Purification of impure oil by centrifugation

Abstract

The present invention relates to methods, apparatus and systems of purifying an impure oil by subjecting the impure oil to a disk stack centrifuge at a rate greater than about 80 gallons per minute, to obtain a purified oil. In particular, the purified oil can have an impurity content of less than about 0.3% by weight, or greater than about 2 fold less than the impurity content of the impure oil. In one embodiment, the present invention utilizes a particular type of dick stack centrifuge referred to as a “disk type nozzle centrifuge”.

Description

BACKGROUND OF THE INVENTION

The oil industry refines crude oil into several types of products, such as gasoline, diesel fuel and home heating oil. Crude oil contains a number of impurities that are removed during the refinement process. Also, certain refinement processes can produce byproducts that contaminate the oil. Some of these byproducts include inorganic materials such as ash, catfines or fines. The presence of such impurities in the oil causes damage to equipment that uses the oil (e.g., engines, furnaces, etc.). Unfortunately, the end user bears the cost in having to repair or replace this equipment.

As such, a need exists to develop a refinement or purification process that reduces the amount of impurities in oil. In particular, a need exists to reduce such impurities while refining large amounts of crude oil quickly and efficiently.

SUMMARY OF THE INVENTION

The present invention pertains to methods for purifying large quantities of oil in an efficient manner. The methods of the present invention allow for the removal of impurities or inorganic material including ash, catfines, and/or fines. The removal of such material results in better quality end products such as gasoline, diesel fuel and home heating oil, which, in turn, advantageously reduces the damage done to equipment associated with these end products. The present invention provides for improved combustion with less impurities.

In particular, the present invention relates to methods for purifying an impure oil, or removing impurities, inorganic material or ash from an impure oil, at a rate of about 80 Gallons Per Minute (GPM) (303 Liters Per Minute (LPM)) or greater by subjecting the impure oil to a centrifuge referred to as a “disk stack centrifuge” to thereby obtain a purified oil. The rate of oil passing through the centrifuge generally can range from about 80 GPM (303 LPM) to about 350 GPM (1324.9 LPM). The bowl speed of the centrifuge, in one aspect of the invention, is greater than about 1000 Revolutions Per Minute (RPM), or preferably between about 1000 RPM and about 4000 RPM. In one embodiment, the impure oil prior to centrifugation has an impurity content, an inorganic material content and/or ash content of about 0.1% by weight or greater (e.g., in a range between about 0.1% by weight and about 2.1% by weight, preferably between about 0.5% and about 0.7% by weight, or more preferably about 0.6% by weight). After centrifugation, the purified oil has an impurity content, an inorganic material content or ash content less than that prior to centrifugation. One embodiment relates to having a purified oil with an impurity content, an inorganic material content or ash content greater than about 2 fold less (e.g.,about 3× less, about 4× less, about 5× less, about 6× less, or about 7× less), or between about 2 fold less and about 7.5 fold less, than that of the impure oil. Another aspect of the invention includes purifying the impure oil so that the purified oil has impurity content, inorganic material content, and/or ash content of less than about 0.3% by weight (e.g., in a range between about 0.01% and about 0.3% by weight, and preferably between about 0.15% and about 0.05% by weight). One aspect of the invention includes having a purified oil that has an aluminum content of less than about 0.03% by weight (or less than about 300 parts per million (PPM), e.g., between about 50 and about 300 PPM), and/or a silicon content of less than about 0.04% by weight (or less than about 400 PPM), e.g., between about 50 and about 400 PPM. Note that 1% by weight equals 10,000 PPM. In one embodiment, the invention includes heating the impure oil to a temperature between about 79° C. (about 175° F.) and about 135° C. (about 275° F.), prior to subjecting the impure oil to the disk stack centrifuge. Also, an aspect of the invention includes filtering the impure oil e.g., to remove particles that are greater than about 80 microns (e.g., 90 microns, 100 microns, 110 microns, or 120 microns), prior to subjecting the impure oil to the disk stack centrifuge. One embodiment of the invention includes using a particular type of disk stack centrifuge referred to as a “disk type nozzle centrifuge” or a “nozzle centrifuge.”

Another embodiment of the invention relates to methods for purifying an impure oil having an impurity content, inorganic material content and/or ash content of greater than about 0.1%, as described herein, by subjecting the impure oil to a disk stack centrifuge at a rate greater than about 80 GPM, to thereby obtain a two products, a purified oil and a slurry. The purified oil has an impurity content, inorganic materials content or ash content of less than that of the impure oil, and the slurry has an impurity content, inorganic materials content or ash content greater than that of the impure oil. In particular, the purified oil has an impurity content, an inorganic material or ash content greater than about 2 fold less (e.g.,about 3× less, about 4× less, about 5× less, about 6× less, about 7× less), or between about 2 fold less and about 7.5 fold less, than that of the impure oil. The invention, in another aspect, includes purifying the impure oil so that the purified oil has impurity content, inorganic material content and/or ash content of less than about 0.3% by weight (e.g., in a range between about 0.01% and about 0.3% by weight, preferably between about 0.15% and 0.05% by weight). The invention results, in another embodinfent, with a slurry that has an impurity content, inorganic materials content and/or ash content in a range between about 1.0% and about 6.0% by weight. An advantage of this embodiment is that the slurry, even with its high impurity content, is recycled into purified oil having an impurity content and/or ash content of less than about 0.3% by weight. Recycling the slurry, in one embodiment, involves subjecting the slurry to a second centrifuge at a rate of between about 10 GPM (38 LPM) and about 150 GPM (568 LPM). Several types of centrifuges can be used in the recycling process as the second centrifuge. An example of a second centrifuge includes, but is not limited to, a decanter centrifuge. The second centrifuge produces a petroleum product having an impurity content, inorganic materials content and/or ash content of less than about 2.5% by weight (e.g., between about 2.5% and about 0.05% by weight, preferably about 0.8% by weight). In an embodiment, the slurry is mixed by one or more mixers prior to entering the second centrifuge. After being subjected to the second centrifuge, the recycling process further includes subjecting the petroleum product, one or more times, to a disk stack centrifuge, as described above, at a rate greater than about 80 GPM, to thereby obtain a purified oil having an impurity content, inorganic materials content and/or ash content of less than about 0.3% by weight. Additionally, the present invention relates to the purified oil, as obtained by the methods described herein.

Furthermore, the present invention pertains to an apparatus or system for purifying impure oil. The apparatus includes a combination of one or more of the following: a first tank for providing impure oil, a pump, a disk stack centrifuge that excretes a centrate and a slurry; a heat exchanger that heats the oil to a temperature in a range between about 79° C. and about 135° C.; and a second tank for receiving the centrate. The impure oil is processed in the centrifuge at a rate greater than about 80 GPM, as further described herein. The apparatus can further comprise a filter that removes particles that are greater than about 80 microns, and also a second heat exchanger that chills the centrate to a temperature less than about 93° C. (about 200° F.), or between about 93° C. (about 200° F.) and about 66° C. (about 150° F.), and preferably to about 82 ° C. (about 1 80° F.).

In another aspect; the invention relates to apparatus or system for purifying impure oil that comprises one or more of the following: a first tank for providing oil, a pump, a first centrifuge (e.g., a disk stack centrifuge that excretes a centrate and a slurry), a second centrifuge that receives the slurry from the first centrifuge, a recirulation means for moving the centrate from the second centrifuge to the first centrifuge, and a second tank, connected to the first centrifuge, for receiving the centrate for the first centrifuge. The impure oil is processed in the centrifuge at a rate greater than about 80 GPM, as further described herein. The second centrifuge can be e.g., a decanter centrifuge.

Advantages of the present invention include the ability to produce a cleaner oil which reduces wear on engines components, burners, etc. This advantage reduces cost to the end users since such equipment will generally need less repair and/or replacement. The present invention advantageously also reduces the cost and quantity of the hazardous waste generated by the end user due to the use of such products. Since the process allows for efficient purification of oil in large quantities, a further advantage of the present invention is the ability to increase profit by selling oil with less impurities at a higher price. The present invention advantageously further reduces costs associated with storage and maintenance of crude oil because the present invention allows the oil to be processed quickly and efficiently, rather than being stored for prolonged periods of time (e.g., for a month). As a result, processing the oil with the present invention also reduces the risk of environmental leakage associated with oil storage tanks.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention.

FIG. 1 is a schematic representation showing one embodiment of an oil purification process.

FIG. 2 is a cross-sectional view of a nozzle centrifuge.

FIG. 3 is a schematic representation showing another embodiment of the oil purification process of the present invention.

FIG. 4 is a schematic representation showing sample maximum flow conditions for feed, centrate, recycled oil, wash liquid (e.g., cutter stock) and concentrate (e.g., slurry) from the disk stack centrifuge for one embodiment of the purification process of the present invention. Abbreviations: gpm—gallons per minute; bb/hr—barrels per hour; bb/24hr—barrels per 24 hours; wt. %—amount in percent weight; lbs/hr—pounds per hour; rpm—revolutions per minute; G's—Gravitational force; deg F—degrees Fahrenheit; Hp—house power; API—specific gravity; CP—viscosity.

FIG. 5 is a schematic representation showing another embodiment of the oil purification process.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to methods for refining and/or purifying an impure oil (e.g., crude oil or clarified oil) so that better quality end products, such as gasoline and heating oil, can be made. The present invention involves removing certain impurities that can cause damage to equipment that uses the oil. The methods described herein allow for quick and efficient purification of large quantities of oil, and include subjecting oil in need of purification (e.g., oil having certain impurities) to a disk stack centrifuge at high flow rates to result in a purified oil.

Purifying oil or refining oil refers to a process of decreasing, removing or separating away one or more impurities from the oil. The phrases, “purifying oil” or “refining oil” are used interchangeably herein. The process of the present invention purifies the oil so that the impurity content, inorganic materials content or ash content is decreased or lessened, as compared to the respective content prior to centrifugation, as described herein. In particular, purifying oil or removing impurities, inorganic material or ash from the oil is used herein to mean to take away, partially or completely, one or more impurities, inorganic materials (e.g., inorganic elements), or ash, respectively.

The impure oil that is purified by the methods described herein can be a crude oil or a clarified oil. Examples of impure oil include Cat Bottoms, Bayway—Cat cracked clarified oil, Bayway—Cat Cracker Bottoms, Bayway—Cat Tar, Bayway—Clarified oil, Bayway—Cycle Gas oil, Bayway—Slurry oil, Cat, Cat Crack Clarified oil (East Coast), Trainer Decanted oil, and wood river Cat Crk Clarified oil. Crude oil is a mixture of several types of chemicals and compounds, primarily hydrocarbons. Crude oil can be obtained in any number of ways, such as drilling or from a well. One or more pre-purification steps can be conducted prior to subjecting impure oil to the stack centrifuge. For example, crude oil can be clarified by a process referred to catalytic cracking in which crude oil is broken down or “cracked” into simpler hydrocarbon compounds at the molecular level by means of extreme heat, pressure, and/or exposure to a chemical catalyst. Essentially, the process changes the long-chain hydrocarbon molecules into shorter-chain compounds.

The present invention purifies impure oil, including crude oil or clarified oil, having an impurity content, inorganic material content and/or ash content of greater than about 0.1% by weight or greater (e.g., in a range between about 0.1% and about 2.1% by weight, and preferably between about 0.5% by weight and about 0.7% by weight). Percent by weight is determined by dividing the weight of the impurity with the overall weight of the oil multiplied by 100%. Impurity content, inorganic material content or ash content can also be measured in Parts Per Million (PPM). Impurity content, inorganic materials content or ash content can be measured using methods known in the art, or those later developed. PPM can be converted to a percent by weight, and viscera, with the following formula: 1% by weight=10,000 PPM.

Consequently, the impurity content refers to a combination of one or more elements, chemical compounds that include such elements, or particles that are not wanted in the impure oil (e.g., sulfur, sodium, silicon, aluminum, vanadium, ash, catfines, fines, and used lubricating or cutter oils), as measured by a percent by weight or in parts per million (PPM). Inorganic material content, measured as a percent by weight or PPM, pertains to one or more non-carbon elements or materials that are not wanted in the impure oil, and includes e.g., sulfur, sodium, silicon, aluminum, vanadium, ash, catfines, or fines. Ash is defined as a certain type of inorganic material or impurity found in oil which cannot burn at the combustion temperature, or can be seen as the residue after all the combustible components have been burned. Essentially, ash, catfines and fines are unwanted inorganic material found in oil, and the three terms are sometimes used interchangeably. More specifically, ash which is generally also measured as a percent by weight, can include, but is not limited to, a combination of one or more of the following, for example: vanadium, aluminum, silicon, sodium, iron oxides, sand, dirt, and used lubricating or cutter oils. Fines (e.g., catalyst fines or iron ore fines) are defined as small particles or powder resulting from the refining process. Catfines are a type of fines derived from spent catalysts from the catalytic cracking process.

The following table is an example of a breakdown of its impurity content, as measured by a percent by weight or PPM, of an impure oil prior to being subjected to centrifugation, as described herein:

TABLE 1
Impurity  Amount
Ash       0.46% weight*
Aluminum, 858 PPM (.0858% weight*)
MDL = 1
Silicon,  1304 PPM (.1304% weight*)
MDL = 1
*Percent by weight = weight of impurity/weight of total volume of oil × 100%

After being subjected to the steps of the present invention, one or more of the elements that comprise the impurity content decreases. The following is an example of the impurity content of a purified oil after being subjected to centrifugation with a nozzle centrifuge.

TABLE 2
Impurity  Amount
Ash       0.09% weight*
Aluminum, 165 PPM (.0165% weight*)
MDL = 1
Silicon,  248 PPM (.0248% weight*)
MDL = 1
*Percent by weight = weight of impurity/weight of total volume of oil × 100%

In one embodiment, the method of the invention is conducted in apparatus g(system) 100, shown in FIG. 1. Apparatus 100 includes tanks 10 and 26 (one for storing the impure oil, and another for receiving the purified oil), pumps 20 and 22 (one for supplying oil to centrifuge and another for supplying the oil to tank 26), heat exchangers 14 and 24 (one for heating the oil and another for chilling the oil), filter 16 and disk stack centrifuge 12.

Tanks 10 and 26 are storage tanks. Tank 10 is used for holding crude petroleum or clarified (e.g., impure oil), and tank 26 is used for storing the purified oil. Tanks 10 and 26 can be constructed, for example, from steel or another suitable material. Generally, the capacity of Tank 10 should be sufficient to supply the apparatus or oil purification system at the proper rate, as further described herein. In other embodiments, a continuous method can be employed, whereby petroleum product is generated from an oil well and employed in the method of the invention continuously, without being held in a storage tank such as tank 10. Similarly, a continuous method can be used to bypass the use of tank 26, wherein the purified oil is deposited directly into a pipeline or the like.

From tank 10, impure oil is directed by pump 20 to heat exchanger 14, where it is heated. The impure oil is pumped by pump 20 at a rate of about 80 GPM (302.8 LPM) or greater. Flow rates that can be employed in the methods of the invention are in the range of between about 80 GPM and about 350 GPM (1324.9 LPM), preferably in the range of between about 180 (681.4 LPM) and about 255 GPM (965.3 LPM). A specific example of a flow rate is about 200 GPM (757.1 LPM). A number of pumps can be used throughout the purification system. Pumps for delivering oil at the specified rate are known in the art and are commercially available. In one embodiment, to supply the centrifuge at above rate, one can use a 4″ valve and a discflow pump (e.g., a Discflow SP Series disc pump, Disc Flo Corporation, Santee, Calif.). This pump has the following characteristics: Hydraulic flow—2-10,000 GPM (0.5-2250 m³/h); pump speeds—up to 3600 RPM; Viscosities—up to 300,000 cPs; temperature—up to 1000° F. (523° C.). Another example of a pump that can be used in the oil purification system of the present invention is a Blackmere paddle pump model No: NP4F, E.I. by DuPont (Wilmington, Del.).

The oil is heated such that it enters the disk stack centrifuge 12 at a temperature in a range about between about 79° C. (about 175° F.) and about 135° C. (about 275° F.) (e.g., between about 90° C. and about 120° C., and preferably between about I 00° C. and 110° C.). Proper oil temperature contributes to efficient centrifugation of the impure oil, and to achieve the desired impurity, inorganic material or ash content. Several methods for heating oil can be used. Methods that are known in the art or later developed can be used for heating the oil in a manner as described herein. Heating the oil involves the following variables: starting temperature of the oil, the rate of oil passing through the heating device, the size of the heating device, and the amount heat emitted by the heating device.

Referring to FIG. 1, the impure oil is heated by directing it, via pump 20, to a heat exchanger. A heat exchanger is a device used to transfer heat to oil passing through it. Examples of heat exchangers that can be used to carry out the present invention include: an air heat exchanger, a fin tube heat exchanger, a block type heat exchanger, a plate heat exchanger, a shell & tube heat exchanger, a spiral heat exchanger, a U-tube heat exchanger, a fin fan heat exchanger, a tube in tube heat exchanger, and others. Suitable heat exchangers are commercially available through several vendors such as Canzler, L. L. C. (Columbia, Md.), Alfa Laval Thermal, Inc.(Richmond, Va.) and Kinetic Engineering Corp. (Houston, Tex.). A specific example of a heat exchanger is the Alfa Laval spiral heat exchanger (Alfa Laval Thermal, Inc.(Richmond, Va.)), and its use is demonstrated in the Exemplification Section. In this section, this spiral heat exchanger, in conjunction with a steam boiler 13, was used to process oil at a rate of about 200 GPM with a starting temperature of about 82.2° C. (180° F.) to heat the oil to a temperature of 104.4° C. (220° F.), suitable for entry into the centrifuge. One can manipulate the variables (e.g., flow rate, input, starting temperature, ending temperature) described herein to achieve the desired temperature. Put another way, these variables can be captured by “Delta T,” the number of BTUs needed to raise the temperature of a known fluid from one temperature to another temperature at a set flow rate. A heat exchanger can have valves, temperature gauges and pressure gauges, or a combination thereof.

Temperature gauges, pressure gauges, sample points, and flow meters are known in the art and can be installed at various points in the purification system. In one embodiment, shown in FIGS. 1 and 3, the Alfa laval spiral heat exchanger has a 4″ valve, temperature gauge and pressure gauge on its suction and discharge. In another embodiment, a sample point was installed at a pressure gauge (not shown in FIG. 1) located between heat exchanger 14 and filter 16. In yet another embodiment, a 4″ turbine style flow meter mounted on the top of a valve is utilized between heat exchanger 14 and filter 16. A suitable flow meter is a EZ-IN® Series BF flowmeter from NuFlo Measurements Systems (Houston, Tex.), and has the following characteristics: flowmeter size—2 inch; linear flow range 40-400 GPM (9.09-90.85 m³/h); Nom. Calibration factor—55 pulses/gallon (14.5 pulses×1000/m³) ; maximum output frequence—365 pulses/sec.

Referring to FIG. 1, from heat exchanger 14, impure oil is directed to filter 16 and is filtered before entering the disk stack centrifuge 12. The oil can be heated before or after filtration. In another embodiment, impure oil is directed to a filter that is located before heat exchanger 14. Thus when filtering is conducted, it takes place before impure oil enters the centrifuge.

In general, a filter that can be used with the present invention is one that can remove particles having a size of about 80 microns or greater (e.g., about 90 microns, about 100 microns, 110 microns). The filter to be used with the present invention removes particles in a range preferably between about 60 microns and about 100 microns. In one application of the invention, an 80 micron filter was used. Types of filters that can be used with the present invention include, but are not limited to, Basket filters, or Pot filters. Such filters should have a sturdy screen that separates particles about 80 microns or greater. Companies from which one can obtain filters include, e.g., puraDYN Filter Technologies Inc. (Boynton Beach, Fla.), and Grotto Filters (Mumbai, INDIA). Filters now known or developed in the future can be used with the present invention so long as they filter particles of the range described herein.

From filter 16, filtered petroleum is directed to disk stack centrifuge 12. A disk stack centrifuge is used in the present invention to purify oil at high rates of speed. An impure oil, having an impurity content, inorganic material content, ash content of greater than 0.1% is subjected to a disk stack centrifuge (e.g., one or more disk stack centrifuges). Subjecting the impure oil to a disk stack centrifuge refers to allowing the oil to entering the centrifuge, e.g., providing piping and pumps to allow the oil to supply the centrifuge from the tank at the proper rate.

Generally, a disk stack centrifuge separates solids from one or more liquid phases using high centrifugal forces. When subject to centrifugal forces, the denser solid particles are pressed outwards against the rotating bowl wall, while the less dense liquid phases form concentric inner layers. The disk stack plates provide additional surface settling area which contributes to the separation process.

A disk stack centrifuge is a centrifuge that has a set of conical disks that spin in a circular motion to separate solids and liquid in the feed (e.g., influent), the product entering the centrifuge. As the conical disks spin, the less dense oil moves upwards and out of the centrifuge through an inlet pipe at the conical tip. This less dense oil that moves through the conical tip is referred to as the “centrate” or as the “purified oil.” The phrase, “purified oil,” is used herein to refer to an oil that has less of one or more impurities (e.g., ash), as compared to the respective impurity prior to centrifugation. Put in another way, purified oil is an oil that is cleaner or purer (i.e., having been separated from one or more impurities) than it was prior to being subjected to the steps of the present invention. In particular, purified oil has an impurity content, an inorganic materials content and/or ash content of less than about 0.3% by weight (e.g., in a range between about 0.01% and about 0.3% by weight, and preferably between about 0.05% and about 0.15% by weight). The purified oil, in another embodiment, can have an impurity content, an inorganic materials content or ash content greater than or equal to about 2 fold less (e.g., greater than about 3 fold less, about 4 fold less, about 5 fold less, about 6 fold less, about 7 fold less, etc.) than the respective content of the impure oil. The content of the purified oil is preferably in a range of between about 2 fold and about 7.5 fold less than that of the impure oil. The feed, in the Exemplification Section, had an ash content of about 0.46%, and after centrifugation with a nozzle centrifuge, the purified oil had an ash content of about 0.09%.

One factor that can impact the impurity content of the purified oil is the impurity content of the impure oil, or the feed oil. A feed oil having a greater amount of impurities can result in a purified oil having more impurities, than one that resulted from a feed oil having an impurity content in lower in the range described herein. For example, an impure oil having an impurity content of about 0.6% by weight could result in a purified oil having an impurity content of about 0.25% by weight, whereas subjecting an impure oil having an impurity content of about 0.2% by weight to the present invention can result in a purified oil having an impurity content, for example, of about 0.08% by weight.

Several types of disk stack centrifuges can be used with the present invention. A preferred disk stack centrifuge used with the present invention is referred to as a “nozzle centrifuge” or “disk type nozzle centrifuge”, and these phrases are used herein interchangeably. A disk type nozzle centrifuge is a disk stack centrifuge with a nozzle attached for the excretion of the slurry, the denser excreted product, as described with reference to FIG. 2, which shows a cross-sectional view of the nozzle centrifuge.

As shown in FIG. 2, the feed containing the liquid and the solids are introduced to the rotating centrifuge bowl from the top via a stationary inlet pipe 50, and is accelerated in the distributor 52 before entering the disc stack 54. It is between the discs that the separation takes place. The liquid phase moves through the disc stack 54 towards the center of the bowl, from where it is discharged over a power-ring 56. The heavier solids phase is collected at the bowl periphery, from where it is continuously discharged through the nozzles 58. Filler pieces 60 can be used to help avoid build-up of the sludge between the nozzles 58. A portion of the concentrated solids discharged through the nozzles 58, can be recirculated into the bowl again through the recirculation inlet pipe 62, a separate distributor 64 and recirculation tubes 66. The bowl can be mounted on a vertical spindle 68, driven by a vertically mounted motor, via a flat belt.

Other examples of disk stack centrifuges that can be used with the present invention include a high speed self ejecting centrifuge, and a high speed solid bowl centrifuge. Disk stack centrifuges that are known in the art, or later developed, can be used to carry out the present invention. One can obtain disk stack centrifuges from various manufacturers such as Alfa Laval (Richmond, Va.), Centrifuge Solutions, Inc (LaPorte, Tex.), or Wesfailia (Ann Arbor, Mich.). One or more disk stack centrifuge can be used alone or in combination, and if used in combination, the same or different types of disk stack centrifuges can be used in parallel or series to increase production and/or efficiency.

Disk type centrifuges have traditionally been used by the dairy industry for skimming, standardization and clarification of milk and whey, by the beverage industry for the clarification of wine and juices, and by other industries for other low rate clarifications. Nozzle type disk centrifuges have been generally used for classification and dewatering of industrial clays, such as kaolin. The present invention is the first application of crude oil refinement at high rates of purification for large quantities of oil.

When used to carry out the steps of the present invention, in one embodiment, the disk stack centrifuge (e.g., the nozzle type centrifuge) processes an impure oil having an impurity content (e.g., an inorganic materials content or ash content) of 0.1% or greater by weight (e.g., between about 0.5% and about 0.7% by weight). The oil enters the centrifuge at a high rate, for example, between about 80 GPM to about 350 GPM (e.g., about 200 GPM). The disks or the bowl speed are moving between about 1000 RPM to about 4000 RPM, for example at about 3500 RPM, to achieve this rate and impurity content of the purified oil. In the Exemplification Section, the nozzle centrifuge had a bowl speed of about 3500 RPM, and the oil entered the centrifuge at a rate of about 200 GPM.

With respect to FIG. 1, the purified oil (e.g., the centrate) is pumped by pump 22 and cooled with heat exchanger 24 prior to entering tank 26. The purified oil is chilled to a temperature that is suitable for storage. The oil is cooled to a temperature less than about 93° C. (less than about 200° F.), e.g., preferably to about 82° C. (about 180° F.). Cooling or chilling the purified oil involves similar variables as for heating the oil: starting temperature of the oil, the rate of oil passing through the cooling device, the size of the cooling device, and the rate of cooling released by the device. One can manipulate the variables (e.g., flow rate, starting temperature) described herein to achieve the desired temperature. Any number of cooling systems, that are known in the art or later developed, can be used to cool the oil, as described herein. Examples of heat exchangers for cooling liquid include cooling water heat exchanger, fixed tubesheet exchanger, floating head removable tubular heat exchanger, spiral heat exchanger, and plate heat exchangers. In particular, the oil, in one embodiment, is cooled with a propeller fin fan used in conjunction with a spiral cooling exchanger (Alfa Laval heat exchanger (Alfa Laval Thermal, Inc.(Richmond, Va.))) to cool the oil to about 82° C. so that it is suitable for being deposited into tank 26. Chilling the oil can be bypassed if the oil is not going to be stored in a tank, e.g., when it is deposited directly into a pipeline. A spiral cooling exchanger is commercially available from a number of manufacturers such as API Heat transfer (Buffalo, N.Y.), Alfa Laval Thermal, Inc.(Richmond, Va.) and Calorplast Wärmetechnik GmbH (Krefeld, Germany).

In one aspect, heat exchanger 24 is provided with an air chiller. The chiller is a large 2 propeller fin fan setup. Water is circulated through the fins and then through the 1065 sq. ft heat exchanger 24 and back to the fins. This enables the apparatus to cool the hot disk centrate to a temperature suitable for pumping into tank 26. The air chiller includes a fin cooler, a circulating pump, a 3″ steel pipe and 3″ tanker hoses.

In another embodiment, during centrifugation, the less dense oil moves through the top of the conical disks, while the more dense oil moves to the bottom of the disk centrifuge and out through the nozzle 58. This more dense oil that exits from the centrifuge (e.g., that moves through the nozzle of a Nozzle type centrifuge) is referred to herein as the “slurry.” An embodiment of the present invention includes subjecting the slurry to a second centrifuge 28. The slurry has an impurity content, inorganic materials content and/or ash content of greater than about 1.0% (e.g., between about 1.0% and about 6.0%). The slurry enters second centrifuge 28 at a flow rate in a range between about 10 GPM and about 150 GPM. (Shown in FIG. 3) The second centrifuge is a centrifuge that separates oil having the above impurity, inorganic material and/or ash contents, and results in a centrate having about 2.5% by weight or less impurity content, inorganic materials content and/or ash content (e.g., between about 0.05% by weight and about 2.5% by weight). The oil can enter the second centrifuge at a temperature in a range between about 75° F. (24° C.) and about 275° F. (135° C.). Several types of centrifuges that are known in the art can be used to carry out this step, and can be obtained from a number manufacturers, such as Centrysis Corp. (Chicago, Ill.), H&H manufacturing (Houston, Tex.), and Flottweg (Germany). One example of such a centrifuge includes the decanter centrifuge. Centrifuges that are known or later developed can also be used to carry out this step so long as the second centrifuge can separate oil having the impurity content, inorganic materials content or ash content described above, and result in a centrate having about 2.5% by weight or less (e.g., about 2.1% by weight less) impurity content, inorganic materials content, and/or ash content. In a particular embodiment, a decanter centrifuge was used to carry out this step, as further described herein. In an example, the influent of the decanter centrifuge had an ash content of about 1.5% by weight, and a centrate of about 0.6% by weight.

Table 3 is one example of an impurity breakdown of oil after being processed by a decanter centrifuge:

TABLE 3
Impurity  Amount
Ash       0.12% weight*
Aluminum, 215 PPM (.0215% weight*)
MDL = 1
Silicon,  328 PPM (.0328% weight*)
MDL = 1
*Percent by weight = weight of impurity/weight of total volume of oil × 100%

The centrate (e.g., petroleum product) is then circulated or recycled so that it is subjected to disk stack centrifuge 12. Piping, pumps and/or tanks are arranged to get the oil to disk stack centrifuge 12. See FIGS. 3 and 5, further discussed below, for examples of this arrangement. This process can be repeated several times until the desired impurity content, inorganic materials content or ash content is achieved.

In particular, FIG. 3 shows another embodiment of the present invention that involves recycling the slurry from disk stack centrifuge 12. In this embodiment, the feed (e.g., the impure oil) comes from the side of tank 10 at the 4′ level (4′ off the ground). The conduits (piping) for directing the feed from tank 10 to other elements of the system shown in FIG. 3 are provided with valves and gauges (e.g., pressure or temperature gauges) as known in the art. For simplicity, theses valves and gauges are not specifically shown in the figures. For example, the conduit connecting tank 10 with pump 20 is provided with a 6″ shell valve and then a 4″ line valve (4″ diameter). After the 4″ valve there is a pressure 1″ blow down and temperature gauge (not shown) before the line drops to pump 20. Feed then flows through a 4″ valve on the discharge of pump 20, past a temperature gauge and into heat exchanger 14. From heat exchanger 14, the feed goes through filter 16, past another pressure gauge, and is fed to disk stack centrifuge 12 through a ¼ turn 4″ valve. If the feed needs to bypass disk stack centrifuge 12 then it flows through a 4″¼ turn valve mounted in the bypass system to a point between pump 22 and a 4″ block valve on second holding tank 18 suction.

Sample maximum flow conditions for the system set-up shown in FIG. 3 can be found in FIG. 4. The flow conditions from the figure include those for the feed, centrate, recycled oil, wash liquid (e.g., cutter stock) and concentrate (e.g., slurry) from the disk stack centrifuge for one embodiment of the invention.

The feed is separated in disk stack centrifuge 12 into 2 phases: purified oil (centrate) and solids laden oil (slurry). The centrate is discharged to second holding tank 18 via an 8″ dump line from disk stack centrifuge 12's housing. The centrate leaves holding second holding tank 18 passes a temperature gauge (not shown), through a 4″ valve to pump 22 (e.g., a 4″ Blackmere paddle variable drive pump). The centrate then passes a temperature gauge (not shown), 4″ block valve, another temperature gauge (not shown), a sample point (not shown in FIG. 3) and is pumped through a heat exchanger 24 preferably coupled with an air chiller, as known in the art. The centrate then flows past a 4″ block valve, sample point (not shown in FIG. 3), a 4″ valve at the bypass header, two more 4″ block valves, additional pressure and temperature gauge (not shown) prior to the 4″ block valve and 4″ check valve at tank 26. If the material is off specification (e.g., has an impurity content, inorganic materials content or ash content more than desired amount), then it can be diverted into the bypass and flow back to tank 10 past a pressure and temperature gauge, a 4″ valve and a 6″ valve at tank 10.

In one aspect, the piping used for the present invention can be 4″ schedule 40 steel, welded flanges,at all connections, steam traced with ½″ copper, Watson McDaniel steam traps, and rock wool insulation that is metal wrapped.

The slurry from disk stack centrifuge 12 can optionally be recirculated back to disk stack centrifuge 12, to second centrifuge 28, as described herein, and/or to fractionation (FRAC) tank 32 or 33, if necessary. The direction of the slurry depends on a number of factors, and can be determined by an operator, automated system, or computerized system. These factors include the temperature of the slurry, the impurity content, inorganic content or ash content of the slurry, the rate of the slurry, the rate of processing of the a centrifuge, etc.

In one aspect, and with respect to FIG. 3, slurry in first holding tank 17 passes out through a 4″ valve, temperature gauge (not shown) and into pump 48, a variable drive mono pump. Pump 48 pushes the slurry down a 4″ insulated steel line to either the mix tank 34, first FRAC tank 32 or second FRAC tank 33. The distinction is made by the operator, or by an automated or computerized system, and is facilitated by to 4″ valves on the discharge manifold of the mono pump. The disk centrate can be by-passed to tank 10. Injection point at tank 10 is 12″ from the floor and is considered a sump line. Centrate can also be pumped by pump 22 to first cutter tank 37 via a 2″ line from P2 to the top of-first cutter tank 37.

Prior to entering second centrifuge 28, the slurry can optionally be mixed by one or more mixers. Mix tank 34 can be insulated and equipped with heating coils. In one example, the slurry was mixed by three vertical mixers prior to entering second centrifuge 28. A variety of mixers can be used, are commercially available and are known in the art. FIG. 3 shows a system where slurry in mix tank 34 is mixed with 3 vertical mixers and held for solids removal in a second centrifuge, a horizontal decanter centrifuge 28. The mix tank 34 is e.g., a 400 bbl. insulated tank with 3 mixers and a dual set of heating coils.

In an embodiment, slurry is pulled from mix tank 34 through a 4″ insulated and steam traced line, past a 4″ block valve and into a variable speed mono pump, pump 44. Slurry is pumped through a 2″ line past a ball style block valve to the feed tube in second centrifuge 28. Slurry that is stored in FRAC tank 32 or 33 is pulled through 4″ insulated and steam traced lines pump 46, a mono pump, into the mix tank 34 for processing.

Second centrifuge 28, in one example, is a horizontal decanter centrifuge. The machine separates the solids from the oil. The oil (centrate) gravity flows to a 4000 gallon receiver tank mounted below the centrifuge stand. The centrate then travels through a 4″ tar hose to a 4″ pump 42. The fluid then passes through 4″ block valve, blow down, temperature and pressure gauge and continues down a 4″ insulated and steam traced line to the bypass line and into Tank 10. There is a 4″ block and 6″ block valve at the base of Tank 10. In one example, using the decanter centrifuge, the influent had an ash content of about 1.5% by weight, and the centrate had an ash content of about 0.6% by weight. Solids are gravity dropped into a roll off container, solids box 30, and disposed of at an approved location.

Lubricant oil, commonly referred to as cutter stock, generally is a light end oil. Cutter stock is added, in some embodiments, where necessary to thin out the feed entering the centrifuge or recirculating line to prevent clogging. This is an optional step. In one example, the cutter stock is stored in cutter tanks 37 and 38 that are connected to the feed line, as shown in FIG. 3.

In one example, cutter and flush oil is pumped from the front of first cutter tank 37 by a 3×2 pump past a pressure gauge, through 1½″ duplex strainer, through a 2″ insulated line, through a 2″¼ turn ball valve and into the disk feed line after the 4″¼ turn valve. This line has a 2″ turbine flow meter. Flush oil, also referred to as “heavy cycle oil,” “PGO” or “light cycle oil,” and is generally used to clean or “flush” out debris after use. Whereas, cutter oil, referred to as “diesel oil” or “heating oil,” is used to thin out the oil or feed. Cutter oil can be used herein to dilute the oil so that the impurity content is in the described range.

In one embodiment shown in FIG. 5, the oil present in the tank 10 is pumped by pump 20 to a heat exchanger 14 where the oil is heated with steam from steam boiler 13. The oil then moves to filter 16 and then to disk stack centrifuge 12. Once processed by the centrifuge 12, the oil can take at least two different paths. It can go to second holding tank 18, and then pump 22 directs the oil to heat exchanger 24 where it is chilled with air chiller 23 before entering tank 10. Alternatively, the oil can move to FRAC Tank 32, where it can then be recirculated. Specifically, oil is directed from FRAC Tank 32 to disk stack centrifuge 12 and then follows the pathway described above. The vapor phase is exhausted from FRAC Tank 32 as known in the art.

A description of preferred embodiments of the invention follows.

Exemplification

Purification of Crude Oil

The apparatus for purifying oil, as depicted in FIG. 3, was used to purify impure oil. The impure oil, after being clarified by a catalyst-cracked process, was pumped from tank 10 at a rate of about 200 GPM (between about 180 and 250 GPM) with pump 20. Pump 20 is a SP Series Disc Pump from Discflow (Disc Flo Corporation, Santee, Calif.). The impure oil having an initial temperature in tank 10 of about 180° F. (82.2° C.) was heated with heat exchanger 14 (Alfa Laval Type I, II or III heat exchanger (Alfa Laval Thermal, Inc.(Richmond, Va.))) to about 220° F. (104.4° C.) and filtered with filter 16, an 80 micron filter (model #: Velcon Model VC 4854003). The heat was generated with a steam boiler. The oil was then subjected to a nozzle centrifuge (Nozzle centrifuge, Alfa Laval Thermal, Inc.(Richmond, Va.), type CHQX 320B-31CGR). The bowl speed of the nozzle centrifuge was about 3500 RPM (between 3000 and about 3700 RPM). The centrate from the nozzle centrifuge was pumped with pump 22 (Blackmere paddle pump model No: NP4F, E.I. by DuPont Wilmington, Del.) and then chilled to temperature in a range between about 180° F. and about 200° F. with heat exchanger 24 (Alfa Laval Type I, II or III heat exchanger (Alfa Laval Thermal, Inc.(Richmond, Va.))), and then deposited into tank 26.

Table 4 below shows the impurity content of the impure oil prior to being subjected to the above process, and the impurity content of the purified oil after undergoing the above process.

TABLE 4
Impurity	Amount of Impure Oil	Amount of Purified Oil
Ash	0.46% weight*	0.09% weight*
Aluminum,	858 PPM** (.0858%	165 PPM** (.0165%
MDL = 1	weight*)	weight*)
Silicon,	1304 PPM** (.1304%	248 PPM** (.0248%
MDL = 1	weight*)	weight*)
*Percent by weight = weight of impurity/weight of total volume of oil × 100%
**1% by weight = 10,000 PPM.

At certain points, as determined by the operator, the slurry was directed to mix tank 34, Frac Tanks 32 or 33, and/or to second centrifuge 30. The second centrifuge used in this instance was a horizontal decanter centrifuge. Once processed, the centrate from the decanter centrifuge was recirculated back to tank 10. The impurity content and ash content of the centrate from the decanter centrifuge can be seen in Table 3 infra. At other times, the centrate from disk stack centrifuge 12 was directly recirculated back to centrifuge 12 for further processing before being moved to tank 26.

Specifications of the Nozzle Centrifuge:

All liquid-welded parts are made in high-grade stainless steel except the nozzles 58 (tungsten carbide), rubber gaskets (nitrite), O rings, PTFE coated Viton, and filler pieces (polyamide 12, filled). A special controlled-torque motor eliminates the need for a clutch between the motor and the centrifuge 12. The spindle 68 is mounted in a cartridge which contains bearings, a lubrication oil bath, an integrated oil pump and an oil clarifier. Disk centrifuge 12 is equipped with sensors for monitoring of bowl speed, vibration level and lubrication oil pressure. The 18 nozzles 58 are tangentially placed in the periphery in order to recover energy from the discharged nozzle flow. The power-rings 56 for the liquid phase discharge are also designed for maximum recovery of energy.

Technical Specification:

	Max. throughput capacity	200	m3/h1)
	Max. solids-handling capacity	72	m3/h2)
	Feed temperature range	0-100°	C.
	Feed inlet pressure required	240	kPa3)
	Installed motor power	135	kW
	Noise level (ISO 3744 or 3746)	79	dB(A)

• • 1) Actual throughput capacity depends on particle sizes, densities, viscosity and required degree of separation.
  • 2) Wet solids.
  • 3) Actual pressure depends on throughput, density and viscosity. The above refers to 200 m³/h of water.
    Due to the process running at 250° F., and water will boil off at 220° F., all flush and safety fluids are of a light oil consistency (e.g., motor oil or hydraulic oil).

Utilities Consumption & Dimension

	Utilities consumption & dimension
	Electric power	70-130	kW1)
	Sealing water	90	dm3/h
	Safety water	22-80	m3/h2)
	Centrifuge with bowl and motor
	Net weight:	4100	kg
	Gross weight:	4400	kg
	Volume:	8	m3

• • 1) Actual consumption depends on throughput, nozzle flow and back pressure.

The above refers to throughput from 100-200 m³/h including a nozzle flow of 20-72 m³/h.

• • 2) The bowl should be filled with liquid at start, stop and normal operation. In case process liquid is not available, safety water should be used. Minimum flow shall be above nozzle flow. The above refers to nozzle sizes from 1.6 to 3.00 mm.

The relevant teachings of all references, journal articles, patents and/or patent applications cited herein are incorporated herein by reference in their entirety.

While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.

Claims

1. A method of purifying an impure oil, wherein the method comprises:

subjecting the impure oil to a disk stack centrifuge at a rate greater than about 303 liters per minute (LPM), to thereby obtain a purified oil.

2. The method of claim 1, wherein the disk stack centrifuge is a disk type nozzle centrifuge.

3. The method of claim 2, wherein the method further comprises filtering the impure oil prior to subjecting said impure oil to the disk type nozzle centrifuge.

4. A method of purifying an impure oil, wherein the method comprises:

a) heating the impure oil; and

b) subjecting the heated, impure oil to a disk stack centrifuge at a rate greater than about 303 LPM, to thereby obtain a purified oil.

5. The method of claim 4, wherein the impure oil is heated to a temperature in a range between about 79° C. and about 135° C.

6. The method of claim 5, wherein the impure oil is filtered to remove particles that are greater than about 80 microns.

7. The method of claim 5, further comprising cooling the purified oil.

8. A method of purifying an impure oil having an impurity content, wherein the method comprises:

subjecting the impure oil to a disk stack centrifuge at a rate greater than about 303 LPM, to thereby obtain a purified oil having an impurity content that is less than the impurity content of the impure oil prior to being subjected to the centrifuge.

9. The method of claim 8, wherein the impure oil has an impurity content of greater than about 0.1% by weight.

10. The method of claim 9, wherein the impure oil has an ash content of greater than about 0.1% by weight.

11. The method of claim 8, wherein the purified oil has an impurity content that is greater than about 2 fold less than the impurity content of the impure oil.

12. A method of purifying an impure oil having an impurity content of greater than about 0.1% by weight, wherein the method comprises:

subjecting the impure oil to a disk stack centrifuge at a rate greater than about 303 LPM, to thereby obtain a purified oil having an impurity content that is greater than about 2 fold less than the impurity content of the impure oil prior to centrifugation.

13. The method of claim 12, wherein the purified oil has an impurity content of less than about 0.3% by weight.

14. The method of claim 13, wherein the purified oil has an ash content of less than about 0.3% by weight.

15. The method of claim 13, wherein the purified oil has an aluminum content of less than about 0.03% by weight.

16. The method of claim 13, wherein the purified oil has a silicon content of less than about 0.04% by weight.

17. A method of purifying an impure oil having an impurity content between about 0.5% by weight and about 0.7% by weight, wherein the method comprises:

subjecting the impure oil to a disk stack centrifuge at a rate greater than about 303 LPM, to thereby obtain a purified oil having an impurity content that is less than the impurity content of the impure oil prior to being subjected to the centrifuge and a slurry having an impurity content that is greater than the impurity content of the impure oil prior to being subjected to the centrifuge.

18. The method of claim 17, wherein the purified oil has an impurity content of less than about 0.3% by weight

19. The method of claim 17, wherein the slurry has an impurity content between about 1.0% and about 6.0% by weight.

20. The method of claim 19, wherein the slurry is recycled into purified oil having an impurity content of less than about 0.3% by weight.

21. The method of claim 20, wherein recycling the slurry comprises:

subjecting the slurry to a second centrifuge at a rate of between about 38 LPM and about 568 LPM, to thereby obtain a petroleum product having an impurity content of less than about 0.3% by weight.

22. The method of claim 21, wherein the method further comprises mixing the slurry with one or more mixers prior to subjecting the slurry to the second centrifuge.

23. The method of claim 22, wherein after subjecting the slurry to a second centrifuge, recycling the slurry further comprises:

subjecting the petroleum product, one or more times, to a disk stack centrifuge at a rate greater than about 303 LPM, to thereby obtain a purified oil having an impurity content of less than about 0.3% by weight.

24. The method of claim 23, wherein the second centrifuge is a decanter centrifuge.

25. A method for removing impurities from an impure oil having an amount of one or more impurities, wherein the method comprises:

subjecting the impure oil to a disk stack centrifuge at a rate greater than about 303 LPM, to thereby obtain an oil having an amount of one or more impurities less than the amount of the one or more impurities prior to centrifugation.

26. A method for removing inorganic material from an impure oil having an inorganic material content between about 0.5% by weight and about 0.7% by weight, wherein the method comprises:

subjecting the impure oil to a disk stack centrifuge at a rate between about 303 LPM and about 1325 LPM, to thereby obtain a purified oil having an inorganic material content greater than about 2 fold less than the inorganic material content of the impure oil prior to centrifugation, and a slurry having an inorganic material content greater than about 2 fold more than the inorganic material content of the impure oil prior to centrifugation.

27. A method for removing ash from an impure oil having an ash content, wherein the method comprises:

subjecting the impure oil to a disk type nozzle centrifuge at a rate between about 303 LPM and about 1325 LPM, to thereby obtain a purified oil having an ash content of less than about 0.3% by weight.

28. The method of claim 27, wherein the method further comprises heating the impure oil prior to subjecting said oil to the disk type nozzle centrifuge.

29. The method of claim 28, wherein the impure oil is heated to between about 79° C. and about 135° C. prior to subjecting said oil to the disk type nozzle centrifuge.

30. An oil purified by the method of claim 1.

31. An apparatus for purifying impure oil that comprises:

a) a first tank for providing impure oil;

b) a pump connected to said tank;

c) a disk stack centrifuge, connected to said pump, wherein the centrifuge excretes a centrate and a slurry;

d) a heat exchanger, located between the centrifuge and the first tank, wherein the heat exchanger heats the oil to a temperature in a range between about 79° C. and about 135° C.; and

e) a second tank, connected to the centrifuge, for receiving the centrate;

wherein the pump provides impure oil to the centrifuge at a rate greater than about 303 LPM.

32. The apparatus of claim 31, further comprises a filter placed between the tank and the centrifuge, wherein the filter removes particles that are greater than about 80 microns.

33. The apparatus of claim 32, further comprises a second heat exchanger, located between the centrifuge and the second tank, wherein the heat exchanger chills the centrate to a temperature in a range between about 93° C. and about 66° C.

34. An apparatus for purifying impure oil that comprises:

a) a first tank for providing oil;

b) a pump connected to said tank;

c) a first centrifuge, connected to said pump, wherein the first centrifuge is a disk stack centrifuge that excretes a centrate and a slurry;

d) a second centrifuge, connected to the first centrifuge so that the second centrifuge receives the slurry from the first centrifuge; wherein the second centrifuge excretes a second centrate and a second slurry;

e) a recirulation means for moving the centrate from the second centrifuge to the first centrifuge; and

f) a second tank, connected to the first centrifuge, for receiving the centrate of the first centrifuge;

wherein the pump provides impure oil to the first centrifuge at a rate greater than about 303 LPM.

35. The apparatus from claim 34, wherein the second centrifuge is a decanter centrifuge.