CA3014991A1 - Clay-based control of primary separation vessel in oil sands processing - Google Patents

Abstract

Various techniques are described herein for clay-based control of a primary separation vessel (PS). Analyzers can be used to determine a clay content parameter that is used to control operation of the PSV, for example by controlling the flow rate of dilution water that is added to the oil sands slurry before being fed into the PSV. Measuring clay content and adapting operation of the PSV based on a clay content parameter can thus be leveraged to facilitate processing lower quality oil sands ores and slurries with variable clay contents while maintaining target bitumen recovery levels.

Description

CLAY-BASED CONTROL OF PRIMARY SEPARATION VESSEL IN OIL SANDS
PROCESSING
TECHNICAL FIELD
[0001] The present technical field relates to operating a primary separation vessel (PSV) used to process oil sands slurries that include bitumen, water and clay material;
and more particularly to automated clay-based control methods for PSV
operations.
BACKGROUND

[0002] Higher clay contents in oil sands ore can be responsible for lower bitumen recovery rates, as clay is an undesirable component of the bitumen froth and interferes with bitumen separation mechanisms. High-clay oil sands ore can also result in additional volumes of tailings production and higher bitumen content in tailings. During separation processes, clay minerals can attach to bitumen and prevent attachment of bitumen to air bubbles for aeration and flotation. Clays have elevated active surface areas which can interact with other components of the slurry during separation and downstream processing of bitumen and tailings streams. Processing high-clay oil sands ore can indeed lead to reduced bitumen recovery and lower efficiency in terms of PSV
performance and overall oil sands processing.

[0003] Caustic soda has been added to oil sands slurry with high fines content so that the hydroxyl ions can attach to positively charged fine particulate mineral solids and inhibit attachment to the bitumen droplets. This leaves the hydrophobic bitumen free to attach to air bubbles, thereby improving bitumen recovery. Addition of surfactants, and other additives has also been performed to change physicochemical interactions between components of the oil sands slurry to facilitate bitumen extraction.

[0004] There is still a need for improvement in separation technologies for treatment of oil sands slurries, particularly for PSV separation of slurries with higher clay content.
SUMMARY

[0005] Various techniques are described herein for clay based control of PSV
operation. Analyzers can be used to determine a clay content parameter that is used to control operation of the PSV, for example by controlling the flow rate of dilution water that is added to the oil sands slurry before being fed into the PSV. Measuring clay content and adapting operation of the PSV based on a clay content parameter can thus be leveraged to facilitate processing lower quality oil sands ores and slurries with variable clay contents while maintaining target bitumen recovery levels.

[0006] Several potential implementations and features for clay-based control of a PSV
are described below, and include certain clay content analyzers, control strategies, and process configurations.
BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 is a process flow diagram showing automated control of a primary separation vessel (PSV).

[0008] Figure 2 is a process flow diagram of an oil sands processing operation that includes various analyzers.

[0009] Figure 3 is a process flow diagram of a primary extraction operation including a PSV with automated control.

[0010] Figure 4 is another process flow diagram of a primary extraction operation including a PSV with automated control.

[0011] Figure 5 is another process flow diagram of an oil sands processing operation with monitoring and adjustment of the process.

[0012] Figure 6 is a graph illustrating that clay-to-water ratio (CWR) was found to be an important variable in bitumen recovery in a PSV.

[0013] Figure 7 is another process flow diagram of a PSV with clay-based dilution control.
DETAILED DESCRIPTION

[0014] Enhanced operation of a primary separation vessel (PSV) that separates oil sands slurry into bitumen froth, middlings, and coarse tailings underflow, can employ a control strategy that adapts PSV operations based on clay content of the oil sands slurry feed. Measuring clay content of the slurry and using the measured clay content to adjust operating parameters of the PSV can facilitate maintaining high bitumen recovery levels.

[0015] In one example implementation, clay content of the oil sands slurry can be measured and, above a maximum clay threshold level or setpoint, dilution water can be added to the slurry such that the slurry feed introduced into the PSV has a clay content below the clay threshold or setpoint and thus within a suitable range for facilitating a target bitumen recovery level. In other implementations, the clay content of the slurry feed can be measured, and one or more operating parameters of the PSV can be controlled in response to the clay content measurements. Automated control of the PSV
in response to high detected clay content in the oil sands slurry can notably enhance bitumen recovery from the oil sands at high clay levels. The PSV control can be based on clay content directly or on a clay content indicator, such as clay-to-water ratio (CWR) of the slurry or clay-to-dilution water ration (CDWR).

[0016] At low clay levels in the oil sands slurry, PSV operation may not require or benefit significantly from control based on the clay content of the slurry feed. However, at high clay contents, it can be advantageous to adjust operation to reduce the clay content of the slurry feed within a desirable operating envelope. In addition, oil sands slurry that is fed to the PSV can have variable clay content that only periodically exceeds a high-clay threshold, and thus the automated control of the PSV based on the clay content can also be periodically activated in response to high-clay detection.
In other words, at low clay levels no active control is performed based on the clay content, but at high-clay levels the PSV is actively controlled in response to the measured clay content of the slurry. In some other situations, due to lower-grade oil sands ore that may be mined and supplied to a slurry preparation unit, the oil sands slurry can have high clay content that is consistently above the threshold level and thus continuous clay-based control of the PSV can be implemented.

[0017] In the context of this disclosure, "clay" can be understood in terms of composition, activity, and size. In particular, clays are phyllosilicate mineral solids that have a size below about 2 or 4 microns, and also have active surfaces that interfere with the bitumen separation process. Due to their activity and small size, when clays are present in higher concentrations their impact tends to dominate over other mineral solid particles, such as larger "fines" which are typically understood as being smaller than 44 microns as week as coarse sand. Clays found in oil sands are mostly composed of kaolinite and illite, although oil sands can also contain fractional amounts of chlorite, smectite, feldspar and montmorillonite.

[0018] Basing PSV control on solids content or fines content does not account for the dominance of clays at higher clay content levels. In addition, solids or fines content of a slurry can remain relatively constant while the clay content on a total solids basis can vary. Thus, basing PSV control on clay content for high-clay slurry streams can lead to enhanced performance, particularly for variable slurry compositions and high-clay slurries.

[0019] The PSV is a unit that is part of an overall oil sands process, which will be described briefly below. The overall oil sands processing facility typically includes various steps, including mining the ore; crushing the ore; breaking the ore down into sized particles (e.g., in a rotary breaker); forming an aqueous slurry with process water and the particulate sized ore; conditioning the slurry in a pipeline (also referred to as hydrotransporting); subjecting the conditioned slurry to primary extraction to produce a bitumen froth and tailings; and subjecting the bitumen froth to secondary extraction where a solvent (e.g., paraffinic or naphthenic) is added to the froth to facilitate separation of bitumen from mineral solids and water to produce diluted bitumen and froth treatment tailings. The diluted bitumen can then be processed in a number of ways to produce a final bitumen product. The PSV is part of the primary extraction stage of the overall process. Figure 2 provides an illustration of an overall oil sands processing facility with its main unit operations.

[0020] An important part in oil sands processing is the separation of oil sands slurry in the PSV, which can also be referred to as a primary separation cell. The PSV
is typically located at the end of the hydrotransport stage and is the first main separation stage to which the oil sands slurry is fed. In the PSV, bitumen is separated from mineral solids and water using flotation and gravity mechanisms. The bitumen-containing slurry that has been subjected to hydrotransporting is introduced into the PSV. Due to bitumen's hydrophobicity, once bitumen is liberated from coarse sand and other solid particles, bitumen droplets may attach to air bubbles that are injected into the PSV and float to the top of the PSV, forming a "bitumen froth". The bitumen froth is typically recovered as an overflow stream that is predominantly bitumen and includes some residual solids and water that are removed in downstream processing (secondary extraction). The coarse solid particles contained in the slurry are relatively heavy and tend to sink to the bottom of the PSV. The fraction of the slurry that remains in the middle of the PSV
is made up of material not heavy enough to readily sink and not light enough to readily float, and is generally referred to as middlings. The middlings fraction mainly includes fines and clay particles, water, and some bitumen. Thus, the oil sands slurry separates into three components: tailings that are withdrawn as an underflow stream, middlings that are withdrawn as an intermediate stream from the side of the PSV, and bitumen froth that is withdrawn as an overflow stream.

[0021] It has been found that PSV separation performance has a strong correlation with clay content of the slurry feed at high-clay levels. In particular, it was found that bitumen recovery can be maintained over a target threshold by ensuring that the clay content of the slurry feed is below a maximum threshold. This clay-based control can be achieved in a variety of ways. For example, dilution water introduced into the slurry feed upstream of the PSV can be controlled in order to add sufficient water into the slurry when the measured clay content exceeds a maximum threshold value, thus keeping the clay content of the feed within a target range.

[0022] There are various methods described herein for obtaining and using clay content indicators for the PSV slurry feed in automated control of the PSV to facilitate bitumen recovery and separation performance. As shown in Figures 1 to 5 and 7, it should be appreciated that there are a number of implementations of clay-based operation of the PSV, where a clay content indicator is obtained and one or more operating parameters are adjusted in response to the clay content indicator to maintain bitumen recovery levels in the PSV. Some possible implementations of the process will be discussed further below.
Clay content measurements and indicators

[0023] As mentioned above, clay content has been found to correlate with separation performance of oil sands slurry in PSVs. There are various methods and techniques to obtain measurements or parameters that are indicative of clay content.

[0024] In terms of measurement techniques, the clay content can be measured by using a K40 analyzer, a near-infrared (NIR) analyzer, a methylene blue index (MBI) analyzer or other analyzers that can provide an accurate indication or estimation of the amount of clay in the slurry. The clay content analyzer can be provided inline or at-line, for example.

[0025] The K40 analyzer measures emissions from a radioactive potassium isotope and is an appropriate proxy for clay content for oil sands slurry with a high-clay content.
Its units are typically counts per second. At low clay contents, the K40 analyzer measures isotope emissions not only from clays but also from coarser particles that also include the isotope, and thus is not correlated with clay content for low-clay slurries.
Thus, when implementing a K40 analyzer, its readings will not be indicative of clay content for slurries that have low levels of clay, but will rather be more indicative of solids content or fines content depending on the granulometry of the solids fraction.
When oil sands slurries have high-clay levels, the K40 analyzer provides an accurate indication of clay content of the slurry for PSV process control.

[0026] The NIR analyzer obtains spectral measurements of the slurry or other oil sands materials, and can be used to determine clay content based on predetermined correlations between clay concentration and NIR spectra. Thus, NIR-based calibration curves can be developed based on sample slurries having known clay levels (e.g., measured using other techniques that may be performed in a laboratory), and the curves can then be used to determine clay content based on NIR measurements of the oil sands slurry stream. NIR analyzers can be implemented at various locations in the overall process to determine clay content of different materials and streams.

[0027] The MBI analyzer can be used to estimate clay content based on a titration method that uses methylene blue. MBI techniques can be used at-line or in the laboratory, for example. For the case of MBI analyzers, it may take more time to obtain clay content information compared to K40 analyzers, which are rapid and can obtain real-time data for process control.

[0028] Depending on the particular analyzer that it used, the analyzer may be designed and calibrated to clay activity or clay concentration, which may be aided by laboratory MBI tests. Calibration to MBI or other clay concentration tests can facilitate higher accuracy in representing the clay proportion or content of the slurry.
The calibration can also be performed with samples from the same general formation or mining site from which ore is used to form the oil sands slurry stream. Since different ores can have various different properties and compositions, calibration is ideally conducted with representative oil sands ore samples.

[0029] Once the clay content measurement is obtained, it can be used directly for PSV
control or it can be used to determine a clay content indicator. The "clay content indicator" is a parameter that can be constructed from the clay measurement and optionally other data regarding the PSV or slurry stream. Depending on the control strategy and methodologies implemented for the PSV or the oil sands processing facility in general, various clay content indicators can be used for PSV control. For example, in one implementation, the clay content indicator can be a clay-to-dilution water ratio (CDWR) that is determined as the ratio between the clay content and the quantity of dilution water added to the oil sands slurry stream prior to the PSV. In this case, even at low-clay levels, a small amount of dilution water can be added to the slurry so that the CDWR remains finite. When the slurry has higher clay contents, the CDWR will increase until it reaches a maximum threshold at which point the flow rate of the dilution water will be increased to reduce the clay proportion in the slurry feed to the PSV and this, in turn, reduces the CDWR to a setpoint below the maximum threshold. Of course, in this implementation, the addition of dilution water to the slurry is one of the control strategies to ensure bitumen recovery in the PSV. It should nevertheless be noted that other operating parameters of the PSV can be adjusted based on the CDWR as the clay content indicator. The CDWR can have various units depending on the measurement approach (e.g., for the K40 analyzer, the clay content can be in "counts" per time and the dilution water can be a volumetric or mass flow rate).

[0030] Figure 7 illustrates a process that includes PSV control using CDWR as a control parameter. A clay content analyzer (e.g., K40 analyzer) obtains clay content data regarding the slurry stream, and a flow rate monitor obtains flow rate data of the dilution water flowing through the dilution line into the slurry stream. In this case, the dilution water can have a baseline flow rate even when the clay content of the slurry is below a control setpoint or even at very low levels. This baseline flow can be selected to be quite low, such as below 1% of the slurry flow rate, for example. The controller is configured to continuously determine a CDWR value based on the measured clay content and dilution water flow rate. The controller is also programmed with a CDWR setpoint, such that when the measured CDWR exceeds the setpoint the controller actuates the valve on the dilution line to increase the dilution water flow rate so that the CDWR will be lowered to the setpoint. If the clay content decreases, the CDWR will also decrease and the controller can then actuate the valve to decrease the dilution water flow rate to the appropriate level, which can be as low as the baseline flow rate, to achieve the CDWR
setpoint. In this manner, the CDWR is used as an indicator for process control of the clay content of the slurry feed into the PSV.

[0031] Of course, other CDWR-based control strategies can also be used and may be combined with other control variables for PSV control. For example, the setup of Figure 7 could be modified so that the clay content analyzer is downstream of the dilution line to enable feedback control.

[0032] In another implementation, as example of which is shown in Figure 1, the clay content indicator is a clay-to-water ratio (CWR) of the slurry itself, which is determined as the ratio between the clay content and the water content of the slurry.
Water content of the slurry can be determined, measured or estimated in various ways.
Alternatively, the CWR can be estimated based on the clay content alone using a predeveloped formula depending on how the clay content is measured. One example of such a formula is CWR = A(K40) ¨ B, where A and B are predetermined empirical constants and K40 is counts per second as measured by the K40 analyzer. When the slurry has higher clay contents, the CWR will increase until it reaches a maximum threshold at which point at least one operating parameter will be controlled in response. In one example case, dilution water is added to the slurry to reduce the CWR in the slurry feed to the PSV.
Dilution can be done so that the CWR is brought back to a setpoint below the maximum threshold. When dilution water is added, it can be introduced only in response to high CWR and turned off when the CWR is below the threshold; alternatively, a small flow of dilution water can be fed into the slurry even at lower CWR, if desired.

[0033] Of course, other CWR-based control strategies can also be used and may be combined with other control variables for PSV control. For example, the setup of Figure 1 could be modified so that the clay content analyzer is upstream of the dilution line or CWR adjustment means to enable feedforward control.

[0034] Other clay content indicators can also be developed and used for process control of the PSV unit. The clay content indicator can include other variables of the process, just as the CDWR includes dilution water and CWR includes water content of the slurry. In some implementations, the clay content indicator includes only terms related to clay and water content, and thus does not include terms related to bitumen content or other components of the slurry, which can provide adequate PSV
control with less complex monitoring setups and control programming.

[0035] The maximum thresholds and setpoints for the PSV control strategy can be developed based on target bitumen recovery by the PSV. "Bitumen recovery"
generally refers to the percentage of bitumen recovered in the bitumen froth compared to the total bitumen in the oil sands slurry stream fed into the PSV. Bitumen recovery targets can be between 88% and 95%, for example. To determine the maximum thresholds and setpoints for the PSV control strategy, empirical testing can be conducted where the clay content of the incoming slurry is varied, actual bitumen recovery levels are determined for the different clay-content slurries, and different operating parameters (e.g., dilution) are then varied to determine the clay levels at which the bitumen recovery dips below the target levels and the control strategies that maintain bitumen recovery in the target range. Other PSV variables can also be used to help determine the maximum thresholds and setpoints for the PSV control strategy, such as froth quality (e.g., solids and water content in froth to be kept to a minimum) and others.
PSV control and process implementations

[0036] Figures 1 to 5 and 7 illustrate different process arrangements and strategies for clay-based control of the PSV. These example processes will be described in further detail below.

[0037] Referring to Figure 1, a process for separating bitumen from an oil sands slurry can include feeding the slurry to a PSV 12 which is illustrated here as producing bitumen froth 14, middlings 15, and tailings 16. Measurement of the clay content may include the use of an analyzer 18, which can provide inferential clay content measurements, i.e., readings from which clay content can be inferred. Various analyzers can be used, such as a K40 analyzer, as discussed above. In some implementations, monitoring of the clay content may include automated analysis of the slurry in real time, as shown in Figure 1.

[0038] Clay content can also be measured for other streams in the overall oil sands processing facility. Depending on the stage of the process, different measurement techniques may be used to adapt to the type of material from which the clay content is being measured. For example, a K40 analyzer, may be used as the analyzer 18 to perform in-line measurement of the oil sands slurry feed 10 upstream of the PSV 12 and at the end of the hydrotransport line. NIR analyzers can also be deployed for obtaining clay-content data.

[0039] As shown in Figure 1, the analyzer 18 can be located downstream of a dilution line configured to add water into the slurry to reduce the concentration of the clay in the feed supplied into the PSV 12. Alternatively, as shown in Figures 3, 4 and 7, the analyzer 18 can be located upstream of a dilution line. It should be noted that analyzers can be located both upstream and downstream of a dilution line, and indeed at various locations throughout the process depending on the control strategy to be implemented.
In some implementations, multiple dilution lines can be provided and controlled to enable different dilution water rates added to the slurry stream upstream of the PSV.

[0040] Automation of these measurements and integration within an automated controller can facilitate maintaining the clay content or a clay indicator (e.g., CDWR, CWR) of the oil sands slurry below a maximum threshold selected to provide good separation efficiency and bitumen recovery within a target range, thereby reducing bitumen losses, mitigating negative effects of clay on downstream processes, particularly when processing high clay-content ore. The measured clay content of the slurry can thus be used to control PSV operations, particularly for high-clay slurries.

[0041] Turning back to Figure 1, a controller 20 can be operatively connected to the analyzer 18 to receive relevant information from it related to the measured clay content and possibly other data depending on the design and implementation of the analyzer 18.
If multiple analyzers are used, they can all be coupled to a single controller 20, if desired. In Figure 1, the controller 20 is configured to implement a control strategy for the PSV based at least in part on the clay content of the slurry. The controller 20 can be configured to calculate or determine the clay content indicator, if one is used for the control strategy. For example, the controller 20 can be programmed to determine the CDWR or CWR that may be used for process control, and can also include an algorithm that includes information regarding maximum thresholds and setpoints. The controller 20 is also configured so that when the clay content indicator exceeds the maximum threshold, the controller 20 will execute a control strategy to adjust at least one operating parameter of the PSV 12 in response to such high clay contents to help maintain high bitumen recovery levels. For example, as shown in Figure 1, the controller 20 can be coupled to a dilution line (referred to here as a CWR adjustment means 22) to control dilution water added to the slurry in order to keep the clay content of the slurry feed sufficiently low. Thus, in this implementation, in response to a high CWR, the controller 20 actuates the CWR adjustment means 22 to add water and thus reduce the CWR
to within a more optimal range.

[0042] When CWR is used as the clay content indicator, the target or setpoint CWR
value may be a function of the size and shape of the PSV 12 as well as the type and quality of the oil sands ore. For low-clay ores, the slurry will have a CWR
that is below the target setpoint, and thus normal operation can be conducted with no advanced clay-based control strategies. However, for higher-clay ores, the CWR can exceed the target CWR setpoint and, consequently, the process will be adjusted accordingly, for example by adding dilution water at a corresponding flow rate to quickly bring the CWR
of the slurry feed to the setpoint. Addition of dilution water will continue as long as high-clay slurries are being processed; if the slurry returns to low-clay levels, the dilution may be ceased or substantially reduced until needed again.

[0043] Referring to Figure 2, an overall oil sands processing facility 24 is illustrated and includes a number of analyzers that are located at different points in the process for obtaining clay content measurements. A K40 analyzer 18 is located upstream of the PSV 12, and can obtain K40 measurements for the slurry being fed to the PSV
12.
Upstream of the PSV 12 are other unit operations of the process, including mining 28 to obtain raw ore 30; slurry preparation 32 (which can include crushing, sizing, breaking, and mixing with water) to form an oil sands slurry 34; and hydrotransport 36 that includes pipelining the slurry in order to impart pipe shearing and produce a conditioned oil sands slurry stream 10 that is ready to be fed into the PSV 12. The bitumen froth 14 can then be supplied to downstream processing referred to as froth treatment 38 where a solvent (e.g., paraffinic solvent or naphthenic diluent) are added to the froth to aid in separating diluted bitumen from the water and mineral solids that form froth treatment tailings 40. The diluted bitumen can then be processed to produce a bitumen product 42.
As for the middlings 15, they can be further processed in one or more flotation vessels

44 to recover scavenger froth that can be recycled back into the PSV 12, and fine tailings that are disposed of. An example of the processing of the middlings 15 can be seen in Figure 3; there can be two flotation vessels in series for treating the middlings stream. Various tailings streams can be sent to tailings ponds for settling or for further treatment.
[0044] Referring to Figure 3, the PSV 12 can receive a slurry feed 10 into which dilution water 46 has been added in response clay content measurements enabled by the analyzer 18. This process arrangement illustrates that the controller 20 can receive data and measurements from multiple analyzers, indicated here as 18 and 18a.
In this case, the controller 20 is coupled to the dilution line 22 at a valve 48 to control the dilution water flow rate. The dilution water can be supplied from a process water vessel 50 that receives process water 52 from the oil sands processing facility 24, e.g., from water obtained from an upper layer of tailings ponds. However, it should be noted that the water used for dilution can be obtained from various sources, including fresh water, process waters, or a combination thereof. A secondary flotation vessel 54 can receive and process middlings 15 from the PSV 12. In the process illustrated in Figure 3, the analyzer 18 is located upstream of the dilution line addition point, which can facilitate feedforward process control for the PSV 12. The controller 20 can enable the PSV
control based on clay content, CWR or CDWR, for example, as explained above.

[0045] As noted further above, the clay content may be a single input parameter provided to the controller 20, but additional variables can also be measured and provided to enhance the control strategy. Thus, the controller 20 can be configured as a multi-parameter control system which receives multiple input variables and controls multiple aspects of the PSV 12 and optionally other parts of the overall process. The multiple variables may be different clay-based measurements taken from different streams or locations in the facility. For example, clay content measurements can be made on oil sands ore, oil sands slurry, tailings streams, bitumen enriched streams, middlings streams, and so on. Multiple clay measurements can facilitate redundancy and higher accuracy for the PSV control techniques described herein. In some situations, clay can be tracked through the overall facility and various units can be controlled to enhance separation of clay from bitumen and promote high bitumen recovery levels.

[0046] Depending on the location within the overall process, different measurement techniques may be used to adapt to the type of material which is being monitored for clay content. Referring to Figure 2, clay content may be measured upstream of the PSV
12 with an NIR analyzer at the mining stage to analyze ore, and/or with a K40 analyzer 18 at the end of the hydrotransport line 36, for example. Clay content may also be measured downstream of the PSV 12 with an NIR analyzer for the diluted bitumen froth and/or the tailings exiting the PSV 12. Clay content could also be measured at flotation banks where the middlings 15 can be processed. Two different analyzers can also be used to measure clay content of the same stream to obtain a more precise estimation. In some implementations, both upstream and downstream parameters are measured and can be used for process control of the PSV 12 and optionally other unit operations as well. Some optional parameters that can be measured include temperature, pressure, density profile in the PSV 12, flow rates of various streams, bitumen losses to the tailings 16, and composition characteristics of various streams. In addition, there may be several NIR probes deployed in the froth treatment facility for obtaining data for the diluted froth feed, diluted bitumen overflow product, secondary tailings, and tertiary tailings, for example.

[0047] Still referring to Figure 2, density and temperature measurements (e.g., with Tracercom" nucleonic liquid interface gauge) can be performed with a profiler inside the PSV 12. Measurements are iterated from the top of the vessel to a mid section of the vessel or to the bottom of the vessel. After plotting the shape of the density and temperature profiles inside the vessel, the shape of the profiles can indicate poor or good separation. For example, if the density profile is low at the top (bitumen froth zone) and gradually increases to above around 1.1 or more in middlings zone, separation performance is often considered satisfactory. If the density profile shape is flatter, separation performance may be poor or even inadequate such that adjustment is desirable. Additionally, if the temperature profile shape is not a mirror image of the density profile shape, it may be an indication that the clay content of the slurry feed should be lowered, e.g., by adding dilution water. The control strategy for the PSV 12 can include continuous monitoring of the density and temperature profiles within the PSV
12, determining a corresponding real-time separation performance level, and deciding whether to take action by upstream dilution for example. The profiling can be used in combination with clay measurements to provide enhanced control of the PSV 12.

[0048] For example, a profiler can be used to determine a certain volume or height of the middlings zone, which can indicate whether good separation is to be expected.
Large middlings volumes can be an indirect indication of low-grade, high-clay ore in the slurry. For example, an increase in the volume of middlings 15 can slow down the coarse particles that sink to the bottom of the PSV 12. Based on the profile monitoring, the PSV process control can be adapted accordingly.

[0049] Referring to Figure 3, in another example setup, clay content may be measured upstream of the PSV 12 and bitumen content of the tailings 16 may be measured downstream of the PSV 12 via another analyzer 18a. More particularly, the clay analyzer 18 may be provided upstream of the PSV 12 to measure the clay content of the oil sands slurry stream 10 in real-time, and a bitumen analyzer 18a may be provided downstream to measure bitumen loss to the tailings 16. The measurements may be sent to a multi-parameter controller 20 which can compare a theoretical or target bitumen recovery level (e.g., correlated to the CWR or CDWR target value) to a real-time bitumen recovery level (derived from the measured bitumen in the tailings 16). The controller 20 can be operatively connected to the valve 48 of the dilution line 22 or to other control assemblies. Based on monitoring of the clay content of the oil sands slurry feed and the bitumen losses to the tailings, the controller 20 can actuate the valve 48 for adjusting the amount of water added to the oil sands slurry feed 10, and thereby adjusting the clay content to within a target range.

[0050] Figure 7 illustrates a process where a clay content analyzer (e.g., K40 analyzer) 18 obtains clay content data regarding the slurry stream 10, and a flow rate monitor 56 obtains flow rate data of the dilution water 46 flowing through the dilution line 22 into the slurry stream 10. The dilution water has a baseline flow rate even when the clay content of the slurry 10 is below a control setpoint. The controller 20 receives information from the analyzer 18 and the flow rate monitor 56, and is configured to continuously determine a CDWR value based on the measured clay content and dilution water flow rate. The controller 20 is also programmed with a CDWR setpoint, such that when the measured CDWR exceeds the setpoint the controller 20 actuates the valve 48 on the dilution line 22 to increase the dilution water flow rate so that the CDWR
will be lowered to the setpoint. Thus, dilution of the slurry is controlled for introduction into the PSV 12, which produces the froth 14, middlings 15 and tailings 16 streams.

[0051] Of course, other CDWR-based control strategies can also be used and may be combined with other control variables for PSV control. For example, the setup of Figure 7 could be modified so that the clay content analyzer is downstream of the dilution line to enable feedback control.
Feedback and feedforward control implementations

[0052] In some implementations, the control method can include both feedback and feedforward control to adapt to changes in clay content in order to maintain performance of the PSV. For instance, in response to a change in clay content measured in the slurry feed to the PSV, feedforward control can be performed by adding dilution water downstream of the analyzer to dilute the slurry before the PSV, while feedback control can be performed by increasing the process water added to the sized ore to form the slurry to be hydrotransported. In this way, the slurry that is formed upstream can have a lower CWR compared to the slurry that was measured by the analyzer as having high clay content. These types of dual control strategies can be advantageous for a number of reasons.

[0053] Referring to Figure 4 showing an example implementation, the analyzer measures real-time clay content of the slurry 10 which is fed to the PSV 12.
This data is sent to the controller 20 which determines a corresponding CWR and compares the latter to a target CWR correlated to a target bitumen recovery level of the PSV 12.
Based on this comparison, the controller 20 is configured to selectively actuate at least one of the feedback control valves 60, 62 for feedback control of the amount of water added in upstream process stages to form the slurry. Based on the monitored CWR, the controller 20 can further actuate at least one of the valves 48, 64, 66, 68 for feedforward control of the amount of water added in downstream process stages. In one implementation, the feedforward control valve that is actuated is the dilution valve 48 and optionally other valves.

[0054] Figure 5 shows an example process in which multiple analyzers (shown as M) and adjustment means (shown as A) are provided for monitoring and adjusting process parameters. A central controller 20 can receive all of the monitoring information (e.g., M1 to M8 as illustrated) and can, in turn, control the adjustment means (Al to All) in response to the input data. For example, a clay analyzer shown as M1 can be used to monitor clay content of the slurry stream 10, and an adjustment means Al can be controlled to adjust CWR, for example, in response to high detected clays in the slurry as part of a feedforward control scheme. As mentioned above, other adjustment means A2, A3, A4 can be controlled in a feedback control scheme based on measurements from Ml. One or more additional adjustment means A5 to Al 1 located downstream can also be activated, if desired. In addition, there may be further analyzers (M2 to M8) for detecting one or more characteristics of streams or units, and the controller 20 can be operated to conduct additional adjustments of operating parameters upstream or downstream of the PSV 12, as illustrated.

[0055] Each adjustment means can be provided based on the potential and suitable adjustment that can be made to the given stream or unit. For example, some adjustment means, such as Ml, can include dilution to add water to the slurry stream 10.
Other adjustment means can include systems that adjust the flow rate of the stream to increase or decrease the flow being introduced into a downstream vessel. Still other adjustment means can include chemical addition so that more or less chemical aids can be added. Other adjustment means that enable heating to increase the temperature of a stream or unit can be used.

[0056] In one implementation, mining adjustment means A4 can be used to modify the mining process in order to, for example, adapt the mining grid or plan to target higher or lower clay ores. For instance, referring still to Figure 5, when the analyzed clay content (via M1) is such that the clay is above a target setpoint, control of the upstream mining and excavation 28 by the adjustment means A4 can be conducted to tailor the mining grid to shovel lower clay ores, and/or blend different excavated ores to lower the clay content of the overall ore material used to form the slurry 10. This feedback control does not of course immediately yield results in the PSV 12, but it can enable enhanced processing of the overall mined ore.

[0057] During slurry preparation 116, the adjustment means A2 may be actuated such that more water is added to produce the oil sands slurry 10. Adjustment means A3 may be actuated to provide water and/or a chemical to the slurry 10 during hydrotransport 36. Regarding downstream process steps, in response to an increase in clay content, water and/or chemicals may also be added to a feed just before flotation vessels 12 and/or 54 (with adjustment means Al and/or All respectively), or directly within the flotation cells (with adjustment means A10 and/or A8). In response to an increase in clay content, adjustment means may be actuated such that the middlings 15 are withdrawn out of the PSV 12 at one or more levels thereof or at different flow rates.
Regarding the tailings 16, adjustment means A5 and A6 may be actuated to change the tailings flow rate to modify separation performance in the vessels.
Additionally, further downstream process stages may be controlled according to the monitored clay content.

[0058] Still referring to Figure 5, it should be noted that feedback and feedforward control via certain adjustment means may also be performed based on in-line measurements from additional analyzers, e.g., M2 to M4. These analyzers can provide the controller 20 with data indicative of the real-time separation performance, such as bitumen losses to the tailings 16 (via M2 and M6), clay content of the middlings 15 (via M3) and of the diluted froth 14 (via M7), density and/or temperature profiles within the flotation cells 12 and 54 (via M4 and M8), or a combination thereof.

[0059] In addition, there can be a hot process water (HPVV) froth underwash that is introduced into the PSV 12 at a height just above the middlings draw line.
This froth underwash stream can also be measured and controlled. For instance, the measurement can be done by an analyzer, as explained above, and the control can include adjustment means that can control the flow rate of the underwash stream, for example.

[0060] In the case of low-clay ore, adjustment means may be actuated to reduce the amount of water added to produce the oil sands slurry 10, thereby increasing the capacity of the separation stage for ore and reducing water that reports to tailings streams and requires heating.

[0061] It should be understood that the adjustment means may include various systems and equipment, e.g., one or more valves, pumps, injectors, heaters and other devices to perform the suitable adjustments to the various different process streams and units in the oil sands processing facility.

[0062] It is also noted that the clay-based process control techniques described herein can be applied to PSVs that are part of an oil sands processing facility, as well as other flotation or separation units used to separate an oil sands stream that includes bitumen, water and clay. For instance, the process control techniques described herein can be applied to secondary flotation vessels used to process middlings, or other separation vessels that receive streams that can periodically or consistently have high clay contents.
EXPERIMENTATION

[0063] Experiments have been performed on twenty typical ore samples and five ore blends including bitumen, fines, clays and soluble ion contents, to provide a basis for process control model to improve separation efficiency. A modified batch extraction procedure was used for preparation of the slurry and flotation thereof, that mimics hydrotransport and flotation in the PSV in primary extraction. The slurries were mixed until complete ablation of bitumen lumps and separation of bitumen from sand grains. Air was used as a flotation aid and the overall ore to water ratio varied to determine the impact on bitumen flotation and recovery.

[0064] The clay-to-water ratio (CWR) was found to be the most important variable in controlling bitumen recovery as seen on Figure 6. While the bitumen content correlates to recovery, its contribution within the mineable concentration range (9 ¨ 15 wt%) does not appear not causative. In general, the CWR in the primary separation vessel has negative impacts on recovery.

[0065] An empirical relationship was derived between the bitumen recovery (R) and the clay content in the ore, slurry and froth underwash water volume (as clay-to-water ratio or CWR) and the connate and process water chemistry (in TDS ppm).
Although bitumen oxidation has an impact on recovery, it is assumed that the incidence is minimized by ore blending and should not contribute significantly to the plant bitumen recovery.

[0066] The developed relationship is given as:
R = Rmax Rmiinx¨hRamlfa)x Equation 1 +.--rex Rmax = maximum recovery; Rim = minimum recovery, xhalf and rate are fitting coefficients to the sigmoid function and = ((2.65)a * TDS5) CWR Equation 2 a and b are fitting coefficients and X is proportional to the viscosity of the middlings.

[0067] Example coefficients are given below:
Rmax 96.1 Rmm 19.7 xhaff 0.64 rate 2.77 a -1.99 0.71

[0068] It should be noted that the recovery equation may be optimal for process water chemistry up to about 8000 ppm TDS and Ca and Mg contents below 1.5 mM (about ppm Ca and 15 ppm Mg), for example. Higher CWRs have been quantitatively shown to impact bitumen recovery. Water chemistry including TDS can also har an impact and thus a given CWR control strategy can be provided for a certain operating envelope of water chemistry and can be adapted or recalibrated if the water chemistry changes.

Claims (54)

1. A method for controlling a primary separation vessel (PSV) used to separate an oil sands slurry feed into a bitumen froth overflow stream, a middlings stream, and a tailings underflow stream, the method comprising:
measuring clay content of an oil sands slurry stream;
introducing dilution water into the oil sands slurry stream to form the oil sands slurry feed that is introduced into the PSV, the dilution water having a dilution flow rate; and controlling the dilution flow rate in response to the measured clay content of the oil sands slurry stream, comprising:
when a clay content indicator based on the measured clay content is below a maximum threshold, maintaining the dilution flow rate at a baseline flow rate; and when the measured clay content is above the maximum threshold, automatically adjusting the dilution flow rate to provide the oil sands slurry feed with a decreased clay content below the maximum threshold.

2. The method of claim 1, wherein measuring the clay content comprises obtaining a K40 measurement of the oil sands slurry stream.

3. The method of claim 2, wherein controlling the dilution water further comprises determining the clay content indicator based on the K40 measurement and the dilution flow rate.

4. The method of claim 3, wherein the clay content indicator is a clay-to-dilution water ratio (CDWR) of the K40 measurement and the dilution flow rate.

5. The method of claim 4, wherein the maximum threshold of the CDWR is predetermined based on empirical testing to maintain a minimum bitumen recovery from oil sands slurry stream by the PSV.

6. The method of claim 4, wherein the maximum threshold of the CDWR is between 0.20 and 0.25.

7. The method of claim 4, wherein the maximum threshold of the CDWR is between 0.21 and 0.24.

8. The method of claim 2, wherein the clay content indicator comprises a clay-to-water ratio (CWR) of the measured clay content and a water content of the oil sands slurry stream.

9. The method of claim 8, wherein the water content of the oil sands slurry stream used in the CWR is estimated from the K40 measurement.

10. The method of claim 9, wherein the CWR is determined based on formula CWR
= A(K40) ¨ B, wherein A and B are predetermined empirical terms.

11. The method of claim 9, wherein A is between 0.2 and 0.3 and B is between 0.5 and 0.7.

12. The method of any one of claims 8 to 11, wherein the maximum threshold of the CWR is between 0.1 and 0.15.

13. The method of claim 8, further comprising determining the water content of the oil sands slurry stream based on upstream water addition to form the oil sands slurry stream, density measurements of the oil sands slurry stream, online measurements of the oil sands slurry stream, or a combination thereof.

14. The method of any one of claims 1 to 13, wherein the maximum threshold is predetermined based on empirical assessment for a target minimum bitumen recovery level from the oils sands slurry stream.

15. The method of claim 14, wherein the target minimum bitumen recovery level is between 85% and 98%.

16. The method of any one of claims 1 to 15, wherein the target minimum bitumen recovery level is between 90% and 96%.

17. The method of any one of claims 1 to 16, wherein the baseline flow rate of the dilution water is at most 5% of a flow rate of the oil sands slurry stream on a volume basis.

18. The method of claim 17, wherein the baseline flow rate of the dilution water is at most 1% of a flow rate of the oil sands slurry stream on a volume basis.

19. The method of any one of claims 1 to 18, wherein measuring clay content of the oil sands slurry stream is conducted in-line.

20. A method for controlling a primary separation vessel (PSV) used to separate an oil sands slurry feed into a bitumen froth overflow stream, a middlings stream, and a tailings underflow stream, the method comprising:
measuring clay content of an oil sands slurry stream;
controlling dilution water added to the oil sands slurry stream in response to the measured clay content thereof exceeding a predetermined maximum threshold, to provide the oil sands slurry feed with a clay content below the maximum threshold.

21. A method for controlling a primary separation vessel (PSV) used to separate an oil sands slurry feed into a bitumen froth overflow stream, a middlings stream, and a tailings underflow stream, the method comprising:
determining a clay-to-water ratio (CWR) of the oil sands slurry feed; and automatically maintaining the CWR of the oil sands slurry feed below a maximum threshold before introduction into the PSV.

22. A method for controlling a primary separation vessel (PSV) used to separate an oil sands slurry feed into a bitumen froth overflow stream, a middlings stream, and a tailings underflow stream, the method comprising:
measuring clay content of the oil sands slurry feed; and automatically adjusting at least one operating parameter of the PSV when the measured clay content exceeds a maximum threshold.

23. The method of claim 22, wherein adjusting at least one operating parameter of the PSV comprises adding dilution water to the oil sands slurry stream.

24. The method of claim 23, wherein adding the dilution water comprises controlling a dilution flow rate in response to the measured clay content of the oil sands slurry stream.

25. The method of any one of claims 22 to 25, wherein measuring the clay content comprises obtaining a K40 measurement of the oil sands slurry stream.

26. The method of claim 25, wherein the clay content indicator is a clay-to-dilution water ratio (CDWR) of the K40 measurement and the dilution flow rate.

27. The method of claim 25, wherein the clay content indicator comprises a clay-to-water ratio (CWR) of the measured clay content and a water content of the oil sands slurry stream.

28. The method of any one of claims 22 to 27, wherein the maximum threshold is predetermined based on empirical assessment for a target minimum bitumen recovery level from the oils sands slurry stream.

29. The method of any one of claims 22 to 28, wherein measuring clay content of the oil sands slurry stream is conducted in-line.

30. The method of any one of claims 22 to 29, wherein adjusting at least one operating parameter of the PSV comprises adjusting an amount of water added to oil sands ore to produce the oil sands slurry stream.

31. The method of any one of claims 22 to 30, wherein adjusting at least one operating parameter of the PSV comprises adjusting a flow rate of at least one of the bitumen froth overflow stream, the middlings stream, and the tailings underflow stream.

32. The method of any one of claims 22 to 31, wherein measuring clay content of the oil sands slurry stream comprises obtaining near-infrared (NIR) spectral measurements of the oil sands slurry stream, and determining the clay content from predetermined calibration curves based on NIR measurements.

33. The method of any one of claims 22 to 31, wherein measuring clay content of the oil sands slurry stream comprises using methylene-blue-index (MBI).

34. The method of any one of claims 22 to 33, further comprising:
determining a real-time bitumen recovery from the PSV;
determining a difference between the real-time bitumen recovery and a target bitumen recovery; and automatically adjusting the at least one operating parameter of the PSV
based in part on the difference between the real-time bitumen recovery and the target bitumen recovery.

35. The method of any one of claims 22 to 34, wherein the oil sands slurry stream has variable clay contents, and automatically adjusting the PSV is performed periodically when the clay content increases above a maximum threshold.

36. A system for recovering bitumen from an oil sands slurry, comprising:
a feedline transporting the oil sands slurry;
a clay analyzer coupled to the feedline and configured to measure clay content of the oil sands slurry flowing therethrough;
a dilution line in fluid communication with the feedline and configured to add dilution water into the oil sands slurry to form an oil sands slurry feed, and comprising a valve for adjusting a dilution flow rate;
a primary separation vessel (PSV) comprising:
an inlet coupled to the feedline to receive the oil sands slurry feed;
a separation chamber for enabling separation of the oil sands slurry feed into an upper bitumen rich zone; a middle zone comprising clay solids, water and residual bitumen; and a lower solids rich aqueous zone;
an overflow outlet for withdrawing a bitumen froth from the upper bitumen rich zone;

an intermediate outlet for withdrawing a middlings stream from the middle zone; and an underflow outlet for withdrawing a tailings stream from the lower solids rich aqueous zone;
a dilution controller coupled to the valve and configured to control the dilution flow rate in response to the measured clay content of the oil sands slurry stream such that:
when a clay content indicator based on the measured clay content is below a maximum threshold, the dilution controller maintains the valve so that the dilution flow rate is at a baseline flow rate; and when the measured clay content is above the maximum threshold, the dilution controller automatically adjusts the valve so that the dilution flow rate increases to provide the oil sands slurry feed with a decreased clay content below the maximum threshold.

37. The system of claim 36, wherein the clay analyzer comprises a K40 measurement device.

38. The system of claim 37, wherein the clay content indicator is a clay-to-dilution water ratio (CDWR) of a K40 measurement and the dilution flow rate.

39. The system of claim 38, wherein the maximum threshold of the CDWR is predetermined based on empirical testing to maintain a minimum bitumen recovery from oil sands slurry stream by the PSV.

40. The system of claim 38, wherein the maximum threshold of the CDWR is between 0.20 and 0.25.

41. The system of claim 38, wherein the maximum threshold of the CDWR is between 0.21 and 0.24.

42. The system of claim 36, wherein the clay content indicator comprises a clay-to-water ratio (CWR) of the measured clay content and a water content of the oil sands slurry stream.

43. The system of claim 42, wherein the clay analyzer comprises a K40 measurement device and wherein the water content of the oil sands slurry stream used in the CWR is estimated from a K40 measurement.

44. The system of claim 43, wherein the CWR is determined based on formula CWR

= A(K40) ¨ B, wherein A and B are predetermined empirical terms.

45. The system of claim 44, wherein A is between 0.2 and 0.3 and B is between 0.5 and 0.7.

46. The system of any one of claims 42 to 45, wherein the maximum threshold of the CWR is between 0.1 and 0.15.

47. The system of any one of claims 42 to 46, further comprising a water content determination assembly for determining the water content of the oil sands slurry stream based on upstream water addition to form the oil sands slurry stream, density measurements of the oil sands slurry stream, online measurements of the oil sands slurry stream, or a combination thereof.

48. The system of any one of claims 36 to 47, wherein the maximum threshold is predetermined based on empirical assessment for a target minimum bitumen recovery level from the oils sands slurry stream.

49. The system of claim 48, wherein the target minimum bitumen recovery level is between 85% and 98%.

50. The system of claim 48, wherein the target minimum bitumen recovery level is between 90% and 96%.

51. The system of any one of claims 36 to 50, wherein the baseline flow rate of the dilution water is at most 5% of a flow rate of the oil sands slurry stream on a volume basis.

52. The system of claim 51, wherein the baseline flow rate of the dilution water is at most 1% of a flow rate of the oil sands slurry stream on a volume basis.

53. The system of any one of claims 36 to 52, further comprising an in-line measurement device configured to measure clay content of the oil sands slurry stream.

54. A process for producing a bitumen product from oil sands, comprising:
mining oil sands ore;
crushing the oil sands ore to form crushed ore;
subjecting the crushed ore to sizing and addition of process water to form a slurry;
conditioning the slurry in a hydrotransport line to form an oil sands slurry stream;
introducing the oil sands slurry stream into a primary separation vessel (PSV);
automatically controlling the PSV using the method as defined in any one of claims 1 to 35;
subjecting the bitumen froth to solvent based froth treatment to form solvent diluted bitumen and solvent extraction tailings; and recovering solvent from the solvent diluted bitumen to produce the bitumen product.