Classifying – separating – and assorting solids – Precedent preparation of items or materials to facilitate...
Reexamination Certificate
1998-02-10
2001-01-09
Nguyen, Tuan N. (Department: 3653)
Classifying, separating, and assorting solids
Precedent preparation of items or materials to facilitate...
C209S010000, C209S315000, C209S913000, C198S670000
Reexamination Certificate
active
06170667
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to an apparatus and method for the preparation of slurries from mixtures of liquids and solids. The invention is particularly intended for the preparation of slurries that incorporate waste materials, for injection into geological formations. The invention may also be adapted for the preparation of other types of slurries, for other uses.
BACKGROUND OF THE INVENTION
Slurries comprised of suspensions of solids within a liquid carrier, with or without the presence of other liquids such as waste oils, are prepared for a variety of applications that require a continuous slurry formation process. The present applicant's co-pending application Ser. No. 08/713,358 relates to an apparatus and method for the disposal of wastes by injection of wastes in slurry form into geological formations. The slurry is prepared on the surface for this application with apparatus designed to produce a generally continuous stream of slurry. Typical wastes that may be slurrified for this process include:
oily sand from petroleum industry operations, as well as waste drilling fluids and drill chips from well drilling operations and oily slop and sand and residues from tank-bottom clean-outs;
soil contaminated with toxic materials such as PCB, heavy metals, cyanide compounds, hydrocarbons, naturally-occurring radioactive wastes, etc.;
dredging wastes;
municipal sewage sludge from which the organic wastes have been largely decomposed;
waste plastics, glass, and other solid materials;
fly ash, clinker or other residue from combustion of wood, coal or municipal wastes;
flue gas desulphurization sludges as well as recaptured particulates from smoke or emission abatement processes, whether in solid or aqueous suspension form;
high solids content sludges and residues from petroleum refining, including high ash content coke, heavy oil residues and removed solids.
Typical existing slurry-making systems employ a batch processing method, wherein slurry is generated and discharged in a series of discrete batches. This approach is not desirable for generating the high volumes of slurry that is preferred for subterranean injection applications, nor does it permit an injection pump to operate on a continuous basis. The continuous production of a steady stream of slurry is important to achieve optimal pump efficiency and to minimize pump wear.
As well, apparatus for producing slurry for use in an injection process as described in co-pending application Ser. No. 08/713,358 must meet several design criteria in order to dispose of a substantial volume of wastes at a high rate:
delivering prepared slurry on a continuous basis at a surface pressure of between 6-15 Mpa;
disposition of slurry injected at a rate of between 1.5 and 2.0 m
3
/min. and 1000 m
3
/day;
slurry composition with a granular solids content between 15-40% and real-time waste concentration and slurry density control to maintain density between 1100 and 1500 kg/m
3
;
processing of 200-400 m
3
/day of granular wastes;
ability to accept a variety of solid materials, including slop and sand.
The operating parameters of a slurry forming apparatus for use in a waste injection system require equipment capable of preparing a relatively granular, highly viscous slurry at relatively high rates and pressures and on a continuous basis. Preferably, the slurry formation apparatus for this application should provide the following features:
a) relative ease of handling of waste material;
b) screening of granular waste material on a continuous basis to remove oversize or undesirable material;
c) a real-time monitoring apparatus to monitor and record injection parameters;
d) variable speed controls linked to the monitoring apparatus to control the various slurry-forming components and maintain consistent slurry quality and delivery rate;
e) a system capable of relatively rapid set-up and disassembly;
f) slurry formation equipment capable of shearing highly viscous material to increase slurry mobility and injectivity, maintaining slurry consistency within a relatively small range, and being capable of handling relatively large amounts of waste material, in the range of at least 100 m
3
/day, which when incorporated within a slurry may result in the formation of 1,500 m
3
/day slurry or more.
A further requirement of an apparatus designed to process sand or other abrasive materials is that the moving parts not be exposed to excess wear. This requirement particularly affects the material transport means within the system, which are in contact with the slurry or slurry substrate. These components should minimize the use of moving parts in contact with each other that are also in contact with the slurry mixture. As well, where the system is intended to provide slurry to a waste injection system, it is desirable to provide a dual slurry outlet, in order to permit the use of dual injection pumps to reduce wear on the individual pumps and minimize maintenance downtime of the system.
SUMMARY OF THE INVENTION
In light of the objectives outlined above, the present invention consists of an apparatus for the formation of a slurry having a predetermined consistency, on a generally continuous basis, by combining a carrier liquid, solids in granular form and optionally other liquids and solids. The apparatus achieves a continuous slurry formation by means of continuously performing one or more preliminary mixing operations of a carrier liquid and solid particulates prior to entry of the mixture into a main mixing tank wherein the particulates are mixed with a carrier liquid. This preliminary mixing stage permits the main mixing tank to perform the final steps of mixing, shearing and averaging, or adjusting of the slurry consistency. These functions may be performed on a generally continuous basis within a mixing/averaging tank that incorporates an effective shearing and mixing means.
In its broadest aspect, the apparatus consists of:
a) receiving means to receive solids in particulate form;
b) a transport/mixing assembly having an opening at a first end to receive material from the receiving means, at least one inlet to receive carrier liquid into the assembly, and transport/mixing means to continuously combine the solid material with the carrier liquid while transporting the mixture from the first end to a second end of the assembly;
c) a mixing/averaging tank adapted to receive the solid/liquid mixture from the transport/mixing assembly to perform a final mixing and averaging of the mixture to achieve a desired slurry consistency, and to discharge the finished slurry on a continuous basis.
The mixing/averaging tank is provided with one or more inlet means to direct additional carrier liquid into the slurry mixture. The inlet means may comprise a sprayer positioned to spray liquid at the surface of the slurry within the tank. The tank is provided as well with mixing and shearing means such as one or more augers to continuously mix and shear the slurry, and one or more outlet ports at the base of the tank to discharge the slurry.
The liquid inlet for introducing carrier liquid into the transport/mixing assembly comprises a separate inlet from the receiving means for receiving particulates. This permits the liquid to be introduced separately from and subsequent to the introduction of particulates. The liquid intake into the slurry mixing tank preferably also comprises a separate inlet from the inlet for receiving slurry particulates. This arrangement permits an efficient formation of slurry.
Preferably there is further provided particulate sizing means to eliminate oversized particles before the mixture enters the mixing/averaging tank. The sizing means may comprise a screen deck with single or multiple spaced apart screen layers, with means to shake or vibrate the screen deck to perform a screening operation. A stream of carrier liquid may be directed at the upper surface of the screen deck and/or between the spaced apart screen layers to introduce additional liquid to the mixture and assist in the screening operation. In one version, the s
Bilak Roman Anthony
Fundytus Darcey Dale
McFadden Fincham
Nguyen Tuan N.
Terralog Technologies U.S.A. Inc.
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