Improvements in Apparatus for Drying White Lead, Colours, and other Powdery, Granular, or Nodular Substances.
Year: 1896

page_text: Date of Application, 14th, Apr., 1896
Complete Specification Left, 12th Jan., 1897-Accepted, 27th Mar., 1897
Improvements in Apparatus for Drying White Lead, Colours, and
other Powdery, Granular, or Nodular Substances.
I, THOMAS CRISP SANDERSON of 53 Cardiff Road Norwich in the County of
Norfolk, Chemical Engineer do hereby declare the nature of this invention to be
as follows:--
My invention relates to drying apparatus consisting of an endless web revolving
on rollers in a long closed heated chamber through which hot air is passed, the
substance to be dried being carried on the web in an opposite direction to the
current of air the chamber itself being heated by pipes or other radiating surface
heated by steam or other suitable means.
The air in its passage from end to end of the chamber is caused to circulate
constantly by means of the heated pipes which are separated from the frame
carrying the web by a brattice which is open below and above.
The air cooled by evaporating water from the substance falls down, passes under
the brattice, is re-heated by the radiating surface and passes by the opening at
the top of brattice back over the surface of the material while at the same time it
is moving slowly through the chamber.
I may arrange the heating pipes so that they are hotter or have greater surface
at the end of the apparatus at which the wet material is introduced thus raising
the air to a higher temperature as it passes along the chamber and meets substance
having more moisture.
I prefer to beat the material to be dried to about 212° Far. as it is charged into
the apparatus so as to prevent moisture depositing upon it when it comes into the
vapour laden atmosphere as would be the case if it were charged cold. To do this
in the case of white lead and similar substances I pass it between a pair of steam
It is best that it
heated rolls which drop it in a flaked condition upon the web.
should be previously filter-pressed.
In case of materials the dust of which would be objectionable such as white
lead the web is made to discharge in a hopper separated from the drying
chamber.
I do this by dividing the hopper from the chamber by plate carrying three
rollers one above another.
a
The web passes from the chamber to the hopper between the middle and upper
roller, the latter resting lightly upon the dried substance then over the end roller
where the substance is discharged returning into the lower part of the drying
chamber between the middle and lower roller. Before leaving the discharging
hopper a circular revolving brush removes any particles which might still adhere
to the web.
By connecting the hopper with a stithe chamber and causing a slight exhaustion
by means of a fan or otherwise, passage of dust to the drying chamber through
any spaces about the end rollers is prevented.
As the substance towards the centre of a band dries more slowly than near the
edges I may divide the web into two or more strips leaving a small space between
each to give passage to the air.
The hot air is introduced into the chamber at the end near the discharging

page_text: hopper and preferably at the top, and is discharged at the further end near the
floor from which it passes to a stack or chimney.
As the material is undisturbed while passing through the drying chamber and
the current of air is comparatively slow no dust is carried away.
Dated this 14th day of April 1896.
THOMAS CRISP SANDERSON.
Improvements in Apparatus for Drying White Lead, Colours, and
other Powdery, Granular, or Nodular Substances.
1, THOMAS CRISP SANDERSON, formerly of Norwich, but now of 42, Stopford
Road, Upton Manor, London, Chemical Engineer, 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:-
This invention relates to the drying of whitelead, colours and other powdery,
granular or nodular substances (hereinafter referred to as "whitelead,") and consists
of an improved arrangement of apparatus designed to effect such purpose and
characterized by the combination of a central chamber (hereinafter referred to as
the "drying chamber") through which the whitelead is slowly traversed, and is,
meanwhile, subjected to the drying action of heated air (hereinafter referred to as
"the drying air") travelling in a reverse direction, and side chambers (hereinafter
referred to as "re-heating chambers") which communicate with the drying chamber
at the lower and upper parts thereof, and serve to re-heat the drying air as it
becomes cooled by evaporating moisture from the whitelead and descends to the
lower part of the drying chamber and passes into the re-heating chambers, causing
it to re-enter the drying chamber at its upper part in a re-heated state; and so on,
repeatedly, whereby a much more effective drying action is obtained than with any
existing air drying apparatus applied to such purpose, and the apparatus is caused
to work much more economically.
On the accompanying drawings:-
Fig. 1, represents a sectional elevation on A B. Fig. 2.
Fig. 2 represents a sectional plan on C D, Fig. 1, and
Fig. 3 represents a sectional elevation on E-F, Fig. 1.
a is a main chamber within which the drying and re-heating operations are
effected and which may be made of any desired length according to the nature of
the substance intended to be treated therein.
At the upper part of one end, the chamber is formed with an inlet a', for the hot
drying air, and, at the lower part of the other end, it is formed with an outlet a
for the air laden with moisture evaporated from the whitelead. For the greater
part of its length, the chamber is partitioned-off into the said drying chamber a³,
and re-heating chambers at, by brattices a, which extend from near the floor to
near the roof of the chamber a, leaving bottom and top passages a, a', between
the chambers a³, a', the latter of which are closed at the ends as at a³.
Each of the chambers a', is independently heated to a temperature equal to or
exceeding that of the drying air supplied to the chamber a³, by steam-heated gill
fitted pipes a, (or by any other suitable means) arranged at the lower part of the
chamber, steam being admitted to the piping by a connection a0 at any convenient
part or parts of its length. The pipes a, may be duplicated or made with greater
radiating surface towards the ends of the chainber at which the moist whitelead is
introduced, so as to raise the temperature of the drying air as it travels along the
chamber a³, and meets wetter material.
The whitelead is carried through the chamber a³, on a slowly travelling endless

page_text: web (or webs) b, which, at the supply end, is mounted on an adjustable roller b¹,
and, at the discharge end, is mounted on a driving roller 63, to which a slow rotary
motion may be communicated by any convenient means, and, at its intermediate
part, is supported by rollers 6.
The inlet, for the whitelead is fitted with steam-heated rolls c, by which the
whitelead is fed onto the web b, in a flaked state, and in a sufficiently heated
condition to prevent moisture from the vapour-laden drying air it meets, from
depositing on it.
In the operation of the apparatus, the hot drying air supplied to the chamber a³,
flows, in a gentle current, over the slowly and reversely traversing layer of
wbitelead carried by the web b, and, as it gets cooled by evaporating moisture from
the whitelead, descends over the edges of the web, to the lower part of the
chamber a³, and flows thence, through the passages a; into the chambers a,
wherein it is then re-heated by the steam-piping a, and is caused to ascend within
such chambers, and to re-enter, through the passages a', the chamber a³, wherein
it again descends onto the whitelead, and, as it is again cooled by evaporating
further moisture therefrom, again descends into the chambers a', and is again
re-heated and so, while travelling from end to end of the chamber a³, it is caused
to circulate in a circuitous course through the chambers a³, a, alternately, being
repeatedly re-heated sufficiently to maintain its drying capacity throughout its
course until it passes beyond the inlet of the moist whitelead, when it descends to
its outlet a², whence it is led to a chimney.
The repeated re-heating of the drying-air so as to maintain its drying capacity
throughout its course, is of particular advantage in the drying of whitelead and
other substances the dust of which is injurious or obnoxious, as it enables the
drying treatment to be carried out in a long continuous chamber through which the
whitelead may be slowly traversed without being disturbed either by the traversing
apparatus or by the drying air, and without any of its dust being raised within the
chamber; in consequence whereof, the chamber itself is kept free from dust and
may be entered by workmen with impunity; and the effluent moisture-laden air is
discharged at the outlet a², free from dust, and, consequently, the dangerous nature
of the operation is considerably lessened.
With the same object, provision is also made for enabling the dried whitelead to
be discharged without any of its dust being drawn back into the chamber, and, to
this end, the chamber is fitted with a discharging hopper d, which is separated
therefrom by a plate d', having openings d', d, for the outward and return passage
of the web b, protected by aprons d', the opening d, through which the web
carrying the dried whitelead issues from the drying chamber into the hopper,
being further protected by being fitted with a roller d³, for supporting the web,
and with a loosely mounted roller d', which rests lightly upon the issuing dried
whitelead and accommodates any irregularities in the thickness thereof, rolling the
same down and preventing any dust being raised as the whitelead issues from out
of the drying chamber. The hopper is also connected, by a passage d³, with a
stithe chamber (not shown), through which, by means of an attached fan or the like, a
sufficient current of air may be caused to flow from the hopper to counteract any
tendency of the current of drying air through the drying chamber to draw any
dust from the hopper thereinto.
The returning part of the web is freed from any adhering particles of the
whitelead by a revolving brush d', driven from the roller b³.
It is not essential that the whitelead should be traversed through the drying
chamber on a travelling web, as a series of trays or other suitable carrying means
may be used for the purpose.
When the improved drying apparatus is adapted to the drying of tea-leaf and
other materials of an innocuous nature, it is not necessary to so completely close off
the discharging hopper from the drying chamber or to connect the same with a
stithe chamber and exhaust apparatus, and the material may be otherwise heated
than by the rolls c, before being admitted to the chamber a³.

page_text: Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what I
claim is :-
In apparatus for drying whitelead, colours and other powdery, granular or
nodular substances, the combination of a central drying chamber a³, heated by a
current of hot drying air, and through which the substance to be dried is slowly
traversed in a reverse direction, and side re-heating chambers a', independently
heated by steam piping or other suitable means, and communicating with the
drying chamber at the lower and upper parts thereof, and serving to re-heat the
drying air as it becomes cooled by evaporating moisture from the substance under
treatment and descends to the lower part of the drying chamber and passes into
the re-heating chambers, and to cause it to re-enter the drying chamber at its
upper part in a re-heated condition, and so on, repeatedly, so as to cause
continuous circulation thereof, and to maintain the temperature and drying capacity
of the drying air thoughout its operative course through the drying chamber, as
set forth.
Dated this 12th day of January 1897.
DAY, DAVIES & HUNT,
Chartered Patent Agents,
321 High Holborn, London, Agents for the Applicant.