Off-gas treatment

Thermal decomposition of wastes during the combustion process generates gaseous effluents that contain the following  

Radioactivity may be present in the off-gas in the form of solid aerosols (dusts bearing radioactive emitters such as Co), in chemical gases (e.g. CO2 containing C) and in liquid aerosols (such as H2O condensed in cold sections of the system containing H). 

The primary objective of off-gas treatment is to ensure that radiological and chemical releases to the environment are minimal and in compliance with the regulatory standards for the specific pollutants. Analysis of waste feed characteristics and the combustion conditions should determine the expected presence of objectionable materials in the off-gas, and therefore the type of treatment necessary. The off-gas treatment systems may consist of dry (non-aqueous) or wet (aqueous) components or process steps. Further information on the treatment concepts may be found in Annex in of this guide and in Ref. [9]. 

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Off-Gas Treatment. Before the advent of the shear, the gases released from the spent fuel were mixed with the entire dissolver off-gas flow. Newer shear designs contain the fission gases and provide the opportunity for more efficient treatment. The gaseous fission products krypton and xenon are chemically inert and are released into the off-gas system as soon as the fuel cladding is breached. Efficient recovery of these isotopes requires capture at the point of release, before dilution with large quantities of air. Two processes have been developed, a cryogenic distillation and a Freon absorption. 

Consider common scrubbers, vents, sumps, drains, off-gas treatment and other opportunities for inadvertently mixing process materials. Cross-contamination potential at transfer stations should not be overlooked. 

Ozonation systems are comprised of four main parts, including a gas-preparation unit, an electrical power unit, an ozone generator, and a contactor which includes an off-gas treatment stage. Ancillary equipment includes instruments and controls, safety equipment and equipment housing, and structural supports. The four major components of the ozonation process are illustrated in Figure 8. 

Two-level diffuser contactors, which involve application of ozone-rich gas to the lower chamber. Lower chamber off-gases are applied to the upper chamber. Offgas treatment from contactors is an important consideration. Methods employed for off-gas treatment include dilution, destruction via granular activated carbon, thermal or catalytic destruction, and recycling. 

The used raw materials were TiCU, oxygen, Ar and NaOH. The reaction apparatus consisted of gas purifiers, reactant preheaters, reactor, water cooler, separator and an off-gas treatment unit. The reactor was a 27 mm in ID. (32 mm in O.D.), 1430 mm in length quartz tube that was heated by a horizontal electrical furnace. A quartz rod and a ceramic rod, 6 mm... 

Dangerous materials may require special equipment. Chlorination with gaseous chlorine requires quite expensive storage facilities. Chlorination with chlorine, thionyl chloride, sulphuryl chloride, phosphorus oxychloride, phosphorus trichloride, or phosphorus pentachloride, all of which are fairly hazardous, requires off-gas treatment. Some of these reactants can be recycled. Pyrophoric solids such as hydrogenation catalysts, anhydrous aluminium trichloride for Friedel-Crafts reactions, or hydrides used as reducing agents should usually be handled using special facilities. Therefore, all of the above proce.sses are usually carried out in dedicated plants. 

These factors affect the number of vapor extraction wells, vacuum level required, type of off-gas treatment, and length of time required for treatment.34... 

Most states require the capture and treatment of air stripper off-gas. Typical off-gas treatment technologies that are applicable to MTBE and other oxygenates are adsorption, thermal treatment, and biotreatment. 

T0130 Bohn Biofilter Corporation, Bohn Off-Gas Treatment... 

T0130 Bohn Biofilter Corporation, Bohn Off-Gas Treatment T0135 Calgon Carbon Corporation, Activated Carbon T0136 Calgon Carbon Oxidation Technologies, Rayox... 

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