Scrubber with plasma burner and washer for cracking of CFC, HFC, SF6.
SemiAn Technology is represented in Europe by
Exhaust gas cleaning by thermal combustion of toxic components and following washing of the exhaust gas is proven technology. In most cases, SemiAn is using for this burner-washer-scrubber an electrically heated burner. The advantages are low susceptibility and high reliability of the burner.
Chlorofluorocarbons CFCs like trichlorofluoromethane CCl3F,
(to name just a few examples), and hydrofluorocarbons HFCs like carbon tetrafluoride CF4
or hexafluoroethane C2F6 and other
inert fluorides such as sulfurhexafluoride SF6 are very stable,
inert compounds and therefore non-toxic to humans. It has been shown though that these compounds damage the ozone layer
of the earth, and thus contribute significantly to global warming.
Hence the use of these compounds has been severely limited. For processes in which the use of
CFCs, HFCs and SF6 is necessary, these compounds must be removed from the exhaust gas by a scrubber.
Because of the great stability of chlorofluorocarbon CFC substances, an electric burner which can achieve
temperatures up to 1000įC is not sufficient. Plasma torches are used then, which can crack the CFCs by
high temperature and high reactivity.
A plasma is a gas, in which the energy of the atoms is so high, that the electrons are separated from the nucleus and plasma is therefore electrically conductive. By high voltage an electric arc is generated between two electrodes. A flow of compressed air generates a plasma flame with a very high internal temperature, which is chemically very reactive and can therefore crack also inert compounds.
When CFC, HFC or SF6 react with air or oxygen, beside carbon dioxide also hydrogenfluoride HF, fluorine F2, hydrogenchloride HCl and chlorine Cl2 are generated. All of these compounds are water soluble and can be removed from the exhaust gas by a wet scrubber, which can be equipped as an option with a neutralization unit. The water is circulated through a circulation tank with an optional cooling unit. Finally residual moisture is removed by a demister.
The plasma scrubber design is differing little from the normal burner-scrubber models SBW. All main parts are made of stainless steel, the reactor itself is made of Inconel and the circulation pump is Teflon-coated. The process control is done by PLC control, heater power detection system, SRC heater power control and visualization achieved by a TFT monitor. As an option, a central, PC based monitoring system is available. Several scrubbers can be connected to this system. The status of all scrubbers can be displayed there. Improved safety functions, various interlocks and water leak detection systems are installed. The footprint of the system is small and total equipment is designed in order to work at lowest cost. The size of the scrubber is available for a gas flow in the range of 100 - 1.200 slm or 6 - 72 m3/h.
The described plasma torch is supplied the company of ATU, Korea and can be ordered also separately for other applications where high temperature is required.