CA2091502C - Process to separate a mixture of water, solids or sludges, non-volatile hydrocarbons and other accompanying substances - Google Patents
Process to separate a mixture of water, solids or sludges, non-volatile hydrocarbons and other accompanying substancesInfo
- Publication number
- CA2091502C CA2091502C CA 2091502 CA2091502A CA2091502C CA 2091502 C CA2091502 C CA 2091502C CA 2091502 CA2091502 CA 2091502 CA 2091502 A CA2091502 A CA 2091502A CA 2091502 C CA2091502 C CA 2091502C
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- solvent
- solids
- water
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- phase
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- 239000007787 solid Substances 0.000 title claims abstract description 45
- 238000000034 method Methods 0.000 title claims abstract description 42
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 title claims abstract description 35
- 239000000203 mixture Substances 0.000 title claims abstract description 33
- 229930195733 hydrocarbon Natural products 0.000 title claims abstract description 31
- 150000002430 hydrocarbons Chemical class 0.000 title claims abstract description 31
- 239000000126 substance Substances 0.000 title abstract description 5
- 239000002689 soil Substances 0.000 claims abstract description 15
- 238000000638 solvent extraction Methods 0.000 claims abstract description 8
- 239000002904 solvent Substances 0.000 claims description 98
- 238000004062 sedimentation Methods 0.000 claims description 16
- 239000013049 sediment Substances 0.000 claims description 12
- 238000000926 separation method Methods 0.000 claims description 12
- 238000011084 recovery Methods 0.000 claims description 11
- UHOVQNZJYSORNB-UHFFFAOYSA-N Benzene Chemical compound C1=CC=CC=C1 UHOVQNZJYSORNB-UHFFFAOYSA-N 0.000 claims description 8
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 claims description 6
- 239000012535 impurity Substances 0.000 claims description 5
- 238000007865 diluting Methods 0.000 claims description 4
- 239000000945 filler Substances 0.000 claims description 4
- 239000013557 residual solvent Substances 0.000 claims description 4
- 230000000717 retained effect Effects 0.000 claims description 4
- 239000004215 Carbon black (E152) Substances 0.000 claims description 3
- 230000018044 dehydration Effects 0.000 claims description 2
- 238000006297 dehydration reaction Methods 0.000 claims description 2
- 229920000831 ionic polymer Polymers 0.000 claims description 2
- 239000003208 petroleum Substances 0.000 claims description 2
- 239000012071 phase Substances 0.000 claims 11
- 239000007791 liquid phase Substances 0.000 claims 2
- 239000010802 sludge Substances 0.000 abstract description 15
- 239000010426 asphalt Substances 0.000 abstract description 14
- 239000003921 oil Substances 0.000 abstract description 10
- 238000004519 manufacturing process Methods 0.000 abstract description 7
- 239000010779 crude oil Substances 0.000 abstract description 3
- 239000000470 constituent Substances 0.000 abstract description 2
- 238000000605 extraction Methods 0.000 description 10
- 239000004576 sand Substances 0.000 description 7
- 239000002245 particle Substances 0.000 description 5
- 239000000047 product Substances 0.000 description 4
- 238000001704 evaporation Methods 0.000 description 3
- 230000008020 evaporation Effects 0.000 description 3
- 239000006200 vaporizer Substances 0.000 description 3
- 239000002699 waste material Substances 0.000 description 3
- 150000001875 compounds Chemical class 0.000 description 2
- 238000009833 condensation Methods 0.000 description 2
- 230000005494 condensation Effects 0.000 description 2
- 238000005202 decontamination Methods 0.000 description 2
- 230000003588 decontaminative effect Effects 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 231100000252 nontoxic Toxicity 0.000 description 2
- 230000003000 nontoxic effect Effects 0.000 description 2
- 238000005067 remediation Methods 0.000 description 2
- 239000013543 active substance Substances 0.000 description 1
- 125000003118 aryl group Chemical group 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 239000000839 emulsion Substances 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 238000007667 floating Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 229910052736 halogen Inorganic materials 0.000 description 1
- 150000002367 halogens Chemical class 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000009996 mechanical pre-treatment Methods 0.000 description 1
- 238000005065 mining Methods 0.000 description 1
- 239000010812 mixed waste Substances 0.000 description 1
- 239000008239 natural water Substances 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 230000001376 precipitating effect Effects 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 239000011343 solid material Substances 0.000 description 1
- 238000000935 solvent evaporation Methods 0.000 description 1
- 238000010025 steaming Methods 0.000 description 1
- 239000000725 suspension Substances 0.000 description 1
- 241001478887 unidentified soil bacteria Species 0.000 description 1
- 230000008016 vaporization Effects 0.000 description 1
- 230000035899 viability Effects 0.000 description 1
- 238000010792 warming Methods 0.000 description 1
- 239000002351 wastewater Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G1/00—Production of liquid hydrocarbon mixtures from oil-shale, oil-sand, or non-melting solid carbonaceous or similar materials, e.g. wood, coal
- C10G1/04—Production of liquid hydrocarbon mixtures from oil-shale, oil-sand, or non-melting solid carbonaceous or similar materials, e.g. wood, coal by extraction
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G53/00—Treatment of hydrocarbon oils, in the absence of hydrogen, by two or more refining processes
- C10G53/02—Treatment of hydrocarbon oils, in the absence of hydrogen, by two or more refining processes plural serial stages only
- C10G53/04—Treatment of hydrocarbon oils, in the absence of hydrogen, by two or more refining processes plural serial stages only including at least one extraction step
Landscapes
- Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Life Sciences & Earth Sciences (AREA)
- Wood Science & Technology (AREA)
- Treatment Of Sludge (AREA)
- Extraction Or Liquid Replacement (AREA)
Abstract
A process separates a mixture of water, solids or sludges, non-volatile hydrocarbons, and other accompanying substances by means of solvent extraction. Mixtures that consist primarily of solids or sludge with non-volatile hydrocarbons are especially suited for application of this process, if they occur as a concentrated sludge from a settling pond of bitumen production from tar sands.
However, it is also possible to use the process to decontaminate soil contaminated by crude oil spillage. The process makes it possible to process, and to break down to its primary constituents, the oil-bearing sludge that has accumulated during the production of bitumen from tar sands using the hot water method, and which is stored in settling ponds and constitutes a permanent danger to the environment. The recycled water is then free of hydrocarbons. This environmentally compatible process can be carried out with low energy and operation costs.
However, it is also possible to use the process to decontaminate soil contaminated by crude oil spillage. The process makes it possible to process, and to break down to its primary constituents, the oil-bearing sludge that has accumulated during the production of bitumen from tar sands using the hot water method, and which is stored in settling ponds and constitutes a permanent danger to the environment. The recycled water is then free of hydrocarbons. This environmentally compatible process can be carried out with low energy and operation costs.
Description
2 ~ 5 1~1 ~
Process to Separate a Mixture of Water, Solids or Sludges, Non-volatile Hydrocarbons and Other Accompanying Substances The invention relates to a process for the separation of a mixture of water, solids or sludges, non-volatile hydrocarbons and other accompanying substances by means of solvent extraction.
Mixtures that consist primarily of solids or sludges with non-volatile hydrocarbons are particularly suited for the application of a process in accordance with the invention, if they occur as a concentrated sludge from the settling ponds of bitumen production from tar sands. However, it is also possible to use the process to decontaminate contaminated soil after a crude oil spillage.
DE-OS 29 21 654 describes a contact process for treating mixed waste materials that contain oil and/or oil byproducts, polluted water and solid sludge. The oil components are extracted by means of a solvent from the waste material in a continuous multiple-chamber contact device in which the waste material and a solvent move in separate phases and are brought into contact with one another by means of containers rotating in the contact device.
The solids are separated solely on the basis of the effect of gravitational forces, by which means it is not possible to achieve a sufficient separation of the non-volatile hydrocarbons and the solid particles.
An object of the present invention is to develop a process that can separate mixtures of water, solids or sludge, non-volatile hydrocarbons and other impurities into their principal components by means of solvent extraction, while avoiding the disadvantages of the process mentioned above. However, the process should also be applicable to the decontamination of contaminated soils after crude oil spillage.
To this end, according to one aspect of the invention, there is provided a process for separating a mixture of water, solids or sludges, non-volatile hydrocarbons and other impurities by means of solvent extraction, comprising: (a) preheating the mixture and diluting it with water and a solvent, and then mechanically separating and dehydrating the mixture to split it into (i) a water-and-solvent-rich phase in which the non-volatile hydrocarbons are released, and (ii) a solid-rich phase in which some solvent is still retained; (b) subjecting phase (i) to multiple stage solvent recovery to evaporate out the solvent and returning such solvent to step (a), skimming the non-volatile hydrocarbons and removing skimmed water; (c) subjecting phase (ii) to solvent stripping to separate the solvent from the solids and feeding such separated solvent to phase (i) in step (b); and (d) employing the separated solids as filler or as decontaminated soil.
According to another aspect of the invention, there is provided a process for separating a mixture of water, solids or sludges, non-volatile hydrocarbons and other impurities by means of solvent extraction, comprising: (a) diluting the mixture with water and a solvent, and then mechanically separating and dehydrating the mixture to split it into (i) a water-and-solvent-rich phase in which the non-volatile hydrocarbons are released, and (ii) a solid-rich phase in which some solvent is still retained; (b) subjecting phase (i) to multiple stage solvent recovery to evaporate out the solvent and returning such solvent to step (a), skimming the non-volatile hydrocarbons and removing skimmed water; (c) subjecting phase (ii) to solvent stripping to separate the solvent from the solids and feeding such separated solvent to phase (i) in step (b); and (d) employing the separated solids as filler or as decontaminated soil.
' ~
2a The process in accordance with the invention makes it possible to process, and break down to its primary constituents, the oil-bearing sludge which accumulates during the production of bitumen from tar sands using the hot water process, which sludge is stored in settling ponds and constitutes a permanent danger to the environment. The recycled water is then free of hydrocarbons. This environmentally friendly process can be carried out at low energy and operating costs.
Another characteristic of this invention is that an organic CFC-free solvent is used as the solvent. An example is petroleum benzin. Many other solvents containing hydrocarbons are equally suitable for extraction. The application depends, in part, on the type of hydrocarbon to be dissolved. If the bitumen or other hard to refine hydrocarbons contain aromatic or polar compounds, then similar solvents, such as toluene or benzene, are recommended. The suitability limits of the solvent are set by the solvent recovery with a sufficiently large difference in boiling point between the solvent and the substance dissolved, ~' its availability on site, the production price, environmental compatibility, and compatibility with the subsequent stages of production. In addition to the environmental reasons, solvents containing CFC must also be ruled out because of halogen traces in bitumen processing, which are harmful to the catalyst.
An excellent characteristic of preferred features of the invention is that, within the mechanical separation stage to which the extraction mixture is fed and which is composed of a single or multiple stage hydrocyclone cascade and/or a single or multiple spiral centrifuge the overflow of the hydrocyclone is fed into a sedimentation device and the lower flow of the first hydrocyclone stage is passed to the following hydrocyclone stage as the feed. The lower flow of the final hydrocyclone stage is the feed of the first spiral centrifuge stage and the sediment of the first centrifuge is passed to the following centrifuge stage as the feed, while the sediment of the final centrifuge stage is sent to the solvent stripping stage. After mechanical separation of the solvent, the sediment of the sedimentation apparatus arrives at the solvent stripping. The overflow of the first station of the sedimentation apparatus is sent to another station of the sedimentation apparatus along with the centrifuged product of the spiral centrifuge. The operation of the process within the mechanical separation stage ensures favourable splitting of the mixture. The recycled water is free of hydrocarbons and high yields of non-volatile hydrocarbons can be achieved. The remaining solid material is ecologically harmless and the solvent used can be repeatedly returned to the circular process.
Operation of the process still incurs only minor energy and operating costs.
In another feature of the process, 1 to 30 mg/L of ionic polymer is added to the mixture before or after the first hydrocyclone stage and/or before or after the first spiral centrifuge stage.
This can advantageously raise the speed of separation until the equipotential point of solution is reached. The right dosage point depends on the solid content of the mixture and the pressure losses set in the hydrocyclones.
A particularly advantageous characteristic of the invention is that the process can be carried out as a cold process, without warming the mixture, if the hydrocarbons are easy to extract. It is thus possible to save on the heat exchangers required to heat the mixture.
The invention will be explained in greater detail below with the help of the following examples and the accompanying drawing in which Figure l is a schematic diagram illustrating the course of the process of oil sludge treatment by means of solvent extraction.
In Figure 1, after having been heated in a heating station 1, the mixture G to be separated is fed into an extraction reactor 2, which is in the form of an agitating pan. The heating station 1 is operated by steam D and/or a warm waste water stream W
available from bitumen refining, for example. The type of extraction reactor 2 depends on the properties of the mixture.
One option is a reactor with a free stream capture floor, through which the regenerated solvent enters. The mixture is fed into the lower section of the extraction reactor 2 and mixed thoroughly with the solvent Lm. During extraction, the oil captured between the solid particles and enveloping the solid particles is floated by differences in consistency and released gases and/or is dissolved in the solvent. The mixture of solvent and sludge contains tiny emulsified and suspended particles which cannot be separated by gravitational forces in a sedimentation apparatus due to the presence of surface-active substances, because relatively stable emulsions and suspensions are created during the extraction.
~ ~ ~ f~
The splitting of this mixture is accomplished by a subsequently carried out mechanical separation stage 5. This stage consists of a single or multistage hydrocyclonic cascade 5H1 to 5Hn and/or a single or multistage spiral centrifuge 5S1 to 5Sn. Between the hydrocyclonic stages 5H1 to 5Hn and the centrifugal stages 5S1 to 5Sn, a poly-electrolyte 3 can be fed in for improved solids precipitation. In the mechanical separation stage 5, the extraction mixture, composed of solvent Lm with dissolved non-volatile hydrocarbons, water and sand, is separated in the hydrocyclone 5H1 to 5Hn into two phases, namely a water-and-solvent-rich phase (i), and a solid-rich phase (ii). The overflow u of this hydrocyclone, namely phase (i), contains mainly solvent, sand fragments and water, with most of the sand consisting of fine grains. Because of the high proportion of solvent, the sand settles out of the cyclone overflow so well that it can be separated in a simple sedimentation apparatus 5A1.
The sediment S from the sedimentation apparatus 5A1 ends up in a residual solvent stripping device 6 (after the mechanical separation of the solvent). The overflow of this sedimentation apparatus 5A1 is unclouded by solid particles and flows together with the centrifuged product Z from the spiral centrifuge 5S1 into another sedimentation apparatus 5A2, which can be preceded by a polymer dosage 3. The centrifuged product from centrifuge 5Sn contains largely water and only small quantities of solvent and fine sand. The sand settles under the influence of the solvent from the first sedimentation apparatus 5A1, so that its overflow to the second sedimentation apparatus 5A2 contains solvent, dissolved and floating bitumen, and water. The lower flow u from the first hydrocyclone stage 5H1 is the feed for the following cyclone stage. The lower flow U of the last cyclone stage 5Hn runs into the first stage of the spiral centrifuge 5S
and contains mainly water and sand. The sediment S from the first centrifuge 5S1 is passed into the subsequent centrifuge stage or stages as feed. Precipitating agent dosing devices can be installed between and/or within the single centrifuge.
A
$ ~ ~
The sediment S from the last centrifuge 5Sn constitutes phase (ii) and is fed into the residual solvent stripping device 6.
Here, the solvent adsorbed to the solids is stripped by steam D
in the stripping device 6. The quantity of stripping steam must make possible a high rate of solvent recovery and still provide enough energy, after the stripping, to run the first solvent steaming stage. Since the hydrocarbon-bearing solvents used have a very high vapour tension and evaporate without a residue, the solvent wastage is slight. Selection of the type of dryer, which is embodied in the stripping device 6, depends upon the degree of dehydration desired. Stage dryers with distribution devices or revolving drum dryers are examples of appropriate dryer types.
With respect to the required stripping steam, contact surface, steam decanter sediment and retention time, the solvent separation must be set up so that the solvent recovery rates are in excess of 99%, in order to achieve an economic operation of the system. The solvent recovery, or loss rate, is defined here as being such that less than 1% of the solvent stream used in the reaction extractor is removed via waste air, decanter sediment and water, or that over 99% of the solvent used is regenerated.
The stripped decanter centrifuge sediment FA is semi-solid or a pumpable stream of water containing high quantities of solids.
Semi-solid discharge can be used as fill on mining sites for re-cultivation of the excavated pits. The sedimented sludge is ecologically harmless, free of bitumen and biologically nontoxic.
The overflow from these ponds can be used in the production process or returned to the natural water cycle.
The multistage solvent recovery apparatus 4 consists of a multistage evaporator (not shown) whose stages vaporize solvents at various pressures. The condensation heat of the solvent vapour is used as vaporizing heat for each following evaporation stage, so that the heat employed is used in the form of stripping steam for each stage and thereby contributes to saving energy in the most energy-intensive step of the process. The solvent A
$ ~ ~.
vapour from the final stage releases its condensation heat to warm the water-solvent stream from the second sedimentation basin, or is used to heat the sludge used in the system intake.
As in all multistage concentrators, the number of evaporation stages is arrived at through calculation of economic viability, in which capital investment costs are offset against the savings of energy over the write-off period. For optimal use of energy and to ensure constantly operating temperature differences, the solvent-water stream from the hydrocyclonic overflows, and the centrifuged product from the spiral centrifuge are fed into the multistage vaporizer flowing counter to the heat carrier (already evaporated solvent). In this process, the solvent Lm evaporates out of the solvent-water stream and the remaining bitumen is concentrated on the surface of the liquid. This bitumen B is skimmed off in the skimmer 7 and is available for further processing in the bitumen processing process. The skimmer 7 need not be integrated in the vaporizer 4. For construction reasons, the skimmer 4 can also be installed outside the vaporizer, which makes particular sense if low levels of bitumen do not obstruct solvent evaporation by solid formation of bitumen film. Solvent recovery can also be carried out in multistage vaporizers, in which the heat carrier flows in parallel with the solvent to be concentrated. The skimmed water W is largely free of solids and can be used to heat the sludge being fed in. All installations and equipment in the process are constructed with an enclosed form so as to have no contact with the surrounding air, in order to avoid solvent loss through evaporation and offensive odours.
The solvent losses occur as a result of residual solubilities of the solvent, which is itself insoluble, in the skimmed-off water, and by removal of solvent in the solids discharge in the dryer.
The small quantities of solvent in the water are quickly broken down biologically. The solvent residues in the sand are broken down by soil bacteria as well, as they constitute a non-toxic biologically degradable compound.
Example 2 The process can also be used to decontaminate soils contaminated by oil. This process differs only in certain details from the above-described processing of sludge. There are differences related to the mechanical pre-treatment, which depend on the type of soil to be decontaminated.
Another distinguishing characteristic can be the size of the system. While typical throughputs in sludge treatment run at about 1000 cubic metres per hour, soil remediation systems are projected for throughputs of 1 to lOOm3/h. These systems must be transportable to a variety of cleanup sites in a relatively short period of time and are therefore constructed for mobile deployment (small soil remediation systems are constructed to fit in containers).
However, there are also applications in which considerably larger systems for soil decontamination would appear to be useful (e.g.
clearing up war damage or natural catastrophes).
The soil to be treated is fed into the extraction reactor, which for cost reasons is generally not a tubular reactor but rather a continuous agitator vessel or a cascade consisting of a series of agitator vessels.
In the reactor, the soil is washed with solvent, during which process the oil is transferred into the solvent or partially floats in the reactor.
The extraction reactor is followed by the above-described separation of soils, solvents and oil by mechanical decanting, solvent recovery and stripping out of the residual solvent by steam.
Process to Separate a Mixture of Water, Solids or Sludges, Non-volatile Hydrocarbons and Other Accompanying Substances The invention relates to a process for the separation of a mixture of water, solids or sludges, non-volatile hydrocarbons and other accompanying substances by means of solvent extraction.
Mixtures that consist primarily of solids or sludges with non-volatile hydrocarbons are particularly suited for the application of a process in accordance with the invention, if they occur as a concentrated sludge from the settling ponds of bitumen production from tar sands. However, it is also possible to use the process to decontaminate contaminated soil after a crude oil spillage.
DE-OS 29 21 654 describes a contact process for treating mixed waste materials that contain oil and/or oil byproducts, polluted water and solid sludge. The oil components are extracted by means of a solvent from the waste material in a continuous multiple-chamber contact device in which the waste material and a solvent move in separate phases and are brought into contact with one another by means of containers rotating in the contact device.
The solids are separated solely on the basis of the effect of gravitational forces, by which means it is not possible to achieve a sufficient separation of the non-volatile hydrocarbons and the solid particles.
An object of the present invention is to develop a process that can separate mixtures of water, solids or sludge, non-volatile hydrocarbons and other impurities into their principal components by means of solvent extraction, while avoiding the disadvantages of the process mentioned above. However, the process should also be applicable to the decontamination of contaminated soils after crude oil spillage.
To this end, according to one aspect of the invention, there is provided a process for separating a mixture of water, solids or sludges, non-volatile hydrocarbons and other impurities by means of solvent extraction, comprising: (a) preheating the mixture and diluting it with water and a solvent, and then mechanically separating and dehydrating the mixture to split it into (i) a water-and-solvent-rich phase in which the non-volatile hydrocarbons are released, and (ii) a solid-rich phase in which some solvent is still retained; (b) subjecting phase (i) to multiple stage solvent recovery to evaporate out the solvent and returning such solvent to step (a), skimming the non-volatile hydrocarbons and removing skimmed water; (c) subjecting phase (ii) to solvent stripping to separate the solvent from the solids and feeding such separated solvent to phase (i) in step (b); and (d) employing the separated solids as filler or as decontaminated soil.
According to another aspect of the invention, there is provided a process for separating a mixture of water, solids or sludges, non-volatile hydrocarbons and other impurities by means of solvent extraction, comprising: (a) diluting the mixture with water and a solvent, and then mechanically separating and dehydrating the mixture to split it into (i) a water-and-solvent-rich phase in which the non-volatile hydrocarbons are released, and (ii) a solid-rich phase in which some solvent is still retained; (b) subjecting phase (i) to multiple stage solvent recovery to evaporate out the solvent and returning such solvent to step (a), skimming the non-volatile hydrocarbons and removing skimmed water; (c) subjecting phase (ii) to solvent stripping to separate the solvent from the solids and feeding such separated solvent to phase (i) in step (b); and (d) employing the separated solids as filler or as decontaminated soil.
' ~
2a The process in accordance with the invention makes it possible to process, and break down to its primary constituents, the oil-bearing sludge which accumulates during the production of bitumen from tar sands using the hot water process, which sludge is stored in settling ponds and constitutes a permanent danger to the environment. The recycled water is then free of hydrocarbons. This environmentally friendly process can be carried out at low energy and operating costs.
Another characteristic of this invention is that an organic CFC-free solvent is used as the solvent. An example is petroleum benzin. Many other solvents containing hydrocarbons are equally suitable for extraction. The application depends, in part, on the type of hydrocarbon to be dissolved. If the bitumen or other hard to refine hydrocarbons contain aromatic or polar compounds, then similar solvents, such as toluene or benzene, are recommended. The suitability limits of the solvent are set by the solvent recovery with a sufficiently large difference in boiling point between the solvent and the substance dissolved, ~' its availability on site, the production price, environmental compatibility, and compatibility with the subsequent stages of production. In addition to the environmental reasons, solvents containing CFC must also be ruled out because of halogen traces in bitumen processing, which are harmful to the catalyst.
An excellent characteristic of preferred features of the invention is that, within the mechanical separation stage to which the extraction mixture is fed and which is composed of a single or multiple stage hydrocyclone cascade and/or a single or multiple spiral centrifuge the overflow of the hydrocyclone is fed into a sedimentation device and the lower flow of the first hydrocyclone stage is passed to the following hydrocyclone stage as the feed. The lower flow of the final hydrocyclone stage is the feed of the first spiral centrifuge stage and the sediment of the first centrifuge is passed to the following centrifuge stage as the feed, while the sediment of the final centrifuge stage is sent to the solvent stripping stage. After mechanical separation of the solvent, the sediment of the sedimentation apparatus arrives at the solvent stripping. The overflow of the first station of the sedimentation apparatus is sent to another station of the sedimentation apparatus along with the centrifuged product of the spiral centrifuge. The operation of the process within the mechanical separation stage ensures favourable splitting of the mixture. The recycled water is free of hydrocarbons and high yields of non-volatile hydrocarbons can be achieved. The remaining solid material is ecologically harmless and the solvent used can be repeatedly returned to the circular process.
Operation of the process still incurs only minor energy and operating costs.
In another feature of the process, 1 to 30 mg/L of ionic polymer is added to the mixture before or after the first hydrocyclone stage and/or before or after the first spiral centrifuge stage.
This can advantageously raise the speed of separation until the equipotential point of solution is reached. The right dosage point depends on the solid content of the mixture and the pressure losses set in the hydrocyclones.
A particularly advantageous characteristic of the invention is that the process can be carried out as a cold process, without warming the mixture, if the hydrocarbons are easy to extract. It is thus possible to save on the heat exchangers required to heat the mixture.
The invention will be explained in greater detail below with the help of the following examples and the accompanying drawing in which Figure l is a schematic diagram illustrating the course of the process of oil sludge treatment by means of solvent extraction.
In Figure 1, after having been heated in a heating station 1, the mixture G to be separated is fed into an extraction reactor 2, which is in the form of an agitating pan. The heating station 1 is operated by steam D and/or a warm waste water stream W
available from bitumen refining, for example. The type of extraction reactor 2 depends on the properties of the mixture.
One option is a reactor with a free stream capture floor, through which the regenerated solvent enters. The mixture is fed into the lower section of the extraction reactor 2 and mixed thoroughly with the solvent Lm. During extraction, the oil captured between the solid particles and enveloping the solid particles is floated by differences in consistency and released gases and/or is dissolved in the solvent. The mixture of solvent and sludge contains tiny emulsified and suspended particles which cannot be separated by gravitational forces in a sedimentation apparatus due to the presence of surface-active substances, because relatively stable emulsions and suspensions are created during the extraction.
~ ~ ~ f~
The splitting of this mixture is accomplished by a subsequently carried out mechanical separation stage 5. This stage consists of a single or multistage hydrocyclonic cascade 5H1 to 5Hn and/or a single or multistage spiral centrifuge 5S1 to 5Sn. Between the hydrocyclonic stages 5H1 to 5Hn and the centrifugal stages 5S1 to 5Sn, a poly-electrolyte 3 can be fed in for improved solids precipitation. In the mechanical separation stage 5, the extraction mixture, composed of solvent Lm with dissolved non-volatile hydrocarbons, water and sand, is separated in the hydrocyclone 5H1 to 5Hn into two phases, namely a water-and-solvent-rich phase (i), and a solid-rich phase (ii). The overflow u of this hydrocyclone, namely phase (i), contains mainly solvent, sand fragments and water, with most of the sand consisting of fine grains. Because of the high proportion of solvent, the sand settles out of the cyclone overflow so well that it can be separated in a simple sedimentation apparatus 5A1.
The sediment S from the sedimentation apparatus 5A1 ends up in a residual solvent stripping device 6 (after the mechanical separation of the solvent). The overflow of this sedimentation apparatus 5A1 is unclouded by solid particles and flows together with the centrifuged product Z from the spiral centrifuge 5S1 into another sedimentation apparatus 5A2, which can be preceded by a polymer dosage 3. The centrifuged product from centrifuge 5Sn contains largely water and only small quantities of solvent and fine sand. The sand settles under the influence of the solvent from the first sedimentation apparatus 5A1, so that its overflow to the second sedimentation apparatus 5A2 contains solvent, dissolved and floating bitumen, and water. The lower flow u from the first hydrocyclone stage 5H1 is the feed for the following cyclone stage. The lower flow U of the last cyclone stage 5Hn runs into the first stage of the spiral centrifuge 5S
and contains mainly water and sand. The sediment S from the first centrifuge 5S1 is passed into the subsequent centrifuge stage or stages as feed. Precipitating agent dosing devices can be installed between and/or within the single centrifuge.
A
$ ~ ~
The sediment S from the last centrifuge 5Sn constitutes phase (ii) and is fed into the residual solvent stripping device 6.
Here, the solvent adsorbed to the solids is stripped by steam D
in the stripping device 6. The quantity of stripping steam must make possible a high rate of solvent recovery and still provide enough energy, after the stripping, to run the first solvent steaming stage. Since the hydrocarbon-bearing solvents used have a very high vapour tension and evaporate without a residue, the solvent wastage is slight. Selection of the type of dryer, which is embodied in the stripping device 6, depends upon the degree of dehydration desired. Stage dryers with distribution devices or revolving drum dryers are examples of appropriate dryer types.
With respect to the required stripping steam, contact surface, steam decanter sediment and retention time, the solvent separation must be set up so that the solvent recovery rates are in excess of 99%, in order to achieve an economic operation of the system. The solvent recovery, or loss rate, is defined here as being such that less than 1% of the solvent stream used in the reaction extractor is removed via waste air, decanter sediment and water, or that over 99% of the solvent used is regenerated.
The stripped decanter centrifuge sediment FA is semi-solid or a pumpable stream of water containing high quantities of solids.
Semi-solid discharge can be used as fill on mining sites for re-cultivation of the excavated pits. The sedimented sludge is ecologically harmless, free of bitumen and biologically nontoxic.
The overflow from these ponds can be used in the production process or returned to the natural water cycle.
The multistage solvent recovery apparatus 4 consists of a multistage evaporator (not shown) whose stages vaporize solvents at various pressures. The condensation heat of the solvent vapour is used as vaporizing heat for each following evaporation stage, so that the heat employed is used in the form of stripping steam for each stage and thereby contributes to saving energy in the most energy-intensive step of the process. The solvent A
$ ~ ~.
vapour from the final stage releases its condensation heat to warm the water-solvent stream from the second sedimentation basin, or is used to heat the sludge used in the system intake.
As in all multistage concentrators, the number of evaporation stages is arrived at through calculation of economic viability, in which capital investment costs are offset against the savings of energy over the write-off period. For optimal use of energy and to ensure constantly operating temperature differences, the solvent-water stream from the hydrocyclonic overflows, and the centrifuged product from the spiral centrifuge are fed into the multistage vaporizer flowing counter to the heat carrier (already evaporated solvent). In this process, the solvent Lm evaporates out of the solvent-water stream and the remaining bitumen is concentrated on the surface of the liquid. This bitumen B is skimmed off in the skimmer 7 and is available for further processing in the bitumen processing process. The skimmer 7 need not be integrated in the vaporizer 4. For construction reasons, the skimmer 4 can also be installed outside the vaporizer, which makes particular sense if low levels of bitumen do not obstruct solvent evaporation by solid formation of bitumen film. Solvent recovery can also be carried out in multistage vaporizers, in which the heat carrier flows in parallel with the solvent to be concentrated. The skimmed water W is largely free of solids and can be used to heat the sludge being fed in. All installations and equipment in the process are constructed with an enclosed form so as to have no contact with the surrounding air, in order to avoid solvent loss through evaporation and offensive odours.
The solvent losses occur as a result of residual solubilities of the solvent, which is itself insoluble, in the skimmed-off water, and by removal of solvent in the solids discharge in the dryer.
The small quantities of solvent in the water are quickly broken down biologically. The solvent residues in the sand are broken down by soil bacteria as well, as they constitute a non-toxic biologically degradable compound.
Example 2 The process can also be used to decontaminate soils contaminated by oil. This process differs only in certain details from the above-described processing of sludge. There are differences related to the mechanical pre-treatment, which depend on the type of soil to be decontaminated.
Another distinguishing characteristic can be the size of the system. While typical throughputs in sludge treatment run at about 1000 cubic metres per hour, soil remediation systems are projected for throughputs of 1 to lOOm3/h. These systems must be transportable to a variety of cleanup sites in a relatively short period of time and are therefore constructed for mobile deployment (small soil remediation systems are constructed to fit in containers).
However, there are also applications in which considerably larger systems for soil decontamination would appear to be useful (e.g.
clearing up war damage or natural catastrophes).
The soil to be treated is fed into the extraction reactor, which for cost reasons is generally not a tubular reactor but rather a continuous agitator vessel or a cascade consisting of a series of agitator vessels.
In the reactor, the soil is washed with solvent, during which process the oil is transferred into the solvent or partially floats in the reactor.
The extraction reactor is followed by the above-described separation of soils, solvents and oil by mechanical decanting, solvent recovery and stripping out of the residual solvent by steam.
Claims (6)
1. A process for separating a mixture of water, solids or sludges, non-volatile hydrocarbons and other impurities by means of solvent extraction, comprising:
(a) preheating the mixture and diluting it with water and a solvent, and then mechanically separating and dehydrating the mixture to split it into (i) a water-and-solvent-rich phase in which the non-volatile hydrocarbons are released, and (ii) a solid-rich phase in which some solvent is still retained;
(b) subjecting phase (i) to multiple stage solvent recovery to evaporate out the solvent and returning such solvent to step (a), skimming the non-volatile hydrocarbons and removing skimmed water;
(c) subjecting phase (ii) to solvent stripping to separate the solvent from the solids and feeding such separated solvent to phase (i) in step (b); and (d) employing the separated solids as filler or as decontaminated soil.
(a) preheating the mixture and diluting it with water and a solvent, and then mechanically separating and dehydrating the mixture to split it into (i) a water-and-solvent-rich phase in which the non-volatile hydrocarbons are released, and (ii) a solid-rich phase in which some solvent is still retained;
(b) subjecting phase (i) to multiple stage solvent recovery to evaporate out the solvent and returning such solvent to step (a), skimming the non-volatile hydrocarbons and removing skimmed water;
(c) subjecting phase (ii) to solvent stripping to separate the solvent from the solids and feeding such separated solvent to phase (i) in step (b); and (d) employing the separated solids as filler or as decontaminated soil.
2. Process as in claim 1, wherein the solvent is an organic CFC-free solvent.
3. Process as in claim 2, wherein the solvent is petroleum benzin, toluene, benzene or a similar hydrocarbon-bearing solvent.
4. Process as in claim 1, 2 or 3, wherein said mechanical separation and dehydration is carried out by passing the mixture through a multiple stage hydrocyclone cascade and a multiple centrifuge apparatus, each hydrocyclone stage producing a solids-reduced overflow and a solids-enhanced underflow, the overflows being transferred to a sedimentation system for removing remaining solids, and the underflow of each hydrocyclone, other than a last of said hydrocyclones, forming a feed for next following hydrocyclones, and the underflow of said last hydrocyclone forming an intake of a first of said multiple centrifuges, and wherein each centrifuge produces a liquid phase and a sediment, said liquid phase being transferred to a sedimentation system for removing remaining solids, and the sedimentation from each centrifuge, other than the last, being used as a feed for a next following centrifuge, the sediment of the last centrifuge being transferred to a solvent stripping system for removing residual solvent, and wherein said sedimentation systems produce said water-and-solvent rich phase and a remaining solid, said remaining solid being fed to at least one said centrifuge and, together with said sediment from said centrifuges, to said solvent stripping system.
5. Process as in claim 4, wherein 1-30 mg/L of ionic polymers are added to the mixture before or after the first hydrocyclone stage and/or before or after the first centrifuge stage.
6. A process for separating a mixture of water, solids or sludges, non-volatile hydrocarbons and other impurities by means of solvent extraction, comprising:
(a) diluting the mixture with water and a solvent, and then mechanically separating and dehydrating the mixture to split it into (i) a water-and-solvent-rich phase in which the non-volatile hydrocarbons are released, and (ii) a solid-rich phase in which some solvent is still retained;
(b) subjecting phase (i) to multiple stage solvent recovery to evaporate out the solvent and returning such solvent to step (a), skimming the non-volatile hydrocarbons and removing skimmed water;
(c) subjecting phase (ii) to solvent stripping to separate the solvent from the solids and feeding such separated solvent to phase (i) in step (b); and (d) employing the separated solids as filler or as decontaminated soil.
(a) diluting the mixture with water and a solvent, and then mechanically separating and dehydrating the mixture to split it into (i) a water-and-solvent-rich phase in which the non-volatile hydrocarbons are released, and (ii) a solid-rich phase in which some solvent is still retained;
(b) subjecting phase (i) to multiple stage solvent recovery to evaporate out the solvent and returning such solvent to step (a), skimming the non-volatile hydrocarbons and removing skimmed water;
(c) subjecting phase (ii) to solvent stripping to separate the solvent from the solids and feeding such separated solvent to phase (i) in step (b); and (d) employing the separated solids as filler or as decontaminated soil.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP4208182.3 | 1992-03-12 | ||
| DE19924208182 DE4208182C2 (en) | 1992-03-12 | 1992-03-12 | Process for the separation of a mixture of water, solids or sludge, low volatile hydrocarbons and other accompanying substances |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2091502A1 CA2091502A1 (en) | 1993-09-13 |
| CA2091502C true CA2091502C (en) | 1999-05-04 |
Family
ID=6454060
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2091502 Expired - Fee Related CA2091502C (en) | 1992-03-12 | 1993-03-11 | Process to separate a mixture of water, solids or sludges, non-volatile hydrocarbons and other accompanying substances |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA2091502C (en) |
| DE (1) | DE4208182C2 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US11273475B2 (en) | 2020-02-12 | 2022-03-15 | Clean Planet Technology Inc. | High rate hydrocarbon solvent extraction system, process and method |
| RU2772332C1 (en) * | 2021-05-13 | 2022-05-18 | Общество с Ограниченной Ответственностью "ДИСТИЛИУМ" | Method for processing watered oil-containing waste |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1994023855A1 (en) * | 1993-04-19 | 1994-10-27 | Robertson, Struan, Glen | Recovery and destruction of toxics from contaminated soils |
| US5948242A (en) * | 1997-10-15 | 1999-09-07 | Unipure Corporation | Process for upgrading heavy crude oil production |
| WO2002102938A1 (en) * | 2001-06-18 | 2002-12-27 | Sasol Technology (Pty) Ltd | Method of separating particles from a hydrocarbon composition |
| CN100340503C (en) * | 2004-10-29 | 2007-10-03 | 中国石油化工股份有限公司 | Oil-containing sludge disposal method |
| CN103693825B (en) * | 2012-09-28 | 2015-10-28 | 中国石油天然气股份有限公司 | Resourceful treatment method for oily sludge |
| CN113402132B (en) * | 2021-05-11 | 2022-05-13 | 广州优特利环保科技有限公司 | Efficient treatment process for oily sludge |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4981579A (en) * | 1986-09-12 | 1991-01-01 | The Standard Oil Company | Process for separating extractable organic material from compositions comprising said extractable organic material intermixed with solids and water |
-
1992
- 1992-03-12 DE DE19924208182 patent/DE4208182C2/en not_active Expired - Fee Related
-
1993
- 1993-03-11 CA CA 2091502 patent/CA2091502C/en not_active Expired - Fee Related
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US11273475B2 (en) | 2020-02-12 | 2022-03-15 | Clean Planet Technology Inc. | High rate hydrocarbon solvent extraction system, process and method |
| RU2772332C1 (en) * | 2021-05-13 | 2022-05-18 | Общество с Ограниченной Ответственностью "ДИСТИЛИУМ" | Method for processing watered oil-containing waste |
Also Published As
| Publication number | Publication date |
|---|---|
| DE4208182C2 (en) | 1995-03-30 |
| DE4208182A1 (en) | 1993-09-16 |
| CA2091502A1 (en) | 1993-09-13 |
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