A Practical Manual On Sea Water Distillation
With A Description Of The Necessary Machinery For The Process
Forfatter: Frank Normandy
År: 1909
Forlag: Charles Griffen & Co., LTD.
Sted: London
Sider: 244
UDK: 663.6
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THE EVAPORATOR.
IOI
yield by large evaporators for the same time ; therefore,
a minimum should be adopted before the proportion is
worked out.
To facilitate the understanding of this subject, suppose
the diameters of two evaporators have to be deter-
mined, one for generating steam at the hourly rate
of 1,000 lbs., the other of 20 lbs. Assume that the area
at the brine level is 400 square inches, which would make
the diameter of the shell 22| inches. By the rule of pro-
portion 1,000 : 20 :: 400 : 8. The diameter of a shell with
an area of 8 square inches would be barely 3| inches, an
absurd dimension for an evaporator. A minimum
diameter should be fixed, so that the ratio would
cause the small evaporator to be of a suitable
diameter.
(6) Material of Casing.
74. Undoubtedly the best material is gun-metal—that
is, an alloy of copper and tin—the proportion of tin being
between 10 and 12 per cent., and that of zinc 2 per cent,
or less. This is Admiralty quality, and evaporator
casings, especially the lower part containing the sea
water, should be made of it. The steam-room is some-
times made of iron or steel galvanised, as also are the base
and cover, but it is best for the entire evaporator to be
made of gun-metal, as the. corrosion is very great. When
iron or steel is used it must be extra thick, in order to
allow for the wear that sets in very quickly. Under
these circumstances steel or iron casings become heavy
and expensive, and are, then, not nearly so reliable as
gun-metal. The upper part or steam-room may be made
of copper, if preferred. It may be mentioned that quite
small evaporators may be made of galvanised cast iron.