Oxygen Concentration In Gas Research Articles

Prediction of Oxygen Content Using Weighted PCA and Improved LSTM Network in MSWI Process

The accurate and real-time measurement of oxygen content in flue gas is the cornerstone of high incineration efficiency and economic benefits for municipal solid waste incineration (MSWI) plants. However, conventional hardware oxygen analyzers are difficult to obtain the oxygen content in flue gas timely and precisely. In this article, a weighted principal component analysis (WPCA) algorithm combined with improved long short-term memory (ILSTM) network is proposed for oxygen content prediction. First, to reduce the model complexity, a WPCA is developed to calculate mutual information correlation coefficients between principal components and the quality variable. Second, the LSTM network is exploited to establish a prediction model, and its hyperparameters are obtained with the particle swarm optimization (PSO) algorithm to improve the generalization ability of the prediction model. Finally, the effectiveness of the proposed prediction method is validated by a benchmark simulation and the real industrial data. And the comparison results with other methodologies demonstrate the considerable prediction performance of the proposed WPCA-ILSTM model.

Pore structure of sludge char and simultaneously NO removal characteristics in the treated flue gas from Ca-L

A novel system for the comprehensive utilization process of treated flue gas from Calcium based looping (Ca-L) is proposed to realize the municipal sludge char (MSC) production and simultaneously NO removal. In this study, the pore characteristic of MSC was studied by low pressure nitrogen adsorption (LP-N2GA) analysis and fractal mechanism. NO removal characteristics of sludge and the contribution of MSC were also investigated. Besides, the migration of nitrogen functional groups in MSC under different oxygen conditions was studied by X-ray photoelectron spectroscopy (XPS). Results show that the pore structure of MSC was the best when the pyrolysis time was 60 s and pyrolysis temperature was 900 °C. Higher concentrations of oxygen and CO2 are not conducive to the good development of pore structure. At the same time, the simultaneous removal of NO was achieved, and the peak NO reduction rate was 73.12%. P-N content in solid samples disappears after pyrolysis. N-6, and N-5 contents decrease, while N-X content in MSC increases at higher oxygen concentration in the flue gas, proving that the oxygen in the flue gas destroys the reducing atmosphere suitable for removing NO.

Output-Relevant Common Trend Analysis for KPI-Related Nonstationary Process Monitoring With Applications to Thermal Power Plants

Operation safety and efficiency are two main concerns in power plants. It is important to detect the anomalies in power plants, and further judge whether they affect key performance indicators (KPIs), such as the thermal efficiency. These two goals can be achieved by KPI-related nonstationary process monitoring. Although the thermal efficiency cannot be accurately measured online, it can be strongly characterized by some online measurable variables, including the exhaust gas temperature and oxygen content of flue gas. These critical variables closely related to the thermal efficiency are termed as output variables. Inspired from nonstationary common trends between input and output variables in thermal power plants, the output-relevant common trend analysis (OCTA) method is proposed, in this article, to model the input–output relationship. In OCTA, input and output variables are decomposed into nonstationary common trends and stationary residuals, and the model parameters are estimated by solving an optimization problem. It is pointed out that OCTA is a generalized form of partial least squares (PLS). The superior monitoring performance of OCTA is illustrated by case studies on a real power plant in Zhejiang Provincial Energy Group of China. Compared with the other PLS-based recursive algorithms, OCTA can effectively detect the anomalies in power plants and accurately determine whether they have an impact on the thermal efficiency or not.

Gas-phase isopropanol degradation by nonthermal plasma combined with Mn-Cu/-Al2O3.

In this study, the dielectric barrier discharge (DBD) induced by nonthermal plasma (NTP) technology was used for isopropanol (IPA) degradation. IPA, intermediate, final product, and ozone concentrations were analyzed using GC-MS, carbon dioxide detector, and ozone detector. The experimental flow rate and concentration were fixed to 1 L/min and 1200 ppm ± 10%, respectively. Different reaction procedures were proposed for self-made metal catalyst combined with a plasma system (plasma alone and γ-Al2O3 combined with plasma, Cu (5 wt%)/γ-Al2O3 combined with plasma, Mn (3 wt%)-Cu (5 wt%)/γ-Al2O3 combined with plasma). In addition, the effect of the carrier gas oxygen content (0%, 20%, and 100%) on IPA conversion and intermediate and carbon dioxide selectivity was also investigated. The results revealed that the Mn (F)-Cu/γ-Al2O3 combined with plasma exhibited more efficient IPA conversion. In the 100% oxygen environment, the IPA conversion rate increased from 79.32 to 99.99%, and carbon dioxide selectivity increased from 3.82 to 50.23%. IPA was completely converted after 60 min of plasma treatment with the acetone selectivity, carbon dioxide selectivity, and tail ozone concentration of 26.71% ± 1.27%, 50.23% ± 0.56%, and 1761 ± 11 ppm, respectively. This study proved that the current single planar DBD configuration is an effective advanced treatment technology for the decomposition of VOCs.

Electrochemical Sensing Behaviour of Fabricated Au-SnO2 /ITO Electrode

Functional nanomaterials formed after the combination of a metal oxide and metal play a prominent role in the world of nanotechnology [1]. The interaction between them generates the formation of the interfacial bonds that are mainly responsible for the adhesion strength occurring at the interfaces. Such materials find utilization in numerous fields of electronics, solar cells and chemical sensing [2]. Nanoparticle research presents widespread span for the corroboration of pioneering revelations in the field of medicines, cosmetics, optics and electronics. Astonishing outcomes result from altering the molecular and atomic states of the materials which may not be possible by using them in their original states. Tin dioxide (SnO2) has been colossally used as sensing material in optoelectronic devices, and solid-state gas sensors owing to its stupendous electrical properties escorted by elevated chemical stability [3]. However, very few reports of SnO2 nanoparticles regarding biomolecule detection are available [4]. The sensing characteristics of SnO2 can further be improved by chemical doping with appropriate transition metals such as Pt, Pd, Au, Ag, Ru and Rh [5]. The addition of Au offers suitable platform for the detection of specific analytes [6]. Sol gel method was used to synthesize SnO2 and Au-SnO2 nanoparticles. Structural, morphological and chemical composition of the synthesized nanoparticles was confirmed by XRD, FESEM, TEM, FTIR, and EDS spectroscopic techniques. A frenzy of excitement has generated in electrochemistry by the application of nanotechnology. The electrochemical sensing response of the synthesized nanoparticles was checked after depositing them on ITO substrate. The comparison of the electrochemical performance of Au-SnO2/ITO electrode was done with SnO2/ITO and ITO by cyclic voltammetry (CV), differential pulse voltammetry (DPV) cyclic and electrochemical impedance spectroscopy (EIS). All studies were carried out in phosphate buffer (pH 7.0) at room temperature. The synthesized sensor exhibited good storage stability, specificity and reproducibility with RSD 1.73%. The practical application of the fabricated electrode was demonstrated in real sample with excellent recovery. Reference Wisnios, A. Kiejna, J. Korecki, Towards understanding MgO/Fe interface formation: Adsorption of O and Mg atoms on an Fe(001) surface, Phys. Rev. B 96 (2017) 115418.Nalepka, K. Sztwiertnia, P. Nalepka, Preferred orientation relationships at the Cu/α−Al2O3interface: Identification and theoretical explanation, Acta Mater. 104 (2016) 156–165.Tournier, C. Pijolat, Influence of oxygen concentration in the carrier gas on the response of tin dioxide sensor under hydrogen and methane, Sens Actuators B 61(1999) 43-50.Lavanya, S. Radhakrishnan, C. Sekar, Fabrication of hydrogen peroxide biosensor based on Ni doped SnO2 nanoparticles, Biosen. Bioelectron, 36 (2012) 41-47.Cheraghi, M. A. Taher, H. Karimi-Maleh, R. Moradi, Simultaneous detection of nalbuphine and diclofenac as important analgesic drugs in biological and pharmaceutical samples using a Pt: Co nanostructure-based electrochemical sensor, J Electrochem Soc. 164 (2017) B60-B65.Zhang, X. Liu, S.Wu,M. Xu, X. Guo, S. Wang, Au nanoparticle-decorated porous SnO2 hollow spheres: a new model for a chemical sensor J. Mater. Chem. 20(2010) 6453–9.

Investigation of optoelectrical properties of indium oxide thin films with hydrogen and oxygen gas concentration variation during sputtering

We have investigated the optoelectrical properties of the In2O3 thin films deposited with hydrogen and oxygen gas concentration variation during the sputtering process. As-deposited films have shown amorphous nature and post-annealing treatment has led to polycrystalline films with better optoelectrical properties. The hydrogen and oxygen gas concentration optimization has led to the In2O3:H films' with electrical mobility of ~80 cm2/V.s at the carrier concentration of ~1 × 1020 cm−3, and the resistivity of ~5 × 10−4 Ω cm. The better carrier mobility of the In2O3:H films in comparison to the pure In2O3 films is due to minimization of carrier scattering, after replacing some of the doubly ionized oxygen vacancies (in In2O3) with the singly charged hydrogen (in In2O3:H). The spectroscopic ellipsometry (SE) analysis of the In2O3:H films' have revealed the role of oxygen in the free carrier absorption in near-infrared wavelength region; apart from quantification of optical mobility, and plasma energy of the In2O3:H films. The post-annealed In2O3:H films’ carrier mobility obtained from the Hall and SE measurements have pointed out the influential role of carrier impurity scattering rather than the grain boundary scattering.

Effect of argon and oxygen gas concentration on mode transition and negative ion production in helicon discharge

In this paper, the effect of mixing of argon and oxygen gas on the mode transition and negative ion production in the helicon discharge is investigated. In the source chamber of the experimental setup, argon–oxygen gas mixture plasma is produced by applying RF power from 100 W to 2000 W at an applied magnetic field of 0.03 T. In this experiment, the total flow rate is kept at 200 SCCM, corresponding to the working pressure of 4–5 × 10−1 Pa. The mode transition to helicon discharge is investigated by varying the concentration of these two gases. To the best of our knowledge, the literature survey indicates this to be the first study of the influence of the mixing of oxygen–argon gas on the mode transition from the inductive to the helicon mode. It is observed that an increase in the concentration of oxygen gas in the discharge shifts mode transition toward higher RF power values, indicating the influence of the nature of the working gas on the transition to the inductive as well as to the helicon mode. The variation of the electron density and temperature is explained in terms of particle and power balance equation. In the source and in the downstream expansion chamber, the effect of the concentration of argon gas on the negative ion production in oxygen discharge is also studied, and the results are explained in terms of various reactions involved in the production and loss of negative ions.

Membrane system for regulating oxygen and carbon gas concentration indoors

In the present work, a conditioning system was simulated based on membrane gas separation technology. The considered system is suitable for the simultaneous monitoring of the following indoor air parameters: oxygen concentration, carbon dioxide concentration. The membrane air conditioning system consists of two membrane modules, one to remove carbon dioxide from the room and the second to maintain the required oxygen level in the room. The effectiveness of using the membrane method for the removal of carbon dioxide formed in the process of human life is shown. It is shown that the use of membrane technologies as part of air conditioning systems helps to reduce the gas consumption necessary for normal human life.

Should We Wear Masks While Exercising Outdoor During COVID-19?

While safety is a high priority for our community during the Covid-19 pandemic, exercise is essential to improve and maintain a healthy lifestyle (ACSM, 2018). Fitness centers are reopening across the county with various safety precautions including masks and social distancing. Although the Centers for Disease Control and Prevention (CDC, 2020) recommends all people to wear a mask (except for children younger than 2 years old, anyone who has trouble breathing, and anyone who is unconscious, incapacitated, or otherwise unable to remove the cloth face-covering without assistance), wearing a mask may not be possible in every situation. For example, during outdoor exercises, wearing a mask contributes to issues of potential breathing restrictions (lower the oxygen gas concentration levels in the recirculated air). This column concerns views on wearing masks while exercising, especially when doing it outdoors.

Change of inspired oxygen concentration in low flow anesthesia.

BackgroundThere are several advantages of low flow anesthesia including safety, economics, and eco-friendliness. However, oxygen concentration of fresh gas flow and inspired gas are large different in low flow anesthesia. This is a hurdle to access to low flow anesthesia. In this study, we aimed to investigate the change in inhaled oxygen concentration in low flow anesthesia using oxygen and medical air.MethodsA total of 60 patients scheduled for elective surgery with an American Society of Anesthesiologist physical status I or II were enrolled and randomly allocated into two groups. Group H: Fresh gas flow rate (FGF) 4 L/min (FiO₂ 0.5). Group L: FGF 1 L/min (FiO₂ 0.5). FGF was applied 4 L/min in initial phase (10 min) after intubation. After initial phase FGF was adjusted according to groups. FGF continued at the end of surgery. Oxygen and inhalation anesthetic gas concentration were recorded for 180 min at 15 min interval.ResultsThe inspired oxygen concentration decreased by 5.5% during the first 15 min in the group L. Inspired oxygen decreased by 1.5% during next 15 min. Inspired oxygen decreased by 1.4% for 30 to 60 min. The inspired oxygen of group L is 35.4 ± 4.0% in 180 min. The group H had little difference in inspired oxygen concentration over time and decreased by 1.8% for 180 min.ConclusionsThe inspired oxygen concentration is maintained at 30% or more for 180 min in patients under 90 kg. Despite some technical difficulties, low flow anesthesia may be considered.

Investigation on the limiting oxygen concentration of combustible gas at high pressures and temperatures during oil recovery process

High pressure air injection is an important method for oil recovery. In this process, due to exist of combustible gas and oxygen, the wellbore explosion accident may happen. To solve the problem, the optimal method is to control the oxygen concentration in the wellbore. Thus, it needs to investigate the limiting oxygen concentration (LOC) of combustible gas at high pressures and temperatures. In this study, experiments were carried out to investigate the LOC of combustible gas at pressures from 1 MPa to 15 MPa and temperatures from 40 °C to 120 °C. The influence of pressure and temperature on LOC was analyzed. The results showed that the LOC of combustible gas declines a lot as the initial pressure and temperature increases. At 15 MPa and 120 °C, the LOC drops up to 8.21%. It was also found that the LOC is exponentially and linearly dependent on initial pressure and temperature, respectively. Besides, the empirical formulas were proposed to calculate the LOC at different conditions. Based on the present results, the standard for controlling the oxygen concentration in the wellbore was confirmed. As a result, the allowable oxygen concentration in the wellbore at different conditions can be determined. Therefore, the results of this study can help to avoid the wellbore explosion and ensure safety during air injection process.

Influence of Air Infiltration on Combustion Process Changes in a Rotary Tilting Furnace

Air infiltration into the combustion chambers of industrial furnaces is an unwanted phenomenon causing loss of thermal efficiency, fuel consumption increase, and the subsequent increase in operating costs. In this study, a novel design for a rotary tilting furnace door with improved construction features is proposed and tested experimentally in a laboratory-scale furnace, aimed at air infiltration rate reduction by decreasing the gap width between the static furnace door and the rotating body. Temperatures in the combustion chamber and oxygen content in the dry flue gas were measured to document changes in the combustion process with the varying gap width. Volumetric flow values of infiltrating air calculated based on measured data agree well with results of numerical simulations performed in ANSYS and with the reference calculation procedure used in relevant literature. An achievable air infiltration reduction of up to 50% translates into fuel savings of around 1.79 to 12% of total natural gas consumption of the laboratory-scale furnace. The average natural gas consumption increase of around 1.6% due to air infiltration into industrial-scale furnaces can thus likewise be halved, representing fuel savings of almost 0.3 m3 per ton of charge.

A study of diesel and Pongamia Pinnata biodiesel combustion in compression ignition engines using zero-dimensional modelling and experimental methods

ABSTRACT The present study develops a single-zone zero-dimensional progressive combustion simulation model using Python programming language for compression ignition engines. The model is capable of predicting in-cylinder pressure, heat release rate, engine performance, and emissions characteristics. The numerical model is experimentally validated using resuts from engine testing for diesel, Pongamia Pinnata biodiesel and diesel-biodiesel blends. The chemical composition of fuel is identified using Gas Chromatography-Mass Spectrometry. The values of power output, mean effective pressure and exhaust oxygen concentration are independently obtained from the numerical model and from the experiments. The engine performance is not significantly affected for biodiesel to diesel blending ratio of up to 30%. A higher oxygen concentration in the exhaust gas is observed with increase in blending ratio. The developed numerical model would be useful in studying the performance and emission characteristics for any alternative fuel with known calorific value and chemical composition.

Analysis of meat and bone meal clean combustion conditions

The combustion process of meat and bone meal (hereinafter referred to as MBM) must comply with a series of conditions and restrictions, which stem from environmental law and engineering, energy, and constructional requirements. To this end, a multi-dimensional analysis model was developed to determine the working area that provides optimal combustion process conditions. The input parameters consisted of the waste stream, exhaust gas oxygen concentration, and heat flux recovered as saturated steam. The limiting parameters of the MBM combustion process, such as the temperature of the exhaust gas after the post-combustion chamber, the temperature of the exhaust gas before the bag filter, and the exhaust gas residence time in the post-combustion chamber, constituted the output parameters. The results of the multi-dimensional analysis were visualized in terms of the distribution of the output parameter values obtained from the input parameter function. Based on a comparison of every output parameter to its corresponding limit value, optimal working areas of the thermal waste treatment system were defined. The research reveals that it is possible to determine the MBM combustion optimal working area that complies with all of the conditions and restrictions. It is worth understanding this working area during the design and construction of thermal waste treatment systems. The multi-dimensional analysis model has been verified under industrial conditions at a real MBM combustion facility.

Pressure Optimized PowEred Respirator (PROPER): A miniaturized wearable cleanroom and biosafety system for aerially transmitted viral infections such as COVID-19

The supply of Personal Protective Equipment (PPE) in hospitals to keep the Health Care Professionals (HCP) safe taking care of patients may be limited, especially during the outbreak of a new disease. In particular, the face and body protective equipment is critical to prevent the wearer from exposure to pathogenic biological airborne particulates. This situation has been now observed worldwide during the onset of the COVID-19 pandemic. As concern over shortages of PPE at hospitals grows, we share with the public and makers’ community the Pressure Optimized PowEred Respirator (PROPER) equipment, made out of COTS components. It is functionally equivalent to a Powered Air Purifying Respirator (PAPR). PROPER, a hood-based system which uses open source and easily accessible components is low-cost, relatively passive in terms of energy consumption and mechanisms, and easy and fast to 3D print, build and assemble. We have adapted our experience on building clean room environments and qualifying the bioburden of space instruments to this solution, which is in essence a miniaturized, personal, wearable cleanroom. PROPER would be able to offer better protection than an N95 respirator mask, mainly because it is insensitive to seal fit and it shields the eyes as well. The PROPER SMS fabric is designed for single-use and not intended for reuse, as they may start to tear and fail but the rest of the parts can be disinfected and reused. We provide a set of guidelines to build a low-cost 3D printed solution for an effective PAPR system and describe the procedures to validate it to comply with the biosafety level 3 requirements. We have validated the prototype of PROPER unit for air flow, ISO class cleanliness level, oxygen and carbon-dioxide gas concentrations during exhalation, and present here these results for illustration. We demonstrate that the area inside the hood is more than 200 times cleaner than the external ambient without the operator and more than 175 times with the operator and in an aerosol exposed environment. We also include the procedure to clean and disinfect the equipment for reuse. PROPER may be a useful addition to provide protection to HCPs against the SARS-CoV-2 virus or other potential future viral diseases that are transmitted aerially.

Limiting current type yttria-stabilized zirconia thin-film oxygen sensor with spiral Ta2O5 gas diffusion layer

In this study, we demonstrated a limiting current-type yttria-stabilized zirconia thin-film oxygen sensor with a gas diffusion layer composed of porous Pt and spiral Ta2O5, which were deposited via sputtering and rotational oblique evaporation, respectively. The rate of the oxygen gas diffusion through the porous Pt and spiral Ta2O5 films defined the limiting current level of the oxygen sensor. When evaporation angle was between 70° and 84°, the relative density of the spiral Ta2O5 was between 0.72 and 0.37. The microstructure of the spiral Ta2O5 film was maintained after annealing at 700 °C for 1 h. The characteristics of the limiting current were clearly observed between 400 °C and 600 °C, which can be attributed to the oxygen gas diffusion rate in the spiral Ta2O5 film. The current response time was 3 s or less after applying the voltage. The level of the limiting current was directly correlated with the oxygen gas concentration. Owing to the thermally stable spiral Ta2O5 microstructure, the characteristics of the limiting current, including the limiting current level and response time, were confirmed to be consistent for up to ten cycles of temperature modulations. The oxygen gas concentration and water vapor were separately measured by applying 1.1 V and 1.8 V, respectively. The presence of CO2 and H2 did not affect the limiting current level for its application in the atmosphere.

Investigation of Mild Steel Corrosion in the Cement Production Associated with the Usage of Secondary Fuels

The present work deals with the corrosion of mild steel (1.0037) used as the outer construction material of the preheater of a modern industrial cement production facility. The facility uses secondary fuels, which introduce considerable amounts of corrosive species. The situation at the examination sites in the preheater zone is tracked over a period of two years including operation and shut-down periods. The investigation is focused on (i) the acquisition of the underlying physicochemical conditions, such as moisture, temperature, and contamination data at the examination site of the preheater, (ii) the multianalytical identification of the formed corrosion products using scanning electron microscopy combined with energy-dispersive X-ray analysis, infrared spectrometry, Raman spectrometry, X-ray diffractometry, and Möβbauer spectrometry, and (iii) voltammetric and EIS laboratory investigations using model solutions. It was evidenced that corrosion takes place at a temperature level of about 100°C in the presence of moisture and oxygen as well as chloride ion as a consequence of the usage of secondary fuels. Typical hot-gas corrosion could be excluded under the current conditions. Appearance, structure, and nature of the corrosion products were found to be not mainly dependent on the varied length of exposure, but on the conditions of the hosting preheater intake. In addition to different FeOOH phases and hematite, magnetite was found, dependent on the oxygen concentration in the process gas. The decisive role of oxygen as key factor for the corrosion rate was electrochemically confirmed.

Torrefaction of corn straw in oxygen and carbon dioxide containing gases: Mass/energy yields and evolution of gaseous species

Pulverized corn straw biomass was torrefied in carrier gases which contain oxygen and carbon dioxide gases with the following proportions (3–7% O2, 13–17% CO2, 80% N2). Torrefaction took place at 275–375 °C, under atmospheric conditions. Upon such oxidative torrefaction, the mass and energy yields of this biomass decreased with increasing temperature and increasing oxygen concentration. Most of the chlorine and sulfur contents of the biomass were released to the gas phase, 52–90% and 55–98% respectively, with amounts increasing with increasing both torrefaction temperature and oxygen concentration. In the examined parameter ranges, temperature had a pronounced effect on the mass and energy yields and on the evolution of chlorine and other elements to the gas phase. Low temperatures decrease the energy input to the process and enhance the mass and energy yields of the solid product. At the examined temperatures, the mass and energy yields were also affected by the variation in the oxygen content of the input gas.

RESULTS OF RESEARCH FOR THE USE OF THE BIOGAS AND METHANE MIXTURE IN A GAS POWER PLANT ENGINE

The analysis of scientific publications over the past ten years in the line of creating gas ICEs in Ukraine, operating on natural gas, biogas or similar low-calorie fuels has been carried out. The objectives of the work are to summarize the results of studies on the use of model gas in a gas internal combustion engine operating as a power plant drive, to develop recommendations on biogas additives to natural gas depending on the power plant load, and to develop a fuel supply control algorithm. It is possible to simplify labor intensity of experimental work with the help of model gas - a mixture of natural and carbon dioxide. The article provides recommendations on setting up the power system and automatic regulation of a gas engine running on a mixture of natural gas (methane) and biogas. To solve the tasks, research was carried out on a gas-electric plant with a rated capacity of 30 kW. The unit was originally equipped with a spark-ignited 8-cylinder petrol engine and an electric generator. The base ICE was converted to pure gas engine with a compression ratio of 8.5. In the physical modeling of biogas to natural gas additives in the model gas, the volume fraction of carbon dioxide was increased to 30 % depending on the external load. By calculation, we determined a similar ratio of compressed natural gas and biogas additives. For the calculation, it was assumed that compressed natural gas contains 90...95 % of methane, and biogas 60 % of methane and 40% of carbon dioxide. The possibility of using biogas with 60 % methane as an additive to natural gas in piston ICEs with spark ignition has been confirmed. It was found that with a decrease in load, the share of biogas can increase and replace up to 85% of natural gas. When working on biogas additives, the values of the concentrations of hydrocarbons and residual oxygen in the exhaust gases were determined to control the setting of the gas equipment of the internal combustion engine. Under operating conditions, three test modes have been selected for the power plant: idle, 50 % load, rated mode. The research results can serve as the basis for creating a control algorithm for the supply of biogas additives to natural gas, depending on load changes.

Determination of the propagation state of the combustion zone during in-situ combustion by dimensionless numbers

Ensuring the sustainable propagation of the combustion zone is a prerequisite for in-situ combustion (ISC). The combustion zone propagation processes with different gas injection parameters and reservoir properties were simulated with CMG STARS and a method of determining the propagation state was proposed based on the theoretical analysis of the simulation results. The simulation results of 67 cases with different gas injection parameters and reservoir properties show that there are three states of combustion zone propagation: the sustainable state, the declined state and the extinguished state. The temperature of the combustion zone shows a good correlation with the state of the combustion zone propagation. With increases in the gas injection rate, oxygen concentration, and oil saturation and decrease in the rock permeability, the combustion zone temperature increases and the propagation state changes from the extinguished or declined state to the sustainable state. Analysis of the nondimensionalized energy conservation equation shows that the combustion zone temperature is determined by the two dimensionless numbers HD and CW with the determined core property and domain. A diagram for determining the time-averaged temperature of the combustion zone using the HD and CW numbers was established, with relative deviations within 7%. The combustion zone propagation state under the combination conditions of the gas injection rate, oxygen concentration, oil saturation and reservoir permeability can be judged according to the predicted combustion zone temperature. The proposed method helps optimize the design of gas injection parameters in combustion tube tests and ISC oilfield applications.