Gas control

Acid gas control efficiency not as high as with wet scrubber... 

Process-flow control and buffer-gas control have been discussed under Variable Nozzles and Buffer-Gas System respectively. Speed is usually self-controlled by a matching speed-sensitive load such as a compressor or a pump. If the load is an induction or svn-chronous generator feeding into a stable ac system, the system frequency fixes the speed. Otherwise, the speed can be controlled by a conventional governor. 

A variation on the wet-spinning technique involves extruding into a heated gas environment. In this dry-spinning process, the temperature and composition of the gas control the extraction process. 

Bameby Sutcliffe Site describes company providing activated carbon, air purification, solvent recovery, emission control, remediation, odor control, corrosive gas control, pollution control, air filterr, and distillation equipment. http //www.bscarbons.com... 

Passive perimeter gas control systems are designed to alter the path of contaminant flow through the use of trenches or wells, and typically include synthetic flexible membrane liners (FMLs) and/or natural clays as containment materials. The membrane is held in place by a backfilled trench, the depth of which is determined by the distance to a limiting structure, such as groundwater or bedrock. A permeable trench installation functions to direct lateral migration to the surface, where the gases can be vented (if acceptable) or collected and conveyed to a treatment system (Figure 10a and 10b). 

An active perimeter gas control system can have any of the same configurations as a passive perimeter system with the addition of any combination of gas extraction wells, gas collection headers, vacuum blowers or compressors. Their ultimate purpose is to direct the gas to a treatment or utilization system. 

Figure 10a. Passive gas control using a permeable trench (U.S. EPA, 1985).

Car-Sealed Closed Valve - In certain cases it may be advantageous to use car sealed closed valves, such as in a bypass around a fuel gas control valve used for furnace flameout protection. The bypass is provided so that the automatic shutdown system can be periodically checked for operation. Where CSC valves are used for other purposes, they are also limited to appUcations where inadvertent opening of the CSC valve would not overpressure the equipment by more than 1.5 times design pressure. 

Corti. G. and Manfrida G. (1998), Analysis of a semi-closed gas lurbine/combined cycle (SCGT/CC) with CO2 removal by amines absorption. International Conference On Greenhouse Gas Control Technologies, Interlaken. 

Procedure (ii). Make certain that the instrument is fitted with the correct burner for an acetylene-nitrous oxide flame, then set the instrument up with the calcium hollow cathode lamp, select the resonance line of wavelength 422.7 nm, and adjust the gas controls as specified in the instrument manual to give a fuel-rich flame. Take measurements with the blank, and the standard solutions, and with the test solution, all of which contain the ionisation buffer the need, mentioned under procedure (i), for adequate treatment with de-ionised water after each measurement applies with equal force in this case. Plot the calibration graph and ascertain the concentration of the unknown solution. 

A double-beam atomic absorption spectrophotometer should be used. Set up a vanadium hollow cathode lamp selecting the resonance line of wavelength 318.5 nm, and adjust the gas controls to give a fuel-rich acetylene-nitrous oxide flame in accordance with the instruction manual. Aspirate successively into the flame the solvent blank, the standard solutions, and finally the test solution, in each case recording the absorbance reading. Plot the calibration curve and ascertain the vanadium content of the oil. 

Passive gas control systems control gas movement by altering the paths of flow without the use of mechanical components. There are generally two types, high-permeability and low-permeability. 

High-permeability passive perimeter gas control systems entail the installation of highly permeable (relative to the surrounding soil) trenches or wells between the hazardous waste site and the area to be protected (Figure 16.6). The permeable material offers conditions more conductive to gas flow than the surrounding soil, and provides paths of flow to the points of release. High-permeability systems usually take the form of trenches or wells excavated outside the site, then backfilled with a highly permeable medium such as coarse crushed stone. 

Low-permeability passive perimeter gas control systems (Figure 16.7) effectively block gas flow into the areas of concern by using barriers (such as synthetic membranes or natural clays) between the contaminated site and the area to be protected. In the low-permeability system, gases are not collected and therefore cannot be conveyed to a point of controlled release or treatment. The low-permeability system can also alter the paths of convective flow. 

High-permeability and low-permeability passive perimeter gas control systems are often combined to provide controlled venting of gases and blockage of available paths for gas migration.15... 

The applications and limitations of passive gas control systems must also be understood. They can be used at virtually any site where there is the capability to trench or drill and excavate to at least the same depth as the landfill. Limiting factors could include the presence of a perched water table or rock strata. Passive vents should generally be expected to be less effective in areas of high rainfall or prolonged freezing temperatures. 

FIGURE 16.6 Passive gas control using apermeable trench. 

The cost of passive gas control systems is low. The passive concept has virtually no operating or maintenance costs. However, it is recommended that periodic inspections be made and that the surface gas be periodically monitored in the area being protected to ensure that the systems are performing their intended functions. 

Active perimeter gas control systems control off-site gas migration with the use of an active control system to alter pressure gradients and paths of gas movement by mechanical means. Three or four major components are required in active perimeter gas control systems ... 

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