Reactor Cracking
Process Description
The process is used for thermal decomposition of CFC/H-CFC/FC-mixtures in a hydrogen/oxygen flame. From the reaction gas hydrofluoric acid of about 55% concentration and hydrochloric acid of about 31% concentration are obtained downstream.
The reactor consists of a reaction chamber connected with a special cooler. The cylindrical reaction chamber is protected by a water-jacketed steel shell. A special burner for hydrogen, oxygen and CFC is flanged to the upper end of the reaction chamber. The material of the reaction chamber is graphite and it has to be protected against overheating. The cooling system used is jacket cooling. The cooler flanged directly to the reaction chamber is also made of acid proof graphite and likewise water-jacketed.
The reaction for R 12 takes place according to following chemical equation:
CCl2F2 + O2 + 2H2 -> CO2 +2 HF + 2 HCl
The CFC's are decomposed into hydrogen fluoride, hydrogen chloride, carbon dioxide, water and some chlorine.
The decomposition products are cooled in the cooler to the extend that aqueous hydrofluoric acid of about 55 % concentration and the non condensable gases can be withdrawn at the cooler outlet.
In the HF-Recovery-Unit the hydrogen fluoride is separated from the non condensable gas mixture and hydrofluoric acid is formed as technical grade quality.The purified gas is than led to the HCl absorption column to recover the hydrogen chloride as hydrochloric acid. This acid is cooled down and pumped to the storage tank.The gas coming from the HCl-absorption is treated in a waste gas scrubber. Any traces of acid are absorbed by water.
The waste gas composition is well within the requirements of the German Clean Air Regulations (TA-Luft). The formation of polychlorinated dioxins and furans is reliably prevented by the high cracking temperatures of over 2000°C and the subsequent rapid cooling of the decomposition products to about 40°C. No solid wastes are produced.