Waste high temperature techniques

The most important current technique for the thermal destmction of waste is incineration, where the energy required for destmction is provided by oxidation of the waste, sometimes supplemented with a fossil fuel. The major question about all thermal destmction techniques is whether products from the process—either traces of umeacted parent compound or compounds synthesized from the parent compound at high temperature— will pose a health hazard. 

Direct injection is the most commonly used technique for sample introduction in GC, typically using combined spht/splitless injectors. In split mode, a portion of the sample passes onto the column and the rest is directed to waste. After sufficient split time to completely flush the injector the split vent may be closed to save gas, although this is optional. The injector is set to a sufficiently high temperature to eliminate discrimination between analytes. The sensitivity of the technique is inversely proportional to the split ratio. 

Waste-Form Stability. If they occur at all, solid state transformations in dry glass and UO2 matrices will be too slow under the temperature conditions of service to be observable in the laboratory at the same temperature. Here we need to extrapolate from high temperature laboratory conditions to low temperature service conditions. It will be desirable to develop an intimate knowledge of the processes of phase separation and devitrification of sodium borosilicate glasses at temperatures below the softening point by meticulous application of electron microscopic. X-ray crystallographic and other techniques. The glasses will contain inactive elements representative of the fission product... 

Sulfur chemistry is important both in combustion and in the petrochemical industry. Most fossil fuels contain sulfur, and also biofuels and household waste have a sulfur content. As a consequence sulfur species are often present in combustion processes. Knowledge of gas-phase sulfur chemistry occurring in combustion has bearing on pollutant emissions and on system corrosion. Air pollution by SO2 still constitutes a major environmental concern and search for control techniques has motivated research also on high-temperature homogeneous sulfur chemistry. However, more recent work on sulfur chemistry has been concerned mainly with the effect of sulfur on other pollutant emissions, such as NO and CO, and with the SO3/SO2 ratio, which is important for the corrosive potential of the flue gas and for formation of sulfur containing aerosols. 

The question of when to use which technique always calls for a case-by-case decision, but the methods must fulfil the basic requirements, they must be environmentally sound, safe and economical. While all other methods touched upon here are feasible in theory, the most appropriate is incineration in special high temperature incinerators (HTI). Suitable waste disposal facilities are only found in small number in industrialised countries. 

Since its foundation the Department of Chemical Engineering and Industrial Chemistry of the V.U.B. acquired considerable experi-eice in the field of high temperature processes, -with studies on steam-reforming of natural gas, pyrolysis of hydrocarbons and catalytic combustion of hydrocarbons. The Department conducted fundamental studies as well as contract work for industry, e.g. in the domain of fluidized bed techniques, incinerator grate mechanisms and small waste-fed boilers. An assessment on current thermal disposal techniques was prepared on behalf of E.E.C.[ 5 57958] ... 

Off-gas purification. As a high-temperature process, any type of vitrification process will have to have a very effective off-gas cleaning system. In fact, besides the remote operation and maintenance technique, off-gas treatment will be among the most important waste-processing problems to be solved. The off-gas may contain volatile fission products, such as ruthenium and cesium, as well as aerosols and dust. Multistage systems will be required with wet and dry cleaning procedures to obtain an off-gas sufficiently clean for release to the atmosphere. 

Applications of the technique include municipal and hazardous waste incinerators, small to medium sized industrial burners and brick kilns. The injection system used is similar to that for the high temperature injection process [29.1]. 

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