Year: 1887

page_text: Date of Application, 21st July, 1887
Complete Left, 19th May, 1888
MOJSK Complete Accepted, 22nd June, 1888
We, H. C. BULL & COMPANY, Limited and HENRY CLAY BULL, Engineer, both
of 31 Poultry, London do hereby declare the nature of the said invention to be
as follows:-
This Invention has for its object to arrange and construct and work calcining ovens
in such a manner that the supply of calcined material therefrom may be more
continuous than heretofore that is the time between the discharges of calcined material
may be diminished.
To the above ends we provide calcining ovens with double moveable grates arranged
one over the other and so constructed that the upper one can be forced into the charge
resting upon the lower grate (say at a quarter the height up the charge in the oven)
and the lower one then may be opened or withdrawn thereby allowing all the material
below the upper grate to fall and be taken away. This portion of the charge will be
fully calcined whilst the portion of the material now resting upon the upper grate
will be only partially calcined. When the finished material is removed the lower
grate is replaced in position and the upper one withdrawn, thereby allowing the
material remaining in the oven to fall onto the lower grate. Fresh material is then
fed to the oven.
As an example of construction of a calcining oven it may be made of cylindrical
form with a portion of the bottom square and is lined with fire brick, or other suitable
material. It is provided with a pair of doors at the bottom, capable of being withdrawn,
or dropped. It also has a swinging grating which can be forced across its centre
say about a quarter of its height from the bottom-and a cup and bell on the top
similar to those used on blast furnaces for charging. The swinging grate may enter
the calcining oven through a water jacketted casting. The draught may be
maintained by a steam jet in the chimney which has its outlet from the calcining
oven immediately under the bell and cup. Gas and air are admitted from each side
through burners similar to Bunsen burners. When calcining metallic ore and
limestone for say a blast furnace, it is filled with these materials and gas and air are

page_text: admitted until a portion of the material is properly' calcined when the grid is forced
in on each side to the centre, thus supporting the upper part of the material. The
bottom doors are then dropped and about a quarter of the contents is emptied into
the charging device of the furnace. The bottom doors are then closed, the grid
withdrawn allowing the contents of the calcining oven to drop to the bottom. A
suitable quantity of fresh material is then charged in at the top the gas and air are
again admitted at the bottom and the calcining proceeded with. Two, or more of
these calcining ovens may be used and may be mounted on wheels so that one, or
one set can be cool for repairs while the other is in operation, and in the case
of a blast furnace, may be placed immediately over the cup and bell of the reducing
shaft.
The calcining oven above described is applicable for general calcining purposes,
such as for calcining limestone and other analogous purposes and uses.

page_text: We, H. C. BULL AND COMPANY, Limited, and HENRY CLAY BULL, Engineer,
both of 31 Poultry, London, do hereby declare the nature of the said invention and
in what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement:-
This Invention has for its object, to arrange and construct and work calcining ovens.
in such a manner that the supply of calcined material therefrom may be more
continuous than heretofore, that is the time usually taken between successive discharges
of calcined material, shall be diminished.
To the above ends we provide calcining ovens with double moveable grates, arranged
one over the other and so constructed that the upper one can be forced into the charge
resting upon the lower grate (say at a quarter the height up the charge in the.
oven) and the lower one then may be opened or withdrawn thereby allowing all
the material below the upper grate to fall and be taken away. This portion of the
charge will be fully calcined, whilst the portion of the material now resting upon the
upper grate will be only partially calcined. When the finished material removed,
the lower grate is replaced in position and the upper one withdrawn, thereby allowing
the material remaining in the oven to fall onto the lower grate. Fresh material is
then fed to the oven.
That this Invention may be clearly and exactly understood, there is hereto annexed
a Sheet of Drawings illustrative of an example of calcining oven according to this
Invention. This Sheet of Drawings forms a part of this Specification, the views
thereon being marked with figures and letters of reference, corresponding with those
used in the following explanation of them. Like letters and figures are used to denote
like parts throughout the views.
The Drawings and the description of this Invention herein contained are together
sufficient to enable others skilled in the art to which this Invention belongs, or is most
nearly connected to put the same into practice.
DESCRIPTION OF THE DRAWINGS.
Figure 1 is a sectional elevation of the calcining oven according to this
Invention.
Figure 2 is a front view of the oven shown at Figure 1.
Figure 3 is a plan of the oven in section taken through the line x x Figure 1.
Figure 4 is a plan of the oven projected from Figure 2.
Figures 5 and 6 are respectively a section and plan of one of the bars of the
swinging crate in detail. and

page_text: The
body consists of a casing A of refractory fire brick bound by iron straps a..
swinging grate consists of two sets of hollow bars 6 secured to hollow cross heads 6',
which are supported by suspended tubes 62. These tubes are mounted and worked
in bearings mounted upon the top of the oven. The bars of the grate are
placed in the oven as shown and are inserted, or withdrawn from it through
apertures d, formed in a cast metal annular box or casing D. Both the casing D
and the bars bare maintained in a comparatively cool state by water, which is
admitted to circulated through them in the following manner: Water is supplied to
the pipes of both grates by a pipe (not shown in the Drawings) in any convenient
way. These pipes 62 communicate with the outer portion, 63 of the crossheads b
which are divided by diaphragms & into two compartments. The water flows from
the chamber through the pipes 6, one of which is provided for each of the bars
and extends from the diaphragm 6 to near the end of the bar. Thus water on leaving
the pipes 65 strikes the interior surface of the bars b and flows back to the second
chamber of the crosshead b¹ from whence it is taken by one of the pipes 62 upon
the side opposite to the inlet side of each grate and is led away.
Water is conveyed to the casing D (which is hollow) by a pipe and is led
from it by another pipe in the ordinary way: these pipes not being shown in the
Drawings.
A second water lined hollow casing E having apertures e¹ is placed at the bottom
of the oven.
This is provided for three purposes, one of which is to support the
brickwork between itself and the casing D, the second is to form a seat for the
grate F, and the third is to provide a means of keeping the air and gas tuyeres e,
which are inserted through the apertures e¹, cool. The grate F is a solid one as shown.
It is hinged at f and is kept closed by any suitable kind of catch or bolt.
The tuyeres e are of the well known Bunsen type, by which the air and gas are
supplied in the required proportions. The motor for supplying the gas and air consists
of a steam jet exhauster of the "Korting" type, placed within the funnel G of the
stove; thus they are introduced and drawn through the tuyeres e and the burden of
material in the oven by creating a partial vacuum within the oven above the charge.
The oven is charged with material through the cup and bell device H and opening
and closing lever I, which are of the ordinary blast furnace type. The whole of the
structure is supported by columns J, having brackets i, upon which the casing E
rests and other brackets g formed upon the casing D are also provided to take a
part of the weight of the oven. These rest upon the capitals of the columns J.
The mechanism employed for operating the swinging grates is shown at Figures 7
and 8 and consists essentially of toothed racks k, which are secured and hinged to the
cross heads 6 and worked by a toothed pinion wheel, (not shown) which lies between
the upper and lower racks k. The pinion is mounted on a spindle on which the
cross turning lever k³ is fixed and by turning this lever one way or the other the cross
heads will be either drawn together or pushed apart. The racks k are kept together
by the box frame k³ in which they slide. This frame k³ is secured in position by the
spindle k¹, whose end is mounted in a bearing plate k*.
The operation of calcining by the oven is carried on as follows:-Let it be assumed
that metallic ore and limestone are the substances that are to be calcined, for use in a
blast furnace; then to start the operation the swinging grate bars b are withdrawn
(the grate F being closed) and the material is fed to the oven through the bell
mouth H in the usual way until it reaches say a point just below the funnel aperture.
The charging bell is then closed and the steam exhauster in the funnel is started,
thereby causing an exhaustion of the air from the oven and an indraught of air and
gas which is turned on and ignited.
The process of calcination now proceeds and it is continued for a sufficient period
of time; the length of this time will depend upon the quality of the materials under
treatment, and the amount of calcination required. The portion nearest the tuyeres
will of course be prepared first and when that portion of the charge which lies
between the tuyeres and the casing D is sufficiently, calcined, namely about one
quarter of the charge-the bars & of the swinging grate are forced into the charge

page_text: and take the position as shown in the Drawings; the lower grate F is then opened
and drops, or swings down upon its hinges f, thereby allowing the calcined material
below the grate bars 6 to fall from the oven.
After this portion of the material is discharged the grate F is closed, the grate
bars bare withdrawn and the remainder of the charge within the oven falls to the
bottom. Fresh material is then supplied to the oven to take the place of that
discharged and the process and operations just described may be repeated and
continued.
In calcining material for blast furnace operations two of the ovens may be used and
arranged above the furnace mouth. They are in this case preferably mounted upon
wheels, one of the two could be used for calcining and placed directly over the
charging hopper of the blast furnace and the other would be wheeled to one side out
of the way for repairing. Thus the two ovens would be used alternately; one being
in operation and the other out.
It must be understood that the oven herein described is applicable for calcining
processes analogous or equivalent to that employed in the preparation of limestone
and metalliferous ores.
Having now described this Invention what is claimed is:-
:-
1. In a calcining oven of the type herein described, a grate, interposed between
the upper portion of the oven and the grate proper, operating as, or substantially as
set forth for the purposes specified.
2. A calcining oven consisting of a vertical chamber formed by a wall A, charging
mouth H a swinging grate constructed as described, a water casing D, a hinged
grate F, tuyeres e, a water casing E, and supports J, all substantially as set forth
with reference to the Drawings and operating as described for the purposes
specified.
3. The swinging grate consisting of members 62 crosshead 6' and water lined
bars 6 constructed and operating as, or substantially as set forth for the purposes
specified with reference to the Drawings.