U.S. patent number 3,843,101 [Application Number 05/301,883] was granted by the patent office on 1974-10-22 for flotation machine and impeller therefor.
Invention is credited to Charles A. Green.
United States Patent |
3,843,101 |
Green |
October 22, 1974 |
FLOTATION MACHINE AND IMPELLER THEREFOR
Abstract
An impeller for a flotation machine having a circular lower
plate with a central hole for supplying air through a hollow shaft
to the underside, and a circular upper plate having a larger
central hole and sloping downwardly toward the outside, together
with a series of radial, upright vanes between the plates which are
thicker at their outer edges than at their inner edges, both of
which are rounded, and a series of shorter, radial fingers
depending from the periphery of the lower plate, also thinner at
their inner rounded edges and thicker at their outer rounded edges.
This impeller is utilized with a stabilizer including outwardly
extending vanes which are thicker at their inner rounded edges and
thinner at their outer edges. The vanes and fingers include central
metal plates reinforced at their outer edges by rods, with the vane
plates and vane rods being welded between the impeller plates and
the finger plates and finger rods being welded to the lower side of
the under plate, to form a skeleton. The impeller skeleton may be
covered with rubber, which may be formed to provide the thickness
and rounded edges of the vanes and fingers. Also, the stabilizer
vanes may be formed of center plates welded to a support bar
structure extending around either the outside of the vanes or
disposed angularly of the lower outer corner thereof. The
stabilizer vanes and support bars may be covered with rubber, which
may be molded to provide the desired rounded inside edge and
variations in thickness. Both the stabilizer vanes and the impeller
are spaced above the bottom of the tank of the flotation machine,
so that a recirculation of pulp around and above the impeller
between the stabilizer vanes is obtained, as well as an outward
discharge of pulp by the depending fingers into the spaces between
the stabilizer vanes. Not only is the efficiency increased, but
also the problem of "sanding up" in the bottom of the tank is
overcome.
Inventors: |
Green; Charles A. (Chihuahua,
MX) |
Family
ID: |
23165307 |
Appl.
No.: |
05/301,883 |
Filed: |
October 30, 1972 |
Current U.S.
Class: |
366/265;
210/221.1 |
Current CPC
Class: |
B03D
1/20 (20130101); B01F 7/1675 (20130101); B01F
7/00033 (20130101); C02F 3/205 (20130101); B03D
1/1493 (20130101); B01F 7/00016 (20130101); B01F
7/00241 (20130101); B03D 1/028 (20130101); Y02W
10/10 (20150501); Y02W 10/15 (20150501) |
Current International
Class: |
B03D
1/20 (20060101); C02F 3/20 (20060101); B03D
1/14 (20060101); B01F 15/00 (20060101); B01F
7/16 (20060101); B01f 005/16 () |
Field of
Search: |
;259/96,95,107,108,6,7,8,23,24,43,44,66,67 ;210/219,220,221 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Jenkins; Robert W.
Attorney, Agent or Firm: Van Valkenburgh; Horace B. Lowe;
Frank C.
Claims
What is claimed is:
1. A rotatable impeller for a flotation machine, comprising:
a circular lower plate;
a circular upper plate concentric with and spaced from said lower
plate, said upper plate having a circular central opening
therein;
a series of vanes extending generally radially and disposed between
said upper and lower plates, said vanes being constructed and
arranged to pump pulp and the like from said central opening of
said upper plate and discharge the same from the periphery of the
space between said plates; and
a series of fingers spaced around the periphery of said lower plate
and depending therefrom, said depending fingers being equally
spaced about the periphery of the underside of said lower plate,
having a radial length less than the radial length of said vanes
and having a lateral thickness adjacent the outer edge greater than
adjacent the inner edge thereof.
2. An impeller as defined in claim 1, wherein the vertical distance
between said upper and lower plates is greater adjacent said
central opening than adjacent the periphery of said plates.
3. An impeller as defined in claim 1, wherein the lateral thickness
of said vanes is greater adjacent the periphery of said plates than
adjacent said central opening.
4. An impeller as defined in claim 3, wherein said vanes are
equally spaced and each vane has substantially the same lateral
thickness at different points along the radial length thereof as
the other vanes.
5. An impeller as defined in claim 4, wherein the centerline of
each said vane lies in approximately a radius of said plates.
6. An impeller as defined in claim 1, wherein both the inner
upright edge and the outer upright edge of said fingers is rounded
and convex.
7. An impeller as defined in claim 1, wherein:
the vertical distance between said upper and lower plates is
greater adjacent said central opening than adjacent the periphery
of said plates;
said vanes are equally spaced, and each vane has substantially the
same lateral thickness at different points along the radial length
thereof as the other vanes; and
both the inner upright edge and the outer upright edge of said
fingers is rounded and convex.
8. In a flotation machine having a tank, the combination with an
impeller as defined in claim 7, of:
a series of generally radial, upright vanes disposed outwardly from
and surrounding said impeller adjacent the bottom of said tank;
means for supporting said outward vanes to hold said vanes with the
lower edges thereof spaced from the bottom of said tank;
means for rotating said impeller about a vertical axis supporting
said impeller with the lower ends of said depending fingers spaced
from the bottom of said tank and including a hollow shaft for
supplying an aeration fluid to the underside of said impeller;
said outward vanes having a lateral thickness adjacent the inner
edge greater than the lateral thickness adjacent the outer edge
thereof and the inner edges of said vanes being rounded and convex;
and
the upper inner edges of said outward vanes being disposed above
the outer upper periphery of said impeller and the lower ends of
said depending fingers and the lower edges of said outward vanes
are disposed at approximately the same height above said tank
bottom.
9. A rotatable impeller for a flotation machine, comprising:
a circular lower plate;
a circular upper plate concentric with and spaced from said lower
plate, said upper plate having a circular central opening therein;
and
a series of vanes extending generally radially and disposed between
said upper and lower plates, said vanes having a greater lateral
thickness adjacent the periphery of said plates than adjacent said
opening and both the inner upright edge and the outer upright edge
of said vanes is rounded and convex.
10. In a flotation machine having a tank, the combination with an
impeller having:
a pair of vertically spaced, concentric circular plates, each of
said plates having a central circular opening, with one opening
being smaller than the other;
a series of vanes extending generally radially and disposed between
said plates;
a series of fingers extending vertically from one of said plates
and spaced around the periphery thereof;
of a series of generally radial, upright vanes disposed outwardly
from and surrounding said impeller adjacent the bottom of said
tank;
means for supporting said outward vanes with the lower edges
thereof spaced from the bottom of said tank; and a hollow shaft for
rotating said impeller about a vertical axis with the lower edge of
said impeller spaced from the bottom of said tank, said hollow
shaft supplying an aeration fluid to the underside of said
impeller.
11. In a flotation machine as defined in claim 10, wherein:
said outward vanes have a lateral thickness adjacent the inner edge
greater than the lateral thickness adjacent the outer edge
thereof.
12. In a flotation machine as defined in claim 11, wherein:
the inner edges of said outward vanes are rounded and convex.
13. In a flotation machine as defined in claim 10, wherein:
said outward vanes are equally spaced about the periphery of said
impeller and the outer edges of said outward vanes correspond
generally to a rectangle.
14. In a flotation machine as defined in claim 10, wherein:
the upper inner edges of said outward vanes are disposed above the
outer upper periphery of said impeller.
15. In a flotation machine as defined in claim 14, wherein:
the lower edges of said depending fingers and the lower edges of
said outward vanes are disposed at approximately the same height
above said tank bottom.
16. In a flotation machine having a tank:
an impeller disposed adjacent the bottom of said tank, having upper
pumping means for receiving pulp and the like centrally and from
above and discharging the same outwardly, and lower agitation and
pumping means for agitating and moving outwardly pulp and the like
from the underside of said impeller;
means for rotating said impeller and supporting said impeller
spaced from the bottom of said tank;
means for supplying an aeration fluid to said lower agitating and
pumping means;
means surrounding said impeller, for receiving a pulp mixture from
both said upper pumping means and said lower agitating and moving
means, for interrupting the circular flow of said pulp mixtures and
for producing an intermixing of said pulp mixtures with said
aeration fluid; and
means for supporting said means surrounding said impeller at a
position above the bottom of said tank corresponding to the
position of said impeller.
Description
This invention relates to flotation machines which are utilized in
separating mineral to be recovered, from gangue or waste, through
the lifting of desired particles by bubbles of air or other
suitable gas, with the addition of suitable reagents which insure
or assist in the frothing and lifting of the particles.
For flotation, the raw ore is ground or otherwise comminuted to a
relatively small size, such as to below 1/4 inch in size to micron
sizes.
Prior flotation machines have had a tendency to "sand up," i.e. the
ground ore tends to collect in the bottom of a flotation cell and
tends to render the machine ineffective, sometimes even stalling
the impeller of the machine. The coarse particles more usually
produce sanding difficulties, although this problem is not unknown
with fine particles. In addition to the difficulties in operation,
the tendency for the machine to sand up also decreases its
efficiency and effectiveness in removing the desired particles. In
addition, the level of pulp in most flotation machines tends to
oscillate upwardly and downwardly, thereby decreasing both the
effectiveness and efficiency of the machine.
Among the objects of this invention are to provide a novel
flotation machine and impeller therefor; to provide such a
flotation machine in which the tendency for sanding up is
materially decreased; to provide such a flotation machine in which
the effectiveness and efficiency is increased; to provide such a
flotation machine in which the tendency for the pulp level to
oscillate is decreased; to provide a novel impeller for a flotation
machine; to provide such an impeller which will, with an
appropriate stabilizer or diffusion vanes, tend to alleviate the
problem of sanding up; and to provide such an impeller which is
effective and efficient in operation.
In accordance with this invention, the impeller of the flotation
machine is provided not only with a lower agitating and pumping
section at which the aeration gas is supplied, but also an upper
pumping section which recirculates the pulp from its center
outwardly and through the stabilizer or diffuser into which the
lower aeration and pumping section discharges. Such recirculation
of the pulp, which has previously been agitated and forced
outwardly, not only increases the recovery rate and efficiency of
the machine, but also decreases the tendency for the pulp level to
oscillate.
A preferred embodiment of this invention is illustrated in the
accompanying drawings, in which:
FIG. 1 is a perspective view of a flotation machine constructed in
accordance with this invention, with a portion of the exterior of
the tank being broken away to show the impeller and stabilizer
within the tank;
FIG. 2 is a perspective view of the skeleton of the impeller of
FIG. 1, i.e. prior to molding thereon a corrosion and abrasion
resistant covering;
FIG. 3 is a horizontal section, taken along line 3--3 of FIG. 4 but
with certain parts of the impeller and a stabilizer having a
modified support broken away and shown in section, for clarity of
illustration; and
FIG. 4 is a central vertical section taken along line 4--4 of FIG.
3.
The flotation machine of FIG. 1 includes a tank T which may be
essentially conventional in construction, being generally square or
rectangular in lateral configuration, and having a froth overflow
lip 10 at one end and a bottom 11. The froth overflow lip 10 may be
provided at one or at both opposite sides, while a conventional
feed inlet and weir structure for the outflow of tailings or
material to be discarded may be on the side adjacent the overflow
or opposite thereto. The tank may also be provided with a pulp
level control weir which essentially determines the depth of the
froth. These elements are all conventional and are therefore not
shown, except for the froth overflow lip 10.
Installed normally centrally within the tank T and suspended by a
tubular shaft 12, through which air may be supplied to the
underside thereof, is an impeller I, which will be described in
detail later. The shaft 12 is connected by a coupling 13 with a
hollow shaft 14 which extends upwardly within a bearing housing 15,
within which air is supplied through an air pipe 16 to the interior
of the hollow shaft. Shaft 14, the upper end of which may be
provided with a suitable plug, extends above the bearing housing 15
and is connected, through a suitable reduction transmission, with a
conventional drive motor (not shown).
The skeleton of the impeller I, prior to the molding of a suitable
corrosion and abrasion resistant elastomer thereto, is shown in
FIG. 2. Thus, the impeller I includes a lower plate 20 which is
circular and provided with a circular hole 21 at the center,
surrounded by bolt holes 22, for attachment of the lower end of
shaft 12 thereto. The impeller also includes an upper plate 25
having a central opening 26, larger in diameter than hole 21 in the
lower plate, and sloping outwardly from the central opening 26 to
its outer periphery. The angle of the outward slope of upper plate
25 may be altered considerably, although an angle of approximately
13.degree. to the horizontal may be found to be suitable in many
instances. A series of pump vane plates 27 are attached, as by
welding, in perpendicular relation to and between the lower plate
20 and upper plate 25, with a rod or post 28 extending between the
plates 20 and 25 at the outer edges of the vane plates 27. Both the
vane plates 27 and the rods 28 are attached in a suitable manner,
as by welding, to the upper and lower plates and to each other.
Depending from the lower plate 20 is a circumferentially spaced
series of finger plates 29 attached at their outer edges to
depending rods or posts 30 and desirably welded to the underside of
plate 20. The number of vanes, determined by the number of vane
plates 27, may be varied considerably, although a series of
radially extending, equally spaced vane plates 221/2.degree. apart
will be found suitable in many instances. Also, the number of
finger plates 29 may be varied, although twice the number of finger
plates as vane plates may be found suitable in many instances. In
the event that the number of vane plates and finger plates shown
are utilized, alternate finger plate rods 30 may be integral with
the vane rods 28, merely extending through a hole drilled in the
lower plate 20 at an appropriate position. After the skeleton of
the impeller I has been assembled, as in FIG. 2, the entire
impeller is provided with a covering of an elastomer having
suitable corrosion and abrasion resistant qualities. The thickness
of the elastomer coating may be varied considerably, in accordance
with the useage, and may also be varied at different portions of
the impeller, depending upon the wear expected at such portions.
The elastomer coating may be rubber or plastic, such as a suitable
polyvinyl chloride.
The elastomer coating 31 on the impeller is molded on the impeller
skeleton so that a series of vanes 35, as in FIG. 3, and a series
of depending fingers 36 are formed, with both the vanes and fingers
extending radially and each having a greater lateral thickness
adjacent its outer edge than adjacent its inner edge. Also, the
vanes each have a convex, rounded and conveniently arcuate inner
edge 37 and outer edge 38, while the fingers 36 also have a convex,
rounded and preferably arcuate inner edge 39 and outer edge 40. The
radial length of the fingers 36 is preferably less than the radial
length of the pumping vanes 35, such as about 1/4 to 1/2 the length
thereof. The impeller I, as in FIGS. 3 and 4, is mounted on the
lower end of shaft 12 by a ring 41 which is secured, as by welding,
to the lower end of the shaft, and a series of bolts 42 which
extend through bolt holes 22 of FIG. 2. Both the bolts 42 and the
nuts 43 therefor are provided with an elastomer coating 31 which,
in the case of rubber, is applied to the assembly, after attachment
to the shaft, and then vulcanized. If desired, the exterior of
shaft 12 may also be coated with an elastomer. Since air only
passes down the inside of the shaft, it is unnecessary to provide
an elastomer coating there.
The stabilizer S includes a plurality of vanes 45, as in FIG. 1,
which extend radially from the impeller, the vanes being
rectangular but of differing lengths, since the vanes extend
outwardly to a supporting bar 46 which has a rectangular or square
configuration corresponding to the inside of the tank T. The inner
edges of the vanes 45 are spaced a short distance from the
periphery of the impeller I, preferably with a clearance, such as 1
inch, greater than that necessary for normal clearance, to
accommodate lateral whipping of the suspended impeller as it comes
up to speed. The support bars 46 are, in turn, supported at each of
the four corners by an angular bracket 47 which is mounted on the
bottom of the tank and holds the lower edges of the stabilizer
vanes 45 in spaced relation to the tank, with the impeller I being
suspended at a height such that the clearance between the lower
ends of the depending fingers 36 and the bottom of the tank is
approximately the same as the clearance between the lower edges of
the stabilizer vanes and the bottom of the tank. If desired, the
stabilizer vanes 45 may be of equal length, with the supporting
bars 46 forming a circle.
Each vane 45 of the stabilizer S may be merely a rectangular plate
48, as in FIG. 4, welded at the outside to the supporting bar 46 of
FIG. 1, or may be bevelled at the lower outside corner, so that
each supporting bar 46' of FIG. 4 will be disposed at about
45.degree. to the plane of the tank bottom. Instead of the brackets
47 of FIG. 1, alternative brackets 49 may be utilized, having a
flange 50 at the upper end extending at the same 45.degree. angle
as the bars 46', and a perpendicular flange 51 at the bottom
attached to the bottom 11 of the tank, or merely resting on the
bottom of the tank, with suitable provision for lateral restraint,
such as an angle attached to the bottom of the tank and against the
outside of which the brackets 47 or 49 abut.
The support bars 46 and 46', as well as the plates 48 and the
brackets 47 or 49, are provided with an elastomer covering 31,
conveniently molded thereto, and if rubber, then vulcanized. In
addition, the bottom 11 of the tank is provided with a wear pad 55
having a molded elastomer covering 31 thereon which extends between
the walls of the tank, except for cutouts 56 at the corners, to
accommodate the brackets 47 or 49.
As in FIG. 3, the elastomer covering for the stabilizer or diffuser
vanes 45 is preferably molded so that the lateral thickness of the
vanes will be greater adjacent the inner edge than adjacent the
outer edge, i.e., directly opposite to the configuration of the
pumping vanes 35 and the fingers 36. Also, the inner edge 57 of
each diffuser vane 45 is convex and rounded, preferably arcuate,
while the outer edge 58 may have any configuration, such as
transverse to the plane of the plate 48.
As indicated previously, the lower edges of the fingers 36 are
preferably spaced the same distance from the bottom of the tank as
the lower edges of the vanes 48. Similarly, the upper edge of the
impeller I may be approximately the same height, or spaced a short
distance above the upper edges of the diffuser vanes 45. Also,
while the pump vanes 35 and fingers 36 extend radially of the
impeller, each may be curved, to increase the pumping action in one
direction, although a radial position of the vanes and fingers may
be preferred, since after the elastomer on one side of the vanes
and fingers has worn sufficiently to require replacement, the
direction of rotation of the impeller may be reversed and the other
side used until worn.
Considering now FIGS. 1 and 4, it will be evident that, with the
impeller rotating in either direction at an appropriate speed, the
pulp in the bottom of the tank will be agitated and thrown
outwardly into the spaces between the vanes of the stabilizer S by
the depending fingers 36. At the same time, the pumping vanes 35
will suck pulp downwardly around the shaft 12, and pump this pulp
outwardly into the spaces between the diffuser vanes. The
inclination of the top of the impeller I tends to cause the
velocity inside the impeller and velocity of discharge to be
similar. The impeller I tends to produce a swirling motion to the
pulp, which is broken up by the vanes of the stabilizer S. In
addition, the recirculation discharge from the pump portion of the
impeller will cause a high degree of agitation of the pulp, both
within and above the diffuser or stabilizer, through an intermixing
of the pulp discharged from the pump portion of the impeller with
the pulp discharged from the lower portion of the impeller. In any
event, it has been observed that the combination of the upper pump
and the lower agitator and pumper of the impeller produces a more
violent agitation of the pulp within and above the diffuser S than
an agitator or a closed impeller alone. Thus, it has been observed
that the violent agitation, particularly directly above the
stabilizer S, causes the air bubbles to be subdivided and as a
result, a greater number of air bubbles produced to act on the
particles to be floated off.
It has also been observed that there are essentially three zones in
the machine constructed in accordance with this invention, i.e., a
first or lower zone which extends from the bottom of the tank
upwardly to approximately 2 or 4 inches above the top of the
stabilizer S, in which zone there is violent agitation and some
feed to the pump of the impeller I. The second or intermediate zone
is above the first zone and extends up to approximately 2/3 to 3/4
of the height of the pulp level determined by the position of the
froth overflow lip 10 of FIG. 1 and the weir bars for waste, in
which the pulp becomes progressively quiescent, with the remainder
of the feed around shaft 12 downwardly toward the intake opening of
the pump of the impeller I. The third or upper zone, approximately
the upper 1/3 or 1/4 of the pulp body, is relatively quiescent,
except for air bubbles carrying recoverable material upwardly in
this zone. In this zone, the mechanical lifting of particles,
extending through substantially the entire range of sizes, occurs
without material assistance from the pumping effect of the
impeller.
For test purposes, an impeller constructed in accordance with this
invention was substituted for the impeller of each of ten Galigher
No. 48 flotation machines, in a mill separating fluorite from
gangue which included calcite, with the deslimed feed size of these
rougher cells being as follows:
+28 mesh 8% +60 mesh 40% +350 mesh Balance
Since the coarser sand, such as +60 mesh and particularly +28 mesh,
has a tendency to settle more readily than the finer sand, the feed
to these cells was considered to be an adequate test of their
capabilities.
Thus, it was found that the peripheral speed of the impeller could
be reduced from 1,170 feet per minute to 780 feet per minute; that
the feed rate could be increased from 2,100 metric tons to 3,150
metric tons per day; that the precentage of mineral recovery was
increased by 11.9 percent; and that the power consumption per cell
was lowered from 3.825 horsepower to 2.95 horsepower, a saving of
22.8 percent. It was also noted that the pulp body had little
tendency to oscillate upwardly and downwardly and that there was no
tendency for sand, particularly the coarser sand, to collect at the
bottom of the tank, particularly in the corners. Each of the test
machines had a stabilizer with outwardly extending vanes which were
uniform in thickness, rather than tapering, as in the preferred
form of this invention. However, other tests have indicated the
desirability of the tapered stabilizer vanes.
When any flotation cell is stopped, there is a tendency for sand to
settle out and collect in the bottom of the tank which, for a
shutdown of between 5 and 10 minutes, but without further feed,
required manual assistance in the case of previous machines for
starting up after such a shutdown. However, the machines of the
present invention started up much more readily and without manual
assistance.
Although a preferred embodiment of this invention has been
illustrated and described and certain variations thereof shown or
indicated, it will be understood that other embodiments may exist
and that other variations may be made, all without departing from
the spirit and scope of this invention.
* * * * *