IMPROVEMENTS IN FURNACES AND APPARATUS CONNECTED THEREWITH FOR EVAPORATING AND INCINERATING ALKALINE LYES, AND FOR RECLAIMING THE SODA OR OTHER ALKALIS THEREFROM
Year: 1881

page_text: PROVISIONAL SPECIFICATION left by William Malcolm at the Office of the
Commissioners of Patents on the 2nd November 1881.
WILLIAM MALCOLM, of Kevock Paper Mills, Lasswade, in the County of
Midlothian, North Britain. "IMPROVEMENTS IN FURNACES AND APPARATUS
CONNECTED THEREWITH FOR EVAPORATING AND INCINERATING ALKALINE LYES,
AND FOR RECLAIMING THE SODA OR OTHER ALKALIS THEREFROM."
This Invention relates to certain improvements in furnaces and apparatus
connected therewith to be employed foror in the processes of evaporating and incin-
erating alkaline lyes, such as have been used in paper manufacture, for the purpose
of reclaiming the soda or other alkalis therefrom; and the object of the Invention is
to dispense with hand labour, and to substitute therefore mechanical means and
appliances for treating the material operated on in such furnaces which shall be
capable of acting more effectually and with a great saving in time, fuel, and labour.
The first part of the Invention has reference to the roasting furnace or roaster
for evaporating and incinerating the lyes, and which consists of a large brick
oven, on the floor of which the lye is run from the evaporating pans wherein it has
been previously partially treated. A heating furnace is formed at one end, and the
flame therefrom passes over a bridge, and is deflected by the roof or crown, as in
ordinary reverberatory furnaces to strike or play on the surface of the lye material
from end to end of the oven or furnace. The action of the fire or flame on the
surface of the lye very soon forms a hard crust which almost stops the evaporation.
Hitherto the only way of breaking up this crust has been by the workmen opening
the oven doors and doing it with a hand rake, and this mode has been a very great
disadvantage to the effective working of the roaster, inasmuch as by opening the
doors a rush of cold air acts in and reduces the temperature of the oven; and although
the crust may be broken in this way, unless the breaking action is continuous the
surface of the material rapidly becomes encrusted. To meet and overcome such
difficulties I provide a series of mechanical breakers which are fitted in a row or
serics on one or both sides of the oven. When there are two rows, the breakers on
the one side of the oven fit and work within the spaces or intervals between those on
the other side. These breakers are made each of a bar of iron, tapered towards the

page_text: point; they are inserted through a small aperture in the sides of the oven, are centred
to work on a fulcrum fixed in the brickwork, and the exterior ends are connected by
a light rod with a lever centred on a bracket on the top of the roaster. The
other end of each of these levers is acted on by a cam on a revolving shaft, which
lifts the breakers one after the other in regular sequence and allows them to drop
by their own weight to the bottom, and the material is thus kept in agitation as
long as it is in a liquid state. When the lye becomes of too thick a consistency
for agitation the breakers can all be withdrawn in a few minutes through the
apertures by which they are inserted and fitted. When the lye material is in this
thick or pulpy state, and the breakers are withdrawn, I introduce a novel
construction of mechanical rake or scraper, which forms another improvement of
the Invention. This scraper consists of a cross bar or plate, the length of which is
equal to the width of the oven, and which is hinged on an axle with two wheels
and set at an angle, the one edge resting on the bottom or floor of the oven, while
the other is inclined upwards to the centre of the axle. This scraper or rake has
a traversing motion, and travels from end to end of the oven, the motion of
the rake being imparted to it by means of a long connecting rod passing out at the
end of the furnace and between a pair of rollers having a reversing motion by
which it is actuated. So long as the lye stuff is in a pulpy state the scraper passes
underneath it, and the stuff runs over the projecting ledge on the upper side of the
scraper and falls upon the bottom again; but when the stuff becomes drier, it
accumulates at the one end. The length of travel of the scraper is increased
a little, which forces it up to the top of an incline at the furnace end where the
stuff drops down through an opening in the bottom into a long iron box set on wheels
and closely perforated with small holes in the bottom, where it lies to smoulder_and_
-burn-during the time the next charge is being brought forward. The box may
then be drawn out, emptied, and replaced. An advantage in this arrangement is
that all the smoke and noxious gases which rise off the soda at this stage pass up
through the part above and under the flame of the furnace, and thus are either
consumed or sent up the chimney. When the scraper is not at work it is drawn
up to the one end into a space or recess always kept full of lye at the end of the
oven to keep it from burning when out of use, and from which it may be drawn
and cooled if it gets too hot while working.
A further improvevement of the Invention has reference to the construction of
scraping and agitating appliances fitted in connection with the pans for evaporating
the lyes. The flame and heat from the roaster pass along and underneath the
evaporating pans, and also along and over the top while they are kept brim full of
lye. In practice it is found that a heavy deposit settles down on the bottom of the
pan and prevents the heat from having such effect as it would otherwise have,
and tends to burn the bottom at the same time. The crust or scum that gathers
on the surface of the lye also greatly hinders the evaporation. To meet these
objections I introduce within the evaporating pan a travelling scraper and agitator
combined, which consists of two side bars or frames. This combined scraping and
agitating apparatus is carried on two axles, in length a few inches less than the
full width of the pan, fixed into the side bars at both ends; and on each axle are
placed two wheels, one of them being a toothed wheel, and all running loose on the
axles, Slipped onto the axles and between the wheels is a short iron tube which
also works loose on the axles, and on which are fixed arms or levers bent on the
one side of each axle towards the bottom and on the other towards the top. On
the other end of these arms is fixed a thin iron bar in contact with the bottom
of the pan forming a scraper, and on the upper end of one set of levers or arms is
a shaft fitted with small revolving reels with two, three, or more blades or
agitating paddles at the surface of the lye, and driven by a small pinion on the end
working into the toothed wheel on the axle. On the ends of the arms of the other
set is fitted a rake with teeth, and extending across the pan nearly the whole
width. On the centre of each of the axle tubes are fixed short arins connected with
a rod between and a joint at each end. To the one end of this ród a chain is

page_text: attachod, and passes round guide pulleys at each end of the pan and a supporting
pulley overhead, and is made fast to the rod at the other end. The action of this
combined scraper and agitator when at work is as follows:-When pulled along by
the chain in the one direction the scrapers are raised off the bottom and the reel
and rake are drawn down under the surface of the lye, and thus it is draggod on
to the end of the pan. Whon the motion is reversed, and the drag is in the
opposite direction, the scrapers are brought down on the bottom and the blades of
the reel and teeth of the rake are set up a little above the surface of the lye, and
in travelling along the teeth of the rake rip up the scum into stripes and tho
blades of the reel cut it across into patches, while the scrapers draw all the deposit to
the one end, where it can be most conveniently lifted out or withdrawn if required.