Process of and Apparatus for Utilizing Producer Gas as Fuel for Calcining Limestone.
Year: 1894

page_text: Date of Application, 30th Jan., 1894-Accepted, 17th Mar., 1:94
Process of and Apparatus for Utilizing Producer Gas as Fuel
for Calcining Limestone.
A communication from WILLIAM A. KONEMAN, Mining Engineer, of the Masonic
Building, and AZEL F. HATCH, Lawyer, of 100, Washington Street, both
of the City of Chicago, County of Cook, State of Illinois, United States
of America.
I, ALFRED JULIUS BOULT of 323 High Holborn in the County of Middlesex,
Chartered Patent Agent, do hereby declare the nature of this invention and in
what manner the same is to be performed to be particularly described and
ascertained in and by the following statement :-
Producer-gas, or gas of low calorific power, by reason of its cheapness, is a very
desirable fuel for use in calcining limestone to produce lime, provided it can be
caused by combustion to generate sufficient heat at the proper point in the kiln.
The point referred to is that of "sticking" the kiln, a term employed to express
the wedging of the limestone between the kiln-walls by its expansion under the
influence of the generated heat, which must be very intense to effect it. This
sticking point should be at the base of the column of limestone, since lime is not
properly burnt unless with an adequate degree of heat for sticking it; hence it
follows that unless the sticking of the kiln be produced at the base of the columu
of limestone, it will take place higher up in the column, according to the point
therein at which complete combustion of the fuel, in rising through it, takes place,
with the undesirable consequences that the mass of stone below that point is
insufficiently burnt, affording a poor or even worthless product, and that great
difficulty is incurred, owing to the comparative inaccessibility of the sticking poiut,
in dislodging the calcined inass to effect precipitation thereof.
To render producer gas, which is inherently low in calorific power, suitable for
the purpose, it is introduced according to this invention simultaneously into opposite
sides of the kiln and burnt near the desired sticking point or base of the limestone
column therein, and air forcibly introduced with the gas, under a blast pressure,
but in a horizontal plane above that of the gas-introduction. Thus are accomplished
three important requirements for the successful burning: First, the gas and air,
being forced under considerable pressure horizontally into the kiln and against the
interposed stratum of limestone, become intimately mixed and reduced to a
condition for thorough combustion of the fuel and generation of the requisitely
great heat, at the desired sticking point at the base of the column of limestone;
second, by forcibly introducing the air in a plane over that of the gas-introduction,
the gas is held down near its said plane the longer, thereby the more effectually
preventing its rise, before reduction to a condition of thorough combustion, in the
limestone column; and, third, the forcible intermixture of the gas and air by the
air-blast (or, if desired, by forcing in the gas with a blast instead of the air)
prevents the draft through the open top of the kiln from producing objectionable
“wall-climbing
"of the products of combustion-so conimon in lime-kilns and
which causes irregular burning of the limestone,-and insures forcible distribution
of the hot products of combustion in rising through the entire mass of the column
and their escape at the top in a thoroughly spent condition.
The improved apparatus is illustrated in the accompanying drawing by a view
in sectional elevation.
A is a lime-kiln involving any suitable or well-known general construction. At
a desired height above the base of the kiln, through the wall thereof, are openings B
divided by diaphragms q into gas-inlets r and air-inlets p, which should unite

page_text: at the inner ends of the diaphragms, which extend short of the inner surface of
the kiln-chamber and form mixing and combustion chambers o. An air-supply
leads into the kiln near its base, tuyeres n being shown as the medium for the
supply.
C is a gas-supply pipe, leading from a generator or other supply (not shown)
of producer gas, or cheap gas of low calorific power, and having branches m
leading into the openings r; and D is an air-pipe having branches leading into
the openings p, the pipe D communicating with a fan E. If desired the air-supply
to the tuyeres n may be from the fan E, by connecting them with the pipe D;
though a separate fan for the tuyeres may be provided, and thereby avoid provision
of pressure-reducing means, which may be otherwise required in the communication
of the tuyeres with the pipe D.
To understand the operation, it is to be presumed that the base, or draw-pit,
of the kiln A is filled up to the dotted line x, with the finished product of a
burning in a highly heated condition, and which has been precipitated into the pit.
From the line the kiln is filled with limestone to be burnt. The fan E being set
in motion, air is forced under pressure into the kiln through the openings p; and,
the supply of gas from the pipe C, admitted to the openings r, and ignited in the
kiln, is drawn in with considerable force. The gas and air commingle in the
mixing-chambers o; and the pressure at which they are introduced overcomes
their tendency to stratify and rise separately and causes them to combine so
intimately in the kiln about where they are introduced therein, as to induce
thorough combustion of the fuel near the point of its introduction, whereby all, or
practically all, the heat of complete combustion is expended on the material above
the line, in passing through it, and only the thoroughly spent products of com-
bustion escape from the top, whereby there is the minimum of waste and the
greatest heat is imparted by the products of combustion to that portion of the
limestone which lies in the plane of the combustion-chambers o. Meantime air,
under more or less pressure, is introduced through the openings represented by
tuyeres n through the pile of hot lime in the pit, being thereby thoroughly heated;
and it commingles with the fuel from the openings B, and enhances the combustion
thereof.
When the burning is finished, the fuel-supply should be turned off, and the contents
of the pit are withdrawn through the opening k to enable the newly burnt product
to be precipitated and form the bed for the next burning. The kiln will be found
to have been "stuck," as aforesaid, forming an arch, represented by the line, at
the proper point, and requiring the burnt mass to be dislodged for precipitation;
for which purpose it is common to insert probing-bars into the kiln through suitable
openings, one of which is represented at x1, and to be provided with means for
closing it, as usual. Then the kiln is ready for another burning operation; and the
proceeding is carried on as described.
The product of this improved treatment is of excellent quality, being uniformly
burnt throughout the kiln, of a high degree of whiteness, and exceptionally free
from grout; and moreover the cheap quality of gas which is rendered serviceable
by the provision for forcing its complete combustion at the base of the material
to be burnt in the kiln, renders the treatment exceptionally economical and
inexpensive.
The limitations with regard to introducing the gas into the kiln through the
walls and the air in a plane above the gas-introduction, are not indispensable; hence
this invention is not limited thereto.
Having now particularly described and ascertained the nature of the said inven-
tion & in what manner the same is to be performed, as communicated to me by
my foreign correspondent, I declare that what I claim is :-
1. The process of utilizing producer-gas as fuel for calcining limestone, which
consists in forcing the gas into and burning it in the kilu in the base of the column
of limestone to be converted, and simultaneously forcing air under blast-pressure

page_text: into the kiln and base-portion of the column of limestone, thereby forcibly inter-
mixing the introduced gas and air and producing thorough combustion of the fuel
and sticking" of the kiln near the said base and causing the products of
combustion to pass upward through and permeate the entire mass of the limestone
column and escape in a thoroughly spent condition freely from the top, substantially
as described.
2. The process of utilizing producer-gas as fuel for calcining limestone, which
consists in forcing the gas into a kiln at opposite sides thereof and burning it in
the kiln in the base of the column of limestone to be converted, and simultaneously
forcing air under blast-pressure into the kiln and base-portion of the column of lime-
stone at opposite sides thereof above the plane of introduction of the gas, thereby
forcibly intermixing the introduced gas and air and producing thorough combustion
of the fuel and "sticking of the kiln near the said base and causing the products
of combustion to pass upward through and permeate the entire mass of the lime-
stone-column and escape in a thoroughly spent condition freely from the top,
substantially as described.
"
3. In combination, a line-kiln A having a draw-pit and uncovered at its upper
end, openings B in opposite sides of the kiln near the sticking point therein
and divided into upper air-inlet passages p and lower gas-inlet passages, a gas-
supply pipe C leading into the passages r, an air-supply pipe D leading into the
passages p, and a blast-fan E communicating with the said air-pipe, substantially
as and for the purpose set forth.
Dated this 30th day of January 1804
W. P. THOMPSON & BOULT,
Agents for the Applicant.