UPGRADING HEAVY OIL BY VISBREAKING

Abstract

Methods, systems and other embodiments associated with upgrading heavy oil by visbreaking are presented. A method of upgrading heavy oil includes mixing raw heavy oil with flue gases, CO2 and/or steam to produce a mixed heavy oil. This mixture is then heated to produce heated heavy oil. High pressure pulses are created in the heated heavy oil to crack the heated heavy oil to produce cracked oil with a lower viscosity than the heavy oil.

Description

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates generally to systems and methods for reducing the density of heavy oils. More particularly, the systems and methods relate to upgrading heavy hydrocarbon oils for transportation by pipeline from production fields to refineries for further processing. Specifically, the methods and systems of the present invention involve reducing the viscosity of the oil to allow for easier pumping and transportation.

2. Background Information

One way to prepare heavy oil for transportation in a pipe is to add a diluent to the oil. This is done at blending stations where the diluent is added to meet pipeline specifications for both density and viscosity. A common diluent is naphtha, a light hydrocarbon with a typical American Petroleum Institute (API) gravity of 60. The cost of naphtha is normally at a premium because it is the light liquid fraction of crude oil at room temperature. The cost of naphtha is normally 15 to 20% higher than the West Texas Intermediate (WTI) crude price. In addition to purchasing naphtha, producers must transport it to their site and store it at the site for later blending with heavy oil.

As the ability to easily extract conventional light and medium weight crude oils declines, the increase in production of heavy oils has created a demand for diluent. The increase demand for diluent has significantly increased the cost of the diluent. The increased cost of diluent drives up the operating costs and this cost is passed on to crude oil products.

To improve the pumping of heavy crude oil, a number of alternative methods (e.g., processes) have been proposed for decreasing the density of heavy oil. The primary alternatives proposed include visbreaking, deasphalting, coking and hydrocracking. In deasphalting, the heavy fraction, asphalt, is separated and removed. This is done by added solvents to the heavy oil to selectively precipitate the fraction of asphalt from the other lighter fractions. The precipitation is performed in specially designed contact towers that operate at selective pressures and temperatures.

In visbreaking, the heavy oil is thermally cracked. This is achieved at high temperatures followed by a rapid quenching and settling. The visbreaking is limited to API gravity increments of 3 to 5 API. The visbreaking process requires high maintenance because a furnace used in the visbreaking process often needs cleaned due to the buildup of coke, an undesirable product of visbreaking. High temperatures and pressures used in the visbreaking process require costly equipment that can handle the high temperatures and pressures.

Hydrocracking is the preferred process because it provides yields higher than deasphalting and visbreaking. Hydrocracking adds hydrogen to the heavy oil and a catalyst at high pressures and temperatures. The higher temperature results in a higher conversion rate of heavy oil to upgraded oil. The better the mixing of the heavy oil, hydrogen and catalyst, the better the conversion rate and lower the residency time which results in a higher throughput.

However, these processes require a significant investment in equipment that may not be available at a producer's job site. Therefore, these processes require the heavy crude to be transported to a refinery suitable for upgrading the heavy crude by one of these processes. These processes require high pressures and temperatures. A high pressure plant requires not only high pressure vessels but accessory equipment such as pumps, compressors, valves, as well as more energy for driving the high pressure pumps, compressors, and so on.

Conventional visbreaking or conventional deasphalting alone often does not provide sufficient viscosity reduction for all heavy crudes. Attempts to reduce the viscosity to a required level by these methods usually lead to an incompatible two phase product from visbreaking and to a very low yield of deasphalted oil from deasphalting. A better way of upgrading heavy oil is needed.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more preferred embodiments that illustrate the best mode(s) are set forth in the drawings and in the following description. The appended claims particularly and distinctly point out and set forth the invention.

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate various example methods, and other example embodiments of various aspects of the invention. It will be appreciated that the illustrated element boundaries (e.g., boxes, groups of boxes, or other shapes) in the figures represent one example of the boundaries. One of ordinary skill in the art will appreciate that in some examples one element may be designed as multiple elements or that multiple elements may be designed as one element. In some examples, an element shown as an internal component of another element may be implemented as an external component and vice versa. Furthermore, elements may not be drawn to scale.

FIG. 1 illustrates a first embodiment of a system for upgrading heavy oil.

FIGS. 2 and 3 illustrate a cavitation valve used in a second and preferred embodiment for upgrading heavy oil.

FIG. 4 illustrates a first configuration of the second embodiment that is a system for upgrading heavy oil that hydrocracks the heavy oil.

FIG. 5 illustrates a second configuration of the second embodiment that is a system for upgrading heavy oil that deasphalts the heavy oil.

FIGS. 6A and 6B illustrate a third configuration of the second embodiment that is a system for upgrading heavy oil that is another version of a system that deasphalts the heavy oil.

FIG. 7 illustrates a fourth configuration of the second embodiment that is a system for upgrading heavy oil that visbreaks the heavy oil.

FIG. 8 illustrates fifth configuration of the second embodiment that is a system for upgrading heavy oil that is another version of a system that visbreaks the heavy oil.

FIG. 9 illustrates a method of upgrading heavy oil.

FIG. 10 illustrates a more detailed variation of the method of upgrading heavy oil shown in FIG. 9.

FIGS. 11A-C illustrate three different configurations of the first embodiment that are modular skid and/or truck mounted versions of the first embodiment of a system for upgrading heavy oil.

Similar numbers refer to similar parts throughout the drawings.

DETAILED DESCRIPTION

FIG. 1 illustrates a first embodiment of a system 10 used to upgrade heavy oil. The system 10 upgrades heavy oil to produce an oil that has a lower viscosity and a lower density than the original oil. In the first embodiment, the system 10 is comprised of a heater 2 (e.g., furnace) and a reaction chamber 4. The heater 2 may receive heavy oil from a storage tank 6 and prepare the heavy oil for cracking in the reaction chamber 4 by heating the oil. The heater 2 may heat the heavy oil to any temperature. However, in the first embodiment, the heater 2 is configured to heat the heavy oil up to about 450 degrees Celsius which is a lower temperature than has been used in prior systems. In other embodiments the system 10 may include a pump for pressurizing the heated oil before it is pumped into the reaction chamber 4.

The reaction chamber 4 is configured to crack the heated heavy oil by subjecting the heated heavy oil to pressure fluctuations. When the oil is subjected to significantly high pressure fluctuations, microscopic gas bubbles are created that expand and implode violently. The imploding microscopic bubbles raise the temperature at the interface of the microbubbles and heavy oil. The temperature rise due to bubble collapse generates a localized extremely high cumulative amount of energy. This energy enhances the cracking of the heated heavy oil because of the formation of radicals and cleavage of bonds. Cracking of the heated heavy oil is generally the breaking of large hydrocarbon molecules into smaller hydrocarbon molecules. The cracked oil can then be passed to a post processing system 8 to separate different petroleum fractions from the upgraded oil. The post processing system 8 may include tower separators, overhead separators, heat exchangers, storage units and other devices to be discussed later.

As discussed below, the reaction chamber 4 may include a cavitation valve configured to create high pressure differentials. The cavitation valve can create a pressure differential of over 6000 psig which is a much greater differential than is achieved by traditional systems of upgrading heavy oil. This high pressure differential increases the quality of the upgraded oil produced by the system 10. Additionally, the cavitation valve operates under high pressure while the remainder of the system 10 can operate under lower pressures. In a traditional system, much more of the system for upgrading heavy oil is required to operate under high pressure. A system with more components operating under higher pressure require more expensive components that can handle high pressure and is therefore more costly than the system 10 of FIG. 1. Higher pressure components can require more maintenance due to the difficulty of operating under high pressure. The system 10 of FIG. 1 reduces maintenance costs because the reaction chamber 4 operates under high pressure while the remainder of the system 10 can operate at much lower pressures.

Traditional systems and methods for upgrading require heavy oil to be heated and pressurized for 3 to 30 minutes before the heavy oil was cracked and upgraded. In the first embodiment, the heated heavy oil has a residency time of one second or less in the reaction chamber 4. In other embodiments, the residency time may be other less than two seconds, less than three seconds or other residency times. The shorter residency time translates into much smaller equipment needed to upgrade heavy oil for the same throughput capacity as a traditional process. The system 10 of FIG. 1 also has a lower operating cost due to lower operating pump pressures and a lower temperature in heater 2 in comparison to a traditional upgrading process. This translates into lower electrical and thermal energy requirements.

The system 10 may be mounted in a fixed location as a local refinery. Alternatively, the system 10 of FIG. 1 may be mounted on one or more skids because the equipment of the system 10 has a small footprint and is much smaller than traditional systems for upgrading heavy oil. The system 10 may be mounted on skids or trucks and brought to a remote production field so that the heavy oil may be upgraded before the heavy oil is transported from the production field. For example, FIGS. 11A-C shows a truck 1101 with the system 10 of FIG. 1 mounted on three skids 1103, 1105 and 1107. The system 10 is shown as three units 1102, 1104 and 1106 with one unit on one skid. The other details shown in FIGS. 11A-C will be discussed later when discussing how the system 10 can be reconfigured. However, the system 10 may be mounted on a greater number of skids or fewer than two skids. The system 10 may alternatively be mounted directly to one or more trucks or partially mounted on trucks, skids or other mounting surfaces. When the system 10 is mounted on two or more skids or trucks, the system 10 is easily transported to a job site and easily assembled at the job site.

The system 10 is scalable and multiple components can be added to the system 10 to achieve the desired daily flow rates of a particular producer of heavy oil. For example, the system 10 may be operated to process 250 barrels per day or the system 10 may be scaled to process 100,000 barrels per day.

After the system 10 is assembled, the system 10 can be operated with less supervision than a traditional upgrading system requires. For example, the system 10 may include an American Petroleum Institute (API) density analyser 1121 (shown in FIGS. 11A-C) to automatically measure the heavy oil density of oil input to the system 10. A computer controller 1120 (shown in FIGS. 11A-C) of the system 10 will then optimize the temperature at which the heater 2 is to heat the heavy oil. The computer controller 1120 can also select the pressure fluctuations that the reaction chamber 4 is to subject the heated heavy oil to. For example, the computer controller 1120 can configure the reaction chamber 4 to create pressure differentials between −2000 pounds per square inch gauge (psig) and 4000 psig and between 10 to 100 hertz. In another embodiment, the computer controller 1120 can also select the frequency of the pressure fluctuations. For example, the computer controller 1120 can control lengths of conduits feeding oil to a cavitation valve discussed below to control the frequency of the pressure fluctuations.

In a second and preferred embodiment, the reaction chamber 4 comprises a cavitation valve 26 as shown in FIG. 2. The cavitation valve 26 is similar to the valve described in United States Patent Application No. 2008/0256947. The reaction chamber 4 includes a first conduit 22 and a second conduit 24 connected to the cavitation valve 26 configured to supply heated heavy oil to the cavitation valve 26. The other ends of the first conduit 22 and the second conduit 24 are connected to a plenum 20. The plenum 20 receives heated heavy oil from the heater 2 through conduit 18.

The cavitation valve 26 includes a housing 27 which includes chambers 33 and 34 connected to the first conduit 22 and the second conduit 24. Cavitation valve 26 has a movable valve member 36 configured to reciprocate longitudinally as indicated by arrow 29. The valve member 36 has sealing members 38 and 40 in its ends. Sealing members 38 and 40 can sit against valve seats 42 and 44 respectively. The valve member 36 can move between a first position, as shown in FIG. 2, in which fluid in second conduit 24 can flow through cavitation valve 26 to an output conduit 28 (while sealing member 38 bears against valve seat 42 and thereby prevents oil from the first conduit 22 from flowing to output conduit 28). When the valve member 36 slides to a second position, as shown in FIG. 3, oil from the first conduit 22 can flow through the cavitation valve 26 to output conduit 28 while the flow of oil from the second conduit 24 to output conduit 28 is blocked by sealing member 40 (which seals against valve seat 44).

In operation, heated heavy oil is received through conduit 18 into the plenum 20. In the preferred embodiment, the oil is pressurized within the plenum 20. The heated oil may be pressurized by pumping the oil from the heater 2 to the plenum 20 with a high-pressure pump. A centrifugal pump or another kind of pump may also be used to pump the heated oil to the plenum 20 with high pressure. The pressure in plenum 20 causes the oil to flow down one of the conduits 22, 24. The initial position of valve member 36 determines which one of the conduits 22, 24 the oil flows through. If the valve member 36 is initially in the position shown in FIG. 2, oil will flow through the second conduit 24, through chamber 34, between sealing member 40 and valve seat 44, and out through conduit 28. When oil flows in this path, the flow of oil between valve member 40 and valve seat 44 will tend to drive valve member 36 towards the position shown in FIG. 3. When sealing member 40 contacts valve seat 44 the flow of oil through conduit 24 is suddenly cut off. This creates a “water hammer” within conduit 24. The water hammer creates a very high pressure pulse which propagates through conduit 24 from the cavitation valve 26 toward the plenum 20. In general, a water hammer is a pressure surge that can arise in a pumping system pumping a fluid that undergoes an abrupt change in its rate of flow. An abrupt change of flow can be caused by a pump starting or stopping and also the opening or closing of valves such as when sealing member 40 contacts valve seat 44. These abrupt changes can cause all or part of a flowing water column in a pipe (conduit 24) to undergo a momentum change. This change can produce a shock wave that travels back and forth between the barrier that created it and a secondary barrier. A water hammer conserves the energy of the previously moving water column by turning the water column velocity energy into high pressure energy. Since fluids have a low compressibility, the resulting pressure energy can be very high. The water hammer phenomenon is well understood by those of ordinary skill in the art. As discussed earlier, a high pressure pulse created by a water hammer creates microbubbles of gas which implode to further raise the temperature of the oil which results in the cracking of the oil into a lower weight oil with a lower viscosity than the original heavy oil.

At the same time as valve member 36 moves to close sealing member 40 against valve seat 44, sealing member 38 moves away from valve seat 42. This permits oil to flow from the first conduit 22 through cavitation valve 26 to output conduit 28. In the meantime, the high pressure pulse which has been propagating upstream in the second conduit 24 eventually reaches plenum 20. At this point, some oil from second conduit 24 spills into plenum 20 and a corresponding low pressure pulse begins to propagate from plenum 20 toward the cavitation valve 26 along the second conduit 24. When this low pressure pulse reaches chamber 34, it tends to draw valve member 36 back down into the position shown in FIG. 2. This tendency is augmented by the tendency of oil flowing between sealing member 38 and valve seat 42 to move valve member 36 in the same direction.

The sudden closure of sealing member 38 against valve seat 42 causes a water hammer pulse to be propagated upstream in the first conduit 22. It can be appreciated that valve member 36 will reciprocate back and forth, alternately closing the fluid path from conduits 22 and 24. As previously mentioned, in the preferred embodiment of system 10 this frequency is generally between 10-100 hertz. Each time valve member 36 allows such an oil path to be opened and re-closed, a new water hammer pressure pulse (e.g., high pressure pulse) is generated. The frequency with which these pressure pulses occur is determined primarily by the lengths of conduits 22 and 24, which are preferably equal in length.

The system 10 of upgrading heavy oil in FIG. 1 is reconfigurable. The system 10 may, for example, be configured to upgrade heavy oil by hydrocracking, deasphalting, or visbreaking the heavy oil. These processes can be achieved in liquid/gas, liquid/liquid, liquid/slurry, and liquid/slurry/gas reactions. The preferred (second) embodiment for upgrading heavy oil can be implemented in at least five different configurations. A first configuration for upgrading heavy oil by hydrocracking is shown in FIGS. 4 and 11A. A second configuration for upgrading heavy oil by deasphalting is shown in FIGS. 5 and 11B. Another configuration of upgrading heavy oil by deasphalting is shown as a third configuration in FIG. 6. A fourth configuration for upgrading heavy oil by visbreaking is shown in FIGS. 7 and 11C. Another configuration of upgrading heavy oil by visbreaking is shown as a fifth configuration in FIG. 8. The modular nature of these configurations is discussed next and other details of these configurations are discussed later.

As mentioned earlier, the system 10 is shown mounted on a truck 1101 as a first unit 1102, a second unit 1104 and a third unit 1106. These units are mounted on corresponding skids 1103, 1105 and 1107. The first unit 1102 may include a pump, a venturi, a mixer, and a heat exchanger. These detailed components are not shown because they are not necessary to show how the system 10 can be reconfigured in FIGS. 11A-C; however, these components are shown in detailed drawings discussed later. The second unit 1104 may include the heat exchanger and a furnace. Unit 1106 may include a tower separator and an overhead separator.

Some line (e.g., pipe) connections are common between the three units 1102, 1104 and 1106 whether the system 10 is in the first, second, third, fourth or fifth configuration. These connections are generally made after the truck 1101 arrives at the jobsite or after the units 1102, 1104 and 1106 are offloaded from the truck 1101. For example, an input line 1108 is attached to the first unit 1102 and connected to a tank of heavy oil located at the jobsite. The pump in the first unit 1102 pumps the oil from the tank into the first unit 1102. Another line 1110 connects the venturi in the first unit 1102 to the heat exchanger in the second unit 1104. Line 1111 provides oil from the heat exchanger in the second unit 1104 to the tower separator in the third unit 1106.

In the first configuration for upgrading heavy oil by hydrocracking shown in FIG. 11A, an additional line 1130 is added for adding recycled hydrogen from the third unit 1106 to the venturi in the first unit 1102.

In the second configuration for upgrading heavy oil, the heavy oil is upgraded by deasphalting as shown in FIG. 11B. In this figure, line 1142 allows for the addition of condensates from the overhead separator in the third unit 1106 to be added to oil in a line pressurized by the pump in the first unit 1102. For example, a condensate stream of C₄ to C₈ can be added through line 1142. Line 1144 in the second configuration allows for the addition of hydrocarbon gases from the overhead separator in the third unit 1106 to heavy oil in the venturi in the first unit 1102. In the third configuration, heavy oil is also upgraded by deasphalting in a system where the heavy is oil is upgraded in a two step process. First, a gaseous stream is mixed with the heavy oil and this mixture is cracked. Next, recovered condensates are mixed with the cracked oil to re-crack this mixture in a second stage of the third configuration to produce upgraded oil.

In the fourth configuration, the heavy oil is upgraded by visbreaking as shown in FIG. 11C. In this figure, line 1150 allows for the addition of carbon dioxide, CO₂, to the heavy oil in the venturi in the first unit 1102. Line 1152 also allows flue gases to be fed back from the furnace in the second unit 1104 to the heavy oil in the venturi in the first unit 1102. In the fifth configuration heavy oil is also upgraded by visbreaking. In this configuration, the heavy is oil is mixed with steam prior to coking and this mixture is then cracked.

In general, key components such as the heater 2, reaction chamber 4 and other elements remain the same between the hydrocracking, visbreaking and deasphalting configurations of cracking heavy oil. However, feedback paths within the system 10 may change between the different configurations. Additionally, the mixing of the heavy oil with material such as hydrogen, a catalyst, a solvent, CO₂, and other materials may change depending on the process the system 10 is configured to use to upgrade heavy oil. However, as previously mentioned, the system 10 of FIG. 1 has a small footprint so these modifications can easily be made when reconfiguring the system 10 between upgrading processes. Additionally, the computer controller 1120 can assist in reconfiguring the system 10 to upgrade oil by a different process. For example, the computer can select a temperature for heater 2 and a pressure for the reaction chamber 4 based on the configurations of the system 10. These configurations and these processes will now be described in greater detail.

The details of the first configuration of the preferred (second) embodiment for upgrading heavy oil by hydrocracking the oil are shown as a system 400 in FIG. 4. In general, the system 400 upgrades heavy oil in a hydrocracking configuration by mixing hydrogen and a catalyst to the heavy oil and then cracking this heated oil in a cavitation valve using high pressure pulses. The hydrocracking reactions are controlled by a set of variables such as: catalyst addition, hydrogen addition, furnace outlet temperature and controlled pressure at the cavitation valve. If the operation is too severe, the resulting product becomes unstable and forms undesirable polymerisation products. The mild cracked mixture is cooled and separated into three streams: the overhead stream, the upgraded oil stream and the catalyst/bottoms steam. The overhead fraction is separated into gaseous and condensate streams. The gaseous stream supplies an external fuel gas system from which fuel gas is produced. The condensate stream is fed back and added to the upgraded oil stream.

In more detail, the system 400 begins the hydrocracking of heavy oil by feeding heavy oil in tank 401 through line 402 to pump 403. The pump 403 pressurizes the heavy oil up to 1500 psi through line 404. The system 400 adds a mixture of liquid catalyst and bottoms that is pumped through line 431 to the heavy oil pumped through line 404. The system 400 transports this mixture through a venturi 406 to create a vacuum. The vacuum makes the mixture susceptible to the addition of hydrogen to the mixture. The system 400 next adds recycled hydrogen received through line 432 at the venturi 406. The system 400 transports the mixture of heavy oil, liquid catalyst, bottoms and hydrogen through line 407 to a static mixer vessel 408. After the mixture is mixed by the static mixer vessel 408, the mixture exits through line 409 and is pre-heated in heat exchanger 410 to about degrees 375 Celsius. The system 400 transports the pre-heated mixture to a furnace 412 through line 411 for further heating up to degrees about 450 Celsius. A high pressure, high temperature mixture exits the furnace 412 through line 413 and enters a distributor 414 (e.g., the plenum 20 discussed above). The distributor 414 has two parallel lines 415, 416 (e.g., the first conduit 22 and the second conduit 24, discussed above) which provide for a continuous flow through cavitation valve 417. At the cavitation valve 417, a regulator controls the valve aperture to control the induced cavitation pressure, which can be as high as 6000 psi at frequencies of 10 to 100 Hz. The oscillation of pressure generated by the cavitation valve 417 forms microbubbles which grow and implode causing a substantial localized rise in temperature for a short period of time at the interface between the microbubbles, the catalyst, the hydrogen and the heavy oil. This substantial rise in temperature promotes the formation of free radicals and chemical reactions. These chemical reactions change the molecular structure of the heavy oil by breaking large molecules into smaller molecules to reduce the viscosity and the specific gravity of the heavy oil.

The products of reaction exit the cavitation valve 417 through line 418 and are fed back and cooled at heat exchanger 410 by the pre-heating stream 409 before the pre-heating stream enters the furnace 412. The system 400 transports the cooled products from the heat exchanger 410 through line 419 to a separator 420. At the separator 420, these products are flashed to generate three streams: an overhead stream, a catalyst/bottoms stream and an upgraded oil stream.

The upgraded oil stream in line 427 is the primary product output by the system 400. This product has a reduced viscosity and reduced gravity that is more suited for transportation in pipes than the unprocessed heavy oil. The upgraded oil stream quality is controlled by four variables: the addition of liquid catalyst to the heavy oil, the addition of hydrogen, furnace outlet temperature and control of induced cavitation pressure.

The overhead stream exits the separator 420 through line 421 and the system 400 will cool this stream in a second heat exchanger 422. This cooled stream is transported by the system 400 through line 423 to an overhead separator 424. The system 400 transports the non-condensable hydrocarbon gases from the overhead separator 424 through line 425 to a fuel gas system. Condensate from the overhead separator 424 in line 426 is added to the upgrading oil in line 427 and pumped to storage through line 428.

The catalyst/bottoms stream exits the separator 420 through line 429 and is pressurized at pump 430. These pressurized catalyst/bottoms slurry travel through line 431 and are recycled by mixing them with unprocessed heavy oil. The catalyst/bottoms stream is controlled by two variables: furnace outlet temperature and API density meter.

The configuration of system 400 in a mode of operation as shown in FIG. 4 provides a wide range of operating variables not available in traditional hydrocracking and hydrotreating processes. For example, the configuration of FIG. 4 provides the ability to control online catalyst addition and concentration, the ability to control online operating pressures by controlling induced cavitation pressures as well as the ability to control temperature for chemical reactions with a low residence time. This allows the system 400 of FIG. 4 to respond rapidly to desired operating conditions.

FIG. 5 illustrates in more detail a system 500 that implements the preferred (second) embodiment in the second configuration of upgrading heavy oil by deasphalting the oil. In general, system 500 deasphalts heavy oil by mixing condensates, non-condensables and heavy oil. This mixture is heated at a controlled induced cavitation pressure to promote mild cracking and precipitation of asphaltenes from the heavy oil.

The system 500 is configured to store heavy oil in tank 501 and to heat the heavy oil by a coil 502 to a temperature of about 35 to 45 degrees Celsius to make it pumpable. Heavy oil is typically defined as oil with an API gravity of less than 20. The heavy oil flows from tank 501 through line 503 to pump 504. The pump 504 pressurizes the heavy oil to 60 psi and pumps the pressurized oil through line 505. The system 500 next mixes the pressurized oil in line 505 with condensates in line 546. For example, a condensate stream of C₄ to C₈ can be added through line 546 and mixed with the heavy oil of line 505. This mixture is then fed through a venturi 507 to create a vacuum. The vacuum allows for non-condensates to be added and mixed at the venturi 507. For example, hydrocarbon gases can be added from line 545 through the venturi 507.

The system 500 then sends the output of the venturi 507 to a static mixer 509 via line 508. The mixture of heavy oil, condensate and hydrocarbon gases are fed through line 510 to high pressure pump 511 to raise the oil pressure up to about 1500 psi. The high pressure oil is then pumped through line 512 to heat exchanger 513 where the mixture is pre-heated to about 275 degrees Celsius. The system 500 sends the high pressure, pre-heated mixture through line 514 to a furnace 515 where its temperature is raised up to about 450 degrees Celsius. The high pressure, heated mixture exits the furnace 515 and travels through line 516 to a plenum 517. Two parallel lines 518 and 519 carry the mixture to a cavitation valve 520 where the oil is cracked with high pressure differentials.

At the cavitation valve 520, a regulator controls the valve aperture to control the induced cavitation pressure, which can be as high as 6000 psi at frequencies of 10 to 100 Hz. An oscillating pressure generated by the cavitation valve 520 forms microbubbles which grow and implode. The implosions cause a substantial localized rise in temperature for a short period of time at the interface between the microbubbles and heavy oil. This substantial rise in temperature promotes the formation of free radicals and chemical reactions. These chemical reactions change the molecular structure of the heavy oil reducing the viscosity and the specific gravity.

The oil products of reaction exit the cavitation valve 520 and the system 500 transports these products through line 521 to a reboiler 522 where they are cooled. The cooled oil exits the reboiler 522 through line 523 and proceeds to a tower separator 524. The oil is flashed in the tower separator 524 to generate three streams: a gaseous stream, a liquid stream and a bottoms fraction stream.

The system 500 is configured to mix the liquid stream that exits the tower separator 524 through line 541 with condensate received from line 540. This mixture is a deasphalted output from the system 500 that is ready for pipeline transmission or may be sent to storage. The system 500 pressurizes the bottoms fraction after it exits tower separator 524 through line 525 with a pump 526. The system 500 is configured to transport the pressurized bottoms fraction through line 527 and into line 528 for feedback into the reboiler 522 to control the asphalt concentration. Another portion of the bottoms fraction is fed back into the heat exchanger 513 through line 529 so that it is cooled by pre-heating the heavy oil mixture. This cooled stream exits heat exchanger 513 through line 30 and proceeds to asphalt storage.

The gaseous stream exits the tower separator 524 through line 532 and is cooled in heat exchanger 533. The cooled stream exits the heat exchanger through line 534 and enters an overhead separator 535. Non-condensable hydrocarbon gases exit the overhead separator 535 through line 543 and are fed back to the venturi 507 via supply line 545. The system 500 feeds a portion of the non-condensable hydrocarbon gases from the overhead separator 535 through line 544 to a fuel gas system for conversion to combustion fuel.

A condensate stream travels from overhead separator 535 through line 536 to a pump 537 where it is pressurized. The pressurized output in supply line 538 supplies three streams (lines): line 546 for feedback into the deasphalting portion of the system 500, line 539 for reflux into the tower separator 524, and line 540 as an addition to the deasphalted oil product in line 541 that is ready for pipeline transmission through line 542.

FIG. 6 illustrates the preferred (second) embodiment in the third configuration for upgrading heavy oil. The third configuration operates as a system 600 that upgrades heavy oil by another variation of deasphalting the heavy oil. In the third configuration, the system 600 deasphalts heavy oil in a two step cracking process. The system 600 is configured to crack heated heavy oil mixed with a gaseous stream with a first cavitation valve. The mildly cracked heavy oil is cooled and fed into separators and a separated gaseous stream is cooled and routed to a fuel gas system. The system 600 pumps and mixes recovered condensates of an overhead separator with the bottoms fractions of a separation tower. This mixture is again heated and then cracked by a second cavitation valve. The system 600 is configured with a second group of separators to separate the cracked heavy oil into deasphalted oil ready for pipeline transportation or storage and into a gaseous stream to supply a fuel gas system.

In more detail the system 600 is configured to feed heavy oil from tank 699 through line 601 into a pump 602. The pump 602 pressurizes the heavy oil in line 603 up to about 1500 psi. The system 600 sends this pressurized heavy oil through a venturi 604 where hydrocarbon gases C₁ to C₃ are added from line 625 and then the oil flows through line 605 into a mixer vessel 606. The system 600 transports the mixture of heavy oil and hydrocarbon gases through line 607 to a heat exchanger 608 for pre-heating up to about 375 degrees Celsius. The heated mixture then travels through line 609 into a furnace 610 for further heating up to about 450 degrees Celsius.

The system 600 transports the cracked products of reaction through line 616 back to the heat exchanger 608 for cooling by pre-heating stream 607. These cooled products of the reaction stream exit the heat exchanger 608 through line 617 and proceed to a tower separator 618. The products of reaction are flashed at the tower separator 618 to generate two streams: a gaseous stream and a bottom's stream.

The system 600 transports the gaseous stream from the tower separator 618 through line 620 to a heat exchanger 621 for cooling. This cooled gaseous stream enters an overhead separator 623 through line 622. The non-condensable hydrocarbon gases exit the overhead separator 623 through line 624 and split into two streams. The first stream travels through line 625 and is mixed with the heavy oil at the venturi 604. The second stream travels through line 626 to a fuel gas system. The condensable hydrocarbons travel from the overhead separator 623, through line 627 and enter a pump 628. The pressurized hydrocarbons exit the pump 628 through line 629 which splits into three streams. The first stream travels through line 630 and is fed back to the tower separator 618 as a reflux stream to control the overhead temperature of the tower separator 618. A second stream of C₄ to C₈ condensate travels through line 631 and is injected into a second venturi 635 which initiates preparing the oil for further cracking at second cavitation valve 646. A third stream exits from pump 629 through line 674 and is added to the deasphalted oil product in line 666 that is ready for storage.

The system 600 sends the bottoms fraction of the tower separator 618 through line 632 to pump 633. The pressurized bottoms fraction travels through line 634 to the second venturi 635. As previously mentioned, at the second venturi 635 a condensate of C₄ to C₈ is added to the bottoms fraction. The system transports this mixture through line 636 to a mixer vessel 637. The mixture is pre-heated in another heat exchanger 639 up to about 375 degrees Celsius. The heated mixture enters a furnace 641 via line 640 where it is heated up to about 450 degrees Celsius. The high pressure/high temperature mixture exits the furnace 641 through line 642 and enters a plenum 643 of the second cavitation valve 646. The plenum 643 transports the mixture over two parallel lines 644 and 645 to provide for a continuous flow through the second cavitation valve 646.

The system 600 controls the cavitation valve 646 to create pressure pulses in a way similar to the cavitation valves discussed earlier. The system 600 transports cracked products of the second cavitation valve 646 through line 647 to a reboiler 648 where they are cooled. The cooled products exit the reboiler 648 through line 649 and proceed to a tower separator 650. The products of reaction are flashed in the separation tower 650 to generate three streams: a gaseous stream, a liquid stream and a bottoms fraction.

The system 600 transports the gaseous stream from the separation tower 650 through line 651 to a heat exchanger 652. The gaseous stream is cooled at the heat exchanger 652 before it passes through line 654 to enter an overhead separator 655.

The liquid stream (e.g., upgraded deasphalted oil) exits tower separator 650 through line 663 and proceeds to pump 664. The system 600 combines the pumped and upgraded deasphalted oil in line 665 with condensate stream 662. The combined mixture of upgraded oil is then output through line 666 ready for pipeline transportation or for storage.

The system 600 transports the bottoms fraction to the tower separator 650 through line 667 to pressuring pump 668. This stream exits the pump 668 on line 263, which splits into line 670 and line 672. Line 670 feeds reboiler 648 to control the asphalt concentration. The oil in line 672 is cooled by pre-heating the heavy oil condensate stream mixture at heat exchanger 639. The cooled stream exits heat exchanger 639 through line 673 and proceeds to asphalt storage.

The system 600 transports the non-condensable hydrocarbon gases from the overhead separator 655 on line 657 to a fuel gas system (external the system of FIG. 6) for producing combustion fuel. Condensate exits the overhead separator 655 through line 656 which feeds a pump 659. The pressurized condensate travels through line 660 to supply line 661 and supply line 662. The condensate in line 661 supplies reflux to the separation tower 650. The condensate in line 662 is added to the deasphalted oil product before it is transported over a pipeline or stored.

In summary, the system 600 of FIG. 6 provides another configuration for allowing for deasphalting at different operating conditions in two stages. In the first stage heavy oil is cracked with a gaseous solvent. In the second stage, the oil is further cracked using a mixture of liquid solvents. The system 600 controls the composition of both gaseous and liquid solvents by controlling process operating conditions. This process provides several variables to allow an operator of the system 600 to meet a deasphalted product specification.

The fourth configuration of the preferred (second) embodiment is shown in more detail in FIG. 7. In the fourth configuration, the preferred embodiment is configured as a system 700. The system 700 visbreaks the heavy oil to reduce the viscosity and density of the heavy oil. Oil with reduced viscosity and density can be transported by pipeline from production fields to refineries for further processing. In general, the system 700 upgrades heavy oil by mixing a stream of heavy hydrocarbon oil with CO₂, flue gases and/or steam. The CO₂ and flue gases aid in the cracking of large heavy oil molecules into smaller molecules. This mixture is heated under pressure and passed through a cavitation valve to induce cavitation at a controlled pressure and frequency to reduce the viscosity and density of the heavy hydrocarbon oil. This system 700 of visbreaking heavy oil produces fuel gas and a product with lower viscosity and a lower density than the original heavy oil.

In more detail, the system 700 begins the visbreaking of heavy oil by pumping oil from tank 701 through line 702 with pump 703. The pump 703 pressurizes the heavy oil up to about 1500 psi through line 704. The pressurized oil is passed through a venturi 705. Flue gases from line 734 and/or CO₂ from line 735 are added from line 736 to the heavy oil at venturi 705. The system 700 next feeds the heavy oil mixture from venturi 705 through line 706 into a mixer vessel 707. The mixture travels through line 708 to a heat exchanger 709. The system 700 pre-heats the mixture in a heat exchanger 709 to up to about 375 degrees Celsius. A furnace 711 further heats the heavy oil mixture up to about 450 degrees Celsius.

Next, the high pressure/high temperature mixture exits the furnace 711 through line 712 and enters a plenum 713. The system feeds this mixture from the plenum 713 through two parallel lines 714 and 715 to a cavitation valve 716. The two parallel lines 714 and 715 provide a continuous flow supply of the oil mixture to the cavitation valve 716. As discussed earlier, the cavitation valve 716 creates high pressure pulses that can be at frequencies of 10 to 100 Hz. At the cavitation valve 716 a regulator controls a cavitation valve aperture to control the induced cavitation pressure, which can be as high as 6000 psi. The oscillation in pressure generated by the cavitation valve 716 forms microbubbles which grow and implode causing a substantial localized rise in temperature for a short period of time at the interface between the microbubbles and heavy oil. This substantial rise in temperature promotes the formation of free radicals and chemical reactions. These chemical reactions change the molecular structure of the heavy oil, reducing the viscosity and the specific gravity of the heavy oil. Additionally, a system 700 with a cavitation valve 716 can take advantage of the acidic properties of flue gases and the solvent properties of CO₂ when visbreaking heavy oil to enhance the mild cracking conditions created by the cavitation valve 716.

The system 700 next transports products of the reaction in the cavitation valve 716 through line 717 back to the heat exchanger 709 to pre-heat heavy oil in line 708 that has not yet been heated. The cooled products next exit the heat exchanger 709 and travel through line 718 so that different hydrocarbon products can be separated. A separator tower 719 receives the cool products from line 718 and generates a gaseous stream and a bottoms stream. The bottoms stream travels through line 730 and is fed to pump 731 where it is pressurized. The pressurized bottoms stream in line 732 is added to condensate in line 729 to generate upgraded oil in line 733 that is ready for pipeline transportation. Alternatively, the upgraded oil in line 733 can be sent to a storage tank.

The gaseous stream exits the separator tower 719 through line 720. This stream is cooled in a second heat exchanger 721 and is passed through line 722 to an overhead separator 723. Non-condensable hydrocarbon gases exit the overhead separator 723 through line 725 and may be provided to a fuel gas system. A second stream of the overhead separator 723, the condensate stream in line 724, is pumped by a pump 726. This stream is pumped through line 727. Line 727 feeds line 728 that supplies a reflux stream to control the tower separator's 719 overhead temperature. Line 727 also feeds 729 that is added to line 732. As previously mentioned, the upgraded oil in line 733 is a combined product of lines 729 and 732 that is ready for pipeline transportation.

The preferred (second) embodiment may also be converted to the fifth configuration of the preferred embodiment as shown in FIG. 8. In the fifth configuration, the preferred embodiment operates as a system 800 to upgrade heavy oil by another version of visbreaking heavy oil. This variation of visbreaking uses steam as a precursor to coking. Adding steam to the heavy oil improves the mild cracking conditions within a cavitation valve. The system 800 begins to upgrade heavy oil by heating it in tank 701 by with a coil 835 to a temperature of about 35 to 45 degrees Celsius. The heated heavy oil proceeds to venturi 705 similar to the venturi in FIG. 7. Instead of adding CO₂ or flue gases as in system 700, steam is added from line 834 to the heavy oil in the venturi 705. The system 800 is configured to process the heavy oil and steam from here on in a way similar to the system 700 of FIG. 7.

Example methods may be better appreciated with reference to flow diagrams. While for purposes of simplicity of explanation, the illustrated methodologies are shown and described as a series of blocks, it is to be appreciated that the methodologies are not limited by the order of the blocks, as some blocks can occur in different orders and/or concurrently with other blocks from that shown and described. Moreover, less than all the illustrated blocks may be required to implement an example methodology. Blocks may be combined or separated into multiple components. Furthermore, additional and/or alternative methodologies can employ additional, not illustrated blocks.

FIG. 9 illustrates a method 900 of upgrading heavy oil by visbreaking. The method 900 mixes raw heavy oil with flue gases, CO₂ and/or steam, at 902, to produce mixed heavy oil. This mixture is heated, at 904, to produce heated heavy oil. High pressure pulses are created in the heated heavy oil, at 906, to crack the heated heavy oil. This produces oil with a lower viscosity than the heavy oil. The high pressure pulses create microscopic bubbles in the heated heavy oil. The microscopic bubbles expand and implode to form radicals and cleavage of bonds to facilitate cracking the heated heavy oil. As discussed earlier, a cavitation valve can be used to create the high pressure pulses. For example, a hammer member within a cavitation valve may oscillate back and forth between two positions to create the high pressure pulses. The high pressure pulses can be created based, at least in part, on a piston sliding back and forth in the cavitation valve.

FIG. 10 illustrates a method 1000 associated with upgrading heavy oil that is a variation of method 900 in FIG. 9. The method 1000 begins by pumping raw heavy oil at a pressure of about 1500 pounds per square inch (psi), at 1002. Similar to method 900, the raw heavy oil is mixed with flue gases, CO₂ and/or steam, at 1004, to produce mixed heavy oil. This mixture is preheated, at 1006. The preheating may occur in a preheater where it is preheated to about 375 degrees Celsius. The preheated heavy oil is then heated in a furnace, at 1008. The furnace may heat the heavy oil to about 450 degrees Celsius. High pressure pulses are created in the heated heavy oil, at 1010, to crack the heated heavy oil.

The cracked oil is separated into an overhead stream, a bottoms stream and an upgraded oil stream, at 1012. The high pressure pulses can be created by a cavitation valve so that the high pressure pulses change pressure from about −2000 pounds per square inch gauge (psig) to about 4000 psig and the high pressure pulses can have a frequency in a range of 10-100 hertz. The residency time of the heated heavy oil in the cavitation valve can be less than one second, two seconds or another value.

In the foregoing description, certain terms have been used for brevity, clearness, and understanding. No unnecessary limitations are to be implied therefrom beyond the requirement of the prior art because such terms are used for descriptive purposes and are intended to be broadly construed. Therefore, the invention is not limited to the specific details, the representative embodiments, and illustrative examples shown and described. Thus, this application is intended to embrace alterations, modifications, and variations that fall within the scope of the appended claims.

Moreover, the description and illustration of the invention is an example and the invention is not limited to the exact details shown or described. References to “the preferred embodiment”, “an embodiment”, “one example”, “an example”, and so on, indicate that the embodiment(s) or example(s) so described may include a particular feature, structure, characteristic, property, element, or limitation, but that not every embodiment or example necessarily includes that particular feature, structure, characteristic, property, element or limitation. Furthermore, repeated use of the phrase “in the preferred embodiment” does not necessarily refer to the same embodiment, though it may.

Claims

1. A method of upgrading heavy oil by visbreaking comprising:

mixing raw heavy oil with at least one of the group of: flue gases, CO2 and steam to produce a mixed heavy oil;

heating the mixed heavy oil to produce heated heavy oil; and

creating high pressure pulses in the heated heavy oil to crack the heated heavy oil to produce cracked oil with a lower viscosity than the heavy oil.

2. The method of claim 1 wherein the step of heating the mixed heavy oil further comprises:

heating the mixed heavy oil in a furnace to about 450 degrees Celsius.

3. The method of claim 2 further comprising:

preheating the mixed heavy oil in a preheater to about 375 degrees Celsius prior to the step of heating the mixed heavy oil in the furnace.

4. The method of claim 1 wherein the step of mixing raw heavy oil is performed in a mixer vessel.

5. The method of claim 1 wherein the step of mixing raw heavy oil further comprises:

creating a vacuum with a venturi, wherein the step of mixing is performed in the venturi.

6. The method of claim 1 further comprising:

separating the cracked oil into an overhead stream, a bottoms stream and an upgraded oil stream.

7. The method of claim 1 further comprising:

pumping the raw heavy oil at a pressure of about 1500 pounds per square inch (psi); and wherein the step of mixing is performed in a venturi.

8. The method of claim 1 wherein the step of creating high pressure pulses further comprises:

creating the high pressure pulses in a cavitation valve.

9. The method of claim 8, wherein the step of the creating high pressure pulses is generated by fluid hammering action in the cavitation valve.

10. The method of claim 8 wherein the residency time of the heated heavy oil in the cavitation valve is less than three seconds.

11. The method of claim 8 wherein the residency time of the heated heavy oil in the cavitation valve is less than one second.

12. The method of claim 1 further comprising:

creating the high pressure pulses that change pressure from about −2000 pounds per square inch gauge (psig) to about 4000 psig, wherein the high pressure pulses have a frequency in a range of 10-100 hertz.

13. A system for upgrading heavy oil by visbreaking comprising:

a mixer to mix at least one of the group of: flue gases, CO2 and steam with raw heavy oil to produce mixed heavy oil; a furnace to heat the mixed heavy oil to create heated heavy oil; and

a reaction chamber configured to receive the heated heavy oil and to generate a controlled cavitation with high pressure differentials to facilitate the local cracking of the heated heavy oil to produce cracked oil that has a lower viscosity than the heated heavy oil.

14. The system of claim 13, further comprising:

a heat exchanger to preheat the mixed heavy oil before it enters the furnace, wherein the cracked oil is circulated through the heat exchanger to preheat the mixed heavy oil.

15. The system of claim 13, further comprising:

a separator configured to separate the cracked oil into an overhead stream, a bottoms stream and an upgraded oil stream.

16. The system of claim 13, further comprising:

a heat exchanger to cool the overhead stream to produce a cool overhead stream; and

an overhead separator to separate the cool overhead stream into a non-condensable hydrocarbon gases and a condensate stream.

17. The system of claim 13, wherein the mixer is a venturi that creates a vacuum.

18. The system of claim 13 wherein the reaction chamber is a cavitation valve.

19. The system of claim 18, further comprising:

a piston within the cavitation valve, wherein the high pressure differentials are created, at least in part, by a back-and-forth action of the piston.

20. The system of claim 13, wherein the residency time of the heated heavy oil in the reaction chamber is less than three seconds.

21. The system of claim 13, wherein the residency time of the heated heavy oil in the reaction chamber is less than one second.

22. The system of claim 13, wherein the heater is configured to heat the heavy oil to about 450 degrees Celsius, and wherein the reaction chamber is configured to create pressure differentials between −2000 psig and 4000 psig and between 10 to 100 hertz.