Treatment of particulate materials

Mobilization apparatus for the treatment, drying for example, of particulate material comprises a mobilization zone bounded by upwardly divergent walls. Particulate material in the zone is mobilized by being subjected to a flow of gaseous mobilizing medium supplied at a multiplicity of sites of the divergent walls. The material is simultaneously subjected to a flow of gaseous accelerating medium supplied in an upward direction from a lower region of the mobilization zone. The obtains in the mobilization zone of circulatory pattern comprising downward flow at the divergent walls and upward flow from a lower region of the zone. In order to discharge the particulate material from the apparatus, a mask extending outwardly from the lower end of an upwardly extending discharge duct is brought to the upper end of the mobilization zone. The result is that the circulatory pattern is destroyed and the material is pneumatically transported up the discharge duct.

This invention relates to the treatment of particulate materials. The 
invention is particularly relevant to the treatment of fibrous particulate 
materials such as, for example, cut lamina tobacco. 
As used herein the term "fibrous particulate material" means particulate 
material a substantial proportion at least of which comprises individual 
particles of which one length dimension is large by comparison with the 
other two length dimensions. Because of the presence of such elongate 
particles, within a body of fibrous particulate material there is a 
propensity for entanglement. 
As used herein the term "mobilisation" means a controlled process in which 
in a body of particulate material individual particles are maintained in a 
separated condition so that the particles are free to move relatively to 
each other. With reference to fibrous particulate material, mobilisation 
further means that the material is wholly or substantially disentangled 
and maintained in a disentangled, particle separated condition. 
As used herein the term "mobilising apparatus" means apparatus comprising 
wall means bounding a mobilisation zone, said wall means being upwardly 
divergent from the vertical, whereby the horizontal cross-sectional area 
of the mobilisation zone increases in an upward direction thereof, first, 
mobilisation nozzle means operable to supply gaseous mobilising medium at 
a multiplicity of sites of the wall means and second, acceleration nozzle 
means operable to supply gaseous accelerating medium in an upward 
direction from a location at a lower region of the mobilisation zone. 
The horizontal cross-section of the mobilisation zone can be of various 
shapes, including square, rectangular, circular, elliptical and polygonal. 
The shape may be constant or may vary from one height location of the 
mobilisation zone to another. The wall means may in vertical cross-section 
be straight; alternatively the wall means may be curved, in concave or 
convex fashion, over a part or the whole of the upward extent thereof. If 
the horizontal cross-section of the mobilisation zone is of square shape, 
or of other shape having oppositely situated and parallel wall members of 
the wall means, such wall members are preferably symmetrically configured 
with reference to a central vertical plane or axis. The angle of upward 
divergence of such wall members is suitably in the region of 30 degrees if 
the apparatus is to be used for the treatment of cut lamina tobaccos. 
At the bottom of the mobilisation zone the horizontal cross-section thereof 
should preferably be small in comparison with the horizontal cross-section 
at the top of the zone. 
Suitably, the mobilisation nozzle means takes the form of an array of 
perforations in the wall means. The perforated wall means may bound plenum 
changer means with which the perforations directly communicate. 
As used herein the term "a method of treating parrticulate material", means 
a method wherein particulate material, fibrous particulate material for 
example, is maintained in a mobilised state in a mobilisation zone bounded 
by wall means upwardly divergent from the vertical, whereby the horizontal 
cross-sectional area of the mobilisation zone increases in an upward 
direction thereof, gaseous mobilising medium being supplied at a 
multiplicity of sites of the wall means to the mobilisation zone whereby 
there obtains in said zone a circulatory pattern comprising downward flow 
at the wall means and upward flow from a lower region of the zone. 
Advantageously, gaseous accelerating medium is supplied to the mobilisation 
zone in an upward direction from a location at a lower region of the zone. 
The treatments of particulate materials which may be practised using the 
method or mobilisation apparatus of the type defined include drying, 
moistening, heating, cooling, blending, mixing, expanding or applying a 
flavourant or other additive. The treatments may also include chemical 
treatments. 
Air is a practicable mobilising medium and a practicable accelerating 
medium. Steam or other vapour or gas may be injected into the mobilised 
bed of particulate material, either directly or with the mobilising medium 
and/or accelerating medium. Steam or other vapour or gas may be employed 
as mobilising and/or accelerating medium. 
When the method of treating particulate material is carried out utilising 
an accelerating flow as well as a mobilising flow, the mobilising flow 
serves to mobilise the fibrous or other particulate material and the 
accelerating flow serves to enhance the circulation, and thereby the 
mixing, of the mobilised body of particulate material. It has been found 
that when the only gaseous flow employed is an upward flow, fibrous 
particulate materials remain or become entangled and so are not mobilised 
in the sense above defined. For any one particulate material or mobilising 
apparatus constructed in accordance with the present invention there will 
be a finite range of mobilising and accelerating flow rates within which 
controlled operation is possible. These ranges may be readily ascertained 
by simple experiment. 
The present invention provides mobilising apparatus comprising discharging 
means, said discharging means comprising discharge duct means and further 
comprising mask means movable between an obturating position and a 
non-obturating position, said mask means when in said obturating position 
providing a gas-flow barrier extending outwardly of said duct means at the 
upper end of the mobilisation zone. 
Preferably, the discharge duct means comprises a first, fixed duct and a 
second duct arranged for telescopic sliding movement with the first duct, 
the mask means being fixed to and extending from a lower end of the second 
duct. 
When the mask means is in the obturating position thereof the mask means 
advantageously contacts walls of the mobilising apparatus. 
The mask means may be of flat configuration. Alternatively the mask means 
may in section be of a curved, or partly curved configuration. 
The present invention also provides a method of treating particulate 
material, wherein gaseous accelerating medium is supplied to the 
mobilisation zone in an upward direction from a location at a lower region 
of said zone and mask means is moved to an upper location of the 
mobilisation zone, at which location the mask means extends outwardly from 
a lower, open end of upwardly extending duct means, whereby the 
particulate material is pneumatically transported upwardly through the 
duct means.

The mobilisation apparatus of FIGS. 1 and 2 comprises an upwardly extending 
casing 1 of square horizontal section, the side walls of the casing 1 
being designated by reference numerals 2-5. In FIG. 2 parts of walls 2 and 
3 have been removed. A lower part 6 of the casing 1 comprises upwardly 
diverent walls, three of which walls are designated by reference numerals 
7, 8 and 9 in FIGS. 1 and 2. Trunking 10 extends downwardly from the lower 
end of the part 6 of the casing 1. 
Disposed inwardly of and extending parallel to each of the walls of the 
part 6 of the casing 1 is a diffuser plate, those of these plates 
observable in FIGS. 1 and 2 being designated by reference numerals 11, 12 
and 13. Along the upper edge thereof each of these four diffuser plates 
contacts, in gas-tight fashion, a respective one of the side walls 2-5 of 
the casing 1. Each of the diffuser plates comprises an array of 
perforations, the perforations in plate 12 being designated 14 and those 
of plate 13 being designated 15. The diffuser plates bound a mobilisation 
zone. 
A pipe 16 extends through the wall of the trunking 10 and, as is indicated 
in FIG. 1, joins at its upper end the lower convergent ends of the 
diffuser plates. Fitted across the pipe 16 at its upper end is an orifice 
plate 17. 
Discharging means of the mobilisation apparatus comprises a trunking 18, 
providing a first part of discharge duct means, and a movable, gas 
impervious flange member 19 providing mask means. 
The trunking 18, which is fixed relative to the casing 1, extends from a 
location within the casing 1, which location is vertically spaced above 
the lower part 6 of the casing 1, through an upper end wall 20 of the 
casing 1. 
The flange member 19 is attached to and extends horizontally from the 
periphery of a length of inner trunking 21, providing a second part of the 
discharge duct means, at a lower end of the trunking 21, to the four side 
walls 2-5 of the casing 1. The outer side edges of the member 19 are 
provided with gas-tight seal means designated 19'. As depicted in FIG. 1, 
the member 10 is at an upper position thereof and the trunking 21 is 
disposed wholly within the trunking 18, from which it is held in spaced 
relationship by spacing means 22 and 23 attached to the trunking 21. 
The discharging means further comprises actuation means operable to move 
the flange means 19, together with the inner trunking 21, between the 
upper position thereof and a lower position thereof, which lower position, 
shown in broken line in FIG. 1, is close above the lower part 6 of the 
casing 1. The actuation means, which for the sake of simplicity is not 
shown in FIG. 2, may comprise, for example, two pneumatic cylinder and 
piston or other linear actuation units 24 and 25. Cylinders 26 and 27 of 
the units 24, 25 are disposed, in vertical orientation, at locations above 
and fixed relatively of the casing 1. Extended rods pass downwardly 
through glands 30 and 31, located in the top wall 20 of the casing 1, into 
attachment with the flange member 19. 
In use of the mobilisation apparatus for the purpose of, for example, 
drying moist cut lamina tobacco, a quantity of the tobacco is disposed 
within the space jointly defined by the four diffuser plates. Suitably, 
the tobacco is introduced into the casing 1 via the trunking 18 and 21 
from tobacco charging means (not shown). 
With the flange member 19 in the upper position thereof, warm mobilising 
air is supplied under low pressure to the trunking 10, from which it 
passes to the spaces between the walls of part 6 of the casing 1 and the 
associated diffuser plates and from there through the diffuser plate 
perforations into contact with the tobacco. Concurrently, warm 
accelerating air is supplied under low pressure to the pipe 16, from which 
it issues in a vertically upward direction into the tobacco charge. When 
starting up the process, it is preferable for the mobilising flow to be 
established before initiation of the accelerating flow. 
As a result of the geometry of the mobilisation zone and of the provision 
of mobilising air and accelerating air there is obtained a controlled 
mobilisation of the cut tobacco. Such mobilisation results in a 
disentanglement of the elongate fibres and the attainment of a close 
approach to a perfect mixing condition. 
The hatched area shown in FIG. 3 represents the zone of controlled 
operation of the mobilisation apparatus in terms of the superficial 
velocity of the mobilising air (ordinate A) and the superficial velocity 
of the accelerating air (abscissa B). 
In FIG. 4 there is indicated the circulatory pattern of air and entrained 
tobacco particles which obtains in the mobilised bed. It may be observed 
that there are downward flows at the sloping walls defining the 
mobilisation zone and an upward flow centrally of the zone. The 
circulatory pattern further comprises outward flows from the central zone. 
The mobilised bed is located substantially wholly within the space defined 
by the divergent walls, i.e. diffuser plates, although, as shown, the bed 
does extent to a location above the upper ends of the diffuser plates. 
The basic circulatory pattern just referred to is established by the 
mobilising flow, but is enhanced by the presence of the accelerating flow. 
The circulatory flow is, of course, superimposed upon a general upward flow 
of air within the apparatus. 
When it is desired to discharge the tobacco from the mobilisation apparatus 
the flange member 19 is moved to the lower position thereof under action 
of the cylinder and piston units 24, 25. When the member 19 occupies its 
lower position the member 19 obturates the space between lower end of the 
trunking 21 and the side walls 2-5 of the casing 1 at a vertical location 
of the casing 1 such that the above mentioned circulatory pattern is 
destroyed. As a result the upward air flow in the central zone is so 
significantly increased that the tobacco becomes subject to pneumatic 
transport upwardly through the trunking 18 and 21. The trunking 18 may at 
its end remote the casing 1 be connected to an air/tobacco separator (not 
shown). 
Whereas as shown in FIGS. 1 and 2 the walls 2-5 of the casing 1 extending 
vertically, it could be arranged for these walls to be gently downwardly 
convergent such that the outer edges of the flange member 19 contact the 
walls only when the flange member has been lowered to its lower, 
cirulatory-pattern destroying position.