was employed for the test. Meanwhile, the current, voltage and output power were 26 A, 32.3 V and 840 W, respectively, and its electrical efficiency was around 33.4%.

Model for Reduction of Iron Oxide Pellet with a C-O-H-N Gas Mixture Considering Water Gas Shift Equilibrium in the Gas While It Diffuses through the Product Layer

In metallurgical processes, more and more usage of hydrocarbons is encouraged to bring down the carbon emissions. In this regard, numerous investigations on reduction of oxides by C-O-H-N gas mixture have been reported. Attempts to simulate these reduction processes using shrinking core model, one of the common models used for such studies, have under predicted the reduction rates. This may be owing to the fact that the homogeneous reaction in the gas phase is not being considered. If the reaction temperatures are above 1,000 K, generally so for many reduction processes, the homogeneous gas reaction rates are expected to be high enough that local equilibrium in the gas phase can be assumed. In the present study, reduction of wustite in a C-O-H-N gas mixture has been modeled using shrinking core model considering the water gas shift equilibrium in the gas while it diffuses through the product layer.