The Hawaiian gazette., 1885-12-08

EDITOR GAzErIE-ln your issue of Nov. oath.
noticed, summary Of the experiments made at
! hohala tor the purpose of ascertaining which is
the best method, maceratiOn or dry grinding, in
the roller mill. In these experiments 1t is seen
that dry grinding Is credited with 1861 per cent
and wetting, or maceratiou, 1852 per cent. This
| shOwes difference OF nearly per cent IN favor
of maceratlon, and Is a gain of lSl2O lbs yalued
| at $500. To the amount of water used in this
maceratlon trial 3O62S gallons or sos 80 lbs
to evaporate this amount of water it is stated ii
would require 165570 lbs of coal or to quote from
the report: The Theoretical power of h. of coal
Is lbs. of water, but notice that the author be-
fore me for safety IN his estimates gives credit for
| only lbs of water 20 10 of coal" The sos 80
| lbs OF water added IN this maceration at Kohala
would require to evapOrate At 165 $40 lbs of coal
which at S2J.OO per ton would amount to sos. 20
which deducted from the S906 proceeds of the lS-
lO lbs OF sugar leaves the gain to be credited to
maceratlon Sl4OSO. This large amount of coal
I655lO lbs required for the evaporation of sos $50
lbs of water Is evidently mistake in printing If
should read $3.50 lbs of coal which would bring
the rest OF the calculation out correctly but even
TINS amount Is far too much, TO assume that one
pound of coal will only evapOrate lbs Of water is
to make all the approved methods of evapor alton
| count for nothing.
| 1t must be evident to any one. that in the sew
eral methods of evaporation there must be differ
ent results for instance the best of steam boiler
Will evaporate 10 lbs Of water per 10 of coal the
reason why this steam when transferred TO AN open
pan will not evaporate more then lbs is difficult
| to account for.
Suppose we take ID of steam, Csteam pres
sure 20 lbs we find it contains l2ll of heat the
pound of water sesulting from the condensation
OF this 10 OF steam dontains Do Fab and would
be loss of III per cent were 1t not returned to
the boiler but this water is usually returned TO the
boiler at temperature of 2l0 Fahrenheit SO there
is not much loss there, from radiation, and con-
densation, there is some loss but not enough 10
berng 1t down from 10 10 1, from NV experience i
should say II Is quite safe TO put Il at lbs: if il
Will not do this IN an open pan 1t will certainly do
in he first Of 4 I,f,,
hrst pan Of a double effect will eyaporate 6 lbs of
water per 10, of coal, the vapor from this will do
almost as much ID the scond. as the live steam did
IN the rst, 9l9 per cent which is equal 20 liz
lbs OF water per 10 Of coal. While the vapor from
the hrst, and second pan of triple effect will eva
Porate nearly one and three quarters times as
nuch as the live steam IN the first pan OF 1868
per cent. From this We see that the double effect
well evaporate ll4 lbs of water per 10 OF coal and
the triple effect nearly l6 lbs of water per III of
coal. The sos, 80 lbs of water would require but
25624 lbs of coal If II were all evaporated in a
double effect, and only 1912 lbs if it were eva
Porated in triple effect.
They are many things which effect the evapora-
tive efficiency of coal first II will ALWAYS be least
as the pressure Is increased and greater as the
pressuse Is decreased: for this reason il will al
ways be more effective IN a vacuum pan then in
an open pan, while double effect well increase its
value 9l.9 per cent and triple effect 1868 per
cent. 80 far from 1t requiring ID of coal to
eyaporate lbs of water IN this apparatus find
by experiment that ID of trash will eyaporate
81 lbs of water, lbs in the first pam the vapor
from this VIII evaporate ia ID in the scond pam
the yapor from this will evapOrate "a lbs in the
third.
There are very few person that realize the great
amount of work or heat energy contained in a
pound OF coal. For instance a pound of good
coal contains 1850 British thermal units of heat
this multiplied by ~ the mechanical equivalent of
heat 1I2Il2r rJO0=96J0,O00 foot pounds and so the
actual amount Of WORK done by this pound of coal
IS equal lifting 96JO0OO pounds one foot high and
If all this heat was absorbed by the water in the
boiler, II would eyapOrate nearly thirteen pounds
of wafer per pound of coal. GRO OsBoRSF
Laurahoehoe, Hawaii, Dec l4th. 1885.