224





RECORD AND GUIDE





January 31, 1914





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BUILDING MANAGEMENT

SOFT COAL FOR HEATING IS ECONOMICAL, EFFICIENT
AND   PRACTICABLE   WITH    SMOKELESS   BOILERS.

By J. F. MUSSELMAN, M. E.

Consulting Engineer.





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m              Conducted by Raymond P. Roberts, Building Manager for the American Real Estate Co.

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WHEN consideration is given to the
fact that for every one thousand
cubic feet of contents of the average
New York office building, loft or apart¬
ment house, somewhere between ¥1 and
$2.50 is spent per year for the coal
burned in the heating apparatus, it is
easy to realize what a large per cent
in the operating cost of any enterprise
goes to the coal bill. With this in mind,
it is difficult to understand why, in de¬
signing the heating systems of buildings,
so little attention is given to the selec¬
tion of the boilers and the determination
of the character of coal to be used. This
is especially remarkable in view of the
fact .that it can be demonstrated that
this item of coal cost is subject to a
variation of at least 40 per cent., which
variation can be traced directly to cor¬
rect or faulty boiler selection or to the
use of right or wrong kind of coal.

A mistake of this kind, once made, is
rarely corrected, for few owners know
what their coal cost really is, and even
fewer can make an accurate estimate of
what it should be. Then this question
of coal cost is apt to come up in mid¬
winter, which is the worst possible time
to think seriously about a change in the
boiler plant. But a boiler that will save
40 per cent, of the coal cost will pay
for itself in from two and one-half to
three years.
Wide Variation in Coal and Its Cost.

So little attention has been given to
the selection of boilers in many of the
present-day buildings that the matter has
generally resolved itself into a condition
by which the boiler of the best sales¬
man or the cheapest manufacturer is
used. This again has brought about the
widest possible variation in the kind and
size of coal used, until it is not uncom¬
mon to see the best grade of stove or
egg coal, which costs on an average $6.25
per ton, used in one building, while an
adjoining building of the same kind is
using No. 1 buckwheat at 13.50 per ton.

The cheapest anthracite coal that can
be used readily under the natural draught
conditions which obtain in the usual
building are pea size, costing in the New
York market an average of about $4.75
per ton, and No. 1 buckwheat, costing
about $3.50. The former has a heat
value   of   about   12,000   British   thermal





units per pound, while the latter runs
in the neighborhood of 11,500 British
thermal units per pound. These twq
sizes are the ones in most general use.

Merits of Soft Coal.

According to the reports of the U. S
Bureau of Mines, there is to be found
in the coal fields of Pennsylvania, Mary¬
land and West Virginia bituminous and
semi-bituminous coal in almost unlim¬
ited quantities. This coal is usually
mined, I am told, on a royalty basis of
ten cents per ton, and the freight is suffi¬
ciently low to allow it to sell in the Mew
York market at $3.75 per ton or less.
These soft coals of the Eastern fields
have very high heating values per pound
and are correspondingly low in ash.
Their average heating value of "run-
of-mine" size is about 14,100 British
thermal units per pound, and, inasmuch
as they are coking, very little fuel is lost
through the grate.

The primary objection to soft coal is
of course, the fact that it smokes, and
we often hear the statement- that the
smoke ordinances of New York will not
permit its use. But this statement is
not correct, and we must consider that
a great many cities which have smoke
ordinances fully as strict as those ot
New York have no hard coal available
at prices not prohibitive.

The importance of abatement of the
smoke nuisance is so manifest and the
economy which could be effected by the
use of this extensive supply of soft coal
so apparent that the U. S. Geological
Survey has authorized an exhaustive in¬
vestigation and test on plants of various
kinds in which soft coal is used. A
report of these tests by Messrs. D. T.
Randall and H. W. Weeks is issued by
the Department of Mines, Bulletin No.
40. The plants which were tested were
equipped with different kinds of stokers,
dutch ovens, down-draft furnaces and
ordinary flat grates. A brief summary
of the conclusions reached states that
smoke prevention is both possible and
economical, and that there are maiiy
types of furnaces and stokers that will
burn soft coal economically without
smoke.

For an ordinary low-pressure heating
plant which is not in conjunction with a
power plant, a mechanical stoker is toe





complicated and too expensive to be
generally used. As it is the purpose of
this article to deal with the conditions
of less expensive and smaller buildings
where isolated plants are not warranted,
the relative merits of mechanical stokers
will not be taken up.

A successful boiler for this kind of
building must be inexpensive, economi¬
cal, smokeless and simple to operate. It
should have a large firebox in order tha^
a considerable quantity of fuel can be
fired at one time, for it is often incon¬
venient, especially in the smaller installa¬
tions, to attend the fire oftener than once
every two hours. It is most important,
too, that such a boiler should have a
large steam space and should be con¬
structed in such a way as to eliminate
as nearly as possible the chance of unex¬
pected breakdown, which might make
the whole system inoperative.
Burns Soft Coal with Almost No Smoke.

This last heating season has intro¬
duced into New York a type of boiler
that accomplishes all of these require¬
ments admirably. It consumes the soft
coal so perfectly that almost no smoke
is visible at the chimney, and at the
same time shows a boiler efficiency aver¬
aging about 2() per cent, higher than the
usual type of heating boiler. The boiler
referred to consists of an adaptation of
the well-known Hawley down-draft fur¬
nace principle to a firebox or portable
steel boiler. It consists of an upper
grate made of heavy steel water tubes,
built into the furnace and extending from
the inside head-sheet to a cross header
running from one side-sheet to the other.
Below this is a lower grate of the usual
rocking pattern that burns only such
half-consumed fuel as falls through from
the upper grate.

In the operation of this type of boiler
all of the green coal is charged on the
water grate, and through this upper fire-
door the greater part of the air is ad¬
mitted, forming a draught down through
the green coal and carrying its smoke
through.the live fire and into the large
combustion chamber where it is entirely
consumed by the heat^ of the lower
fire which is fed by the coked live coals
which fall between the wide openings
of the water grate. The combustion
chamber back of upper grate is large
and high, giving the smoke a low veloc-











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