Crystec Technology Trading GmbH

Gas cleaning by thermal decomposition of toxic components followed by wet scrubbing has proven effective. In most cases SemiAn uses an electric heater for these burner-washer systems. The advantages are low susceptibility to faults and high operational safety of the burner.

Chlorofluorocarbons (CFCs) such as trichlorofluoromethane CCl₃F, dichlorodifluoromethane CCl₂F₂, chlorodifluoromethane CHCl₂F, trichlorotrifluoroethane CClF₂-CCl₂F, dichlorotetrafluoroethane CClF₂-CClF₂ (to name a few), as well as hydrofluorocarbons (HFCs) such as carbon tetrafluoride CF₄ or hexafluoroethane C₂F₆ and other inert fluorides like sulfur hexafluoride SF₆ are very stable, inert and therefore non-toxic to humans. However, it has been shown that these compounds damage the Earth's ozone layer and thus contribute significantly to global warming. Therefore, the use of these substances has been heavily restricted. For processes where the use of CFCs, HFCs or SF₆ is necessary, these substances must be removed from the exhaust gas. Due to the high stability of chlorofluorocarbons, however, an electric burner that can reach temperatures up to approx. 1000°C is no longer sufficient. Plasma burners are used, which can crack CFCs due to their high temperatures and high reactivity.
An ionized gas (plasma) is a gas in which the energy of individual atoms is so high that electrons are detached from the nucleus. Positive ions and free electrons exist side by side and plasma is therefore electrically conductive. High voltage is used to create an electron discharge between two electrodes that generates an arc. Pressurized air flowing through produces a plasma flame which has very high internal temperatures, is chemically very reactive and is therefore well suited for cracking even inert compounds.
When CFCs, HFCs or SF₆ are cracked in the presence of air or oxygen, carbon dioxide CO₂ as well as hydrogen fluoride HF, fluorine F₂, hydrogen chloride HCl and chlorine Cl₂ are formed. All of these compounds are water-soluble and can be removed from the exhaust gas by a downstream scrubber, which can optionally be equipped with neutralization. The water is circulated via a storage tank which can optionally be cooled. Residual moisture after this step is removed in a dryer.