THE KEL-CHLOR PROCESS-CONVERSION OF HCl TO CHLORINE
Publication Date: 2012-Sep-06
The IP.com Prior Art Database
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THE KEL-CHLOR PROCESS - CONVERSION OF HCI TO CHLORINE
The M.W. Kellogg Co. first disclosed its Kel-Chlor process in 1969I. This process converts hydrogen chloride (HCI) to chlorine by oxidation with oxygen through a chemical route involving nitrogen
oxide compounds in a circulating sulfuric acid system. After develop- ing the process in conjunction with the E.I. du Pont de Nemours & Co., Inc., in a series of pilot plants in Kellogg's and Du Pont's facilities Du Pont erected a large (600-900 TPD) fac~llty in Corpus Christi, Texas (Figure l). This plant has been operating successfullysince spring 1974 treating the age-old problem of by-product HCI. A full discussion of the process is therefore indicated.
The gain obtained by the Kel-Chlor process, can be best understood by starting with the Deacon reaction:
4 HCI + 02 ++ ,2 Cl2 + 2 H20 ...................................... If]
This process was catalyzed with catalyst containing copper chloride,
which become active at the relatively high temperatures of 650-750°F. At these temperatures equilibrium limitations allow conversion only to about 75%.
In the Kel-Chlor process a complex chemistry is used in the presence of sulfuric acid, which permits finishing the reaction at a much lower temperature of about 250-350°F. Not only is the equilibrium of the ex- othermic reaction'is much more favorable at this lower temperature
but the sulfuric acid removes the water of reaction, so that conversions of 99.5% become possible and have been demonstrated over
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long operating periods.
.Figure 2 gives a simplified process arrangement to convert gaseous HCI to gaseous chlorine of reasonable purity. The process can also take in aqueous HCl, but gaseous HCl is the simplest case.
Basically, four steps are employed in the conversion of HCl to gaseous chlorine: recycle-acid stripping of catalyst, catalytic con- version in the oxidizer, absorption of the catalyst and finishing off
of the conversion,~finally followed by flashing of the recycling acid to remove the Water of reaction.
The important and governing characteristic of the process is the presence of a large recycle of sulfuric acid, which not only serves to keep the nitrogen oxide type catalyst locked in the system, but also removes the water of reaction and also most of the heat of reaction.
RecycZe-acid stripping - In this operation gaseous feed HCI contacts, countercurrently, a hot aqueous sulfuric acid stream of about 80% concen- tration, which contains the water of reaction and catalyst, taken up in
the absorber. The catalyst, mainly present in the form of nitrosylsulfuric acid, is stripped from the acid by the reaction:
.HNSO5 + HCl ÷÷ NOCl + H2SO4 ..................................... [21
In the next lower section of the stripper, oxygen is introduced to
strip out the small amount of HCl, which has gone into solution. The acid stream leaves the stripper carrying the water of reaction and only traces of HNSO5.