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Thermal industrial processes go green

In the light of evidence of their extreme toxicity to human health and the environment, the discharge of heavy metals from industrial processes has become a question of considerable public and scientific concern. The difficulty in developing appropriate techniques for controlling the polluting effects of heavy metals coming from the incineration or any thermal industrial process consists of their highly complicated behaviours throughout the process. An EC funded project developed a new model and approach that is capable of describing the physical properties of all heavy metal-related compounds found in the successive stages of the incineration process, along with the effect of the operational parameters and methods on their behaviour.

Industrial Technologies

The fate of heavy metals in the environment largely depends on its form. When fossil fuels or trash burn, the contained heavy metals may evaporate as gases, some of which may oxidise in the flue gases that disperse in the atmosphere and contaminate air over large regions. Another potential route into the environment is fly and bottom ash that are often disposed of on land and may leach heavy particles to close waterways. Practically every industry discharges heavy metals into the environment. The primary anthropogenic source for the emission of heavy metals, such as lead, zinc, copper, in the environment is the incineration as well as any thermal industrial processes. The developed MELODI tool includes a comprehensive database containing detailed information on each compound and particularly the heavy metals found in every step of the process along with its physical state and properties. This information is of vital importance for identifying the potential leaching activity of the material and additionally for developing the profiles of the compound's distribution between the various residues. Moreover, the used approach can also provide valuable information of the effects of the operating parameters on the heavy metals behaviour. Thereby, depending on the waste composition, the suitable operation conditions and methods, such as high temperature filtration, can be identified for optimum control of heavy metals. Most importantly, the tool may also be useful for performing risk management concerning possible leaks. With the aid of MELODI, it has also been proven that heavy metals recovered from fly ashes may be used in road construction. Currently, incineration has a high profile resulting from public concern over potential emissions of pollutants that led to strict new legislative controls introduced by the European Commission. The MELODI approach offers new means for the chemical and process engineering research into incineration and combustion for the management of residues of heavy metals and can be exploited in many possible applications involving heavy metals' hazards in the materials produced by thermal processes.

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