Three sizes of boiler have been tested thus far, the dimensions being as
given in Table 4.
Each of the three boilers was tested at several temperatures of entering
air, up to 1,500° Fahr., about ten tests being made at each temperature.
It is also the intention to run, on these three boilers, about eight
tests at temperatures of 1,800°, 2,100° and 2,400° Fahr., respectively.
A bulletin on the work already done, together with much incidental
matter, is in course of preparation.[18]
TABLE 4.--Dimensions of Boilers Nos. 1, 2, and 3.
------------------------------------+--------+--------+--------
Items. | Boiler | Boiler | Boiler
| No. 1. | No. 2. | No. 3.
------------------------------------+--------+--------+--------
Distance, outside to outside of | | |
boiler heads, in inches | 8.28 | 8.28 | 16.125
Actual outside diameter of flues, | 0.252 | 0.313 | 0.252
in inches | | |
Actual inside diameter of flues, | 0.175 | 0.230 | 0.175
in inches | | |
Number of flues (tubes) | 10 | 10 | 10
------------------------------------+--------+--------+--------
The work on the first three boilers is only a beginning; preparations
are being made to test eight more multi-tubular boilers of various
lengths and tube diameters, under similar conditions. Because of the
experience already obtained, it will be necessary to make only eight
tests at each initial air temperature.
When the work on multi-tubular boilers is completed, water-tube boilers
will be taken up, for which a fairly complete outline has been prepared.
This second or water-tube portion of the investigation is really of the
greater scientific and commercial interest, but the multi-tubular
boilers were investigated first because the mathematical treatment is
much simpler.
_Producer-Gas Tests._--The producer-gas plant at the Pittsburg testing
station is in charge of Mr. Carl D. Smith, and has been installed for
the purpose of testing low-grade fuel, bone coal, roof coal, mine
refuse, and such material as is usually considered of little value, or
even worthless for power purposes. The gas engine, gas producer,
economizer, wet scrubber (Fig. 1, Plate XIX), and accessories, are in
Building No. 13, and the dry scrubber, gas-holder, and water-cooling
apparatus are immediately outside that building (Fig. 2, Plate XIX).
At present immense quantities of fuel are left at the mines, in the form
of culm and slack, which, in quality, are much below the average output.
Such fuel is considered of little or no value, chiefly because there is
no apparatus in general use which can burn it to good advantage. The
heat value of this fuel is often from 50 to 75% of that of the fuel
marketed, and if not utilized, represents an immense waste of natural
resources. Large quantities of low-grade fuel are also left in the
mines, simply because present conditions do not warrant its extraction,
and it is left in such a way that it will be very difficult, if not
practically impossible, for future generations to take out such fuel
when it will be at a premium. Again, there are large deposits of
low-grade coal in regions far remote from the sources of the present
fuel supply, but where its successful and economic utilization would be
a boon to the community and a material advantage to the country at
large. The great importance of the successful utilization of low-grade
fuel is obvious. Until within very recent years little had been
accomplished along these lines, and there was little hope of ever being
able to use these fuels successfully.
The development of the gas producer for the utilization of ordinary
fuels,[19] however, indicates that the successful utilization of
practically all low-grade fuel is well within the range of possibility.
It is notable that, although all producer-gas tests at the Government
testing stations, at St. Louis and Norfolk, were made in a type of
producer[20] designed primarily for a good grade of anthracite coal, the
fuels tested included a wide range of bituminous coals and lignites, and
even peat and bone coal, and that, in nearly every test, little serious
difficulty was encountered in maintaining satisfactory operating
conditions.[21] It is interesting to note that in one test, a bone coal
containing more than 45% of ash was easily handled in the producer, and
that practically full load was maintained for the regulation test period
of 50 hours.[22]
It is not expected that all the fuels tested will prove to be of
immediate commercial value, but it is hoped that much light will be
thrown on this important problem.
[Illustration: PLATE XX.
Fig. 1.--Charging Floor of Gas Producer.