Saline Water Conversion by Freezing HERBERT F. WIEGANDT
SALINE WATER CONVERSION Downloaded from pubs.acs.org by UNIV OF NEW SOUTH WALES on 09/05/15. For personal use only.
Cornell University, Ithaca, N. Y.
Favorable energy relationships and a convenient refrigeration cycle make freezing look attractive. Movement of a crystal bed by hydraulic forces combines adequate production with a simple wash ing procedure.
Investigations at Cornell University are based on process concepts i n which an ice slurry is produced from saline water b y evaporation of a suitable immiscible refrigerant. After washing, the ice crystals are melted b y direct condensation on the ice of the compressed refrigerant vapors. Potable water is the product, and the immiscible refrigerant re cycles to the process. η-Butane and isobutane are the preferred economical refrigerants which allow the process to operate close to atmospheric pressures and thereby allow use of large-volume process equipment. Experimentally much use has been made of methylene chloride as a convenient refrigerant.
Energy Requirements Although the minimum energy needed for the conversion of saline water to fresh water is the same for any isentropic process, the goal is to achieve this conversion efficiently i n a real process, on a large scale, at low cost, and with easily maintained equipment. T h e minimum work theoretically required at a specified salinity and temperature may be equated b y a number of alternatives: —Wrev = reversible work in B.t.u. per pound of product s=
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