WO2003076482A1

WO2003076482A1 - Drag reducing compositions and methods of manufacture and use

Info

Publication number: WO2003076482A1
Application number: PCT/US2003/006745
Authority: WO
Inventors: Brad A. Bucher; Thomas M. Weatherford; Michael J. Monahan
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-03-07
Filing date: 2003-03-04
Publication date: 2003-09-18
Anticipated expiration: 2004-09-07
Also published as: AU2003225677A1

Abstract

A drag reducing composition containing 25 to 70% by weight of a finely divided solid polyolefin friction reducing agent formed from mono olefins containing from to 2 to 30 carbon atoms and 30 to 65% by weight of a fatty acid suspending medium which is a stable liquid in the temperature range of from 10 to 100°C, the composition being formed by finely dividing the solid polyolefin reducing agent to produce a free flowing particulate polyolefin material and suspending the particulate polyolefin material in the suspending medium.

Description

DRAG REDUCING COMPOSITIONS AND METHODS OF MANUFACTURE AND USE

Background of the Invention

Field of the Invention

The present invention relates to compositions for reducing friction in the

flow of hydrocarbons such as crude oil or refined products in conduits such as

pipelines, and to methods for producing and using such compositions.

Description of the Prior Art

The prior art abounds with patents directed to generally non-crystalline,

high molecular weight polyolefin, particularly polyalphaolefins, compositions

which are generally hydrocarbon soluble and, when dissolved in a hydrocarbon

fluid flowing through a conduit, greatly reduce turbulent flow and decrease

"drag." This reduction of drag is important since it reduces the amount of

horsepower needed to move a given volume of hydrocarbon, or conversely

enables greater volumes of fluid to be moved with a given amount of power.

These polyolefin drag reducers display flow enhancing characteristics not

present in commonly known crystalline, largely non-hydrocarbon soluble

polymers such as polyethylene and polypropylene.

It is known that these polyalphaolefin drag reducers are susceptible to

degradation by shear when dissolved in the flowing hydrocarbon in the conduit.

Accordingly, pumps, constrictions in the conduit or the like which result in

excessive turbulent flow lead to degradation of the polymer thereby decreasing its effectiveness. Accordingly, it is necessary that the drag reducing

compositions be introduced into the flowing hydrocarbon stream in a form which

achieves certain desirable features.

First of all, the drag reducing compositions should be in a form that is

easy to transport and handle without special equipment since injection points for

the drag reducing compositions into the flowing hydrocarbon stream are often at

femote and inaccessible locations. Secondly, the polymer must be in a form

which dissolves rapidly in the hydrocarbon stream flowing in the conduit since

the polyalphaolefins have little drag reducing effect until solubilized in the

hydrocarbon stream. Lastly, the drag reducing composition should impart no

deleterious effects to the hydrocarbon. For example, in the case of crude oil

flowing through a pipeline, certain amounts of material and contaminants can be

tolerated unlike in finished pipeline products such as diesel fuel, gasoline and

other hydrocarbon materials resulting from refining operations.

A number of approaches have been taken in the preparation of drag

reducing compositions. For example, because of the effectiveness of the

polyolefins as drag reducers, solutions of the polyalphaolefins ranging from one

up to 100 parts per million can be employed in drag reduction. Accordingly in the

case of a solution produced polyalphaolefin wherein alphaolefin is polymerized in

a dilute solution of an inert solvent such as hexane, isopentane or the like, the

entire mixture containing polyolefin, solvent and catalyst can be used without

separation to form dilute, -solutions of the polymer in the crude oil or finished

hydrocarbon. The disadvantage of this approach is that the inert solvent, which is a hydrocarbon, is flammable and poses shipping and handling problems.

Furthermore, the product generally is a gel-like substance and difficult to

introduce into a flowing hydrocarbon streams. Moreover, in cold weather

conditions the gel becomes extremely viscous and difficult to handle making

injection difficult and often requiring special equipment.

It is also known from U.S. Patent Nos. 4,584,244, 4,720,397, 4,826,728,

fand 4,837,249 to prepare the polyolefin drag reducing polymers as a solid

material and grind the solid polyolefins 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 or coating agent which coats the polymer particles. Thus it is

taught to prepare the fine particle size polyolefins in an inert atmosphere utilizing

a refrigerant such as liquid nitrogen and a coating agent while grinding the

polyolefin polymers to the desired particle size, the coating agent preventing

contact of oxygen with the freshly ground polymer particles and their

reagglomeration at more elevated, usable temperatures.

U.S. Patent No. 6,172,151 is directed to the formation of a drag reducing

composition containing a polyolefin formed from olefins containing from 2 to 30

carbon atoms, the composition comprising a partitioning agent which is a fatty

acid wax which is used during the cyrogrinding of the polymer. The polymer

particles, coated with the fatty acid wax partitioning agent are then suspended in

a suspending agent which is an alcohol containing 14 or less carbon atoms, a

glycol containing 14 or less carbon atoms, mixtures of such alcohols and glycols,

dipropylene glycol methyl ether, tripropylene glycol methyl ether, tetrapropylene giycoi metnyi etner, ethyl ethers ^"and mixtures of such ethers. In any event, the

suspending medium is "substantially free of water, the water level generally being below 1 to 2%".

Summary of the Invention

The present invention provides a substantially water-free drag reducing

composition which exhibits freeze protection, permits a relatively high loading of

active polyolefin in the composition, eliminates agglomeration and heat instability

problems and eliminates concerns about adding water to product pipelines.

In a preferred embodiment of the present invention, there is provided a

drag reducing composition containing from 25 to 70% by weight of a finely

divided solid polyolefin friction reducing agent obtained by polymerizing olefins

containing from 2 to 30 carbon atoms and from 30 to 65% by weight of a fatty

acid suspending medium which is a stable liquid in the temperature range of

from 10° to 100°C.

Another aspect of the invention is a method of forming a drag reducing

composition which comprises finely dividing a solid polyolefin friction reducing

agent formed from olefins containing from 2 to 30 carbon atoms to produce a

free flowing particulate polyolefin material and suspending the particulate

polyolefin material in a fatty acid suspending medium which is a stable liquid in a

temperature range of from 10° to 100°C.

In still another aspect of the present invention, there is provided a method

of reducing drag in a conduit conveying a liquid hydrocarbon comprising

introducing into the conduit an effective amount of the drag reducing composition

described above. Description of the Illustrated Embodiments

Polymers which are used to prepare the finely divided polymer particles

used in the drag reducing compositions of the present invention are obtained by

polymerizing or copolymerizing mono-olefins from about 2 to about 30 carbon

atoms. More usually, the mono-olefins, which are preferably alpha olefins, used

in the preparation of the friction-reducing polymers used in the drag reducing

^compositions of the present invention contain from about 4 to about 20 carbon

atoms, most preferably from about 6 to about 10 carbon atoms.

Any of several well known methods for polymerizing the mono-olefins may

be employed to produce the polymeric/co-polymeric friction-reducing agents

used in the drag reducing compositions of the present invention. A particularly

suitable method is the Ziegler process which employs a catalyst system

comprising the combination of a compound of a metal of Groups IVb, Vb, Vlb, or

VIII of the Periodic Chart of Elements, with an organo metal compound of a rare

earth metal or a metal from Groups la, lla, and lllb of the Periodic Chart of the

Elements. Particularly suitable catalyst systems are those comprising titanium

halides and organo aluminum compounds. A typical polymerization procedure is

to contact the monomeric mixture with a catalyst in a suitable inert hydrocarbon

solvent for the monomers and the catalyst in a closed reaction vessel at reduced

temperatures autogenous pressure and in a nitrogen or inert atmosphere.

Methods and catalysts used in the preparation of polyolefin drag-reducing

polymers useful in the pxesent invention are disclosed in the following U.S.

patents: 4,289,679; 4,358,572; 4,415,704; 4,433,123; 4,493,903; and 4,493,904, all of which are incorporated herein by reference. While the preferred

polyalphaolefins used in the drag reducing compositions of the present invention

are generally produced by a so-called solution polymerization technique,

polymers produced by bulk polymerization methods can also be employed.

The polymers which are used in preparing the drag reducing compositions

of the present invention are generally those of high molecular weight, the only

,'iιmιtation on the molecular weight being that it must be sufficient to provide

effective friction reduction in the flowing stream of hydrocarbon in a conduit. In

general, the effectiveness of the polymer composition to reduce friction increases

as the molecular weight increases. On the upper end of the scale, the molecular

weight of the polymers used in the process of the invention is limited only by the

practicability of making the polymers. The average molecular weight of the

desirable polymers is usually over 100,000 and is generally in the range of from

about 100,000 to about 20 million. The average molecular weight of the

polymers used in the processes and compositions of the present invention is

preferably in the range of about 500,000 to about 30 million.

Generally speaking, the drag reducing compositions of the present

invention will contain from about 25 to 70%, preferably 25 to 60% by weight of

the polyolefin produced as described above, be it a solution polymerized or bulk

polymerized polymer.

In addition to the polyolefin friction reducing agent, the drag reducing

compositions of the presentinvention can contain a coating agent, e.g., a wax.

The term "wax" includes any low melting organic mixture or compound of high molecular weight which is solid at room temperature. The waxes contemplated

by the present invention can be natural, i.e., derived from animal, vegetable or

mineral sources, or synthetic as, for example, ethylenic polymers, waxes

obtained from the Fischer-Tropsch synthesis, etc. Non-limiting examples of

suitable waxes include paraffin, micro-crystalline wax, slack or scale wax,

polymethylene wax, polyethylene wax, etc. Preferably, the waxes used in the

[compositions of the present invention are hydrocarbon in nature and powders or

particulates at room temperature. In addition to waxes, other suitable coating

agents include talc, aluminum, alumina, magnesium sterate, silica gel,

polyanhydride, polymers, sterically hindered alkyl phenol antioxidants and the

like.

Generally speaking and when used, the coating agent will be present in

the compositions of the present invention in an amount of from about 1 to about

25% by weight.

The other essential ingredient in the compositions of the present invention

is a fatty acid suspending medium. The term "fatty acid suspending medium" as

used herein means a composition which contains one or more fatty acids and

which is a stable liquid in a temperature range of from about 10° to about 100°C.

The term "stable liquid" means that the fatty acid suspending medium remains

liquid in that temperature range and will not undergo any substantial thermal

degradation, i.e., thermal degradation to a point which would deleteriously affect

the composition. Also, thejatty acid suspending agent should be of a type which

can be handled safely. The fatty acid suspending medium is typically a vegetable oil, e.g., an oil extracted from the seeds, fruit or nuts of plants. It will

be understood that such vegetable oils commonly contain substantial amounts of

mixed glycerides as well as long chain fatty acids and it is intended that the term

fatty acid encompass the glycerides thereof as well. Non-limiting examples of

suitable vegetable oils that can be used as the fatty acid suspending mediums

include cottonseed oil, linseed oil, corn oil, olive oil, peanut oil, perella oil, etc. It

is contemplated that the fatty acid suspending medium can include mixtures of various fatty acid compositions, i.e., mixtures of various vegetable oils.

The fatty acid suspending medium will be present in the composition of

the present invention in an amount of from about 30 to 65% by weight.

In preparing the compositions of the present invention, the drag reducing

polymeric agent is ground at cyrogenic temperatures to produce a finely divided

free flowing particulate polyolefin material. The term "cyrogenic temperatures"

means temperatures below the glass transition temperature of the polymer or

copolymers which are being subjected to grinding. For example, when the

polyolefin friction-reducing agent is a high molecular weight poly (1-decene), the

cyrogenic temperature is below about -60°C. The temperature employed in

carrying out the grinding operation can vary depending on the glass transition

point of the particular polymer or polymers used. However, such temperatures

must be below the lowest glass transition point of the polymer. Any commercial

grinders which are capable of producing finely subdivided particles from solids

may be used in producing- the free flowing, particulate polyolefin material.

Examples of suitable grinders include impact mills, rod mills, ball mills, and the like. The particle size of the resulting particulate polyolefin material can be

controlled by methods in the art such as by varying the grinding speed or by

controlling the time of grinding. Techniques for cyrogrinding drag reducing

particulate polyolefins are disclosed in U.S. Patents 4,837,249; 4,826,728;

4,789,383, all of which are incorporated herein by reference. Depending upon

the storage, handling and transportation temperatures to which the friction

reducing compositions of the present invention are subjected, it may not be

necessary, as noted above, to include a coating agent. However, generally

speaking a coating agent will be employed and in this regard the present

invention contemplates that at least a part of the coating agent may be added as

part of the cyrogrinding step. Alternatively, the polymer can be cyroground in the

absence of any coating agent and the coating agent and cyroground polymer

added separately to the fatty acid suspending medium. Thus, for example,

cyroground poly alpha olefins friction reducing agent could be added to the

suspending medium together with wax or some other coating agent. Indeed, it

has been found that a stable non-agglomerating composition can be achieved in

this manner. However, in the usual case, the cyrogrinding of the poly alpha

olefin will occur in the presence of at least a portion of the coating agent, the

remainder of the coating agent, if needed, being added to the suspending

medium together with the cyroground poly alpha olefin.

The drag reducing compositions of the present invention can also include

a surfactant such as, for example, surfactants such as alkyl phenols, e.g., nonyl

phenol or other surface active agents. Additionally, it may be desirable in certain environments to incorporate a pore point depressant to ensure fluidity of the

composition at very low temperatures.

The stable, non-agglomerating compositions of the present invention flow

easily and can be readily injected into a pipeline or conduit containing flowing

hydrocarbons without any special equipment. Generally, the drag reducing

compositions of the present invention can be added to the flowing hydrocarbon

fluid by continuous injection by means of proportioning pumps situated at desired

locations along the conduit in which the hydrocarbon is flowing.

The hydrocarbon fluids in which friction loss may be reduced by addition

of the drag reducing compositions of the present invention include such materials

as crude oils, gas oils, diesel oils, fuel oils, asphaltic oils, and the like, varying

from materials with relatively low viscosity to high viscosity hydrocarbon

fractions.

The amount of the polyolefin friction-reducing agent used for reducing

drag in a pipeline or conduit is usually expressed as ppm (parts by weight of

polymer per million parts by weight of hydrocarbon fluid). The amount of a

polyolefin friction reducing agent required to produce the desired drag reduction

will vary depending upon the physical properties and composition of the

hydrocarbon fluid. Thus, the desired result may be obtained by the addition of

as little as two ppm or less of the polymer. Conversely, some high viscosity

fluids may require as much as 1 ,000 ppm or even up to 10,000 ppm of the

polyolefin friction reducing -agent to achieve desired drag reduction. Generally, it

is preferred to add the polyolefin friction reducing agent in amounts of from about ά to aoout ouu ppm and most preferably amounts from about 1 to about 100

ppm.

The drag reducing compositions of the present invention provide a

number of advantages. For one, the composition can easily be injected in the

pipeline without any special equipment such as special nozzles or placement of

nozzles. The compositions of the present invention readily dissolve in the

flowing hydrocarbon. Lastly, the compositions of the present invention can be

used with a much higher loading of the polyolefin friction reducing agent, polymer

contents of up to 45% or more forming stable free flowing compositions. It will

be recognized that this substantially reduces transportation costs as the shipping

volume of polyolefin friction reducing agents is substantially less. Additionally,

the molecular weight of the polyolefin friction reducing agent in the composition

can be substantially increased without handling problems associated with

conventional polymer solutions. As noted above, with increased molecular

weight, the effective performance of a polyolefin friction reducing agent is

improved. Since the suspending medium can take the form of a vegetable oil,

environmental hazards both in transportation and in use of the composition are

greatly reduced.

To more illustrate the present invention, the following non-limiting

examples are presented.

In the examples that follow, the test pipeline and the crude oil flowing

therein had the following characteristics:

26" O.D., 0.375" Wall Thickness Flow rate 10,5000 to 11 ,500 BPH (barrels per hour)

Crude Oil: West Texas Intermediate, API 40.1 , Viscosity 4.4 cSt

Pipeline temperature 62°F

Pipeline length: 20.34 miles

Elevation difference: 17 feet downhill (6 psi head)

TesM

In this test, the drag reducing composition had the following formulation:

50% by weight corn oil

0.5 wt% surfactant (nonyl phenol)

15.4 wt% polyethylene wax

34.1 wt% Poly-1-decene

10 ppmv of the above formulation was added to the pipeline. The following

results were obtained:

Pump station discharge pressure: 604 psig

Pressure at end of pipeline segment: 517 psig

Flow Rate: 10832 BPH

Pressure loss due to friction without

drag reducing composition: 604-517+6=93

Pressure loss due to friction without

drag reducing composition: 147.1

% drag reduction = (141.1-93)/141.1 =36.8%

Test 2

In this test, the drag reducing composition had the following formulation: 50.6 wt% corn oil

1.0 wt% surfactant (nonyl phenol)

1.9 wt% polyethylene wax

38.5 wt% poly-1-decene

The following results were obtained:

Pump Station Discharge Pressure: 707 psig

Pressure at end of segment: 629 psig

Flow Rate: 11102 BPH

Pressure loss due to friction with

drag reducing composition: 707-629+6=84

Pressure loss due to friction without

drag reducing composition: 152.3

% drag reduction = (152.3-84)/152.3=44.8wt%

Claims

What is claimed is:

1. A drag reducing composition comprising:

from 25 to 70% by weight of a finely divided solid polyolefin friction-

reducing agent formed from mono olefins containing from 2 to 30 carbon atoms;

from 30 to 65% by weight of a fatty acid suspending medium which is a

stable liquid in a temperature range of from 10° to 100°C.

2. The composition of Claim 1 wherein said suspending medium

comprises a vegetable oil.

3. The composition of Claim 2 wherein said vegetable oil comprises

corn oil.

4. The composition of Claim 1 wherein said polyolefin friction reducing

agent is produced by solution polymerization.

5. The composition of Claim 1 further including from 1 to 25% by

weight of a coating agent.

6. The composition of Claim 5 wherein said coating agent comprises

a wax.

7. The composition of Claim 6 wherein said wax is a hydrocarbon

wax.

8. A method of forming a drag reducing composition comprising:

finely dividing a solid polyolefin friction reducing agent formed from mono

olefins containing from 2 to 30 carbon atoms to produce a free flowing, particulate polyolefin material; and

suspending said particulate polyolefin material in a fatty acid suspending

medium which is a stable liquid in a temperature range of from 10°C to 100°C.

9. The method of Claim 8 wherein said polyolefin friction reducing

agent is finely divided by cyrogrinding.

10. The method of Claim 9 wherein said cyrogrinding is conducted in

the presence of a coating agent.

11. The method of Claim 10 wherein said coating agent comprises a

wax.

12. The method of Claim 10 wherein said wax comprises a

hydrocarbon wax.

13. The method of Claim 9 wherein the coating agent is added to said

suspending medium after said cyrogrinding.

14. A method of reducing drag in a conduit conveying a liquid

hydrocarbon comprising introducing into said conduit an effective amount of the

composition of Claim 1.

15. The method of Claim 13 wherein the amount of said composition introduced into said conduit provides from 1 to 100 ppm of said polyolefin friction

reducing agent in said liquid hydrocarbon.