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

MULTIPLE DISTILLATION. i85 distillation the coal consumed would be in ratio of 24'4 of water to 1 of coal. Therefore, if in 1,000 hours’ working the actual production of water was 500,000 gallons of water= 2,237 tons (500,0004-224=2,237), then the coal consumed in producing the 2,237 tons of water would be as follows :— 1.237 -r 18 = 124 tons (about) of coal (in double distillation). 1.238 4- 24'4 = 92 tons (nearly) of coal (in treble distillation) ; So that a saving of about 32 tons of coal (124- 92=32), about 25 per cent., would be obtained in producing 2,237 tons of water if treble distillation apparatus is used instead of double distillation apparatus. 27. By this method of calculation the actual saving by the use of any type of apparatus can be ascertained, and it will then be possible to judge how far the extension of multiple distillation can be carried advantageously for practical purposes. Diminishing Economy. 28. The economy (or amount of fuel saved by the process of multiplying evaporators) is greatest in double distillation stage, in the first evaporator—i.e., the first evaporator is the most effective—while the effectiveness of any evaporator beyond the fourth is scarcely re- munerative, when the increased cost of the apparatus is taken into account. Note.— Sometimes the boiler, instead of being fed with the same impure water that is in process of distillation, is fed with distilled water—i.e., the primary water—or