Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1997-09-11
2001-01-09
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S207000, C524S275000, C524S284000, C524S376000, C524S377000, C524S388000, C524S389000, C524S570000, C524S579000, C524S232000, C523S207000
Reexamination Certificate
active
06172151
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to improvement of flow of hydrocarbons, whether crude oil or refined products, in constricted conduits such as pipelines. The invention finds application both in science and industry, such as the oil industry.
It is well known in the art that certain polymers which are oil soluble may be polymerized in the presence of catalysts to produce high molecular weight, non-crystalline, hydrocarbon soluble polymers by various means. These polymers when dissolved in a hydrocarbon fluid flowing through a conduit greatly reduce turbulent flow and decrease “drag”, thus reducing the amount of horsepower needed to move a given volume of hydrocarbon, or conversely enable greater volumes of fluid to be moved with a given amount of power. In short, these polymers are drag reducers or flow improvers for hydrocarbon fluids.
It is of particular interest to note that the high molecular weight polymers known as drag reducers are used in very dilute solutions ranging up to about 100 parts per million in the hydrocarbon flowing through the conduit. These materials display useful flow characteristics not present in the commonly known crystalline, largely non-hydrocarbon soluble artifact-forming polymers such as polyethylene and polypropylene. In contrast, the hydrocarbon soluble materials of the present invention are noted for their effectiveness as anti-misting agents and drag reducing agents.
As is known in the art, these polymers are susceptible to shear degradation when dissolved in the hydrocarbons in which drag is being reduced. Thus passage through a pump, severe constrictions in a conduit or the like which produce excessive turbulent flow leads to degradation of the polymer, which thereafter has reduced effectiveness. Consequently, it is important that these materials be placed into the flowing hydrocarbon stream in a form which achieves certain desirable features.
First, the polymer should be placed in a form adequate for easy transportation and handling without exotic or unusual equipment, since injection points for the polymer into the flowing hydrocarbon stream can often be at remote and inaccessible locations and require the movement of material to such locations. Secondly, the polymer must be in a form which dissolves rapidly in the hydrocarbon being transported, since the polymers have little drag reducing effect until solubilized into the hydrocarbon stream. Third, the hydrocarbon should also be innocuous to the ultimate purpose of the hydrocarbon fluid. For example, in the case of crude oil flowing through a pipeline, larger amounts of water and contaminants can be tolerated than in finished pipeline products such as diesel fuel, gasoline, and jet fuel which are ultimately destined to be burned in internal combustion engines and turbine engines.
Currently, a number of different commercial approaches are being taken to the problem of preparing, dissolving, transporting and using such drag reducing polymers. In use, the polymers form extremely dilute solutions ranging from about 1 to up to about 100 parts per million polymer and hydrocarbon, yet remain effective in order to receive drag reduction or anti-misting. A common commercial method is to prepare the polymer in dilute solutions in an inert solvent such as kerosene or other solvating material as set forth in Mack, U.S. Pat. No. 4,433,123. In this reference, Mack utilizes a solution of high molecular weight polymer suitable for use as a drag reducing agent when produced by polymerization of alpha olefins in a hydrocarbon solvent. The entire mixture, containing polyolefin, solvent, and catalyst particles is used without separation to form dilute solutions of the polymer in crude oil or finished hydrocarbons. However, one disadvantage of such approach is the use of a solvent, which poses a shipping and handling difficulty and may constitute a hazard. In addition, the product itself forms a gel-like substance which is difficult to introduce into flowing hydrocarbon streams and which becomes extremely viscous and difficult to handle under cold weather temperature conditions, such as when injection into conduits at remote locations is required.
A second, more recent approach is to prepare the polymers as a solid material as described in patents issued to Fenton, U.S. Pat. No. 4,584,244, and to O'Mara, U.S. Pat. Nos. 4,720,397; 4,826,728; and 4,837,249; all of which deal with finely grinding drag reducing polymers to a very small particle size in an inert atmosphere below the glass transition point of the polymers and in the presence of a partitioning agent to form a multi-layered coating which holds the inert atmosphere adjacent to the particle polymers after grinding. The O'Mara patents teach it is mandatory that the reduction to fine particle size be carried out in inert atmosphere utilizing a refrigerant such as liquid nitrogen, and a coating agent while grinding the polymer to an appropriate size, where the coating agent prevents contact of oxygen with the freshly ground polymer particles.
Another recent method is set forth in U.S. Pat. Nos. 5,449,732 and 5,504,132 which deal with preparing a hydrocarbon-soluble drag reducing aqueous suspension or water alcohol suspension. The patents also teach that bulk polymerization of the poly alphaolefins produces a material which is much higher in molecular weight and which provides superior drag reduction as compared to solution polymerization, where molecular weight declines as polymer content increases. That invention solved the problem of producing such high molecular weight alkenes in a commercially satisfactory manner for use in drag reducing materials and further, provided methods for suspending such materials in an aqueous or alcohol/aqueous system.
However, these prior art processes have distinct problems, including clumping, and conversion to a solid in the aqueous suspension in extremely warm temperature conditions. In addition, it is necessary to protect the suspension against freezing in extremely cold temperature conditions.
DESCRIPTION OF THE PRIOR ART
U.S. Pat. No. 5,244,937 deals with stable nonagglomerating aqueous suspensions of oil soluble polymeric friction reducers by suspending such materials in water, together with a water-soluble thickening agent in a mixture of water or water and alcohol. U.S. Pat. Nos. 5,449,732; 5,504,131; and 5,504,132 all deal with a method of preparing ultrahigh molecular weight poly alphaolefins using a bulk polymerization system, cryogrinding in the presence of a partitioning agent, and suspending the resulting mixture in a water or water-alcohol mixture. U.S. Pat. No. 5,539,044 deals with the aqueous suspension of drag reducing polymers together with a surfactant having a hydrophilic/lipophilic balance (HLB) in a particular range to enhance suspension and durability of the suspension.
All of the prior art processes have certain drawbacks and unwanted features, including agglomeration at high temperatures, freezing at cold temperatures, and the necessity of adding an aqueous-based material into a hydrocarbon flowing stream. Such addition is not particularly troublesome in crude oil pipelines in view of the small amount injected, which generally becomes lost in the overall pipeline water content, but such materials can be objectionable in finished product pipelines even at low concentrations, as the presence of water may force the product outside specified limits.
Consequently, it would be a great advantage to provide a nonaqueous suspension of highly effective drag reducing materials for use in hydrocarbons flowing through conduits.
SUMMARY OF THE INVENTION
This invention relates to improving the flow of flowing streams of hydrocarbons, such as petroleum or finished products, in a conduit, such as a pipeline. The present invention also relates to a stable, nonagglomerating nonaqueous suspension suitable for improving flow of hydrocarbons in conduits, particularly finished product hydrocarbons in conduits.
The present invention comprises a method of forming a heat stable, nonaqueous suspen
Johnston Ray L.
Lee Yung N.
Conoco Inc.
Lu Caixia
Schupbach Cortlan R.
Sun Hsiang-ning
Wu David W.
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