Patent Application
20110278240
1. Field of Invention
This invention relates generally to processing of a feedstock and more particularly to a pumpbox for receiving a hydrocarbon feedstock.
2. Description of Related Art
Hydrocarbon feedstocks are generally viscous and may be entrained with other components such as rock, sand, clay and other minerals. As a result, such feedstocks require processing to separate useful hydrocarbon products from residue before transport and refining.
One example of a hydrocarbon ore deposit is the Northern Alberta oil sands, which comprises about 70 to about 90 percent by weight of mineral solids including sand and clay, about 1 to about 10 percent by weight of water, and a bitumen or oil film. The bitumen may be present in amounts ranging from a trace amount up to as much as 20 percent by weight. Due to the highly viscous nature of bitumen, when excavated some of the ore may remain as clumps of oversize ore that requires sizing to produce a sized ore feed suitable for processing. The ore may also be frozen due to the northerly geographic location of many oil sands deposits, making sizing of the ore more difficult. The sized ore feed is typically processed by adding water to form a slurry in a location proximate to the ore deposit, and the resulting slurry is hydro-transported through a pipeline to a processing plant, where the slurry forms the feedstock for a processing plant that separates hydrocarbon products from the sand and other minerals.
Low specific gravity hydrocarbons such as bitumen froth may be separated from sand and water, which generally have higher specific gravity, by various gravity separation processes. There remains a need for improved processes and apparatus for treating heavy hydrocarbon feedstocks.
In accordance with one aspect of the invention there is provided a pumpbox apparatus. The apparatus includes a reservoir volume having a first inlet for receiving a feedstock stream and a second inlet for receiving a water stream, the reservoir volume being in communication with a discharge outlet disposed to discharge accumulated liquid from the reservoir volume. The reservoir volume is operable to accumulate the feedstock stream and the water stream to a first liquid level in the reservoir volume while withdrawing a discharge stream through the discharge outlet to cause a flow of liquid through the pumpbox. The first inlet is located above the second inlet and defines a first flow velocity region between the first inlet and the second inlet and a second flow velocity region between the second inlet and the discharge outlet. The first flow velocity is lower than the second flow velocity to facilitate flotation of a low specific gravity portion of the feedstock through the first region toward an upper surface of the liquid accumulated in the reservoir volume. The apparatus also includes a collector for collecting at least a portion of the low specific gravity portion from an upper surface of the accumulated volume when the first liquid level is above the first inlet.
The apparatus may include a controller for controlling a flow rate through the discharge outlet to maintain the first liquid level at a level between the first inlet and a high liquid level, the high liquid level being a desired maximum operating level for the reservoir volume.
The collector may be operably configured to collect at least a portion of the low specific gravity portion from an upper surface of the accumulated volume when the first liquid level reaches a high liquid level.
The collector may include a launder having an inlet disposed in the reservoir volume at the high liquid level for receiving an overflow of the low specific gravity portion from the reservoir volume.
The reservoir volume may be selected to maintain a retention time of feedstock and water in the pumpbox in the range of about 30 seconds to about several minutes at an expected average flow rate of the feedstock stream and the water stream. In one arrangement, the retention time is about 1 minute.
The apparatus may include a discharge pump in communication with the discharge outlet for withdrawing the discharge stream from the discharge outlet.
The discharge pump may be operably configured to discontinue operation when the liquid level reaches a low liquid level.
The apparatus may include a controller operably configured to control operation of the discharge pump in response to receiving a liquid level signal representing an accumulation level of liquid in the reservoir volume.
The feedstock stream may include bitumen. In one embodiment, the feedstock stream comprises bitumen froth. In another embodiment, the bitumen froth is in the form of an aerated froth. In another variation, the feedstock stream comprises bitumen froth in the form of a highly aerated bitumen froth. Highly aerated bitumen froths tend to float fast. Advantageously, in one aspect of the invention, the vessel is operative to selectively separate out such a fast floating aerated bitumen froth.
The feedstock stream may include water and solids.
The water stream may include a re-circulated water stream.
The re-circulated water stream may include residual bitumen and solids.
The second inlet may be disposed to cause solids that settle out of the accumulated liquid volume to be dispersed toward the discharge outlet for discharge in the discharge stream.
The second inlet may be oriented to direct the water stream received at the second inlet generally towards the discharge outlet.
The pumpbox may include a base having portion that may be inclined to direct solids that settle out of the accumulated liquid volume toward the discharge outlet for discharge in the discharge stream.
A density of the discharge stream may be between about 122×101 and about 128×101 kg/m3.
The flow velocity in the first flow velocity region may be less than about 5×10−2 meters per second.
In accordance with another aspect of the invention there is provided a pumpbox apparatus. The apparatus includes a reservoir volume having a first inlet for receiving a feedstock stream and a second inlet for receiving a water stream, the reservoir volume being in communication with a discharge outlet disposed to discharge accumulated liquid from the reservoir volume. The reservoir volume is operable to accumulate the feedstock stream and the water stream to a first liquid level in the reservoir volume while withdrawing a discharge stream through the discharge outlet to cause a flow of liquid through the pumpbox. The first inlet is located above the second inlet and defines a first flow velocity region between the first inlet and the second inlet and a second flow velocity region between the second inlet and the discharge outlet, the first flow velocity being lower than the second flow velocity to facilitate flotation of a low specific gravity portion of the feedstock through the first region toward an upper surface of the liquid accumulated in the reservoir volume. The apparatus also includes provisions for collecting at least a portion of the low specific gravity portion from an upper surface of the accumulated volume when the first liquid level is above the first inlet.
The apparatus may include provisions for controlling a flow rate through the discharge outlet to maintain the first liquid level at a level between the first inlet and a high liquid level, the high liquid level being a desired maximum operating level for the pumpbox.
The provisions for collecting may include provisions for collecting at least a portion of the low specific gravity portion from an upper surface of the accumulated volume when the first liquid level reaches a high liquid level.
The provisions for controlling may include provisions for controlling a flow rate through the discharge outlet to maintain a retention time of the feedstock stream and water stream in the reservoir volume of about 1 minute.
The apparatus may include provisions for causing solids that settle out of the accumulated liquid volume to be dispersed toward the discharge outlet for discharge in the discharge stream.
A density of the discharge stream may be between about 122×101 and about 128×101 kg/m3.
The flow velocity in the first flow velocity region may be less than about 5×10−2 meters per second.
In accordance with another aspect of the invention there is provided a method for regulating flow through a pumpbox having a reservoir volume in communication with a discharge outlet disposed to discharge accumulated liquid from the reservoir volume. The method involves receiving a feedstock stream at a first inlet of the reservoir volume, receiving a water stream at a second inlet of the reservoir volume, and accumulating the feedstock stream and the water stream to a first liquid level in the reservoir volume while withdrawing a discharge stream through the discharge outlet to cause a flow of liquid through the pumpbox. The first inlet is located above the second inlet and defines a first flow velocity region between the first inlet and the second inlet and a second flow velocity region between the second inlet and the discharge outlet, the first flow velocity being lower than the second flow velocity to facilitate flotation of a low specific gravity portion of the feedstock through the first region toward an upper surface of the liquid accumulated in the reservoir volume. The method further involves collecting at least a portion of the low specific gravity portion from an upper surface of the accumulated volume when the first liquid level is above the first inlet.
The method may involve controlling a flow rate through the discharge outlet to maintain the first liquid level at a level between the first inlet and a high liquid level, the high liquid level being a desired maximum operating level for the reservoir volume.
Collecting may involve collecting at least a portion of the low specific gravity portion from an upper surface of the accumulated volume when the first liquid level reaches a high liquid level.
Collecting may involve causing the low specific gravity portion to overflow into a launder having an inlet disposed in the reservoir volume at the high liquid level.
Withdrawing the discharge stream may involve operating a discharge pump in communication with the discharge outlet.
The method may involve discontinuing operation of the discharge pump when the liquid level reaches a low liquid level.
The method may involve controlling operation of the discharge pump in response to receiving a liquid level signal representing an accumulation level of liquid in the reservoir volume.
The method may involve causing solids that settle out of the accumulated liquid volume to be dispersed toward the discharge outlet for discharge in the discharge stream.
Causing solids that settle out of the accumulated liquid volume to be dispersed may involve directing the water stream received at the second inlet generally towards the discharge outlet.
A density of the discharge stream may be between about 122×101 and about 128×101 kg/m3.
The flow velocity in the first flow velocity region may be less than about 5×10−2 meters per second.
In accordance with one aspect of the invention there is provided a system for extracting bitumen from a feedstock. The system includes a pumpbox including a reservoir volume having a first inlet for receiving a feedstock stream including bitumen and a second inlet for receiving a water stream. The reservoir volume is in communication with a discharge outlet disposed to discharge accumulated liquid from the reservoir volume. The reservoir volume is operable to accumulate the feedstock stream and the water stream to a first liquid level in the reservoir volume while withdrawing a discharge stream through the discharge outlet to cause a flow of liquid through the pumpbox. The first inlet is located above the second inlet and defines a first flow velocity region between the first inlet and the second inlet and a second flow velocity region between the second inlet and the discharge outlet. The first flow velocity is lower than the second flow velocity to facilitate flotation of at least a portion of the bitumen through the first region toward an upper surface of the liquid accumulated in the reservoir volume. The system also includes a first hydrocyclone having a feed inlet, an overflow discharge outlet for producing a first product stream, and an underflow discharge outlet, the feed inlet of the first hydrocyclone being in communication with the discharge outlet of the pumpbox for receiving the discharge stream from the pumpbox. The system further includes a second hydrocyclone having a feed inlet, an overflow discharge outlet, and an underflow discharge outlet for producing a first tailings stream, the feed inlet of the second hydrocyclone being in communication with the underflow discharge outlet of the first hydrocyclone. The overflow discharge outlet of the second hydrocyclone is in communication with the second inlet of the pumpbox for providing the water stream to the pumpbox. The pumpbox further includes a collector for collecting at least a portion of the low specific gravity bitumen portion from an upper surface of the accumulated volume when the first liquid level is above the first inlet to produce a second product stream, the second product stream being combined with the first product stream to produce a system product stream.
The system may include a third hydrocyclone having a feed inlet, an overflow discharge outlet, and an underflow discharge outlet, the feed inlet of the third hydrocyclone being in communication with the underflow discharge outlet of the second hydrocyclone for receiving the first tailings stream, the third hydrocyclone being operable to produce a second tailings stream at the underflow discharge outlet of the second hydrocyclone, the overflow discharge outlet of the third hydrocyclone being in communication with the feed inlet of the second hydrocyclone to provide an additional feed to the second hydrocyclone.
Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.
In drawings which illustrate embodiments of the invention,
Referring to
The first inlet 104 is located above the second inlet 106. In this embodiment the first inlet 104 is in communication with a feed conduit 105, which is receives the feedstock stream, and directs the stream to the first inlet 104. The pumpbox apparatus 100 is shown in side schematic view in
The flow through the first and second flow velocity regions 144 and 146 is generally in a downwards direction and in one embodiment where the feedstock stream comprises bitumen, the first flow velocity is less than about 5×10−2 meters per second, which permits a fast rising bitumen portion to float upwardly in the reservoir volume 102. Referring back to
In the embodiment shown in
In the embodiment shown in
In this embodiment, the apparatus 100 also includes a liquid level sensor 170 and an opening 172 in a sidewall 174 of the pumpbox, which permits sensing of the first liquid level in the reservoir volume 102. The level sensor 170 includes an output 176 for producing a level signal representing a liquid level in the reservoir volume 102. The apparatus 100 further includes a controller 180 having an input 182 for receiving the level signal from the output 176 of the level sensor 170. The controller 180 also includes an output 184 for producing the pump control signal for controlling operation of the pump 160. In one embodiment, the control signal received at the input 166 of the pump 160 may be an analog signal that controls a speed of the pump, and thus the discharge flow rate through the discharge outlet 108. In other embodiments, the control signal may be a signal having one of two states, including a first state for causing the pump 160 to operate, and a second state for causing the pump to discontinue operation.
Referring back to
The feedstock stream received at the first inlet 104 may be an oil sand slurry including mineral solids such as sand and clay, water, and a bitumen froth. Preferably, the feedstock stream includes a highly aerated bitumen froth. Highly aerated bitumen froth tends to float fast. Advantageously, in one aspect of the invention, the pumpbox apparatus is operative to selectively separate out such a fast floating aerated bitumen froth.
In one embodiment the upstream oil sand flow rate of an oil sand feed may be in the range of about 1000 and about 6000 tonnes per hour. The oil sand feed is diluted with water (e.g. process water) to produce a slurry having densities in the range of about 1400 kg/m3 to about 1650 kg/m3, which is received at the first inlet 104. The water stream received at the second inlet 106 may be re-circulated process water, which may include dispersed solids and at least some residual bitumen.
During operation of the pumpbox apparatus 100, the feedstock stream and the water stream accumulate in the reservoir volume 102 while the controller 180 monitors the liquid level signal produced by the level sensor 170. When the first liquid level reaches the low liquid level (indicated as LLL in
Q
D
=Q
1
+Q
2 Eqn 1
where QD is the volumetric flow rate through the discharge outlet 108, Q1 is the volumetric flow rate in the first region 144, and Q2 is the volumetric flow rate through the second region 146. Assuming a downwardly vertical flow, the volumetric flow rate in the first region 144 may be written as:
Q
1
=Av
1 Eqn 2
where A is the cross-sectional area of the reservoir volume 102, v1 is the flow velocity in the first region 144. Rearranging and substituting Eqn 2 into Eqn 1 gives:
Q
2
=Q
D
−AV
1 Eqn 3
For example, at a discharge rate of 2000 m3/hour through the discharge outlet 108 in a vessel having a cross-sectional area of 8 m2, in order to maintain a velocity v1 of 5×10−2 meters per second, the flow rate through the second inlet 106 should be about 560 m3/hour. Under these conditions a velocity v2 in the second region 146 would be about 7×10−2 meters per second. Advantageously, the reduced first flow velocity v1 in the first region 144 facilitates flotation of the low specific gravity portion of the feedstock through the first region 144 to the upper surface 148. Equations 1-3 above are derived under assumption of vertically downward flow. In practice, flow paths through the apparatus 100 will have portions that are not vertically downward. It should thus be appreciated that for accurate calculation the above analysis would need to be applied to actual flow paths through the apparatus.
In the embodiment shown, collection of the low specific gravity portion of the feedstock that floats to the upper surface 148 occurs when the first liquid level in the reservoir volume 102 reaches the level of the overflow inlet 112 of the collector 110. The overflow inlet 112 therefore defines a high liquid level (HLL) for operation of the pumpbox apparatus 100. Generally, while it may be desirable to always operate the pumpbox apparatus 100 at the HLL in order to facilitate continuous collection of the low specific gravity portion of the feedstock, in practice variations in flow rate of the feedstock stream through the first inlet 104 would necessarily result in deviations from HLL that would require periodic intervention by an operator to adjust the discharge flow rate QD and/or the flow rate Q2 of the water stream. Practically, the operator would seek to maintain the first liquid level in the reservoir volume 102 between a normal liquid level (NLL) located at or above the first inlet 104 and the HLL. The NLL assumes liquid densities are about a nominal fluid density. Aerated bitumen froth, due to the air content, has a lower density hence a higher level than the nominal fluid. Aerated bitumen froth may have a density ranging from about 600 kg/m3 to about 1000 kg/m3.
While the first liquid level is maintained between NLL and HLL and the velocity v1 is maintained below less than about 5×10−2 meters per second, favorable conditions for flotation of the low specific gravity portion of the feedstock exists and bitumen should accumulate at the upper surface. When the first liquid level is above NLL but below HLL, bitumen may accumulate, but would not be collected. Accumulated bitumen is collected when the various flows permit the first liquid level in the reservoir volume to rise to the HLL. In one embodiment the discharge pump 160 is operated to maintain the first liquid level at an average liquid level of about 75% of the vertical distance between NLL and HLL above the NLL.
Referring to
In general, hydrocyclones operate by receiving a tangentially oriented flow at the feed inlet and a resulting circumferential flow transports heavier solid particles outwardly towards the walls of the hydrocyclone allowing lower specific gravity components and a portion of the water to be extracted as an overflow stream at the overflow outlet. The solids and a remaining portion of the water exit the hydrocyclone at the underflow outlet. Suitable hydrocyclones for the cyclone separation stages include those manufactured by FLSmidth Krebs of Tucson Ariz., USA under the trademark gMAX®. Alternatively, Cavex hydrocyclones marketed by Warman International may be used.
The system 200 further includes the pumpbox apparatus 100 shown in
The first hydrocyclone 202 separates the feed received at the inlet 210 and produces a second product stream 230 of low specific gravity bitumen, water, and some fine entrained solids at the overflow outlet 212 and an underflow stream including solids, water, and a bitumen portion at the underflow outlet 214. The second product stream 230 is mixed with the first product stream 228 to produce a combined product stream 232 from the system 200, which may be further processed to separate the low specific gravity bitumen components from the water. In general mixing of the second product stream 230 and the first product stream 228 would occur in a conventional pumpbox.
The underflow at the outlet 214 is fed to the feed inlet 216 of the second hydrocyclone 204. The second hydrocyclone 204 further separates the feed into a low specific gravity overflow stream including mostly water, some bitumen, and some fine solids. The overflow outlet 218 of the second hydrocyclone 204 is fed to the second inlet 106 of the pumpbox apparatus 100, and forms the water stream inlet for the pumpbox. The underflow stream produced by the second hydrocyclone 204 at the outlet 220 and a system process water feed 208 are combined to make up the feed to the inlet 222 of the third hydrocyclone 206. The combining of these streams may occur in a conventional pumpbox, for example.
The third hydrocyclone 206 further separates the feed into an overflow stream including mostly water, some bitumen, and some fine solids which is fed through the outlet 224 to the feed inlet 216 of the second hydrocyclone 204. The underflow stream produced by the third hydrocyclone 206 at the outlet 226 forms a tailings stream 234 for the system 200. The tailings stream 234 may be further processed or diverted to a tailings pond for treatment. The feedstock thus flows serially through the first, second, and third hydrocyclones 202, 204, and 206, while the system process water feed 208 flows through the third hydrocyclone, to the second hydrocyclone, and through the pumpbox apparatus 100 to the first hydrocyclone. The system process water 208 is thus generally counter to the feedstock flow through the system 200, which serves to improve recovery of bitumen from the feedstock.
The reservoir volume 102 of the pumpbox apparatus 100 provides a capacity for buffering the flow of feedstock to the first hydrocyclone 202, thereby facilitating operation of the hydrocyclones at a desired steady-state flow rate. In one embodiment the cross sectional dimension of the reservoir volume 102 is about 7.3 meters by about 7.3 meters and the capacity of the pumpbox is selected to accommodate flows of between about 1400 kg/m3 to about 1650 kg/m3 with a residence time of about 30 seconds to about several minutes. For illustrative purposes, in one arrangement, the retention time is about 1 minute. Advantageously, the pumpbox apparatus 100 further facilitates collection of a bitumen portion, in the form of aerated bitumen froth, that readily floats to the surface of the accumulated liquid in the reservoir volume 102. The first, second, and third hydrocyclones 202, 204, and 206 thus operate on feed streams having bitumen requiring more aggressive processing to separate low specific gravity bitumen from the solids.
Advantageously, in the event of a failure of a pump, such as the pump 160 shown in
In other embodiments, the configuration of the system 200 may be changed to suit a particular feedstock. For example, where it is desired to process a feedstock having a lower portion of solids, the third hydrocyclone 206 may be omitted, in which case the system process water may be provided to feed inlet 216 of the second hydrocyclone 204, and the underflow 220 of the second hydrocyclone forms the tailings stream for the system 200.
The pumpbox apparatus 100 may also be used in other applications that generally require blending of two or more streams having components of different specific gravity and where it is desired to collect a low specific gravity portion that readily floats upwardly within the accumulated liquid.
While specific embodiments of the invention have been described and illustrated, such embodiments should be considered illustrative of the invention only and not as limiting the invention as construed in accordance with the accompanying claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2689021 | Dec 2009 | CA | national |
