Injection Flow Research Articles

Professor Manuel Miró, a researcher with an extensive and prestigious academic career, kindly spoke to BrJAC

Manuel Miró received his M.Sc. (1998) and Ph.D. (2002) in Chemistry from the University of the Balearic Islands, Spain. He has conducted post-doctoral research in several universities, including the Technical University of Berlin, Technical University of Denmark and University of Natural Resources and Applied Life Sciences. He is currently Full Professor in Analytical Chemistry at the University of the Balearic Islands (since September 2017); Guest Professor at Charles University (Czech Republic) (since 2014); and member of the IUPAC Chemistry and Environment Division (Subcommittee on Chemical and Biophysical Processes in the Environment). He has completed and consolidated four teaching periods (each of 5 years) and three research periods (each of 6 years). Dr. Miró is the Reviews Editor of the journal Analytica Chimica Acta (Elsevier, IF: 6.91, the second highest IF across scientific journals for general analytical chemistry) and Associate Editor of the Encyclopedia of Analytical Science, 3rd Edition, Elsevier, positions that he has held since 2007 and 2016, respectively. His publication record shows over 220 refereed publications, including 14 book chapters and a foreword, with an h-index of 42 and over 5600 citations. He has published 24 articles in the prestigious journal ‘Analytical Chemistry’ from the American Chemical Society and is the corresponding author of 110 articles. Dr. Miró has delivered 70 oral presentations (60 as plenary, keynote, or invited lecturer) at international conferences on analytical chemistry, sample preparation, nanotechnology, environmental chemistry, and automation based on flow methodology. He has also presented over 180 poster communications in international conferences and symposiums. He has supervised 10 Ph.D. students in national and international universities (Technical University of Denmark, Mahidol University and Chiang Mai University in Thailand, University of the Balearic Islands in Spain, and Federal University of Bahia in Brazil). He has been actively engaged in 34 national and international research projects (e.g., University of Melbourne in Australia and Charles University in Czech Republic), including 16 as the Principal Investigator. Dr. Miró’s research interests are focused on the development of on-line sample processing strategies for isolation and/or preconcentration of trace levels of environmental pollutants, exploiting 3D printing in the generation of various flow injections, including 3D-printed µFIA and Lab-on-a-Valve mesofluidic platforms, in conjunction with modern analytical instrumentation.

Cadmium and copper transport in alluvial soils in the Brazilian semiarid region: column percolation and modeling

ABSTRACT Regarding the Brazilian textile industry, part of the northeast region stands out as the second-largest textile manufacturing hub in the country. Despite its importance, this industrial activity has been bringing relevant environmental concerns regarding the disposal of textile effluents, especially from industrial laundries. This waste contains many chemicals and among them are various types of heavy metals. To assess environmental risks associated with heavy metals, pollutant transfer needs to be investigated. This study evaluated the retention and mobility of heavy metals Cd and Cu in alluvial soil, through soil column tests. The up-flow column percolation tests were performed using a nonreactive tracer (KBr) at a concentration of 0.3 mol L -1 and injecting a metallic solution containing Cu and Cd at 100 and 60 mg L -1 , respectively. The injection flow rate was 0.75 mL min -1 . The hydro-dispersive parameters were obtained by modeling the observed breakthrough curves with the convection-dispersion equation (CDE) and the two-region model, also referred to as the MIM (Mobile-IMmobile waters) model. The transport parameters were obtained from the two-site model (TSS). All elution curves were fitted to the models with the CXTFIT 2.0 program. The Two-Site Sorption Model was the best for the case studied, with R 2 of 0.985 and 0.995 for Cu and Cd, respectively. The values of R were considerably higher than the unit, presenting an average of 2.138 for Cu and 1.907 for Cd. This indicates a delay of these contaminants when leaving the column, which is caused by the interaction of these chemical compounds with the soil. The values obtained for parameter D were 3.469 for Cu and 5.205 for Cd. Thus, the metals in this study present a risk of groundwater contamination for the local alluvial aquifers. The main reason for that is the physicochemical features of the soil, such as high sand content (85 %) and low OM content (2.1 %). The results also indicated greater retention and less mobility for Cu than for Cd, pointing to a greater risk for Cd.

BCH modelling studies on biocementation process in mitigating leaks from a CO2 sequestrated aquifer

BCH modelling studies on biocementation process in mitigating leaks from a CO2 sequestrated aquifer

Optimal parameter adjustment of catalytic combustion heaters for oil shale in-situ conversion of low calorific value gases

Oil shale resources are huge, and in order to develop and utilize them rationally, it is crucial to research heaters suitable for downhole in-situ conversion mining. Compared with the problems of short life and multi-stage energy utilization of downhole electric heaters, combustion heaters have advantages such as high thermal efficiency and low cost. The heater uses low calorific value industrial waste gas as the fuel for gas injection, which reduces carbon emissions and environmental pollution and saves gas injection costs. In this paper, we propose to apply catalytic combustion of low calorific value industrial waste gas to generate high temperature exhaust gas suitable for mining, and establish the relationship between gas injection flow rate, combustion chamber parameters and gas injection duration by mathematical methods. The effect of the downhole high-pressure environment on the catalytic combustion characteristics of low calorific gas was simulated and the formula for calculating the content of low calorific gas in the exhaust gas was modified. The results show that the determination of the relational equation solves the problem of excessive axial volume in the design process of downhole heaters. Under high pressure conditions downhole, the exhaust gas temperature and low calorific gas conversion rate are significantly improved. The catalyst ignition temperature ranged from 973 K to 1073 K. Increasing the downhole pressure to 5 MPa increased the conversion of low calorific value gas from 74.56% to 88.22%. The gas injection rate and calorific value range can be calculated by correcting the equation for the content of low calorific gas in the exhaust gas. The conclusion of the study provides a reference basis for the selection of catalytic combustion process parameters for low calorific industrial waste gas, and also provides an important theoretical basis for the construction of the downhole test prototype.

Application of Remote Wireless Intelligent Layered Water Injection Technology in Dagang Oilfield

A remote wireless intelligent layered water injection technolo-gy is proposed to address the problems of traditional layered water in-jection well testing in oil fields, such as the inability to achieve continu-ous dynamic monitoring of injection parameters, high failure rate, and low success rate of testing and commissioning. The technology consists of a host computer client, a server, a surface controller, and an under-ground intelligent water distributor. The underground intelligent water distributor takes the injected water as the carrier, and uses the fluctua-tion of the water injection pressure in the tubing for signal transmission to realize two-way communication between the ground controller and the downhole intelligent water distributor. The underground intelligent water distributor integrates high-precision pressure gauges, controllable water nozzles, and calculation and control modules to form an intelli-gent control system, realizing the reception of ground down transmitted commands or data, the calculation and control of water injection flow rate of water nozzles, and the storage and upload of underground data. Remote wireless intelligent layered water injection technology has been applied in 43 wells, with a success rate of 100%. The maximum depth is 3897m, and the maximum wellbore inclination is 56.07°. This tech-nology realizes remote control of water injection wells, intelligent au-tomatic measurement and adjustment, real-time data monitoring, and automatic early warning functions, laying a foundation for the con-struction of “Digital Intelligence” oilfield.

Dynamic modelling and engineering simulation of fluid mechanics in water injectors

To study the fluid dynamic response mechanism under the working condition of water injection well borehole, based on the microelement analysis of fluid mechanics and the classical theory of hydrodynamics, a fluid microelement pressure-flow rate relationship model is built to derive and solve the dynamic distribution of fluid pressure and flow rate in the space of well borehole. Combined with the production data of a typical deviated well in China, numerical simulations and analyses are carried out to analyze the dynamic distribution of wellbore pressure at different injection pressures and injection volumes, the delayed and attenuated characteristics of fluid transmission in tube, and the dynamic distribution of wellbore pressure amplitude under the fluctuation of wellhead pressure. The pressure loss along the wellbore has nothing to do with the absolute pressure, and the design of the coding and decoding scheme for wave code communication doesn't need to consider the absolute pressure during injecting. When the injection pressure is constant, the higher the injection flow rate at the wellhead, the larger the pressure loss along the wellbore. The fluid wave signal delay amplitude mainly depends on the length of the wellbore. The smaller the tubing diameter, the larger the fluid wave signal attenuation amplitude. The higher the target wave code amplitude (differential pressure identification root mean square) generated at the same well depth, the greater the wellhead pressure wave amplitude required to overcome the wellbore pressure loss.

Transient Injection of Flow: How Torn and Bent Slabs Induce Unusual Mantle Circulation Patterns Near a Flat Slab

AbstractTorn and bent slabs are usually associated with flat‐slab subduction where the descending plate develops a horizontal geometry beneath the overlying continent. How such slab dynamics modify the surrounding mantle flow and the overriding plate remains enigmatic. Here, we conduct three‐dimensional subduction numerical experiments to investigate the flat slab to steep‐angle slab transition region and examine the impact of slab geometry changes on mantle flows. The results show that the along‐strike change due to flattening a segment of slab induces oblique flow toward the mantle corner at the transition region where flat slab bends to steep‐subducting slab. Slab tears can occur due to the buoyancy contrast between an oceanic ridge and the surrounding dense oceanic crust and/or presence of weak zones. A vertical tear at the side edge of a flat slab causes toroidal flow around the steep‐angle slab where sub‐slab mantle floods rapidly through the tear. Flow through the tear spreads to all directions including upwelling toward the continental base that may trigger slab and partial melting and thus affect arc magmatism. A horizontal tear that occurs ahead of the flat portion where slab resumes its steep‐angle results in enhanced plate‐motion parallel flow. Notably, the tear‐induced flow behaves as a rapid injection through the slab breach with the peak velocity up to an order of magnitude higher than plate motion, lasting for 1–2 million years after initially tearing. This rapid pulse flow might be recorded in surface tectonics as distinct transient events of topography or metamorphism.

Influence of Horizontal Multi-Bedding on Hydraulic Fracture Propagation in Shale Reservoirs

Artificial fractures can easily occur and propagate in shale reservoir bedding. Their height restricts the volume of fracturing modification. A physical simulation of true triaxial hydraulic fracturing was used to analyze the characteristics of fracture morphology and the fracturing curve, as well as explore the influence of horizontal multi-bedding on the hydraulic fracture propagation of shale reservoirs. The results showed that a weaker bedding strength increased bedding fracture activation and reduced the fracture height. A higher bedding density increased the fracture complexity and reduced the main fracture height. A high injection flow can easily cause morphologically complex multi-bedding fractures. A higher injected fracturing-fluid viscosity increased the layer-penetration ability of the main hydraulic fracture when it expanded and reduced the opening degree of the bedding plane. This study provides technical support for the hydraulic fracturing design of shale reservoirs.

Optimization of combustion organization scheme for pre-combustion chamber of pre-cooled engine

Pre-cooled engines, in which the incoming air is cooled by a pre-cooler before it enters the subsequent components for operation, are one of the important developments in combined power solutions. Therefore, how to optimize the gas temperature uniformity of the high temperature gas stream at the outlet of the pre-combustion chamber to achieve higher efficiency of the pre-cooled engine will be the main research content. In this paper, grid partitioning was performed on the pre combustion chamber model, and the k-omega model and EDC model were used to simulate the internal flow field of the pre combustion chamber. And verify the correctness of the simulation through engine hot testing. Explored the changing trends of the internal velocity and temperature fields of the engine under different secondary injection structures. The larger the secondary injection flow rate, the more obvious the obstruction to high-temperature gas, and the better the uniformity of gas temperature. However, in experiments, the secondary injection components often cannot withstand a large flow rate ratio. Ultimately, the gas temperature uniformity is best when the secondary injection flow rate ratio is 65%. Circumferential deflection will cause the gas to spin, and the spinning process will make the gas temperature at the same radius more uniform. However, due to the decrease in radial velocity, the obstruction effect on the overall high-temperature gas is weakened. When the gas is deflected towards the head by 30°, the velocity of the incoming gas and the velocity of the secondary injection gas are combined and perpendicular to the axis. At this time, the gas temperature uniformity is the best.

Fracture propagation laws of staged hydraulic fracture in fractured geothermal reservoir based on phase field model

Hydraulic fracturing is widely used in geothermal resource exploitation, and many natural fractures exist in hot dry rock reservoirs due to in-situ stress and faults. However, the influence of natural fractures on hydraulic fracture propagation is not considered in the current study. In this paper, based on the phase field model, a thermo-hydro-mechanical coupled hydraulic fracture propagation model was established to reveal the influence of injection time, fracturing method, injection flow rate, and natural fracture distribution on the fracture propagation mechanism. The results show that fracture complexity increases with an increase in injection time. The stress disturbance causes the fracture initiation pressure of the second cluster significantly higher than that of the first and third clusters. The zipper-type fracturing method can reduce the degree of stress disturbance and increase fracture complexity by 7.2% compared to simultaneous hydraulic fracturing. Both low and high injection flow rate lead to a decrease in fracture propagation time, which is not conducive to an increase in fracture complexity. An increase in the natural fracture angle leads to hydraulic fracture crossing natural fracture, but has a lesser effect on fracture complexity. In this paper, we analyzed the influence of different factors on initiation pressure and fracture complexity, providing valuable guidance for the exploitation of geothermal resources.

Production performance optimization of water-enhanced geothermal system based on effective time-averaged volume

Enhanced geothermal systems (EGS) hold great promise for geothermal energy extraction. However, accurately evaluating reservoirs and fractures remains a primary challenge in optimizing the production performance of EGS. This study addresses this gap by introducing a novel index, the effective time-averaged volume. It assesses the effectiveness of reservoirs and fractures, and system economy, making it a valuable tool for determining effective utilization times. Through establishing a triple-well fractured model, parametric studies are innovatively conducted. Results indicate that a reduced effective time-averaged volume leads to a higher thermal recovery rate and greater power generation. The optimized parameters of the model are a reservoir permeability of 0.5 mD, a primary fracture permeability of 50 D, an injection flow rate of 45 kg/s, an injection temperature of 20 °C, and a well spacing of 200 m. The cumulative power generation and effective time-averaged volume of the reservoir for 45 years are 4.89 × 106 GJ and 4.78 × 108 m3, respectively. Furthermore, we quantify the contributions of influencing factors to production performance, highlighting the significant impact of injection flow rate on system economy. These insights provide valuable guidance for the efficient design, operation, and optimization of EGS.

Effect of resolution enhancement using metal ion assisted strategy based on electrospray ionization-ion mobility spectrometry: A case study of carbendazim and thiabendazole in fruits

A method for the rapid and simultaneous determination of carbendazim and thiabendazole residues by electrospray ionization-ion mobility spectrometry (ESI-IMS) combined with a metal ion-assisted technique was developed and validated in different fruit matrices. The metal ion assisted strategy was performed instead of tedious pre-separation procedures to overcome the limitation of low resolution of IMS. Four transition metal cations, Co(II), Ni(II), Cu(II), and Zn(II), were screened and their interactions with carbendazim and thiabendazole were investigated. The injection flow rate and metal ion concentration were optimized. The Cu(II) assisted approach helped to achieve well-separated peaks with a peak-to-peak resolution of 3.61. This method was then applied to detect carbendazim and thiabendazole simultaneously in apples, pears, bananas, and mangoes. The limit of detection (LOD) were 0.03 mg kg−1 and 0.13 mg kg−1 for carbendazim and thiabendazole, respectively, while spiked recoveries were 61.5–122.0% and 83.5–119.8%, respectively, with RSDs less than 13.9%. These satisfactory evaluation parameters indicated that the approach was capable of performing quantitative analysis of multi-pesticide residues. In addition, the feasibility of using metal ion assisted-ESI-IMS for the simultaneous detection also was theoretically demonstrated through molecular electrostatic potential analysis and binding energy calculation based on density functional theory (DFT). Both experimental and theoretical results revealed the effectiveness of the metal ion assisted strategy in improving the resolution of ESI-IMS.

First clinical evaluation report of using the Topol device to deliver PIPAC treatment

Pressure Intra Peritoneal Aerosol Chemotherapy (PIPAC) is a new approach to deliver a drug into the peritoneal cavity. This novel approach associates an intraperitoneal pressure obtained by the laparoscopic procedure and an aerosol distribution obtained by a specific devoted nebulizer device. A new device is now available to perform PIPAC, called Topol® (Skala). We reported earlier, as a clinical evaluation report, the first consecutive cases treated. Seven patients had gastric, appendix, ovarian and rectal peritoneal metastasis and received 12 PIPAC procedures. The injector flow was selected to be 1.5 ml/s, as proposed by the company. No abnormal hyper pressure was observed in the injector. All the procedures were successful with a pressure between 10 and 20 bars and were performed to completion for drug administration. The intended therapeutic results were obtained in each case. No adverse events were recorded during the post-PIPAC clinical evaluations. To date, two patients succumbed due to peritoneal metastasis progression, 5 are alive, and two patients considered as non-operable had been secondarily proposed for cytoreductive surgery because of tumor response. One patient underwent gastrectomy, cytoreductive surgery and HIPEC. Conclusions regarding safety, performance and conformity are favorable for this first limited clinical evaluation report.

Reactive Transport Modeling of Chemical Stimulation Processes for an Enhanced Geothermal System (EGS)

An enhanced geothermal system is a kind of artificial geothermal system, which can economically exploit geothermal energy from deep thermal rock mass with low permeability by artificially created geothermal reservoirs. Chemical stimulation refers to a reservoir permeability enhancement method that injects a chemical stimulant into the fractured geothermal reservoir to improve the formation permeability by dissolving minerals. In this study, a reactive solute transport model was established based on TOUGHREACT to find out the effect of chemical stimulation on the reconstruction of a granite-hosted enhanced geothermal system reservoir. The results show that chemical stimulation with mud acid as a stimulant can effectively improve the permeability of fractures near the injection well, the effective penetration distance can reach more than 20 m after 5 days. The improvement of porosity and permeability was mainly caused by the dissolution of feldspar and chlorite. The permeability enhancement increased with the injection flow rate and HF concentration in the stimulant, which was weakly affected by the change in injection temperature. The method of chemical enhancement processes can provide a reference for subsequent enhanced geothermal system engineering designs.

High-Frequency Pulsed Coaxial Injectors for High-Speed Flow Mixing and Control

Efficient and controlled mixing of fuel with fast-moving air is a challenging physical problem relevant to hypersonic systems. Although mixing happens at the molecular level through diffusion, the macroscopic phenomenon such as entrainment and vorticity dynamics resulting from the shear layer instabilities of the mixing fluids play a significant role in the overall efficiency of the process. With a focus on improving mixing at extreme flow conditions, this paper presents a fundamental study of a novel, high-speed, pulsed coflow system integrated with ultrahigh-frequency actuators (11–20 kHz). This injection system consists of a supersonic actuation air jet at the inner core that provides large mean and fluctuating velocity profiles in the shear layers of a fluid stream injected surrounding the core through an annular nozzle, with pulsing occurring at a designated frequency. The high-frequency streamwise vortices and shockwaves tailored to the mean flow significantly enhanced supersonic flow mixing between the fluids compared to a steady coaxial configuration operating at the same input pressure. Experiments also indicate a strong connection between the frequency and unsteady amplitude of the actuation jet to the supersonic flow mixing phenomenon. This paper reports the design details of the injector assembly and flow mixing characteristics captured using phase-locked microschlieren and planar laser-induced fluorescence techniques.

Simulation and Optimization of Surface Gas Injection Systems for Underground Gas Storage.

With the rapid development and popularization of sensing technology and information technology, the demand for intelligence in the oil and gas industry and gas storage has increased. The optimized operation of surface engineering is an important part of intelligence. To master the operation law of the surface engineering of gas storage, improve the production management level, and reduce the cost of gas injection, we investigated the simulation and optimization of a surface gas injection system for practical underground gas storage. We propose calculation formulas for gas injection well pressure separately according to the ideal gas equation of state, the van der Waals equation, and the R-K equation and verify them using actual data. By comparing the calculation error of the data and the complexities for both the equation and the calculation process, we finally choose the formula derived from the ideal gas equation of state as the constraint condition for our research. Moreover, we model the surface gas injection system by using the Aspen HYSYS simulation software. From the variation in the compressor power, we determine that the equalizing pressure injection pattern is the optimal injection pattern and the optimal number of injection wells is three. In addition, we examine the relationship between injection flow and well pressure with injection time under the optimal injection pattern. Finally, we obtain the functional formula of well pressure and injection flow with injection time. The results can provide not only a basis for the gas injection decision making of production systems but also a basic guarantee for the digital transformation and intelligent operation of enterprises.

Development and Application of New Multifunctional Foaming Agents to Enhance Production in Oil Wells

Summary Maintaining or increasing production from wells in mature oil reservoirs with high pressure, temperature, brine hardness, and salinity is a significant technological and economic challenge. These wells usually produce with a high gas-oil ratio and large water cuts and often operate with gas lift systems. This work focuses on the development and application of new multifunctional foaming agents (MFAs) to enhance production from oil wells under these conditions. The MFAs were developed based on molecular design and laboratory studies, which demonstrated that they can be used with water cuts exceeding 30% and in the presence of salinity and hardness levels up to 400,000 ppm and 180,000 ppm, respectively. Furthermore, these agents remain stable at temperatures up to 180°C. The production/lift efficiency of the MFAs was evaluated using two novel dynamic laboratory methods that are conducted close to the wellhead and at downhole conditions of temperature and pressure, respectively. The experimental results demonstrate a significant enhancement in the liquid production efficiency, with some cases showing an increase from no production to as much as 44% when the MFAs were used. The laboratory tests were also used to optimize the MFA type and concentration in the design of a field application. The field test was conducted in three oil wells with water cuts ranging from 40% to 90%, depths exceeding 5000 m, bottomhole temperature around 150°C, and brine hardness and salinity up to 180,000 ppm and 310,000 ppm, respectively. This is the first reported field test of MFAs for production enhancement under such challenging conditions. The MFA was coinjected with gas lift via the annulus. The MFA mixed with reservoir fluids in the tubing and generated foam downhole with concentrations ranging from 160 ppm to 750 ppm. The rheological properties of the foam were designed to prevent pressure losses and the formation of stable foam or emulsions at surface facilities. The field tests demonstrated that the MFA was able to increase oil production at a fixed gas lift injection flow rate. Alternatively, it was able to reduce lift gas consumption while maintaining or even increasing the original oil production.

Experimental study of dual-well gas injection and brine discharge in salt cavern sediment space

Docking Well underground salt cavern storage (DWUSCS) is a novel construction method that enables dual-well to be used for gas injection and brine discharge (GIBD), resulting in improved efficiency, cost savings, and greater utilization of the cavity space. However, the uncertainties of insoluble materials and the discharge patterns have retarded the research status in dual-well GIBD studies. In this study, we analyzed the insoluble materials of the DWUSCS layer, and investigated the factors that affect sediment space injection and discharge in the connecting channel through GIBD simulation experiments. We found that the densities of insoluble mineral components were similar to those of rock salt. Our simulation experiments revealed that the greater the permeability of the sediment space, the larger the void fraction, the more micron-sized particles in the insoluble materials, and the more brine that can be discharged during GIBD. During OIOD, gas injection pressure rises rapidly and then stabilizes before gas discharge. When the gas is discharged with brine, the pressure drops dramatically and finally reaches equilibrium. The gas injection flow rate has an impact on the discharge of brine, flow rate with 10 mL/min can displace more brine than 100 mL/min. The angle of the connecting channel also influences the effect of brine discharge in the sediment space during OIOD. Specifically, when the angle of the channel is 0°, the discharge volume is minimum, but it increases with increasing angle, and the optimal angle relates to permeability. In the case of a horizontal connecting channel, TIOD (the discharge outlet is at the bottom of the channel) (TIOD (bottom)) can discharge the maximum amount of brine. For large GIBD device, TIOD (bottom) will expend more than 50 times experimental periods than OIOD. By using OIOD first and then TIOD (bottom), the construction period can be shortened and the economic cost reduced. These findings provide valuable insights into the GIBD process from on-site DWUSCS.

Process optimization for short carbon fiber polyetherimide composite mold

With the high precision requirements and the trend of large-scale composite parts, the development of composite molds is imminent. The short carbon fiber (SCF) composite mold is mainly prepared by the technological process flow of composite sheet injection, the bonding of composite plates, and machining. However, the current process optimization method has not matured adequately, and there are still many shortcomings, for example, low precision and high cost. In this paper, the optimization method of SCF/polyetherimide (PEI) composite molds is proposed. Many experiments have been conducted, and the results show that the coefficient of thermal expansion of composite samples can be effectively reduced and the mechanical properties can be improved by optimizing the SCF weight ratio and carbon fiber length. The bonding strength of composite joints in a high-temperature environment can be improved by optimizing the bonding process parameters and modification by carbon nanotubes. Based on the above optimization method, the SCF/PEI composite mold is prepared, and the C-shaped beam composite part is fabricated by using this mold. Compared with the part made by aluminum mold, the shape accuracy of the C-shaped beam composite part is proven high through digital measurement technology.

Intermittent injection of carbon dioxide to control the risk of coal spontaneous combustion and methane explosion: A case study in U-type ventilation

The compound risk of coal spontaneous combustion (CSC) and methane (CH4) explosion poses a serious threat to mining safety. Green resource utilization of carbon dioxide (CO2) can help achieve carbon neutrality. Therefore, CO2 is seen as a means to prevent compound risk of CSC and CH4 explosion. To address the situation at the 4209 working face, a multi-physical field coupling model was established to simulate the CSC and CH4 explosion in the gob of a U-type ventilation system. The accuracy of the model was verified against measured data from the gob. Following the injection of CO2 into the gob, the volume of the compound risk area was significantly reduced. The effects of intermittent CO2 injection were compared to those of continuous injection, and it was determined that intermittent injection was the preferred method, taking injection cost into account. Three injection frequencies were tested, with F= 1/2 d showing the optimal effect. When the injection frequency was set to F= 1/2 d, and three CO2 injection flow rates were tested, it was demonstrated that a flow rate of 141.3 m3/h provided the most effective risk reduction while meeting the required CO2 concentration in the working face.