Adsorption and Incineration

This process involves a combination of activated carbon adsorption with incineration. The adsorber concentrates the organic laden air before treatment by incineration. This approach is particularly useful for organic streams with a low concentration and higher volumes ( 100 ppmv and flowrates over 20,000 cfin), such as paint spray booths. This process has many advantages. These include  

Condensation is a basic separation technique where a contaminated gas stream is first brought to saturation and then the contaminants are condensed to a liquid. The conversion of vapor to liquid phase can be accomplished either by increasing the pressure at constant temperature, or reducing the temperature, keeping the pressure constant. Generally, condensation systems are operated at a constant pressure. 

The design and operation of the system is affected by the concentration and type of VOC s in the emission stream. Before condensation can occur, the dew point of the system (where the partial pressure of the organic is the same as the system pressure) must be reached. As condensation continues, VOC concentration in the vapor decreases, and the temperature must be lowered even further. 

The removal efficiency of the condenser ranges from 50% to 95% or more and depends on the partial pressure of the organic in the gas stream, which is a function of the concentration of the organic and the condenser temperature. For a given temperature, the greatest potential removal efficiencies are achieved with the largest initial concentrations. VOC removal efficiencies via condensation may reach 95% or more for concentrations in excess of 5,000 ppmv. 

Plots of vapor pressure versus temperature (Cox charts) are used to determine the temperature required to achieve the desired removal efficiency. Generally, the condenser outlet organic concentration will be greater than 

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Hot air desorption Rotor adsorber are often desorbed by hot air Concentration by adsorption and incineration of the high calorific value desorbate... 

Steps. Thermal-swing cycles have at least two steps, adsorption and heating. A cooling step is also normally used after the heating step. A portion of the feed or product stream can be utilized for heating, or an independent fluid can be used. Easily condensable contaminants may be regenerated with noncondensable gases and recovered by condensation. Water-iminiscible solvents are stripped with steam, which may be condensed and separated from the solvent by decantation. Fuel and/or air may be used when the impurities are to be burned or incinerated. 

Thermal Desorption. Thermal desorption is an innovative treatment that has been appHed primarily to soils. Wastes are heated to temperatures of 200 to 600°C to increase the volatilization of organic contaminants. Volatilized organics in the gas stream are removed by a variety of methods including incineration, carbon adsorption, and chemical reduction. 

A number of papers have appeared on the removal of heavy metals in the effluents of dyestuff and textile mill plants. The methods used were coagulation (320—324), polymeric adsorption (325), ultrafiltration (326,327), carbon adsorption (328,329), electrochemical (330), and incineration and landfiU (331). Of interest is the removal of these heavy metals, especiaUy copper by chelation using trimercaptotria2ine (332) and reactive dyed jute or sawdust (333). 

Adsorption and condensation are the normal recovery options. If recycling is considered and is economically feasible, consideration of incinerators as destruction devices may be unnecessary. Generally, recovery units like adsorbers and absorbers result in higher total capital investment than modular, packaged incinerators. 

Condensation is normally used for the recovery of organic compounds from process or tank vent gases or from releases during loading. Condensation is used to recover valuable compounds prior to incineration, or to reduce the organic load entering other control systems, such as adsorbers or absorbers. Adsorption and absorption processes benefit from low condenser outlet temperatures. 

The technologies used in the control of gaseous organic compound emissions include destruction methods such as thermal and catalytic incineration and biological gas treatment and recovery methods such as adsorption, absorption, condensation, and membrane separation. The most common control methods are incineration, adsorption, and condensation, as they deal with a wide variety of emissions of organic compounds. The most common types of control equipment are thermal and fixed-bed catalytic incinerators with recuperative heat recovery, fixed-bed adsorbers, and surface condensers. The control efficiencies normally range between 90% and 99%. 

Several techniques for VOC removal have been investigated such as thermal incineration, catalytic oxidation, condensation, absorption, bio-filtration, adsorption, and membrane separation. VOCs are present in many types of waste gases and are often removed by adsorption [1]. Activated carbon (AC) is commonly used as an adsorbent of gases and vapors because of its developed surface area and large pore volumes [2]. Modification techniques for AC have been used to increase surface adsorption and hence removal capacity, as well as to improve selectivity to organic compounds [3]. 

Ammonia and acetic acid in waste water give rise serious pollution problems which bring about eutrophication of rivers, lakes, etc [1, 2]. These have been treated by the conventional method of biological techniques, adsorption, and thermal incineration. A band of researchers have suggested that the ammonia molecules could be transferred to N2 using a photocatalytic redox mechanism as shown follows 4NH3 + 3O2 2N2 + 6H2O. However, it has been... 

Economic feasibility studies suggest that even at the present state of the art photocatalytic technology indeed can be competitive with the traditional carbon adsorption or incineration technologies in treatment of contaminated soil vapor extraction vents and small scale VOC-containing vents [28]. Rapid progress in basic and applied research in photocatalysis suggests... 

Physico-chemical treatment techniques, precipitation, sedimentation, air flotation, filtration, crystallization, chemical oxidation, wet air oxidation, super-critical water oxidation, chemical reduction, hydrolysis, nanofiltration, reserve osmosis, adsorption, ion exchange, extraction, distillation, rectification, evaporation, stripping, and incineration. 

Radioactive metal wastes from the nuclear industry are of increasing concern as the amount of waste to be disposed of increases. Current treatment of nuclear wastewater involves the addition of lime, which is effective in precipitating most metals out of solution with the exception of radium (Tsezos Keller, 1983). Barium chloride (BaCl2) is used to precipitate radium from sulfur-rich effluents as barium-radium sulfate. Other treatment methods include incineration for some solid wastes, and filtration, adsorption and crystallization for liquid wastes (Godbee Kibbey, 1981). 

The volatile organic components that are emitted in the gaseous effluent can be controlled by a variety of technologies including scrubbing techniques, granular-carbon adsorption and fume incineration. The specific technology is selected on a case-by-case basis. 

Chlorinated aromatic compounds are hazardous compounds that result from various industrial and agricultural activities. Water disinfection, waste incineration, and uncontrolled use of biocides are the major sources of chlorinated aromatics in the environment. Chlorinated compounds are also formed as subproducts of the biochemical reactions of herbicides containing chlorophe-noxy compounds. Treatment of chlorinated compounds has been studied using biological treatment, adsorption, air stripping, and incineration. Biodegradation of chlorinated compounds is a slow process that is ineffective for extremely low concentrations. Air stripping and adsorption simply trans-... 

Rghei HO, Eiceman GA. 1984. Adsorption and chlorination of dibenzo-p-dioxin and 1-chlorodibenzo-p-dioxin on fly ash from municipal incinerators. Chemosphere 13 421-426. 

Acrolein is destroyed by controlled burning in an incinerator. It is also destroyed by biodegradation after being treated with dilute NaOH or sodium bisulfite solution. Acrolein and other toxic pollutants from industrial laundry wastewater can be removed by treatment involving lime coagulation, carbon adsorption, and ultrafiltration (Van Gils and Pirbazari 1985). 

Filtration Process for Air Quality Management. - Purification of gaseous pollutants is associated with adsorption, absorption and incineration. A new... 

The removal of gaseous pollutants from dryer exhaust may be accomplished by several possible processes. Among these are absorption, adsorption, condensation, and incineration [11-16]. The choice of a given process is usually determined by physical and chemical characteristics of the dried product and by economic and environmental considerations. Table 53.3 summarizes some of the basic characteristics of the gaseous emission control equipment. 

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