Pressure Air Injection Research Articles

Performance and completion assessment of an in-situ aerated municipal solid waste landfill – Final scientific documentation of an Austrian case study

By converting anaerobic landfills into a biologically stabilized state through accelerating aerobic organic matter degradation, the effort and duration necessary for post-closure procedures can be shortened. In Austria, the first full-scale application of in-situ landfill aeration by means of low pressure air injection with simultaneous off-gas collection and treatment was implemented on an old MSW-landfill and operated between 2007 and 2013. Besides complementary laboratory investigations, which included waste sampling from the landfill site prior to aeration start, a comprehensive field monitoring program was conducted to assess the influence of the aeration measure on the emission behavior of the landfilled waste during the aeration period as well as after aeration completion. Although the initial waste material was described as rather stable, the lab-scale aeration tests indicated a significant improvement of the leachate quality and even the biological solid waste stability. However, the aeration success was less pronounced for the application at the landfill site, mainly due to technical limitations in the full-scale operation. In this paper main performance data of the field investigation are compared to four other scientifically documented case studies along with stability indicators for solid waste and leachate characteristics in order to evaluate the success of aeration as well as the progress of a landfill towards completion and end of post-closure care. A number of quantitative benchmarks and relevant context information for the performance assessment of the five hitherto conducted international aeration projects are proposed aiming to support the systematization and harmonization of available results from diverse field studies and full-scale applications in future.

The influence factors analysis of the light crude oil oxidation reaction process

ABSTRACTDuring the high pressure air injection process, there are different types of oxidation reactions, which do not exist, and the predominant reaction type of is dependent on the specific conditions. In this study the influences of formation temperature, pressure, and oxidation time on light crude oxidation have been studied via oxidation experiments. And it is shown that the reaction types could be effectively improved by the temperature increment, which decreases the oil viscosity. As well, the pressure and oxidation time have obvious effects that were mainly present in oxygen addition reactions and the viscosity increase.

Pressurized air injection in an axial hydro-turbine model for the mitigation of tip leakage cavitation

Tip leakage vortex cavitation in axial hydro-turbines may cause erosion, noise and vibration. Damage due to cavitation can be found at the tip of the runner blades on the low pressure side and the discharge ring. In some cases, the erosion follows an oscillatory pattern that is related to the number of guide vanes. That might suggest that a relationship exists between the flow through the guide vanes and the tip vortex cavitating core that induces this kind of erosion.On the other hand, it is known that air injection has a beneficial effect on reducing the damage by cavitation. In this paper, a methodology to identify the interaction between guide vanes and tip vortex cavitation is presented and the effect of air injection in reducing this particular kind of erosion was studied over a range of operating conditions on a Kaplan scale model.It was found that air injection, at the expense of slightly reducing the efficiency of the turbine, mitigates the erosive potential of tip leakage cavitation, attenuates the interaction between the flow through the guide vanes and the tip vortex and decreases the level of vibration of the structural components.

Pneumatic microfinger with balloon fins for linear motion using 3D printed molds

Polymer-based pneumatic balloon actuators consisting of novel trapezoidal vertical microballoon fins were fabricated by three-dimensional (3D) printed molds and validated experimentally. The introduction of 3D printed molds for pneumatic actuation provides additional freedom in the design of actuators, removing the limitation of extruded 2D shapes that is present with conventional microfabrication. Whereas conventional balloon actuators exhibit nonlinear response to applied pressure, the presence of balloon fins with 100s-μm width was shown to produce a linear change in bend angle with the injection of pressurized air. The balloon fins also mitigate stress concentrations that can lead to material failure. Static bending (exceeding 80° bend angle) and the mechanical force of the fabricated microfingers were tested and compared with analytical models. The expanded design space permitted by 3D printing allows actuator designs to achieve a given deflection with less stress in the material as compared to planar designs. Feasibility of this design flexibility and fast prototyping enabled by the 3D printed molding process was demonstrated by fabricating and testing various designs of microfingers. When grouped, the microfingers with balloon fins can successfully accomplish complex object transfer tasks (i.e., multi-directional actuation with independently controlled displacement).

Recovery of light oil by air injection at medium temperature: Experiments

Abstract Volatile oil recovery through air injection is a promising method for highly heterogeneous low permeability reservoirs. Thermal effects due to oxidation reaction, vaporization/condensation and flue gas drive are the most important mechanisms for light oil recovery by medium pressure air injection. To gather evidence for this claim, we performed ramped temperature experiments with consolidated cores filled with hexadecane injecting either air or nitrogen at different injection rates at medium pressures. The experiments show that oxygen is removed from the injected air through physical and chemical sorption by the hydrocarbon at low temperatures. Most of the bonded oxygen is released later at higher temperatures and reacts to form carbon oxides. The amount of oil burned in the air injection process relative to the amount of oil recovered increased from 2% at 10 bar to 18% at 30 bar, and again decreased to 5% at 45 bar and 3% at 70 bar. This trend was predicted theoretically in an earlier study of the medium temperature oxidation process.

Variation of reservoir fluid property during the high pressure air injection process

ABSTRACTThis research aimed at determining the variation of reservoir fluid property during the high-pressure air injection process. For this purpose, the forward multiple contact experiment was employed by pressure–volume–temperature (PVT) system to investigate the physical property variation of the crude oil and the complex oxidation reactions. The results show: under the relative low temperature and pressure condition, instead of carbon dioxide, carbon monoxide dominates the products in the air phase. The gas/oil ratio and volume ratio increased due to the generated gas while the viscosity and density achieved a descending trend. The colloid and bitumen in the oil phase reduced by half but the amount of wax achieved a small increase. The low-temperature oxidation and pyrolysis reactions caused the fluctuated change of the different compounds. The amount of light compounds decreased at the beginning and then increased while that of heavy compounds showed the opposite trend. But at last, due to the H/C ratio, the light compounds increased to more than their initial value.

The Kinetic Analysis of Coke Formation Under Differential Air-oil Ratio During High Pressure Air Injection

For studying the heavy oil property change during high pressure air injection process, constant temperature oxidation tube experiments have been finished to study the influence of air-oil ratio on the oxidation process with thermoanalysis methods. The results presented an increasing amount of formation coke was contained with the air-oil ratio increment. When the air-oil ratio reached 200:1, the oxidation process was promoted and the oxide was identified as “coke” with smell. Based on the Arrhenius method, it indicated the air concentration has positive influences on the coke deposition conducive to form and sustain stable combustion front.

Low-Temperature Oxidation and Characterization of Heavy Oil via Thermal Analysis

High pressure air injection (HPAI) without ignition has attracted extensive attention in the air injection based improved oil recovery (IOR) process for light oil reservoirs but was rarely proposed as an IOR process for heavy oil reservoirs. This study aims at evaluating the potential of HPAI without ignition for deep, high pressure, heavy oil reservoirs (Tahe oilfield, Tarim Basin, China). Many low-temperature oxidation (LTO) experiments were carried out to study the oxidation behavior of heavy oil under the reservoir conditions (120 °C, about 30–40 MPa) using an isothermal oxidation reactor. The produced gases were analyzed using gas chromatography for their content of O2, CO2, CO, and hydrocarbon gas (C1–C6) content. The apparent hydrogen/carbon (H/C) and molar ratio of the carbon oxides (m-ratio) were also calculated from effluent gases to analyze oxidation behavior. The effects of quartz, reservoir core (characterized by X-ray diffraction), formation water, and catalyst on LTO were analyzed. Thermogravimetry (TG-DTG) experiments were conducted to characterize the oxidation behavior and kinetics of heavy oil. The Arrhenius method was employed to calculate reaction activation energy. The isothermal oxidation experimental results show that reservoir core, formation water, and catalyst have important influences on LTO. The upgrading of heavy oil occurred in the presence of catalyst. The inflammable coke was formed, and combustion reaction happened at 40 MPa and 120 °C after oxidation for 7 days, which implies heavy oils have a spontaneous combustion potential for HPAI without ignition process in Tahe heavy oil reservoir. Simultaneously, the heavy oil upgrading indicates that HPAI without ignition process in the presence of catalyst is a promising and potential air injection based IOR technique for deep, high pressure, heavy oil reservoirs such as the Tahe oilfield.

The Kinetic Analysis of Oxidized Oil During the High Pressure Air Injection by Thermal Kinetic Analysis

Studying the changing of the oil property with injected air is the prerequisite to apply the HPAI technique in heavy oil reservoir. For this purpose, the oxidation experiments have been carried to study the influence of pressure on heavy oil analyzed by thermogravimetry and differential scanning calorimetry. The results indicated that the oxidized oil with lower activation energy is easier to react with the oxygen. So the higher pressure has positive influence on the coke deposition with stable combustion front. Sufficient coke will bring the possibility for application of HPAI technique without ignition devices in heavy oil reservoirs.

Effects of water on light oil recovery by air injection

We formulate a mathematical model for one dimensional flow with chemical reactions resulting from injection of air into a porous medium initially filled with gas, water and volatile oil. Our goal is to investigate the effect of water and steam on oil recovery, and we do so for a medium pressure air injection process. We show that, when the boiling point of the volatile oil is below or slightly above the boiling point of water, the hot steam region moves upstream of the medium temperature oxidation (MTO) wave (where oil vaporization and combustion occur), while the volatile oil and steam condense at the same location; it leads to considerable improvement of oil recovery by the MTO wave. Remarkably, the recovery curves (recovery fraction vs. time) depend weakly on the initial water and light oil saturations. If the volatile oil boiling point is much higher than the boiling point of water, the steam region moves downstream of the MTO wave. In this case the water effect on recovery is weaker and becomes negative for high water saturations. Numerical calculations suggest the existence of an oil boiling point at which a bifurcation occurs that separates solutions with the steam region upstream or downstream of the combustion zone.

Pneumomediastinum and Subcutaneous Emphysema after High Pressure Air and Sand Injection Injury to the Upper Arm

We present a rare case of a 47-year-old man who developed pneumomediastinum and subcutaneous emphysema after a high pressure hose accidentally injected air and sand particles into his right upper arm. On presentation, he complained of dyspnoea and chest pain. He had palpable subcutaneous emphysema extending from the upper arm to his neck, face, and trunk. Plain X-ray films and computed tomography showed pneumomediastinum and subcutaneous emphysema, but no sand particles. Conservative treatment was done with close observation, and serial radiographs were obtained. There was complete resolution of the mediastinal and subcutaneous air after about two weeks with no evidence of infection. This was an extremely rare case of pneumomediastinum and severe subcutaneous emphysema occurring after accidental air injection injury to the upper arm. With regard to how air entered the mediastinal cavity, possible pathways are discussed. (Hong Kong j.emerg.med. 2014;21:51-54)

Experimental modelling of fragmentation applied to volcanic explosions

Explosions during volcanic eruptions cause fragmentation of magma and host rock, resulting in fragments with sizes ranging from boulders to fine ash. The products can be described by fragment size distributions (FSD), which commonly follow power laws with exponent D. The processes that lead to power-law distributions and the physical parameters that control D remain unknown. We developed a quantitative experimental procedure to study the physics of the fragmentation process through time. The apparatus consists of a Hele-Shaw cell containing a layer of cohesive silica flour that is fragmented by a rapid injection of pressurized air. The evolving fragmentation of the flour is monitored with a high-speed camera, and the images are analysed to obtain the evolution of the number of fragments (N), their average size (A), and the FSD. Using the results from our image-analysis procedure, we find transient empirical laws for N, A and the exponent D of the power-law FSD as functions of the initial air pressure. We show that our experimental procedure is a promising tool for unravelling the complex physics of fragmentation during phreatomagmatic and phreatic eruptions.

A method based on the Harcourt and Esson equation to estimate the catalytic effect of metallic additives on light crude oil

Abstract This paper provides the research on four different metallic additives during the combustion process and kinetic behavior of crude oil based on the Harcourt and Esson equation. The oil-only sample and oil-metal additive mixtures were studied by TG/DTG and DSC. The results indicate that Dagang crude oil exhibites three regions low temperature oxidation (LTO), fuel deposition and high temperature oxidation (HTO) during the heating process. The metal additives show obvious catalytic effects on the oil and ZnSO 4 . The exotherm increment benefits the high pressure air injection (HPAI) process. Based on the Harcourt and Esson equation, the activity energy requirement presents different values and trends in the LTO and HTO processes. Compared with the TG/DSC profile and activity energy, ZnSO 4 shows a positive effect on Dagang light crude oil during the HPAI process.

Comparison between lab- and full-scale applications of in situ aeration of an old landfill and assessment of long-term emission development after completion

Sustainable landfilling has become a fundamental objective in many modern waste management concepts. In this context, the in situ aeration of landfills has been recognised for its potential to convert conventional anaerobic landfills into biological stabilised state, whereby both current and potential (long-term) emissions of the landfilled waste are mitigated. In recent years, different in situ aeration concepts have been successfully applied in Europe, North America and Asia, all pursuing different objectives and strategies.In Austria, the first full-scale application of in situ landfill aeration by means of low pressure air injection and simultaneous off-gas collection and treatment was implemented on an old, small municipal solid waste (MSW) landfill (2.6ha) in autumn 2007. Complementary laboratory investigations were conducted with waste samples taken from the landfill site in order to provide more information on the transferability of the results from lab- to full-scale aeration measures. In addition, long-term emission development of the stabilised waste after aeration completion was assessed in an ongoing laboratory experiment. Although the initial waste material was described as mostly stable in terms of the biological parameters gas generation potential over 21days (GP21) and respiration activity over 4days (RA4), the lab-scale experiments indicated that aeration, which led to a significant improvement of leachate quality, was accompanied by further measurable changes in the solid waste material under optimised conditions. Even 75weeks after aeration completion the leachate, as well as gaseous emissions from the stabilised waste material, remained low and stayed below the authorised Austrian discharge limits. However, the application of in situ aeration at the investigated landfill is a factor 10 behind the lab-based predictions after 3years of operation, mainly due to technical limitations in the full-scale operation (e.g. high air flow resistivity due to high water content of waste and temporarily high water levels within the landfill; limited efficiency of the aeration wells). In addition, material preparation (e.g. sieving, sorting and homogenisation) prior to the emplacement in Landfill Simulation Reactors (LSRs) must be considered when transferring results from lab- to full-scale application.

Catalytic effect analysis of metallic additives on light crude oil by TG and DSC tests

This research aimed at the investigation of the effect of different metallic additive on the combustion and kinetic behavior of crude oil. For this purpose, the thermal behavior of the oil-only and oil–metallic salts mixtures were studies by the thermogravimetry (TG)/derivative thermogravimetry and differential scanning calorimetry (DSC) on heating rate at 10 °C min−1. The result shows that Dagang crude oil exhibited apparent low temperature oxidation (LTO), fuel deposition, and high temperature oxidation processes. With the addition of metallic salts, the LTO process has been shortened and samples added CuSO4, CrCl3·6H2O, and AlCl3·6H2O achieved a much lower peak temperature than that of oil. Based on the Arrhenius model, metallic additives were proven to have obvious influence on the combustion activation energy. And, by comprehensive analysis of TG/DSC profile and activation energy, ZnSO4 exhibited a positive influence on light crude oil combustion during the high pressure air injection process.

Local Application of Drugs to Study Nicotinic Acetylcholine Receptor Function in Mouse Brain Slices

Tobacco use leads to numerous health problems, including cancer, heart disease, emphysema, and stroke. Addiction to cigarette smoking is a prevalent neuropsychiatric disorder that stems from the biophysical and cellular actions of nicotine on nicotinic acetylcholine receptors (nAChRs) throughout the central nervous system. Understanding the various nAChR subtypes that exist in brain areas relevant to nicotine addiction is a major priority. Experiments that employ electrophysiology techniques such as whole-cell patch clamp or two-electrode voltage clamp recordings are useful for pharmacological characterization of nAChRs of interest. Cells expressing nAChRs, such as mammalian tissue culture cells or Xenopus laevis oocytes, are physically isolated and are therefore easily studied using the tools of modern pharmacology. Much progress has been made using these techniques, particularly when the target receptor was already known and ectopic expression was easily achieved. Often, however, it is necessary to study nAChRs in their native environment: in neurons within brain slices acutely harvested from laboratory mice or rats. For example, mice expressing "hypersensitive" nAChR subunits such as α4 L9'A mice (1) and α6 L9'S mice (2), allow for unambiguous identification of neurons based on their functional expression of a specific nAChR subunit. Although whole-cell patch clamp recordings from neurons in brain slices is routinely done by the skilled electrophysiologist, it is challenging to locally apply drugs such as acetylcholine or nicotine to the recorded cell within a brain slice. Dilution of drugs into the superfusate (bath application) is not rapidly reversible, and U-tube systems are not easily adapted to work with brain slices. In this paper, we describe a method for rapidly applying nAChR-activating drugs to neurons recorded in adult mouse brain slices. Standard whole-cell recordings are made from neurons in slices, and a second micropipette filled with a drug of interest is maneuvered into position near the recorded cell. An injection of pressurized air or inert nitrogen into the drug-filled pipette causes a small amount of drug solution to be ejected from the pipette onto the recorded cell. Using this method, nAChR-mediated currents are able to be resolved with millisecond accuracy. Drug application times can easily be varied, and the drug-filled pipette can be retracted and replaced with a new pipette, allowing for concentration-response curves to be created for a single neuron. Although described in the context of nAChR neurobiology, this technique should be useful for studying many types of ligand-gated ion channels or receptors in neurons from brain slices.

Simulation of Dynamic Two-Phase Flow During Multistep Air Sparging

Air sparging is an in situ soil/groundwater remediation technology, which involves the injection of pressurized air through air sparging well below the zone of contamination. To investigate the rate-dependent flow properties during multistep air sparging, a rule-based dynamic two-phase flow model was developed and applied to a 3D pore network which is employed to characterize the void structure of porous media. The simulated dynamic two-phase flow at the pore scale or microscale was translated into functional relationships at the continuum-scale of capillary pressure–saturation (P c–S) and relative permeability—saturation (K r–S) relationships. A significant contribution from the air injection pressure step and duration time of each air injection pressure on both of the above relationships was observed during the multistep air sparging tests. It is observed from the simulation that at a given matric potential, larger amount of water is retained during transient flow than that during steady flow. Shorter the duration of each air injection pressure step, there is higher fraction of retained water. The relative air/water permeability values are also greatly affected by the pressure step. With large air injection pressure step, the air/water relative permeability is much higher than that with a smaller air injection pressure step at the same water saturation level. However, the impact of pressure step on relative permeability is not consistent for flows with different capillary numbers (N ca). When compared with relative air permeability, relative water permeability has a higher scatter. It was further observed that the dynamic effects on the relative permeability curve are more apparent for networks with larger pore sizes than that with smaller pore sizes. In addition, the effect of pore size on relative water permeability is higher than that on relative air permeability.

Design of top covers supporting aerobic in situ stabilization of old landfills – An experimental simulation in lysimeters

Landfill aeration by means of low pressure air injection is a promising tool to reduce long term emissions from organic waste fractions through accelerated biological stabilization. Top covers that enhance methane oxidation could provide a simple and economic way to mitigate residual greenhouse gas emissions from in situ aerated landfills, and may replace off-gas extraction and treatment, particularly at smaller and older sites. In this respect the installation of a landfill cover system adjusted to the forced-aerated landfill body is of great significance. Investigations into large scale lysimeters (2×2×3m) under field conditions have been carried out using different top covers including compost materials and natural soils as a surrogate to gas extraction during active low pressure aeration. In the present study, the emission behaviour as well as the water balance performance of the lysimeters has been investigated, both prior to and during the first months of in situ aeration. Results reveal that mature sewage sludge compost (SSC) placed in one lysimeter exhibits in principle optimal ambient conditions for methanotrophic bacteria to enhance methane oxidation. Under laboratory conditions the mature compost mitigated CH4 loadings up to 300lCH4/m2d. In addition, the compost material provided high air permeability even at 100% water holding capacity (WHC). In contrast, the more cohesive, mineral soil cover was expected to cause a notably uniform distribution of the injected air within the waste layer. Laboratory results also revealed sufficient air permeability of the soil materials (TS-F and SS-Z) placed in lysimeter C. However, at higher compaction density SS-Z became impermeable at 100% WHC.Methane emissions from the reference lysimeter with the smaller substrate cover (12–52g CH4/m2d) were significantly higher than fluxes from the other lysimeters (0–19g CH4/m2d) during in situ aeration. Regarding water balance, lysimeters covered with compost and compost-sand mixture, showed the lowest leachate rate (18–26% of the precipitation) due to the high water holding capacity and more favourable plant growth conditions compared to the lysimeters with mineral, more cohesive, soil covers (27–45% of the precipitation).On the basis of these results, the authors suggest a layered top cover system using both compost material as well as mineral soil in order to support active low-pressure aeration. Conventional soil materials with lower permeability may be used on top of the landfill body for a more uniform aeration of the waste due to an increased resistance to vertical gas flow. A compost cover may be built on top of the soil cover underlain by a gas distribution layer to improve methane oxidation rates and minimise water infiltration. By planting vegetation with a high transpiration rate, the leachate amount emanating from the landfill could be further minimised. The suggested design may be particularly suitable in combination with intermittent in situ aeration, in the later stage of an aeration measure, or at very small sites and shallow deposits. The top cover system could further regulate water infiltration into the landfill and mitigate residual CH4 emissions, even beyond the time of active aeration.

Imbalance Response and Stability Characteristics of a Rotor Supported by Hybrid Air Foil Bearings

This article presents the imbalance response of a 4.84-kg rotor of 49 mm in diameter supported by hybrid air foil bearings (HAFBs). In this work, hybrid means hydrostatic injection of pressurized air into the air film. Previous experimental works by the authors on HAFBs with different designs (elastic supports, overall size, number of top foils) considered the load capacity at low speeds and the cooling effectiveness of the hybrid operation. The current article investigates the rotordynamics performance of HAFBs. The HAFB in this work has three top foils with hydrodynamic preload with a clearance distribution similar to traditional three-lobe bearings. The imbalance response in cylindrical mode is presented with different supply pressures (2.67–4.67 bar). Imbalance responses near the critical speeds do not clearly show the effect of increased pressure on the bearing stiffness, natural frequency, and damping around the critical speeds. However, the frequency of subsynchronous vibrations (considered to be the natural frequency of the rotor-bearing system) at high speeds increases slightly with the pressure. The increased supply pressure is more effective in suppressing the subsynchronous vibrations at high speeds rather than affecting the modal stiffness and natural frequencies. Prediction using modal impedance curves calculated from a linear perturbation method slightly overpredicts (4–9%) the measured natural frequencies.

In-situ biosurfactant flushing, coupled with a highly pressurized air injection, to remediate the bunker oil contaminated site

A pilot scale test for in-situ biosurfactant flushing coupled with a highly pressurized air injection (HPAI) was performed to remediate a bunker oil contaminated site. The contaminated area was located in Ulsan, Korea, which had been used for a roofing tile manufacturing facility for 25 years. This site was mainly contaminated by the leakage of bunker A- and C-oil from the old underground storage tank (the average TPH concentration of soil was 1,820 mg/kg). A pilot scale test site (17 m × 12 m × 4 m) was selected in the contaminated area and twelve injection wells and two extraction wells were established at the site. Two percent of biosurfactant solution was flushed into each injection well at 2 L/min, followed by HPAI (20 kgf/cm2) to accelerate the mobility of flushed solution in pore spaces and thus to increase the removal efficiency of in-situ flushing. The process of biosurfactant flushing with HPAI was repeated until about 1.9 pore volumes of biosurfactant solution (350 tons) were flushed at the test site. The effluent solution was gathered and treated by a post treatment process that included a chemical reaction tank. A total of 2.2 ton of TPH (82% of the initial TPH) was removed from the site within 1.9 pore volumes of biosurfactant solution flushing resulting in the average TPH concentration of the residual soil being below 500 mg/kg, suggesting that the in-situ biosurfactant flushing coupled with HPAI, is very useful in remediating bunker oil contaminated sites.