APPARATUS AND PROCESS FOR WET CRUSHING MINED OIL SAND

A slurry preparation tower is provided comprising an intake opening through which oil sand enters the slurry preparation tower; a first sizer device operative to comminute oil sand passing through the first sizer device to a first upper size threshold; a second sizer device operative to comminute oil sand passing through the second sizer device to a second upper size threshold, wherein the second upper size threshold is less than the first upper size threshold; a first solvent supply device for adding solvent to the oil sand prior to or during its comminution in the first sizer device; and a plurality of deflector plates positioned between the first sizer device and the second sizer device to assist in the mixing of the first comminuted oil sand and solvent.

FIELD OF THE INVENTION

The present invention relates to an apparatus and process for wet crushing mined oil sand to form a pumpable and pipelinable oil sand slurry without screening.

BACKGROUND OF THE INVENTION

Oil sand containing bitumen mined from the ground is generally slurried with a solvent such as water as part of an initial process for eventually removing the bitumen from the oil sand. Oil sand is a type of bitumen deposit typically containing sand, water and very viscous oil (the bitumen). When the oil sand deposit is located relatively close below the ground surface, the oil sand is often extracted from the deposit by mining. The oil sand is mined by excavating down through the ground surface to where the oil sand deposit occurs and removing oil sand from the deposit with heavy machinery.

Typically, this removal of the oil sand from the deposit is done with some of the largest power shovels and dump trucks in the work, with the power shovels removing shovel-loads of oil sand from the deposit and loading the collected oil sand onto conveyors to be carried away for further processing.

The viscous bitumen tends to hold the sand and water together causing the mined oil sand to contain lumps and chunks, some of which can be quite large. Because of the size of some of these pieces of mined oil sand, the mined oil sand is typically “pre-crushed” by running it through a preliminary crusher (often referred to as a “primary crusher”) to crush the pieces of oil sand to a suitable size for transport on a conveyor (i.e. conveyable size).

The pre-crushed oil sand is then transported by conveyor to a slurry preparation unit as known in the art where the pre-crushed oil sand is further processed to form an oil sand and water slurry.

The slurry preparation unit has to ensure that the pieces of oil sand in the oil sand and water slurry are of pumpable size before the slurry is directed to a pump box and pump to be pumped to the next step in its processing, for example, hydrotransporting the slurry in a pipeline for further conditioning. Therefore, oversize pieces of oil sand or other materials have to be prevented from being directed to the pump in order to obtain a pumpable, pipelinable oil sand slurry. There are at least two forms of slurry preparation units that have been used to form the oil sand and water slurry; slurry preparation units that use screening and more recent screen-less slurry preparation units.

Slurry preparation units that use screening typically comprise a vertically stacked series of components. The pre-crushed oil sand is initially fed into a mixing box where water is mixed with the oil sand to form the slurry. From the mixing box, the oil sand and water slurry is passed through some sort of screening device to remove oversize from the oil sand and water slurry. The slurry that passes through the screening device passes into a pump box where it is pumped to the next stage of the process. The rejected oversize that does not pass through the screening device is rerouted to a crusher to be comminuted and then added to a secondary mix box and again mixed with water to form a slurry before this slurry is passed through another screening device. The portion of the slurry that passes through this other screening device is then returned to the main slurry components. The oversize rejects that do not pass through the second screening device are treated as rejects and removed from the system. The removed rejects are typically eventually hauled away by trucks and dumped in a discard area.

Slurry preparation units that use screens have a disadvantage in that a portion of the oil sand passing through the slurry preparation units is rejected by the system. This rejection of a portion of the oil sand means that the bitumen in this rejected oil sand is lost, as it is not extracted at later process stages like the rest of the system. In some screening processes, the rejection rate can be as high as 8%. This rejection rate can add up to a significant amount of bitumen that is simply being thrown away. More recently, screen-less slurry preparation towers have been used such as the screen-less system described in U.S. Pat. No. 7,431,830 and Canadian Patent No. 2,480,122.

Screen-less slurry preparation towers form all of the oil sand and other materials entering the slurry preparation tower into a slurry and as such avoid rejects. In particular, essentially all of the oil sand that enters the tower is typically comminuted in one or more stages to a pumpable size while water is being added to it to form a slurry. This allows bitumen to be extracted from essentially all of the oil sand delivered to the slurry preparation tower, thereby essentially eliminating rejects.

However, the screen-less slurry preparation tower must be designed such that proper and sufficient mixing of crushed oil sand and water occurs to form pumpable oil sand slurry. Thus, there is a need for improved mixing in screen-less slurry preparation towers.

SUMMARY OF THE INVENTION

In an aspect, a slurry preparation tower is provided comprising in series an intake opening through which oil sand enters the slurry preparation tower; a first sizer device operative to comminute oil sand passing through the first sizer device to a first upper size threshold; a second sizer device operative to comminute oil sand passing through the second sizer device to a second upper size threshold, wherein the second upper size threshold is less than the first upper size threshold; a first solvent supply device for adding solvent to the oil sand prior to or during its comminution in the first sizer device; and a plurality of deflector plates positioned between the first sizer device and the second sizer device to assist in the mixing of the first comminuted oil sand and solvent.

In one embodiment, the plurality of deflector plates positioned between the first sizer device and the second sizer device includes at least one convex deflector plate and at least one concave deflector plates. It is understood, however, that the deflector plates can be uniplanar as well.

In one embodiment, a second solvent supply device is provided between the first sizer device and the second sizer device to further dilute the oil sand and solvent mixture. In one embodiment, the solvent is water.

In another embodiment, at least one deflector plate is also positioned between the intake opening and the first sizer device. In one embodiment, the at least one deflector plate is positioned above the first water supply device and is convex for dividing the oil sand feed into two streams. In another embodiment, the at least one deflector plate positioned between the intake opening and the first sizer device is positioned below the first solvent supply device.

In another aspect, a method of forming a pumpable oil sand slurry is provided comprising the steps of providing at least one conveyor for delivering the mined oil sand to a slurry preparation tower, the slurry preparation tower having a first sizer and a second sizer; adding a solvent to the oil sand prior to comminuting the oil sand in the first sizer to a first upper size threshold; mixing the comminuted oil sand and solvent that has passed through the first sizer by means of a plurality of deflector plates prior to comminuting the oil sand and solvent mixture in the second sizer to a second upper size threshold that is less than the first upper size threshold to produce the pumpable oil sand slurry.

In one embodiment, the pumpable oil sand slurry exits the slurry preparation tower into a pump box.

DESCRIPTION OF VARIOUS EMBODIMENTS

The detailed description set forth below in connection with the appended drawings is intended as a description of various embodiments of the present invention and is not intended to represent the only embodiments contemplated by the inventors. The detailed description includes specific details for the purpose of providing a comprehensive understanding of the present invention. However, it will be apparent to those skilled in the art that the present inventions may be practiced without these specific details.

FIG. 1is a schematic illustration of a slurry preparation tower50used to form an oil sand slurry ready for hydrotransport (pumpable oil sand slurry). Oil sand ore mined from an oil sand deposit is routinely first sized in a preliminary (or primary) crusher that reduces the size of the mined oil sand ore to pieces of conveyable size (pre-crushed oil sand ore). For example, pre-crushed oil sand ore may have an average size of 600 mm. Pre-crushed oil sand ore14is fed to a conveyor110where the pre-crushed oil sand ore14is transported along the conveyor110to a discharge end112of the conveyor110. At the discharge end112of the transport conveyor110, the pre-crushed oil sand ore14drops onto an apron feeder40positioned below the discharge end112of the conveyor110, with a first end42of the apron feeder40positioned over an intake opening55in the slurry preparation tower50.

The slurry preparation tower50has two comminuting stages implement with a first sizer52and a second sizer54. In one aspect, the first sizer52can include four (4) rotatable elements in the form of crusher rolls81having a generally cylindrical shape and positioned side-by-side, however, it is understood that any type of mineral sizer that is know in the art could be used for the first sizer52. Each of the crusher rolls81have a plurality of crusher teeth82to aid in comminuting the larger pieces of pre-crushed oil sand ore14. The crusher rolls81are spaced a set horizontal distance apart to form gaps between adjacent crusher rolls81. The size of the gaps determines the first upper size threshold the secondary sizer52will size oil sand passing through the first sizer52. As shown inFIG. 1, the four crusher rolls81comprise two pairs of oppositely rotating crusher rolls.

The pre-crushed oil sand14drops off the first end42of the apron feeder40and onto a deflector plate20, which may be convex in shape and thus splits the oil sand feed into two feed streams16,16′. Deflector plate20is located at or near intake opening55of slurry preparation tower50. Solvent supply device22is positioned below deflector plate20and is operative to spay a solvent such as water onto both feed streams16,16′.

In one embodiment, as shown inFIG. 2AandFIG. 2B, slurry preparation tower250may comprise first sizer252, second sizer254, and a serrated deflector plate220(also referred to as a serrated impact beam) located at or near intake opening255of the tower. The serrated deflector plate220presents to the incoming pre-crushed oil sand ore214an irregular surface due to projections221to assist in the fragmentation of the ore, thereby increasing the wettability of the ore when it is sprayed with a solvent (e.g., process water) from solvent supply device222. Thus, there is good exposure of the pre-crushed oil sand ore214to the solvent due to the increase in surface area of the ore. The serrated deflector plate220may also prevent build up of oil sand thereon. Finally, the serrated deflector plate220may provide protection to the solvent supply device222, which is positioned immediately below. The slurry preparation tower250may further comprise a second solvent supply device240. The oil sand slurry is then collected in a recycle mix box270, wherein a 1:1 ratio of fresh oil sand slurry and recycled oil sand slurry is pumped to a hydrotransport pipeline (not shown).

The wetted oil sand ore then falls on deflector plates24,24′, which are positioned below the solvent supply device22. Deflector plates24,24′ may be concave in shape in order to direct feed streams16,16′ into two feed streams18,18′ such that each feed stream drops in between the each pair of crusher rolls, respectively. It is understood, however, that deflector plates24,24′ can also be uniplanar.

The first sizer52comminutes the oil sand passing through the first sizer52to a first upper threshold size so that substantially all the pieces of oil sand that have passed through the first sizer52are no greater in size than the first upper threshold size. In one aspect, this first upper threshold size is approximately eight (8) inches so that substantially all of the pieces of oil sand that have passed through the secondary sizer52are eight (8) inches in size or less.

The second sizer54comminutes the oil sand passing through the second sizer54to a second upper threshold size. The second upper threshold size is smaller than the first upper threshold size. In this manner, the second sizer54reduces the size of the larger pieces of oil sand even more than the first sizer52. In one aspect, this second upper threshold size is approximately four (4) inches so that substantially all of the pieces of oil sand that have passed through the second sizer52are four (4) inches in size or less.

In one aspect, the second sizer54can include four (4) rotatable elements in the form of crusher rolls91positioned side-by-side, however, as previously mentioned, any type of mineral sizer known in the art could be used for the second sizer54. Each of the crusher rolls91have a plurality of crusher teeth92to aid in comminuting pieces of oil sand ore still present. However, the gaps between adjacent crusher rolls91are smaller than the gaps between adjacent crusher rolls81of the first sizer52, so that the second sizer54comminutes material to a smaller size than the first sizer54. Additionally, the crusher teeth92on the crusher rolls91may be smaller and there may be more crusher teeth92on a crusher roll91than the number of crusher teeth82on the crusher rolls81of the first sizer52. As shown inFIG. 1, the four crusher rolls91comprise two pairs of oppositely rotating crusher rolls.

Directly below the first pair of crusher rolls of the first sizer52is a deflector plate26and directly below the second pair of crusher rolls of the first sizer52is a deflector plate26′. Deflector plate26may be convex in shape to split the oil sand and solvent from the first pair of crusher rolls into two feed streams32,32′. Feed streams32,32′ are further mixed by means of deflector plate28and deflector plate30. Optionally, additional solvent such as water can be added to streams32,32′ by means of solvent supply device40. The mixed oil sand and solvent stream36now drops in between the first pair of crusher rolls of the second sizer54. Similarly, deflector plate26′ may be convex in shape to split the oil sand and solvent from the second pair of crusher rolls of the first sizer52into two feed streams34,34′. Feed streams34,34′ are further mixed by means of deflector plate28′ and deflector plate30. Optionally, additional solvent such as water can be added to streams34,34′ by means of solvent supply device40′. The mixed oil sand and solvent stream36′ now drops in between the second pair of crusher rolls of the second sizer54.

A pump box70is provided below the second sizer54so that oil sand slurry streams38,38′ that have passed through the second sizer54can drop into the pump box70and the oil sand slurry can be pumped by one or more pumps72to the next stage in the process. In one embodiment, the bottom of slurry preparation tower50is cone shaped, directing streams38,38′ to outlet96, which outlet may be connected to pump box70. In one embodiment, pump box70comprises a deflector plate98positioned beneath outlet96to further mix the oil sand slurry prior to pumping.

In operation, oil sand ore is discharged from the discharge end112of the conveyor110and onto the apron feeder40. In normal operation, the apron feeder40discharges the oil sand from the first end42of the apron feeder40through the intake opening55and drops it downwards towards the first sizer52. As the oil sand ore falls towards the first sizer52, a solvent, such as water, can be sprayed onto the falling oils sand ore using the first solvent supply device22, wetting the falling oil sand ore that contacts the first sizer52.

When the oil sand ore reaches the first sizer52, the oil sand ore is comminuted as it passes through the first sizer52to a size equal to or smaller than the first upper size threshold before the oil sand exits the first sizer52and drops towards the second sizer54.

Oil sand that has passed through the first sizer52falls downwards towards a plurality of deflector plates positioned between the first sizer52and the second sizer54. The deflector plates aid in mixing the oil sand and water that exits from first sizer52. Optionally, additional solvent, such as water, can be sprayed onto the falling oil sand and solvent from first sizer52using at least one second solvent supply device40,40′, thereby wetting the falling oil sand and solvent further. Further mixing occurs as the oil sand and solvent contact the deflector plates prior to passing through the second sizer54.

The second sizer54comminutes the oil sand to a size equal to or smaller than the second upper size threshold before allowing the oil sand to pass through the second sizer54.

Oil sand and solvent that has passed through the second sizer54drops into the pump box70positioned below the second sizer54where the oil sand and water slurry will be pumped by the one or more pumps72to the next stage of the bitumen extraction process for further processing.

In this manner, substantially all of the oil sand ore that is introduced into the slurry preparation tower50through the intake opening55exits the slurry preparation tower as an oil sand and water slurry to be transported to the next stage in its processing. All of the oil sand ore in the slurry has been reduced to a pumpable size and none of the oil sand ore is rejected from the slurry preparation tower to be hauled away and discarded.

The present invention makes good use of the elevation of the slurry preparation tower by integrating deflector plates which aid in the formation of pumpable oil sand slurry. Thus, the present invention provides a more vertically efficient layout without compromising mixing of oil sand slurry. Hence, by providing deflector plates on the walls of the slurry preparation tower between the first sizer52and second sizer54and/or below the roll gaps of the first sizer52, the flow is directed in an optimized manner to further stimulate slurry formation. It is understood, however, that other configurations of deflector plates in the space between the first sizer52and second sizer54can be used. Deflector plates can be any variety of shapes, for example, concave, convex, uniplanar, etc.