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This protocol demonstrates how to prepare a briquette sample and conduct a uniaxial compression experiment with a briquette in different CO2 pressures using a visualized and constant-volume gas-solid coupling test system. It also aims to investigate changes in terms of coal’s physical and mechanical properties induced by CO2 adsorption.
Injecting carbon dioxide (CO2) into a deep coal seam is of great significance for reducing the concentration of greenhouse gases in the atmosphere and increasing the recovery of coalbed methane. A visualized and constant-volume gas-solid coupling system is introduced here to investigate the influence of CO2 sorption on the physical and mechanical properties of coal. Being able to keep a constant volume and monitor the sample using a camera, this system offers the potential to improve instrument accuracy and analyze fracture evolution with a fractal geometry method. This paper provides all steps to perform a uniaxial compression experiment with a briquette sample in different CO2 pressures with the gas-solid coupling test system. A briquette, cold-pressed by raw coal and sodium humate cement, is loaded in high-pressure CO2, and its surface is monitored in real-time using a camera. However, the similarity between the briquette and the raw coal still needs improvement, and a flammable gas such as methane (CH4) cannot be injected for the test. The results show that CO2 sorption leads to peak strength and elastic modulus reduction of the briquette, and the fracture evolution of the briquette in a failure state indicates fractal characteristics. The strength, elastic modulus, and fractal dimension are all correlated with CO2 pressure but not with a linear correlation. The visualized and constant-volume gas-solid coupling test system can serve as a platform for experimental research about rock mechanics considering the multifield coupling effect.
The increasing concentration of CO2 in the atmosphere is a direct factor causing the global warming effect. Due to the strong sorption capacity of coal, CO2 sequestration in a coal seam is regarded as a practical and environment-friendly means to reduce the global emission of greenhouse gas1,2,3. At the same time, the injected CO2 can replace CH4 and result in gas production promotion in coalbed methane recovery (ECBM)4,5,6. The ecological ....
1. Sample preparation
The average mass of the briquette sample was 230 g. Depending on the industrial analysis, the briquette exhibited a moisture content of 4.52% and an ash content of 15.52%. Furthermore, the volatile content was approximately 31.24%. As the sodium humate was extracted from the coal, the components of the briquette were similar to raw coal. The physical characteristics are displayed in Table 2.
The comparison of th.......
Considering the danger of high-pressure gas, some critical steps are important during the test. The valves and O rings should be inspected and replaced regularly, and any source of ignition should not be allowed in the laboratory. When using the manual pressure-regulating valve, the experimenter should twist the valve slowly to make the pressure in the visualized vessel increase gradually. Do not disassemble the vessel during the test. When the experiment is finished, the back door of the vessel should be opened after th.......
This work was supported by the China National Major Scientific Instruments Development Project (Grant No. 51427804) and the Shandong Province National Natural Science Foundation (Grant No. ZR2017MEE023).
....Name | Company | Catalog Number | Comments |
3Y-Leica MPV-SP photometer microphotometric system | Leica,Germany | M090063016 | Used for vitrinite reflectance measurement |
Automatic isotherm adsorption instrument | BeiShiDe Instrument Technology (Beijing)CO.,Ltd. | 3H-2000PH | Isothermal adsorption test |
Electro hydraulic servo universal testing machine | Jinan Shidaishijin testing machine CO.,Ltd | WDW-100EIII | Used to provide axial pressure |
Gas pressure sensor | Beijing Star Sensor Technology CO.,LTD | CYYZ11 | Gas pressure monitoring |
Gas tank(carbon dioxide/helium) | Heifei Henglong Gas.,Ltd | Gas resource | |
high-speed camera | Sony corporation | FDR-AX30 | Image monitoring |
Incubator | Yuyao YuanDong Digital Instrument Factory | XGQ-2000 | Briquette drying |
jaw crusher | Hebi Tianke Instrument CO.,Ltd | EP-2 | Coal grinding |
Manual pressure reducing valve | Shanghai Saergen Instrument CO.,Ltd | R41 | Outlet gas pressure adjustment |
Proximate Analyzer | Changsha Kaiyuan Instrument CO.,Ltd | 5E-MAG6700 | Coal industrial analysis |
Resistance strain gauge | Jinan Sigmar Technology CO.,LTD | ASMB3-16/8 | Poisson ratio measurement |
Sieve shaker (6,16mesh) | Hebi Tianguan Instrument CO.,Ltd | GZS-300 | Coal powder shelter |
Soft pipe | Jinan Quanxing High pressure pipe CO.,Ltd | Inner diameter=5 mm maximal pressure=30 MPa | |
Standard rock sample circumferential deformation test apparatus | Huainan Qingda Machinery CO.,Ltd | Circumferential deformation acquisition | |
Strain controlled direct shear apparatus | Beijing Aerospace Huayu Test Instrument CO.,LTD | ZJ-4A | Tensile strength, cohesion, internal friction angle measurement |
Vaccum pump | Fujiwara,Japan | 750D | Used to vaccumize the vessel |
Valve | Jiangsu Subei Valve Co.,Ltd | S4 NS-MG16-MF1 | Gas seal |
Visual loading vessel | Huainan Qingda Machinery CO.,Ltd | Instrument for sample loading and real-time monitoring |
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