Note: Descriptions are shown in the official language in which they were submitted.
o~64~3
.- B~CKGROUND OF Tll~ INV~NTION
- Thls invention relates to an improved method of pipelining
; ~waxy" crude oil by inhibiting the agglomeration of congealed
. wax particles slurried in a hydrocarbon liquid.
; Various crudc oils are very difficult to pump below
~ their pour points. The art has used heat transfer methods,
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': pour point depressants, diluents, chemicals to modify wax
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~ crystals, viscosity reducing agents, etc. to improve the
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~; ~ pumpabili~y thereo~O Al~o~ tne cxude oil has been cong~ale~
`` 2 suspended in water and the result~ng slurry pumped at temperature~
~ 3 below the pour point of the crud~ oilO Examples of patent~
: .
4 representative of th~ art include:
. S Kell~, in UOSO 271,080 separate~ wax from crude oil by
- 6 pumping the crude oil into the bottom of a tank containing a
- 7 brine at a temperature sufficiently low to congeal the wax.
8 ~he congealed wax is recovered from the brine.
9 Scott et al in UDS7 3,269,401 improves the pipelining of
~ 10 wax bearing oil by dissolving in the oil a gas, e.g. nitrogen,
!~. 11 carbon dioxide, flue ga$, a~d hydrocarbons containing less than
12 3 carbon atoms. The "gas" becomes associated in some way with
13 the wax crystals and prevents the precipitated wax from agglom-
, .~.,.
; 14 erating to form strong wax structures~ Alsof the gas collects
.. :,
on the surfaces of the wax particles, especially the larger
16 ones, to form films of gas envelopes which isolate the particles
17 from one another and prevents the wax particles from combining.
18 Watanabe in U.S. 3,468,986 forms spherical particles of
19 wax by first melting the wax and then dispersing the wax drop-
lets in a non-solvent liquid, e.g. water, maintained at a
21 temperature above the solidification temperature of the wax
., ~ . .
` ~ 22 and thereafter cools the dispersion to solidify the dispersed
23 droplets into discrete solid particles. The particles are
.,. ~ .
~ 24 coated with a finely divided agent such as calcium carbonate~
, .
, . . .
U.S. 3,679,582 to Wagenaar et al improves the flow prop~
~-i` 26 erties o ~axy crude oil by admixing OJ 001-2~ ~Y weight of a
~ 27 polysaccharide ester of a saturatcd fatty acid llaving at least
5" 28 15 carbon atoms. An cxample of a waxy crude is one containing
~9 13% wax.
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1 Sweeney et al in U.S. 3,675,671 improve~ the pipclining
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2 ~f waxy hydrocarbons by incorporating therein 0.01-0.15% by
~ 3 weight o an oil-soluble ethylene~vinyl fatty acid ester co-
; 4 polymer in which the fatty component of the ester contains 2-6
carbon atoms. The copolymers have molecular weights of about
~; 6 16,000 to about 310000.
7 In transporting slurries of congealed wax particles
B dispersed in hydrocarbon medium, some of the problems involved
are the agglomeration of the wax particles and precipitation
- 19 of wax out of the hydrocarbon medium both of which increase
` 11 the pressure drop o~ the transporting system. Applicants
- 12 have discovered that high molecular weight hydrocarbon soluble
13 polymers are useful to inhibit these adversitiesO
.
14
'.'''.-
'- 15SUMMARY OF T~IE INVENTIO~
:
16Applicants incorporate into the slurry about 1-10,000
17 ppm of a polymer soluble in the hydrocarbon liquid. The
18 polymer most preferably has a molecular ~eight greater than
19 about 10,000.
2~
21 DESCRIP~ION OF THE PREFERRED ~r1BODI~ENTS
22 Hydxocarbon mixtures having average pour points above
23 the seasonably ambient temperature of the transportation
;-, .
;- 24 system are particularly use~ul in this invention. Examples
~i- 25 include crude oil, shale, oil, tar sand oil, fuel oil, gas
26 oil, and like hydrocarbon mixtures and mixtures of two or
. ,. ~
- 27 more of the same type or different hydrocarbon mixtures.
-; 28 Crude oils are particularly useful and especially those
~ 29 classified as "waxy" crude oils. Examples of the latter
,j~ 30
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`~include crude oils which exhibit a "waxy gel" appearance
2 at seasonably ambicnt temperature and which contain about 1%
3 to about 80% wax (wax is defined as the precipitate which
4 orms after one part of crude oil is dissolved in 10 parts
of methyl ethyl ketone at about B0C. and the mixture chilled
6 to -25~C.) and which have an average pour point above the
7 average ambient minimum temperature of the transporting
8 system at the time of transport. Examples of average pour
, .
~ 9 points of crude oils particularly useful with this invention
~ :.
include pour points of about -10 to about 200F. and prefer
'~ 11 ably about 0 to about 150F. and more preferably those
~, 12 having pour points greater than about 50F.
, . .
13 The hydrocarbon mixture is first fractionated into at
- 14 least two fractions, an o~erheads fraction which has a
~i 15 relatively low pour point (also identified as having a
, ~,~; .
16 density and viscosity at a given temperature lower than the
. 17 original hydrocarbon mixture) and a bottoms fraction which
18 has a relatively high pour point (also identified as having
~;
; ~ 19 a density and viscosity at a given temperature above that
~ . . .
}~ 20 of the original hydrocarbon mixtu~e). The bottoms fraction
- 21 can ~e any portion of the original hydrocarbon mixture but
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~ 22 is about 1 to about ~0~ and preferably about 20 to about
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~`; 23 70% and more preferably about 30 to about 60% by weight of
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24 th~ original hydrocarbon mixtureO Fractions other than the
- ~5 overhead and bottom fractions can be obtained and used in
26 other processing streams. Also other fractions can he com-
'~ 27 bined with the relatively high pour point fraction b~fore
r ' ~ ,, '
-~ 28 congelation.
~- 29 Fractionation can be accomplished at atmospheric
i 30 pressure, sub or superatmospheric pressure and at low and
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h temperatur~s ~y proce.sses such as distillation, solvent
2 extraction, membrane fractionation, crystallization, or any
3 process which separates the hydrocarbon mixture into at
4 lea~t two different fractions. Optionally, any equivalent
amount of up to 50%, preferably UE~ to 42% and more prefer-
6 ably up to 33% by volume of the high pour point fraction
7 can be cracked (by thermal, hydrogenation, catalytic,
8 combina~ions thereof, or other e~fective methods) during
9 fractionation or before congelation.
The low poux point fraction should have a pour point
: ,. .
11 at least 1 and preferably at least about 5 and most prefer-
12 ably at least about 10F. below the average of the minimum
13 temperature range of the transporting system at the time the
14 slurry is transported.
Ater the hydrocarbon mixture is fractionated, all or
16 at least a portion (preferably at least 50%) o~ the high
17 pour ~oint ~raction or the bottoms fraction is collected,
18 congealed and comminuted to form substantially solid particles
19 having an average diameter of less than about 0.05 to about
20 mm (millimeters) or more and preferably about OD1 to
21 about 5 mm and more preerably a~out 0.5 to about 3 mm. The
22 particles can be of any shape, e~g. tubular, spherical, or
23 irregular, but are preferably spherical and can be of
24 substantial uniform or random diameter sizes. Comminution is
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accomplished by prilling, extruding, molding, shredding, grinding,
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26 shearing, and like methods for dispersing or disintegrating the
27 uncongealed or congealed material. Where shredding or grinding
28 is used, comminution preferably takes place a~ter congelation.
29 Congealing as used herein includes solidification, crystalli-
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r"~. 30 zation, making into a consistency like a firm jelly, etc.
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1 The hi~h pour point fr~ction i~ pre~erably about 1 to about
_50F~ and more preferably about 10 to about 100F. above
3 its average congelation temperature as it enters the congelation
4 and/or comminution steps.
Prilling can be accomplished by spraying the bottoms
6 ~raction into a prilling tower where the prill comes in contact
7 w~th gas (e.g. air, N2, natural gas, or like gases) and/or
8 water (liquid and/or vapor) using known prilling techniques.
9 Prilling tower velocities below about 20 ft/sec (feet per second)
. . .
~ 10 and preferably below 10 ft/sec and more preferably below about
.;" ~ ,
11 5 ~t/sec are useful. Temperature of the air entering the
12 prilling tower is preferably about 1 to about 230 below to
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~ 13 about 150 above and more preferably about 100 ~elow to
;.;
`~ 14 about 10F. above the average congealing temperature of the
fraction entering the tower. A mist of water is pre~erably
16
sprayed into the tower along with the air. The water temperature
should be at least about 5F. and preferably at least about 20F.
18
below the congealing temperature of the high pour point fraction~
Another method for congealing the high pour point fraction
- -
is by extruding or spraying the fraction into water, preerably
at about 5 to about 100~. and more preferably about 130 to
:
about 220F. above its average congelatlon temperature. ~ore
~- preferably, the water i5 in turbulent flow at the injection point
of the high pour point fraction. The dispersed high pour point
fraction is thereafter congealed by admixing cooler water, e.g.
26
- at about ambient temperature, with the aqueous mixture.
,~ Surfactants or other additives such as bactericides,
~- - 28
;~ insecticides, etc. can be incorporated into the high pour point
.- 29
~raction be~ore it is congealed, e.g. it can be admixed with the
;~ 30
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1 ~ action beforc or a~ i~ enters thc prilling tower. Volum¢
2 dmount-~ o~ a~out 0.0001 to about 20~ ~nd pre~erably about 0.001
3 to about 10%, and more preferably about 0.01 to about 1% by
4 volume, based on the fraction, are useful. The surfactants
should be at least partially hyclrocarbon solu~le. It i3 postu-
6 lated that the surfactant molecules tend to orient their ~Iydror
7 ph~lic portion radially at the droplet surface and thus impart
, . .
~- 8 a hydrophilic property to tlle pxill which in turn inhibits solu-
~i ~ bîlization of the prill in the Low pour point fraction. Thero-
-- lO retically, this happens as the droplets of wax are formed.
`~ 11 Examples of useful surfactants include fatty acids (e.g. those
~` .12 containing about lO to a~out 20 carbon atoms) and preferably mono-
13 valenk cation containing salts thereof. Sorbitan monolaurate
.
- 14 is an example of a useful surfactant. Preferably the suractant
~; 15 is a petroleum sulfonate preferably having a monovalent cation,
16 e.g. Na , and preferably }laving an average equivalent wei~ht
17 of about 200 to about 600 and more preferably about 250 to about
!: 18 500 and most preferably about 350 to abo~t 420.
19 ~iscosity reducing agentsg pour p~nt reducers,
.
~ ~ 20 drag reduction agents, etc. can be admixed witn the
i 21 slurry to impart desired properties.
- 22 A~ter the high pour point fraction is congeale~l or
!: .
23 during the congelation and/or comminution thereof~ the
24 particles can be coated with a solid material. This
inhibits agglomeration of the particles and may permit
26 higher slurry t~npcratures during transportation.
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`~ 27 Examples of coatings include those disclosed in U.S.
;.~
~-~ 28 Patent No. 3,468,986 to Watanabe. The coating can be
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29 applied as a spray, eithcr hydrous or anl~ydrous, or as
a~ aqueous bath containing the soli~ material.
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-~ About 1 to about 10,000 and preferably about 2.5 to
about 500 ppm, and more preferably about 5 to about 100 ppm
` of the high molecular weight polymer soluble within the
. .
liquid hydrocarbon phase of the slurry is incorporated
within the slurry. The average molecular weight of the poly-
- mer is preferably about 100 to about 5 million or more. The
average molecular weight is more preferably greater than
5,000 and most preferably greater than 10,000. The polymer
can be, in general, any polymer which is hydrocarbon soluble
and, of course, which inhibits the agglomeration of the wax
particles. Examples of such polymers include pol~dimethyl
siloxanes, polyisobutylene, ethylene propylene copolymers,
ethylene-vinyl fatty acids, ester copolymers defined in U.S.
: . .
Patent No. 3,675,671 to Sweeney et al and like copolymers,
butyl rubber, and like polymers; polysaccharide derivatives
having saturated aliphatic hydrocarbon chains of at least
15 carbon atoms in the molecule, examples of these poly-
saccharides are U.S. 3,679,582 to Wagenaar et al; modified
polysaccharide such as Soloid~ 1040, a dimethyl dihydro-
:
genate~ tallow ammonium sulfated cellulose having a mole-
cular weight of about 100,000 (identified in U.S. 3,637,520);
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;~ and other oil soluble polymers that inhibit agglomeration of
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wax particles.
Concentration of the polymer in the low pour point
; fraction will depend on the concentration of congealed
.,.,..~
` wax particles, the type of polymer, the physical properties
- of low pour point fraction, e.g. if the low pour point
. . .
fraction contains dissolved wax, then sufficient polymer
should be added to inhibit precipitation of this wax,
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1 ~pecially when it is anticipated that the temperature o
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2 the slurry will decrease.
` 3 ~he polymer is preferably added to the low pour
4 point fraction prior to slurrying the congealed high pour
S point fraction with the low pour point fraction. ~owever,
6 the polyrner can be admixed with the slurry after it is
7 constituted. Also, part of the pol~ner can be incorporated
8 into the low pour point ~raction before slurryinq an~ the
: 9 re~idue added after slurrying.
After the high pour point fraction is congealed into
11 the desired particle size, at least a portion and prefer-
- 12 ably all of the particles are slurried ~e.g. combined or
~ .
:~ 13 mixed) with the low pour point fraction. The concentration
. ..
14 of congealed fraction in the slurry is preferably about 1~
:-'
- 15 to about 80% and more preferably about 5% to about 55%
16 and most preferably about 10% to about 50% by weight.
17 Water may be entrapped within the congealed fraction or
` 18 sorbed, e.g. for up to about 10 and preferably less than
- 19 about 3% and more preferably less than about 1~ by weight
~,. .~ .
of water within the slurry. During the slurrying operation,
` 21 the temperature of the low pour point ~raction is preferably
~" ~ .. .
i~; 22 about 30 below to about 30 above and more preferably about
;~ 23 20 below to about 20 above the minimum, seasonably ambient
,r,',''." 24 temperature of the transportation system. Also, the tempera-
ture of the low pour point fraction during slurrying should
26 be below an~ preerably at least about 5F. and more prefer-
; 27 ably at least about 15F. and most preferably at least
28 about 30F. below the solution ternperature of the congeale~
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~ 29 high pour point fraction in the low pour point fraction.
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1 A llquid diluent, such as crude oil (preferably a non-
2 ~waxy" crude~, straigllt run gasoline, reservoir condensate,
:"
3 crude oil fraction(s), or like hydrocarbon, can be admixed
.
4 with the low pour point fraction either before or after the
S slurrying operation. Any diluent which is miscible or
: 6 substantiall~ miscible with the low pour point fraction and
7 which preferably has a pour point below the minimum ambient
~` 8 a~erage tel,lperature of the transportation system at the time
9 of transport is useful with this invention.
- 10 A gas miscible with the low pour point fraction but
11 preferably immiscible with the congealed fraction can be
~- 12 admixed with the slurry to reduce the viscosity thereof~
~ .... . .
13 The gas may be liquid at the temperature and pressure of
14 the transportation system. Examples of such miscible gases
`~` 15 include COz, lower hydrocarbons containing less than 4
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; 16 carbon atoms, etc.
` 17 The slurry can be subjected to a shearing action through
.,
18 a centrifugal pump or like means before it is transported in
~ 19 a pipeline.
,~ 20 The slurry can be trànsported in bulk, e.g. tank car,
~` 21 tank truck, tank trailer, tank barge, tanker or like means,
.: ~
22 but is prefera~ly transported in a conduit, such as a pipe-
23 line. O course, the conduit pipeline system may have tank
24 batteries, i.e. collection or holding tanks, associated
,;.
with it. The collection or holding tanks may have or have
26 some means of controlling the temperature of the slurry.
,-,
27 The slurry can be transpoxted under laminar, transi-
28 tional (e.g. Reynolds Wumber range of about 2000 to about
~-; 29
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; 30 720109-A -10
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6~43
1 4000), turbulent or a combination of flow conditions in the
2 conduit. Turbulent flow conditions may be preferred where it
3 iB desired to maintain the congealed particles in a "homo-
4 geneous" dispersed state.
Compositions of this invention require reduced pump
- 6 pressures, as compared to prior art hydrocarbon mixtures,
7 when being transported through conduits. Also, the dispersed
8 particles are ~ept in suspension more easily than the prior
9 art hydrocarbon mixtures, this is due to the polymer.
The solubility characteristics of the wax~ the hydro-
11 carbon carrier fluid, the time period during which the slurry
12 will be transported, and the ambient temperatures along the
13 transportation route determine the required make-up of the
~4 slurry. The pump capacity along a pipeline will also regulate
the composition o the slurry. Thus, where a pipeline run is
~6 short, the hydrocarbon carrier can be a relatively good
17 solvent for the wax if the pump capacity can take care of the
18 increasing viscosity of the solution~ However, if the run
-` 19 i5 long and there is little excess pump capacity, it is
~ 20 preferable to have a hydrocarbon carrier which is not a
;s; 21 good solvent for the wax.
22 An engineer or chemist formulating a slurry for trans-
- 23 portation over a predetermined distance during a predetermined
;; 24 time period at predicted ambient temperatures along the route
of transportation will be able to select rom the hydrocarbon
~; 26 fractions available those combinations which will insure
i~ 27 that a slurry can be maintained which is pumpable by the
~; 28 existing pump capacity.
.~ .
29
30 720109-A
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- 1 -- Workin~ Examples _ ~0464~3
2 A waxy crude oil i5 fractionated into a low pour
3 point fraction taverage pour point about 12F.) and a
- 4 high pour point raction (average pour point about 120F.)
.:
` 5 The hi~h pour poin~ fraction is prilled by spraying it
through a nozzle into a tower wherein water is sprayed
7 into a tower to facilitate cooling of the dispersed high
8 pour point fraction as it is sprayed and falling in the
g tower. Average diameter of the prill is about 0.1-1 ~n.
About 35~ by weight of tne prilled high pour point fraction
- 11 is slurried in 65% by weight of the low pour point frac~ionO
- 12 This slurry is pumped in a conduit and samples are taken
13 during the pumping thereof to determine the amount of
14 agglomeration of the prill.
A comparative study is made with identically the
';.,
16 same slur~y exce~t the low pour point fraction contains
17 100 ppm. of Soloid 1040~ The polymer is incorporated J
18 into the low pour point fraction before the prill is slurried
19 with the low pour point fraction. Samples are ~aken along
; . . _
` the conduit to determine the amount of agglomeration of the
;::
21 prill. This run, compared to the previous run, indicates
22 that the polymer tends to inhibit agglomeration of the
23 prill, and as a result, facilitates pwnping of the slurry.
24 It is not intended that this example limit the inven-
tion. R~ther, all equivalents are to be included within
26 the scope of the invention as defined in the specification
: .
~ 27 and appended claims.
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, 29
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