Patent Application
20120104128
The present invention relates to mix boxes in general and more specifically to mix boxes useful in the preparation of uniformly mixed oil sand slurries.
The Athabasca Region of Alberta, Canada constitutes one of the largest deposits of oil sand in the world. The oil sand is first mined at a mine site and then transported to an extraction plant in order to extract the bitumen. In recent years the preferred mode of transport of mined oil sand has been by way of a slurry pipeline. The oil sand is mixed with water to form a slurry that is pumped down a pipeline to the extraction plant.
One needs to provide a suitable means for slurrying the oil sand with water and entraining air to produce a slurry that is suitable for pumping down the pipeline and subsequent bitumen recovery. The as-mined oil sand contains a variety of lumps including rocks, clay and oil sand lumps. Therefore a mixer means is required that not only slurries the oil sand but also ensures that oversize lumps that are unsuitable for pumping and feeding into the pipeline are rejected. A typical aqueous slurry comprises the following: bitumen froth, sand, smaller lumps of oil sand, clay and/or rocks (between 0 and 2 inches in diameter) and larger lumps of oil sand, clay and/or rock (between 2 and 4 inches in diameter).
In U.S. Pat. No. 5,039,227, one mixer circuit for slurrying oil sand with water has been disclosed. In this mixer circuit, an oil sand stream is dropped from the end of a conveyor into a mixer tank. The mixer tank is open-topped, has a cylindrical body and conical bottom and forms a central bottom outlet. A swirling vortex of slurry is maintained in the tank and the incoming oil sand and added water is fed into it. Slurry leaves the tank through the bottom outlet, is screened using vibrating screens to reject oversize, and is temporarily collected in an underlying pump box. Some of the slurry in the pump box is withdrawn and pumped back through a return line to be introduced tangentially into the mixer tank to form the swirling vortex. The balance of slurry in the pump box is withdrawn and pumped into the pipeline.
A second-generation mixer circuit in the form of a vertically oriented stack of components, which also functions to slurry the oil sand with water, is disclosed in U.S. Pat. No. 5,772,127. As-mined oil sand is initially crushed, for example, by passing it through a set of double rolls. The crushed oil sand is then initially dropped from the end of a conveyor and is contacted in mid-air with a stream of water. The mixture drops into a downwardly slanted trough and the water and oil sand mixes as they move turbulently through the open-ended trough. The slurry is deflected as it leaves the trough and is spread in the form of a thin sheet on an apron. It is then fed over a primary screen, e.g., a vibrating screen, to reject oversize lumps. The screened slurry drops into a pump box. The rejected lumps are comminuted in an impactor positioned at the end of the primary screen. The comminuted lumps are then screened through a secondary screen to remove remaining oversize lumps and the screened comminuted lumps are also delivered into the pump box. The slurry in the pump box is withdrawn and pumped into the pipeline.
Both of the prior art mixer circuits routinely produce a slurry that contains lumps ranging from 0 to 4 inches in diameter. The slurry must then travel down a hydrotransport pipeline, where slurry conditioning or digestion takes place. Adequate conditioning is critical for good bitumen recovery in a downstream separation vessel and is especially important when extracting bitumen from low grade oil sand. Basically what conditioning means is that the larger oil sand lumps are digested/ablated/dispersed into smaller lumps and bitumen flecks coalesce and coat or attach to air bubbles. The lumps need to be dispersed in water to promote the release of oil droplets and the attachment of air. Conditioning also benefits from turbulent pipeline flow and is dependent upon the length of the pipeline, hence, the length of time that the slurry resides in the pipeline before reaching the separation vessel. The larger the oil sand lumps, the more time required to digest or ablate these lumps to release the bitumen flecks. Therefore if a slurry is routinely produced that contains large lumps, there will be a need for longer pipelines with more residence time to ablate the lumps.
Further, in the second-generation mixer circuit, a problem was encountered with respect to blinding and uneven wear of the primary screens. The mixing of the crushed oil sand and water did not result in uniformly mixed oil sand slurry, in that portions of the oil sand slurry deposited on the screen would be too dry, causing blinding, and portions of the slurry would be wetter, causing more wear on the screens.
Thus, it is desirable to have a mixer circuit that produces more uniformly mixed oil sand slurries having smaller oil sand lump sizes, resulting in better oil sand slurry conditioning, more even wear on screens and ultimately improved bitumen recovery.
The present invention relates to mix boxes in general and more specifically to mix boxes useful in the preparation of uniformly mixed oil sand slurries.
In one aspect of the present invention, a mix box for mixing oil sand and water to form a substantially uniformly mixed oil sand slurry is provided, comprising:
In another aspect, a mix box for mixing oil sand and water to form a uniform oil sand slurry is provided, comprising:
In another aspect, a method is provided for preparing an oil sand slurry, comprising:
In one embodiment, the mix box further comprises a sloped bottom end. In another embodiment, at least one shelf has at least one flow diverter positioned at its leading edge. In another embodiment, the shelves are profiled.
Referring to the drawings wherein like reference numerals indicate similar parts throughout the several views, several aspects of the present invention are illustrated by way of example, and not by way of limitation, in detail in the figures, wherein:
The detailed description set forth below in connection with the appended drawing is intended as a description of various embodiments of the present invention and is not intended to represent the only embodiments contemplated by the inventor. 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 invention may be practiced without these specific details.
With reference now to
The more uniformly mixed the oil sand and water is will result in an oil sand slurry having a consistent texture, i.e., a more uniform water ratio across the mix box exit (discharge outlet 27). One advantage of having such a thoroughly and consistently mixed oil sand slurry is that it flows onto on screen 30 and uniformly spreads across the entire width of the screen, thereby preventing “hot spots” of wear on the screen due to large amounts of unmixed oil sand landing thereon.
To promote as uniform mixing as possible, profiled shelves can be used. This can be seen in
To further enhance a uniform flow distribution onto screen 30,
With reference now to
Mix box 464 comprises two internal profiled, convex shelves, 466 and 470. In between the two profiled shelves 466 and 470 are downwardly slanting shelves 468a and 468b and below profiled shelf 470 are downwardly slanting shelves 472a and 472b. The orientation of the profiled shelves and the downwardly slanting shelves is such that the oil sand slurry is directed alternately outwardly towards the walls of the mix box 464 and then inwardly towards the center of the mix box 464. This lateral mixing results in a very uniformly mixed oil sand slurry. Oil sand slurry then exits the mix box 464 via discharge outlet 467 located at the bottom of mix box 464.
It was further discovered that the addition of trilateral pyramid-shaped flow diverters 450, as shown in
Prototype mix boxes for preparing oil sand slurry from dry pre-crushed oil sand and water were constructed using three different shelves: (1) non-profiled shelves (“Original”); (2) profiled shelves (“Shelf Profiles”), as shown in
It can be seen from
It can be further seen from
Prototype mix box was designed as shown in
It can be seen in
From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention, and without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions. Thus, the present invention is not intended to be limited to the embodiments shown herein, but is to be accorded the full scope consistent with the claims, wherein reference to an element in the singular, such as by use of the article “a” or “an” is not intended to mean “one and only one” unless specifically so stated, but rather “one or more”. All structural and functional equivalents to the elements of the various embodiments described throughout the disclosure that are known or later come to be known to those of ordinary skill in the art are intended to be encompassed by the elements of the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims.
This application claims priority to U.S. provisional patent application No. 61/409,830, filed Nov. 3, 2010.
| Number | Date | Country | |
|---|---|---|---|
| 61409830 | Nov 2010 | US |
