Published November 1978
Electrolysis of sodium chloride to produce chlorine can be achieved by the diaphragm process, the mercury process, and the recently commercialized membrane process. Cost evaluations in this report show that when solid salt is the raw material, the mercury process is the most economical. If the raw material is brine, the diaphragm process gives the lowest product value (production cost plus a 25% pretax return on investment), but the diaphragm process only slightly surpasses the mercury process, if one takes into account the premium value of the caustic soda produced by the latter process. The membrane process is not competitive with either of the other two processes unless the dilute caustic soda from the cells can be used captively. The above statement relates to a plant with a capacity of 1,000 short tons of chlorine per day. A capacity larger than this favors the diaphragm process; a smaller capacity shifts the advantage to the mercury process and the membrane process.
Coproduction of sodium carbonate instead of caustic soda is generally less economical. Conversion of hydrogen chloride to chlorine can be more economically achieved by the Rel-Chlor process using nitric acid/sulfuric acid oxidation than by electrolysis, except in plants having a very small capacity.
Other PEP Related Reports:
