US3853356A

US3853356A - Method of pumping waxy crude oil

Info

Publication number: US3853356A
Authority: US
Inventors: L Merrill
Original assignee: Marathon Oil Co
Current assignee: Marathon Oil Co
Priority date: 1973-08-23
Filing date: 1973-08-23
Publication date: 1974-12-10
Anticipated expiration: 1991-12-10
Also published as: AT340027B; GB1475741A; DE2433472A1; PL98261B1; CA1010476A; FR2241742B1; BR7406965D0; CH606902A5; IT1017495B; RO66496A; DD115194A1; ATA685374A; FR2241742A1; AU7150874A

Abstract

Crude oils containing at least 25% wax are transported by fractionating (e.g., by distillation) the crude oil into at least a relatively high pour point fraction, a relatively medium pour point fraction and a relatively low pour point fraction. The medium pour point fraction is congealed (preferably by prilling), and slurried in a mixture of the relatively low pour point fraction and a portion of the high pour point fraction. The remaining high pour point fraction can be congealed with the medium pour point fraction. Diluents, e.g., crude oil, can be added to improve pumpability. This procedure reduces the formation of strong wax matrixes and creates a slurry with better pumpability characteristics.

Description

[451 Dec. 10, 1974 4] METHOD or PUMPING WAXY CRUDE OIL [75] Inventor: LaVaun S. Merrill, Jr., Englewood,

[73] Assignee: Marathon Oil Company, Findlay,

Ohio

[22] Filed: Aug. 23, 1973 [21] App]. No.: 390,837

52 us. Cl 302/66, 137/1, 208/370 [51] Int. Cl. F17d l/00, B65g 53/04 [58] Field of Search 302/66, 14; 137/13, 1; 208/370; 252/83 [56] References Cited I UNITED STATES PATENTS 2,204,967 6/1940 Moser 208/370 X 2,303,823 12/1942 Coberly 208/370X 2,981,683 4/1961 Simpson et al. 208/370 X Titus 137/13 Primary Examiner-Evon C. Blunk Assistant ExaminerJames L. Rowland Attorney, Agent, or Firm-Joseph C. Herring; Richard C. Willson, Jr.; Jack L. Hummel [5 7] ABSTRACT Crude oils containing at least 25% wax are transported by fractionating (e.g., by distillation) the crude oil into at least a relatively high pour point fraction, a relatively medium pour point fraction and a relatively low pour point fraction. The medium pour point fraction is congealed (preferably by prilling), and slurried in a mixture of the relatively low pour point fraction and a portion of the high pour point fraction. The remaining high pour point fraction can be congealed with the medium pour point fraction. Diluents, e.g., crude oil, can be added to improve pumpabilityv This procedure reduces the formation of strong wax matrixes and creates a slurry with better pumpability characteristics.

14 Claims, No Drawings METHOD OF PUMPING WAXY CRUDE OIL BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to an improved method of transporting waxy" crude oils as a slurry containing congealed waxy particles.

2. Description of the Prior Art It is difficult to pump viscous crudes below their pour point. Chemical additives and heat transfer methods have been studied to improve pumpability. Also, the oil has been congealed, suspended in water and the resulting 'slurry pumped at temperatures below the pour point of the crude oil.

Tracer lines and large heat exchangers have been placed intermittently along the pipeline to maintain the crude oil above its pour point and thus facilitate pumping of same. The main disadvantage of these methods is that the crude oil tends to set up during shutdowns.

Examples of patents representative of the art include:

Iberfell et al., In US. Pat. No. 2,526,966 teach transporting viscous crude oils by removing the light hydrocarbons (including straight-run gasoline), hydrogenating the residue to increase the fluidity thereof and then combining the hydrogenatedproduct and the light hydrocarbons to obtain a pumpable mixture.

Scott et al in US. Pat. No, 3,269,401 facilitate the flow of wax-bearing oil by dissolving in the oil, at superatmospheric pressure and while above its pour point, an inert gas, which prevents the precipitated wax from agglomerating to form strong wax structures.

Kane in US. Pat. No. 3,425,429 transports viscous crude oils by forming an oil-in-water emulsion and then pumping same. The water contains a nonionic surfactant.

Watanabe in U.S. Pat. No. 3,468,986 forms spherical particles of wax by dispersing melted wax droplets in a non-solvent liquid (e.g., water) and thereafter cooling the dispersed wax to form discrete solid particles which can be coated with finelydivided coating solids such as calcium carbonate, etc. Watanabe teaches that it is known in the art to disperse waxy particles by molding, prillin g, spray drying, extruding, etc.

above the seasonably ambient temperature of the transportation system and which contain at least about 25 percent wax are useful with this invention. Crude oils are particularly useful and especially those classified as waxy crude oils. Examples of the latter include crude oils containing about 25 percent to about 80% wax (wax is defined as the precipitate which forms after one part of crude oil is dissolved in 10 parts of methyl ethyl ketone at above 80C. and the mixture chilled to 25C.). Examples of average pour points of crude oils particularly useful with this invention include about 0 to about 200F. and preferably about 20 to about 150F. and more preferably those having pour points greater than about F.

The hydrocarbon mixture is fractionated into at least three fractions, an overheads fraction which has a relatively low pour point, a middle fraction which has a medium pour point and a bottoms fraction which has a relatively high pour point. For a typical crude, the low pour point fraction will generally have typical molecules containing up to about 25 carbon atoms, the medium pour point fraction will have molecules containing between about 15 to about 30 carbon atoms, and the high pour point fraction will be composed of molecules containing greater than about 20-26 carbon atoms. For a typical waxy hydrocarbon mixture, the low pour point fraction can be about 20 to about 95 and preferably about 40 to about 95 and more preferably about 50 to about 70 percent of the original crude, the medium pour point fraction can be about 3 to about 30, preferably about 5 to about 20 and more preferably about 10 to about 20 percent of the original crude and the high pour point fraction can be about 5 to about 60 and preferably about 10 to about 40 and more preferably about 20 to about 30 percent of the original crude oil.

It is to be understood that more than the three abovefractions can be obtained during fractionation. Also, other crude oil fractions or hydrocarbon(s) can be combined with the crude oil either before or after fractionation. For example, other hydrocarbon(s) or crude Allen in US. Pat. No. 3,548,846 transports, waxy I crude oils by admixing propane or butane within the crude oil.

This technology, except for heat transfer methods and crude oil-water suspension systems, is generally economically unattractive.

SUMMARY OF THE INVENTION point fraction with the low pour point fraction, con- 7 gealing at least a portion of the medium pour point fraction and/or the high pour point fractions. Slurrying the congealed particles with the low pour point mixture and the slurry transported, preferably in a conduit.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hydrocarbon mixtures having average pour points oil fractions can be combined with the medium pour point fraction before congelation thereof.

Fractionation can be accomplished by any process which will separate the hydrocarbon mixture into at least three fractions, e.g., distillation, solvent extraction, membrane fractionation, or crystallization. Of course, the original hydrocarbon mixture can be fractionated into an overheads fraction and a bottoms fraction and the bottoms fraction further fractionated into a medium pour point fraction and a high pour point fraction. Optionally, up to about 30 percent of the crude oil can be cracked e.g., by thermal, hydrogenation, catalytic, or combinations thereof, prior to, during, or after fractionation.

The low pour point fraction should have a pour point at least about l, preferably at least about 10, and most preferably at least about 20 below the average of the minimum temperature range of the transportation system at the time the slurry is transported.

After the hydrocarbon mixture is fractionated, all or at least a portion (preferably at least about percent) of the medium pour point fraction, preferably containing up to 98 percent of the high pour point fraction, is collected, congealed and comminuted to form substantially solid particles having an average diameter of about 0.05 or less to about 20 or more mm (millimeters) and preferably about 0.l to about mm and more preferably about 0.5 to about 3 mm. The particles can be of any shape such as tubular, spherical, or irregular, but are preferably spherical and can be of substantially uniform or random diameter sizes. Comminution is accomplished by prilling, extruding, molding, shredding, grinding, shearing, and like methods for dispersing or disintegrating the uncongealed or congealed material. Congealing as used herein includes solidification, crystallization, making into a consistency like a firm jelly, etc.

The medium pour point fraction is preferably about 1 to about 150 and more preferably about to about 100F. above its average congelation temperature as it enters the congelation and/or comminution steps. Medium pour point fraction as used hereinafter, can include other fractions, e.g., high pour point fraction, etc.

Prilling can be accomplished by spraying the fraction into a prilling tower where the prill comes in contact with gas (e.g., air, N CO natural gas, or like gases) and/or water (liquid and/or vapor). Optionally, the prill is collected in a water bath at the bottom of the tower. Air is the preferred gas and is preferably moved through the prilling tower by natural or forced convec tion at velocities sufficient to not exceed the drop or settling rate of the prill falling through the prilling tower. Air velocities below about ft/sec and preferably below 10 ft/sec and more preferably below about 5 ft/sec are useful. Temperature of the air entering the prilling tower is preferably about 1 to about 230 and more preferably about 10 to about 150F. below the congealing temperature of the prill. Temperature of the air leaving the prilling tower is preferably about 230 below to about 150 above and more preferably about 100 below to about 10F. above the average congealing temperature of the fraction entering the tower. Water is preferably sprayed into the tower along with the air, the water being at temperature at least about 5F. and preferably at least about 20F. below the congealing temperature of the medium pour point fraction. Also, it is preferred that the water be sprayed into the tower as a mist.

Another method for congealing the medium pour point fraction is by extruding or spraying into water, the fraction preferably at about 5 to about l00F. and more preferably about 130 to about 220F. above its average congelation temperature. Preferably the water is in turbulent flow at the introduction or injection point of the fraction in the water. The dispersed fraction is thereafter congealed by admixing cooler water, e.g., at about ambient temperature. The congealed fraction is then separated from the water, slurried in the low pour point fraction and then transported.

Surfactants or other additives such as bactericides, insecticides, etc., can be incorporated into the medium pour point fraction before congelation. Volume amounts of about 0.000] to about 20 percent and preferably about 0.001 to about 10 percent, and more preferably about 0.01 to about l percent by volume, based on the fraction, are useful. A surfactant should be at least partially hydrocarbon soluble. It is postulated that the surfactant molecules tend to orient their hydrophilic portion radially at the droplet surface and thus impart a hydrophilic property to the prill which in turn inhibitssolubilization of the prill in the low pour point fraction. Theoretically, this happens as the droplets of wax are formed. Examples of useful surfactants include fatty acids (e.g., those containing about 10 to about 20 carbon atoms) and preferably monovalent cation containing salts thereof. Sorbitan monolaurate is an example of a useful surfactant. Preferably the surfactant is a petroleum sulfonate and more preferably one having a monovalent cation, e.g., Na", and preferably having an average equivalent weight of about 200 to about 600 and more preferably about 250 to about 500 and most preferably about 350 to about 420.

Chemical agents to facilitate suspension of the congealed fraction can be added to the slurry. Examples of such agents include high molecular weight polymers, including biopolymers and chemically synthesized polymers. Also, viscosity reducing agents, pour point reducers, drag reduction agents can be admixed with the slurry to impart desired properties.

After the medium pour point fraction is congealed or during the congelation and/or comminution thereof, the particles can be coated with a solid material. This inhibits agglomeration of the particles and may permit higher slurry temperatures during transportation. Examples of coatings include those disclosed in US. Pat. No. 3,468,986 to Watanabe. Where the high pour point fraction is prilled, the coating can be applied as a spray, either hydrous or anhydrous, or as an aqueous bath containing the solid material. Examples of useful coating materials include inorganic and organic salts of the metals of Group II, III, IV-A, V, VI, VII, and VIII of the Periodic Table; synthetic resins such as cellulose acetate, polystyrene, polyethylene, polyvinyl acetate, and like resins; and other materials such as clay (e.g., bentonite), kaolin, Fuller's earth and other aluminum silicates, limestone, etc. Calcium carbonate is a preferred coating material.

At least a portion and preferably all of the congealed particles are slurried in the low pour point fraction. The low pour point fraction contains about 1 to about 20 and preferably about 2 to about 15 and more preferably about 5 to about 10 percent of the high pour point fraction. By adding the high pour point fraction to the low pour point fraction, fine crystals which do not have a strong matrix-forming tendency are obtained. As an unusual correlation, if the'medium pour point fraction were added to an equivalent amount of low pour point fraction without the high pour. point fraction, larger crystals having a strong matrix-forming tendency would be obtained. However, by combining the high pour point fraction with the low pour point fraction, a more fluid slurry is obtained than if the low pour point fraction were combined with a portion of the medium pour point fraction or if both the medium pour point fraction and the high pour point fraction were congealed and thereafter slurried in the low pour point fraction. Based on the volume amount of the low pour point fraction, preferably about 5 to about 15 percent of the high pour point fraction is admixed with the low pour point fraction. Also, whole crude oil can be added to the low pour point to obtain the same results; based on the volume of the low pour point fraction and the medium pour point fraction, about 10 to about 30 percent of the whole" crude oil can be admixed to ob tain the smaller wax crystals.

Concentration of the congealed fraction in the slurry is about I to about percent and more preferably about 5 to about 55 percent and most preferably about 10 to about 50 percent by weight. Water may be entrapped within the congealed fraction or water may be sorbed into the wax particles. In addition, water may slop over from the congealing process; As a result, the slurry may contain up to about 20 percent and preferably less than about and more preferably less than about 2 percent by weight of water within the slurry.

During the slurrying operation, temperature of the low pour point fraction is preferably about 30 below to about 30 above and more preferably about 20 below to about 20 above the minimum seasonably ambient temperature of the transportation system. Also, the temperature of the low pour point fraction during slurrying should be below, and preferably at least about 5F. and more preferably at least about F. and most preferably at least about 30F. below the solution temperature of the congealed medium pour point fraction.

A liquid diluent, such as crude oil and preferably a non waxy crude, straight-run gasoline, reservoir condensate, crude oil fraction(s), or like hydrocarbon can be admixed with the low pour point fraction either before or after the slurrying operation. Generally speaking, any diluent which is miscible or substantially miscible with the low pour point fraction and which preferably has a pour point below the minimum ambient average temperature of the transportation system at the time of transporting the hydrocarbon mixture is useful with this invention.

A gas miscible with the low pour point fraction but preferably immiscible with the congealed fraction can be admixed with the slurry to reduce the viscosity thereof. The gas can be liquid at the temperature and pressure conditions of the transportation system. Examples of such gases include carbon dioxide, lower hydrocarbons containing less than 4 carbon atoms, etc. The gas can be injected into the slurry under conditions such that the gas is present in concentrations greater than that present at atmospheric conditions.

The slurry can be subjected to shearing action before it is actually transported. For example, it can be sheared in a centrifugal pump or like mechanical means before it is injected in a pipeline for transportation therein.

Transportation of the slurry can be in bulk, e.g., tank car, tank truck, tank trailer, tank barge, tanker or like means but it is preferably transported in a conduit such as pipeline. Of course, the conduit system may have tank batteries, i.e., collection or holding tanks associated with it.

The slurry is preferably transported in a pipeline at a temperature which is not below the average pour point of the low pour point fraction of the slurry and preferably is at least about lF and more preferably at least about 5F. and most preferably at least about 10F. above the pour point of the low pour point fraction.

WORKING EXAMPLES EXAMPLE I A waxy" crude having an average pour point of 1 10F. and an average APl gravity of about 50, is fractionated by distillation into a low pour point fraction (average pour point about 130F.), a medium pour point fraction (average pour point about 125F.) and a high pour point fraction (average pour point about 15F.). The average hydrocarbon molecure of the low pour point fraction contains up to about to 22 carbon atoms, the average molecule of the medium pour point fraction contains 18 to about 28 carbon atoms and the average molecule of the high pour point fraction contains more than about 28 carbon atoms. To show the effect of combining the low pour point fraction with the high pour point fraction and the effect of obtaining finer crystals and the reduction in the wax matrix-forming tendency, the following series of mixing experiments were conducted:

1. 85 ml of the low pour point fraction are mixed with 15 of the medium pour point fraction and the resulting mixture agitated and observed after standing for 24 hours-the crystals formed were rather large in diameter and exhibited a very strong wax matrix-forming tendency. 1. 85 ml of the low pour point fraction are admixed with 15 ml of the high pour point fraction and the resulting mixture let stand for 24 hours. A finer wax crystal than the mixture of 1 is observed and it has less tendency to form a strong wax matrix as compared to l. 3. The misture of 1 is duplicated except 20 ml of the high pour point fraction is admixed and the resulting mixture let stand for 24 hours. Upon observation, it was determined that the wax crystals were smaller in size than the crystals of 1 and also the resulting mixture had less tendency to form a strong wax matrix.

EXAMPLE II A given waxy crude oil is distilled in one distillation to give 40 wt. percent low pour point fraction, 15% medium pour point fraction and 45 percent high pour point fraction. A second distillation on the same crude is performed to give 50 percent low pour point fraction and 50 percent high pour point fraction. Enough of the high pour point fraction from the first distillation is dis solved in the 40 percent low pour point fraction to give a mixture comprising 50 percent of the whole crude. The medium pour point fraction is then combined with the remaining high pour point fraction and this mixture congealed to obtain substantially spherical prills. The congealed prills are then added to the 50 percent low pour point mixture to give a 30 percent slurry. This slurry is then pumped through a /2inch pipeline at 40F. The high pour point fraction from the 2nd distillation is then congealed into prills and the prills are added to the 50 percent overhead fraction from that'distillation to give a 30 percent slurry. This slurry is then pumped through the same /2inch pipeline at 40F. Comparison of the two runs shows that the 30 percent slurry made up with the 50 percent mixture from the first distillation gives lower pressure drops than did the slurry made from the products of the 2nd distillation.

The above examples are not intended to limit the invention. All equivalents obvious to those skilled in the art are intended to be incorporated within the scope of theinvention as defined within the specification and appended claims.

What is claimed is:

1. An improved process of transporting a hydrocarbon mixture that contains at least about 25 percent wax (this wax is defined as the precipitate which forms after 1 part of the hydrocarbon mixture is dissolved in 10 parts of methylethyl ketone at C. and the mixture chilled to 25C.),- the improved process comprising fractionating the hydrocarbon mixture into at least a low pou'r point fraction, a medium pour point fraction, and a high pour point fraction, substantially congealing at least a portion of the medium pour point fraction and optionally a portion of the high pour point fraction, admixing at least a portion of the high pour point fraction with the low pour point fraction and thereafter slurrying the congealed particles with the low pour point fraction to obtain a hydrocarbon slurry suitable for transport at predetermined temperatures.

2. The process of claim 1 wherein the hydrocarbon mixture has an average pour point above the average seasonably minimum temperature of the transportation system.

3. The process of claim 1 wherein the slurry is transported in a pipeline.

4. The process of claim 1 wherein the concentration of the congealed fraction in the slurry is about 1 to about 80% by weight.

5. The process of claim 1 wherein the concentration of the congealed fraction in the slurry is about 5 to about 55 percent by weight.

6. The process of claim 1 wherein slurrying is effected at a temperature at least about 5 below the average solution temperature of the congealed fraction within the slurry.

7. The process of claim 1 wherein the medium pour point fraction is congealed at a temperature at least about 5 below its pour point.

8. The process of claim 1 wherein the congelation is effected by prilling.

9. The process of claim 1 wherein the average diameter of the congealed fraction is about 0.05 to about 10. The process of claim 1 wherein the slurry contains up to about 10 percent by weight water.

11. The process of claim 1 wherein a hydrocarbon diluent is admixed with the hydrocarbon slurry to improve the pumpability'thereof.

12. A process for preparing a hydrocarbon slurry from a waxy crude oil containing at least 25 percent wax (wax is defined as the precipitate which forms after 1 part of hydrocarbon mixture is dissolved in 10 parts of methylethyl ketone at about C. and the mixture chilled to 25C.) that can be effectively transported in a conduit, the process comprising fractionating the crude oil into at least a low pour point fraction, a medium pour point fraction and a high pour point fraction, substantially congealing at least a portion of the medium pour point fraction which can optionally contain at least a portion of the high pour point fraction, thereafter slurrying at least a portion of the congealed particles in the low pour point fraction which contains at least a portion of the high pour fraction to obtain a hydrocarbon slurry containing about 5 to about 55 percent by weight of the congealed particles and transporting the slurry in a conduit at a temperature below about the average pour point of the low pour point fraction.

13. The process of claim 12 wherein the concentration of the congealed fraction in the slurry is about 5 to about 55 percent by weight.

14. The process of claim 12 wherein a hydrocarbon diluent is admixed with the slurry to improve the pumpability thereof.

A PatentNo, 3,853,356 D e December 10,1974

lnventofls) LaVaun S. Merrill, Jr.

It is certified that error appears in the above-identified patent A and that said Letters Patent are hereby corrected as shown below:

Column 6, line 11, after "15" insert ml Column 6, line 15, after "dency," delete "l." and insert 2.

# Column 6 line 20 "misture" should read mixture Column 8 line 22 following "temperature" insert not This certificate supersedes Certificate of Correction issued March 4, 1975.

i Signed and Scaled this Second D y 0f May 1978 sr.-\|. .1tlust:

RUTH .\I.-\S()\ LUTRELLE F. PARKER t-ittmting Officer Acting ummissiom'r of Patents and Trademarks C 4 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 53,35 r Dated December 10 1975 Inventor(s) L S Merrill Jr It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col. 6, line 11: After "15" I insert -ml-.

Col. 6, line 15: After dency.,' delete "l." and insert -2.-.

Col. 6, line 20: Delete "misture'? and insert -mixture. f

Signed and sealed this 4th day of Mareh 1975.

(SEAL) Attest- C. l'iARSHALL DANN RUTH C. Z'IAS Commissioner of Patents Attestin; OFficer and Trademarks FORM PO-OSO (10-69) USCOMM-DC GO376-P69 W U.S. GOVEINIENT PRINTING OFFICE: 1!, O-JGi-SSI.

Claims

1. AN IMPROVED PROCESS OF TRANSPORTING A HYDROCARBON MIXTURE THAT CONTAINS AT LEAST ABOUT 25 PERCENT WAX (THIS WAX IS DEFINED AS THE PRECIPITATE WHICH FORMS AFTER 1 PART OF THE HYDROCARBOM MIXTURE IS DISSOLVED IN 10 PARTS OF METHYLETHYL DETONE AT 80*C. AND THE MIXTURE CHILLED TO -25*C.), THE IMPROVED PROCESS COMPRISING FRACTIONATING THE HYDROCARBON MIXTURE INTO AT LEAST A LOW POUR POINT FRACTION, A MEDIUM POUR POINT FRACTION, AND A HIGH POUR POINT FRACTION, SUBSTANTIALLY CONGEALING AT LEAST A PORTION OF THE MEDIUM POUR POINT FRACTION AND OPTIONALLY A PORTION OF THE HIGH POUR POINT FRACTION, ADMIXING AT LEAST A PORTION OF THE HIGH POUR POINT FRACTION WITH THE LOW POUR POINT FRACTION AND THEREAFTER SLURRYING THE CONGEALED PARTICLES WITH THE LOW POUR POINT FRACTION TO OBTAIN A HYDROCARBON SLURRY SUITABLE FOR TRANSPORT AT PREDETERMINED TEMPERATURES.

3. The process of claim 1 wherein the slurry is transported in a pipeline.

6. The process of claim 1 wherein slurrying is effected at a temperature at least about 5* below the average solution temperature of the congealed fraction within the slurry.

7. The process of claim 1 wherein the medium pour point fraction is congealed at a temperature at least about 5* below its pour point.

8. The proceSs of claim 1 wherein the congelation is effected by prilling.

9. The process of claim 1 wherein the average diameter of the congealed fraction is about 0.05 to about 20 mm.

10. The process of claim 1 wherein the slurry contains up to about 10 percent by weight water.

11. The process of claim 1 wherein a hydrocarbon diluent is admixed with the hydrocarbon slurry to improve the pumpability thereof.

12. A process for preparing a hydrocarbon slurry from a ''''waxy'''' crude oil containing at least 25 percent wax (wax is defined as the precipitate which forms after 1 part of hydrocarbon mixture is dissolved in 10 parts of methylethyl ketone at about 80*C. and the mixture chilled to -25*C.) that can be effectively transported in a conduit, the process comprising fractionating the crude oil into at least a low pour point fraction, a medium pour point fraction and a high pour point fraction, substantially congealing at least a portion of the medium pour point fraction which can optionally contain at least a portion of the high pour point fraction, thereafter slurrying at least a portion of the congealed particles in the low pour point fraction which contains at least a portion of the high pour fraction to obtain a hydrocarbon slurry containing about 5 to about 55 percent by weight of the congealed particles and transporting the slurry in a conduit at a temperature below about the average pour point of the low pour point fraction.