scholarly journals Methane Desorption Characteristics of Coal at Different Water Injection Pressures Based on Pore Size Distribution Law

Energies ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 2345 ◽  
Author(s):  
Dong Zhao ◽  
Tao Gao ◽  
Yulin Ma ◽  
Zengchao Feng
Keyword(s):  
Pore Size ◽  
Water Pressure ◽  
Water Injection ◽  
Volume Distribution ◽  
Residual Water ◽  
Distribution Law ◽  
Flow Process ◽  
Gas Desorption ◽  
Methane Desorption ◽  
Injection Pressures

Methane desorption characteristics of coal under definite water pressure comprises a complex two-phase flow process. A series of mercury intrusion porosimetry (MIP) and desorption experiments at different water injection pressures are reported in this study. Three lumpy coal samples were used in desorption experiments at three different water injection pressures and at natural desorption for comparison. Samples comprising two ranks of coal were used for MIP measurements including the distribution of porosity and pore sizes. The results of this study enable the establishment of a new model that encompasses a critical theoretical pore size that is most effective for water injection into coalbeds and that can be related to water injection pressure, the length of residual water, and gas adsorption capacity. Data show that the use of different water injection pressures leads to different gas desorption capacities as well as variable time effects and degree of gas desorption. Critical pore size is therefore proposed as a new parameter that can be employed to describe high pressure water effects in the context of gas desorption and can be calculated using pore size and the volume distribution law, as well as via the moisture ratio that remains after experiments and the permanent desorption percentage.

scholarly journals Experimental Study on Methane Desorption from Lumpy Coal under the Action of Hydraulic and Thermal

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Dong Zhao ◽  
Dayuan Li ◽  
Yulin Ma ◽  
Zengchao Feng ◽  
Yangsheng Zhao
Keyword(s):  
Gas Flow ◽  
Water Pressure ◽  
Water Injection ◽  
Steam Injection ◽  
Gas Desorption ◽  
Pressure Water ◽  
Methane Desorption ◽  
Cbm Production ◽  
Injection Technology ◽  
Desorption Capacity

Moisture and thermal are the key factors for influencing methane desorption during CBM exploitation. Using high-pressure water injection technology into coalbed, new fractures and pathways are formed to transport methane. A phenomenon of water-inhibiting gas flow existed. This study is focused on various water pressures impacted on gas-adsorbed coal samples, and then the desorption capacity could be revealed under different conditions. And the results are shown that methane desorption capacity was decreased with the increase in water pressure at room temperature and the downtrend would be steady until water pressure was large enough. Heating could promote gas desorption capacity effectively, with the increasing of water injection pressures, and the promotion of thermal on desorption became more obvious. These results are expected to provide a clearer understanding of theoretical efficiency of heat water or steam injection into coalbed, and they can provide some theoretical and experimental guidance on CBM production and methane control.

scholarly journals Experimental Study on Methane Desorption from Lumpy Coal under the Action of Hydraulic and Thermal

2018 ◽  
Author(s):  
Dong Zhao ◽  
Dayuan Li ◽  
Yulin Ma ◽  
Zengchao Feng ◽  
Yangsheng Zhao
Keyword(s):  
Gas Flow ◽  
Water Pressure ◽  
Water Injection ◽  
Steam Injection ◽  
Gas Desorption ◽  
Pressure Water ◽  
Methane Desorption ◽  
Cbm Production ◽  
Injection Technology ◽  
Desorption Capacity

Moisture and thermal are the key factors for influencing methane desorption during CBM exploitation. Using high pressure water injection technology into coalbed, new fractures and pathways are formed to methane transport. It is existed a phenomenon of water inhibiting gas flow. This study is focused on various water pressures impacted on gas adsorbed coal samples, then the desorption capacity could be revealed under different conditions. And the results are shown that methane desorption capacity was decreased with water pressure increased at room temperature and the downtrend would be steady until water pressure was large enough. Heating could promote gas desorption capacity effectively, with the increasing of water injection pressures, the promotion of thermal on desorption became more obvious. These results are expected to provide a clearer understanding of theoretical efficiency of heat water or steam injection into coalbed, they can provide some theoretical and experimental guidance on CBM production and methane control.

scholarly journals Experimental Study on Methane Desorption with the Coupling Effects of High Pressure Water and Thermal

2017 ◽  
Author(s):  
Dong Zhao ◽  
Dayuan Li ◽  
Yulin Ma ◽  
Zengchao Feng ◽  
Yangsheng Zhao
Keyword(s):  
High Pressure ◽  
Gas Flow ◽  
Water Pressure ◽  
Water Injection ◽  
Key Factors ◽  
Gas Desorption ◽  
Pressure Water ◽  
Methane Desorption ◽  
Injection Technology ◽  
Desorption Capacity

Moisture and thermal are the key factors for influencing methane desorption during CBM exploitation. Using high pressure water injection technology into coalbed, new fractures and pathways are formed to methane transport. It is existed a phenomenon of water inhibiting gas flow. This study is focused on various water pressures impacted on gas adsorbed coal samples, then the desorption capacity could be revealed under different conditions. And the results are shown that methane desorption capacity was decreased with water pressure increased at room temperature and the downtrend would be steady until water pressure was large enough. Heating could promote gas desorption capacity effectively, with the increasing of water injection pressures, the promotion of thermal on desorption became more obvious. There are the others effects on methane desorption capacity influenced by water injection and thermal.

Simulation Analysis for Reinforced Concrete Aqueduct of Lijia Pumping Station

2014 ◽  
Vol 488-489 ◽  
pp. 605-608
Author(s):  
Xiang Zan Xie
Keyword(s):  
Reinforced Concrete ◽  
Simulation Analysis ◽  
Water Pressure ◽  
Water Diversion ◽  
Distribution Law ◽  
Masonry Arch ◽  
Pumping Station ◽  
Earthquake Effect ◽  
Concrete Masonry ◽  
Cushion Layer

Reinforced concrete masonry arch aqueduct is a common water diversion engineering structure. Aqueduct is decorated on the concrete cushion layer, cushion layer effects on masonry arch, the structures stress is uniform, carrying capacity is strong. This paper adopts finite element method to carry out force analysis for reinforced concrete masonry arch aqueduct of Lijia pumping station, considering aqueduct weight, water pressure and earthquake effect, etc. Researching stress and deformation distribution law of reinforced concrete masonry arch aqueduct.

scholarly journals An assessment of sub-standard water pressure in South African potable distribution systems

2017 ◽  
Vol 7 (4) ◽  
pp. 557-567 ◽  
Author(s):  
Louis Strijdom ◽  
Vanessa Speight ◽  
Heinz Erasmus Jacobs
Keyword(s):  
South African ◽  
Distribution Systems ◽  
High Pressures ◽  
Water Pressure ◽  
Residual Pressure ◽  
Residual Water ◽  
Flow Conditions ◽  
Minimum Requirement ◽  
Hydraulic Models ◽  
Standard Pressure

Abstract Sub-standard residual water pressures in urban water distribution systems (WDS) are a prevalent phenomenon in developing countries – South Africa being no exception. The phenomenon of sub-standard pressure is poorly understood, with intermittent supply ultimately resulting when there is no residual pressure left in the system. This research addressed the prevalence and extent of sub-standard pressures by using hydraulic models of potable WDS for 71 South African towns, located in 17 different South African municipalities geographically spread over the country. The hydraulic models included 539,388 modelled nodes, which were analysed to determine the number of nodes with sub-standard pressure heads during peak hour flow conditions. The results show that the residual pressure head was <24 m at 16.5% of the model nodes under peak hour flow conditions, with 6.7% of the nodes having pressure heads <12 m. In contrast, the results also report relatively high pressures in certain parts of the systems, far in excess of the minimum requirement, underlining the need for better pressure management at both high and low ranges. It was also noted that the South African design criterion is relatively stringent compared with some other countries and could potentially be relaxed in future.

Numerical Simulation for the Optimization of the Angle of the Velocity of the Hydrogen in the High Performance Hydrogen Bell-Type Annealers

2012 ◽  
Vol 535-537 ◽  
pp. 1542-1546
Author(s):  
Shun Li Fang ◽  
Shi Ping Jin ◽  
Yong Xiang Zhang ◽  
Su Yi Huang ◽  
Wu Qi Wen
Keyword(s):  
Numerical Simulation ◽  
Heat Exchange ◽  
High Performance ◽  
Simulation Method ◽  
Volume Distribution ◽  
Distribution Law ◽  
Axial Angle ◽  
Numerical Simulation Method ◽  
Design And Application

The flow of the hydrogen has played an important role in the heat exchange in the inner bell. In this research, we have studied the volume distribution of the hydrogen in the inner bell through numerical simulation method, and we get the volume distribution law of the hydrogen when we change the axial angle and the tangential angle of the velocity of the hydrogen flowing into the inner bell while we do not change the speed of the hydrogen. This research could provide theory reference for the design and application of the structure of the coil base of the high performance hydrogen bell-type annealers later.

scholarly journals Examining the effect of pore size distribution and shape on flow through unsaturated peat using computed tomography

2009 ◽  
Vol 13 (10) ◽  
pp. 1993-2002 ◽  
Author(s):  
F. Rezanezhad ◽  
W. L. Quinton ◽  
J. S. Price ◽  
D. Elrick ◽  
T. R. Elliot ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Hydraulic Conductivity ◽  
Pore Structure ◽  
Pore Size ◽  
Soil Water ◽  
Water Pressure ◽  
Peat Soil ◽  
Pressure Head ◽  
Peat Soils ◽  
Unsaturated Hydraulic Conductivity

Abstract. The hydraulic conductivity of unsaturated peat soil is controlled by the air-filled porosity, pore size and geometric distribution as well as other physical properties of peat materials. This study investigates how the size and shape of pores affects the flow of water through peat soils. In this study we used X-ray Computed Tomography (CT), at 45 μm resolution under 5 specific soil-water pressure head levels to provide 3-D, high-resolution images that were used to detect the inner pore structure of peat samples under a changing water regime. Pore structure and configuration were found to be irregular, which affected the rate of water transmission through peat soils. The 3-D analysis suggested that pore distribution is dominated by a single large pore-space. At low pressure head, this single large air-filled pore imparted a more effective flowpath compared to smaller pores. Smaller pores were disconnected and the flowpath was more tortuous than in the single large air-filled pore, and their contribution to flow was negligible when the single large pore was active. We quantify the pore structure of peat soil that affects the hydraulic conductivity in the unsaturated condition, and demonstrate the validity of our estimation of peat unsaturated hydraulic conductivity by making a comparison with a standard permeameter-based method. Estimates of unsaturated hydraulic conductivities were made for the purpose of testing the sensitivity of pore shape and geometry parameters on the hydraulic properties of peats and how to evaluate the structure of the peat and its affects on parameterization. We also studied the ability to quantify these factors for different soil moisture contents in order to define how the factors controlling the shape coefficient vary with changes in soil water pressure head. The relation between measured and estimated unsaturated hydraulic conductivity at various heads shows that rapid initial drainage, that changes the air-filled pore properties, creates a sharp decline in hydraulic conductivity. This is because the large pores readily lose water, the peat rapidly becomes less conductive and the flow path among pores, more tortuous.

On the characterization of pore size distribution of building materials

2017 ◽  
Vol 41 (3) ◽  
pp. 247-263 ◽  
Author(s):  
LF Dutra ◽  
N Mendes ◽  
PC Philippi
Keyword(s):  
Relative Humidity ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Building Materials ◽  
Mercury Porosimetry ◽  
Energy Performance ◽  
Volume Distribution ◽  
Wide Range

Moisture affects significantly the energy performance of air conditioning systems, the durability of materials, and the health of occupants. One way of reducing those effects, without increasing the energy costs, is by means of using porous material ability of absorbing and releasing moisture from/to the adjacent environment, which attenuates the indoor relative humidity variation. This natural ability is intrinsically related to the porous microstructure. Therefore, the characterization of the pore space is an important research theme in the building physics area. This article aims to present a method for obtaining the pore size distribution based on adsorption isotherms and mercury porosimetry data. First, the theoretical formulation based on the Gibbs free energy for a two-phase (liquid–vapor) system, using the De Boer and Zwikker model, is presented, allowing the calculation of the critical adsorbed thickness for pore filling, critical radius, adsorbed moisture content, capillary condensation content, available surface for adsorption, and the distribution of micropores for a wide range of radius. The adsorption isotherm curve is estimated for high relative humidity values through mercury porosimetry, along with the adsorption curve obtained from the experiment. The pore volume distribution calculated by this method can be used to estimate transport coefficients for liquid and vapor phases.

scholarly journals Coal Temperature Variation Mechanism during Gas Desorption Process

2018 ◽  
Vol 2018 ◽  
pp. 1-7
Author(s):  
T. Yang ◽  
B. S. Nie ◽  
Q. S. Ye ◽  
P. Chen
Keyword(s):  
Temperature Change ◽  
Gas Diffusion ◽  
Measured Temperature ◽  
Desorption Process ◽  
Temperature Changes ◽  
Coal Gas ◽  
Coal Temperature ◽  
Gas Desorption ◽  
Heat Adsorption ◽  
Methane Desorption

To further reveal the mechanism of coal gas migration, the reasons for coal temperature changes during the methane desorption process were analyzed from the aspect of molecular motion and the thermodynamic theory. The temperature change mechanism was investigated, and the mathematical equation was established to describe the variation of temperature change during the methane desorption and diffusion process. The established equation was applied for the calculation of temperature change for two types of coal samples, and the measured and theoretical values of temperature changes were obtained. The results show that the temperature changes in the coal gas desorption process are mainly caused by the heat adsorption. The heat adsorption phenomenon was also caused by free gas expansion during the pressure relief process. The gas diffusion and work done for gas seepage also need heat adsorption. The temperature change is positively correlated to the coal gas pressure, quantity, and limit value of gas desorption volume. Due to the poor insulation in the test system, the difference between the theoretical and the measured temperature change values increase with the adsorption equilibrium pressure. It is helpful to further reveal the mechanism of coal and gas outburst. It also has an important reference value for controlling gas dynamic disasters in coal mines.

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