CA2164925A1 - Method and apparatus for the size reduction of and preparation of a slurry from a solid material - Google Patents

Abstract

An apparatus and method for sizing a solid and preparing from it a slurry, typically of a mineral ore, such that it will have a consistent density and be in a continuous stream, suitable for hydrotransport (slurry pipelining) and/or subsequent processing.

Description

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1. Field of the Invention.
This invention relates to a method and apparatus for size reduction and preparation of a slurry from a solid material in a continuous process.

2. Prior Art.
A search of the patent literature has revealed a number of patents which pertain to the production of slurries of coal. These are typified by the following documents:

U.S. Patent Documents 4,850,700 Markus, et al 88:05:24 4,753,660 Kellerwessel, et al 86:03:17 Canadian Patent Documents 1,200,696 Nakaoji, et al 86:02:18 1,200,235 Naka, et al 87:05:05 The focus of such patents dealing with the production of coal slurries, usually for the purpose of generating a fuel, is to ensure a coal particle size that will be small enough to generate as high a total solids content as possible whilst maintaining the slurry viscosity within the pumpable range. A secondary requirement is to ensure that the solid particles do not settle, either during transportation or storage due to the effects of gravity alone or via an agglomeration process initiated by the surface forces on the coal particulates. This latter effect is normally avoided by the addition of (usually) an organic chemical which will act to modify the particle surface forces. As such, the patents tend to be insensitive to the physical process of comminution but, rather, are concerned with the nature and addition of the surface energy modifying species. As such they fall ~ 2164925 `~ , outside of the area of interest of the current invention.
Canadian Patent 1,035,394 (Parkes and Hart, 78/07/25) describes an apparatus for the treating and conveying of hydraulically mined aggregate. This process, for use underground, uses some of the generic components described in the current specification, but, due to the specific application, is tied irrevocably to a hydraulic mining operation and as such would be unable to accept a dry feed. By the same token, it would be unable to enjoy many of the other benefits offered by the current invention, such as the ability to blend ores.
Thus we believe the current invention to be novel and practically useful for the comminution of, and preparation of a slurry from, a solid material, such as a mined ore (oil sand, coal, phosphate, etc.) in a continuous process using an apparatus which is compact enough to allow it to be relocatable.
BRIEF SUMMARY AND OBJECTS OF THE lNV~N-llON
The present invention therefore relates to an apparatus and method for sizing a solid and preparing from it a slurry, typically of a mineral ore, such that it will have a consistent density and be in a continuous stream, suitable for hydrotransport (slurry pipelining) and/or subsequent processing. The invention is especially suitable for use in the mining, transportation and processing of oil sand (tar sand) but should also be useful in the recovery of other minerals, such as phosphate, coal, etc. or any other materials that are usefully transported as a slurry.
In a preferred form of the invention the ore is fed to an ore sizer, water from several nozzles mixes with it, and as the mixture passes between through the rolls of the sizer, not only is the ore reduced in size and comminuted but a slurry begins to form. This ore/water mixture then falls onto a screen. Additional nozzles are positioned to provide water sprays (or recycled slurry sprays) to help . 2164925 .~

the mixture pass through the screen and any oversize material to be rejected. The screen openings are chosen based on the ore, the slurry pump, and the pipeline design, such that the screen will remove oversize material effectively and efficiently and allow the slurry to pass through without fear of screen blinding.
Once having passed through the screen, the slurry is directed to a pumpbox from where it is subsequently withdrawn, by a suitable pump, for transportation to the process plant via a conventional slurry pipeline. The pumpbox, may or may not contain a recirculating system, depending upon the nature, density and needs of the slurry.
The apparatus is of such a size and design that it is movable and can thus be transported to the most opportune location for use. As conditions change, it can be subsequently relocated to ensure continued mining and transportation efficiencies as dictated by the overall operation.
Design of the apparatus and method are such that whilst the feed to the equipment may be continuous (e.g.
by conveyor belt) or discontinuous (e.g. by truck or shovel), the output will be continuous and of a relatively consistent nature.
Through manipulation of the feed rates of both ore and water, it is possible to effect control over the density of the output slurry and hence to offer an additional degree of control to the process operations downstream.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 presents a cross-section view of one embodiment of the invention which would typically be used for the sizing of and preparation of a slurry from oil sand (tar sand);
Fig. 2 presents a plan view of a typical layout of the major components of the apparatus and includes the ore delivery system and surge piles;
Fig. 3 is similar to Fig. 1 and depicts another embodiment in which waste hot gases can be introduced into the unit to allow them to be entrained in the slurry and to offer downstream assistance with floatation based separation processes.
DETATT~Rn DESCRIPTION OF THE PREFERRED EMBODIMENT
The apparatus of the presently preferred embodiment is one which would be used in the recovery of oil sand (tar sand). The central unit is a conventional or modified commercial ore sizer 10, or conceptually similar machine. This is depicted in the drawings as comprising a modified conventional two roll (12, 14) sizer which can be set to produce an underflow suitable for subsequent transportation and/or processing. Rolls 12, 14 are disposed between spaced vertical side walls 15, 17 (Fig.
1) and opposed machine end walls (Fig. 2). Suitable machines would be those manufactured by MMD or Krupp (or other) which would typically have a ring diameter of 1600 mm and which would rotate with a shaft speed in the range of 10 to 30 r.p.m. The nip width between the two rolls will be selected dependent on the type of ore and the degree of comminution desired as is well known in the art generally. In most designs the rings of the rolls 12, 14 are fitted with three or four "teeth" which allow the larger lumps in the feed to be gripped and pulled into the crushing nip of the sizer. A breaker bar 16 is positioned just below the nip of the rolls 12, 14 in well known fashion. The length of the rolls 12, 14 is chosen in accordance with the desired capacity or throughput.
Commonplace details such as the roll mountings and drive train are not shown.
A major modification to the sizer comprises manifolds 18, 20 positioned above the rolls 12, 14 and co-extensive therewith such as to introduce water, which in the case of oil sand, will have been preheated into the desired , 2l64s2s temperature range, (40C to 95C), at a pressure in excess of 25 psi. The manifolds 18, 20 are typically equipped with a number of nozzles which would normally be 50 mm in diameter and at 300 mm to 450 mm centers. The water is 5 thus caused to impinge upon and to mix with the solid incoming feed and to pass, along with it, through the nip of the sizer rolls 12, 14.
Solid feed to the sizer 10 is most effectively provided by an all-metal pan feeder 22 which draws the material from a hopper 24 which is skid (25) or crawler mounted and which is typically positioned into a recess or shell in a custom built reinforced earthwork, movable cast concrete wall or mining high wall 26. The pan feeder speed is controlled to provide the required rate of feed 15 to the sizer. The angle at which the pan feeder leaves the hopper will be a function of the ore being handled. In the case of oil sands, it will be 12 to 18 from horizontal. The importance of the angle of the pan feeder is related to the propensity of the feed ore to "roll"
20 backwards into the hopper and to the propensity of the ore "to" arch in the hopper.
Feed to the hopper 24 can be by any of the commercially viable methods open to the mining industry.
It can be either continuous or intermittent, but should be 25 matched as nearly as possible to the output rate of the unit. In the case of oil sands, the preferred method would be to employ haul trucks which are loaded by a shovel, loader, or by other means as described hereafter.
After the ore and water mixture passes through the sizer, it falls onto a series of inclined impact plates 28, 30 located below the sizer rolls 12, 14 which assist in further breaking any agglomerations of feed material.
These impact plates 28, 30 which, like many other components, are typically fabricated from an abrasion 35 resistant structural steel, are washed by water from nozzle-carrying manifold 32 supplied with pressurized 21 6492~

water as before and located generally above the impact plates as shown in Fig. 1. An important aspect of the geometry of the sloping impact plates 28, 30 is that they are positioned in a slightly overlapping fashion as to allow the feed to be introduced to the primary screen 34 with a minimum of impact. This feature is important in both reducing wear of the screen and in reducing blinding of the screen by partially processed ore.
The primary screen 34 located below impact plates 28, 30 defines screen openings which, in the case of oil sands, are of typically 2.5 inch by 2.5 inch size.
Selection of the screen and particularly the screen opening size will be dictated by the material being processed and by the specifications of the pumps and pipe used to transport the final slurry. The screen 34 extends the full length of rolls 12, 14 and is sloped at an angle from the horizontal sufficient as to allow the oversize material to roll or slide sideways beneath sidewall 15 into the secondary sizer 44 to be described hereafter.
As the mixture moves toward the screen 34 it continues to be subjected to sprays of (hot) water from the manifold 32 as mentioned above. These sprays not only assist in controlling the ultimate slurry density but also provide additional mechanical energy which will continue the comminution of the ore and assist in ensuring that the maximum proportion of the feed will pass through the screen 34 on the first pass. Additionally, in the case of oil sand the added hot water will assist the separation of the bitumen from the sand.
Directly below screen 34 is a pump box 36 which again is co-extensive in length with sizer rolls 12, 14 and which has a sloping bottom wall 38 which leads downwardly into an elongated pump entrance port 40. The sloping bottom wall 38 inhibits stagnation of the slurry in the pump box and consequent settling out of solids therein.
Ore which has been reduced in particle size to less ~ ^
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than the dimensions of the primary screen openings, along with the bulk of the water, will pass through the screen 34 and into pump box 36. After passing the screen 34 the material can be considered a slurry. The slurry density at this stage should be close to the target density for pipelining and hence the slurry would typically comprise 60~ by weight of oil sand and 40~ by weight water.
Although the process per se is insensitive to slurry density there are some limitations resulting in competing requirements from transportation, processing and economic standpoints. A higher density is beneficial from economic and process viewpoints whilst too high a density can create significant problems with transportation. Thus the target density will be set by total system parameters and the feed streams (ore and water) will be adjusted to produce the overall optimum value. The requirements or ore particle size in the slurry are established by the principles of hydrotransport, namely that the maximum size of the solid particles should not be greater than 30~ of the diameter of the pipeline being used to transport the final slurry. Whilst there is no real minimum to the particle size that can be transported, the cost of size reduction increases as the mean particle size reduces.
Once in the pumpbox 36 the slurry can be optionally recirculated prior to being pumped out into the transportation pipeline via slurry pump 37. This assists in keeping the solids in suspension and offers benefits when recycling final slurry to assist in additional slurry preparation.
Oversize material that does not pass through the primary screen 34 is directed to either a reject pile 42 from where it is removed to a permanent dump, or to a secondary sizer 44 (as shown in Fig. 1). The secondary sizer, while similar in concept to the primary sizer 10 is, however, smaller with a pair of smaller diameter rolls 46, 48 rotating in opposite directions. This common g industry technique allows the secondary sizer 44 to act in a fashion similar to a feeder breaker, and to break the feed material against the outer plates 50, 52 of the unit.
These adjustments provide a finer pass size. As the wet 5 oversize feed is rejected and rolls or slides away from the primary screen 34 and is directed to the secondary sizer 44, it is again subjected to a sprays of (hot) water (or recycled slurry) from manifold 54 to assist in the sizing and slurry preparation. Materials passing through the secondary sizer 44 can be fed directly to the pump box 36 or alternately directed to a secondary screen (not shown) complete with an additional spray of hot water or recycled slurry. In the latter case, the underflow would be directed to the pumpbox and rejected material would be 15 disposed of.
The sizer 10 and associated components, including the pump box 36 are again skid or crawler mounted ( 37) to facilitate movement as mentioned previously.
In the preferred embodiment, the movable components 20 are placed in juxtaposition with, such as, a previously constructed movable precast concrete wall 26 as noted previously. The hopper 24 is designed so that haul trucks 56 capable of delivering between 85 and 360 tons of ore at a time can reverse against a concrete berm at the end of 25 it, and rear dump. If a second or subsequent haul trucks 56 should arrive at the unit prior to the previous load having been withdrawn from the hopper, then they can rear dump at the side locations 60 to create a surge pile.
This material can subsequently be fed to the hopper by use 30 of a loader, shovel, dozer, etc. 62. An added advantage of the surge pile(s) is that they allow the blending of ores to optimize the feed in terms of the critical component, e.g. in the case of oil sand recovery the ores from various mine locations could be blended to provide a 35 feed bitumen content that would offer optimized processing downstream.

-` 2164925 -The portability or movability of the system allows the maintenance of short haul truck journeys from the mining face to the sizer/slurry unit, effectively minimizing the costs for ore transportation. The location of the sizer/slurry unit can be changed as required to ensure that the haul distance will never exceed some predetermined maximum.
One major alternative is illustrated in Fig. 3 and relates to the addition, via entrainment, and consequent use of hot gases as a floatation aid for gravity separation processes, such as the Clark Hot Water Process for oil sands.
In this alternative an extra manifold 66 for use with hot gases is introduced immediately beneath a final sloping impact plate 68 located below the screen 34 such that the gases escaping from it are in close proximity to the slurry passing through the screen 34. The intimate contact of the gases with the slurry will achieve the entrainment of some (hot) gases in the slurry and these will assist in the final separation of the bitumen. (It should be noted that some of these gases may become dissolved in the water, and as a result have a small effect on the chemical properties of the water. This effect may have to be taken into consideration in those cases where process chemicals are added at the slurry preparation stage). The geometry for the manifold 66 used to introduce the hot gases can be very simple, comprising a simple horizontal slit of about 25 mm width, and running the full length of the manifold.
At the same location is an additional water manifold 70 having spray emitting nozzles to help the slurry move through the pump box 36 and avoid any buildup of particulates. The hot gases can consist of the exhaust from the diesel power plant being used to run the unit, or they may be obtained from other sources.
When using the apparatus described and shown in Fig.

2,64925 3, the ore and water feed rates are again chosen to produce the final slurry density required. Real time modifications to either the ore or water feed rate will permit changes to slurry density as required.
The heat exchangers, pumps and piping for supplying heated pressurized water to the several manifolds noted above have not been described in detail as they are all commonplace items readily available commercially.
Likewise the slurry pump and conduits and their connections to the manifolds to provide for the spraying of recirculated slurry (when desired) are not illustrated as, again, these components are commonplace details.
The whole of the unit is fabricated such that it is movable and can be relocated to the most opportune site for operations at any given time. This is facilitated by building the unit on skids, crawler units, or other suitable base to effect relocation.
In the claims which follow, the references to sprays of "water" are to be construed, where the context admits, as including entrained particles of ore, as when a portion of the slurry is being recycled and/or other desirable additives which may be employed, particularly in the case of oil sands, to enhance the separation of bitumen from sand.

Claims (23)

1. A method for the sizing of a mineral ore or like material and the preparation therefrom of a slurry comprising passing the ore through the nip defined by a pair of closely spaced parallel rotating rolls and wetting the ore with water as it moves toward the nip of the rolls such that the ore is comminuted and the particle size thereof reduced while simultaneously therewith a slurry begins to be formed.

2. The method of claim 1 wherein said step of wetting the ore comprises spraying the water on the ore as it moves toward said nip.

3. The method of claim 2 wherein the crushed ore and water mixture is permitted to fall downwardly from said nip while being subjected to further sprays of water to impart additional mechanical energy and to continue the comminution of the ore, with the ore and water mixture thereafter passing toward a primary screen adapted to pass slurry material below or equal to a selected particle size.

4. The method of claim 3 wherein said ore and water mixture is caused to fall into contact with one or more inclined impact plates while being subjected to said sprays of water prior to encountering said screen whereby to assist in further comminution of the ore and passage of a slurry thereof through said screen.

5. The method of claim 3 wherein ore slurry passing through said screen enters into a pump box and is thereafter pumped into a pipeline for transport to a remote location for further processing.

6. The method of claim 4 wherein ore slurry passing through said screen enters into a pump box and is thereafter pumped into a pipeline for transport to a remote location for further processing.

7. The method according to any one of claims 3 to 6 wherein oversize ore which does not pass said screen is passed through a secondary sizer and thereafter passed to said pump box after being reduced in particle size.

8. The method according to any one of claims 3 to 6 further comprising introducing heated gases into the slurry after passage through said screen to effect gas entrainment and improve slurry flotation.

9. The method according to any one of claims 1-6 wherein the ore comprises tar sand and wherein said water is preheated to temperatures of approximately 40°C. to 95°C.

10. The method according to claim 9 comprises introducing heated gases into the slurry to effect gas entrainment and improve slurry flotation.

11. The method of claim 10 including the step of pumping the slurry with its entrained gases through a pipeline to a further processing facility.

12. The method of claim 8 including the step of pumping the slurry with its entrained gases through a pipeline to a further processing facility.

13. Apparatus for the sizing of a mineral ore or like material and the preparation therefrom of a slurry comprising:
a pair of rotatable rolls defining a nip therebetween;

means for feeding ore into the nip of said rolls during rotation thereof; and means for wetting the ore with water as the ore moves toward said nip such that the ore is comminuted and reduced in particle size in the nip while simultaneously therewith a slurry begins to be formed.

14. Apparatus according to claim 13 wherein said means for wetting the ore comprises nozzle means for directing sprays of water onto the ore as it moves toward the nip.

15. Apparatus according to claim 14 wherein said apparatus is arranged such that, in use, the ore slurry being formed is permitted to fall downwardly from the nip, a primary screen being arranged to intercept the downwardly moving material and to pass material which is below or equal to a selected size, and further nozzle means being provided to subject the downwardly moving material to further sprays of water.

16. Apparatus according to claim 15 further comprising one or more inclined plates against which, in use, the downwardly falling ore material impacts while being subjected to said sprays of water and prior to meeting said screen whereby to impart mechanical energy and assist in the further comminution of the ore and passage of a slurry thereof through said screen.

17. Apparatus according to claim 15 including a pump box disposed below said screen to receive slurry passing therethrough and a slurry pump connected to said pump box to pump the slurry therefrom and pass it into a pipeline.

18. Apparatus according to claim 16 including a pump box disposed below said screen to receive slurry passing therethrough and a slurry pump connected to said pump box to pump the slurry therefrom and pass it into a pipeline.

19. Apparatus according to any one of claims 15-18 wherein said screen is sloped such that oversized ore material moves away from it, and a secondary sizer for receiving the over-sized material and reducing and comminuting the same and thereafter passing it to the said pump box.

20. Apparatus according to any one of claims 15 to 18 further including manifolds arranged to introduce heated gases into the ore slurry after passage through said screen to effect gas entrainment therein.

21. Apparatus according to any one of claims 13-20 when adapted for the processing of tar sands, and wherein means are provided for the preheating of the water to temperatures between 40°C. and 95°C.

22. Apparatus according to any one of claims 13-21 wherein said means for feeding ore comprises a pan feeder.

23. Apparatus according to claim 22 wherein said pan feeder is supplied from a hopper arranged such that loaded vehicles can deposit their loads therein.