Incineration thermal

In incineration, gaseous organic-vapor emissions are converted to carbon dioxide and water through combustion. There are two types of thermal incinerator, based on heat recovery employed, regenerative and recuperative. 

Thermal incinerators depend upon contact between the contaminant and the high-temperature combustion flame to oxidize the pollutants. The incinerator, generally consists of refractory-lined chamber, one or more burners, a temperature-control system, and heat-recovery equipment. 

Contaminated gases are collected by a capture system and delivered to the preheater inlet, where they are heated by indirect contact with the hot incinerator exhaust. Gases are mixed thoroughly with the burner flame in the upstream portion of the unit, and then passed through the combustion zone, where combustion process is completed. An efficient thermal incinerator design must provide  

The residence times forincinerators are on the order ofO.5 to 1 seconds, at a temperature ranging from 1200°F to 1600°F. Destruction efficiencies in excess of 95% can be commonly achieved. 

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Design considerations and costs of the catalyst, hardware, and a fume control system are direcdy proportional to the oven exhaust volume. The size of the catalyst bed often ranges from 1.0 m at 0°C and 101 kPa per 1000 m /min of exhaust, to 2 m for 1000 m /min of exhaust. Catalyst performance at a number of can plant installations has been enhanced by proper maintenance. Annual analytical measurements show reduction of solvent hydrocarbons to be in excess of 90% for 3—6 years, the equivalent of 12,000 to 30,000 operating hours. When propane was the only available fuel, the catalyst cost was recovered by fuel savings (vs thermal incineration prior to the catalyst retrofit) in two to three months. In numerous cases the fuel savings paid for the catalyst in 6 to 12 months. 

Combustion-Control Equipment Combustion-control equipment can be divided into three types (1) flares, (2) thermal incinerators, (3) catalytic incinerators. 

Catalytic Incinerators Catalytic incinerators are an alternative to thermal incinerators. For simple reactions, the effect of the presence of a catalyst is to (1) increase the rate of the reaction, (2) permit the reaction to occur at a lower temperature, and (3) reduce the reactor volume. 

Lower fuel requirements as compared with thermal incinerators... 

Thermal incinerators (gas-fired afterburners or catalytic afterburners) None... 

Lower and upper explosive limits (LEL, UEL) must be considered in order TO avoid dangerous operation in the incinerators. Thermal incinerators are normally designed to operate with concentrations below 2.5% of the LEI, lypically, the LEL ranges from 2500 to 10 000 ppmv. ... 

When a mixture of compounds is to be treated, more limitations may be placed upon the selection of a suitable abatement method. There may be several compounds in the waste gas, some being unsuitable to one method, while others are unsuitable to another method. In such cases, thermal incineration may be the best solution. When recovering mixtures, additional separation equipment may be needed for recycling the reclaimed compounds. 

Many compounds can cause problems in pollutant-control equipment. Particulate matter, liquids, or solids in the waste stream can plug the adsorber beds, heat-recovery beds in regenerative thermal incinerator systems and biofilters. Conventional filtration systems are used to remove particulate matter before or after the process. 

The advantages of thermal incineration are that it is simple in concept, has a wide application, and results in almost complete destruction of pollutants with no liquid or solid residue. Thermal incineration provides an opportunity for heat recovery and has low maintenance requirements and low capital cost. Thermal incineration units for small or moderate exhaust streams are generally compact and light. Such units can be installed on a roof when the plant area is limited. = The main disadvantage is the auxiliary fuel cost, which is partly offset with an efficient heat-recovery system. The formation of nitric oxides during the combustion processes must be reduced by control of excess air temperature, fuel supply, and combustion air distribution at the burner inlet, The formation of thermal NO increases dramatically above 980 Table 13.10)... 

In catalytic incineration, organic contaminants are oxidized to carbon dioxide and water. A catalyst is used to initiate the combustion reaction, which occurs at a lower temperature than in thermal incineration. Catalytic incineration uses less fuel than the thermal method. Many commercial systems have removal efficiencies eater than 98%. 

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... 

Incineration is an estabhshed process for virtually complete destruction of organic compounds. It can oxidize solid, liquid, or gaseous combustible wastes to carbon dioxide, water, and ash. In the pesticide industry, thermal incinerators are used to destroy wastes containing compounds such as hydrocarbons (e.g., toluene), chlorinated hydrocarbons (e.g., carbon tetrachloride). 

TABLE 1 Estimated Treatment Costs in Dollars per Pound for Trichloroethylene (TCE), Trichloroethane (TCA), and Carbon Tetrachloride (CCL4) Using Timable Hybrid Plasma, Thermal Incineration, Catalytic Oxidation, and Granular Activated Carbon"... 

Once an undesirable material is created, the most widely used approach to exhaust emission control is the application of add-on control devices (6). For organic vapors, these devices can be one of two types, combustion or capture. Applicable combustion devices include thermal incinerators (qv), ie, rotary kilns, liquid injection combusters, fixed hearths, and fluidized-bed combustors catalytic oxidization devices flares or boilers/process heaters. Primary applicable capture devices include condensers, adsorbers, and absorbers, although such techniques as precipitation and membrane filtration are finding increased application. A comparison of the primary control alternatives is shown in Table 1 (see also Absorption Adsorption Membrane technology). 

The advantage of electro over thermal incineration is that no noxious materials are added to the environment. It seems likely that rubbish disposal in general will become electrochemical. Low-temperature (-250 °C) molten salt processes may be necessary for tougher cases (Lin, 1997). Low current density Cl2 evolution may be introduced as a biocide when necessary, particularly in treatment of aqueous electrolytic sewage involving urine (Kaba, 1990 Tennakoon, 1993). 

Recognize that a viable economic approach to recycling is by thermal incineration reclamation of electrical energy. Since there is unlimited raw material sources (vegetation, etc.) to produce plastics, the incineration approach can eliminate the problems associated with reusing recycled plastics.3 211... 

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