CA2882172A1

CA2882172A1 - Process of fines removal from oilsands bitumen

Info

Publication number: CA2882172A1
Application number: CA2882172A
Authority: CA
Inventors: Jun Zhao; Murray Gray; Qi Liu; Mainak Ghosh; James Dunn
Original assignee: University of Alberta
Current assignee: University of Alberta
Priority date: 2015-02-17
Filing date: 2015-02-17
Publication date: 2016-08-17
Also published as: CA2920131A1

Abstract

A process for the separation of oil from bitumen froth, said process comprising: the removal of bitumen froth resulting from bitumen extraction from oilsands, said bitumen froth containing water, fine solids and bitumen; heating the bitumen froth for a period of time sufficient to change the wettability of the fines contained therein; optionally, adding an aqueous solvent to the bitumen froth;
filtering the resulting solution at an elevated temperature; extracting the fine solids from the resulting solution in a first stream; extracting the clean bitumen from the resulting solution in a second stream; and optionally, extracting the gas/liquid phase from the resulting solution in a third stream.

Description

PROCESS OF FINES REMOVAL FROM OILSANDS BITUMEN
FIELD OF THE INVENTION
The present invention relates to a process for the removal of solids from bitumen slurry, more specifically this process is directed to the removal of fines from bitumen froth from the oilsands extraction.
BACKGROUND AND PRIOR ART
The extraction of bitumen from the oilsands gives recovered bitumen that is contaminated with fine solids.
Aqueous extraction of bitumen from tile oilsands gives a froth of bitumen, water, and fine solids that forms stable emulsions. Bitumen froth contains about 10-15% water, 5-10% fines solids and 80-85%
bitumen. Nonaqueous (i.e. solvent) extraction of oilsands gives bitumen contaminated with highly hydrophobic solids and water. Most of the fines and some water in these bitumen streams can be separated by filtration after a hydrothermal reaction at about 390 C for 30 min. The hydrothermal reaction modifies the wettability of the fine solids to enable easy filtration. This approach has significant advantages over the current paraffinic froth treatment technology, which results in the loss of 8%
of the bitumen, and over filtration of the untreated fine solids from non-aqueous extracted bitumen.
Bitumen froth is contaminated with water and fine solids. These contaminants must be reduced to 0.5 vol% and circa 300 ppm respectively to give feed acceptable to refineries.
Cleaning of bitumen froth currently requires expensive centrifugation steps, which are only partly effective or paraffinic precipitation of about 8% of the bitumen to remove water and fine solids. Removal of all the fine solids without loss of bitumen is desirable.
US 3,901,791 discloses a method where raw bituminous froth is first diluted with a liquid hydrocarbon boiling in the range of 350-750F and thereafter transferred to an autoclave settling zone wherein the diluted froth, in combination with a recycle centrifugal froth hereinafter described, is settled to provide an upper froth layer, a water layer, and a lower mineral tailings layer. The tailings layer is thereafter withdrawn from the autoclave settling zone, diluted with diluents similar to that added to the raw bitumen froth, and thereafter transferred to a centrifuge which is preferably a scroll centrifuge wherein a centrifugal froth product is recovered and recycled to the autoclave settling zone. By this process, a froth product substantially reduced in mineral matter and water and thereby suitable for further refining with well-known petroleum refining techniques is provided.

US 5,236,577 discloses a process for treating bitumen froth containing mixtures of a hydrocarbon component, water and solids. The process requires heating bitumen froth to a temperature in the range of about 80 C. to about 300 C., preferably in the range of 100 C. to 180 C., under pressure of about 150 to about 5000 kPa, preferably in the range of 800 to about 2000 kPa. The process requires passing the heated froth through a plurality of separation stages in series, and gravity settling the solids and water from the hydrocarbon layer while maintaining said elevated temperature and pressure.
The process preferably requires a diluent miscible with the bitumen to be mixed with the bitumen froth in an amount of 0 to about 60 per cent by weight of the bitumen, preferably in an amount of 15 to 50 per cent by weight of the bitumen in a mixing stage for preconditioning of the froth prior to each gravity separation stage.
US 4,648,964 discloses a process suitable for separating the hydrocarbon fraction from a tar sands froth. The process is said to require heating a fluid stream comprising the froth to above about 300 C., then pressurizing the stream to above about 1000 psig and separating the hydrocarbon fraction, having less than 1 percent solids and less than 5 percent water, from the treated stream. The description states that the separation is preferably done by gravitational settling in a settler and is said to occur substantially instantaneously. The description also states that the heat/pressure treatment can be optionally followed by addition of a diluent, such as naphtha.
CA 2,217,300 discloses a method for cleaning bitumen froth comprising hydrocarbon and aqueous phases and containing water and particulate solids contaminants dispersed in the hydrocarbon phase in the form of an emulsion, said froth having been produced by a water extraction process practiced on oil sand, comprising: adding a sufficient amount of paraffinic solvent to the froth to induce inversion of the emulsion;
mixing the froth and the solvent for a sufficient time to disperse the solvent in the froth; subjecting the mixture to gravity or centrifugal separation for a sufficient period to separate substantially all of the water and solids from the bitumen to produce dry diluted bitumen; and pumping the dry diluted bitumen through a pipeline to an upgrading circuit.
CA 2,103,508 discloses a process for the thermal rearrangement of a water emulsion, or a mixture with water, of a feedback selected from the group consisting of tar sand bitumen, heavy oil, refinery residue and a heavy waste oil stream, the feedstock containing a naturally-occurring, finely-divided mineral material water emulsion or the water mixture with a gas selected from the group consisting of synthesis gas and carbon monoxide in the presence of a catalytic amount, of about 0.03 to about 15%, of a bifunctional catalyst that facilitates the water gas shift reaction and also promotes the hydrogenation and stabilization of cracking

2 reaction products, the bifunctional catalyst including the naturally-occurring, finely-divided mineral material which is contained in the feedstock the process being conducted under such conditions of pressure and temperature that a water gas shift reaction occurs.
In light of the above, there still exists a need to provide a process to recover bitumen from oilsands froth through a simple, robust process which does not require the addition of chemicals.
SUMMARY OF THE INVENTION
Nonaqueous (i.e. solvent) extraction of oilsands gives bitumen contaminated with highly hydrophobic solids and water. Most of the fines and some water in these bitumen streams can be separated by filtration after a hydrothermal reaction at about 390 C for 30 mm. The hydrothermal reaction according to the present invention modifies the wettability of the fine solids to enable easier filtration than would typically be possible. One advantage of the present invention over the current paraffinic froth treatment technology is that the latter results in the loss of approximately 8% of the bitumen. The process according to the present invention is also more desirable than known processes of filtration of untreated fine solids from non-aqueous extracted bitumen as it involves no addition of chemicals.
According to a first aspect of the present invention, there is provided a process for the separation of oil from bitumen froth, said process comprising:
- removal of bitumen froth resulting from bitumen extraction from oilsands, said bitumen froth containing water, fine solids and bitumen;
- heating the bitumen froth for a period of time sufficient to change the wettability of the fines contained therein;
- optionally, adding an aqueous solvent to the bitumen froth;
- filtering the resulting solution at an elevated temperature;
- extracting the fine solids from the resulting solution in a first stream;
- extracting the clean bitumen from the resulting solution in a second stream; and - optionally, extracting the gas/liquid phase from the resulting solution in a third stream.
Preferably, the bitumen froth is heated at a temperature in the range of 300 to 400 C. More preferably, the bitumen froth is heated at a temperature in the range of 380 to 400 C. Even more preferably, the bitumen froth is heated at a temperature in the range of 390 to 400 C in a high pressure autoclave.

3 According to another aspect of the present invention, there is provided a process for the separation of oil from bitumen froth, said process comprising:
- removal of bitumen froth resulting from bitumen extraction from oilsands, said bitumen froth containing water, fine solids and bitumen;
- heating the bitumen froth for a period of time sufficient to change the wettability of the fines contained therein;
- optionally, adding an aqueous solvent to the bitumen froth;
- filtering the resulting solution at an elevated temperature;
- extracting the fine solids from the resulting solution in a first stream;
- extracting the clean bitumen from the resulting solution in a second stream;
and - optionally, extracting the gas/liquid phase from the resulting solution in a third stream, wherein the resulting clean bitumen contains less than 0.5%w/w of water and less than 300 ppm of fines solids.
BRIEF DESCRIPTION OF THE FIGURES
The present invention may be better understood in consideration of the following description of various embodiments of the invention in connection with the accompanying figures, in which:
FIGURE 1 is a schematic of the process according to a preferred embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
In referring to Figure 1, according to a preferred embodiment of the present invention, the process involves collecting (10) the bitumen froth resulting from bitumen extraction from oilsands, the bitumen froth contains water, fine solids and bitumen. The collected bitumen froth is placed in a high temperature/high pressure autoclave. Water is added if necessary. The collected bitumen froth (20) is then heated at 400 C for a period of time sufficient to change the wettability of the fines contained therein. Once the desired fines wettability is attained, the solution (50) is then filtered at an elevated temperature. The fine solids from the resulting solution are removed in a first stream (60). The clean bitumen from the resulting solution is extracted in a second stream (70). The gas/liquid phase is extracted from the resulting solution in a third stream (80) which undergoes an additional separation step (90) to separate the gas and water phase. It is worth noting that the process for the treatment of bitumen from non-aqueous extraction follows the same flow diagram.

4 The resulting clean bitumen contains less than 0.5%w/w of water and less than 300 ppm of fines solids. The major advantage of the process according to the present invention is to eliminate the need to precipitate a significant fraction of the bitumen (7-8%) by adding paraffinic solvent in order to break the water-in-oil emulsion stabilized by the fine solids, and thus recovery of an additional 7-8% bitumen is achieved.
The initial bitumen froth contained stable water-in-oil emulsion stabilized by fine solids at the oil-water interface. The initial mixture of fines in the froth had very heterogeneous wettability, from oil-wet to water-wet, but after the hydrothermal reaction in a batch reactor at 392 C for 30 mm the fines became more uniformly oil wet. This change in wettability destabilized the emulsion of water in the bitumen, because the fines tended to stay in the oil phase instead of stabilizing the water-oil interface.
The distribution of wettability of the fines was determined by separating the fines from the froth and mixing with toluene and water. For fractionating the fines, 1 g of each unreacted fines and fines reacted with bitumen froth at 392 C for 30 min was placed in Teflon separation funnels with 50 mL water and 50 mL
toluene. Then thorough agitation was applied to the funnels. After that, the toluene layer, aqueous layer, and rag layer/emulsion layer were separated from the funnels. The separated layers were dried and then the fines they contained were analyzed. Depending on their surface properties, the fines either stabilized an emulsion or passed into the oil phase or the water phase. The phases were separated and the mass of fines was measured. The carbon content indicated the wettability high carbon indicates hydrophobic surface and low carbon hydrophilic surface.
Table 1 Separation of fines from bitumen froth by partitioning between toluene and water Samples Weight % of Total Sample Carbon Content, wt% =
Unreacted Fine Solids Total Samples 18.6+0.1 Toluene Layer 25.0 27.6+0.1 Rag Layer/Emulsion 70.0 16.7+2.0 Aqueous Layer 5.0 4.1+0.1 Reacted Fine Solids (392 C for min) Total Sample 15.4+0.3 Toluene Layer 75.0 16.8+0.4 Rag Layer 25.0 14.9+0.4 Aqueous Layer 0 NA

5 Filterability of the fines was significantly increased after the reaction not only because the wettability characteristic of the solids had changed but also the viscosity of the hydrocarbon phase had become lower due to partial upgrading of the bitumen. Filtration was tested using a Buchner funnel with vacuum suction of circa ¨ 85 kPa. Four grams of each of the reacted and unreacted bitumen froth were diluted to 95 mL with toluene. Four grams of Athabasca bitumen was also diluted into 95 mL for reference purposes.
There were three samples in total used in the filterability test. In order to filter the samples, the filter assembly was set up and the vacuum pump was turned on. Then the filter paper was rinsed by toluene. Once minimum pressure was reached, one 95 mL sample was quickly stirred and poured into the glass dam, and the fines that stuck with the beaker were rinsed off by 5 mL of toluene. The total time required for that no visible toluene droplets remained in the glass darn was recorded as filtration time. The filtration time was compared for the three samples. For example, 5 mL of bitumen froth diluted by 95 mL toluene plugged 0.22 1.1.m filtration paper very quickly during filtration, hence it could take an extremely large amount of time to finish and filtration time was essentially infinite. However, the same filtration took about 240 sec after the froth was directly reacted at 392 C for 30 min and diluted by the same amount of toluene. For comparison, Athabasca bitumen (solids-free from paraffinic froth treatment) was diluted and filtered. It only took 40 sec for the solution to pass though the filtration paper. These results suggest that solids-free bitumen can be produced by thermal treatment followed by filtration, without the expense of current froth treatment technologies.
The reaction vessels for the industrial application of the process are preferably high temperature and high pressure autoclaves. The temperatures at which the process can be performed range from about 250 C to over 400 C but preferably are performed at around 390 C.
The description provided as well as the embodiments described therein, is provided by way of illustration of an example, or examples, of particular embodiments of the principles of the present invention.
These examples are provided for the purposes of explanation, and not limitation, of those principles and of the invention.

6

Claims

1. Process for the separation of oil from bitumen froth, said process comprising:
- removal of bitumen froth resulting from bitumen extraction from oilsands, said bitumen froth containing water, fine solids and bitumen;
- heating the bitumen froth for a period of time sufficient to change the wettability of the fines contained therein;
- optionally, adding an aqueous solvent to the bitumen froth;
- filtering the resulting solution at an elevated temperature;
- extracting the fine solids from the resulting solution in a first stream;
- extracting the clean bitumen from the resulting solution in a second stream; and - optionally, extracting the gas/liquid phase from the resulting solution in a third stream.

2. Process according to claim 1 wherein the bitumen froth is heated at a temperature in the range of 300 to 400°C.

3. Process according to claim 1 or 2 wherein the bitumen froth is heated at a temperature in the range of 380 to 400°C.

4. Process according to any one of claims 1 to 3 wherein the bitumen froth is heated at a temperature in the range of 390 to 400°C.

5. Process for the separation of oil from bitumen froth, said process comprising:
- removal of bitumen froth resulting from bitumen extraction from oilsands, said bitumen froth containing water, fine solids and bitumen;
- heating the bitumen froth for a period of time sufficient to change the wettability of the fines contained therein;
- optionally, adding an aqueous solvent to the bitumen froth;
- filtering the resulting solution at an elevated temperature;
- extracting the fine solids from the resulting solution in a first stream;
- extracting the clean bitumen from the resulting solution in a second stream; and - extracting the gas/liquid phase from the resulting solution in a third stream, wherein the resulting clean bitumen contains less than 0.5%w/w of water and less than 300 ppm of fines solids.