Technical Field

The present invention generally relates to a method and a system for the solidification of hydrocarbon wax from a liquid hydrocarbon mixture containing said hydrocarbon wax and non-wax hydrocarbons.

Background

During onshore crude oil production, the temperature of crude oil decreases as it is transported upwards through the production pipeline from the underground oil reservoir at subsurface levels to the relatively cooler earth surface where the oil extraction facilities are located.

Similarly, the temperature of crude oil in offshore crude oil production decreases as it is transported upwards through the production pipeline from the hot underground oil reservoir at subsurface levels to the relatively cooler ocean floor and subsequently to the floating platform where the oil extraction facilities are located.

The temperature at the onset of crystallization of hydrocarbon compounds typically increases with an increase in molecular weight and carbon number. Accordingly, waxy high carbon compounds in crude oil crystallize at higher temperatures than compounds with a lower number of carbons .

Therefore, when crude oil is transported from warmer to cooler zones, the waxy high carbon compounds crystallize before the compounds with a lower number of carbons do. However, because crude oil is a complex mixture of hydrocarbon compounds, the onset of crystallization of waxy high carbon compounds, known as the wax appearance temperature (WAT) of the crude oil, is unique for each crude oil sample because the WAT depends on the composition of the crude oil mixture and the concentration of each hydrocarbon component in the crude oil mixture. Whenever the bulk temperature of the crude oil falls below the WAT of the crude oil, the wax in the oil film near the inner wall of the pipeline crystallizes because the temperature of the crude oil is the lowest at the pipeline wall and increases radially inwards from the pipeline wall to the centre of the pipe. This liquid film has a consistency of a layer of jelly and contains both liquid oil and floating wax crystals. The jelly layer is more viscous than the crude oil containing no wax crystals flowing through the centre of the pipe and is therefore almost a no-flow zone. If the jelly layer is not removed, it grows on the inner walls of the pipeline and constricts the cross-sectional flow of the pipeline, resulting in a decrease of the production rate of crude oil. This flow constriction may also contribute to the temperature drop due to the Joule Thomson effect if gas is present in the crude oil.

Many oil fields produce heavy crude oil which has a high amount of waxy high carbon components. Therefore, the decrease in production rate due to wax deposits in these oil. fields can cost significant economic losses.

Methods used to treat wax deposits include chemical treatment, thermal treatment and mechanical treatment. Chemical treatment methods, such as the use of pour point depressants and wax inhibitors, alter the natural properties of the crude oil to reduce the formation of wax crystals. However, the chemical additives are relatively expensive and a high amount of additives are needed due to the frequency of chemical treatment.

In thermal treatment methods, hot oil or hot water is flushed into the pipeline to melt the wax deposits. However, thermal treatment requires plant shutdown, which translates into higher economic losses. Restarting plant operations pose further safety risks.

Mechanical treatment methods include the use of pipeline inspection gauges (PIGs) and wax cutting. PIGs are inserted into surface pipelines to clean residue deposited on their inner walls and are pushed along the line by the pressure of the oil flow. However, thick, wax deposits that narrow the inner diameter of the pipeline may cause the PIGs to get stuck. Intelligent pigging may be used to remove the stuck PIG, but intelligent PIGs on the market are currently still very expensive. It is also difficult to identify the section of the pipeline that is plugged. Further, excessive time is wasted between pigging operations and the deposits progressively get harder as they age.

There is therefore a need to provide a method of treating wax deposits that overcomes, or at least ameliorates, one or more of the disadvantages described above. ^'

Summary

According to a first aspect, there is provided a method for the solidification of hydrocarbon wax from a liquid hydrocarbon mixture containing said hydrocarbon wax and non-wax hydrocarbons, the method comprising the step of contacting the liquid hydrocarbon mixture with particles that encapsulate a phase change media, said particles being at a temperature below the wax appearance temperature of the liquid hydrocarbon mixture to solidify said hydrocarbon wax.

Advantageously, the phase change media possesses a high latent heat of melting. Thus, the phase change media is capable of acting as a heat sink to absorb a high amount of latent heat of the wax components in the liquid hydrocarbon mixture. Accordingly, the solidification of hydrocarbon wax components in the liquid hydrocarbon mixture is induced because the latent heat of solidification of hydrocarbon wax is absorbed by the phase change media.

More advantageously, the particles that encapsulate the phase change media provide a much larger surface area per unit mass of liquid for heat transfer as compared to conventional heat transfer equipment. Accordingly, the ratio of liquid hydrocarbon mixture the efficiency of heat transfer is much higher as compared to conventional heat transfer equipment.

Yet more advantageously, the disclosed method provides a continuous method to treat the problem of wax depositing in the pipeline. Thus, the disclosed method does not require any production downtime.

In one embodiment, the phase change media is a suspension, of nanoparticles in water. The water may be purified water.

Advantageously, the suspension of nanoparticles in purified water has a high latent heat of melting of about 300 kJ/kg. Further, providing a suspension of nanoparticles in water leads to the formation of uniform, nucleated icing because the nanoparticles act as a locus for crystallization when the water freezes, thus supercooling is avoided.

According to a second aspect, there is provided a system for the solidification of hydrocarbon wax from a liquid hydrocarbon mixture containing said wax hydrocarbons and non-wax hydrocarbons, the system comprising: a solidification zone for containing the liquid hydrocarbon mixture therein; and a plurality of particles disposed in said solidification zone for thermally contacting said hydrocarbon mixture while in said solidification zone, each of said particles encapsulating a phase change media, wherein in use, the phase change media enables said particles while in contact with said liquid hydrocarbon mixture to solidify said wax by being at a temperature below the wax appearance temperature of said liquid hydrocarbon mixture.

Definitions

The following words and terms used herein shall have the meaning indicated:

The term "hydrocarbon (s) " refers to organic material with molecular structures containing carbon bonded to hydrogen. Hydrocarbons may also include other elements, such as, but not limited to, halogens, metallic elements, nitrogen, oxygen, and/or sulfur. The source of the hydrocarbons may be from crude oils, gas oils and refined petroleum.

The term "hydrocarbon wax" is to be interpreted broadly to include hydrocarbons of high molecular weight, including but not limited to, mineral waxes, such as paraffin wax and microcrystalline wax. Hydrocarbon wax typically comprises alkanes and may contain large amounts of iso-alkanes. More particularly, in the context of the present specification, high carbon hydrocarbon wax refers to hydrocarbons having typically more than 40 carbon atoms, while low carbon hydrocarbon wax refers to hydrocarbons having typically between 20 to 40 carbon atoms . The terra "wax appearance temperature", as used within the context of the present specification, refers to a temperature wherein hydrocarbon wax as defined above present in a mixture of liquid hydrocarbons begins to crystallize. The wax crystals may be observed with the aid of optical equipment when exposed to infrared light. The wax appearance temperature is dependent on the composition of the liquid hydrocarbon mixture because of the complex thermodynamic influences of each component in multi- component systems. Thus, the wax appearance temperature of each mixture is unique.

The term "nanoparticle" refers to a particle with an average particle ^' size of less than about 1000 nm, particularly less than 500 nm and more particularly, less than 200 nm. The particle size may refer to the diameter of the particles where they are substantially spherical. The particles may be non-spherical and the particle size range may refer to the equivalent diameter of the particles relative to spherical particles or may refer to a dimension (length, breadth, height or thickness) of the non-spherical particle.

The term "phase change media" as used within the context of the specification is any medium that induces a transition from one state of matter to another state of matter, for example, from liquid state to solid state.

The term "purified" as used within the context of the specification is used to describe water that has been purified to remove impurities.

The word "substantially" does not exclude "completely" e.g. a composition which is "substantially free" from Y may be completely free from Y. Where necessary, the word "substantially" may be omitted from the definition of the invention. Unless specified otherwise, the terms "comprising" and "comprise", and grammatical variants thereof, are intended to represent "open" or "inclusive" language such that they include recited elements but also permit inclusion of additional, unrecited elements.

As used herein, the term "about", in the context of concentrations of components of the formulations, typically means +/- 5% of the stated value, more typically +/- 4% of the stated value, more typically +/- 3% of the stated value, more typically, +/- 2% of the stated value, even more typically +/- 1% of the stated value, and even more typically +/- 0.5% of the stated value.

Throughout this disclosure, certain embodiments may be disclosed in a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the disclosed ranges. Accordingly, the description of a range should be considered to have specifically disclosed all the possible sub-ranges as well as individual numerical, values within that range. For example, description of a range such as from 1 to 6 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range.

Detailed Disclosure of Embodiments

Exemplary, non-limiting embodiments of a method for the solidification of hydrocarbon wax from a liquid hydrocarbon mixture containing said hydrocarbon wax and non-wax hydrocarbons will now be disclosed. The method for the solidification of hydrocarbon wax from a liquid hydrocarbon mixture containing said hydrocarbon wax and non-wax hydrocarbons comprises the step of contacting the liquid hydrocarbon mixture with particles that encapsulate a phase change media, the particles being at a temperature below the wax appearance temperature of the liquid hydrocarbon mixture to solidify said hydrocarbon wax in a solidification zone.

The solidification zone may be within the annulus of a pipeline. The particles may be capsules or beads and encapsulate a phase change media. The phase change media may be any suitable material with a high latent heat of melting. The phase change media may also be water.Alternatively, the phase change media may be a suspension of nanoparticles in purified water. The nanoparticles may have a diameter selected from the group consisting of about 50 nm to about 500 nm, about 100 nm to about 500 nm, about 150 nm to about 500 nm, about 200 nm to about 500 nm, about 250 nm to about 500 nm, about 300 nm to about 500 nm, about 350 nm to about 500 nm, about 400 am to about 500 nm, about 450 nm to about 500 nm, about 50 nm to about 450 nm, about 50 nm to about 400 nm, about 50 nm to about 350 nm, about 50 nm to about 300 nm, about 50 nm to about 250 nm, about 50 nm to about 200 nm, about 50 nm. to about 150 nm, and about 50 nm to about 100 nm. In one embodiment, the nanoparticles have a diameter of about 100 nm to about 200 nm.

The method comprises the step of solidifying the hydrocarbon wax on the surface of the particles. The particles act as a locus for the hydrocarbon wax to solidify there on. The hydrocarbon wax solidifies as crystals and these crystals are suspended in the interfacial layer of liquid hydrocarbons adjacent to the surface of the particles, thus appearing as a jelly layer. In the disclosure herein, the terms "interfacial layer" and "jelly layer" are used interchangeably to refer to the thin film of liquid hydrocarbons adjacent to the surface of the particles that contain wax crystals present in suspension. The jelly layer on the surface of the particles may comprise of more than 15 vol% of hydrocarbon wax components. In one embodiment, the jelly layer on the surface of the particles comprise of 25 vol% of hydrocarbon wax components. In another embodiment, the jelly layer on the surface of the particles comprise of 50 vol% of hydrocarbon wax components.

The size of wax crystals in the jelly layer depends on the number of carbon atoms present in the hydrocarbon wax as well as the rate of crystallization. Specifically, the higher the number of carbon atoms in the wax, the smaller the size of the wax crystals.

Advantageously, solidification is localized on the surface of the particles in the solidification zone and is thus easily identifiable.

The solidification of hydrocarbon wax components in the hydrocarbon mixture occurs when the temperature of the hydrocarbon mixture is at or under the wax appearance temperature of the mixture. The wax appearance temperature of the liquid hydrocarbon mixture varies with the concentration of the hydrocarbon wax in the hydrocarbon mixture. Particularly, the wax appearance temperature of a mixture decreases as the concentration of hydrocarbon wax components in the mixture decreases. Accordingly, hydrocarbon wax components in the liquid hydrocarbon mixture may be removed until the wax appearance temperature of the bulk liquid hydrocarbon mixture is lower than the temperature of the bulk hydrocarbon mixture in the solidification zone, thereby allowing the continued production of liquid hydrocarbons with a lower probability of having plugged flow.

Advantageously, the disclosed method will significantly reduce any risks associated with, for example, re-starting operations in crude oil production and enlarge the critical time window allowed for such operations with special conditions during crude oil production .

The method may further comprise the step of maintaining the fluid flow conditions of the liquid hydrocarbon mixture in the solidification zone in the turbulent flow regime.

If the bulk flow of the liquid hydrocarbon mixture is not in the turbulent regime, the shear rate of the flow may not be sufficient to induce turbulent burst actions and remove the larger crystals of lower carbon wax compounds from the jelly layer. However, if the bulk flow of the liquid hydrocarbon mixture is excessively turbulent, the excessive shear, of the turbulent flow will totally remove the jelly layer into the main liquid hydrocarbon flow, preventing the accumulation of undesirable smaller wax crystals of high carbon wax compounds in the jelly layer on the surface of the particles .

Advantageously, the burst activity of the turbulent flow causes the larger crystals of lower carbon wax compounds to mix with, the relatively warmer liquid hydrocarbon mixture and melt, thereby rejoining the main liquid hydrocarbon flow. Consequently, the undesirable, smaller crystals of high carbon hydrocarbon wax may be progressively concentrated in the jelly layer resulting in an accumulation of high carbon wax on the surface of the particles. Advantageously, the ability and ease of the disclosed system to selectively accumulate high carbon wax from a hydrocarbon mixture is an improvement over conventional mechanical treatment methods.

The desired fluid flow conditions may be maintained by any known method in the art, such as by pumping. In one embodiment, the desired fluid flow conditions · is maintained by pumping the particles that encapsulate a phase change media at a sufficiently high pressure into the solidification zone. In this embodiment, the range of pressures may be selected from the group consisting of about 0.5 Pa to about 3.0 MPa, about 1.0 MPa to about 3.0 MPa, about 1.5 MPa to about 3.0 MPa, about 2.0 MPa to about 3.0 MPa, about 2.5 MPa to about 3.0 MPa, about 0.5 MPa to about 2.5 MPa, about 0.5 MPa to about 2.0 MPa, about 0.5 MPa to about 1.5 MPa, and about 0.5 MPa to about 1.0 MPa.

In one embodiment, the method further comprises the step of separating the particles with the solidified hydrocarbon wax from said liquid hydrocarbon mixture.

As a result of the separation step, a first stream comprising substantially of particles with the solidified hydrocarbon wax and a second stream comprising substantially of the liquid hydrocarbon mixture may be obtained. The solidified hydrocarbon wax on the surface of the particles in the first stream may be in the form of a jelly layer. The jelly layer may be very viscous and may comprise of about 15 vol% to about 50 vol.% of hydrocarbon wax crystals suspended in liquid hydrocarbon. Advantageously, the hydrocarbon wax crystals in the jelly layer may be the smaller high carbon wax crystals that have been concentrated in the jelly layer in the solidification zone.

The second stream may be introduced back into the main pipeline containing the liquid hydrocarbon mixture. In one embodiment, the method further comprises the step of heating the first stream to obtain a third stream comprising substantially of liquid hydrocarbon wax and a fourth stream comprising substantially of said particles that encapsulate a phase change media. The concentration of liquid hydrocarbon wax in the third stream may be about at least 75 vol%.

Advantageously, the heating step enables the removal of solidified hydrocarbon wax on the particles in the first stream, thereby permitting the continued effective heat transfer between the liquid hydrocarbon mixture and the particles in the solidification zone when the particles in the fourth stream are introduced back into the solidification zone. This further enables the continued solidification of the hydrocarbon wax components remaining in the liquid hydrocarbon mixture in the solidification zone.

A refrigerant may be introduced into the first stream during the heating step. The refrigerant may also be a solvent that dissolves the jelly layer. In one embodiment, the refrigerant is propane. The heating step may be performed at a temperature above the WAT of the liquid hydrocarbon mixture.

In the embodiment where the refrigerant is propane, the heating step may be carried out at a range of temperatures selected from the group consisting of about 50°C to about 80°C, about 55°C to about 80°C, about 60°C to about 80°C, about 65°C to about 80°C, about 70°C to about 80°C, about 75°C to about 80°C, about 50°C to about 75°C, about 50°C to about 70°C, about 50°C to about 65°C, about 50°C to about 60°C, and about 50°C to about 55°C. Further, in the embodiment where the refrigerant is propane, the heating step may be carried out at a range of pressures selected from the group consisting of about 2.0 MPa to about 3.0 MPa, about 2.5 MPa to about 3.0 MPa, and about 2.0 MPa to about 2.5 MPa .

The method may further comprise the step of cooling the fourth stream comprising substantially of said particles that encapsulate a phase change media to a temperature below the WAT of the liquid hydrocarbon mixture. In one embodiment, the fourth stream is cooled to a temperature of less than 20°C below the WAT of the liquid hydrocarbon mixture.

The cooling step may comprise throttling the refrigerant. When the refrigerant is propane, the pressure may be throttled to a pressure in the range of about 0.5 MPa to about 0.7 MPa.

The cooled refrigerant may be subsequently introduced into a compressor to increase the pressure of the refrigerant for continued feeding into the first stream during the heating step.

Advantageously, the particles may be recycled to extract hydrocarbon wax. In one embodiment, the phase change media encapsulated in the particles may have a high latent heat of melting. Advantageously, the particles are capable of acting as a heat sink to absorb a large amount of heat in the encapsulated media. Advantageously, the temperature of the particles may remain below the WAT of the bulk of the liquid hydrocarbon mixture for a longer period of time.

In one embodiment, the method further comprises the step of pumping the cooled stream back to said liquid hydrocarbon mixture in the solidification zone. Advantageously, the particles may be reused, thereby reducing cost.

In one embodiment, there is disclosed a system for the solidification of hydrocarbon wax from a liquid hydrocarbon mixture containing said hydrocarbon wax and non-wax hydrocarbons. The system comprises a solidification zone for containing the liquid hydrocarbon mixture therein; and a plurality of particles disposed in said solidification zone for thermally contacting the hydrocarbon mixture while in said solidification zone, wherein each of the particles encapsulates a phase change media. In use, the phase change media enables the particles while in contact with the liquid hydrocarbon mixture to solidify the wax by being at a temperature below the WAT of the liquid hydrocarbon mixture.

The solidification zone may be a pipeline containing a liquid hydrocarbon mixture such as crude oil.

The shell material of the particles may be any suitable material that is a good heat conductor. Exemplary shell materials include copper or aluminium. In one embodiment, the shell material is copper.

The particles may be of any suitable shape. In one embodiment, the particle is a spherical particle. Advantageously, the spherical particle maximizes the surface area for heat transfer. The outside diameter of the particles may be about 2 mm to about 8 mm, about 3 mm to about 7 mm and about 4 mm to about 6 mm. In one embodiment, the outside diameter is 3.2 mm. The inside diameter of the particles may be about 1 mm to about 9 mm, about 2 mm to about 8 mm and about 3 mm to about 7 mm. In one embodiment, the inside diameter is 2.8 mm.

The particle encapsulates a phase change media. The phase change media may be any suitable material that has a high latent heat of melting.

Table 1 below shows the correlation of the number and dimensions of the particles with the volume of hydrocarbon wax extracted from the liquid hydrocarbon mixture. The voidage of the particles in the liquid hydrocarbon mixture within an arbitrary solidification zone volume of 1 m ³ is fixed at 50% and a deposition of jelly layer of 2 mm from the surface of the particles is assumed.

Table I

Particle Particle Particle REACTOR REACTOR REACTOR Jellv Laver WAX diameter volume area Void No. of A dep depos Vol Vol mm m m m ² m Particles m ² mm m m

2 0.002 4.2E-09 1.3E-05 0.5 119,366,207 1500 2 3.0 0.60

0.003 1.4E-08 2.8E-05 0.5 35,367,765 1000 2 2.0 0.40

4 0.004 3.4E-08 5.0E-05 0.5 14,920,776 750 2 1.5 0.30

5 0.005 6.5E-08 7.9E-05 0.5 7,639,437 600 2 1.2 0.24

6 0.006 1.1E-07 1.1E-04 0.5 4,420,971 500 2 1.0 0.20

7 0.007 1.8E-07 1.5E-04 0.5 2,784,051 429 2 0.9 0.17

As can be seen in Table 1 above, the particles provide a very large heat transfer area for the hydrocarbon wax to solidify on. For example, particles of 3 mm in diameter have a surface area of 280 mm ² and can extract a volume of 0.4 m ³ of wax. It is thus evident that the heat transfer efficiency of the disclosed method is superior to conventional heat transfer methods.

In one embodiment, the phase change media is water. Advantageously, water has a high latent heat of melting of 300 kJ/kg and is capable of absorbing a significant amount of the latent heat of solidification of hydrocarbon wax, thereby enabling the solidification of the wax.

In one embodiment, the phase change media is a suspension of nanoparticles in purified water. The nanoparticles may be in the form of a powder and the suspension may have less than 1 vol% of nanoparticles in the water. Advantageously, the nanoparticles in the suspension facilitate a rapid and uniform nucleation and solidification.

The fluid flow conditions of said liquid hydrocarbon mixture within said solidification zone may be configured to be maintained in the turbulent flow regime. The desired fluid flow conditions may be maintained by any known method in the art . A pump may be provided to pump the particles that encapsulate a phase change media into the solidification zone to achieve the desired fluid flow conditions. The particles may be pumped at a range of pressures selected from the group consisting of about 0.5 MPa to about 3.0 MPa, about 1.0 MPa to about 3.0 MPa, about 1.5 MPa to about 3.0 MPa, about 2.0 MPa to about 3.0 MPa, about 2.5 MPa to about 3.0 MPa, about 0.5 MPa to about 2.5 MPa, about 0.5 MPa to about 2.0 MPa, about 0.5 MPa to about 1.5 MPa , and about 0.5 MPa to about 1.0 MPa.

In one embodiment, the system further comprises a first separator to separate said particles with the solidified hydrocarbon wax from said liquid hydrocarbon mixture to obtain a first stream comprising substantially of particles with the solidified hydrocarbon wax and a second stream comprising substantially of the liquid hydrocarbon mixture. The first separator may be configured to remove at least 95% of the particles.

The first separator may be a horizontal separator, a vertical separator or a tangential or cyclone separator. In one embodiment, the separator is a cyclone separator. The cyclone separator may optionally have a filter on one of the exits of the cyclone separator.

In one embodiment, the system further comprises a heat exchanger to heat the first stream comprising substantially of particles with the solidified hydrocarbon wax to melt said solidified hydrocarbon wax and obtain a third stream comprising substantially of liquid hydrocarbon wax and a fourth stream comprising substantially of said particles that encapsulate a phase change media. The heat exchanger may be a propane condenser, wherein the propane condenser may be configured to heat the first stream to a temperature in the range of about 50°C to about 80°C, or about 55°C to about 80°C, or about 60°C to about 80°C, or about 65°C to about 80°C, or about 70°C to about 80°C, or about 75°C to about 80°C, or about 50°C to about 75°C, or about 50°C to about 70°C, or about 50°C to about 65°C, or about 50°C to about 60°C, or about 50°C to about 55°C. The propane condenser may be configured to a pressure of about 2.0 Pa to about 3.0 MPa, or about 2.5 MPa to about 3.0 MPa, or about 2.0 MPa to about 2.5 MPa.

In one embodiment, the system further comprises a second separator to separate the third stream and the fourth stream.

In one embodiment, the system further comprises a refrigerant to cool the fourth stream to a temperature below the wax appearance temperature of the liquid hydrocarbon mixture. The refrigerant may be any suitable refrigerant known in the art. In one embodiment, the refrigerant is propane. The refrigerant may be configured to cool the fourth stream to a temperature less than 20°C below the wax appearance temperature of the liquid hydrocarbon mixture. The refrigerant may be throttled to a low pressure to cool the particles in the fourth stream. When the refrigerant is propane, the propane may be throttled to a pressure of about 0.5 MPa to about 0.7 MPa.

The system may further comprise a compressor to increase the pressure of the cooled refrigerant for continued feeding into the heat exchanger.

In one embodiment, the system further comprises a pump to pump the cooled stream back to said liquid hydrocarbon mixture in the solidification zone. The pump may be a positive displacement pump.

The solidification zone may refer to any volume where the solidification of the hydrocarbon wax occurs. In one embodiment, the solidification zone is a pipe. Brief Description Of Drawings

The accompanying drawings illustrate a disclosed embodiment and serves to explain the principles of the disclosed embodiment. It is to be understood, however, that the drawings are designed for purposes of illustration only, and not as a definition of the limits of the invention.

Fig. la is a process flow diagram of a system for the removal of wax components in crude oil in accordance with an embodiment disclosed herein.

Fig. lb is a schematic diagram of a particle in accordance with an embodiment disclosed herein.

Fig. 2 is a graph showing how the wax appearance temperature of crude oil varies with the amount of wax extracted from the crude oil.

In the figures, like numerals denote like parts.

Detailed Description Of Drawings

Referring to Fig. la, the process flow diagram of a system 100 for the removal of wax components in crude oil in accordance with an embodiment of the present disclosure is shown.

Spherical copper particles 102 comprising a suspension 400 of nanoparticles in purified water therein (as seen in Fig. lb) are pumped into a section of a crude oil extraction pipeline 104 to form a fluidized bed. The particles 102 are at -10°C prior to introduction into pipeline 104. Advantageously, suspension 400 has a high latent heat of melting and a large amount of heat may be contained in suspension 400 within particles 102 before a change in temperature occurs. Accordingly, the particles 102 are able to remain at a temperature below the wax appearance temperature (WAT) of the crude oil during its residence time in pipeline 104. Furthermore, the nanoparticles in suspension 400 facilitate a rapid and uniform nucleation and solidification. Therefore, liquid wax components present in the crude oil crystallizes uniformly onto the surface of the particles 102 to produce a jelly layer 210 adjacent to the surface of the particles 102, as seen in Fig. lb.

The crude oil in pipeline 104 is maintained in the turbulent flow regime by pump 150. The Reynolds number of a flow in a pipe is calculated with the following equation :

Re = Q ^■ D _H / vA,

wherein Q is the volumetric flow rate, D _H is the hydraulic diameter of pipeline 104, v is the kinematic viscosity of the crude oil and A is the cross-sectional area of pipeline 104. Advantageously, the flow regime causes the large crystals of low carbon wax to be removed from the jelly layer 210 adjacent to the surface of the particles 102, thus selectively concentrating the small crystals of high carbon wax in the jelly layer 210.

A cyclone separator 110 is located downstream of the pipeline 104 to separate a slurry stream 114 containing the particles 102 with jelly layer 210 from a crude oil stream 112 that has a reduced amount of liquid wax components. Crude oil stream 112 has a WAT lower than the bulk temperature of the crude oil in pipeline 104 and' is pumped back into the crude oil extraction pipeline 104. The slurry stream 114 is passed through a propane condenser 120 at 80°C to melt the wax crystals in the jelly layer adjacent to the surface of the particles 102 and obtain stream 116 containing liquid hydrocarbon wax and stream 118 containing particles 102. Separator 130 separates streams 116 and 118. The liquid wax stream 116 is removed from the system 100. The particles 102 in stream 118 are cooled to -10°C by throttling propane in cooler 140 before being pumped by pump 150 back into the crude oil extraction pipeline 104.

Fig. lb shows a schematic of a particle in accordance with ah embodiment disclosed herein. The copper particle 102 comprises an outer shell 200 and an inner cavity 300. The spherical copper particle 102 may be manufactured by a blow moulding process, comprising the formation of the outer shell 200 and the inner cavity 300. In the blow moulding process, the particle material is mixed with or contains as part of the composition a blowing agent which decomposes at high temperature. As the temperature is quickly raised, the blowing agent decomposes and the resulting gas expands from within, thus forming the copper particle 102 comprising an outer shell 200 and an inner cavity 300. A conduit is formed through the outer shell 200, to allow for the suspension 400 of nanoparticles in purified water to be injected into the inner cavity 300 of the particle. The conduit is then sealed to allow the suspension 400 to remain within the copper particle 102.

Referring to Fig. 2, the wax appearance temperature (WAT) of a particular crude oil composition varies with the amount of wax present in the crude oil. Specifically, the WAT of a particular crude oil composition decreases with a decreasing amount of wax present in the crude oil. For example, when none of the wax is extracted from the crude oil, the WAT is about 50°C. When about 40% of wax is extracted from the crude oil, the WAT is about 15°C. Accordingly, in surface pipelines where the ambient temperature is about 25°C, the probability of wax deposition for crude oil with a WAT of about 15°C is reduced. Therefore, wax may be extracted from the crude oil until the WAT of the crude oil is lower than the bulk temperature of the main crude flow in the pipeline. Below this point, the waxy high carbon compounds in the crude oil are less likely to precipitate out as solid and cause plugging of the pipeline. Accordingly, the low temperature of the copper particles 102 advantageously aids in the crystallization of wax in the interfacial oil jelly layer 210 adjacent to the surface of the particles 102 and the particles 102 have a residence time in pipeline 104 so that wax is extracted until the WAT of the crude oil is lower than the bulk temperature of the crude oil in pipeline 104. Advantageously, the wax crystallization is localized on the surface of the particles 102 which are subsequently removed from the crude oil extraction pipeline 104.

Applications

. Advantageously, the system does not incur additional production downtime.

Advantageously, the system permits the crude oil to have a wax appearance' temperature that is lower than the ambient temperature.

Advantageously, the particles encapsulate a substance with high latent heat of melting so that a large amount of heat may be absorbed by the encapsulated substance. Thus, the substance is capable of acting as a heat sink to absorb a high amount of . heat from the liquid hydrocarbon mixture. Accordingly, the solidification of hydrocarbon wax components in the liquid hydrocarbon mixture is induced because the latent heat of solidification of hydrocarbon wax is absorbed by the phase change media. Advantageously, wax crystallization is localized and is thus easily identifiable.

Advantageously, the solidified wax is subsequently removed from the crude oil extraction system, reducing the possibility of plugging of the crude oil extraction pipeline during normal operations or result in a high risk during restarting after prolonged flow interruptions, thereby also reducing the economic losses associated with production downtime.

It will be apparent that various other modifications and adaptations of the invention will be apparent to the person skilled in the art after reading the foregoing disclosure without departing from the spirit and scope of the invention and it is intended that all such modifications and adaptations come within the scope of the appended claims.