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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70
SEA WATER DISTILLATION.
10. Economy is, therefore, a totally different matter
from the evaporative power of an evaporator as against
time, which we have just been considering with regard
to the amount of heating surface required. Although
large evaporators are naturally rather more economical
than small ones, as relatively less heat is wasted, the
primary steam required for a large production of secondary
steam, or a small one, is proportionately the same. Thus,
if it takes, say, 12 lbs. of primary steam to obtain 1 lb.
of secondary steam (irrespective of the time taken in the
operation), it will take 1*2 tons of primary steam to pro-
duce 1 ton of secondary steam, no matter what may be
the amount of heating surface in operation, provided the
type of apparatus and all the other conditions of working
are kept to.
Note.—In specifying the economy of multiple distilling
machinery, where the proportion of distilled water to
coal consumption is specified, it is usual to state the
economy as being so many lbs. (or tons) of water per
1 lb. (or ton) of coal.
11. Thus, take the three cases before referred to, and
first take the case where the primary pressure is at 10 lbs.
per square inch. Every lb. of the Ij tons of feed-water
will have to be heated from, say, 100° to 212°, and then
f of the 1| tons (i.e., 1 ton) will have to be converted
into steam. This will, therefore, require heat as follows :—
168 units of sensible heat to heat up the feed-water
(212 - 100 X = 168).
966 units of latent heat for evaporation.
1,134 B.T.U. (total) to be found (per lb. evaporated).