Fracture processes in coal measures strata under liquid CO2 phase transition blasting

Liquid CO2 phase transition blasting is a physical blasting method to enhance permeability through liquid CO2 phase transition expansion. To study the propagation criterion of fractures during blasting, the energy of phase transition blasting is evaluated through the thermodynamic equation by studying the action process of the liquid CO2 blasting, thus obtaining the scope of the smash zone and crack zone as well as the propagation criterion of fractures under the effect of high pressure gas. The gas blasting model for a coal body is established based on the SPH algorithm, thus obtaining the criteria for formation of the smash zone and for generatio and propagation of the crack zone. Moreover, the radius of phase transition blasting is surveyed onsite by the peephole method. It is shown that the explosive energy of the MZL-51/2000 phase transition blasting equipment with a release pressure of 270 MPa is 1510 kJ. The coal body is crushed by the high pressure CO2 percussive drilling, forming the smash zone. Meanwhile, fractures are generated around the smash zone. With the expansion and migratio of the gas, the fracture will further grow into a crack zone. The fracture inside the coal body goes through four states: rapid, slow, rapid, and then slow again. According to field surveys, the blasting radius of the MZL-51/2000 equipment with loaded liquid of 1.8 kg is approximately 3 m.

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Liquid CO2 Phase-Transition Rock Fracturing: A Novel Technology for Safe Rock Excavation

Applied Sciences ◽

10.3390/app12010068 ◽

2021 ◽

Vol 12 (1) ◽

pp. 68

Author(s):

Haoyue Sui ◽

Tianming Su ◽

Ruilin Hu ◽

Ke Yang ◽

Yaxing Cheng

Keyword(s):

Phase Transition ◽

Rock Mass ◽

Processing System ◽

Field Tests ◽

Fractal Dimensions ◽

Dominant Frequency ◽

Rock Breaking ◽

Rock Breakage ◽

Rock Fracturing ◽

Liquid Co2

In order to determine the applicability of liquid CO2 phase-transition fracturing technology in rock mass excavations, the principles of CO2 phase-transition fracturing were analyzed, and field tests of liquid CO2 phase-transition fracturing were performed. An “Unmanned Aerial Vehicle (UAV) camera shooting + Microstructure Image Processing System (MIPS) analyzing” method was used to acquire the rock mass characteristics. Further, the Hilbert–Huang Transform (HHT) energy analysis principle was adopted to analyze the characteristics of fracturing vibration waves. The experimental results showed that during the process of fracturing, there were both dynamic actions of rock breakage due to excitation stress wave impacts, and quasi-static actions of rock breakage caused by gasification expansion wedges. In semi-infinite spaces, rock-breakage zones can mainly be divided into crushing zones, fracture zones, and vibration zones. At the same time, under ideal fracturing effects and large volumes, the fracturing granularity will be in accordance with the fractal laws. For example, the larger the fractal dimensions, the higher the proportion of small fragments, and vice versa. Moreover, the vibration waves of the liquid CO2 phase-transition fracturing have short durations, fast attenuation, and fewer high-frequency components. The dominant frequency band of energy will range between 0 and 20 Hz. The liquid CO2 phase-transition fracturing technology has been observed to overcome the shortcomings of traditional explosive blasting methods and can be applied to a variety of rock types. It is a safe and efficient method for rock-breaking excavations; therefore, the above technology effectively provides a new method for the follow-up of similar engineering practices.

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Effect of Pipe Diameter and Inlet Parameters on Liquid CO2 Flow in Transportation by Pipeline with Large Height Difference

Processes ◽

10.3390/pr7100756 ◽

2019 ◽

Vol 7 (10) ◽

pp. 756 ◽

Cited By ~ 2

Author(s):

Lu ◽

Hu ◽

Qi

Keyword(s):

Phase Transition ◽

Flow Rate ◽

Coal Mine ◽

Inlet Pressure ◽

Pipe Diameter ◽

Fire Prevention ◽

Inlet Temperature ◽

Height Difference ◽

Liquid Co2 ◽

Temperature And Pressure

Fire prevention and extinguishing and CO2 sequestration in coal mine gob require continuous transportation of liquid CO2 in pipelines with large height difference (from ground to underground). However, the temperature and pressure variation of liquid CO2 in pipelines with large height difference is still unclear, which hinders the design of a liquid CO2 pipeline transportation system. The influence of pipe diameter and inlet parameters (temperature and pressure) on the variation of temperature and pressure of liquid CO2 along the 1000 m vertical pipeline was studied in this paper. The study found that for each pipeline diameter considered there existed a range of flowrates where safe flow conditions could be ensured, at which no phase transition occurs throughout the length of the pipeline. When the transporting flow is larger than the maximum limit flow, phase transition occurs dramatically, which will lead to a sudden drop in temperature and pressure. When the transporting flow rate is lower than the minimum limit flow rate, phase transition of CO2 occurs slowly along the pipeline. According to the requirement of underground fire prevention and extinguishing for transporting flow rate and the economic cost of the pipeline system, the optimum diameter is 32 mm, and the corresponding safe transporting flow range is 507–13,826 kg/h. In addition, when the inlet pressure is constant, if the inlet temperature is too high, phase transition of CO2 occurs dramatically at the entrance. For a 1000 m vertical pipe with diameter of 32 mm, when the inlet pressure is 14 bar, 16 bar, 18 bar, 20 bar, 22 bar, 24 bar, the corresponding maximum allowable inlet temperatures are −30 °C, −26 °C, −23 °C, −19 °C, −16 °C and −13 °C, respectively. This research has significant guidance for safety transportation scheme of liquid CO2 from coal mine surface to underground.

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Effects of Flow Velocity on Transient Behaviour of Liquid CO2 Decompression during Pipeline Transportation

Processes ◽

10.3390/pr9020192 ◽

2021 ◽

Vol 9 (2) ◽

pp. 192

Author(s):

Chenghuan Xiao ◽

Zhaijun Lu ◽

Liguo Yan ◽

Jiaqiang Wang ◽

Shujian Yao

Keyword(s):

Phase Transition ◽

Flow Velocity ◽

Large Scale ◽

Equilibrium Phase ◽

Temperature Drop ◽

Pipeline Transportation ◽

Initial Flow ◽

Evaporation Coefficient ◽

Transient Behaviour ◽

Liquid Co2

Investigating the transient behaviour of liquid CO2 decompression is of great importance to ensure the safety of pipeline transportation in carbon capture and storage (CCS) technology. A computational fluid dynamics (CFD) decompression model based on the non-equilibrium phase transition and Span–Wagner equation of state (EoS) was developed to study the effects of actual flowing state within the pipeline on the transient behaviour of liquid CO2 decompression. Then, the CFD model was verified by comparing the simulated results to test data of a large-scale “shock tube” with an inner diameter of 146.36 mm. The results showed that the evaporation coefficient had a significant impact on the transition behaviour of CO2 decompression, while the condensation coefficient made no difference. When the evaporation coefficient was 15 s−1, the CFD-predicted results were in good agreement with the test results. Moreover, the effects of flow velocity on transient behaviour of liquid CO2 decompression were further investigated. It was found that the flow velocity affected the temperature drop of liquid CO2 during decompression, thereby affecting the phase transition of liquid CO2. In addition, the initial flow velocity also showed a significant influence on the transient behaviour of CO2 outside the pipe.

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Research on Liquid CO2 Phase Transition Ejection Technology

E3S Web of Conferences ◽

10.1051/e3sconf/202126102008 ◽

2021 ◽

Vol 261 ◽

pp. 02008

Author(s):

Danna He ◽

Youxing Zuo ◽

Bailiang Shen ◽

Qingsan Shi ◽

Heng Wang

Keyword(s):

Phase Transition ◽

Mathematical Model ◽

Low Temperature ◽

Research Field ◽

Experiment Data ◽

Environmental Friendliness ◽

Internal Ballistics ◽

Liquid Co2 ◽

Simulation Calculation ◽

New Research

Due to the low temperature and clean gas, liquid CO2 phase transition ejection technology has outstanding advantages such as high versatility, low launch cost, and environmental friendliness, which will open up a new research field for the development of missile launch technology. Through the study of phase transition characteristics of liquid CO2 in this paper, a mathematical model of internal ballistics of the liquid CO2 phase transition ejection power system is established. And through simulation calculation, the launching parameters such as the pressure in the launcher, the velocity and acceleration of the missile are obtained, and they is compared with the experiment data to verify the validity of the model.

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