Air Injection Rate Research Articles

Development of a multigeneration system with underground coal gasification integrated to bitumen extraction applications for oil sands

In this study, a combined system for syngas, bitumen, hydrogen and electricity production is developed and analyzed. The proposed system consists of steam assisted gravity drainage (SAGD), underground coal gasification (UCG), solid oxide fuel cell (SOFC), integrated gasification combined cycle (IGCC) and an electrolyser. The present system offers significant practical advantages for the regions, containing both coal and oil reserves such as Alberta region. Coal, as an alternative to natural gas for generating steam, is gasified using high temperature and pressurized steam in underground cavity. The produced syngas is utilized in both IGCC and SOFC systems. By using the excess steam in IGCC, SAGD process is run, and bitumen is extracted as in-situ extraction. In addition, a part of generated power is used in an electrolyser to produce hydrogen. The present system is analyzed in terms of energy and exergy methodologies to assess the performance of the cycles. Additionally, the effects of various system parameters, such as ambient temperature and pressure, syngas temperature, coal and syngas lower heating values, air and steam injection rates on energy and exergy efficiencies of the subsystems and overall system are evaluated. The energy and exergy efficiencies of the overall system are calculated as 19.6% and 17.3%, respectively.

Investigation of Lean Premixed Swirl-Stabilized Hydrogen Burner With Axial Air Injection Using OH-PLIF Imaging

In the context of lean premixed combustion, the prevention of upstream flame propagation in the premixing zone, referred to as flashback (FB), is a crucial challenge related to the application of hydrogen as a fuel for gas turbines. The location of flame anchoring and its impact on FB tendencies in a technically premixed, swirl-stabilized hydrogen burner are investigated experimentally at atmospheric pressure conditions using planar laser-induced fluorescence of hydroxyl radicals (OH-PLIF). The inlet conditions are systematically varied with respect to equivalence ratio (ϕ=0.2−1.0), bulk air velocity u0 = 30–90 m/s, and burner preheat temperature ranging from 300 K to 700 K. The burner is mounted in an atmospheric combustion test rig, firing at a power of up to 220 kW into a 105 mm diameter quartz cylinder, which provides optical access to the flame region. The experiments were performed using an in-house burner design that previously proved to be highly resistant against FB occurrence by applying the axial air injection strategy. Axial air injection constitutes a nonswirling air jet on the central axis of the radial swirl generator. While a high rate of axial air injection yields excellent FB resistance, reduced rates of air injection are utilized to trigger FB, which allowed to investigate the near FB flame behavior. Results show that both, fuel momentum of hydrogen and axial air injection, alter the isothermal flow field as they cause a downstream shift of vortex breakdown and, thus, the axial flame front location. Such a shift is proven beneficial for FB resistance from the recorded FB limits. This effect was quantified by applying an edge detection algorithm to the OH-PLIF images, in order to extract the location of maximum flame front probability xF. By these means, it was revealed that for hydrogen xF is shifted downstream with increasing equivalence ratio due to the added momentum of the fuel flow, superseding any parallel augmentation in the turbulent flame speed. The parameter xF is identified to be governed by J, the momentum ratio between fuel and air flow, over a wide range of inlet conditions. These results contribute to the understanding of the sensitivity of FB to changes in the flow field, stemming from geometry changes or specific fuel properties.

Energy and exergy analyses of an integrated underground coal gasification with SOFC fuel cell system for multigeneration including hydrogen production

A novel integrated system, including underground coal gasification (UCG), steam assisted gravity drainage (SAGD) based oil sands, syngas fueled Solid Oxide Fuel Cell (SOFC), integrated gasification combined cycle (IGCC) and an electrolyzer, for hydrogen production is proposed and analyzed for practical applications, especially for Alberta region in which there are huge capacity of oil sands and coal reserves. This combined multi generation system produces syngas from underground coal without mining, produced syngas is utilized for generating electricity from IGCC and SOFC. A part of generated electricity in the Rankine cycle is used for hydrogen production through an electrolyzer. The excess steam in IGCC is utilized for SAGD process in order to extract Bitumen from underground as in-situ extraction. Energy and exergy analyses are conducted to assess the performance of the cycle, and the effects of various system parameters on energy and exergy efficiencies of the overall system and its subsystems are studied comparatively. The overall energy and exergy efficiencies of the system are found as 29.2% and 26% respectively for 20 kg/s coal feed rate. Furthermore, the effects of varying ambient temperature and pressure, syngas temperature, coal and syngas lower heating value, air and steam injection rates on the system performance are investigated.

Study of Two-Phase Natural Circulation Cooling of Core Catcher System Using Scaled Model

A two-phase natural circulation cooling has been proposed to remove melted core decay heat by external core catcher cooling system during sever accident scenario. In this paper, two types of the core catcher cooling loops, one with heated loop and the other adiabatic loop simulated with air water system are analytically studied. First, a scaling analysis was carried out for natural circulation flow in a closed loop. Based on the scaling analyses, simulation of two-phase natural circulation is carried out both for air–water and steam–water system in an inclined rectangular channel. The heat flux corresponding to the decay heat is simulated with steam generation rate or air flux into the test section to produce equivalent flow quality and void fraction. Design calculations were carried out for typical core catcher design to estimate the expected natural circulation rates. The natural circulation flow rate and two-phase pressure drop were obtained for different heat inputs or equivalent air injection rates expressed as void fraction for a select downcomer pipe size. These results can be used to scale a steam water system using scaling consideration presented. The results indicate that the air–water and steam water system show similar flow and pressure drop behavior.

Self-sustaining smouldering combustion of coal tar for the remediation of contaminated sand: Two-dimensional experiments and computational simulations

This study presents the development and validation of a computational model which simulates the propagation of a smouldering front through a porous medium against unique experiments in coal tar and sand. The model couples a multiphase flow solver in porous media with a perimeter expansion module based on Huygens principle to predict the spread. A suite of two-dimensional experiments using coal tar-contaminated sand were conducted to explore the time-dependent vertical and lateral smouldering front propagation rates and final extent of remediation as a function of air injection rate. A thermal severity analysis revealed, for the first time, the temperature–time relationship indicative of coal tar combustion. The model, calibrated to the base case experiment, then correctly predicts the remaining experiments. This work provides further confidence in a model for predicting smouldering, which eventually is expected to be useful for designing soil remediation schemes for a novel technology based upon smouldering destruction of organic contaminants in soil.

Multiphase Flow Simulation for In Situ Combustion to Investigate Field-scale Hydraulic Heterogeneity and Air Injection Rate Affecting Oil Production

The article presents numerical analyses on the effects of field-scale hydraulic heterogeneity and air injection rate for production behavior of in situ combustion. Hydraulic heterogeneity is an essential reservoir property on determining the movement of a combustion front while the air injection rate is a key operational factor on maintaining the combustion front. Hydraulic heterogeneity affects significantly occurring viscous fingerings but may not be critical at the averaged cumulative production. The lower air injection rate results in the extensive combustion front and the large amount of ultimate recovery if the front is maintained before it reaches a production well.

Study on Effective Parameters in Caustic Regeneration on LPG Sweetening

General demercaptanization of LPG sweetening method used in Iran's South Pars Gas Complex is a Sulfrex process that is based on the ability of a sulfonated cobalt phthalocyanine, to catalyze the oxidation of mercaptans to alkyl disulfides under caustic condition by air. The aims of this work were to study and optimize the caustic regeneration condition. At first caustic regeneration process was represented. Thereafter, effect of the main operating variables including regeneration temperatures, caustic concentration, and air injection rate to the oxidizer on the caustic regeneration were studied, and at the end operational process parameters according to laboratory results were optimized and tuned.

Drainage type oil and heavy-oil displacement in circular capillary tubes: Two- and three-phase flow characteristics and residual oil saturation development in the form of film at different temperatures

It is still uncertain to what extent pore scale mechanisms, such as the counter and co-current nature of multiphase flow, the trapping mechanisms, the distribution of phases, and heat transfer mechanisms affect the process of isothermal and non-isothermal gravity drainage dominated oil and heavy-oil recovery. This type of processes is encountered during gas injection into oil reservoirs for enhanced oil recovery under isothermal conditions. Steam injection in thick reservoirs where gravity displacement is an effective mechanism and steam assisted gravity drainage (SAGD) are well-known examples of a non-isothermal gravity dominated heavy-oil recovery applications. It is commonly observed that field scale applications of the latter yield less recovery than estimated. One may also encounter this type process in the removal of any crude oil contamination in shallow zones where steam injection is used for cleaning. All these require in-depth analysis of the problem at the pore scale to account for the residual oil saturation (Sor) in the swept zone. In this paper, we used a single capillary tube (radius<0.03 cm) to mimic an elementary volume in the swept area during gravity dominated displacement applications and studied the flow characteristics of two and three phase flow with emphasis on film development. We carried out two-phase (air–oil) and three phase (air–oil–initial water saturation) flow displacements in a capillary tube under different temperature conditions, varying the air injection rate and the capillary properties. Detailed visualization experiments were carried out to analyze (1) the effects of heavy oil viscosity, wettability and spreading coefficient on displacements at different temperature conditions, (2) the interplay among capillary, gravity and viscous (air injection rates) forces and wettability using different capillary sizes (pore size), and (3) the residual oil saturation in the form of film development and phase distribution in the capillaries (mainly the thicknesses of the wetting and non-wetting phases). The experimental observations suggest that for heavy oil there is a threshold capillary number around 1.0E−2 over which the oil recovery (and therefore the residual oil saturation) is very sensitive to the capillary number, i.e., the injection rate, interfacial tension, wettability and temperature. At lower capillary numbers (typical range for oil reservoirs) temperature and hence viscosity do not have a significant influence in the residual oil saturation of the processed and crude oils; for horizontal displacement the residual oil saturation is a function of the capillary forces and for gravity drainage experiments it depends of the competition between capillary and gravity forces (Bond number).

Numerical simulation of mechanism of high-pressure air injection (HPAI) in light oil reservoirs

Abstract Based on the research progress of the crude oil oxidation-combustion model proposed by predecessors, this paper established a new multi-reaction model for high-pressure air injection (HPAI) process to compare the HPAI performance in reservoirs without water injection and high water cut reservoirs by numerical simulation. Results show that gas override is universal in air injection in light oil reservoirs before and after waterflooding, and is more apparent in strongly heterogeneous reservoirs. However, the produced oxygen concentration is very low all the time. For reservoirs that haven't gone through water injection, at high air injection rate oil is very likely to auto-ignite and keep high peak temperature and long time stable combustion front. However, there exists a critical value for the influence of air injection rate on the combustion front moving speed, above the critical value, oil recover factor increment is not obvious with the increase of air injection rate. At the same air injection rate, high water cut reservoirs are 6.3% lower in recovery factor than reservoirs without water injection, With high increase in GOR and high water recovery degree during HPAI process. It is suggested that polymer gel/ and or foam assisted air injection be taken to reduce GOR/ and or water cut in production wells.

Modeling of Coupled Mechanical–Hydrological Processes in Compressed-Air-Assisted Tunneling in Unconsolidated Sediments

This paper presents an analysis of coupled hydrological–mechanical processes in the construction of tunnels using the compressed air technique. The compressed air is applied in the tunnel space during the construction to prevent a water inflow. The paper uses a methodology that links two computer codes TOUGH2 and FLAC3D such that hydrological-mechanical analysis can be conducted. An air flow test conducted in Essen, Germany, was simulated, and the results agreed well with the field measurements. Subsequently, a numerical simulation of compressed air tunneling was performed to analyze the air injection rate and the surface displacements. The calculated air losses from the tunnel are within the range of the field observations. The analysis of surface settlement shows upward heaving and a decrease in the magnitude of surface settlement, which is consistent with the field observations.

Bubble formation and flow instability in an effervescent atomizer

Bubble formation from a gas jet in a liquid cross flow inside the mixing conduit of an effervescent atomizer is studied using flow visualization. Air injection rates were varied from 0.99 × 10−5 to 4.94 × 10−5 kg/s, while maintaining a constant liquid cross-flow rate of 0.298 kg/s. Though gas–liquid ratio (GLR) and flow velocities dominate bubble formation, intermittent choking at the exit nozzle is shown to have a morphological impact on the bubbly flow. This impact is visible as a pressure wave that propagates upstream from the nozzle exit. This pulse is found to have a strong influence on bubble formation at the gas injection location leading to bubble distortion and breakup. In most cases, a liquid jet is observed to propagate through the centreline of larger bubbles as the pressure pulse passes.

Consistency Measures for Isoconversional Interpretation of In-Situ Combustion Reaction Kinetics

The reaction kinetics of an in situ combustion process were studied via ramped temperature oxidation within a kinetic cell system. A methodology is established for rapid assessment of consistency among the various heating programs needed to interpret the apparent activation energy versus conversion or temperature. The isoconversional principle based on multiple programs of temperature versus time is applicable to interpret the apparent activation energies of the series and coupled reactions comprising crude-oil combustion. The issue of measurement consistency was studied using both simulations and experiments. Three sets of ramped temperature oxidation experiments of different reactor designs, different air injection rates, and different sample mixture sizes were conducted. Both experimental and simulation results support that the isoconversional principle is a model-free interpretation tool and the principle is promising for the study of crude-oil reaction kinetics that involve multiphase, multicomponent, and multistep reactions.

Study on Cuttings Starting Velocity in Air Drilling Horizontal and Highly-Deviated Wells

Air injection rate as the key parameter of drilling air is directly related to the success of drilling procedure. In the previous studies, most of air injection rate models were built based on the vertical wells, which are not appropriate for horizontal and highly-deviated well and limit the wide application of air drilling to some extent. Based on the movement analysis of cuttings, this paper assumed that after the cuttings deposit to the low side of borehole, Air is injected to carry the cuttings out of the wellbore. Then, the starting velocity model in different hole angles is established through the stress analysis of cuttings motion, which can be used to calculate the minimum air injection rate. The numerical simulation results show that starting velocity of cuttings reaches the maximum in the hole angle 60-70 degrees. The larger diameter cuttings require a high starting velocity, which is difficulty to be transported. This means some appropriate methods should be applied for air drilling procedure, like using secondary crush tools. The subsidence degree is one important factor to the calculation model, and it is necessary to study cutting subsidence degree in next step.

Influence of aeration modes on leachate characteristic of landfills that adopt the aerobic–anaerobic landfill method

As far as the optimal design, operation, and field application of the Aerobic–Anaerobic Landfill Method (AALM) are concerned, it is very important to understand how aeration modes (different combinations of aeration depth and air injection rate) affect the biodegradation of organic carbon and the transformation of nitrogen in landfill solid waste. Pilot-scale lysimeter experiments were carried out under different aeration modes to obtain detailed information regarding the influence of aeration modes on leachate characteristics. Results from these lysimeter experiments revealed that aeration at the bottom layer was the most effective for decomposition of organic carbon when compared with aeration at the surface or middle layers. Moreover, the air injection rate led to different nitrogen transformation patterns, unlike the lesser influence it has on organic carbon decomposition. Effective simultaneous nitrification and denitrification were observed for the aeration mode with a higher air injection rate (=1.0L/min). On the other hand, the phenomenon of sequenced nitrification and denitrification could be observed when a low air injection rate (=0.5L/min.) was employed. Finally, it is concluded that, for AALM, air injection with a higher air injection rate at the deepest layer near the leachate collection pipe tends to accelerate the stabilization of landfill waste as defined in terms of the enhancement of denitrification as well as organic carbon decomposition.

Self-oscillation regimes in a liquid jet curtain separating gas regions with different pressures

The results of an experimental investigation of the self-oscillation regimes of liquid jet outflow into a plane channel with air injection in its dead end are presented. The effect of the volume of the cavity, or the air cushion, and its thickness (or channel width) on the flow is studied on a wide range of the gas injection rate and the liquid outflow velocity. The self-oscillation flow regimes are realized at a constant pressure of water in the supply tank and a constant mass flow rate of the air injected into the cushion. With increase in the air injection rate the self-oscillation regime realized at lower injection intensities is replaced by a higher-frequency regime. High-speed videofilming shows that the difference from the low-frequency regime consists in the absence of the direct interaction between the out flowing jet and the channel wall. It is found that in both low-frequency and high-frequency regimes the self-oscillation frequency and amplitude are independent of the cushion thickness but the moment of the regime changeover is determined by this parameter. It is established that there exists a threshold value of the cavity volume, behind which the low-frequency regime does not occur at any air injection rates.

Using Compressed Air Injection to Control Seawater Intrusion in a Confined Coastal Aquifer

Seawater intrusion into groundwater is an important problem in many coastal regions. Freshwater injection has been widely used to avoid seawater contaminating freshwater systems, but is not an attractive solution where freshwater is limited. We investigated the effects of injecting compressed air on seawater movement in a confined coastal aquifer using a numerical simulation. We used TOUGH2/EOS7 software to analyze the effects of injecting compressed air in preventing seawater intruding into a hypothetical confined coastal aquifer (Henry’s problem), simulating steady-state initial conditions and comparing the results with the literature sources. We then performed a transient-state numerical simulation to quantify the seawater intrusion control efficiency achieved by injecting air. The results showed that injecting compressed air can mitigate seawater intrusion: Saltwater was ejected from the aquifer and the seawater circulation disappeared. The injected air flowed upward and spread laterally near the top of the aquifer because of the groundwater and air densities. Injecting air significantly increased the groundwater and gas pressures near the air injection zone and at the top of the aquifer. The air injection rate increased rapidly, then increased gradually. Freshwater injection was also simulated using settings similar to those used for air injection, and this showed that seawater intrusion is prevented more efficiently by freshwater injection than air injection. However, freshwater resources are valuable, whereas air is readily available, so injecting air to mitigate seawater intrusion has great potential. The modeling approach that we used will be used as a foundation for future work.

Optimum Parameter Design of Microbubble Drag Reduction in a Turbulent Flow by the Taguchi Method Combined With Artificial Neural Networks

This study attempts to optimize parameters for the microbubble drag reduction in a turbulent flow based on experimental measurements. Five parameters were investigated: three are control factors (the area of air injection, bubble size, and the rate of air injection) and two are indicative factors (flow speed and the measured position of local shear stress). An integrated approach of combining the Taguchi method with artificial neural networks (ANN) is proposed, implementing the optimum parameter design in this study. Based on the experimental results, analysis of variance concluded that, among the control factors, the rate of air injection has the greatest influence on microbubble drag reduction, while bubble size has the least. The investigation of drag reduction characteristics revealed that the drag ratio decreases with an increasing rate of air injection. However, if the rate of air supplied exceeds a certain value, the efficiency of drag reduction can drop. In the case of optimum parameter design, a 21% drag reduction and an S/N ratio of 1.976 dB were obtained.

Determination of optimum injection flow rate to achieve maximum micro bubble drag reduction in ships; an experimental approach

Reduction in ship resistance, in order to decrease fuel consumption and also achieve higher speeds, has been the topic of major research over the last three decades. One of the most attractive ideas in this field is micro bubble drag reduction, which attempts to obtain optimum injection flow rate based on ship specifications. The model test results of a 70 cm catamaran model was used to quantify the effect of air injection rate on drag reduction, and to estimate a simple formulation for calculating an efficient injection rate by considering the main parameters of the ship, such as: length, width and speed. The test results show that excessive air injection decreases the drag reduction effect, while suitable injection reduces total drag by about 5%–8%.

Bubble characteristics of air–water bubbly jets in crossflow

This paper presents a detailed experimental study on bubble characteristics of bubbly jets in crossflow by injecting air–water mixtures vertically via a circular nozzle. Bubbles were observed to separate from the water jets after some distance from the nozzle. Bubble properties were measured at different sections along the gas-phase centerline trajectory. The results show that the radial distributions of void fraction, bubble frequency and bubble specific interfacial area generally follow the Gaussian distribution. The distribution of bubble velocity was found to be larger in the downstream side of a cross-section, but Gaussian in the transverse direction. The distribution of bubble diameter was found to be affected primarily by air and water injection rates and the distance from the nozzle. At a cross-section, the gas-phase exhibits an ellipse-shape for pure air injection, while a kidney-shape for a mixture of air–water injection. Bubble properties along the gas-phase centerlines were also investigated, and their values decay along the centerlines until reaching some terminal values. Finally, relation of bubble slip velocity with bubble diameter in crossflow was found close to that of single isolated bubbles in stagnant water, rather than that of bubbly jets in stagnant water.

Systematic investigation on parameters of solution blown micro/nanofibers using response surface methodology based on box‐Behnken design

ABSTRACTResponse surface methodology, based on the four‐factor, three‐level Box‐Behnken design, has been utilized to facilitate a more systematic understanding of the solution and processing parameters of solution blown polyethylene oxide (PEO) micro/nanofibers. The factors investigated include air pressure, solution concentration, nozzle diameter, and injection rate. Fiber diameters, ranging from 137 to 1982 nm, are associated with these variables by applying a response surface model. The linear coefficients of air pressure and solution concentration, the interactive effect between air pressure and injection rate as well as the quadratic terms of nozzle diameter and injection rate are demonstrated statistically significant. Verification of the response surface model is successfully accomplished. Consequently, this study puts forward an overview of the effect of solution and technical parameters on solution blown submicron PEO fibers and provides a train of thought for fabricating other micro/nanofibers. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1383‐1391, 2013