Kel-Chlor Flow Sheet Article for Chemical Engineering
Publication Date: 2012-Sep-15
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Page 01 of 8
MAKES CHLORINE FROM HYDROGEN CHLORIDE
The Theme: 4HC1 + 02 ~ 2 Cl2 + 2 H20.
Deacon commercialized this reaction for conversion of hydrogen chloride to chlorine in the 1870's using air and a copper chloride catalyst at 650-750°F. Limited to about 75% conversion by the equilibrium a~d plagued by corrosion problems and high energy consumption, the process has been discarded. Other attempts to oxidize HCl directly to chlorine were similarly unsuccessful.
In 1969 the M. W. Kellogg Co. (now Pullman Kellogg) announced its Kel-Chlor process, in which oxygen reacts with
HCl aided by nitrogen oxide catalysts in a circulating stream
of sulfuric acid. Developed through a series of pilot plants
and in collaboration with E.I. duPont de Nemours & Co.,
efforts culminated in the first commercialization of the Kel-Chlor process in duPont's Corpus Christi, Texas facilities with a Kel-Chlor unit designed to produce 600 tons per day of liquid chlorine. The Kel-Chlor unit has been operating successfully, without process problems, since May 1974 as an integral part
of the total facility, feeding on HCl off-gas from the produc- tion units and recycling chlorine. Easy and quick to start up
and shut down, the Kel-Chlor unit has demonstrated its inherent operational stability by producing specification product
chlorine at a variety of production rates.
Kel-Chlor is Deacon up-to-date. In Ke1-Chlor the highly exothermic reaction finishes at 250-350°F and the water of reaction is removed by the circulating ~ulfuric acid to so favor the equilibrium that conversions as high as 99.5% are normal in the commercial plant. Corrosion problems have been solved with available materials. Energy requirements are a small fraction of other processes for conversion of HCl to chlorine.
Page 02 of 8
In the flow diagram HC1 feed gas enters the stripper and countercurrently contacts hot aqueous (about 80% H2504) sulfuric acid that contains water of reaction and the catalyst, which here is present mainly as nitrosylsulfuric acid, and strips the cata- lyst into the gas phase by the reaction:
HNSO5 + HCI~NOCl + HzSO4
The Oxygen feed gas then countercurrently removes any dissolved HCl from the acid and the acid stream leaves the stripper carry- ing the water of reaction with only traces of HNSO5.
Strlp~er off gas, composed of NOC], HCl and.oxygen, enters the oxidizer and is heated by mixing with partly-oxidized gas to the operating temperature ~t which the following reactions are self-sustaining:
2NOCl ~ 2NO + Cl2 (2)
2NO + 02 ÷ 2 NO2
Excess heat from the highly exothermic oxidation reactions is removed by exchange to an external steam generator so that the reactions will proceed to the desired conversion. The generated steam powers the ejectors in the sulfuric acid vacuum flash system and provides all needed process heat.
When the oxidizer off gas, depleted in HCI and oxygen, is countercurrently contacted in the absorber by the circulating sulfuric acid stream, the reve...