A Practical Manual On Sea Water Distillation
With A Description Of The Necessary Machinery For The Process

I 74 SEA WATER DISTILLATION. 8. For a production up to, say, 10 tons of water per day (24 hours) the double distillation type will probably be sufficient (except in cases where the price of fuel is very high). For productions above 10 tons and up to, say, 50 tons daily, the treble distillation would be suitable. The simplicity of only three successive distillations will, how- ever, often induce one to carry the installation of treble distilling apparatus up to 80 or even 100 tons of water daily. For productions over the above requirements, quadruple, quintuple, or even higher grades of multiple distillation may be suggested. Multiple distillation can- not, however, be continued with advantage to an un- limited extent. 9. It will be seen shortly that after carrying multiple distillation to a certain point, the increased gain of water becomes so small, the boiler so large, and the initial pressure so high, that the addition of more evaporators cannot be usefully continued. Gained Water. 10. The term “gained” water is usually applied to the distilled water obtained by the evaporation of sea water by means of an evaporator (on board ship) to distinguish it from the greasy fresh water (condensed boiler steam) used by the evaporator—i.e., the primary steam when it is re-converted into primary water by the abstraction of its latent heat. Such primary water has to be kept separate from the gained water, in order to be returned to the boiler for re-evaporation. 11. In the double distiller on a steam ship the primary steam, being always greasy, is only used as an initial