IMPROVEMENTS IN AND WAR Camani, Drona
Year: 1880

page_text: LETTERS PATENT to James Mactear, of Glasgow, in the County of Lanark,
North Britain, Chemist, for an Invention of "IMPROVEMENTS IN AND
WAR
Camani, Drona"
+ !
PROVISIONAL SPECIFICATION left by the said James Mactear at the Office
of the Commissioners of Patents on the 4th November 1880.
JAMES MACTEAR, of Glasgow, in the County of Lanark, North Britain, Chemist.
"IMPROVEMENTS IN AND CONNECTED WITH FURNACES FOR CHEMICAL PROCESSES."
This Invention relates to chemical furnaces partly of the kind described in
the Specification of Letters Patent granted to the present applicant, and dated
28 November 1879 (No. 4870), and it has for its objects to simplify the con- .
struction or formation of the rotating bottoms or hearths of such furnaces, to modify
them so as to render them more advantageously applicable for different chemical,
processes, and generally to improve the accessories with the view of more completely.
and efficiently carrying out the system of a practically continuous action, which is
a distinguishing feature of these furnaces.
By the present Invention the rotating furnace bottom or hearth is by one modi-
fication made with a flat or nearly flat upper surface, and with or without a central
depression or pot or compartment formed by a low circular rib or partition wall to
receive the materials on their first introduction into the furnace from an inlet
arranged at or near a point above the centre of the rotating hearth. Circular or
spiral partition walls between the central part and the outer edge or rim are
dispensed with in this modification.
According to another modification the hearth is made with low partition walls of
a circular or curved form, but with openings or ports, the ports in the several walls
being by preference placed so as not to be in line with each other, but alternately
on opposite sides or at other suitable positions.
Instead of the rotating hearth being flat its surface may be concave, the concavity
being of a conical or conoidal or spherical form, with the central part depressed
below the general contour or encircled by a low partition wall. In some cases the
surface of the rotating hearth may be slightly convex, or it may be formed with
an annular convexity. In a process such as that for making sulphate of soda or

page_text: sulphate of potash in which the materials are partly liquid at the earlier part of
the action, the concave form of the hearth will promote the draining of liquid
towards the centre, and thus prevent insufficiently decomposed or converted materials
from being prematurely discharged at the outer edge of the hearth; and the
annular convexity whilst promoting the return of liquid towards the centre from a
certain distance will also promote the more rapid passage outwards of the materials
when they have reached the top of the convexity.
Apparatus for stirring or turning over or otherwise moving the materials of any
suitable kind in use with chemical furnaces may be employed with the improved
furnaces, but preference is given to the kind described in the earlier Specification
herein before referred to, or a series of scrapers or endless chains may be used, or
there may be a series of stationary but adjustable guides or ploughs, in contact with
which the materials will be continually brought by the rotation of the hearth, such
guides being set at an angle or at different angles so as to cause the materials to
gradually move outwards.
The discharging apparatus or arrangements may be like those described in the
earlier Specification herein before referred to; or at one or more points there may
be a stationary inclined guide or plough arranged to cause the materials to rise
thereon and pass over the rim or outer edge of the hearth into a discharge duct,
dipping down into a receptacle arranged to prevent the escape of gas, or fitted with
a door at the bottom to be opened periodically. Heavy mineral oil or tar or other
suitable liquid not readily acted on by the acid gas may be placed instead of sand in
the lute grooves of the stationary annular discharge channel when that arrange-
ment is employed, and with this arrangement also stationary scrapers may be fixed
so as to prevent the accumulation of crusts on the rim of the rotating hearth.
The improved furnaces are by preference fired with coke or with combustible
furnace gas, and the materials to be furnaced may be fed in by means of apparatus
such as is described in the earlier Specification herein before referred to. Instead
however of employing a pair of reversed cones and a belt for varying the rate of
feed, the motion is transmitted through a pawl lever and ratchet wheel, the lever
being made to reciprocate by a rotating crank or equivalent through an adjustable
connection allowing of the effective length of stroke being altered and adjusted.
In some cases instead of feeding the materials (such, for example, as chloride of
sodium and sulphuric acid) separately into the furnace they may be first mixed
in charges or measured quantities into a separate pot or vessel, from which
after mixing they are gradually transferred to the furnace. There may be two
or more of such preparatory mixing pots in connection with each furnace, so
that the mixed materials may be supplied to the furnace in a sufficiently continuous
manner, fresh charges being prepared in one or more of the pots whilst the contents
of another or others are being transferred to the furnace.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said James Mactear in the Great Seal Patent Office on the 4th May
1881.
JAMES MACTEAR, of Glasgow, in the County of Lanark, North Britain, Chemist.
"IMPROVEMENTS IN AND CONNECTED WITH FURNACES FOR CHEMICAL PROCESSES."
My said Invention relates to chemical furnaces partly of the kind described in
the Specification of Letters Patent granted to me, and dated 28 November 1879
(No. 4870), and it has for its objects to simplify the construction or formation of
the rotating bottoms or hearths of such furnaces, to modify them so as to render
them more advantageously applicable for different chemical processes, and generally
to improve the accessories with the view of more completely and efficiently carrying
out the system of a practically continuous action, which is a distinguishing feature
of these furnaces.
And in order that my present Invention and the manner of performing the
same may be properly understood I hereunto append five Sheets of explanatory
Drawings to be hereinafter referred to, and representing chemical furnaces as made
with my improvements..
The Figures on Sheets 1 to 4 of the accompanying Drawings represent one
modification of my improved furnace as arranged for continuously decomposing
salt, or converting sodium chloride into sulphate of soda, Figure 1 being an
elevation, Figure 2 a plan (with the furnace roof removed), Figure 3 a vertical
section, and Figures 4 to 9 enlarged views of details; Figures 10 to 17 on Sheet 5
of the Drawings are diagrams of various modifications of the furnace bed or hearth.
In these Drawings the same reference numerals are used to mark the same or like
parts wherever they are repeated.
The furnace bed or hearth 21 (Figures 1 to 9), which is of a generally flat form
and circular in plan, is constructed with an iron framework, which is mounted on
wheels 22, and is driven by means of a ring of spur teeth 23, with which there
gears a pinion 24 on a vertical shaft 25. This shaft 25, which serves also to drive the
stirrers, as hereinafter explained, receives its motion through bevil wheels 26 from
a horizontal first-motion shaft 27. At the centre of the hearth 21 there is a
dish 28 having a raised rim, into which dish the materials to be operated on are
first supplied. This dish 28 may be constructed of the firebrick or other suitable
refractory materil of which the general surface of the hearth is formed; or it
may be made of castiron, with or without a refractory lining. A raised rim or
wall 29 extends round the circumference of the hearth, and the hearth is covered
by a brickwork roof 30, carried by an annular iron frame which rests on pillars,
the space between the hearth and roof forming a reverberatory chamber, which is
heated by means of a furnace or pair of furnaces, indicated by dotted lines at 31,
Figure 1, communicated with the chamber by a single flue 32. From the inlet
flue 32 the flames or fire gases pass over the hearth 21 to the opposite side, and
leave the chamber by two outlets 33, a little on each side of a point diametrically
opposite to the inlet flue 32. At the part between the two outlets 33 there is a
framing 34, carrying vertical shafts 35, which have fixed to their lower ends forks
or prongs 36 for stirring the materials on the hearth 21. The stirrer shafts 35 are
geared together by spurwheels 37, and are driven by a spurwheel 38 on the
vertical shaft 25. The framing 34 carrying the stirrers is fitted in a casing 39
inserted in the roof of the furnace chamber, the parts being shown enlarged in
Figure 7, and it can be raised or lowered, having fixed or formed on it racks 40,
with which there gear pinions 41 on a horizontal shaft 42. This pinion shaft 42
has a wormwheel 43 on its outer end, with which there gears a worm on a shaft 44,

page_text: having a squared outer end to receive a crank handle. The stirrers 36 can be
raised through separate openings in the casing 39 for examination, repair, or
renewal, and covers 45 are provided to close the openings, these covers being made
with rims which dip into sand or other suitable luting material, and with boxes
for luting or packing material at the holes, through which the stirrer shafts 35
pass. The driving spurwheel 38 is made with teeth of extra depth to allow of
some vertical adjustment of the stirrer shafts without the wheels getting out of
gear.
The furnace is delineated with feeding apparatus suitable for supplying sodium
chloride and sulphuric acid, but this apparatus may be modified if necessary for
other materials.. The sodium chloride is put into a hopper 46, shown in vertical
section and enlarged in Figure 4, and from the bottom of this hopper a screw
shaft 47 conveys it along a horizontal pipe or duct 48 to a position directly above
the central dish or compartment 28 of the hearth, and it falls thence into the dish
through a duct or casing 49. The sulphuric acid is led continuously at a suitable
rate through a pipe 50 into the casing 49, or into any convenient part of a cover 51
attached to the casing 49, and covering an opening in the roof directly over the
dish 28. The screw feeding shaft 47 is driven in a practically continuous manner,
at a rate which can be varied or adjusted as is in practice found to best suit the
action of the furnace, and for this purpose it has fast on it a ratchet wheel 52
(Figures 5 and 6), which is acted on by a pawl 53 jointed to a lever 54, and to this
lever is connected one end of a rod 55, the other end of which is on a crank pin on
a shaft driven from the vertical shaft 25. The rod 55 is jointed on a block which
can be adjusted inwards or outwards along the lever 54 by means of a screw
spindle 56, and with this arrangement the reciprocating motion imparted to the
lever 54 can be made to turn the screw shaft 47 to a greater or less extent at each
stroke, as may be required. In order to prevent the sodium chloride from hanging
in the hopper 46 there is arranged inside a skeleton or frame 57, consisting of
longitudinal ribs touching or nearly touching the sides of the cone and connected
by rings. This frame 57 is attached to an upper toothed and flanged ring 58,
which rests by its flange upon the top edge or rim of the hopper, whilst its teeth
are in gear with a pinion 59 on a vertical shaft 60 driven by bevil wheels 61 from
the screw shaft 47. By these means the skeleton or frame 57 is kept slowly turning;
and it prevents the materials from adhering to the sides of the hopper and keeps them
in a loose condition such as to insure their descent in a uniform manner as the
screw shaft 47 gradually moves them away from the bottom of the hopper.
The materials gradually overflow from the central dish 28 (being prevented
from adhering to the sides of the dish by a stationary scraper 62), and
they gradually move outwards over the surface of the hearth 21, being thoroughly
and repeatedly stirred by the stirrers 36, under which they are brought over and
over again by the rotation of the hearth 21. The stirrers 36 are represented as
not being wide enough to cover the entire space between them, in consequence of
which there is a tendency to the formation of low annular walls by the materials
themselves, and these quasi walls prevent the materials from working too
rapidly outwards towards the circumference of the hearth. This retarding action
may be made different in different cases by making the stirrers 36 relatively
wider or narrower so as to more or less completely cover or operate upon the space
between the central dish 28 and the circumference.
A number of descending discharge ducts 63 are formed at the circumference of
the hearth 21, close to the rim or wall 29, and beneath these there is a stationary
annular channel 64 to receive the materials as they fall through the ducts or
openings 63. The ducts 63 communicate with or have attached to them an
annular piece 65, shaped like an inverted channel, and which forms a cover to the
stationary channel 64, its sides dipping down into lute grooves 66 formed upon
the sides of the stationary channel 64. Portions of the materials enter the lute
grooves 66; or sand or other suitable luting materials may be put therein so as to
prevent the entrance of air into the furnace, or the egress of gases or vapors

page_text: therefrom.
The stationary channel 64 has fixed in connection with it one or
more hopper-shaped discharge boxes 67 (Figure 1), fitted with bottom doors or
valves for periodically emptying the sulphate or other materials into trucks or
other receptacles. The outer rim 29 of the hearth 21 is beneath an annular
plate or frame 68, which is made up of separate pieces bound by a wrought iron
hoop, and is supported on pillars 69, and which supports or partly supports the
roof 30; and this plate 68 is formed with a cylindrical flange, which has fixed to
it a sheet iron band 70 dipping down into an annular channel 71 fixed to the
revolving hearth and having placed in it suitable luting materials to prevent
ingress or egress of air, or gas, or vapor.
In some modifications the hearth is made with a flat or nearly flat upper surface,
as shown in Figures 10 to 14, and without any central depression or pot as in
Figure 10, or with a central depression as in Figure 11, or with a pot or central
compartment 28, formed by a low circular rib or partition wall, as shown in
Figures 12 to 14, to receive the materials on their first introduction into the
furnace from an inlet arranged at or near a point above the centre of the rotating
hearth. Circular or spiral partition walls between the central part and the outer
edge or rim 29 are dispensed with in the modifications shown in Figures 10, 11, 12;
but in another modification, shown in plan and in section in Figures 13 and 14,
there are low partition walls 72, 73, 74, of a circular or curved form, made
however with ports 75, the ports in the several walls being by preference placed as
shown and not in line with each other.
Instead of the rotating hearth being flat its surface may be concave, as shown in
Figure 15, the concavity being of a conical, or conoidal, or spherical form, with the
central part depressed below the general contour, or encircled by a low partition
wall. In some cases the surface of the rotating hearth may be slightly convex, as
shown in Figure 16, or it may be formed with an annular convexity, as shown in
Figure 17. In a process such as that for making sulphate of soda or sulphate of
potash, in which the materials are partly liquid at the earlier part of the action, the
concave form of the hearth will promote the draining of liquid towards the centre,
and thus prevent insufficiently decomposed or converted materials from being
prematurely discharged at the outer edge of the hearth; and the annular convexity,
whilst promoting the return of liquid towards the centre from a certain distance,
will also promote the more rapid passage outwards of the materials when they
have reached the top of the convexity.
Apparatus for stirring or turning over, or otherwise moving the materials, of any
suitable kind in use with chemical furnaces may be employed with my improved
furnaces, but I prefer the kind hereinbefore described; or a series of scrapers on
endless chains may be used; or there may be a series of stationary but adjustable
guides or ploughs, in contact with which the materials will be continually brought
by the rotation of the hearth, such guides being set at an angle or at different
angles, so as to cause the materials to gradually move outwards.
Instead of the discharging apparatus or arrangements hereinbefore described,
there may be at one point, or at each of two or more points, a stationary inclined
guide or plough arranged to cause the materials to rise thereon, and pass over the
rim or outer edge 29 of the hearth into a discharge duct dipping down into a
receptacle arranged to prevent the escape of gas, or fitted with a door at the
bottom to be opened periodically. Heavy mineral oil, or tar, or other suitable
liquid not readily acted on by the acid gas may be placed instead of sand in the
lute grooves 66 of the stationary annular discharge channel 64, when that
arrangement is employed; and with this arrangement also stationary scrapers may
be fixed so as to prevent the accumulation of crusts on the rim 29 of the rotating
hearth. A set of such stationary scrapers is shown as fitted at 76 in Figure 2,
and they are shown enlarged in face view and side view in Figures 8 and 9. The
set of scrapers consists of four rods 77 held in guides against the vertical face of a
bracket 78, and passing down through a box or casing provided with a cover 79.
These rods 77 can move independently of each other, their upper parts being

page_text: The
formed with slots, into which project pins fixed into the bracket 78 to prevent the
rods from descending too far, whilst allowing them to rise over small obstructions,
which action is also facilitated by their bottom ends being bevilled.
scrapers 77 serve to dislodge inaterials from the parts of the hearth 21 between
the discharge openings 63.
My improved furnaces may be fired by means of any suitable fuel, but I prefer
to employ coke, or to fire them by means of combustible furnace gas, such as is
formed in what are known as " gas producers."
In some cases instead of feeding the materials (such, for example, as sodium
chloride and sulphuric acid) separately into the furnace, they may be first mixed in
charges or measured quantities into a separate pot or vessel, from which after
mixing they are, gradually transferred to the furnace. There may be two or more
of such preparatory mixing pots in connection with each furnace, so that the mixed
materials may be supplied to the furnace in a sufficiently continuous manner, fresh
charges being prepared in one or more of the pots whilst the contents of another or
others are being transferred to the furnace.
Having thus particularly described my said Invention and the manner of
performing the same, I have to state that I do not restrict myself to the precise
details herein described or delineated, but that what I believe to be novel and
original, and claim as the Invention secured to me by and in terms of the
herein before in part recited Letters Patent is,-
1. The combination of parts constituting my improved furnace and accessories
for chemical processes, herein before described with reference to Figures 1 to 9 of the
accompanying Drawings.
2. The combination of parts constituting the improved feeding apparatus
hereinbefore described.
3. The combination of a uniformly flat rotating hearth, such as is shown in
Figure 10 of the accompanying Drawings, with feeding, discharging, and other
accessories adapted for practically continuous action, substantially in the manner
herein before described.
4. The making of the surface of the rotating hearth in any of the forms shown
in Figures 11 to 17 of the accompanying Drawings.
5. The modification of continuous discharge apparatus, consisting of one or more
stationary inclined guides or ploughs arranged to lead the materials over the rim of
the rotating hearth, as herein before described.
6. The combination with the furnace of one or more preparation pots in which
the materials are mixed in separate charges, and from which the mixed materials
are transferred to the furnace in a practically continuous manner, as hereinbefore
described.
In witness whereof, I, the said James Mactear, have hereunto set my hand
and seal, this Twentieth day of April, in the year of our Lord One
thousand eight hundred and eighty one.
Witness,
EDMUND HUNT,
Patent Agent,
Glasgow.
JAMES MACTEAR. (L.S.)