scholarly journals A Method for the Measurement of Carbon Dioxide Desorption from Coal in the Elevated Pressure Range

1996 ◽  
Vol 13 (2) ◽  
pp. 71-84 ◽  
Author(s):  
Adam Nodzeński
Keyword(s):  
Carbon Dioxide ◽  
Heat Exchange ◽  
Pressure Range ◽  
Elevated Pressure ◽  
Gas Pressure ◽  
Coal Bed ◽  
Empirical Equations ◽  
Grain Sizes ◽  
Gas Desorption ◽  
Endothermic Process

During the liberation of gas from a coal bed, the temperature of the system is decreased because desorption is an endothermic process and heat exchange with the surroundings is difficult. A method for measuring gas desorption in the elevated pressure range, enabling investigations under isothermal and quasi-adiabatic conditions, was described. The results of carbon dioxide desorption from Polish coal were presented. The study was carried out using different rates of decrease in the external gas pressure for different coal grain sizes. The non-isothermal desorption curves thus obtained were described using empirical equations. Extrapolation of the equation constants obtained enabled the desorption curves to be calculated for the limit of decrease in rate of the external gas pressure and of grain size. It was found experimentally that the dependence of the decrease in coal temperature on the amount of desorbed gas is linear provided that heat exchange with the surroundings is limited.

scholarly journals Desorption characterization of methane and carbon dioxide in coal and its influence on outburst prediction

2018 ◽  
Vol 36 (7-8) ◽  
pp. 1484-1495 ◽  
Author(s):  
Yunpei Liang ◽  
Fakai Wang ◽  
Yongjiang Luo ◽  
Qianting Hu
Keyword(s):  
Carbon Dioxide ◽  
High Frequency ◽  
Gas Pressure ◽  
Initial Time ◽  
Desorption Process ◽  
Gas Desorption ◽  
Desorption Time ◽  
Short Period ◽  
Experimental Apparatus

Coal and gas outburst is a dynamic phenomenon with violent eruptions of coal and gas from the working coal seam. It has been proved that the rapid desorption within a short period is necessary for the occurrence of an outburst. Due to limitation of the present test condition, gas desorption characterization for the first 60 s has not been researched sufficiently. In the present study, an experimental apparatus with the ability of high-frequency data collection was developed. Initial desorption characterization of methane and carbon dioxide in coal was experimentally studied. Both the initial desorption characterization of methane and carbon dioxide were experimentally studied with different equilibrium pressures. The desorbed gas pressure was measured at desorption time phase of 0–10 and 45–60 s, besides the initial amount of desorbed gas and initial diffusion velocity of coal gas were calculated to assess their risk of outburst. The results show that the gas pressure for both methane and carbon dioxide increases sharply in the initial time and then levels off, and the total amount of desorbed gas increases with the increasing desorption time. Although the amount of desorption methane is slightly larger than that of carbon dioxide at the beginning, the total amount of desorbed carbon dioxide is significantly larger than that of methane at the desorption process. Therefore, it can be concluded that the coal and carbon dioxide outburst is more dangerous than the coal and methane outburst based on the obtained experimental results.

Pressure Assisted Sintering of an Aluminium Alloy

2009 ◽  
Vol 618-619 ◽  
pp. 627-630
Author(s):  
Stephen J. Bonner ◽  
Graham B. Schaffer ◽  
Ji Yong Yao
Keyword(s):  
Aluminium Alloy ◽  
Gas Flow ◽  
Isothermal Holding ◽  
Horizontal Tube ◽  
Elevated Pressure ◽  
Nitrogen Pressure ◽  
Gas Pressure ◽  
Densification Rate ◽  
Conventional Press ◽  
Gas Pressures

An aluminium alloy was sintered using a conventional press and sinter process, at various gas pressures, to observe the effect of sintering gas pressure on the densification rate. Compacts of aluminium alloy 2712 (Al-3.8Cu-1Mg-0.7Si-0.1Sn) were prepared from elemental powders and sintered in a horizontal tube furnace under nitrogen or argon at 590°C for up to 60 minutes, and air cooled. The gas flow was adjusted to achieve specific gas pressures in the furnace. It has been found that increasing the nitrogen pressure at the start of the isothermal holding stage to 160kPa increased the densification rate compared to standard atmospheric pressure sintering. Increasing the nitrogen pressure further, up to 600kPa, had no additional benefit. The densification rate was increased significantly by increasing the gas pressure to 600kPa during both heating and isothermal holding. Under argon the elevated pressure did not increase the densification rate. Results seem to suggest that the beneficial effect of the elevated pressure on the rate of densification is related to nitride formation.

Adsorption isotherms and kinetics of carbon dioxide on Chinese dry coal over a wide pressure range

Adsorption ◽  
2015 ◽  
Vol 21 (1-2) ◽  
pp. 53-65 ◽  
Author(s):  
Yongchen Song ◽  
Wanli Xing ◽  
Yi Zhang ◽  
Weiwei Jian ◽  
Zhaoyan Liu ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Adsorption Isotherms ◽  
Pressure Range ◽  
Adsorption Isotherms And Kinetics ◽  
Wide Pressure Range ◽  
Kinetics Of ◽  
Wide Pressure

Gas Heat Conduction in Evacuated Flat-Plate Solar Collectors: Analysis and Reduction

1995 ◽  
Vol 117 (3) ◽  
pp. 229-235 ◽  
Author(s):  
T. Beikircher ◽  
N. Benz ◽  
W. Spirkl
Keyword(s):  
Heat Conduction ◽  
Flat Plate ◽  
Pressure Range ◽  
Gas Pressure ◽  
Loss Reduction ◽  
Stationary Heat ◽  
Conduction Loss ◽  
Flat Plate Solar Collector ◽  
Gas Conduction ◽  
Kinetic Gas Theory

In stationary heat-loss experiments, the thermal losses by gas conduction of an evacuated flat-plate solar collector (EFPC) were experimentally determined for different values of interior gas pressure. The experiments were carried out with air and argon in the pressure range from 10−3 to 104 Pa. For air, loss reduction sets in at 100 Pa, whereas at 0.1 Pa heat conduction is almost completely suppressed. Using argon as filling gas, gas conduction is reduced by 30 percent (compared to air) at moderate interior pressures of 1000 Pa. With decreasing pressure this reduction is even greater (50 percent reduction at 10 Pa). A theory was developed to calculate thermal losses by gas conduction in an EFPC: Fourier’s stationary heat conduction equation was solved numerically (method of finite differences) for the special geometry of the collector. From kinetic gas theory a formula for the pressure dependency of the thermal conductivity was derived covering the entire pressure range. The theory has been validated experimentally for the gases air and argon. Calculations for krypton and xenon show a possible gas conduction loss reduction of 60–70 percent and 75–85 percent (with respect to air, depending on gas pressure), corresponding to a reduction of the overall collector losses of up to 40 percent.

Understanding Carbon Dioxide Transfer in Direct Methanol Fuel Cells Using a Pore-Scale Model

2021 ◽  
Vol 19 (1) ◽  
Author(s):  
Nathaniel Metzger ◽  
Archana Sekar ◽  
Jun Li ◽  
Xianglin Li
Keyword(s):  
Carbon Dioxide ◽  
Pressure Drop ◽  
Gas Flow ◽  
Direct Methanol Fuel Cells ◽  
Gas Pressure ◽  
Mass Transfer Resistance ◽  
Transfer Resistance ◽  
Cell Components ◽  
Direct Methanol ◽  
Methanol Fuel Cells

Abstract The gas flow of carbon dioxide from the catalyst layer (CL) through the microporous layer (MPL) and gas diffusion layer (GDL) has great impacts on the water and fuel management in direct methanol fuel cells (DMFCs). This work has developed a liquid–vapor two-phase model considering the counter flow of carbon dioxide gas, methanol, and water liquid solution in porous electrodes of DMFC. The model simulation includes the capillary pressure as well as the pressure drop due to flow resistance through the fuel cell components. The pressure drop of carbon dioxide flow is found to be about two to three orders of magnitude higher than the pressure drop of the liquid flow. The big difference between liquid and gas pressure drops can be explained by two reasons: volume flowrate of gas is three orders of magnitude higher than that of liquid; only a small fraction of pores (<5%) in hydrophilic fuel cell components are available for gas flow. Model results indicate that the gas pressure and the mass transfer resistance of liquid and gas are more sensitive to the pore size distribution than the thickness of porous components. To buildup high gas pressure and high mass transfer resistance of liquid, the MPL and CL should avoid micro-cracks during manufacture. Distributions of pore size and wettability of the GDL and MPL have been designed to reduce the methanol crossover and improve fuel efficiency. The model results provide design guidance to obtain superior DMFC performance using highly concentrated methanol solutions or even pure methanol.

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