CA1146897A - Recovery of bitumen from tar sands sludge using additives - Google Patents

Abstract

ABSTRACT

Improved method for the treatment of sludge from a water storage retention pond used to store the tailings discharged from a tar sands water extraction process. The method involves mixing the sludge, prior to its processing, with an effective amount of a bitumen flotation promoter, e.g., an ammonium lignin sulfonate whereby a froth is formed. The froth is separated and processed. The use of the promoter increases substantially the recovery of the bitumen from the sludge.

Description

BACKGROUND OF THE INVENTION

The present invention relates generally to an improvement in the recovery of bitumen from tar sands. The invention further relates to an improvement in the recovery of bitumen in water processes of extracting bitumen from tar sands. This invention particularly relates to the improved treatment of tailings dis-charged from a water extraction process and the improved treatment of tailings retained in a water storage retention pond. More par-ticularly, this invention relates to an improved method of treat-ing the sludge layer from a retention pond to recover bitumen froth therefrom using certain additives.

Tar sands are also known as oil sands or bituminous sands. The sand deposits are found in numerous locations throughout the world, e.g., Canada, United States, Venezuela, Albania, Rumania, Malagasy and U.S.S.R. The largest deposit, .. 1 ~

and the only one of present commercial importance is in the northeast of the Province of Alberta, Canada.

Tar sand is a three-component mixture of bitumen, mineral and water. Bitumen is the component for the extraction of which tar sands are mined and processed.
The bitumen content is variable, averaging 12 wt.% of the deposit, but ranging from 0 to 18 wt.%. Water typically runs 3 to 6 wt.% of the mixture, increasing as bitumen content de-creases. The mineral content constitutes the balance.

Several basic extraction methods have been known for many years for separating the bitumen from the sands. In a "cold-water" method, the separation is accomplished by mixing the sands with a solvent capable of dissolving the bitumen.
The resulting mixture is then introduced into a large volume of water, water with a surface agent added, or a solution of a neutral salt in water. The combined mass is then subjected to a pressure or gravity separation.

The "hot-water" process for primary extraction of bitumen from tar sands consists of three major process steps (a fourth step, final extraction, is used to clean up the recovered bitumen for further processing). In the first step, called conditioning, tar sand is mixed with water and heated with open steam to form a pulp of 70-85 wt.% solids. Sodium hydroxide or other reagents are added as required to maintain the pH in the range of about 8.0-8.5. In the second step, called separation, the conditioned pulp is diluted further so that settling can take place. The bulk of the sand-sized particles (greater than 325 mesh screen) rapidly settles and 1~68~7 is withdrawn as sand tailings. Most of the bitumen rapidly floats (settles upward) to form a coherent mass known as bitu-men froth which is recovered by skimming the settling vessel.
An aqueous middlings layer containing some mineral and bitumen is formed between these layers. A scavenger step may be con-ducted in the middlings layer from the primary separation step to recover additional amounts of bitumen therefrom. This step usually comprises aerating the middlings. The froths recovered from the primary and scavenger step can be combined, diluted with naphtha and centrifuged to remove more water and residual mineral. The naphtha is then distilled off and the bitumen is coked to a high quality crude suitable for further processing.
Hot water processes are described in U.S. Patents Nos.
3,487,003; 3,496,0g3; 3,502,565; 3,502,566; 3,502,575; 3,526,585;
3,951,800; 3,951,779; 3,509,641 and 3,751,358. Tailings can be collected from the aforementioned processing steps and gen-erally will contain solids as well as dissolved chemicals. The tailings are collected in a retention pond in which additional separation occurs. The tailings can also be considered as processing water containing solids which are discharged from the extraction process. The tailings comprise water, both the natural occurring water and added water, bitumen and mineral.

The mineral particle size distribution is particularly significant to operation of the hot water process and to sludge accumulation. The terms sand, silt and clay are used in this specification as particle size designations. Sand is siliceous material which will not pass through a 325 mesh screen. Silt will pass through a 325 mesh screen, but is larger than two microns and can contain siliceous material.

Clay is smaller than 2 microns and also can contain siliceous material. The word fines as used herein refers to a combina-tion of silt and clay.

Conditioning tar sands for the recovery of bitumen consists of heating the tar sand/water feed mixture to process temperature (180~200F), physical mixing of the pulp to uniform composition and consistency, and the consumption (by chemical reaction) of the caustic or other added reagents. Among the added reagents are phosphates as disclosed in U. D. Patent No. 3,422,000; sodium hydroxide and sodium tripolyphosphate as disclosed in U.S. Patent No. 3,556,982; alkali metal bicar-bonates as disclosed in U.S. Patent No. 4,120,777; and the product resulting from the addition of ammonium hydroxide to a~ueous tannic acid as disclosed in U.S. Patent No. 3,953,317.
Also non-foaming wetting agents including nonionic detergents are often added. Under the aforementioned conditions, bitumen is stripped from the individual sand grains and mixed into the pulp in the form of discrete droplets of a particle size on the same order as that of the sand grains. During conditioning, a large fraction of the clay particles become well dispersed and mixed throughout the pulp. The conditioning process which prepares bitument for efficient recovery during the following process steps also prepares the clays to be the most difficult to deal with in the tailings disposal operation.

The other process step, called separation, is actually the bitumen recovery step, the separation having already occurred dur~ng conditioning. The conditioned tar sand pulp is screened to remove rocks and unconditionable lumps of tar sands and clay. The reject material, "screen ~6~'7 oversize", is discarded. The screened pulp is further diluted with water to promote two settling processes. Globules of bitumen, essentially mineral-free, float upward to form a coherent mass of froth on the surface of the separation units; and, at the same time, mineral particles, particularly the sand size material, settle down and are removed from the bottom of the separation unit as sand tailings. These two settling processes take place through a medium called the middlings. The middlings consist primarily of water, bitumen particles and suspended fines.

The particular sizes and densities of the sand and of the bitumen particles are relatively fixed. The parameter which influences the settling processes most is the viscosity of the middlings. Characteristically, as the suspended material content rises above a certain threshold, which varies according to the composition of the suspended fines, viscosity rapidly achieves high values with the effect that the settling processes essentially stop. Little or no bitumen is recovered and all streams exiting the unit have about the same composition as the feed. As the feed suspended fines content increases, more water must be used in the process to maintain middlings viscosity within the operable range.

The third step of the hot water process is scavenging.
The feed suspended fine content sets the process water require-ment through the need to control middlings viscosity which, as noted before, is governed by the clay/water ratio. It is usu-ally necessary to withdraw a drag stream of middlings to main-tain the separation unit material balance, and this stream of middlings can be scavenged for recovery of incremental amounts t~71 of bitumen. Air flotation is an effective scavenging method for this middlings stream.

Final extraction or froth clean-up is usually accom-plished by centrifugation. Froth from primary extraction is diluted with naphtha, and the diluted froth is then subjected to a two stage centrifugation. This process yields an oil pro-duct of essentially purel but diluted, bitumen. Water and mineral and any unrecovered bitumen removed from the froth constitutes an additional tailing stream which must be disposed.

In the terminology of extractive processing, tailings are a throwaway material generated in the course of extracting the valuable material from the non-valuable material. And in tar sands processing tailings consist of the whole tar sand plus net additions of process water less only the recovered bitumen product. Tar sand tailings can be subdivided into three categories: (1) screen oversize; (2) sand tailings -the fraction that settles rapidly, and (3) middlings - the fraction that settles slowly. Screen oversize is typically collected and handled as a separate stream.

Tailings disposal is all the operations required to place the tailings in a final resting place. Because the tail-ings contain bitumen emulsions, finely dispersed clay with poor settling characteristics and other contaminants, water pollution considerations prohibit discarding the tailings into rivers, lakes or other natural bodies. Currently the tailings are stored in retention ponds (also referred to as evaporation ponds) which involve large space requirements and the construction of expen-sive enclosure dikes. A portion of the water in the tailings '7 can be recycled back into the water extraction process as an economic measure to conserve water. Currently two main operat-ing modes for tailings disposal are (1) dike building -hydraulic conveying of tailings followed by mechanical com-paction of the sand tailings fraction; and (2) overboarding -hydraulic transport with no mechanical compaction.

At one commercial location, for dike building, tailings are conveyed hydraulically to the disposal area and discharged onto the top of a sand dike which is constructed to serve as an impoundment for a pool of liquid contained in-side. On the dike, sand settles rapidly and a slurry of water, silt, clay and minor amounts of bitumen, as well as any chemical used during processing flows into the pond interior. The settled sand is mechanically compacted to build the dike to a higher level. The slurry which drains into the pond interior commences stratification in settling over a time scale of months and years. As a result of this long term settling, three layers form. The top layer, e.g., 5-10 feet of the pool, i8 a layer of relatively clear water containing minor amounts of solid, e.g., up to 5 wt.% and any dissolved chemicals. This layer of pond water can be recycled to the water extraction process without interfering with extraction of bitumen from tar sands. Below this clear water layer is a continuity in solid contents. Over a fe~ feet, solids content increases to about 10-15 wt.% and thereafter, solids contents increase regularly toward the pond bottom. In the deeper parts of the pond solid contents of over 50 wt.% have been measured. This second layer is commonly called the sludge layer. In general ~6~

the sludge layer can be characterized as having more than 10 wt.% of solids (which is defined as mineral plus bitumen).
More particularly the sludge can be characterized as having 20 wt.% to 50 wt.% solids. Also the sludge can be characterized as having about 0.5 to about 20 wt.% bitumen. The solids con-tents of the sludge layer increase regularly from top to bottom by a factor of about 4-5. Portions of the solids are clays.
The clays, dispersed during processing, apparently have partially reflocculated into a fragile gel network. Through this gel, particles of larger-than-clay sizes are slowly settling. Gen-erally this sludge layer cannot be recycled to the separation step because no additional bitumen is extracted. A third layer formed of sand also exists.

Overboarding is the operation in which tailings are discharged over the top of the sand dike directly into the liquid pool. A rapid and slow settling process occurs but this distinction is not as sharp as in the previously described dike building and no mechanical compaction is carried out.
The sand portion of the tailings settles rapidly to form a gently sloping beach, extending from the discharge point toward the pond interior. As the sand settles, a slurry drains into the pool and commences long-term settling. Water in ponds prepared by both dike building and overboarding can be in-cluded in the general definition of sludge in the present de-scription.

Methods for treating sludge formed in a retention pond used to store tailings from a hot water extraction of bitumen from tar sands are disclosed in Canadian Patents Nos.
975,696; 975,697; 975,698; 975,699 and 975,700. The first mentioned Canadian Patent discloses removing sludge from a pond, placing the sludge in an air scavenger treating zone wherein the sludge is aerated and agitated concurrently to form an upper bitumen froth layer and a lower tailings of water and mineral water. The lower tailings can be discharged into a retention pond. The upper bitumen froth is sent to a settling zone wherein two layers are formed, an upper bitumen layer reduced in mineral matter and water and a lower layer comprised substantially of mineral matter and water with minor amounts of bitumen. The latter lower layer is recycled back to the air scavenger treating zone while the upper bitumen layer is processed further to recover the bitumen. This Canadian patent and the others also disclose that sodium sili-cate can improve bitumen recovery when used in connection with the aeration and agitation. Canadian Patent No. 975,697 dis-closes a process similar to that described in the previous patent with an additional step in that a portion of the lower layer, which otherwise would be recycled back to the air scavenger treating zone, is returned to the retention pond. Canadian Patent No. 975,690 discloses feeding the sludge from a retention pond to an air pressure zone wherein the sludge is aerated at superatmospheric pressure to aerate bitumen in the sludge.
Canadian Patent No. 975,699 discloses feeding sludgé recovered from a retention pond to aeration and settling zones and per-mitting the sludge to form an upper froth layer and a lower tailings layer. Canadian Patent No. 975,700 discloses feeding sludge to an air scavenger treating zone wherein the sludge is aerated and agitated concurrently and resulting froth is aerated and agitated concurrently and resulting froth is separated in the scavenger treating zone, while the tailings 11~6~97 are returned to the pond. However, none of the foregoing Canadian patents disclose or suggest that the additives that the applicants disclose would be suitable for treating sludge removed from a retention pond.

SUMMARY OF THE INVENTION

Present invention is an improved method for processing sludge formed in a retention pond used to store tailings obtained from the water extraction of bitumen from tar sands. The process involves removing sludge from a retention pond, agitating and aerating concurrently the sludge in the presence of a bitumen flotation promoter, e.g., ammonium lignin sulfonate, which facilitates the separation of bitumen from the sludge.
The resulting froth, containing bitumen, is separated from the treated mixture, and can be processed in a similar manner to the froth obtained from the primary and scavenger steps. Also present invention involves a composition comprising sludge and an effective amount of bitumen flotation promoter.

DESCRITPION OF THE DRAWING

The attached drawing is a schematic representation of one of applicants' embodiments as it relates to a hot water extraction process.

DETAILED DESCRIPTION

Referring now to a single figure, tar sands are fed into the system through a line 1 and pass to a conditioning drum (or muller) 30. Water and steam are introduced to the drum 30 through another line 2. The total water so introduced in liquid and vapor form is a minor amount based on the weight of the tar sands processed. The tar sands conditioned with water, pass through a line 3 to the feed sump 31 which serves as a zone for diluting the pulp with additional water via line 20 before passage to the separation zone 32. The addi-tional water 20 may be clear pond water.

The pulp tar sands are continuously flushed from the feed sump 31 through a line 4 into separator zone 32.
The settling zone within the separator 32 is relatively quies-cent so that bitumen froth rises to the top and is withdrawn via line 5 while the bulk of the sand settles to the bottom as a tailings layer which is withdrawn through line 6.

A middlings tailings stream is w_thdrawn through line 7 to be processed as described below. Another middlings stream, which is relatively bitumen-rich compared to the stream with-drawn through line 7, is withdrawn from the unit via line 8 to a flotation scavenger zone 33. In this zone, an air flotation operation is conducted to cause the formation of additional bitumen froth which passes from the scavenger zone through line 9 in mixture with the primary froth from the separator 32 to a froth settler 34. A bitumen-lean water stream is removed from ~he bottom of the scavenger zone 33 through line 10 to be further processed as described below. In the settler zone 34, some further bitumen-lean water is withdrawn from the froth and removed through line 11 to be mixed with the bitumen-lean water stream from the flotation scavenger zone 33, the sand tailings stream from the separation zone 32 and a portion of the lower middlings withdra~m via line 21 from the separation zone 32. The bitumen froth from the settler 34 is removed through line 12 for further treatment.

The bitumen-lean water from the froth settler 34, the scavenger zone 33 and the separator 32, all of which make up a tailing discharge stream which can be collected and handled via a dike building or overboarding operation previously described. The tailing discharge stream via line 13 can be fed to distribution pipe 14. The distribution piping provides for continuous and uniform delivery of the effluent 15 to the pond 35. The latter can be considered another separation zone;
it is a zone of quietness. Both the dike building and over-boarding operation result in what is commonly referred to as a pond, particularly a retention pond. And as previously described, three layers are formed in the pond. They are (1) a top water layer relatively free of clay and bitumen and which can be recycled; (2) a middle layer consiting of bitumen and mineral (defined as not being soluble in toluene); and (3) a bottom layer having a relatively high concentration of sand. The middle layer of the pond is often referred to as sludge.

The sludge is continuously being formed in a time span of many months and even years. As a result its character-istics are different from those of the middlings layer drawn off from the separation zone 32 via lines 7 and 8.
Some of the differences include that the middlings layer has a higher pH (e.g., about 8.4) whereas the sludge can have a lower pH (e.g., about 7.3). The differences in pH

reflect changes which are not fully understood but which are ~G~5~7 occurring in the pond. Another difference between the sludge and middlings streams (via lines 7 and 8) is the weight percent of mineral, e.g., the middlings stream contains about a lower 8-12 wt.% whereas the sludge contains a higher weight %.

Applicants' improved method comprises withdrawing sludge from the pond 35 by known means, for example, line 16 which opening is maintained in the sludge layer and which line is attached to suction pump 36. Line 17 from the latter, carries the sludge to treating zone 37. In applicants' in-vention, an effective amount of the promoter is admixed with the incoming sludge 17 or added to treating zone 37. The promoter can be added to the treating zone 37, e.g., via line 18. Other combinations can be used. The resulting froth con-taining bitumen can be separated and forwarded to additional processing via line l9 while the remaining material can be returned to the same pond or a different pond (not shown) via line 20.

Agitation (not shown) within treating zone 37 can be by known means such as stirring while the aeration (not shown) also can be by known means such as forcing air through a porous pipe in the bottom of the treating zone 37. Other alternatives and combinations are known to those skilled in the art. The amount of agitation and aeration can vary over a wide range with economic considerations suggesting that the minimum necessary to achieve the desired separation of bitumen is preferred. Further, the amount of agitation and aeration may vary depending, in part, on how much promoter is used. As demonstrated hereinafter, both agitation and aeration may be necessary, either one by itself is not effective.

'7 The promoter used to contact the sludge in contacting zone 37 is a material that facilitates the separation of the bitumen contained in the sludge. The promoter is not a flota-tion agent in the sense that the latter is used in the con-centration of minerals wherein the agent concentrates the minera. (~ discussion as to the theory how such agents work and a list of many such agents, see Kirk-Othmer, Encyclopedia of Chemical Technology, 1st Edition, Vol. 6). Since the purpose of the promoter used herein is to concentrate the bitumen in a froth and leave behind the mineral it could be classified as a bitumen flotation promoter, and which is selected from the group consisting of phosphates including the salts of alkali metals or NH4, creosotes, phenols, phenol derivatives, starches, modified starches, lignin sulfonates including the salts of alkali metals or NH4, and polycarboxylates including the sodium salts. Preferred phosphates are sodium hexa-metaphosphate, trisodium phosphate, sodium tripolyphosphate, sodium pyrophosphate, sodium phosphate, disodium hydrogen phosphate and monosodium hydrogen phosphate. Creosote, when obtained by the destructive distillation of wood tar, is a mixture of phenols and phenol derivatives. The phenols are a class of aromatic organic compounds in which one or more hydroxyl groups are attached directly to the benzene ring;
examples are phenol itself (benzophenol1 cresols, xylenols, resorcinol and naphthols. Examples of phenol derivatives include alkali metal salts of phenols. Creosote is also ob-tained by distillation of coal-tar.

Starches are generally derived from corn, potatoes, ~6~7 wheat and other known sources. Modified starches are derived from starches which have been modified by acetylation, chlori-nation, acid hydrolysis or enzymatic action. Lignin sulfonates are metallic or ammonium sulfonates made from lignins of sul-fite pulp mill liquors. Preferred lignin sulfonates are potassium, sodium and ammonium. A polycarboxylate can, for example, result from the polymerization of any of a broad array of organic acids comprising chiefly alkyl (hydrocarbon) groups usually in a straight chain terminating in a carboxyl radical (-COOH). The acid is polymerized and when the terminal acid groups are reacted with bases, e.g., sodium hydroxide, a sodium salt of the polycarboxylate results. More preferred promoters are sodium polycarboxylates and ammonium lignin sulfonate.

The amount of promoter used is an effective amount in that it will facilitate the separation of the bitumen from the sludge and can vary over a wide range. While economics will determine the amount used in a commercial operation, generally the range will be about 10 to 10,000 parts of pro-moter per million parts by weight of sludge with 40 to 5000 parts preferred. The resulting novel composition comprising the sludge and a bitumen flotation promoter is also appli-cants' invention. The composition comprises tar sands sludge containing more than 10 wt.~ solids including 0.5 to 20 wt.~
bitumen and an effective amount of bitumen flotation promoter which enhances the separation of the bitumen from the sludge when the composition is agitated and aerated.

The promoter, as indicated previously, can be incor-porated with the sludge prior to or during the agitation and ~46~

aeration. With different sludges the optimum amount of promoter can vary as well as the amount of agitation and aeration. The the optimum amounts can be determined without undue experimentation.

After the mixture of sludge and promoter and sludge has been sufficiently agitated and aerated in treating zone 37 the resulting mixture can be transferred via line 19 to separation zone 38 wherein the froth is permitted to separate.
In separation zone 37 two layers are formed, an upper bitumen froth layer reduced in mineral matter and water and a lower layer comprised substantially of mineral matter and water with minor amounts of bitumen therein. The separated froth (upper layer) could be fed via line 21 to the froth settler zone 34, admixed with separation zone froth and thus processed in the same manner as the froth obtained from the separation zone 32. An alternative could be to bypass the froth settler zone 34 and feed into line 12. The remaining materials (lower layer), that is, the tailings containing water and the mineral obtained as a result of the contacting in treating zone 36 can be returned via line 20 to pond 35 or a different pond (not shown).

The result of treating the sludge by applicants' method is that the amount of bitumen remaining in the tailings from treating zone 36 is substantially reduced. For example, with one promoter the amount of bitumen removed from the sludge, depending in part on the concentration of additive used, ranges from 78 to 82 wt.%. Another result of applicants' method is that the ratio of bitumen to mineral increases, e.g., the sludge can have a bitumen/mineral ratio of 0.27 whereas the bitumen froth from the contacting zone 36 has a ratio of 0.89 to 1.5 depending on the concentration of additive and the type. The higher ratio facilitates treatment of the froth.
Advantages of applicants' method include the fact that more bi-tumen is ultimately recovered from the tar sands and the amount of tailings requiring storage can be reduced. Both of the fore-going economically enhance the tar sands operation.

Essentially, the improvement of the present invention is the method of recovery of bitumen from sludge by agitating and aerating sludge recovered from a retention pond used to store tailings from water extraction of bitumen from tar sands and separating resulting froth containing bitumen formed during the agitation and aeration comprises admixing an effective amount of the bitumen flotation promoter with the tar sands sludge thereby enhancing the separation of bitumen from the sludge.

The following examples illustrate the invention.
Comparative examples are also provided.

EXAMPLES

The procedure used to illustrate applicants' method was as follows. To a Western Machinery Flotation Cell wa~
charged 3000 grams of tar sand sludge consisting of 6 wt.%
bitumen, 22 wt.~ mineral and 72 wt.~ water. The sludge had a pH of 7.1. The Cell consists of a vessel and means for agita-tion and aeration. The means for agitation are located about

2/3 down inside the vessel. The agitation means consist of two parallel plates connected by a series of rods located toward the outer edges, the effect being that of a cage. Inside the outer cage is a similar but smaller cage which is turned by a hollow shaft which goes upward through the outer plate and is connected to a power source which rotates the inner cage.
The outer cage is connected to the shaft and the inner cage so that when the inner cage rotates the outer one remains stationary. The net effect is a high shear agitation. The hollow shaft provides the means for passing air, or other gases, down into the material being agitated.

The additives charged to the Cell and the amounts used are shown in the accompanying Table I. The length of time for running the cell is also shown in Table I. In the case of the run containing a promoter, the promoter was added to the vessel and the machine was run for 15 minutes. After stop-ping the machine, the froth was removed by scraping it from the vessel and placing it in a separate container. The sequence was repeated once and the resulting total froth analyzed. The analyses are reported in Table I.

The comparative run (1), without additive, involved running the Cell for three fifteen minute intervals. Compari-son of the data in accompanying Table I indicates that agitation and aeration of the sludge by itself caused only a 30 wt.%
bitumen recovery (i.e., the amount of bitumen contained in the froth over the amount of bitumen contained in the charge to the cell) despite the additional 15 minutes of operation.

In contrast, use of a promoter in connection with applicants' method, as demonstrated by runs 2-6 increased bitumen recovery. The amount of bitumen recovery increased to 40-82 wt.% despite a 15 minutes shorter operation time com-pared to Run 1.

~4689~

Runs 7 and 8 indicate that sodium polyphosphates are an effective promoter. These runs also indicate that a third 15 minutes of agitation and aeration increases overall bitumen recovery.

Comparative runs using sodium silicate and agitation only or aeration only clearly demonstrated the need for both concurrently.

Three additional runs were performed as previously ~5 described except that the froth was skimmed continuously with the unit running rather than stopping the unit first and then skimming the froth. The results of the three runs are shown in Table II.

--o z--~ ~ ~1~6~7 ~; ~
,, a) ~ ,~ ~ ~ Ln r~ ~ er ~ o E~ ~ ~ N 1~ Il) ~ CO CS~Lt~
O ~
~ a~ o o _I o o o _i o oo o '1 0 ~
m-, H 1~ m ~ ~ ~ ~ ~o ~9 ~
o ~ co co _/ o a~ 1 0 ~ O I ~ OD 1` r-- CO ~Lr) ~ ~1 ,1 o ~n a) ~
~; 0 d~ .,1 o H

S~ ~ ~ O~ ~ ~ ~ O ~ U~
S~ ~ ~
:E: 3 OdP ~0 r~l o ~ _l ~
~0 ~ 10 ~ ~ ~n m o m_d~ ~

H ~, o ~ ~4~ ~ ~ -~ O ~ I O ~
~10 I + ~ O
O ~ I 11 ~~ _~ ~
O~--~ + + Z
~~ a~ u~ u) + + + +~d V
P~~ C~ ~ V ~
O ~ ~0 ` 0 V
O ~ ., 0 0 0 0 U~ O O O O
1: 0 /~ I o o 11~ r o o L~ 0 ~ ~ O ~ ~ ~ I O
O O

_I ~ 0 a~ ~
~ ~a S~ ~ ~ 0 I ~ O
~ ~1 0 ^ P~
_I a) _I ~I n~ 0 ~1 O ~
a) ~ ~ ~ ~= o .~ ~ ~, e e e~ ~ ~ e O E~
~1 I O 1-l O O~
~ ' æ

zl ~ ~ ~ ~ u~

TABLE II
Promoter Enhances Bitumen Recovery Amount of ~ Bitumen Recovered Run Promoter Additive-ppm after 40 minutes 1 None - 69 2 Creosote 100 81

3 Dextrin 200 74 Dextrin is a starch gum formed by the hydrolysis of a starch and is an example of a modified starch. Others are known to those skilled in the art. Use of creosote or dextrin (runs 2 and 3) increased the amount of bitumen recovered compared to the use of no promoter (run 1).

Additives, which when used in the Cell, did not increase bitumen recovery from the sludge were sodium carbonate, sodium bicarbonate, sodium n-alkyl sulfates, and petroleum sulfonates.

Claims (5)

CLAIMS:

1. In the method of recovering bitumen from sludge by agitating and aerating sludge recovered from a retention pond used to store tailings from water extraction of bitumen from tar sands, and separating resulting froth containing bitumen formed during the agitation and aeration, the improve-ment comprises:
admixing with the sludge an effective amount of a bitumen flotation promoter selected from the group consisting of phosphates, creo-sotes, phenols, phenol derivatives, starches, modified starches, lignin sulfonates and polycarboxylates.

2. Improvement according to Claim 1 wherein the amount of additive is in the range between from about 10 parts to about 10,000 parts of additive per million parts by weight of sludge.

3. Improvement according to Claim 2 wherein the sludge is from a hot water bitumen extraction tar sands process.

4. Composition comprising tar sands sludge contain-ing more than 10 wt.% solids including 0.5 to 20 wt.% bitumen and an effective amount of bitumen flotation promoter selected from the group consisting of phosphates, creosotes, phenols, phenol derivatives, starches, modified starches, lignin sul-fonates and polycarboxylates to enhance the separation of the bitumen from the sludge when the composition is agitated and aerated.

5. Composition according to Claim 4 wherein the amount of the promoter is in the range between from about 10 parts to about 10,000 parts of additive per million parts by weight of sludge.