Note: Descriptions are shown in the official language in which they were submitted.
CA 02198671 2004-O1-16
MULTIPLE SHEAR MDCING APPARATUS
The present invention relates to a multiple shear mixing apparatus for slurry
type solid-liquid mixtures. The apparatus includes a storage tank having an
internal
jet mixer, a pump, a rigid shear filter, a jet nozzle with vacuum chamber
surrounding
same and inlet port in the chamber, a venturi tube coupled with the jet nozzle
and
a return to the storage tank. The apparatus can be used to prepare suspensions
or mixtures such as drilling muds or to recondition used muds, and may be part
of a drilling system.
Slurry type solid-liquid mixtures have been prepared using various blenders
and mixers usually individually and on a batch basis. Pumps have been used to
off-load mixed product and occasionally may be part of the mixing apparatus.
Note, for example, U.S., Patent No. 4,285,601, issued August 25, 1981 to
Miner.
Drilling muds require considerable shear in their formation and a shear mixing
apparatus has been designed using annular concentric housings (see U.S. Patent
No. 4,184,771, issued January 22, 1980 to Day).
In the context of detergent foam formation and delivery, a reference (U.S.
Patent No. 3,547,409, issued to Jacuzzi December 15, 1970) has been noticed in
which a jet nozzle and venturi have been combined in a flow line to enable
mixing
of foam ingredients, foam formation and delivery.
No references have been noticed to a multiple shear in-line (or loop) mixing
apparatus for slurries, suspensions or drilling muds, in which materials may
be
repeatedly cycled to enhance mixing and uniformity before off-loading product.
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In accordance with one aspect of the present invention there is
provided a method of mixing fluid suspensions comprising fluid suspension
components, said method comprising:
providing at least part of the suspension components in a storage tank;
pumping said components from the storage tank through a shear filter;
passing the filtered components through a jet nozzle surrounded by a
chamber, the nozzle jet causing a vacuum within the chamber;
directing the nozzle jet into a venturi tube with a throat, said venturi
tube having an output;
passing the output of the venturi tube into the storage tank;
introducing feed components into said chamber then through the
venturi tube;
repeatedly cycling components out of, and returning to, the storage
tank until uniformly mixed; and
withdrawing mixed product between the shear filter and the jet nozzle.
In accordance with another aspect of the present invention there is
provided a multiple shear mixing apparatus for treating a slurry-type
solid/liquid mixture, comprising:
a storage tank for the mixture;
a pump connected to the storage tank and suitable for pumping said
mixture from the storage tank;
a shear filter connected to receive the mixture from the pump;
a jet nozzle downstream of the shear filter;
a venturi tube located to receive mixture from the jet nozzle;
a vacuum chamber surrounding the jet nozzle and an inlet end of the
venturi tube and having at least one port for the introduction of starting or
make-up materials to the chamber;
an off-loading outlet for the mixture between said shear filter and said
jet nozzle;
a jet mixer within the storage tank;
CA 02198671 2004-O1-16
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wherein the above components are interconnected and adapted to
pump said mixture from the storage tank, through the shear filter, then
through the jet nozzle and chamber, hence into the venturi tube and from the
venturi tube into the storage tank, while allowing some of the mixture to be
removed from the apparatus through said off-loading outlet.
Having here summarized the invention, reference will now be made to
the accompanying drawings illustrating preferred embodiments.
Figure 1 is a side perspective view of a typical arrangement of the
mixing apparatus;
Figure 2 is a top plan view of the apparatus of Figure 1;
Figure 3 is a schematic diagram of the fluid path through the primary
mixing components;
Figure 4 is a vertical sectional view through the storage tank showing
the location of, and feed conduit for, the tank jet mixer;
Figure 5 is a vertical sectional view through one typical tank jet mixer;
and
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Figure 6 is a top plan view of the tank jet mixer of Figure 5 primarily
showing
the horizontal base and the location of the jet holes in the vertical walls
just above
the base.
Similar numerals in the drawings denote similar elements.
While the pump may be any design to handle solid-liquid mixtures, one type
found very suitable is a trash pump which can cope with the irregular sized
solids
encountered on recycling used drilling muds. The capacity and output of the
pump
needs to be selected in conjunction with the components particularly the shear
site
components (as illustrated below). The pump intake is from the storage tank
preferably near the jet mixer location.
The shear filter is chosen to remove solids that are above the maximum size
tolerated by the rest of the system. The shear at the filter openings helps to
break
down aggregates on agglomerates formed of smaller sized pieces. One fitter
type
found very suitable is a cylindrical sleeve or tube having openings in the
periphery,
with the flow entering axially at one end and exiting radially through the
openings.
Preferably, a bleed of flow that has passed through the filter is fed to the
tank jet mixer in which the jet openings are not smaller (and preferably
larger) than
the filter openings to avoid plugging. It has been found preferable to
withdraw
mixed and filtered product after the filter and before the jet nozzle.
The tank jet mixer is designed to direct jets across the bottom of the tank to
minimize settling and dead spots. A smaller number of vertical (upward) jets
may
be used to encourage bottom to top mixing in the tank. Various jet mixers with
nozzles or openings may be used with one preferred type described in detail
below.
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The main jet nozzle opening is sized to suit the pump capacity and back
pressure (a preferred example is given below). An operative nozzle opening
size
range for drilling mud type mixtures may be from about 0.5 inch to about 0.9
inch
diameter. The nozzle and associated funnel are fitted into a chamber able to
maintain whatever vacuum is generated by the nozzle flow.
The vacuum chamber is fitted with at least one opening to introduce starting
or make-up materials. It has been found preferable to have a valued hopper
type
inlet for solid materials, e.g. crude feed and a separate port for liquid
materials, e.g.
make-up liquid. The vacuum chamber encloses the upstream end of the venturi,
with the venturi being directionally coupled with the main jet nozzle.
The venturi intake funnels the jet nozzle stream to the venturi throat and
from
there the flow diverges through the venturi tube, and onward to the storage
tank.
An operative venturi throat diameter range may be from about 1.0 inch to about
1.6
inch LD. for mud type mixtures depending on the capacity of the pump and the
size
of nozzle used.
The storage tank may be formed of plastic or metal, and sized to allow
sufficient hold up of mixture to allow for batch or continuous operation as
desired.
This multiple shear combination has several advantages. The combination
allows for preparing mixtures from starting components, or from partial or
used
mixtures with make-up components added as required. The mixtures may be
cycled out of and into the storage tank many times to increase uniformity and
to
allow for addition of various materials. It has been found to be desirable to
have
the final product outlet (between filter and nozzle) of smaller size than the
circulating
stream size, so that, as final product is off-loaded, more mixture is still
being
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circulated, made up, filtered, etc. In fact, the combination may be operated
in a
continuous mode, or in a batch mode as desired.
Reference will now be made to the drawings and to one example which is
typical (and found preferable) but not limiting.
Referring to Figures 1 and 2, pump 10 is driven by a gasoline engine (not
shown) fed from gas tank 11, and connected to input conduit 12 from storage
tank
40. In the example, the pump selected is a centrifugal one with a two-vane
impeller
and diffuser. The type of pump used can be any suitable type to obtain a
sufficiently high vacuum in the mixing chamber. The output of the pump 10 is
through conduit 13 connected to filter housing 15. The selection of the filter
will be
made to achieve a filter size such that it removes large particle material,
permitting
passage only of particles capable of being processed by the balances of the
system. This is desirable to prevent blockage of any openings in the nozzles,
etc.
Downstream of the filter element (shown in Figure 3 at 15A), the off-loading
valve
is shown at 28 in Figure 1. Valve 29 and conduit 31 carry a bleed flow to feed
internal tank jet mixer 30 (via internal conduit 31 A shown in Figure 4). From
housing 15, the flow is directed to nozzle intake 16 and nozzle 17 within
vacuum
chamber 18. Chamber 18 has a top hopper 20 attached to hopper table 20A.
Hopper shut-off valve is shown at 21 and auxiliary intake port at 22. The flow
then
proceeds through venturi 19 and conduits 23 and 24A into storage tank 40.
Conduit 24A is inside tank 40 such that the return flow is released near the
top of
the tank and preferably above tank jet mixer 30. Storage tank 40 has cover 8
over
access hatch (not shown) and anchor straps 5 and 6. The combination is mounted
on skid frame 7. Couplers of various types may be used.
The intake port 22 may be used for the addition of various components such
as fresh water for the system, reclaimed mud from a reclaimer, powdered
material
from a source of the same, various types of additives from primary sources.
The
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addition of various components through inlet port 22 may be manual or through
automated systems as desired, and of course, can take place while the system
is
operating.
In Figure 3, arrows show the flow path in more detail. The inlet flow 12 from
tank 40 enters pump 10 and exits through 13 to filter housing 15 containing
filter
tube 15A. Product outlet is shown at 28 which is a mixed product outlet and
bleed
to tank jet mixer is shown at 29. The flow then proceeds to nozzle intake
funnel 16
and to nozzle 17. The hopper is indicated at 20 and the hopper shut-off valve
at
21. The second intake port is shown at 22. The flow then proceeds through
venturi intake 19A, throat 19B and venturi tube 19, then onward to storage
tank 40.
The in-line filter may be mounted using quick-couplers for cleaning purposes;
the filter housing may be such that it includes at least one access opening to
permit
manual flushing.
Figure 4 shows storage tank 40 in vertical section, with the tank jet mixer at
30. The bleed line to the jet mixer is shown at 31 A and the main flow return
at 24A.
The jet mixer 30 preferably is located centrally at or near the bottom of tank
40.
Figure 5 is a vertical section through an example of jet mixer 30 showing
inlet
coupler 32, top plate 33, side wall 34, bottom plate 36, and mounting holes
37.
Holes for horizontal jets (e.g. 5) are shown at 35 in wall 34. Holes (e.g. 2)
for
vertical jets in top plate 33 are shown at 33A.
Figure 6 is a top plan view of top plate 33 showing inlet coupler 32, wall 34
and horizontal jet holes 33A. A mounting plate (not shown) may be used having
holes aligned with holes 37, for mounting the jet mixer 30 to the bottom of
tank 40.
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Referring now to one specific example, the pump 10 is selected to have a
flow capacity of 20,000 U.S. gallons per hour at a 75 foot head (water).
In the above described arrangement, various valves can be incorporated into
the system at different points for closing different sections as desired for
maintenance or other purposes.
The apparatus and method of the present invention are particularly useful in
drilling , operations where clays such as bentonite, which are used in such
operations, create site problems. With the apparatus and method of the present
invention, site problems are reduced or eliminated by recovery as opposed to
having the mud come to the surface at the drilling site and flood the work
area.
The method and apparatus of the present invention can be used in combination
with existing drilling equipment and techniques, to thereby provide a more
effective
and environmentally acceptable solution to the problems facing this field. By
recovery of the bentonite, greater economy can be achieved and the cost of
disposal of spent mud at a site is reduced. Recovery of the spent mud for
further
use provides further economic advantages.
In carrying out the method of the present invention using the arrangement
described above, circulation of the recovered material through the system may
be
carried out for relatively brief times up to more extended times as required
or
desired. Thus, given the type of equipment described cycling times of 5 to 10
minutes, e.g. typically 7 minutes, may be used. In the method, using the
outlet
arrangement described above, as the fluid is off-loaded, more material is
still being
circulated and filtered/sheared. It should be noted that with typical drill
mud or
powders, the circulation, drilling, filtering and nozzle effect makes the
resulting
product "cream" or fluff up, which is a desirable benefit since less raw
product will
be required. Still further, as the raw product is introduced into the hopper
or shelf
loading port, given the arrangement contemplated by this invention, will be
broken
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down from the nozzle force and admixed with the material in the tank which is
being recirculated.
Although embodiments of the invention have been described above, it is not
limited thereto and it will be apparent to those skilled in the art that
numerous
modifications form part of the present invention insofar as they do not depart
from
the spirit, nature and scope of the claimed and described invention.
