Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
- lQS4t~14
This invention relates geneFally to continuous
cryogenic treatment of materials. More particularly, the
lnvention relates to an apparatus for continuously feeding
material, such as scrap, through a freezing zone to render it
brlttle so that, thereafter, it can be crushed or impacted and
separated according to the various types of material of which
it is composed.
In the prior art, it is known to subject material,
such as insulated wire, to a low temperature gas, such as
nitrogen, in a liquid atomized state, so that the insulation
becomes brittle and can be cracked off of the metallic wire,
thereby separating the wire from the insulation. See, for example,
Morita et al, United States Patent 3,647,149, issued March 7, 1972.
One disadvantage of the prior art devices, such as that shown
in the referenced patent, wherein a conveyor belt is used ln the
freezing zone, i3 that it is difficult to lubricate the moving
parts of the apparatus within the extremely cold environment.
Also, there can be a frost build~up within the device and the
accumulation of fine particles or other undesirable material.
Other problems that have arisen in prior art devices
involve the distribution and agitation of the gas within the
freezing chamber and, in particular, involve attempts to get
maximum exposure of the product to the cooled gas and maximum
utilization of the cooling effect of the gas. The present
application is a division of Canadian application Serial No.
201,110 filed May 29, 1974 and various aspects of the apparatus
disclosed therein are claimed in such parent application and
in the other divisional applications Serial Nos.
and ~ ~ 57d filed simultaneously herewith.
~0 According to the present invention there is provided
a refrigerating means, comprising: a. a rotatable drum having
-- 1 --
l~S4814
means to receive and to discharge material; said drum
having an interior configuration which further comprises
transport means for advancing the material longitudinally
within said drum upon rotation of the drum; b. rotation
means engaging said drum for rotating said drum; c. an
intake header means through which material may be
introduced into said drum, juxtaposed to the material
receiving end of said drum so that said drum is free to
rotate with respect thereto, said intake header means
forming a chamber communicating with the interior of said
drum; d. refrigeration means within said drum to
refrigerate material while it is within said drum; said
refrigeration means further comprising a low temperature
fluid introduced within said drum; and e. recirculation
means to recirculate said fluid from said chamber of said
intake header means, to and through the end of said drum
from which material is discharged.
In drawings which illustrate embodiments of the
invention:
Figure 1 is a side view of an apparatus partially
broken away and shown in section with alternate positions
shown in phantom lines and certain portions shown
schematically;
Figure 2 is an enlarged section taken as indicated by
the lines and arrows 2-2 in Figure 1, which has been
foreshortened and partially broken away;
Figure 3 is a greatly enlarged section taken as
indicated by the lines and arrows 3-3 in Figure 2;
Figure 4 is an enlarged end view taken as indicated by
the lines and arrows 4-4 in Figure l;
Figure 5 is a foreshortened side view of an alternate
1054814
embodiment;
Figure 6 is a section taken as indicated by the lines
and arrows 6-6 in Figure 5, with portions of the apparatus
shown in phantom lines; and
Figure 7 is an enlarged section of a portion of the
device shown in Figure 1.
Although specific forms of the invention have been
selected for illustration in the drawings, and the
following description is drawn in specific terms for the
purpose of
- 3 -
~.o54~14
describing hesc forms of the invention, this description
is not intended to limit the scope of the invention which is
defined in the appended claims.
In Figure 1 a drum, designated generally 10, comprises
a cylindrical shell 12 made of a suitable material for with-
8tanding extremely cold temperatures, such as 304 stainless steel
or other similar cryogenic material. The interior of the drum
is provided with a means for transporting material through the
drum upon rotation of the drum. In the preferred embodimsnt
shown, the interior configuration of the drum comprises a flat
spiral blade 14 disposed in a helix welded along the inner
surface of the drum. The blade extends radially inwardly from
the wall of the drum a distance of approximately ona-tenth of
the diameter of the drum.
The drum is supported for rotation on a plurality
of rings 18 which provide a force transmitting, insulating
means. The rings are of a unique construction in that they
comprise two T-shaped members insulated from one another by
a spacer made of plastic or other suitable insulating and
force-transmitting material. A cross-section of a typical
ring is shown in Figure 3. The outer T-shaped portion 20 is
a metallic ring while the inner T-shaped portion is made up
of a plurality of L-shaped pieces 22 and 24 formed into an
annular ring. The stems of the T-shaped portions are opposed
and are joined by four brackets 26 L-shaped in cross-section
and a plastic spacer 30. Referring to Figures 2 and 3, each
of the brackets 26 are welded to their respective stems of the
T-shaped portions. Bolts 28 firmly clamp the plastic spacer 30
between the brackets 26.
The outside of the cylindér is covered with an
insulat~ng material 16, which extends outwardly from the shell
1054814
12 past thc inller free end of the stem 20 and engaglng and
covering the inncr portion of the r~ngs, but not beyond the
outer face of the ring 20, Thus, the insulation does not
inter~ere with the rollers 40 which have flanges 42 embracing
the cross portion Oe the T-shaped ring 20, so that the ring
tracks in and rolls on the roller 40. The rollers 40 are
driven by means of sprockets 44 mounted on common shafts with
.the rollers and interconnected by means of a chain 46. The
Qprocket 47 is mounted on a shaft 48 driven by a pulley belt
drlve means, designated generally 49, connected to a source
of motive power 50, Figure 1. This electric motor 50 is a
variable speed motor, so that the speed at which the drum 10
rotates on the driven rollers 40 can be ad~usted. Ad~usting
the speed of rotation ad~usts the travel of material through
the drum and thus regulates the exposure of the material
to cold gas. ~lternatlve means could be provided for rotating
the drum on the rings, such as hydraulic motors direc.tly
driving the rollers 40.
Material enters the drum 10 by means of the input
chute 60. This chute passes through a box-like entrance
header, designated generally 62, at the upstream end, designated
generally 64, of the drum 10. The upstream end 64 of the drum
has an annular face plate 66 fixedly mounted thereto. Over-
lapping the shell 12 is a cylindrical reinforcing shell 68
retained by an annular flange 70. Additional insulation is
provided at 71. The walls of the header 62 are insulated as
shown at 72. Between the insulation 71 and the insulation on
the outer wall of the header 62, there is a heat tape 65. This
tape can be heated by electricity remotely controlled to prevent
frost build-up in the space shown and thereby prevent wearing
of the insulation. At the point at which the chute 60 enters
1054814
thc hcader ~)2 there i~s a ~ree swinging plate 74 forming a
door wl~ich automat~al~y open.~ and closes as ~shown by the
phantom an~l ful] ~ine positions respectively in Figure 1, when
material comes d~wn the chute and enters the header on its way
toward the drum 10. An additional free swinging door is provided
by the insulated plate 76 mounted in the transverse partition
78 which completely divides thc box-like header into two
compartments. These doors serve a useful function in connection
with certain exhaust fans which will now be more fully
described.
A stack 80 is provided communicating through the
top of the header 62 with the upstream compartment 82. Within
the stack 80 there is mounted a discharge fan 84 driven by any
suitable motive means 85. The purpose of this discharge fan
is to draw off air coming in with the material down the chute
and also to draw off used nitrogen gas which may escape when
the door 76 is opened. A control damper 87 is provided on the
tischarge side of the fan 84.
In the preferred construction shown in Figure 5, the
chute 60 is replaced by an alternate forced feeding means, such
as a mechanical feeder 160, whlch reciprocates as shown by
the arrows. The feeder is shown basically in a schematic
form comprising a trough 162 mounted on arms 164 and driven
in a reciprocating motion by means of a motor and crank arm,
designated generally 166. This loosely shakes the incoming
material into the rotating drum. The mechanism is not
described in further detail herein since such feeders are
known in the art. Indeed, a vibrating feeder could also be
used as an alternative feeding means. It should be noted
that the stack will continue to have a fan and a control
damper for the same purposes as previously described.
~05D.~14
Whilc many kinds of materia].s can be processed by
the apparatus, it has particular applicability to scrap metal
which is composed of various components of material, such as
ferrous and nonferrous metals which cannot be cleanly separated
by mechanical means. By freezing the scrap material, it is
pos8ible to shatter it ln a crusher or impactor and then
separate out particular materials magnetically, or by other
suitable means. In Figure l we have shown schematically a
crusher 92 and a magnetic conveyor separator 94. ~hese devices
are not shown in greater detail, since they are well known
in the art.
The first stage in the separation process is the
freezing unit, and we provide a pre-cooling chamber and a
cooling chamber within our freezing unit 10. Liquid nitrogen
is introduced into the freezing portion of the chamber (which
i8 downstream when viewed in the direction of travel of the
material through the chamber), through a common header 100
and a plurality of nozzles 102. As the nozzles spray the
nitrogen into the chamber, it immediately vaporizes to low
temperature gas and comes into intimate contact with the moving
scrap material. As the drum rotates, the helical blade
transports or advances the material down the drum. The inner
surface of the shell 12 is continually moving with respect
to the material, so that this surface is re-exposed to the
cold gas intermittently and then comes in contact with the
under surfaces of the material. This also has the effect of
wiping the surface of the drum, thereby removing frost. This
contact may be enhanced where flights or vanes are used,
rather than a helix, by virtue of the churning action caused by
the tumbling of the material as it proceeds down the inner
surface of the drum. However, in this embodiment the helical
-` ~0548~4
blade 14 is p~eferable, since the continuity of the blade
presents a conÇiguration whlch is not susceptible to having
lrregular pieces of material hang-up on lt. The header lO0
is supported on a cable 104, which is fixedly connected at
one end to and within the heàder 62 and is fixedly connected
at the other end to any convenient structure, such as at 106.
A tension device 108 is provlded to ad~ust the tension in
the cable depending on the weight of the header 100. A
plurality of rings llO are connected to the header and disposed
about the cable to support the header on the cable.
The liquid nitrogen, as it enters the chamber, is
at a temperature of approximately -320F. In order to maximize
the effectiveness of the nitrogen contact with the material,
a flow ls provided by withdrawing some of the nitrogen gas
from the upstream end of the drum and pumping lt back through
a conduit 112 and a nozzle 114 into the downstream end of the
drum 10. The nitrogen gas is heavier than air and for the most
part lays in the bottom of the drum, which is mounted horizontally.
The internal transport means tend to make the gas flow out the
discharge end. The reverse flow condition tends to inhibit
this loss. It is difficult to maintain a closed fluid flow
system with so many openings at the entrance and discharge ends,
and, therefore, it is necessary to pump gas in at the discharge
end to maintain the flow. When the door 76 is closed, the
compartment 84 essentially communicates only through the port
86 in the end plate 66 within the cavity 89 formed within
the shell 12. Used nitrogen gas is drawn out through this port
86 and down through the conduit 88 by means of the recirculating
fan 90 which runs constantly as the device is operating. In
the processing of scrap iron, for example, this recirculation
of gas is at a temperature of about -150F once the unit reaches
1054814
its continllous operatlng condition.
In the preferred embodiment shown in Figures S and 6,
the nozzle 114 is replaced by an e~ector 214 mounted on the
discharge end of the conduit 112. The lntake end of the ln~ector
is provided with a control damper 216. In this embodlment,
the ~lscharge header 218 embraces the dlscharge end of the
rotating drum 10 to form a chamber for mounting the e~ector
214, as clearly illustrated in the figures. The bottom of the
header 218 has a plurality of trap doors 220 which are rotatably
mounted to swing between the closed positlon shown in full llnes
and the open position shown in phantom llnes. The doors are
spring biased or counterweighted by any suitable means (not
8hown) to return to their closed positlon when not acted upon
by materlal being discharged from the drum 10. Protective
means in the form of angle lrons and the like (as shown at
400; 401) are provlded mounted above the hinges to prevent
~amming of the hinge by material exiting from the unit. The
doors open into a chute 222, which has a second pair of similarly
mounted doors 224, which function in a similar fashion as
shown by the solid and phantom lines. The chute 222 opens into
the crusher 92. The e~ector improves the operation of the system
by recirculating a portion of the nitrogen which would otherwise
be discharged. This portion of the nitrogen is drawn into the
ejector from the discharge header 218 as shown by the arrows
in Figure 6 and is induced to flow from the discharge end of the
drum toward the intake or upstream end of the drum.
The flow pattern provided by the recirculating
system provides a pre-cooling chamber in the upstream portion
of the drum 10 between the port 86 and that nozzle which is
positioned at the upstream end of the header 100. In this
pre-cooling chamber, the nitrogen gas which has lo~t much of
1054814
its cooling power by virture of contact with the material in
the drum in tlle downstream freezing portion thereof, is
expo2~ed t0 the incoming material to reduce its temperature
before it enters the freezing chamber, thereby increasing the
effectlveness of the system in the freezing portion of the
drum.
Since more nitrogen is constantly being introduced
through the nozzles 102, there is a build-up of nitrogen gas
such that the excess must, at times, be withdrawn. This is
done in the recirculation cycle by means of the discharge
conduit 116 connected to a valve mechanism (shown schematically
at 117) which can be operated in response to an automatic
flow indicator 118.
The input of nitrogen, the withdrawal of used
nitrogen, and the speed of the rotation of the dru~ are all
regulated in accordance wlth the actual effect on the particular
items of material being processed. Thus, these can and must
be adjusted depending on the thickness of the material and other
factors which may be encountered in dealing with the particular
material. In the case of scrap, the end result is to render
some of the scrap components brittle and fragile by sub~ecting
it to the low temperature refrigerant gas while conveying it
ln the rotating drum, so that by the time the scrap is discharged
through the insulated free swinging door 119 down the chute
120, Figure 1, into the crusher 92, it is ready for fragment-
ation by impaction or crushing. To this end, thermocouples
are provided as at 300, 30l, 302, 303, 304 and 305 to monitor
temperature and for use in ad~usting the controls.
It will be observed from what has been described
that in operation this device automatically takes care of
frost build-up within the drum by virtue of the wlping action
-- 10 --
- lOS4~14
of the matcria~ nn thc w~lls of the drum, The lce whlcll is
removed is then tr~nsported out of the drum with the material.
This wiping action also prevents particle build-up. Further-
more, since there is no mechanism having moving parts within
the freezing zone, there can be no freeze~up of the material
transporting means.
It will slso be observed that by re-introducing a
portion of the nitrogen gas at the downstream end of the drum,
there is a thorough mixing and intimate contact between the
refrigerant gas and the material. This contact is enhanced
by the constant motion of the material within the drum.
It will be understood that various changes in the
details, materials and arrangement of parts which have been
herein described and illustrated in order to explain the nature
o this lnvention may be made by those skilled in the art
within the principle and scope of the invention as expressed
ln the following clalms. Por example, the same process and
apparatus can be employed for cooling other materials, such
as scrap rubber, food products, plastics, organic material,
metallics, and the like.
-- 11 --
