CA1081642A - Recovery of hydrocarbons from dilution centrifuging tailings - Google Patents
Recovery of hydrocarbons from dilution centrifuging tailingsInfo
- Publication number
- CA1081642A CA1081642A CA267,579A CA267579A CA1081642A CA 1081642 A CA1081642 A CA 1081642A CA 267579 A CA267579 A CA 267579A CA 1081642 A CA1081642 A CA 1081642A
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- cell
- tailings
- flotation
- froth
- recovery
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Abstract
"RECOVERY OF HYDROCARBONS FROM DILUTION CENTRIFUGING TAILINGS" The invention has to do with treatment of dilution centrifuging tailings which are produced in connection with a hot water extraction operation for recovery of bitumen from oil sands. The tailings are subjected to induced gas flotation for a predetermined period of time to recover contained hydrocarbons as froth.
Description
10816qZ
BACKGROUND OF TH~ INVENTION
. .
This invention relates to a process for recover-ing hydrocarbons from tailings produced by a dilution centri-I fuging circuit within an oil sand operation employing the known hot water extraction process. It also encompasses the hydrocarbon froth product obtained by the practise of the pro-cess.
: The hot water extraction process, used commer-cially to recover bitumen from the Alberta oil sands, involves the following series of steps:
(1) slurrying, heating and conditioning the oil sand in a rotating drum in which it is mixed .
with steam, hot water and caustic;~
BACKGROUND OF TH~ INVENTION
. .
This invention relates to a process for recover-ing hydrocarbons from tailings produced by a dilution centri-I fuging circuit within an oil sand operation employing the known hot water extraction process. It also encompasses the hydrocarbon froth product obtained by the practise of the pro-cess.
: The hot water extraction process, used commer-cially to recover bitumen from the Alberta oil sands, involves the following series of steps:
(1) slurrying, heating and conditioning the oil sand in a rotating drum in which it is mixed .
with steam, hot water and caustic;~
(2) diluting the slurry with more hot water and introducing it into a primary separation vessel where it is retained to permit buoyant bitumen particles to rise to the surface and ~ form primary froth;
: (3) withdrawing a stream of middlings from the mid-point of the separation vessel and subjecting it to induced air flotation in a secondary recovery flotation cell to cause contained bitumen to form secondary froth; and (4) combining the primary and secondary froths to form a combined froth product.
' The dilution centrifuging process used to remove water and solids from the froth product of the hot water ex-traction process involves the following steps:
~ (1) diluting the combined froth product with t 30 naphtha to alter the viscosity and specific !
gravity of the contained bitumen; and 1~8i6;42 (2) introducing the diluted froth into a two-stage centrifugal separation circuit where the coarse solids are separated from the stream in a scroll-type centrifuge and the water and fine solids are separated in a disc-type centrifuge.
There is a significant loss of hydrocarbons in the dilution centrifuging (D.C.) tailings produced by the scroll and disc centrifuges. More particularly, in the plant presently being constructed by the assignee of this invention, there will be approximately 1.6 million pounds/hour of D.C. tailings pro-duced containing approximately 3.5% by weight bitumen, 2.1%
hydrocarbon diluent, 24.0~ solids and 70.4~ water. The losses of bitumen and diluent per day will be approximately 3,900 barrels and 3,200 barrels, respectively. These figures are only given by way of example, as it is expected that they will vary significantly with plant operating conditions and through-put.
The tailings composition shown above corresponds to the predicted values for a commercial plant. The tailings actually used in developing this invention were derived from pilot plant operations and contained a significantly greater proportion of water, as indicated in Example I. This extra water is a direct result of the mechanical configuration of the pilot plant centrifuges. However, the recovery of hydrocarbon from the pilot plant tailings is more difficult than it will be from the actual tailings, because the hydrocarbon content of the pilot plant tailings is reduced by the extra water.
' A problem which has heretofore existed was how to economically recover the hydrocarbons contained in the D.C.
tailings. If such a process could be developed, it would also ll ~1081~;4Z
be desirable that the diluent and bitumen be recovered in a single step. In this regard, it needs to be kept in mind that the D.C. tailings is a unique and difficult material to deal with. It contains a relatively small amount of bitumen and diluent distributed throughout a large quantity of water and solids. The bitumen in the tailings is originally re- jcovered as part of the froth produced by the hot water ex-traction process. Its rejection to the D.C. tailings together with the proportionate amount of diluent suggests that these hydrocarbons are physically associated with the froth solids.
Hence, despite the fact that the specific gravity of the diluted bitumen i5 less than 1.0, it still reports to the tailings. This is borne out by simple settling tests on D.C.
tailings, in which it is found that only minor quantities f tthe hydrocarbons present float and the bulk of them are found ; in the solids which settle out.
SVMMARY OF THE INVENTION
It has now been found that induced gas flotation can successfully be applied to D.C. tailings to recover the major portion of the bitumen and diluent. While minimum amounts of aeration and agitation are required to achieve hydrocarbon flotation, it has been determined that recovery varies signifi-cantly only with retention time up to a definite limit, at which point the process becomes relatively insensitive to changes in the operating conditions. It has also been determined that ' the relationship between retention time and recovery holds true for feedstocks of different compositions. Thus a preferred process employing multiple flotation cells has been outlined.
In this process, the retention time for each cell falls within 1 30 the predicted range wherein recovery from that cell is signifi-cantly sensitive to retention time. The process has success-.
` i 108~64Z
fully been practised to recover most of the bitumen and diluent contained in the D.C. tailings. The unique froth product holds the hydrocarbons in a contaminated but con-centrated form which can ~e either fed directly to the primary upgrading process or subjected to additional treat-ment to remove solids and water.
When the flotation cell is open to the atmosphere, it is found that some of the diluent is lost while the great-est part of the balance reports in the froth. In a preferred form of the invention, flotation is carried out in one or more sealed flotation cells using an inert gas, such as nitrogen, as the flotation agent. The excess gas collected from these cells is recycled to the flotation cells and ultimately be- j comes saturated with diluent vapors. When this state is reached, the recycled flotation gas no longer strips diluent from the tailings and the diluent then reports to the froth j in the same proportion as the bitumen. Tests have shown that the flotation efficiency, using nitrogen as the flotation gas, is unaffected by diluent vapor.
An alternative to the procedure of recycling saturated nitrogen to the flotation cell , involves employing a condensor to remove diluent vapor from the vent gas be-fore it is recycled. In this manner, some diluent can be recovered as liquid, and some is recovered in the froth. Both methods are effective to reduce the losses incurred by running the flotation cells open to the atmosphere.
In another preferred feature of the invention, it has been found desirable to maintain the aeration rate in the flotation vessel below 0.2 SCFM of gas per cubic foot of vessel capacity, while maintaining a minimum power input of 0.04 horsepower per cubic foot of vessel capacity. (It is to 1 .
be under~.tood that the term "aeration" as used herein i5 to be interpreted broadly to include introduction of an inert gas as the flotation agent.) The froth product obtained from this flotation process practised on D.C. tailings i`s unique i.n composition. It comprises 8 to 28% by weight hydrocarbons (that is bitumen plus di`luent), 70 to 37% water and 22 to 43%
soli.ds. I:n comparison to the original D.C. tailings, the hydrocarbons are present in greater concentration in this product and some solids and most of the water have been rejected; in comparison to combined primary and secondary froth, the present product contai'ns perhaps twice as much water and three times as many soli:ds. I.n any event, the product is a feedstock wh;ch can feasi.bly be treated to recover contained hydrocarbons as a pure product.
The invention is characteri:zed by the following advantages:
(1) A large proport;on of the hydrocarbons in the D.C. tailings can no~ econom;cally be recovered in a more concentrated form and water and solids can s;'multaneously be rejected;
and (.2~ The froth product ;.s proportionately small in volume when compared w;.th the or;g;nal D. C. tail;ngs and ~s amenable to further treatment at reasonable cost to recover the b;:tumen ;:n pure form.
Braadly stated, the ;:nvent;:on is a method for treating tailings obta;.ned directly from the di'lution centr;:fuging circu;`t of a hot water extractian complex for the recovery of b;tumen from oil sands, said ta;l;ngs conta;ning bi.tumen, hydrocarbon d;luent, solids and water, compr;s;ng: ;ntroduci.ng only the ta;:lings into a flotation cell and re-taining it therein for a suffic;ent period of time, while subjecting it to ag;tat;on and flotat;on us;ng gas ;ntroduced ;nto the base of the body of tail;.ngs, to recover a s;gnificant port;on of the contained bitumen and diluent as froth from the cell and to reject a portion of the solids and ~ater as under flow; and removing the froth from further treatment.
~ - 5 -108~;~4Z
DESCRIPTION OF THE DRAWING
In the dra~ing:
F;gure 1 is a block diagram setting forth the steps of ; the process;
., .
.. , ;
,, , .
- 5a -~..
Figure 2 is a schematic diagram of the circuit used to carry out the experiments involved in developing the invention; and Figure 3 is a plot of hydrocarbon recovery versus retention time for a single cell system.
DESCRIPTION OF THE PREFERRED EMBODIMENT
STARTING MATERIAL
The pilot plant D. C. tailings, which formed the feedstock for the development work involved in this invention, comprised a mixture of scroll centrifuge tailings and disc centrifuge tailings provided in a ratio of about 1 to 12.
These two streams were blended and usually heated in a mix tank to form a mixture having a temperature of about 170F.
FLOTATION
This mixture was introduced into a conventional induced gas flotation cell or into the first of a bank of such cells. The laboratory pilot plant used to develop the in-vention is illustrated in Figure 2. It comprised an agitated heating tank 1 to which cold disc and scroll tailings were fed manually and mixed and heated to about 170F. The product was pumped through a line 2 to a series of 3 Denver* induced air flotation cells from which the froth and tailings products were obtained. (*trade mark).
; As previously mentioned, the most significant p~rameter with respect to the operation of the flotation cell was its retention time. As shown in Figure 3, the slope of the curve obtained by plotting hydrocarbon recovery against retention time was consistently steep until it changed suddenly at point "A", after which increased retention time yielded little increase in recovery. This finding requires that one should choose a cell having sufficient volume to provide a !
10~1164Z
retention time corresponding with or close to the retention time at which the slope of the curve changes suddenly, for the particular D. C. tailings feedstock being processed. Now this choice will, of course, be also influenced to some extent by the economics of cell size and the limited range of sizes which are commercially available.
It has also been found that the recovery-retention time curve for a single cell, such as is shown in Figure 3, provides a reliable indication of the performance of additional cells placed in series downstream from the first cell. In other words, a reliable scale up is achieved by using the data from a single cell for a plurality of cells operating downstream from it and receiving its underflow.
- There is a minimum agitation level required in the cell, below which "sanding out" can occur. More particularly, it is preferred to operate the vessel above a minimum power input of about 0.04 H.P./ft.3 of cell volume.
; It has also been found that there is an air injection rate above which there is little improvement in recovery. More particularly, it is preferred to operate the flotation cells at an aeration rate of less than 0.2 SCFM/cu.
ft. of cell volume, as this is sufficient to recover the hydrocarbon.
It is also preferred to use multiple cells in series to improve the ultimate recovery. These cells can all be operated at the same condition.
If desired, nitrogen may be used with sealed cells to avoid losing diluent to the atmosphere and to eliminate the safety hazard associated with air-naphtha vapor mixtures.
The invention is illustrated by the following examples.
, 7 !
EXAMPLE I
This example involves the operation of a single cell open to the atmosphere. About 250 pounds of scroll tail-ings and 350 Imperial gallons of disc tailings were placed in a tank and heated to 170F with agitation. The time re-quired to accomplish this heating was approximately one hour.
The analyses of the two tailings was as follows:
TABLE I (Run L13) Typical Typical Measured % by weight Scroll ~ailings Disc Tailings D.C. Tailings hydrocarbons 6.46 1.50 1.70 solids75.00 4.00 6.85 water18.50 94.50 91.45 This mixture was fed at 23.5 lbs./min. into a 0.8 cubic foot capacity flotation cell equipped with a Denver Sub-A type aeration impellor. Air was fed into the body of tailings through the impellor mechanism. The cell operating conditions were as follows:
retention time - 2.26 minutes j 20 impellor speed - 750 r.p.m.
air rate - 0.175 SCFM/cu. ft. of cell volume power input - 0.09 HP/cu. ft. of cell volume Froth and tailings products were obtained at respective rates of 1.59 and 21.91 lbs./min. and had the fol-lowing compositions:
TABLE II
% by weight Froth Tailings ; hydrocarbons 15.61 0.73 Solids 30,44 5.57 ; 30 Water 53.95 93.70 ,, ~ .
EXAMPLE II
', This example illustrates that a reliable scale ' ``
10~1~42 up is obtained by using recovery data developed by a single cell and applying it to a bank of cells operating under similar conditions.
The underflow or tailings from Example I was subjected to two additional flotation stages. With the excep-tion of retention time, the cell design and operating conditions were identical to those of Example I. The retention time varied slightly from cell to cell by virtue of the froth produced which tended to reduce the volume of material fed to the next cell. Table III summarizes the experimental results:
TABLE III- (Run L13) Cell 1 Cell 2 Cell 3 Retention Time per Cell - minute 2.26 2.42 2.47 Froth Produced lb./minute 1.59 0.39 0.27 Froth Composition -by weight hydrocarbons 15.61 18.09 17.64 solids 30.44 36.54 32.28 water 53.95 45.37 49.98 The total froth and final tCell 3) tailings were obtained at respective rates of 2.25 and 21.25 lb./minute and had the following composition:
TABLE IV- ~Run L13) by wei~t Total Froth Final Tailings hydrocarbons 16.28 0.19 solids 31.73 4.66 ' water 51.99 95.15 ! 3o Cell 1 recovered 60.89% of the hydrocarbon (bitumen plus naphtha) fed to the bank of cells. This number was used to calculate the hydrocarbon recovered in cells 2 and 3.
Table V shows a comparison between calculated and measured _ g _ , , 108~ 42 performance. The total hydrocarbon recovery for the cell bank was adequately predicted from the single cell value.
TABLE V- (Run L13) , Total Cell 2Ce'll' 3 (Cell l + Cell 2 + Cell 3) % of Cell 1 Feed Hydrocarbon Recovered Measured 17.5611.62 90.08 Calculated 23.819.32 94.02 EXA _ LE III
This example illustrates that hydrocarbon re-covery is insensitive to increases in cell air input in the range 0.175 to 0.512 SCFM/cu. ft. of cell volume. Therefore the preferred air input is less than 0.175 SCFM/cu. ft. of cell volume. Runs L25, L26 and L27 were carried out at three dif-ferent air rates while other operating conditions remained essentially constant. Runs L43, L44 and L45 were accomplished in a similar manner. The major difference between these two ; 20 sets of runs was in cell retention times which were nominally 0.9 minutes and 1.25 minutes respectively.
TABLE VI
Av. Input Cell 1 Run SCFM/cu. ft. cell Recovery L25 0.175 , 23.41 L26 0.325 23.86 ' L27 0.512 23.52 I L43 0.175 40.36 L44 0.325 46.58 L45 0.512 39.97 EXAMPLE IV
This example illustrates the single cell relationship between hydrocarbon recovery and retention time.
Such a correlation can be used in sizing banks of multiple cells.
1019164i~ 1 An important feature is that recovery initially increases steadily with retention time but eventually the slope of the curve changes abruptly and becomes flat, so that further increases in residence time yield relatively little improvement in recovery.
A num~er of experiments were undertaken in which tailings were prepared and passed through the flotation cell as described in Example I. Feed rates to the cell were varied such that cell retention times ranged from about 0.9 minutes to 5.2 minutes. Impellor speed and power input were maintained constant at 750 rpm and 0.09 H.P./cu. ft. of cell volume. Air rates ranged from 0.175 to 0.512 SCFM~cu. ft. of cell, but as shown in Example III the recovery is independent of air rate.
Figure 3 shows the recovery-retention time relationship obtained fr~m this series of runs.
, , . I
: (3) withdrawing a stream of middlings from the mid-point of the separation vessel and subjecting it to induced air flotation in a secondary recovery flotation cell to cause contained bitumen to form secondary froth; and (4) combining the primary and secondary froths to form a combined froth product.
' The dilution centrifuging process used to remove water and solids from the froth product of the hot water ex-traction process involves the following steps:
~ (1) diluting the combined froth product with t 30 naphtha to alter the viscosity and specific !
gravity of the contained bitumen; and 1~8i6;42 (2) introducing the diluted froth into a two-stage centrifugal separation circuit where the coarse solids are separated from the stream in a scroll-type centrifuge and the water and fine solids are separated in a disc-type centrifuge.
There is a significant loss of hydrocarbons in the dilution centrifuging (D.C.) tailings produced by the scroll and disc centrifuges. More particularly, in the plant presently being constructed by the assignee of this invention, there will be approximately 1.6 million pounds/hour of D.C. tailings pro-duced containing approximately 3.5% by weight bitumen, 2.1%
hydrocarbon diluent, 24.0~ solids and 70.4~ water. The losses of bitumen and diluent per day will be approximately 3,900 barrels and 3,200 barrels, respectively. These figures are only given by way of example, as it is expected that they will vary significantly with plant operating conditions and through-put.
The tailings composition shown above corresponds to the predicted values for a commercial plant. The tailings actually used in developing this invention were derived from pilot plant operations and contained a significantly greater proportion of water, as indicated in Example I. This extra water is a direct result of the mechanical configuration of the pilot plant centrifuges. However, the recovery of hydrocarbon from the pilot plant tailings is more difficult than it will be from the actual tailings, because the hydrocarbon content of the pilot plant tailings is reduced by the extra water.
' A problem which has heretofore existed was how to economically recover the hydrocarbons contained in the D.C.
tailings. If such a process could be developed, it would also ll ~1081~;4Z
be desirable that the diluent and bitumen be recovered in a single step. In this regard, it needs to be kept in mind that the D.C. tailings is a unique and difficult material to deal with. It contains a relatively small amount of bitumen and diluent distributed throughout a large quantity of water and solids. The bitumen in the tailings is originally re- jcovered as part of the froth produced by the hot water ex-traction process. Its rejection to the D.C. tailings together with the proportionate amount of diluent suggests that these hydrocarbons are physically associated with the froth solids.
Hence, despite the fact that the specific gravity of the diluted bitumen i5 less than 1.0, it still reports to the tailings. This is borne out by simple settling tests on D.C.
tailings, in which it is found that only minor quantities f tthe hydrocarbons present float and the bulk of them are found ; in the solids which settle out.
SVMMARY OF THE INVENTION
It has now been found that induced gas flotation can successfully be applied to D.C. tailings to recover the major portion of the bitumen and diluent. While minimum amounts of aeration and agitation are required to achieve hydrocarbon flotation, it has been determined that recovery varies signifi-cantly only with retention time up to a definite limit, at which point the process becomes relatively insensitive to changes in the operating conditions. It has also been determined that ' the relationship between retention time and recovery holds true for feedstocks of different compositions. Thus a preferred process employing multiple flotation cells has been outlined.
In this process, the retention time for each cell falls within 1 30 the predicted range wherein recovery from that cell is signifi-cantly sensitive to retention time. The process has success-.
` i 108~64Z
fully been practised to recover most of the bitumen and diluent contained in the D.C. tailings. The unique froth product holds the hydrocarbons in a contaminated but con-centrated form which can ~e either fed directly to the primary upgrading process or subjected to additional treat-ment to remove solids and water.
When the flotation cell is open to the atmosphere, it is found that some of the diluent is lost while the great-est part of the balance reports in the froth. In a preferred form of the invention, flotation is carried out in one or more sealed flotation cells using an inert gas, such as nitrogen, as the flotation agent. The excess gas collected from these cells is recycled to the flotation cells and ultimately be- j comes saturated with diluent vapors. When this state is reached, the recycled flotation gas no longer strips diluent from the tailings and the diluent then reports to the froth j in the same proportion as the bitumen. Tests have shown that the flotation efficiency, using nitrogen as the flotation gas, is unaffected by diluent vapor.
An alternative to the procedure of recycling saturated nitrogen to the flotation cell , involves employing a condensor to remove diluent vapor from the vent gas be-fore it is recycled. In this manner, some diluent can be recovered as liquid, and some is recovered in the froth. Both methods are effective to reduce the losses incurred by running the flotation cells open to the atmosphere.
In another preferred feature of the invention, it has been found desirable to maintain the aeration rate in the flotation vessel below 0.2 SCFM of gas per cubic foot of vessel capacity, while maintaining a minimum power input of 0.04 horsepower per cubic foot of vessel capacity. (It is to 1 .
be under~.tood that the term "aeration" as used herein i5 to be interpreted broadly to include introduction of an inert gas as the flotation agent.) The froth product obtained from this flotation process practised on D.C. tailings i`s unique i.n composition. It comprises 8 to 28% by weight hydrocarbons (that is bitumen plus di`luent), 70 to 37% water and 22 to 43%
soli.ds. I:n comparison to the original D.C. tailings, the hydrocarbons are present in greater concentration in this product and some solids and most of the water have been rejected; in comparison to combined primary and secondary froth, the present product contai'ns perhaps twice as much water and three times as many soli:ds. I.n any event, the product is a feedstock wh;ch can feasi.bly be treated to recover contained hydrocarbons as a pure product.
The invention is characteri:zed by the following advantages:
(1) A large proport;on of the hydrocarbons in the D.C. tailings can no~ econom;cally be recovered in a more concentrated form and water and solids can s;'multaneously be rejected;
and (.2~ The froth product ;.s proportionately small in volume when compared w;.th the or;g;nal D. C. tail;ngs and ~s amenable to further treatment at reasonable cost to recover the b;:tumen ;:n pure form.
Braadly stated, the ;:nvent;:on is a method for treating tailings obta;.ned directly from the di'lution centr;:fuging circu;`t of a hot water extractian complex for the recovery of b;tumen from oil sands, said ta;l;ngs conta;ning bi.tumen, hydrocarbon d;luent, solids and water, compr;s;ng: ;ntroduci.ng only the ta;:lings into a flotation cell and re-taining it therein for a suffic;ent period of time, while subjecting it to ag;tat;on and flotat;on us;ng gas ;ntroduced ;nto the base of the body of tail;.ngs, to recover a s;gnificant port;on of the contained bitumen and diluent as froth from the cell and to reject a portion of the solids and ~ater as under flow; and removing the froth from further treatment.
~ - 5 -108~;~4Z
DESCRIPTION OF THE DRAWING
In the dra~ing:
F;gure 1 is a block diagram setting forth the steps of ; the process;
., .
.. , ;
,, , .
- 5a -~..
Figure 2 is a schematic diagram of the circuit used to carry out the experiments involved in developing the invention; and Figure 3 is a plot of hydrocarbon recovery versus retention time for a single cell system.
DESCRIPTION OF THE PREFERRED EMBODIMENT
STARTING MATERIAL
The pilot plant D. C. tailings, which formed the feedstock for the development work involved in this invention, comprised a mixture of scroll centrifuge tailings and disc centrifuge tailings provided in a ratio of about 1 to 12.
These two streams were blended and usually heated in a mix tank to form a mixture having a temperature of about 170F.
FLOTATION
This mixture was introduced into a conventional induced gas flotation cell or into the first of a bank of such cells. The laboratory pilot plant used to develop the in-vention is illustrated in Figure 2. It comprised an agitated heating tank 1 to which cold disc and scroll tailings were fed manually and mixed and heated to about 170F. The product was pumped through a line 2 to a series of 3 Denver* induced air flotation cells from which the froth and tailings products were obtained. (*trade mark).
; As previously mentioned, the most significant p~rameter with respect to the operation of the flotation cell was its retention time. As shown in Figure 3, the slope of the curve obtained by plotting hydrocarbon recovery against retention time was consistently steep until it changed suddenly at point "A", after which increased retention time yielded little increase in recovery. This finding requires that one should choose a cell having sufficient volume to provide a !
10~1164Z
retention time corresponding with or close to the retention time at which the slope of the curve changes suddenly, for the particular D. C. tailings feedstock being processed. Now this choice will, of course, be also influenced to some extent by the economics of cell size and the limited range of sizes which are commercially available.
It has also been found that the recovery-retention time curve for a single cell, such as is shown in Figure 3, provides a reliable indication of the performance of additional cells placed in series downstream from the first cell. In other words, a reliable scale up is achieved by using the data from a single cell for a plurality of cells operating downstream from it and receiving its underflow.
- There is a minimum agitation level required in the cell, below which "sanding out" can occur. More particularly, it is preferred to operate the vessel above a minimum power input of about 0.04 H.P./ft.3 of cell volume.
; It has also been found that there is an air injection rate above which there is little improvement in recovery. More particularly, it is preferred to operate the flotation cells at an aeration rate of less than 0.2 SCFM/cu.
ft. of cell volume, as this is sufficient to recover the hydrocarbon.
It is also preferred to use multiple cells in series to improve the ultimate recovery. These cells can all be operated at the same condition.
If desired, nitrogen may be used with sealed cells to avoid losing diluent to the atmosphere and to eliminate the safety hazard associated with air-naphtha vapor mixtures.
The invention is illustrated by the following examples.
, 7 !
EXAMPLE I
This example involves the operation of a single cell open to the atmosphere. About 250 pounds of scroll tail-ings and 350 Imperial gallons of disc tailings were placed in a tank and heated to 170F with agitation. The time re-quired to accomplish this heating was approximately one hour.
The analyses of the two tailings was as follows:
TABLE I (Run L13) Typical Typical Measured % by weight Scroll ~ailings Disc Tailings D.C. Tailings hydrocarbons 6.46 1.50 1.70 solids75.00 4.00 6.85 water18.50 94.50 91.45 This mixture was fed at 23.5 lbs./min. into a 0.8 cubic foot capacity flotation cell equipped with a Denver Sub-A type aeration impellor. Air was fed into the body of tailings through the impellor mechanism. The cell operating conditions were as follows:
retention time - 2.26 minutes j 20 impellor speed - 750 r.p.m.
air rate - 0.175 SCFM/cu. ft. of cell volume power input - 0.09 HP/cu. ft. of cell volume Froth and tailings products were obtained at respective rates of 1.59 and 21.91 lbs./min. and had the fol-lowing compositions:
TABLE II
% by weight Froth Tailings ; hydrocarbons 15.61 0.73 Solids 30,44 5.57 ; 30 Water 53.95 93.70 ,, ~ .
EXAMPLE II
', This example illustrates that a reliable scale ' ``
10~1~42 up is obtained by using recovery data developed by a single cell and applying it to a bank of cells operating under similar conditions.
The underflow or tailings from Example I was subjected to two additional flotation stages. With the excep-tion of retention time, the cell design and operating conditions were identical to those of Example I. The retention time varied slightly from cell to cell by virtue of the froth produced which tended to reduce the volume of material fed to the next cell. Table III summarizes the experimental results:
TABLE III- (Run L13) Cell 1 Cell 2 Cell 3 Retention Time per Cell - minute 2.26 2.42 2.47 Froth Produced lb./minute 1.59 0.39 0.27 Froth Composition -by weight hydrocarbons 15.61 18.09 17.64 solids 30.44 36.54 32.28 water 53.95 45.37 49.98 The total froth and final tCell 3) tailings were obtained at respective rates of 2.25 and 21.25 lb./minute and had the following composition:
TABLE IV- ~Run L13) by wei~t Total Froth Final Tailings hydrocarbons 16.28 0.19 solids 31.73 4.66 ' water 51.99 95.15 ! 3o Cell 1 recovered 60.89% of the hydrocarbon (bitumen plus naphtha) fed to the bank of cells. This number was used to calculate the hydrocarbon recovered in cells 2 and 3.
Table V shows a comparison between calculated and measured _ g _ , , 108~ 42 performance. The total hydrocarbon recovery for the cell bank was adequately predicted from the single cell value.
TABLE V- (Run L13) , Total Cell 2Ce'll' 3 (Cell l + Cell 2 + Cell 3) % of Cell 1 Feed Hydrocarbon Recovered Measured 17.5611.62 90.08 Calculated 23.819.32 94.02 EXA _ LE III
This example illustrates that hydrocarbon re-covery is insensitive to increases in cell air input in the range 0.175 to 0.512 SCFM/cu. ft. of cell volume. Therefore the preferred air input is less than 0.175 SCFM/cu. ft. of cell volume. Runs L25, L26 and L27 were carried out at three dif-ferent air rates while other operating conditions remained essentially constant. Runs L43, L44 and L45 were accomplished in a similar manner. The major difference between these two ; 20 sets of runs was in cell retention times which were nominally 0.9 minutes and 1.25 minutes respectively.
TABLE VI
Av. Input Cell 1 Run SCFM/cu. ft. cell Recovery L25 0.175 , 23.41 L26 0.325 23.86 ' L27 0.512 23.52 I L43 0.175 40.36 L44 0.325 46.58 L45 0.512 39.97 EXAMPLE IV
This example illustrates the single cell relationship between hydrocarbon recovery and retention time.
Such a correlation can be used in sizing banks of multiple cells.
1019164i~ 1 An important feature is that recovery initially increases steadily with retention time but eventually the slope of the curve changes abruptly and becomes flat, so that further increases in residence time yield relatively little improvement in recovery.
A num~er of experiments were undertaken in which tailings were prepared and passed through the flotation cell as described in Example I. Feed rates to the cell were varied such that cell retention times ranged from about 0.9 minutes to 5.2 minutes. Impellor speed and power input were maintained constant at 750 rpm and 0.09 H.P./cu. ft. of cell volume. Air rates ranged from 0.175 to 0.512 SCFM~cu. ft. of cell, but as shown in Example III the recovery is independent of air rate.
Figure 3 shows the recovery-retention time relationship obtained fr~m this series of runs.
, , . I
Claims (6)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method for treating tailings obtained directly from the dilution centrifuging circuit of a hot water extraction complex for the recovery of bitumen from oil sands, said tailings containing bitumen, hydrocarbon diluent, solids and water, comprising:
introducing only the tailings into a flotation cell and retaining it therein for a sufficient period of time, while subjecting it to agitation and flotation using gas introduced into the base of the body of tailings, to recover a significant portion of the contained bitumen and diluent as froth from the cell and to reject a portion of the solids and water as under flow; and removing the froth from further treatment.
introducing only the tailings into a flotation cell and retaining it therein for a sufficient period of time, while subjecting it to agitation and flotation using gas introduced into the base of the body of tailings, to recover a significant portion of the contained bitumen and diluent as froth from the cell and to reject a portion of the solids and water as under flow; and removing the froth from further treatment.
2. The method as set forth in claim 1 wherein:
the gas introduced for flotation is an inert gas which is recovered from the flotation cell and recycled to it.
the gas introduced for flotation is an inert gas which is recovered from the flotation cell and recycled to it.
3. The method as set forth in claim 2 comprising:
recovering inert gas, containing diluent vapor, from the flotation cell;
condensing diluent vapor from said recovered inert gas; and recycling the product inert gas to the flotation cell.
recovering inert gas, containing diluent vapor, from the flotation cell;
condensing diluent vapor from said recovered inert gas; and recycling the product inert gas to the flotation cell.
4. The method as set forth in claim 1 wherein:
the retention time of the flotation cell is about that at which the slope of the recovery-retention time line plotted for the cell and the dilution centrifuging circuit involved breaks sharply.
the retention time of the flotation cell is about that at which the slope of the recovery-retention time line plotted for the cell and the dilution centrifuging circuit involved breaks sharply.
5. The method as set forth in claim 4 wherein:
the flotation vessel is operated at an aeration rate of less than 0.2 SCFM of gas per cubic foot of cell capacity.
the flotation vessel is operated at an aeration rate of less than 0.2 SCFM of gas per cubic foot of cell capacity.
6. The method as set forth in claim 4 or 5 wherein:
the underflow from the flotation cell is introduced into a second flotation cell wherein it is subjected to agitation and flotation using gas introduced into the base of the body of underflow to recover contained bitumen as froth.
the underflow from the flotation cell is introduced into a second flotation cell wherein it is subjected to agitation and flotation using gas introduced into the base of the body of underflow to recover contained bitumen as froth.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA267,579A CA1081642A (en) | 1976-12-10 | 1976-12-10 | Recovery of hydrocarbons from dilution centrifuging tailings |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA267,579A CA1081642A (en) | 1976-12-10 | 1976-12-10 | Recovery of hydrocarbons from dilution centrifuging tailings |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1081642A true CA1081642A (en) | 1980-07-15 |
Family
ID=4107478
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA267,579A Expired CA1081642A (en) | 1976-12-10 | 1976-12-10 | Recovery of hydrocarbons from dilution centrifuging tailings |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1081642A (en) |
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8382976B2 (en) | 2009-04-09 | 2013-02-26 | Titanium Corporation Inc. | Recovery of bitumen from froth treatment tailings |
| US8656996B2 (en) | 2010-11-19 | 2014-02-25 | Exxonmobil Upstream Research Company | Systems and methods for enhanced waterfloods |
| US8657000B2 (en) | 2010-11-19 | 2014-02-25 | Exxonmobil Upstream Research Company | Systems and methods for enhanced waterfloods |
| US8739869B2 (en) | 2010-11-19 | 2014-06-03 | Exxonmobil Upstream Research Company | Systems and methods for enhanced waterfloods |
| US8852429B2 (en) | 2010-02-22 | 2014-10-07 | Titanium Corporation Inc. | Method for processing froth treatment tailings |
| US8974661B2 (en) | 2010-12-30 | 2015-03-10 | Exxonmobil Upstream Research Company | Methods for separation of bitumen from oil sands |
| US9314713B2 (en) | 2010-05-12 | 2016-04-19 | Titanium Corporation | Apparatus and method for recovering a hydrocarbon diluent from tailings |
| US9719022B2 (en) | 2009-04-09 | 2017-08-01 | Titanium Corporation Inc. | Methods for separating a feed material derived from a process for recovering bitumen from oil sands |
-
1976
- 1976-12-10 CA CA267,579A patent/CA1081642A/en not_active Expired
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8382976B2 (en) | 2009-04-09 | 2013-02-26 | Titanium Corporation Inc. | Recovery of bitumen from froth treatment tailings |
| US9719022B2 (en) | 2009-04-09 | 2017-08-01 | Titanium Corporation Inc. | Methods for separating a feed material derived from a process for recovering bitumen from oil sands |
| US10087372B2 (en) | 2009-04-09 | 2018-10-02 | Titanium Corporation Inc. | Methods for separating a feed material derived from a process for recovering bitumen from oil sands |
| US8852429B2 (en) | 2010-02-22 | 2014-10-07 | Titanium Corporation Inc. | Method for processing froth treatment tailings |
| US9314713B2 (en) | 2010-05-12 | 2016-04-19 | Titanium Corporation | Apparatus and method for recovering a hydrocarbon diluent from tailings |
| US8656996B2 (en) | 2010-11-19 | 2014-02-25 | Exxonmobil Upstream Research Company | Systems and methods for enhanced waterfloods |
| US8657000B2 (en) | 2010-11-19 | 2014-02-25 | Exxonmobil Upstream Research Company | Systems and methods for enhanced waterfloods |
| US8739869B2 (en) | 2010-11-19 | 2014-06-03 | Exxonmobil Upstream Research Company | Systems and methods for enhanced waterfloods |
| US8974661B2 (en) | 2010-12-30 | 2015-03-10 | Exxonmobil Upstream Research Company | Methods for separation of bitumen from oil sands |
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