The downsides of high temperature plasma disposal

For the temperatures at which the waste can be converted into a plasma (over 6,000°C), implementing the reactor design is a complicated task, at least the situation is not likely to change in the foreseeable future. Thus, the conditions of reliable operation of the reactor temperature process using a plasma heating should be in the range of from 900 to 1,200°C. This temperature level is well maintained in many other well-known and already mature technologies, which are based on pyrolysis and gasification processes. However, as the years of operating experience pass, all of these technologies hasn’t achieved the traditional burning of solid waste in terms of the technical and economic indicators.

Environmental benefits of plants with plasma technology compared with incineration, including addressing the problem of dioxin, are actual for the large productions. First of all it should be noted that almost all modern MSW incinerators are provided with the regulated emissions of harmful substances in flue gases, which if necessary may be significantly optimised.

Reduced levels of dioxins to standard values is performed in two stages using methods and scrubbing process. This also applies to installations using plasma torches. Despite the high temperature (above 1,200 – 1,300 ° C, and in some cases up to 1,600°C) at which reportedly (according to supporters plasma method) another dioxins synthesis generally does not occur at all sites with plasma torches and mounted equipment for the removal of dioxins. In the comparative tables, powered by analytical materials, it is mostly often indicated that the quantity of dioxin emissions is lower than those provided for by Directive 2000/76/EC of the European Parliament and the Council of Waste Incineration, meaning the presence of dioxins in the flue gases is yet attaching. Therefore, we can say that the burning of the resulting synthesis gas dioxins occur and additional cleaning of flue gases for normal values is required.

As for the decision of the general scrubbing of the synthesis gas produced by gasification of MSW using plasma heating, it is a relatively new issue, and thus its cleaning circuit is rather complicated. Thus, for example, the technology of Simdean, an expert in plasma waste disposal and industrial waste disposal solutions manufacturing, syngas passes successively through scrubber, a spray tower, wet electrostatic filter with activated carbon and fed to desulphurisation, and selective catalytic reduction of nitrogen oxides. Further, in some technologies quenching gas is used, which essence lies in the fact that the hot synthesis gas exits the reactor at about 1200°C, and then cooled in a water tube heat exchanger to about 200°C. It should be noted that in this case, there are serious doubts concerning the application of normally used in such cases tubular heat exchanger. Moreover, the operation in general of any heat exchanger at the dust-laden gas with a temperature of 1,200°C is questionable. The synthesis gas contains fusible particles that can intoxicated the heat exchange surface completely.

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