EVAPORATION OF APPLES 927 
sary to supply the requisite heat. Sev- 
eral kilns, however, which are said to 
work admirably, have about 650 running 
feet of pipe for every 100 square feet of 
floor space. One-half of this is “riser,” 
the other half “return.” 
In the type of evaporator referred to as 
“cabinet evaporators,” the length of one 
inch steam pipe required per square foot 
of surface directly exposed to the pipes 
is considerably less than in the case of 
the kiln just described, although it is 
probable that in the system in question 
a greater degree of heat can be main- 
tained than with the usual piping for a 
kiln. As previously mentioned, in this 
system the pipes are arranged in hori- 
zontal tiers, the racks on which the fruit 
is placed being inserted between them. 
Hence, the upper racks receive more or 
less heat from the lower tiers, as well 
as from those to which they are directly 
exposed. In one evaporator of this type, 
which gives excellent satisfaction, and in 
which the drying compartments are 
about nine feet square—that is, large 
enough to hold four four-foot racks (two 
square) in the same plane—there are 
thirty-two one-inch pipes in each tier. 
Hach pipe is about 814 feet in length, or 
approximately 270 feet in each tier. In 
the evaporator referred to there are eight 
tiers in each compartment. Hight racks— 
two deep—are placed between each tier 
of pipes. 
In another evaporator of this type, hav- 
ing a capacity of 400 bushels every twen- 
ty-four hours, a 40-horsepower boiler, 
with about 15 square feet of grate sur- 
face, furnishes the necessary steam when 
run at a pressure of 40 to 50 pounds 
This is sufficient for drying the fruit and 
for running the parers, slicers, elevators, 
etc., required to handle this quantity of 
fruit. The steam pressure at which such 
systems are run varies considerably ac- 
cording to the individual requirements of 
the systems. A range of from 40 to 90 
pounds has been noted in different evap- 
orators. 
Fuel 
Where the owner of an evaporator has 
an abundant supply of wood and it can 
be cut at times of leisure, this is probably 
the least expensive fuel in actual cash 
outlay that can be had in most of the 
apple-growing sections. In fact, under 
these conditions, it is commonly esti- 
mated that the fuel costs nothing. But in 
a great number of cases fuel has to be 
bought, even by operators who are drying 
apples from their own orchards. 
For kiln evaporators using the common 
type of furnaces, hard coal is probably 
the most satisfactory fuel, and requires 
less attention than any other. Coke is 
sometimes used, and if it were as satis- 
factory as coal, other things being equal, 
it would be the cheaper fuel. But it re- 
quires much attention, and even with the 
best of care it is difficult to maintain 
a uniform degree of heat. A combination 
of coal and coke is sometimes used with 
satisfactory results, in which case the 
faults and advantages of one tend, in a 
measure, to equalize those of the other. 
In a steam-heated plant soft coal serves 
the purpose in a satisfactory way, and 
in most apple-growing sections is prob- 
ably cheaper than any other fuel that is 
readily available. 
Quantity of Fuel Required 
While the amount of fuel necessary to 
dry a given quantity of fruit will vary 
more or less, depending upon the condi- 
tions of the weather, the efficiency of the 
furnace, the construction of the kiln, the 
percentage of moisture to be left in the 
fruit, and various other things, it is 
roughly estimated that a ton of hard 
coal, for a kiln evaporator, will make a 
ton of dried fruit. Probably the average 
requirement is rather more than this. 
It is claimed that a tower evaporator re- 
quires slightly less for the same results. 
Open grates also considerably reduce the 
amount of fuel necessary for a given 
quantity of fruit, but on account of their 
objectionable features they can not be 
used for the better grades of apples. 
Coke is rather more efficient, 2,600 to 
2,700 pounds of apples being evaporated, 
it is claimed, by a ton of fuel. 
A good steam system should require 
considerably less than a ton of soft coal 
