METHOD FOR TREATING HEAVY CRUDE OIL

FIELD OF INVENTION

The present invention relates to a method for deasphalting oils containing asphaltenes (such as heavy crude oil (HCO) , bitumen, and oil refinery residues) using solvents and acoustic sound energy resulting in an upgraded higher value synthetic crude oil which may be further upgraded by chemical or biological/chemical processes.

BACKGROUND OF INVENTION

It is well known that solvent deasphalting can be used to upgrade heavy crude oil (HCO) , including bitumen, to a synthetic crude oil (SCO) via enhancement of its chemical and physical properties such as:

• increased API gravity • decreased viscosity

• decreased nickel content

• decreased vanadium content

• decreased sulphur content

API gravities above 19 and viscosities below 350 centistokes are particularly desirable for purposes of product pipelining .

Nickel contamination in oil refineries can come from two (2) sources: corrosion of stainless steel (e.g. via the presence of hydrogen chloride or naphthenic acids) or nickel organometallic compounds (e.g. porphyrins) in the asphaltene portion of bitumen. Nickel, a hydrogen scavenger, causes

catalyst fouling via coke formation due to dehydrogenation of alkanes to olefins in refinery catalytic crackers. Therefore SCO containing less nickel is more valuable.

Vanadium contamination in oil refineries can come from vanadium organometallic compounds (e.g. porphyrins) in the asphaltene portion of bitumen. Vanadium destroys catalytic cracker catalysts by altering their crystal structure to non- catalytic forms. Therefore SCO containing less vanadium is more valuable.

U.S. Patents No. 4,941,134 and 5,005,773 issued to Nyberg et al . describe a sonic reactor for the transmission of energy into fluid mediums using a "resonating bar" or probe.

U.S. Patent No. 6,357,526 (Abdel-Halim and Subramanian) describes "flashing" of light ends from HCO followed by solvent deasphalting of the flasher residue.

Canadian patent 2,549,358 (Boakye) describes a chemical and biological upgrading process for heavy oils which includes solvent deasphalting as a primary step. Although the process achieves high quality SCO output, the deasphalting step is prohibitively expensive and therefore not commercially viable due to excessive solvent requirements e.g. 10:1 preferred solvent to oil volume ratio (see page 5 section [0016]) and deasphalter processing times e.g. 2 to 3 hours (see page 2 section [0005] ) .

The process of deasphalting has two purposes: to initiate upgrading of the HCO, by an average quantity of 4-5 API, as per prior technical evaluation as well as to remove a substantial quantity of sulphur from the HCO to the precipitated, insoluble asphaltene fraction. Deasphalting

involves the solubilization of non-asphaltenes and the precipitation of asphaltenes, i.e. molecules insoluble in the deasphalting solvent.

U.S. Patent No. 3,779,902 (Mitchell and Speight) shows, in Example 1, the relative deasphalting capability of a series of non-polar alkane solvents on Athabasca bitumen at 1:1 solvent to bitumen weight ratio. The solvent-bitumen mixtures were shaken vigorously for 5-10 minutes at 0.5 hour intervals for approximately 8 hours. At the end of the 8 hour reaction period, the fractions were separated by decantation followed by filtration, with light suction of the solvent-bitumen solution. The following Table 1 shows degree of asphaltene precipitation in weight % for each of the solvents: Table 1

Deasphalting was high for non-cyclic alkanes and improved as the molecular weight of the alkane was reduced. Deasphalting was efficient based on the low solvent : bitumen ratio, however, deasphalting was extremely slow (i.e. 8 hours) .

Prior art deasphalting of heavy crude oil and refinery residues suffers from the following problems alone or in combination:

• excessive solvent to heavy crude oil/residue ratios

• excessive processing times

SUMMARY OF THE INVENTION

The present invention is a method for converting heavy crude oil (HCO) , such as bitumen, or oil refinery residues to a higher grade synthetic crude oil (SCO) or refinery output via separation of the SCO from asphaltenes. Asphaltenes are defined as the part of the HCO or refinery residue precipitated by addition of a low-boiling paraffin solvent such as n-pentane. The SCO can be used as is or further upgraded via chemical and/or biological processing e.g. Canadian patent 2,549,358.

According to the invention, there is provided a method for treating heavy crude oil (HCO) which includes the steps of combining the HCO with an alkane containing non-polar solvent to form an HCO/solvent mixture, sonicating this mixture at audio frequency to precipitate asphaltenes from the HCO/solvent mixture, and separating the precipitated asphaltenes from the HCO/solvent mixture.

Preferably, vacuum filtration is used to remove . precipitated asphaltenes from the HCO/solvent mixture.

Distillation may be used to remove solvent from the HCO/solvent mixture after removal of precipitated asphaltenes so as to create a deasphalted and solvent free synthetic crude oil (SCO) .

The alkane containing solvent may include pentane, hexane or iso-octane.

The deasphalted HCO/solvent mixture may advantageously be used as the feedstock for a chemical and/or biological oil upgrading process.

The chemical and/or biological .process uses enzyme sources and one or more oxidants in the presence of an acid.

The enzyme source may be soyabean husk and the enzyme, peroxidase .

The acid may be acetic acid.

The oxidant may be hydrogen peroxide combined with iron oxide .

The deasphalting time is preferably 2 minutes (120 seconds) or less.

The deasphalting time may be 60 seconds.

The deasphalting solvent: HCO weight ratio may be less than or equal to 3.5.

The deasphalting solvent: HCO weight ratio may be 1.16 or less .

The deasphalting solvent: HCO weight ratio may be 0.91.

The method exhibits improved solvent deasphalting, without excessive blending and dilution, by virtue of much faster deasphalting at low solvent to oil ratios, including

separation of asphaltenes from deasphalted oil (in contrast to prior art methods) . More particularly, this improved deasphalting is achieved by applying low-frequency, high amplitude acoustic energy to the HCO-solvent process stream (referred to as "sonication" of the HCO-solvent mixture) followed by separation of precipitated solvent insolubles (asphaltenes) via filtration, centrifugation, settling, or other appropriate technique. The method results in a SCO product that meets pipeline specifications in terms of API gravity and viscosity.

The current invention is a method for simplified, accelerated deasphalting of HCO' s with non-polar solvents, under low frequency acoustic sonication at an audio frequency that is well below the ultrasonic range (ultrasound frequency range commences at approximately 20,000 Hertz (Hz) ) .

"Audio frequency" refers to a range of 16Hz to 20,000Hz, however, in the preferred embodiment of the invention the sonic mixing takes place at a frequency range of 30Hz-5, 000Hz, or more preferably, in a range of lOOHz-1, 000Hz .

Such sonication devices come in two preferred types: sonicating probes in direct contact with fluids; and fluid containing vessels where the sonication is applied indirectly to the fluids via the vessel (e.g. component #44 on United States patent 5,005,773) . Sonication devices can be of any type which can generate the desired acoustic frequency, high amplitude and sufficient energy density to the process fluids at an industrial scale. The preferred sonication device would achieve a high energy efficiency by using a balanced dynamic system operating at its natural resonance frequency to sonicate the fluid containing vessel (e.g. see Nyberg United States patents 4,941,134 and 5,005,773 component #44 where

such vessel is mounted axially to the resonating member but in the absence of grinding media) .

In particular, non-polar, non-cyclic, low molecular weight alkane solvents and their associated analogs such as propane, pentane, hexane, heptane and iso-octane are used.

"Sonication" and "low frequency acoustic sonication" refer to methods whereby a material is subjected to low frequency acoustic vibration. Devices for producing such vibration, "sonicators", are disclosed in, for example, U.S. Patents No. 4,941,134 and 5,005,773 (Nyberg et al.) . Unlike ultrasonic devices, these low frequency sonic reactors are reducible to large scale commercial practice (e.g. ≥20 kilowatt sonicator modules) and can achieve HCO deasphalting at low solvent :HCO doses (with ultra-low residence times in the sonicator (e.g. less than 120 seconds) .

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and- advantages will be apparent from the following detailed description, given by way of example, of a preferred embodiment taken in conjunction with the accompanying drawings, wherein:

Figure 1 is a Heavy Oil Deasphalting Process Flow Diagram;

Figure 2 is a Heavy Oil Upgrading Process Flow Diagram;

Figure 3 is a SIMDIST graph for Upgraded and Raw oil showing boiling point temperature versus percentage of oil distilled at that temperature for heavy oil from South Western Texas;

Figure 4 is a SIMDIST graph for heavy oil from Lloydminster;

Figure 5 is a SIMDIST graph for heavy oil from Albania; and

Figure 6 is a SIMDIST graph for American Oil Refinery Residue .

DETAILED DESCRIPTION OF THE INVENTION

The process is comprised of the following key unit operations:

• Intense agitation of the HCO/solvent mixture using audio frequency sonic energy "sonication", resulting in efficient separation of asphaltenes from the HCO/solvent mixture. Such sonication devices come in two preferred types: sonicating probes in direct contact with fluids; and sonication of fluid containing vessels;

• Separation of the HCO from the asphaltene solids via physical separation e.g. decantation, filtration, centrifugation, etc. • Optional biological and/or chemical oxidation of asphaltene stripped HCO/solvent mixture to create and SCO/solvent mixture.

• Removal of solvent from the asphaltene stripped HCO/solvent mixture to create a solvent free SCO. • Recycling of the solvent for further processing of raw HCO.

The sonication device reactor typically involves the conversion of electric power, via sequentially activated magnets, to produce vibrational energy. As an example one sonication device used an electro-magnetic drive system to resonate a three tonne solid steel bar. Vibrational energy from the bar is transmitted to the attached to the fluid containing sonic reaction chambers (vessels containing the HCO-solvent mixture) and through which fluid materials can be pumped and be subjected to very intense audio frequency agitation ("sonication") . The vigorous sonication is used in the current process to enhance solvent extraction of the non- asphaltene fraction from the HCO through enhanced mass

transfer as a result of the sonication and secondary effects such as cavitation.

The sonic reactors are large (beyond bench and lab scale) low frequency sonication reactors that have sufficient processing capacity for commercial applications. The sonic reactors are readily transportable and require no anchoring once on site.

Heat generation testwork indicates specific energy inputs for the 20 kW to 50 kW sonic reactor ranging up to 90 kW/m ³ of reactor volume (450 Horsepower/1, 000 US gallons) . This range of power input is at least one to two orders of magnitude (10 to 100 times) greater than is achieved by energy intensive industrial mixing systems such as flotation cells or standard agitation systems.

The energy and fluid dynamic conditions and energy intensity produced by sonication devices, and in particular by the sonic reactors, is advantageous for chemical process operations. Sonication enhances process reactions by causing intense mixing and other fluid dynamic effects such that sonication improves the selectivity or efficiency of the desired chemical or physical reaction.

The following non-limiting examples illustrate the effectiveness of the invention:

Example 1 Upgrading Oil from a Texas Oil Source

The oil came from a heavy oil field located in Southwestern Texas. Fifty grams of the Southwestern Texas HCO was blended with 175 grams of iso-octane solvent (225 grams total) for sonic deasphalting in a baffled 1.7 litre stainless

steel reaction chamber. The deasphalting occurred at 25 kW power applied continuously for 120 seconds in batch mode in a 1.7 lire sonic reaction chamber. Subsequently the deasphalted material was separated through direct vacuum filtration. Optionally, the subsequent deasphalted oil was oxidized via the prior art described by Boakye (Canadian patent #2,549,358) utilizing acetic acid, hydrogen peroxide, peroxidase enzyme source (i.e. soyabean husk) and iron oxide. The oxidation reaction was quenched through absorption of generated polar compounds and sulfur compounds by passing the deasphalted HCO/solvent/reagent reaction product through a natural clay and activated carbon mixture that removes excess and/or unconsumed oxidation reagents.

The solvent is recovered by atmospheric distillation at temperatures sufficient to evaporate the solvent. Any solvent recovery system may be used and persons skilled in the art may specify equipment based on recovery and cost considerations.

Table 2. Sample Candidate Oil Balance (Run 081018E-1) , normalized to 1 barrel of oil:

Table 3

IBP = Initial Boiling Point ( ⁰ C)

Referring to Fig. 3, the SIMDIST shows the simulated distillation via gas chromatography of upgraded and raw oil from Southwestern, Texas. The upper curve corresponds to raw- crude and the lower one to upgraded crude. This is the same for Figs. 4 to 6. If one arbitrarily chooses a value of 20 on the x-axis then 20 % of the upgraded oil is distilled at 260 ⁰ C while 20 % of the raw oil is distilled at 310 ⁰ C. Oil value tends to increase as the boiling points of its components decrease .

Example 2 Upgrading Oil from a Canadian Oil Source

Oil from a heavy oil field located near Lloydminster, Alberta, Canada was tested.

Fifty grams of Lloydminster HCO was blended with 175 grams of iso-octane solvent (225 grams total) for sonic deasphalting in a baffled 1.7 litre stainless steel reaction chamber. The deasphalting occurred at 25 kW power applied

continuously for 120 seconds in batch mode. After the deasphalted material was separated through direct vacuum filtration, the subsequent deasphalted oil was oxidized via the prior art described by Boakye (Canadian patent #2,549,358) utilizing acetic acid, hydrogen peroxide, peroxidase enzyme source (i.e. soyabean husk) and iron oxide. The oxidation reaction was quenched through absorption of generated polar compounds and sulfur compounds by passing the deasphalted HCO/solvent/reagent reaction product through a natural clay and activated carbon mixture.

Table 4

Sample Candidate Oil Balance (Run 081017E-1) :

Table 5

IBP = Initial Boiling Point (°C)

Referring to Fig. 4, this SIMDIST graph corresponds to Example 2.

Example 3

Upgrading Oil from an Albanian Oil Source

The oil from a heavy oil field located in Albania was tested next.

Fifty grams of Albanian HCO was blended with 175 grams of iso-octane solvent (225 grams total) for sonic deasphalting in a baffled 1.7 litre stainless steel reaction chamber. The deasphalting occurred at 25 kW power applied continuously for 120 seconds in batch mode. After the deasphalted material was separated through direct vacuum filtration, the subsequent deasphalted oil was oxidized through the prior art described by Boakye (Canadian patent #2,549,358) utilizing acetic acid, hydrogen peroxide, peroxidase enzyme source (i.e. soyabean husk) and iron oxide. The oxidation reaction was quenched through absorption of generated polar compounds and sulfur

compounds by passing the deasphalted HCO/solvent/reagent reaction product through a natural clay and activated carbon mixture that remove all excess and/or unconsumed oxidation reagents .

Table 6

Sample Candidate Oil Balance (Run 081119E-1) :

Table 7

IBP = Initial Boiling Point ("C)

Referring to Figure 5 this SIMDIST refers to the heavy oil from Albania

Example 4

The next test sample was Processed American oil refinery residue. The oil refinery residue ("asphalt extender tank bottoms") came from an oil refinery manufacturing refinery gas fuels, fuel additives, lubricants and anticorrosive materials.

Fifty grams of refinery residue was blended with 175 grams of n-pentane solvent for sonic deasphalting in a baffled 1.7 litre stainless steel reaction chamber. The methodology involved the addition of 50 grams of the selected heavy oil indicated for each example to 175 grams of solvent (225 grams total) for sonic deasphalting. The deasphalting occurred at 25 kW power applied continuously for 120 seconds in batch mode. After the deasphalted material was separated through direct vacuum filtration, the subsequent deasphalted oil was oxidized via the prior art described by Boakye (Canadian patent #2,549,358) utilizing acetic acid, hydrogen peroxide,

peroxidase enzyme source (i.e. soyabean husk) and iron oxide. The oxidation reaction was quenched through absorption of generated polar compounds and sulfur compounds by passing the deasphalted HCO/solvent/reagent reaction product through a natural clay and activated carbon mixture that remove all excess and/or unconsumed oxidation reagents.

Table 8

Sample Candidate Oil Balance (Run 080829V-1) :

Inputs Mass (kg) Outputs Mass (kg)

Crude Oil 154 Upgraded Oil 120

Solvent 620 Asphaltenes 34

Biological Catalyst 9 Solvent 589

Oxidizing Reagents 18 Solvent Loss 31

Chemical Catalyst 9 Reagent + Catalyst 18

Adsorbent Agents 40 Reagent + Catalyst Loss 18

Adsorbent Agents 40

TOTAL 850 TOTAL 769

Crude Oil Volume 1 bbl Upgraded Oil Volume 0.87 bbl

Table 9

Analytical Parameters Raw Upgraded Change (%) Method

Total Acid Number (TAN) (mg KOH/g) 3.19 0.26 -91. 8 ASTM D664

API gravity 14.5 + 124 .1 ( ⁰ API, @15°C) 32.5 ASTM D4052

Density (kg/irv ³ , @15°C) 969.0 862.5 -11. 0 ASTM D4052

Nickel (μg/g) 12.2 <1.0 -91. 8 ASTM D5185

Vanadium (μg/g) 23.8 1.7 -92. 9 ASTM D5185

Sulfur (mass %) 1.18 0.62 -47. 5 ASTM D4294

SIMDIST (by GC) IBP=130.8 IBP=85.5 (IBP ¹ to 72O ⁰ C) See plot See plot - ASTM D7169

IBP = Initial Boiling Point ( ⁰ C) Referring to Fig. 6, this SIMDIST corresponds to Example 4.

Example 5

Pentane Solvent Deasphalting Only Using Acoustic Sonication Only

The methodology involved mixing 619.4 g heavy crude oil (HCO) from Alberta with 716.7 g of solvent (n-pentane) (1,336 grams total), and therefore a solvent:oil weight ratio of

1.16, in a baffled 1.7 litre stainless steel reaction chamber. Acoustic energy was applied for 60 seconds at 40 kW continuously in batch mode followed by direct insoluble asphaltenes fraction filtration and atmospheric pressure distillation for solvent removal. The mass yield on the deasphalted oil was 85.3% of the HCO feedstock.

Table 10

Example 6 Hexane Solvent Deasphalting Only Using Acoustic Sonication Only

The methodology involved mixing to a solvent: oil ratio of 1.09 by adding 690.9 g heavy crude oil (HCO) from Alberta with 631.6 g of solvent (n-hexane) (1,323 grams total) and therefore a solvent:oil weight ratio of 0.91, in a baffled 1.7 litre stainless steel reaction chamber. Acoustic energy was applied for 60 seconds at 40 kW continuously in batch mode followed by direct insoluble asphaltenes fraction filtration and atmospheric pressure distillation for solvent removal. The mass yield on deasphalted oil was 95.5% of the HCO feedstock.

Table 11

Accordingly, while this invention has been described with reference to illustrative embodiments, this description is not intended to be construed in a limiting sense, for instance longer residence times and higher solvent ratios could be used. Various modifications of the illustrative embodiments, as well as other embodiments of the invention, will be apparent to persons skilled in the art upon reference to this description. It is therefore contemplated that the appended claims will cover any such modifications or embodiments as fall within the scope of the invention.