Direct Air Injection Research Articles

Residual Strength of Liquefied Soil: The Effect of Induced Partial Saturation

Abstract Post-liquefaction response and residual strength play important roles in stability assessment of liquefied ground. Considering the recent advancements in the application of induced partial saturation for liquefaction mitigation, the state of knowledge in estimating the residual strength should be extended for liquefied desaturated soils. In this paper, the residual strength response of a clean sand at different saturation levels was investigated using a ring shear device. Direct air injection was used to desaturate the soil, which helped with mitigating the liquefaction under cyclic loading. However, by raising the shear strain level, both saturated and partially saturated soils were liquefied, followed by residual strength measurement. Results indicate that the residual strength increased with a reduction of the saturation level because of the change in compressibility and consequent volume reduction. In addition, the strain-rate dependency of the residual strength was confirmed because an increase of shear strain rate resulted in an increase in residual strength under both saturated and partially saturated conditions.

Simultaneous degradation of phenol-Cr(VI) wastewater on air injection plasma electrolysis using titanium anode

Phenol and Cr(VI) are dangerous wastewater were degraded simultaneously by reactive chemical species on plasma electrolysis reactor where direct air injection into plasma zone which titanium as the working electrode. Air injection contributes to increasing the formation of the radical species, such as radical ·OH, ·H, O2·−, and H2O2 molecules, even reducing the energy consumption. The effects of various air injection flow rates, pH, and voltages on phenol–Cr(VI) degradation were observed. The removal efficiency on the binary system was achieved 66% for phenol and 91% for Cr(VI) within 30 min, where the optimum condition of air injection flow rate is 0.2 L min−1 and pH 3.7. The energy efficiency of degradation was compared with that in other competitive processes. Increasing the voltage at constant power decreases the number of ·OH and ·H and increases the number of H2O2 molecules, indicating the formation of new reactive species. This study validated the synergistic effect on the simultaneous oxidation and reduction processes in wastewater.

A novel air plasma electrolysis with direct air injection in plasma zone to produce nitrate in degradation of organic textile dye

AbstractNitrogen is one of the essential nutrients for plants. Even though its availability in the air is abundant, it cannot be utilized yet due to its structure. Plasma electrolysis by air injection is effectively degrade organic textile dyes waste. In this study we propose a novel air plasma electrolysis (APE) where direct air injection into plasma zone inside electrolysis plasma can converts air into nitrate, while simultaneously the degradation of dyes waste produces organic nitrogen. Degradation of organic textile dye by APE can also transform nitrogen‐rich organic wastewater into nitrogen fertilizers. In this experiment, Remazol red as a compound in the azo dye group was used as a model for organic textile dye wastewater. Air plasma electrolysis reactor equipped with a stainless‐steel cathode, a tungsten anode, with various air injection rates and electric power. The results show 99.82% Remazol red degradation and 41.41 mmol of nitrate production. Preliminary efficacy tests on tomato plants showed that the nitrogen fertilizers produced from Remazol red produce the best plant growth. This study shows that APE simultaneously reduces organic textile dye waste, transforms them into potential organic fertilizer, and at the same time, synthesizes nitrates.

Effect of direct air injection through anode in plasma electrolysis process for batik dye wastewater treatment

Plasma electrolysis has been proved have much higher effectivity in degrading complex pollutant contained in batik dye wastewater. This study aims to investigate the effect of gas bubbles with air injection of plasma electrolysis in decolorization process. A new method to form bubbles using injection of air directly through anode with a tiny hole of glass tube is proposed. This research work presents the effects of gas injection rates on various phenomena such as electrical power of discharge pulses, concentration of OH radicals, and the decolorization percentage of remazol red as the dye waste in a batch reactor system. Experimental results showed that direct injection of air through anode can reduce the required energy for plasma generation significantly compared to non gas injection. Energy consumption for discharge plasma was observed lowered at higher rates of gas injected. Optimum gas flow rate at different voltage has been evaluated based on the physical and chemical characteristics of plasma. At higher required energy due to higher operation voltage used, the required gas injection rate to effectively degrade the waste was found higher.

Impact of fish feed on airlift pumps in aquaculture systems

Airlift pumps are commonly used in aquaculture systems to circulate water and maintain critical gas levels. In production marine reuse systems, a significant decrease in airlift pump flowrate was visually observed immediately after feeding. In experimental systems without fish, it was found that feed additions of less than 10 mg/L decreased water flow by as much as 78% for diffuser injectors but only 10% for pumps with direct air injection. For both injector types, feed impact diminished over several hours but persisted longer in seawater than in freshwater. Video footage revealed increasing bubble coalescence with the addition of feed. The decrease in pump flow is likely attributed to water property changes due to compounds leaching out of the feed. This decrease in pumping rate has the potential to negatively impact water quality, system performance, and fish health.

Cerebral arterial gas embolism following cardiopulmonary bypass surgery

A 13-year-old boy with a history of tetrology of Fallot underwent a pulmonary value replacement procedure. Gas bubbles were observed in the bypass circuit during the procedure. Trendelenburg position, one of the older standard recommendations when AGE is suspected, was established during the remainder of the procedure [2]. The patient could not support respirations adequately and remained minimally responsive following the procedure. Hyperbaric oxygen therapy was implemented to reduce gas bubble volume and facilitate diffusion of gas back into solution [3]. During the hyperbaric oxygen therapy, the patient experienced three cardiac arrests requiring chest compressions and pressor support. Following the hyperbaric procedure, the patient remained without brainstem reflexes and did not breathe spontaneously. Crepitus was present throughout the abdominal and pelvic areas. The accompanying scan (Fig. 1) was performed six hours after the hyperbaric procedure ended to confirm the diagnosis. Fig. 1 Computerized tomography scan of the brain after hyperbaric treatment for iatrogenic arterial gas embolism. The white and gray matter differentiation is lost and the sulcal pattern is obliterated. Numerous cortical vessels, especially in the anterior and ... Arterial gas embolism (AGE) is a known complication of underwater diving using compressed air and a rare complication of medical procedures. Iatrogenic causes are more common in procedures that access the arterial circulation, such as cardiopulmonary bypass surgery and angiography, but can also be caused by procedures that access the venous system when accompanied by a cardiovascular defect that results in shunting of blood from the venous to the arterial system [1,2]. Although AGE and the central nervous system complications of AGE have been discussed in the literature, examples of neuroimages associated with central nervous system complications are not well documented. A case is presented to familiarize the neurologist with the conspicuous neuroimaging findings associated with AGE. Iatrogenic AGE is uncommon, but can occur as a result of pulmonary barotrauma during mechanical ventilation and through direct injection of air into the vascular system [1,2]. Procedures that access the arterial system, such as cardiopulmonary bypass or angiography, can results in injection of air directly into the arterial system. Gas in the venous system can rarely result in AGE when a right-to-left shunt exists. Such shunts are common when an atrial septal defect or patent foramen ovale exists and in congenital cardiac anomalies. Since children are more likely to have untreated congenital cardiac abnormalities and vascular shunts and are at high risk for barotraumas, AGE is an entity with which pediatric specialists should be familiar. Initial supportive procedures are implemented when AGE occurs. These include administration of 100% oxygen, discontinuation of nitrous oxide and support of vital functions. Although Trendelenburg and lateral decubitus positions have been recommended in the past, since the buoyancy of gas bubbles is not sufficient to counteract the force of the blood flow towards the head, supine positioning in now recommended [1, 2]. In addition, Trendelenburg position can exacerbate cerebral edema [3]. Hyperbaric oxygen treatment or retrograde perfusion can be considered if supportive procedures are not effective [4,5]. A reduction in cerebral metabolism through barbiturate coma, especially when seizures are present, may be effective [1].

Effects of perfluorocarbon emulsions on microvascular blood flow and oxygen transport in a model of severe arterial gas embolism

BackgroundArterial gas embolism (AGE) is a clinical problem that occurs directly in cardiopulmonary bypass machines in open-heart surgeries, or indirectly (through cardiac or pulmonary right to left shunts) in dive accidents, resulting in serious morbidity and even death. Perfluorocarbon (PFC) emulsions have been used for the treatment of AGE in an animal model. We hypothesized that PFC emulsions enhance microvascular blood flow, speed bubble resolution, and oxygenation in AGE compared with saline in a model of cremaster muscle from anesthetized rats. Materials and methodsAGE was induced by direct air injection into the femoral artery ipsilateral to the studied cremaster muscle. Microhemodynamics, microvascular, and tissue oxygenation were determined before and after treatment with two different commercial PFC emulsions (C10F20, Oxycyte; Oxygen Biotherapeutics, Inc and C10F18, PHER-O2; Sanguine Corporation, Inc) compared with saline in real time using brightfield and phosphorescence microscopy. ResultsBlood pressure and heart rate remained unchanged. Systemic PO2, oxygen (O2) content, and glucose were higher in PFC groups, whereas hematocrit dropped in all groups. Arteriolar blood flow went up 85% and 80% of baseline after C10F20 and C10F18 treatments, respectively, versus 11% after saline treatment. Arteriolar and tissue PO2, and O2 delivery were higher in PFC groups compared with the control group. There was an increase in arteriolar blood flow, reduction in diffusional resistance of O2 in the plasma, and improved tissue oxygenation. ConclusionsAdministration of PFC emulsions in AGE is superior to saline primarily because of surfactant properties along with air bubble reabsorption.

Biotrickling filters for biogas sweetening: Oxygen transfer improvement for a reliable operation

An industrial-scale biotrickling filter for the removal of high concentrations of H2S is described in this work. The system has been operating at H2S inlet concentrations between 1000 and 3000ppmv at acidic conditions. A decrease of pH from 2.6 to 1.8 did not affect the biological activity inside the biofilter while reducing the water make-up consumption up to 75%. The current oxygen supply system, based on direct injection of air to the liquid phase, has demonstrated to be inefficient for a long-term operation leading to elemental sulfur accumulation in the packing material (i.e. promoting clogging episodes). The present study demonstrates it is possible to partially remove (40.3%) the deposited elemental sulfur by bio-oxidation when biogas is not fed. In normal operation conditions, the implementation of an aeration system based on jet-venturi devices has shown quite promising results in terms of oxygen transfer efficiency and robustness. Such improvement of oxygen transfer was translated in a better conversion of H2S to sulfate, which increased around 17%, prolonging the lifespan operation at low-pressure drop.

In vivo microvascular mosaics show air embolism reduction after perfluorocarbon emulsion treatment

Massive arteriolar gas embolism (AGE) has never been evaluated in vivo using intravital microscopy and previous perfluorocarbon (PFC) emulsions were only effective in AGE when administered before AGE. We implemented a new system for quantitative studies of massive AGE using brightfield microscopy and tested a treatment with a third-generation PFC emulsion after massive AGE. We studied bubble dynamics in cremaster muscles from anesthetized rats after AGE was induced by direct air injection into the femoral artery ipsilateral to the studied muscle. Using a motorized microscope stage and a color camera, in vivo microvascular mosaics were produced on-line from over 2000 digital images to evaluate multiple networks in order to investigate the distribution, lodging, breaking, reduction and moving of 105 air bubbles in microvessels. Thirty minutes after PFC treatment, there was a reduction of 80% in bubble volume while untreated and saline-treated rats showed significantly smaller decreases of 33% and 40%, respectively (p<0.05). Air bubbles also dissolved into a larger number of smaller bubbles after PFC treatment. The proposed methodology may prove useful for rapid in vivo data acquisition from large networks. Since large air bubbles broke-up, decreased in length and volume, and moved toward smaller microvessels, the study provides quantitative data to support a mechanism by which PFC may improve tissue blood flow following massive AGE. The findings suggest that this new generation of PFC emulsions administered after severe AGE may reach compromised microvascular networks and provide help to alleviate microvascular obstruction by increasing air bubble reabsorption.

Managed-Pressure Drilling Using a Parasite Aerating String

Summary Drilling on top of the mesa in the Piceance basin presents a significant lost-circulation and stuck-pipe challenge to operators wanting to exploit the gas reserves in the area. Operators have experienced losses that exceed 4,000 bbl of mud when the intermediate section is drilled using conventional techniques. This is because of a combination of natural fractures and weak rock. Various strategies have been deployed to tackle the problems, including underbalanced-drilling (UBD) operations and directional casing while drilling. A new technique implemented by an operator in the Piceance basin is described in this paper; it involves acquiring real-time equivalent-circulating-density (ECD) data and control of mud weight in the annulus by use of direct air injection through a parasite aerating string (PAS). During the development stages of this new process, a real-time annular-pressure sensor was run in the bottomhole assembly (BHA) to gather diagnostic data. Analysis of the data shows conventional drilling practices often yield up to 3 lbm/gal variation in ECD exposed to the formation. The analysis also suggests that there is a fracture-reopening gradient of approximately 8.3 lbm/gal and that there are significant ECD variations during connections. The new strategy shows that these wells can be drilled with an ECD in the range of 5-7 lbm/gal using conventional water-based-mud systems. This strategy allows wells with a narrow mud-weight window to be drilled without significant mud loss to the formation. This approach avoids the use of complex multiphase models, and the downhole ECD can be displayed on the driller's console in real time from the data measured by the annular-pressure sensor and sent through the mud-pulse-telemetry measurement-while-drilling (MWD) tool. Alternatively, if an annular-pressure sensor is not included in the BHA, the downhole ECD can still be estimated accurately by use of a simple spreadsheet calculation (Scott 2009). This gives a measure of flexibility in deploying the technique to the wellsite. Expert personnel were used in the initial diagnostic stages to establish the procedures and validate the effectiveness of the technique. After that, they will not normally be required at the wellsite to manage the process in subsequent wells because the ECD data from the annular-pressure sensor can be understood by the driller, and the alternative spreadsheet solution, if used, can also be managed by the wellsite supervisor to calculate a reliable downhole ECD measurement. The ECD data enable the driller to control and keep the annular pressure within recommended limits, ensuring that lost circulation risk is reduced and wellbore stability is maintained. The alternative approach of using conventional well-design techniques would result in multiple casing strings and in cost overruns, while more-advanced techniques such as directional casing while drilling and UBD would require specialized equipment and crews. This new technique uses existing and common drilling technologies along with new software tools for geomechanics analysis and drilling surveillance to achieve a fit-for-purpose solution. This paper presents a risk-management technique using today's conventional technologies to successfully mitigate lost circulation risk in the Piceance basin.

Hydrogen from an Internally Circulating Fluidized Bed Membrane Reactor

A novel fluidized bed membrane reactor has been developed for the production of high-purity hydrogen based on steam methane reforming (SMR). The reactor incorporates perm-selective membranes for in-situ removal of hydrogen from the reactor, thus shifting the thermodynamic equilibrium of the SMR reaction. The membranes also eliminate the need for downstream hydrogen purification.The endothermic reaction duty is provided either by external heating of the vessel wall or through direct air injection into the fluidized catalyst bed (autothermal reforming). The gas flow pattern within the fluidized bed induces internal circulation of catalyst particles between the central reaction (permeation) zone and outer heating zones. The circulating hot catalyst particles from the oxidation zone carry the required endothermic heat of reaction for the reforming while ensuring that the palladium membranes are not exposed to high temperatures or to oxygen. Another characteristic of the reactor configuration is that very little of the nitrogen present in the oxidation air reaches the reaction zone, thus maintaining the hydrogen driving force for the perm-selective membranes.The reactor concept was proven in a pilot reactor (0.13 m diameter, 2.3 m tall). A number of variables were studied, including steam-to-carbon ratio, temperature and pressure. The pilot reactor was operated with both external heating and direct air addition. Pure hydrogen (99.999+%) was obtained from the reactor and an equilibrium shift was demonstrated. The maximum pure hydrogen recovery obtained from the pilot reactor was 0.96 mol H2/mol CH4, limited by the installed membrane surface area for these tests.

Separation kinetics of karnal bunt (Tilletia indica) infected wheat (Triticum aestivum) grains in a fluidized bed / Cinética de separación de granos de trigo (Triticum aestivum) infectados con carbon parcial (Tilletia indica) en un lecho fluidificado

Infection of breadmaking wheat grains by karnal bunt ( Tilletia indica) is a common disease in north- western Mexican states, causing major economic losses. In this work, the feasibility of separating infected from wholesome wheat grains by using fluidized bed technologies was evaluated. The pro posed separation equipment was of the batch type and fluidization was attained via direct air injec tion into the grain bed. Minimum fluidization rates were determined and effects of infected grain composition in the bed were studied. The experimental results showed that the separation of infected grains was quite possible with small losses of wholesome wheat grains. A quantitative characteriza tion of the separation process was made by determining the separation kinetics from the available experimental data. Separation kinetics were shown to be useful for estimating the equipment operat ing time to attain an allowed level of grain infection, as established by the Mexican government for the commercialization of wheat.

Electrocatalysis at chemically modified electrodes

Abstract The electrocatalytic response of chemically modified carbon paste and glassy carbon electrodes with anchored Fe(II)/Fe(III) centers is presented for gaseous species such as NO 2 , SO 2 , H 2 S, and Cl 2 . Carbon paste electrodes are modified by direct admixing of tris[4,7-diphenyl-1,10-phenanthroline]iron(II) perchlorate, and glassy carbon electrodes are modified by oxidative electropolymerisation of tris[5-amino-1,10-phenanthroline]iron(II) perchlorate. The electrocatalytic cycle operating in the integrated reaction/pre-electrode layer of chemically modified electrodes results in significant signal enhancement. Chemical modification of the conducting surfaces protects the electrode surface from poisoning. evaluation was done in a continuous-flow system using gravitational flow fo supporting electrolyte carrier propulsion, direct injection of air containing parts per billion or parts per million (v/v) of the gaseous species, and amperometric detection with the chemically modified electrodes as part of a thin-layer cell.

Biological Nitrification in an Up Flow Fixed Bed Reactor (UFBR)

This paper describes a kinetic model for ammonification and nitrification in an upflow fixed bed reactor (UFBR) with direct injection of air into the support material. Modeling has been based on the computation of active biomass concentration along the reactor. The tests, which extended over a period of one year and have been applied to municipal sewage after conventional treatment using activated sludge, have shown that the filtration rate is the most important factor as regards both the overall quantity of biomass found in the system and the distribution of this biomass within the reactor. The optimum quantity of biomass is obtained with a filtration rate of around 5 m3.m2.hr. Under these conditions, it is then possible to reach active biomass concentrations 8 to 9 times higher than the ones found in conventional processes based on the use of nitrifying activated sludge. It is also clearly evidenced that ammonification will, in most cases, be incomplete and this will limit the efficiency of the overall reaction Total N → NO3−. Other parameters also greatly influence the process : among these parameters, the influence of the ratio air process rate/influent rate has been the subject of special examination.

64. On the Experience of Pneumoencephalography with Direct Injection of Air

64. On the Experience of Pneumoencephalography with Direct Injection of Air