Purification, of waste gases

Sazanova TV. Creation of sorbents for the purification of waste gases of industrial production from fluorine compounds. Cand. thesis. Ivanovo Khimico-tekhnologjcheskii Univ, 2000. 

Muller H, Deller K, DespeyrouxB, Peldszus E, Kammerhofer P, KiihnW, etal. Catalytic Purification of Waste Gases Containing Chlorinated Hydrocarbons with Precious Metal Catalysts. Catal Today 1993 17 383-390. 

Depending on the process, the most frequently used liquid superficial velocity range is fix>m Z=2 mV(m h), in case of vacuum rectification, to X=300 m /(m h), in case of some high-pressure absorption processes [1]. In some cases of purification of waste gases, the optimal liquid superficial velocity in the packing is some times lower than L=2 sxr/(m ), which requires using distributors able to operate at lower liquid superficial velocities. 

Gases from waste incineration plants are often treated with powdered activated carbon, which is injected into the flue gas stream. Subsequently, the added PAG is separated from flowing gas on a fabric filter. Thus, the filtration cake is deposited on the fabric and a further removal of pollutant (e.g. dioxins and furans) takes place in the fixed bed of activated carbon [162]. Due to relatively high temperatures (ca. 343-423 K), the purification of flue gases is often carried out with the use of activated coke. Two examples of operational conditions are given in Table 13. 

Protection of the environment from the impurities originating from industrial wastes and transportation means is a very important and current problem. Adsorbents play a significant role in neutralization of waste gases and sewages and at the same time in capturing valuable components found in wastes. Compared with other methods, adsorbents allow for the most thorough purification of raw materials with relatively low costs. 

The main applications of PSA are to be found in the production of oxygen from air, dehumidification of gases and purification of hydrogen. Other applications include removal of carbon dioxide, recovery of radioactive waste gas, enrichment recovery of rare gases, purification of helium, purification of natural gases, separation of isomers and separation of carbon monoxide. Separation of iso-parafllns from normal paraffins is accomplished by using a shape-selective adsorbent such as a molecular sieve. Separation of carbon monoxide involves chemical adsorption on complex adsorbents. 

Burning of gas exhausts on flares allows reducing pollution of air basin by toxic substances considerably. However, salvaging of waste gases of the oil refining and petrochemical enterprises on flares is not a rational method of protection of environment. Therefore, it is necessary to provide decrease in exhausts of gases on a torch. Application of effective systems of purification of gas exhausts result in to reduction of number of torches at the petrochemical enterprises [2]. 

Kotler VR, Pein R. Reduction of waste gases without flue gas purification at thermal power plants (USA experience). Fuel Energy Abstr 1995 36 356—62 [in Russian]. 

The purification of exhaust gases from burners working on liquid and gas fuel is accomplished by using oxidation catalysts of Perrovski t3 e oxides - ABO3 combined with ozonation. Ozone is injected prior the waste gases flow. A may be La, Pr or other alkali earth element B may be Co, Mn or other transition metal. A may be also partially substituted by Sr, Ca or any other alkali earth element. A catalyst deposited on ceramic support of honeycomb type may contain SrCOgjMnp Oj. It is oxidized 24% CO in the absence of ozone and 80% in ozone atmosphere [14]. 

Carbon also is produced and used in other forms namely, activated carbon, carbon black, and coke, that have many commercial applications. Structurally they are amorphous forms of carbon belonging to the graphites. Activated carbon or activated charcoal has a highly porous honeycomb-like internal structure and adsorbs many gases, vapors, and colloidal solids over its very large internal surface area. Some of its major applications include purification of water and air, air analysis, waste treatment, removal of subur dioxide from stack gases, and decolorization of sugar. 

Dispersion of the waste gases leads to the dilution of the pollutants in the atmosphere. Self-purification mechanisms of atmospheric air also assists the... 

Use Purification of drinking water industrial waste treatment deodorization of air and sewage gases bleaching waxes, oils, wet paper, and textiles production of peroxides, bactericide. Oxidizing agent in several chemical processes (acids, aldehydes, ketones from unsaturated fatty acids), steroid hormones, removal of chlorine from nitric acid, oxidation of phenols and cyanides. 

The catalytic activity of the SHS ceramic catalysts in the processes of incineration was found to be virtually identical to that of widespread precious metal catalysts. The ceramic catalysts prepared by promising SHS technique may be a challenge to conventional catalysts for purification of engine exhaust and other waste gases. 

The range of applications is somewhat restricted, since the cost of most polymeric adsorbents is typically about ten times more than that of other common adsorbents. In some instances, polymeric materials are the only choice. In other cases, they compensate for the cost differential by yielding much better performance, especially for high value-added uses. Current applications include recovery and purification of antibiotics and vitamins, decolorization, decaffeination, hemop-erfusion, separation of halogenated light orgaifics from water, and treatment of certain industrial wastes such as aqueous phenolics and VOC recovery from off-gases. 

The most active foam catalysts were tested in the process of neutralization of gas emissions of furnaces for wire enameling. Waste gases contained mixture of vapors of different (mainly aromatic) organic compounds in amount of 10-50 g/m. Temperature of the waste gases was 380-450°C. The existing catalytic neutralization system (2 % Pd on Nichrome wire) did not give the necessary degree of purification (72-80 % conversion only). 

Despite a significantly lower adsorption capacity of activated carbons for the removal of SOj and NO from flue gases in comparison with the VOC removal capacity, there are many processes in which they (or activated cokes) are applied for purification of industrial fumes [171-174] from coal fired power plants and waste incinerators. Activated coke is a carbonaceous adsorbent manufactured from lignites or hard coals. Typically, the specific surface areas of commercially available activated cokes are relatively low (up to 400 m g" ) and the pore volumes are only up to ca. 0.25 cm g Depending on the material origin and the manufacturing process, either adsorptive or catalytic characteristics may play a dominant role in the removal of contaminants on this adsorbent. The majority of activated cokes is used for the removal of SO and dioxins fiom waste and flue gases. 

Solubility calculations are merely phase-equilibrium calculations applied to supercritical gases in liquids, solids in liquids, and solutes in near-critical fluids. The last application has drawn substantial attention, for near-critical extraction processes are being applied, not only in the chemical and energy industries, but also in food processing, purification of biological products, and clean-up of hazardous wastes. 

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