Injected air

Like steam injection, in-situ combustion is a thermal process designed to reduce oil viscosity and hence improve flow performance. Combustion of the lighter fractions of the oil in the reservoir is sustained by continuous air injection. Though there have been some economic successes claimed using this method, it has not been widely employed. Under the right conditions, combustion can be initiated spontaneously by injecting air into an oil reservoir. However a number of projects have also experienced explosions in surface compressors and injection wells. 

In wet combustion, water is injected concurrently and alternately with air, extending the steam 2one and aiding heat transfer to the cmde oil reducing oil viscosity. This can decrease injected air produced oil ratio and improve project economics. 

The aerodynamic force (P) of the main stream and the momentum of the injected air change the X component of the directing jet. The X component of the directing jet can be calculated from... 

This system involves injecting air or gas downhole at the rates sufficient to attain annular velocity of 2,000 to 3,000 ft/min. Hard formations that are relatively free from water are most desirable for drilling with air-gas. Small quantities of water usually can be dried up or sealed off by various techniques. 

Scrubber. This removes excess water from the injected air (or gas) stream to ensure that a minimum of moisture is circulated (if dry air for drilling is required) and to protect the booster. 

A service well is a well drilled or completed for the purpose of supporting production in an existing field. Wells of this class are drilled for the following specific purposes gas injection (natural gas, propane, hutane, or flue gas), water injection, steam injection, air injection, salt water disposal, water supply for injection, observation, injection for in-situ combustion. 

Another measure to improve the removal of ethanol is air injection into the mixer during the silanization step. Air can be injected from the bottom part of the mixer using existing valves without any special outlet for the injected air. In these experiments air injection is switched on once the compound reached the silanization temperature (145°C) and the rotor speed is adjusted in order to maintain the silanization temperature. Figure 29.13 shows the properties of this compound compared to a compound that was silanized under the same conditions except with air injection switched off. Air injection lowers the Payne effect, Mooney viscosity, and water content in the compound, and ethanol removal is more effective. All other properties are comparable to the properties of a standard silica compound. 

High airflow rates may result in unintended fracturing leading to nonuniform flow or short-circuiting of injected air in the subsurface, or may result in unintended mobilization of contaminants as nonaqueous phase liquids (NAPL), dissolved in groundwater, or in soil gas. 

Cappuccino lovers would argue that the foam cap on the drink is the critical element to a great cappuccino. Steam frothing of milk to prepare a cappuccino coffee involves injecting air and steam into milk to create the foam and to heat the milk to near boiling. 

Waeschle (Fig. 13) has developed a pressure sensing plug system. The boosters in this system are actuated by pressure rises in the line. The Fluid-Schub system of Buhler, Fig. 14, uses valves to inject air from an auxiliary air line. A system that produces extruded flow of long plugs can also be devised as shown in Fig. 15. 

The process where the accident occurred consisted of six reactors in series. In these reactors cyclohexane was oxidized to cyclohexanone and then to cyclohexanol using injected air in the presence of a catalyst. The liquid reaction mass was gravity-fed through the series of reactors. Each reactor normally contained about 20 tons of cyclohexane. 

Isasmelt A two-stage lead smelting process. In the first stage, the lead concentrate is oxidized by injecting air down a Sirosmelt lance, using helical vanes to swirl the gas. In the second, the high-lead slag is reduced with coal. The process was developed by Mount Isa Mines and the CSIRO, Australia, and due for startup at Mount Isa in 1991. 

Injection of air the oxygen in the injected air will prevent sulfate-reducing conditions in the sewer. The DO concentration in the wastewater establishes an aerobic upper layer in the biofilm, and sulfide produced in the deeper part of the biofilm or the deposits that may diffuse into the water phase will be oxidized (cf. Figure 6.2). The oxidation of sulfide will mainly proceed as a chemical process, although microbial oxidation may also take place (Chen and Morris, 1972). Factors that affect the oxidation rate of sulfide include pH, temperature and presence of catalysts, e.g., heavy metals. 

When injecting air in pressure mains, it must be taken into account that the volume of oxygen only amounts to about 20%. The inert N2 gas — to some extent mixed with the incoming air—will be collected at the top part of a pipe. An automatic vent system to remove this gas may be installed. The pumping performance of an air-injected pressure main can be evaluated using a model for the energy loss. 

Figures 5.10 and 5.11, show that such conditions exist in gravity sewers that are subject to a variability that proceeds in time and space. Changing aerobic and anaerobic conditions also appear in pressure mains when injecting air or pure oxygen. The integrated aerobic-anaerobic concept based on Figures 5.5 and 6.8 is shown in Figure 6.10.

The effectiveness of air sparging as a remediation tool depends on several variables, including soil type, the method of air injection, and the type and concentration of contaminants. The particle size and gradation of a particular soil determine the flow pattern in which the injected air will travel. 

Use of pulsed air injection rather than continuous air injection may improve performance at many sites. After a system has been operating for a period of time, the concentration of contaminant in the recovered air declines. Continued injection of the same volume of injected air recovers less VOC. Injection of air in a pulsed pattern allows time for reestablishment of a greater concentration gradient toward air channels and a more uniform concentration throughout the contaminant plume area. When the system is resumed, volatilization is again the predominant removal mechanism. 

Air sparging Injects air below the water table and captures it above the water table to extract volatile contaminants and promote biodegradation Can be inefficient in low-permeability zones and complex geologic settings Typically limited to depths less than 30 ft Multicomponent mixtures can adversely affect extractability... 

In-well aeration is the process of injecting air into the lower portion of a dual-screened well with perforations at the bottom and above the water table. As the bubbles rise, they expand, which causes the mixed mass of air and water to have less density. The result is an air-lift pump effect. When the water rises and exits the upper perforations, replacement water enters the bottom of the well. The result is a circulation cycle. Free air does not enter the aquifer, but dissolved air (and oxygen) travels with the circulating water. Figure 9.4 is a schematic diagram of in-well aeration. 

In some applications, it is necessary to inject nutrients or other chemicals into the aquifer to effect a more efficient restoration. Most of the time, additives are injected into separate wells. These additives may include surfactants, nutrients, pH adjustment chemicals, or additional carbon sources. Some success has been achieved with injected heated air to improve volatility of the chemicals. Where a small quantity of methane (as a primary substrate) is required, it can be added with the injection air. The lower explosive limit (LEL) of methane in air is 5% thus, extreme care must be used to control the mixture and the methane content of the vapor that reaches the surface. 

Traditionally air sparging has been used as a groundwater remediation tool. Occasionally, however, it has been successfully used to remediate the vadose zone. In this application, the compressed air is injected through a well screen that is open to the VOC-contaminated area. The injection wells may be either vertical or horizontal (Figure 10.7). In this setting, the injected air is usually captured by a corresponding set of SVE wells (Figure 10.8). Properly spaced patterns of injection and recovery wells are necessary for efficient operation. 

Inject air through well screen or open formation for 20 seconds at 75 psi... 

The formation of bubbles at orifices in a fluidised bed, including measurement of their size, the conditions under which they will coalesce with one another, and their rate of rise in the bed has been investigated. Davidson el alP4) injected air from an orifice into a fluidised bed composed of particles of sand (0.3-0.5 mm) and glass ballotini (0.15 mm) fluidised by air at a velocity just above the minimum required for fluidisation. By varying the depth of the injection point from the free surface, it was shown that the injected bubble rises through the bed with a constant velocity, which is dependent only on the volume of the bubble. In addition, this velocity of rise corresponds with that of a spherical cap bubble in an inviscid liquid of zero surface tension, as determined from the equation of Davies and Taylor ... 

The flow control system provides facilities for injecting air, steam, oxygen or other fluids into the reactor, and is governed by d/p cell transmitters and pneumatically-activated valves which permit automatic or manual regulation of flow rates and pressures. 

It is assumed in estimates 1 and 3 that a single Envitco melter would be used. For estimates 2 and 4, a bank of four melters operating in tandem was used. For estimates 2 and 4, it was assumed that at any one time three of the four melters would be operational. It is noted that the use of injected air or oxygen instead of sodium nitrate would lower treatment costs (D14867Y,... 

For ISSZT, a physical barrier, such as a slurry wall or vertical membrane barrier, is installed around the area of contamination to a depth that will be slightly below the future lowered groundwater level to limit the escape of air from the area. Existing clay or silt may serve as a cap for the system, otherwise a man-made cap is installed. Wells are installed into the soil to inject the low-pressure compressed air beneath the cap. As the air pressure increases, the groundwater is lowered. The injected air is prevented from escaping by the cap at the top, the barrier along the sides, and the water table at the bottom. 

Continuous injection is accomplished by drilling two wells into the oil sand deposit, one injection well and one recovery well. Into the injection well, air is pumped at high pressure, and bitumen at the base of the well is ignited. Air injection continues and moves the combustion process along as temperatures of 660°F to 940°F (350°C to 450°C) are attained. The bitumen is thermally cracked and vaporized. The cracked oils, gases, and vapors are driven toward the production well by injected air and recovered. 

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