CA2188064C - Oil sands tailings treatment process - Google Patents
Oil sands tailings treatment process Download PDFInfo
- Publication number
- CA2188064C CA2188064C CA002188064A CA2188064A CA2188064C CA 2188064 C CA2188064 C CA 2188064C CA 002188064 A CA002188064 A CA 002188064A CA 2188064 A CA2188064 A CA 2188064A CA 2188064 C CA2188064 C CA 2188064C
- Authority
- CA
- Canada
- Prior art keywords
- water
- tailings
- bitumen
- suspension
- coarse
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03B—SEPARATING SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS
- B03B9/00—General arrangement of separating plant, e.g. flow sheets
- B03B9/02—General arrangement of separating plant, e.g. flow sheets specially adapted for oil-sand, oil-chalk, oil-shales, ozokerite, bitumen, or the like
Abstract
Fresh hot tailings, from the hot water extraction process for removing bitumen from oil sand, are treated to remove fine clay solids ("fines") in the suspension. Ca(OH)2 lime is added to the suspension to reduce the stability of the clay-water colloidal structure. Then CO2 is injected to react with excess Ca++ and form water-insoluble CaCO3. The CaCO3 adsorbs fines and sediments them.
Description
3 The present invention relates to treatment of oil sand tailings with the 4 objective of better achieving non-segregated consolidation of the solids in the tailings. More particularly, it relates to better sedimenting the fine clay solid 6 particles in the tailings.
BACKGROUND OF THE INVENTION
~i Two commercial plants, owned respectively by Syncrude Canada Ltd.
1CI and Suncor Inc., are producing over 90 million barrels of synthetic crude 11 annually by surface mining of Athabasca oil sands in Northern Alberta. At 12 both aperations, bitumen is released from the oil sands using the caustic hot 1 a water extraction process. An average sample of surface mineable Athabasca 14 oil sand ore contains 11 per cent weight bitumen (varies up to 18 per cent weight), 5 per cent weight water (varies in the range of 3 to 6 per cent weight), 1Fi 12 percent weight fines (mainly clay and less than 44 microns in size), and 72 17 per cent weight sand.
18 At Syncrude and Suncor, a large quantity of water is used during the 19 production of bitumen. About 20 cubic meters of water is required per cubic 21) meter of bitumen produced, of which 70 per cent is recycled from the surface 21 zone of the tailings pond. In this process, about 0.3 cubic meters of water per 2;2 ton of oil sands feed is withdrawn from the Athabasca River. Syncrude and 23 Suncor have licenses to operate under the Clean Water Act, which stipulates 24 no discharge of process affected water. As a result of this "zero discharge"
policy, waste water containment ponds are formed, and waste water 1 (including drainage and other sources) and tailings are discharged into these 2 ponds.
3 During the extraction of bitumen from the oil sands by a water 4 extraction process, coarse tailings are produced in the form of a slurry.
This slurry comprises about 55 per cent weight solids, of which 82 per cent weight 6 is sand, 17 per cent weight fines, and 1 per cent weight is unrecovered 7 bitumen. This slurry is hydraulically transported and deposited in the tailings 8 ponds. Upon entering the pond, the coarse sand particles segregate quickly 9 and form a beach. The remaining fine tails of 6 to 10 percent weight accumulate in the tailings ponds. Fine tails settle, quickly forming a 11 suspension of 20 percent weight solids content and, over a few years, up to 12 30 percent weight solids (85 percent water by volume). The material has a 13 stable slurry structure and is called mature fine tails. Mature fine tails remain 14 in a fluid state almost indefinitely because of their very slow consolidation rate. It is predicted that if the existing tailings management practice is 16 continued, the accumulated volume of mature fine tails will increase from the 17 current level of 325 million cubic meters to over 1 billion cubic meters by the 18 year 2020. Accumulation of large volumes of mature fine tails with a very 19 stable fluid structure creates environmental concerns and a long-term environmental liability.
{EM 163461. DOC;1 }2 2 The present invention is based on the treatment of tailings, produced 3 from a process involving water extraction of bitumen from oil sand, with 4 calcium hydroxide (Ca(OH)2) lime followed by the injection of carbon dioxide (C02). Both Ca(OH)2 (or CaO, which dissolves in water forming Ca(OH)2) 6 and C02 can be produced from thermal decomposition of limestone (CaC03), 7 on site.
8 Treatment of the coarse tailings with Ca(OH)2 reduces the suspension 9 stability of fines and promotes the non-segregated consolidation of fines present in the coarse tailings. Excess Ca(OH)2 is precipitated in the form of 11 calcium carbonate (CaC03) by the injection of C02. As a result, the freshly 12 formed solid surfaces of CaC03 adsorb fine particles present in the 13 suspension and sediments them with it. C02 injection appears to help 14 floatation of the residual bitumen in the form of a water-in-oil emulsions.
The suspension can be further settled and may be subjected to 16 landfilling.
17 The water in the suspension preferably is reconditioned with soda ash 18 (Na2C03) and recycled to the caustic hot water bitumen extraction process.
19 Reconditioning of the recovered water with Na2C03 appears to reduce the sodium hydroxide (NaOH) consumption during the caustic hot water bitumen 21 extraction process.
22 The treatment of the coarse tailings with Ca(OH)2, injection of C02 and 23 reconditioning of the recovered water with Na2C03 should preferably be 24 conducted at temperatures as high as possible. As a result of the present {EM163461. DOC;1 }3 1 invention's high temperature operating conditions, recycling the recovered 2 water as hot saves considerable amount of energy during the extraction of 3 bitumen from the tar sands.
4 The high temperature operating conditions are desirable to limit the formation of water soluble Ca(HC03)2 from water insoluble CaC03 and C02 6 as well as to reduce the calcium ions (Ca2+) present in the water by reducing 7 the solubility of CaC03. Presence of Ca2+ ions in water have a detrimental 8 effect on the extraction of bitumen from oil sands during the caustic hot water 9 bitumen extraction process.
12 The present invention is based on the principle that for a better 13 management of the oil sands tailings, the settling characteristics of the fine 14 solids (clays) present in the coarse tailings must be improved. It is a known fact that the water soluble asphaltic acids present in bitumen reduce the 16 surface and interfacial tension of water (aqueous media) and act as clay 17 dispersants. These asphaltic acids are partly aromatic in nature and contain 18 oxygen functional groups of phenolic, carboxylic and sulphonic types.
1 g Presence of water soluble asphaltic acids in the tailings promote the clay dispersion. Addition of small quantities of calcium ions (Ca2+) into the 21 coarse tailings reduces the activity of asphaltic acids in the aqueous phase.
22 This results in an increase in surface and interfacial tension of the water (ion 23 exchange between Na+ and Ca2+ forms water insoluble asphaltenic acid 24 salts), which promotes the clay (fines) flocculation. Therefore, addition of {EM163461. DOC;1 }4 1 small quantities of Ca2+ prevents segregation of sands from the fines, which 2 results in non-segregating consolidation of the fines present in the coarse 3 tailings.
4 It must be cautioned that the presence of Ca2+ ions in the process water has an adverse effect on the recovery of bitumen during the caustic hot 6 water extraction process. The present invention for the management of oil 7 sands tailings is based on the treatment of the coarse tailings with slaked lime 8 Ca(OH)2 preferably when it is fresh and hot (at temperatures between 70 and 9 80 °C), followed by C02 injection.
In the present invention when the coarse tailings is treated with slaked 11 Ca(OH)2 lime, surface and interfacial tension of the water increases, resulting 12 in the flocculation of fine particles (clay). A sufficient time (about 10 minutes) 13 and slight mixing conditions should be provided for the treatment of coarse 14 tailings with the slaked lime, in which the chemical reactions between the lime and coarse tailings reaches chemical equilibrium.
16 The mixture is then carried into a sedimentation tank, in which C02 17 gas is injected into the mixture, preferably also at a temperature between 18 and 80 °C. With the injection of C02, the excess amount of Ca2+
present in 19 the aqueous phase is precipitated in the form of CaC03. Subsequently, the newly formed CaC03 surfaces in the aqueous phase absorb ultra-fine 21 particles and sediments them with it. Injection of C02 also reduces the 22 amount of Ca2+ ions in the aqueous phase.
{EM163461. DOC;1 }r'J
1 High-temperature operating conditions are desirable during the 2 injection of CQ2 to prevent the formation of water soluble Ca(HC03)2 from 3 water insoluble CaC03 (the solubility of CaC03 is inversely proportional to 4 temperature). Injection of C02 also floats the residual bitumen which is released during the treatment of the coarse tailings with slaked lime.
6 The solids precipitated at the bottom of the precipitation tank can be 7 disposed to a pond for further consolidation followed by land filling.
8 Water recovered (as hot as possible) in this process is reconditioned 9 by the addition of soda ash (Na2C03) which reduces the consumption of NaOH during the caustic hot water bitumen extraction process.
11 In the present preferred embodiment, the oil sands coarse tailings 12 (produced by the caustic hot water extraction process) are treated when they 13 are already hot. The present invention reduces the formation of mature fine 14 tailings. Fresh and hot coarse tailings of the caustic hot water extraction process can also be blended with the mature fine tailings from the existing 16 tailings ponds. The amount of excess heat available at the plant will 17 determine the amount of mature fine tailings slime taken out from the existing 18 tailings ponds. To save energy, the recovered water will also be treated and 19 recycled, as hot as possible, to the caustic hot water bitumen extraction process.
21 The present invention for the management of the oil sands coarse 22 tailings is based on the following preferred process steps (Figure 2):
23 Step 1. Limestone (CaC03) is decomposed to Ca0 and C02 in a 24 moving bed reactor (furnace) by the following thermal reaction:
{EM 163461. DOC;1 }6 1 CaC03 -> Ca0 + C02 oH1° = 182.90 kJ/mol 2 where the heat required for this reaction is provided from coal (sub-bituminous 3 or high volatile bituminous) combustion:
4 C + 02 -> C02 OHZ° _ - 393.31 kJ/mol If thermal coal with a calorific value of 25 kJ/g is used in the process, 0.073 G tonnes of coal consumption is needed per tonne of limestone decomposed.
8 Step 2_ Ca0 recovered from the limestone furnace will be dissolved in 9 water to form Ca(OH)2 lime:
Ca0 + H20 -> Ca(OH)2 oH3 = - 80.21 kJ/mol 11 Lime is mixed with the oil sands fine tailings slime at about 80 °C.
The 12 solubility of Ca(OH)2 in water at 80 °C is 0.94 g/L and 1.85 g/L at 20 °C (the 13 solubility of Ca0 in water to form Ca(OH)2 decreases with increasing 14 temperature as presented in Figure 3).
16 Step 3. Oil sands coarse tailings slime (discharge of the hot water 17 bitumen extraction process) is treated with Ca(OH)2 lime at temperatures 18 between 70 and 80 °C. At this stage, mature fine tailings slime from the 19 existing tailings ponds can be processed as well, provided that excess heat is available in the plant.
21 When Ca(OH)2 lime is added into the coarse tailings, its pH and the 22 surface tension of the liquid phase increase. The increase in surface tension 23 results from the exchange of Ca2+ ions with Na+ ions of the water soluble {EM 163461. DOC;1 }7 1 asphaltic acids. Therefore, addition of Ca2+ ions reduces the stability of the 2 clay-water colloidal structure and non-segregating consolidation of fines 3 begins. Simultaneously, residual oil (bitumen) in the coarse tailings 4 separates. Non-segregating consolidation of fines takes place in the order of 20 to 90 minutes. High-temperature treatment of the coarse tailings with lime 6 significantly reduces the required time for the non-segregating consolidation 7 of the fines. Preliminary test results showed that less than 0.028 g of Ca2+
8 per gram of fine solids in the coarse tailings provided sufficient consolidation 9 for the fine particles.
11 Step 4~ After sufficient time is allowed for Ca(OH)2 lime to react with the 12 coarse tailings, C02 gas (obtained during Step 1 ) is injected into the mixture.
13 During the injection of C02, the aqueous phase temperature is kept between 14 70 and 80 °C. At this stage of the process, C02 dissolves in the aqueous phase and reacts with the excess Ca2+ ions (Ca(OH)2) to form water 16 insoluble CaC03:
17 Ca(OH)2 + C02 -> CaC03 + H20 oH4" _ -1 U~.Ei~ KJ/mol 18 During the injection of C02, high-temperature operating conditions are 19 desirable to prevent the formation of water soluble Ca(HC03)2 in the aqueous phase:
21 CaC03 + H20 + C02 -> Ca(HCOg)2 22 With the formation of CaC03 in the aqueous phase, a large amount of 23 surface area is created. In this process, fine particles present in the aqueous {EM163461.DOC;1}8 1 phase are adsorbed and then consolidated on the newly created CaC03 2 surfaces. Injection of C02 also improves the quality of water by reducing its 3 Ca2+ content, which is essential for its recycling to the caustic hot water 4 bitumen extraction process.
Injection of C02 also helps the residual bitumen float to the top of the 6 vessel in the form of water-in-oil emulsion. This bitumen-rich stream could be 7 forwarded to the bitumen clean-up operation in the hot water extraction 8 process or de-watered separately.
Step 5. Solids are precipitated (de-watering by settling) in about 20 to 90 11 minutes. The sediment is discharged to a pond for further maturation followed 12 by discharge for land filling.
14 St_ ep 6. Water recovered from the top of the sedimentation vessel is treated with Na2C03 and recycled back to the hot water extraction process.
16 The use of Na2C03 for reconditioning of the recycled water reduces the 17 consumption of NaOH during the caustic hot water extraction process:
18 Ca2+ + Na2C03 -> CaCOg + 2Na+
19 The solubility of CaC03 is inversely proportional with respect to an increase in temperature, therefore treatment of the recovered water with 21 Na2C03 at temperatures between 70 and 80 °C provides an additional 22 advantage for the present invention.
{EM163461.DOC;1 }9 1 Treatment of coarse tailings with Ca(OH)2 lime and precipitation of 2 excess Ca2+ in the form of CaC03 with C02 injection preferably requires the 3 liquid temperature to be maintained between 70 and 80 °C. Therefore, to save 4 energy, the water recovered from the coarse tailings treatment process should be reconditioned with Na2C03 and recycled to the caustic hot water bitumen 6 extraction plant as hot as possible.
7 The invented concept of high temperature (70 to 80 °C) treatment of 8 coarse tailings with Ca(OH)2, water recovery, water reconditioning and water 9 recycling reduces the overall energy consumption associated with the caustic hot water bitumen extraction process. If a 60 °C temperature difference is 11 gained in the recycled water by the present invention, the energy saved will 12 be in the order of 0.67 GJ per barrel of bitumen produced. This corresponds 13 to US $1.50 savings per barrel of bitumen produced.
14 The advantages and capabilities of the present invention are defined as follows:
16 1. The invented process offers a cost effective solution for the management 17 of coarse tailings which is produced during the production of bitumen from 18 oil sands by caustic hot water bitumen extraction process.
19 2. The invented process is simple to use in commercial environments and uses low cost chemicals for the management of oil sands coarse tailings.
21 3. The invented process can smoothly be integrated with the existing caustic 22 hot water bitumen extraction and oil sands tailings management 23 pracesses.
1 4. The invented process for the management of oil sands coarse tailings has 2 the ability to be tailored for the specific needs of existing plants.
3 5. The invented process for the management of oil sands coarse tailings can 4 also be used for the management of other industrial tailings wastes.
6. The invented process requires less than 90 minutes of processing time.
6 7. The invented process treats the fresh, hot coarse tailings and reduces the T formation of mature fine tailings.
f. 8. The invented process allows the treatment of the mature fine tailings from the existing tailings ponds by heating and then blending it with the fresh coarse tailings.
11 9. The invented process discharges the solids for further settling followed by 1 ~! land filling without formation of any mature fine tailings.
1 ~4 10. The invented process recovers the residual oil in the form of water in oil 1~l emulsion.
11.The invented process saves energy ($0.58 of coal or $1.50 of natural gas 1Ei per barrel of bitumen produced) by processing the coarse tailings and 17 recycling the recovered water at temperatures between 70 °C and 80 °C to 18 the caustic hot water bitumen extraction process.
1 ~a 12. The invented process reconditions the recovered water for its use in the 21) caustic hot water bitumen extraction process.
21 13. The invented process improves the quality of the recycled water by 2:2 reconditioning it with soda ash (Na2C03), which reduces sodium hydroxide 2.3 (NaOH) consumption during the caustic hot water bitumen extraction 2~4 process.
1 The present invention saves energy by recovering, reconditioning and 2 recycling the process water as hot as possible. That means that the 3 sedimentation time has to be reduced to a minimum after treating the hot and 4 fresh coarse tailings with Ca(OH)2 upon its discharge from the caustic hot water bitumen extraction process. The present invention was developed 6 based on the experimental data at which the sedimentation process occurred 7 only under gravitational force. The use of cyclones or centrifugal equipment 8. are also possible to accelerate the sedimentation process to reduce the ~i processing time. Short sedimentation time for the treated coarse tailings 1 CI would result in minimum heat losses for the recycled water.
11 This process eliminates the formation of the mature fine tailings by 12 consolidating the fines in the coarse tailings followed by further consolidation 1:3 and land filling. The mature fine tailings in the existing tailings ponds can also 1~E be processed by blending it at certain proportions to the fresh coarse tailings.
1fi In this invention the coarse tailings are processed as hot. The recovered 1 Ei water is reconditioned and recycled to the caustic hot water bitumen 1;~ extraction process as hot, which saves considerable amount of energy for the 1 t3 bitumen extraction process. The coarse tailings management process 1!~ disclosed by this invention can be integrated with the existing caustic hot 2iJ water bitumen extraction plants, as depicted in Figure 1. A slight modification 21 of the process disclosed by this invention can also be used for the 2:2 management of other industrial tailings. This includes the management of 23 industrial wastes such as drilling mud and contaminated soils, rivers, lakes 24 and oceans by petroleum and/or hydrocarbon spills.
1 In the present invention the recycled water quality is improved. For 2 example, its Ca2+ concentration is reduced by operating the treatment process 3 at temperatures as high as possible, injection C02 and treating it with 4 Na2C03.
BACKGROUND OF THE INVENTION
~i Two commercial plants, owned respectively by Syncrude Canada Ltd.
1CI and Suncor Inc., are producing over 90 million barrels of synthetic crude 11 annually by surface mining of Athabasca oil sands in Northern Alberta. At 12 both aperations, bitumen is released from the oil sands using the caustic hot 1 a water extraction process. An average sample of surface mineable Athabasca 14 oil sand ore contains 11 per cent weight bitumen (varies up to 18 per cent weight), 5 per cent weight water (varies in the range of 3 to 6 per cent weight), 1Fi 12 percent weight fines (mainly clay and less than 44 microns in size), and 72 17 per cent weight sand.
18 At Syncrude and Suncor, a large quantity of water is used during the 19 production of bitumen. About 20 cubic meters of water is required per cubic 21) meter of bitumen produced, of which 70 per cent is recycled from the surface 21 zone of the tailings pond. In this process, about 0.3 cubic meters of water per 2;2 ton of oil sands feed is withdrawn from the Athabasca River. Syncrude and 23 Suncor have licenses to operate under the Clean Water Act, which stipulates 24 no discharge of process affected water. As a result of this "zero discharge"
policy, waste water containment ponds are formed, and waste water 1 (including drainage and other sources) and tailings are discharged into these 2 ponds.
3 During the extraction of bitumen from the oil sands by a water 4 extraction process, coarse tailings are produced in the form of a slurry.
This slurry comprises about 55 per cent weight solids, of which 82 per cent weight 6 is sand, 17 per cent weight fines, and 1 per cent weight is unrecovered 7 bitumen. This slurry is hydraulically transported and deposited in the tailings 8 ponds. Upon entering the pond, the coarse sand particles segregate quickly 9 and form a beach. The remaining fine tails of 6 to 10 percent weight accumulate in the tailings ponds. Fine tails settle, quickly forming a 11 suspension of 20 percent weight solids content and, over a few years, up to 12 30 percent weight solids (85 percent water by volume). The material has a 13 stable slurry structure and is called mature fine tails. Mature fine tails remain 14 in a fluid state almost indefinitely because of their very slow consolidation rate. It is predicted that if the existing tailings management practice is 16 continued, the accumulated volume of mature fine tails will increase from the 17 current level of 325 million cubic meters to over 1 billion cubic meters by the 18 year 2020. Accumulation of large volumes of mature fine tails with a very 19 stable fluid structure creates environmental concerns and a long-term environmental liability.
{EM 163461. DOC;1 }2 2 The present invention is based on the treatment of tailings, produced 3 from a process involving water extraction of bitumen from oil sand, with 4 calcium hydroxide (Ca(OH)2) lime followed by the injection of carbon dioxide (C02). Both Ca(OH)2 (or CaO, which dissolves in water forming Ca(OH)2) 6 and C02 can be produced from thermal decomposition of limestone (CaC03), 7 on site.
8 Treatment of the coarse tailings with Ca(OH)2 reduces the suspension 9 stability of fines and promotes the non-segregated consolidation of fines present in the coarse tailings. Excess Ca(OH)2 is precipitated in the form of 11 calcium carbonate (CaC03) by the injection of C02. As a result, the freshly 12 formed solid surfaces of CaC03 adsorb fine particles present in the 13 suspension and sediments them with it. C02 injection appears to help 14 floatation of the residual bitumen in the form of a water-in-oil emulsions.
The suspension can be further settled and may be subjected to 16 landfilling.
17 The water in the suspension preferably is reconditioned with soda ash 18 (Na2C03) and recycled to the caustic hot water bitumen extraction process.
19 Reconditioning of the recovered water with Na2C03 appears to reduce the sodium hydroxide (NaOH) consumption during the caustic hot water bitumen 21 extraction process.
22 The treatment of the coarse tailings with Ca(OH)2, injection of C02 and 23 reconditioning of the recovered water with Na2C03 should preferably be 24 conducted at temperatures as high as possible. As a result of the present {EM163461. DOC;1 }3 1 invention's high temperature operating conditions, recycling the recovered 2 water as hot saves considerable amount of energy during the extraction of 3 bitumen from the tar sands.
4 The high temperature operating conditions are desirable to limit the formation of water soluble Ca(HC03)2 from water insoluble CaC03 and C02 6 as well as to reduce the calcium ions (Ca2+) present in the water by reducing 7 the solubility of CaC03. Presence of Ca2+ ions in water have a detrimental 8 effect on the extraction of bitumen from oil sands during the caustic hot water 9 bitumen extraction process.
12 The present invention is based on the principle that for a better 13 management of the oil sands tailings, the settling characteristics of the fine 14 solids (clays) present in the coarse tailings must be improved. It is a known fact that the water soluble asphaltic acids present in bitumen reduce the 16 surface and interfacial tension of water (aqueous media) and act as clay 17 dispersants. These asphaltic acids are partly aromatic in nature and contain 18 oxygen functional groups of phenolic, carboxylic and sulphonic types.
1 g Presence of water soluble asphaltic acids in the tailings promote the clay dispersion. Addition of small quantities of calcium ions (Ca2+) into the 21 coarse tailings reduces the activity of asphaltic acids in the aqueous phase.
22 This results in an increase in surface and interfacial tension of the water (ion 23 exchange between Na+ and Ca2+ forms water insoluble asphaltenic acid 24 salts), which promotes the clay (fines) flocculation. Therefore, addition of {EM163461. DOC;1 }4 1 small quantities of Ca2+ prevents segregation of sands from the fines, which 2 results in non-segregating consolidation of the fines present in the coarse 3 tailings.
4 It must be cautioned that the presence of Ca2+ ions in the process water has an adverse effect on the recovery of bitumen during the caustic hot 6 water extraction process. The present invention for the management of oil 7 sands tailings is based on the treatment of the coarse tailings with slaked lime 8 Ca(OH)2 preferably when it is fresh and hot (at temperatures between 70 and 9 80 °C), followed by C02 injection.
In the present invention when the coarse tailings is treated with slaked 11 Ca(OH)2 lime, surface and interfacial tension of the water increases, resulting 12 in the flocculation of fine particles (clay). A sufficient time (about 10 minutes) 13 and slight mixing conditions should be provided for the treatment of coarse 14 tailings with the slaked lime, in which the chemical reactions between the lime and coarse tailings reaches chemical equilibrium.
16 The mixture is then carried into a sedimentation tank, in which C02 17 gas is injected into the mixture, preferably also at a temperature between 18 and 80 °C. With the injection of C02, the excess amount of Ca2+
present in 19 the aqueous phase is precipitated in the form of CaC03. Subsequently, the newly formed CaC03 surfaces in the aqueous phase absorb ultra-fine 21 particles and sediments them with it. Injection of C02 also reduces the 22 amount of Ca2+ ions in the aqueous phase.
{EM163461. DOC;1 }r'J
1 High-temperature operating conditions are desirable during the 2 injection of CQ2 to prevent the formation of water soluble Ca(HC03)2 from 3 water insoluble CaC03 (the solubility of CaC03 is inversely proportional to 4 temperature). Injection of C02 also floats the residual bitumen which is released during the treatment of the coarse tailings with slaked lime.
6 The solids precipitated at the bottom of the precipitation tank can be 7 disposed to a pond for further consolidation followed by land filling.
8 Water recovered (as hot as possible) in this process is reconditioned 9 by the addition of soda ash (Na2C03) which reduces the consumption of NaOH during the caustic hot water bitumen extraction process.
11 In the present preferred embodiment, the oil sands coarse tailings 12 (produced by the caustic hot water extraction process) are treated when they 13 are already hot. The present invention reduces the formation of mature fine 14 tailings. Fresh and hot coarse tailings of the caustic hot water extraction process can also be blended with the mature fine tailings from the existing 16 tailings ponds. The amount of excess heat available at the plant will 17 determine the amount of mature fine tailings slime taken out from the existing 18 tailings ponds. To save energy, the recovered water will also be treated and 19 recycled, as hot as possible, to the caustic hot water bitumen extraction process.
21 The present invention for the management of the oil sands coarse 22 tailings is based on the following preferred process steps (Figure 2):
23 Step 1. Limestone (CaC03) is decomposed to Ca0 and C02 in a 24 moving bed reactor (furnace) by the following thermal reaction:
{EM 163461. DOC;1 }6 1 CaC03 -> Ca0 + C02 oH1° = 182.90 kJ/mol 2 where the heat required for this reaction is provided from coal (sub-bituminous 3 or high volatile bituminous) combustion:
4 C + 02 -> C02 OHZ° _ - 393.31 kJ/mol If thermal coal with a calorific value of 25 kJ/g is used in the process, 0.073 G tonnes of coal consumption is needed per tonne of limestone decomposed.
8 Step 2_ Ca0 recovered from the limestone furnace will be dissolved in 9 water to form Ca(OH)2 lime:
Ca0 + H20 -> Ca(OH)2 oH3 = - 80.21 kJ/mol 11 Lime is mixed with the oil sands fine tailings slime at about 80 °C.
The 12 solubility of Ca(OH)2 in water at 80 °C is 0.94 g/L and 1.85 g/L at 20 °C (the 13 solubility of Ca0 in water to form Ca(OH)2 decreases with increasing 14 temperature as presented in Figure 3).
16 Step 3. Oil sands coarse tailings slime (discharge of the hot water 17 bitumen extraction process) is treated with Ca(OH)2 lime at temperatures 18 between 70 and 80 °C. At this stage, mature fine tailings slime from the 19 existing tailings ponds can be processed as well, provided that excess heat is available in the plant.
21 When Ca(OH)2 lime is added into the coarse tailings, its pH and the 22 surface tension of the liquid phase increase. The increase in surface tension 23 results from the exchange of Ca2+ ions with Na+ ions of the water soluble {EM 163461. DOC;1 }7 1 asphaltic acids. Therefore, addition of Ca2+ ions reduces the stability of the 2 clay-water colloidal structure and non-segregating consolidation of fines 3 begins. Simultaneously, residual oil (bitumen) in the coarse tailings 4 separates. Non-segregating consolidation of fines takes place in the order of 20 to 90 minutes. High-temperature treatment of the coarse tailings with lime 6 significantly reduces the required time for the non-segregating consolidation 7 of the fines. Preliminary test results showed that less than 0.028 g of Ca2+
8 per gram of fine solids in the coarse tailings provided sufficient consolidation 9 for the fine particles.
11 Step 4~ After sufficient time is allowed for Ca(OH)2 lime to react with the 12 coarse tailings, C02 gas (obtained during Step 1 ) is injected into the mixture.
13 During the injection of C02, the aqueous phase temperature is kept between 14 70 and 80 °C. At this stage of the process, C02 dissolves in the aqueous phase and reacts with the excess Ca2+ ions (Ca(OH)2) to form water 16 insoluble CaC03:
17 Ca(OH)2 + C02 -> CaC03 + H20 oH4" _ -1 U~.Ei~ KJ/mol 18 During the injection of C02, high-temperature operating conditions are 19 desirable to prevent the formation of water soluble Ca(HC03)2 in the aqueous phase:
21 CaC03 + H20 + C02 -> Ca(HCOg)2 22 With the formation of CaC03 in the aqueous phase, a large amount of 23 surface area is created. In this process, fine particles present in the aqueous {EM163461.DOC;1}8 1 phase are adsorbed and then consolidated on the newly created CaC03 2 surfaces. Injection of C02 also improves the quality of water by reducing its 3 Ca2+ content, which is essential for its recycling to the caustic hot water 4 bitumen extraction process.
Injection of C02 also helps the residual bitumen float to the top of the 6 vessel in the form of water-in-oil emulsion. This bitumen-rich stream could be 7 forwarded to the bitumen clean-up operation in the hot water extraction 8 process or de-watered separately.
Step 5. Solids are precipitated (de-watering by settling) in about 20 to 90 11 minutes. The sediment is discharged to a pond for further maturation followed 12 by discharge for land filling.
14 St_ ep 6. Water recovered from the top of the sedimentation vessel is treated with Na2C03 and recycled back to the hot water extraction process.
16 The use of Na2C03 for reconditioning of the recycled water reduces the 17 consumption of NaOH during the caustic hot water extraction process:
18 Ca2+ + Na2C03 -> CaCOg + 2Na+
19 The solubility of CaC03 is inversely proportional with respect to an increase in temperature, therefore treatment of the recovered water with 21 Na2C03 at temperatures between 70 and 80 °C provides an additional 22 advantage for the present invention.
{EM163461.DOC;1 }9 1 Treatment of coarse tailings with Ca(OH)2 lime and precipitation of 2 excess Ca2+ in the form of CaC03 with C02 injection preferably requires the 3 liquid temperature to be maintained between 70 and 80 °C. Therefore, to save 4 energy, the water recovered from the coarse tailings treatment process should be reconditioned with Na2C03 and recycled to the caustic hot water bitumen 6 extraction plant as hot as possible.
7 The invented concept of high temperature (70 to 80 °C) treatment of 8 coarse tailings with Ca(OH)2, water recovery, water reconditioning and water 9 recycling reduces the overall energy consumption associated with the caustic hot water bitumen extraction process. If a 60 °C temperature difference is 11 gained in the recycled water by the present invention, the energy saved will 12 be in the order of 0.67 GJ per barrel of bitumen produced. This corresponds 13 to US $1.50 savings per barrel of bitumen produced.
14 The advantages and capabilities of the present invention are defined as follows:
16 1. The invented process offers a cost effective solution for the management 17 of coarse tailings which is produced during the production of bitumen from 18 oil sands by caustic hot water bitumen extraction process.
19 2. The invented process is simple to use in commercial environments and uses low cost chemicals for the management of oil sands coarse tailings.
21 3. The invented process can smoothly be integrated with the existing caustic 22 hot water bitumen extraction and oil sands tailings management 23 pracesses.
1 4. The invented process for the management of oil sands coarse tailings has 2 the ability to be tailored for the specific needs of existing plants.
3 5. The invented process for the management of oil sands coarse tailings can 4 also be used for the management of other industrial tailings wastes.
6. The invented process requires less than 90 minutes of processing time.
6 7. The invented process treats the fresh, hot coarse tailings and reduces the T formation of mature fine tailings.
f. 8. The invented process allows the treatment of the mature fine tailings from the existing tailings ponds by heating and then blending it with the fresh coarse tailings.
11 9. The invented process discharges the solids for further settling followed by 1 ~! land filling without formation of any mature fine tailings.
1 ~4 10. The invented process recovers the residual oil in the form of water in oil 1~l emulsion.
11.The invented process saves energy ($0.58 of coal or $1.50 of natural gas 1Ei per barrel of bitumen produced) by processing the coarse tailings and 17 recycling the recovered water at temperatures between 70 °C and 80 °C to 18 the caustic hot water bitumen extraction process.
1 ~a 12. The invented process reconditions the recovered water for its use in the 21) caustic hot water bitumen extraction process.
21 13. The invented process improves the quality of the recycled water by 2:2 reconditioning it with soda ash (Na2C03), which reduces sodium hydroxide 2.3 (NaOH) consumption during the caustic hot water bitumen extraction 2~4 process.
1 The present invention saves energy by recovering, reconditioning and 2 recycling the process water as hot as possible. That means that the 3 sedimentation time has to be reduced to a minimum after treating the hot and 4 fresh coarse tailings with Ca(OH)2 upon its discharge from the caustic hot water bitumen extraction process. The present invention was developed 6 based on the experimental data at which the sedimentation process occurred 7 only under gravitational force. The use of cyclones or centrifugal equipment 8. are also possible to accelerate the sedimentation process to reduce the ~i processing time. Short sedimentation time for the treated coarse tailings 1 CI would result in minimum heat losses for the recycled water.
11 This process eliminates the formation of the mature fine tailings by 12 consolidating the fines in the coarse tailings followed by further consolidation 1:3 and land filling. The mature fine tailings in the existing tailings ponds can also 1~E be processed by blending it at certain proportions to the fresh coarse tailings.
1fi In this invention the coarse tailings are processed as hot. The recovered 1 Ei water is reconditioned and recycled to the caustic hot water bitumen 1;~ extraction process as hot, which saves considerable amount of energy for the 1 t3 bitumen extraction process. The coarse tailings management process 1!~ disclosed by this invention can be integrated with the existing caustic hot 2iJ water bitumen extraction plants, as depicted in Figure 1. A slight modification 21 of the process disclosed by this invention can also be used for the 2:2 management of other industrial tailings. This includes the management of 23 industrial wastes such as drilling mud and contaminated soils, rivers, lakes 24 and oceans by petroleum and/or hydrocarbon spills.
1 In the present invention the recycled water quality is improved. For 2 example, its Ca2+ concentration is reduced by operating the treatment process 3 at temperatures as high as possible, injection C02 and treating it with 4 Na2C03.
Claims (3)
1. A process for removing fine solids from a tailings suspension produced from a process involving water extraction of bitumen from oil sand, comprising:
treating the tailings suspension with calcium hydroxide lime to reduce the suspension stability of the fine solids and promote their consolidation, thereby producing a treated suspension containing excess calcium ions; and injecting carbon dioxide into the treated suspension to react with the calcium ions and produce water-insoluble calcium carbonate which adsorbs fine solids and sediments with them, thereby producing a residual suspension containing treated water.
treating the tailings suspension with calcium hydroxide lime to reduce the suspension stability of the fine solids and promote their consolidation, thereby producing a treated suspension containing excess calcium ions; and injecting carbon dioxide into the treated suspension to react with the calcium ions and produce water-insoluble calcium carbonate which adsorbs fine solids and sediments with them, thereby producing a residual suspension containing treated water.
2. The process as set forth in claim 1 wherein the process is carried out with the suspension at a temperature of about 70 - 80ÀC.
3. The process as set forth in claim 1 or 2 comprising:
adding sodium carbonate to the treated water and recycling the product to the hot water extraction process.
adding sodium carbonate to the treated water and recycling the product to the hot water extraction process.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002188064A CA2188064C (en) | 1996-10-17 | 1996-10-17 | Oil sands tailings treatment process |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002188064A CA2188064C (en) | 1996-10-17 | 1996-10-17 | Oil sands tailings treatment process |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2188064A1 CA2188064A1 (en) | 1998-04-17 |
| CA2188064C true CA2188064C (en) | 2002-02-26 |
Family
ID=4159095
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002188064A Expired - Lifetime CA2188064C (en) | 1996-10-17 | 1996-10-17 | Oil sands tailings treatment process |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2188064C (en) |
Families Citing this family (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8147682B2 (en) | 2006-10-31 | 2012-04-03 | Syncrude Canada Ltd. | Bitumen and thermal recovery from oil sand tailings |
| US7931800B2 (en) | 2007-03-14 | 2011-04-26 | Apex Engineering Inc. | Method for extraction of bitumen from oil sands using lime |
| CA2729457C (en) | 2011-01-27 | 2013-08-06 | Fort Hills Energy L.P. | Process for integration of paraffinic froth treatment hub and a bitumen ore mining and extraction facility |
| CN102676199B (en) * | 2011-02-15 | 2015-08-19 | 顾国兴 | The treatment system of oil sand tailing or oil sand slurries and method |
| CA2906715C (en) | 2011-02-25 | 2016-07-26 | Fort Hills Energy L.P. | Process for treating high paraffin diluted bitumen |
| CA2865126C (en) | 2011-03-04 | 2015-12-22 | Fort Hills Energy L.P. | Process for solvent addition to high viscosity bitumen froth |
| CA2735311C (en) | 2011-03-22 | 2013-09-24 | Fort Hills Energy L.P. | Process for direct steam injection heating of oil sands bitumen froth |
| CA2737410C (en) | 2011-04-15 | 2013-10-15 | Fort Hills Energy L.P. | Heat recovery for bitumen froth treatment plant integration with sealed closed-loop cooling circuit |
| CA2740935C (en) | 2011-05-18 | 2013-12-31 | Fort Hills Energy L.P. | Enhanced temperature control of bitumen froth treatment process |
| US9676638B2 (en) | 2012-06-15 | 2017-06-13 | 650438 Alberta Ltd. | Method and system for separation of suspensions |
| US10647606B2 (en) | 2017-08-18 | 2020-05-12 | Graymont Western Canada Inc. | Treatment of oil sands tailings with lime at elevated pH levels |
| WO2019094620A2 (en) | 2017-11-08 | 2019-05-16 | Graymont Western Canada Inc. | Treatment of tailings streams with one or more dosages of lime, and associated systems and methods |
| US10894730B2 (en) | 2018-09-11 | 2021-01-19 | Graymont (Pa) Inc. | Geotechnical characteristics of tailings via lime addition |
-
1996
- 1996-10-17 CA CA002188064A patent/CA2188064C/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| CA2188064A1 (en) | 1998-04-17 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA2522031C (en) | Method for treatment of oil sands tailings with lime or with lime and carbon dioxide | |
| CA2188064C (en) | Oil sands tailings treatment process | |
| US5985138A (en) | Tar sands extraction process | |
| US4495056A (en) | Oil shale retorting and retort water purification process | |
| US5626743A (en) | Tar sands extraction process | |
| US7638057B2 (en) | Method of treating water using petroleum coke | |
| US7628204B2 (en) | Wastewater disposal with in situ steam production | |
| US6251290B1 (en) | Method for recovering hydrocarbons from tar sands and oil shales | |
| US20100147742A1 (en) | Method for improving bitumen recovery from oil sands by production of surfactants from bitumen asphal tenes | |
| EA003978B1 (en) | Separation of tars, oils and inorganic constituents from oil bearing sands or shales | |
| US3751358A (en) | Freeze-thaw separation of solids from tar sands extraction effluents | |
| US3931006A (en) | Method of reducing sludge accumulation from tar sands hot water process | |
| CA2168808C (en) | Tar sands extraction process | |
| US9315734B2 (en) | System and method for minimizing the negative environmental impact of the oilsands industry | |
| US20150122732A1 (en) | METHOD OF TREATING WATER USING PETROLEUM COKE AND A pH-LOWERING AGENT | |
| US20020104799A1 (en) | Tar sands extraction process | |
| CA2758608C (en) | Methods for separation of bitumen from oil sands | |
| US3953318A (en) | Method of reducing sludge accumulation from tar sands hot water process | |
| CA1063957A (en) | Method for reducing mineral content of sludge | |
| CA2304972A1 (en) | A process for low temperature separation and isolation of crude heavy oil | |
| CA2665747A1 (en) | Usage of oil facilities waste sludge and fine tailings water for generation of hot water and steam for bitumen production | |
| CA2607353C (en) | Method of treating water using petroleum coke | |
| US20110192768A1 (en) | Method for extraction of bitumen from oil sands using lime | |
| Arnipally et al. | Reduction of Environmental Impacts of Oil Sands Plants by Implementing Bitumen Extraction and Tailings Disposal Processes using Lime (CaO) Additive | |
| US3556981A (en) | Separation of bitumen from bituminous sand using a dense slurry and controlled velocities |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKEX | Expiry |
Effective date: 20161017 |