US3509641A - Tar sands conditioning vessel - Google Patents

Description

y 1970 M. R. SMITH ETAL 3,509,641

TAR SANDS CONDITIONING VESSEL Filed May 17, 1968 5 SheetsSheet 1 FIGURE l DILUENT CENTRIFUGE ZONE BITUMEN PRODUCT COMBINED 24 FROTH\ TAR SANDS I I SETTLED SCAVENGER WATER /FROTH l5 2 PRIMARY 23 FR0TH\ FROTH conmnonms LER DRUM \ SCAVENGER FROTH\ OVERSIZE [:1 2 SEPARATION 2 ZONE AIR MIDDLINGS FLOTATION SCAVENGER 21 m ZONE OIL-LEAN MIDDLINGS SAND TAILINGS May 5, 1970 s n' ETAL TAR SANDS CONDITIONING VESSEL 3 Sheets-Sheet 2 Filed May 17. 1968 N mEDQI y 5, 1970 M. R. SMITH ETAL 3,509,641

TAR SANDS CONDITIONING VESSEL Filed May 17, 1968 3 Sheets-Sheet 5 FIGURE 3 United States Patent 3,509,641 TAR SANDS CONDITIONING VESSEL Marshall R. Smith, Fort MacMurray, Alberta, Canada, and Frederick W. Camp, West Chester, and George H. Evans, Wallingford, Pa., and Jack D. Tinkler, Claymont, Del., assignors to Great Canadian Oil Sands Limited, Toronto, Ontario, Canada, a corporation of Canada Filed May 17, 1968, Ser. No. 729,970 Int. Cl. E26b 23/10 US. Cl. 34-134 2 Claims ABSTRACT OF THE DISCLOSURE The specification discloses a conditioning drum designed specifically for producing a pulp by mulling tar sands with steam and water. The pulp is used in a hot water process for separating bitumen from tar sands. The conditioning drum comprises a cylindrical drum rotatable around its longitudinal axis and a sparge valve disposed at one end of the drum for receiving steam. The sparge valve comprises a rotatable outer sleeve with a plurality of ports spaced along its circumference and a stationary seat of circular cross section with at least one port at its lower portion. The valve conducts steam through the spaced sleeve ports only when they are in line with the seat ports. The drum also contains a plurality of steam conduits adjacent the drum wall extending longitudinally inside the drum from the ports in the sparge valve sleeve. The conduits rotate with the drum and valve sleeve and receive steam from the valve. The steam is injected into the tar sands in the drum through perforations in the conduits. If desired, pitched retarder blades can be mounted on the inside circumference of the drum for controlling the forward flow of material therethrough.

This invention relates to a conditioning drum for conditioning or mulling tar sands. The drum comprises a cylinder with a sparge valve connected at one end. The sparge valve receives steam from an outer source and conducts it to a plurality of steam conduits. The steam conduits run longitudinally inside the drum, adjacent to the drum wall, and are perforated for transferring steam into the material being mulled in the drum. The conduits are connected to the sparge valve and the sparge valve is constructed in such a manner that steam is injected into the conduits only when they are submerged in the material being mulled.

The invention is specifically utilized for conditioning and mulling tar sands with steam and water to form a pulp in a hot water process. Tar sands comprise a fine quartz sand impregnated with a viscous bitumen in quantities of from 5 to 21 weight percent of the total compo sition. More typically the bitumen content is from 8 to percent. This bitumen is quite viscous6 to 8 API gravity-and contains typically 4.5 percent sulfur and 38 percent aromatics. Its specific gravity at 60 F. ranges typically from about 1.00 to about 1.06.

In addition to the bitumen and quartz sand, the tar sands contain clay and silt in quantities of from 1 to weight percent of the total composition. Silt is normally defined as material which will pass a 325 mesh screen but which is larger than 2 microns. Clay is material smaller than 2 microns including some siliceous material of that size.

Several basic extraction methods have been known for many years for the separation of bitumen from the sands. In the so-called cold water method, the separation is accomplished by mixing the sands with a solvent capable of dissolving the bitumen constituent. The mixture is then introduced into a large volume of water, water with a 'ice surface agent added, or a solution of a neutral salt in water. The combined mass is then subjected to a pressure or gravity separation.

In the hot water method, the bituminous sands are jetted with steam and mulled with a minor amount of hot water at temperatures in the range of to 210 F. The resulting pulp is screened, diluted and carried to a separation cell maintained at a temperature of about to 200 F. In the separation cell, sand settles to the bottom as tailings and bitumen rises to the top in the form of an oil froth. An aqueous middlings layer containing some mineral and bitumen is formed between these layers. A scavenger step may be conducted on the middlings layer from the primary separation step to recover additional amounts of bitumen therefrom. This step usually comprises aerating the middlings as taught by K. A. Clark, The Hot Water Washing Method, Canadian Oil and Gas Industries 3, 46 (1950). These froths can be combined, diluted with naphtha and centrifuged to remove more water and residual mineral. The naphtha is then distilled off and the bitumen is coked to a high quality crude suitable for further processing.

It is essential to best operation of the hot water process, that the tar sands be intimately contacted with steam and water in the initial mulling stage and that adequate agitation be applied to the mixture of tar sands and water to produce a pulp with a fairly uniform distribution of water. Proper contact of the sands with steam and Water and proper mulling of the pulp is essential so that initial displacement of the sand particles from the bitumen can take place through the relative preferential aflinity of the sand particles for water.

The physics of the separation of the bitumen requires that, in order to float, the bitumen be freed from most of the mineral and contain enough gas to make the particles less dense than water. Also, the particles must be larger than 30 microns diameter in order to float in the time allowed. One observable effect of increased clay in tar sands is to make the particles of oil smaller. When the sands are not conditioned properly these flecks remain in the water-clay layer.

The conditioning drum of the present invention provides an apparatus for the proper agitation of sands. The apparatus is uniquely designed for achieving the above objectives for the proper mulling of tar sands to produce a pulp amenable to bitumen froth formation in the su: sequent separation step. This drum comprises a cylinder, mounted with the longitudinal axis approximately horizontal. The drum is rotatable around its longitudinal axis. A sparge valve is positioned at one end of the drum for transferring steam from an external source to steam conduits Within the drum. The valve comprises a rotatable outer sleeve with a plurality of ports arranged along the outer sleeve circumference. The sleeve rotates around a stationary seat of circular cross section. The seat has one or more ports at its lower portion for conducting steam into the sleeve ports when the sleeve ports are in line with the seat ports. Steam enters the valve through the seat, passing through the seat ports, through the sleeve ports, and into the steam conduits which have a plurality of perforations for injecting steam into the drum. The steam conduits are arranged inside the drum adjacent to the wall, extending longitudinally with the drum. The perforations in the conduits can be circular openings, longitudinal slits or whatever shaped and sized perforations desired. Since the conduits are connected to the valve sleeve, each conduit receives steam from the valve only when the sleeve port is aligned with a seat port. The seat ports are spacedso that this occurs only when the conduit is immersed in the material being treated. This arrangement uniquely provides for the proper type of intimate contact between steam and tar sands, necessary to produce a pulp of the desired characteristics.

As discussed supra, producing a good pulp by proper treatment requires not only intimate contact between the tar sands and steam but also adequate mulling to provide good disintegration. Another aspect of the present invention is a conditioning drum which has been found to be far superior over other types of drums for producing tar sands pulp. This drum comprises a cylindrical drum with retarder blades pitched so as to impede the forward flow of material through the drum so as to tend to return the material to the feed end. This type of arrangement provides the additional residence time necessary for proper disintegration of tar sands lumps. The retarder blades are mounted in rows on the circumference of the drum and will be described more in detail infra with reference to the drawings.

FIGURE 1 of the drawings is a schematic representation of the hot water process in which the conditioning drum of the present invention is best utilized. FIGURE 2 is an elevation view, in section, of the conditioning drum. FIGURE 3 is a sectional view of the drum along the line, A-A of FIGURE 2.

In FIGURE 1, bitumious tar sands are fed into the system through line 1 where they first pass to the conditioning drum or muller which is indicated generally by 18. The muller comprises the conditioning drum of the present invention and will be described in more detail with reference to FIGURES 2 and 3 of the drawings. Water and steam are introduced into the drum from 2 and mixed with the sands. The total water so introduced is a minor amount based on the weight of the tar sands processed and generally is in the range of to 45 percent *by weight of the mulled mixture. Enough steam is introduced to raise the temperature in the conditioning drum to within the range of 130 to 190 F. and preferably at least to 170 F. A monovalent alkaline reagent can also be added to the conditioning drum usually in amount of from 0.1 to 3.0 lbs. per ton of tar sand. The amount of such alkaline reagent preferably is regulated to maintain the pH of the middlings layer in separator zone 21 within the range of 7.5-9.0. Best results are obtained at a pH value of 8.0-8.5. The amount of the alkaline reagent that needs to be added to maintain a given pH value in the range of 7.5-0.0 may vary from time to time as the composition of the tar sands as obtained from the mine site varies. The best alkaline reagents to use for this purpose are caustic soda, sodium carbonate or sodium silicate, although any of the other monovalent alkaline reagents can be used if desired.

Mulling of the tar sands produces a pulp which then passes from the conditioning drum as indicated by line 3 to a screen indicated at 19. The purpose of screen 19 is to remove from the tar sand pulp any debris, rocks or oversized lumps as indicated generally at 4..

The pulp then passes from screen 19 as indicated by 5 to a sump 20 where it is diluted with additional Water from 6 and a middlings recycle stream 7. Recycling of the middlings is not essential in all cases, particularly when the clay content of the tar sands is high. In this event a relatively high rate of fresh feed water introduction through 6 can be employed to compensate for the high clay content while a correspondingly high rate of transfer of middlings layer through line 11 as hereinafter described can be maintained. Under these circumstances recycling of the other stream of middlings through line 7 to the sump is not required.

Modifications that may be made in the process as above described include sending a minor portion of the middlings recycle stream from line 7 through a suitable line (not shown) to the conditioning drum 18 to supply all or a part of the water needed therein other than that supplied through condensation of the steam which is consumed. Also, if desired, a stream of the middlings recycle can be introduced onto the screen 19 to flush the pulp therethrough and into the sump. As a general rule the total amount of water added to the natural bituminous sands as liquid water and as steam prior to the separation step should be in the range of 0.2-3.0 pounds per pound of the bituminous sands. The amount of water needed within this range increases as the silt and clay content of the bituminous sands increases. For example, when 15% by Weight of the mineral matter of the tar sands has a particle size below 44 microns, the fresh water added generally can be about 0.3-0.5 pounds per pound of tar sands. On the other hand, when 30% of the mineral matter is below 44 microns diameter, generally 0.7-10 pounds of water should be used per pound of tar sands. Correspondingly, the amount of oil-rich middlings removed through line 11 will vary depending upon the rate of fresh water addition. As a general rule the rate of withdrawal of oil-rich middlings to scavanger zone 22 will be 10-75 gallons per ton of tar sands processed when 15% by weight of the mineral matter is below 44 microns and 150-250 gallons per ton when from 25-30% of the mineral is of this fine particle size.

Further following the process, the pulped and diluted tar sands are pumped from the sump 20 through line 8 into the separation zone 21. The separation zone comprises a settling cell containing a relatively quiescent body of hot water which allows for the formation of a bitumen froth which rises to the cell top and is withdrawn via line 9, and a sand tailings layer which settles to the bottom to be withdrawn through line 10. An aqueous middlings layer forms between the froth and tailings layer. This layer contains silt and clay and some bitumen which failed to form froth. In order to prevent the buildup of clay in the system it is necessary to continually remove some of the middlings layer and supply enough water in the conditioning operations to compensate for that so removed. The rate at which the middlings need to be removed from the system depends upon the content of clay and silt present in the tar sands feed and this will vary from time to time as the content of these fines varies. If the clay and silt content is allowed to build up in the system, both the density and the viscosity of the middlings layer will increase. Concurrently with such increase an increase in the proportions of both the bitumen and the sand retained by the middlings will occur. If the clay and silt content is allowed to build up too high in the system, effective separation no longer will occur and the process will become inoperative. Inoperability can be avoided by regulating the recycling and withdrawal of middlings and input of fresh water per the invention disclosed and claimed in the Floyd et al. US. application Scr. No. 509,589 filed Nov. 24, 1965 now U.S. Patent No. 3,401,- 110 issued Sept. 10, 1968, Canadian application No. 975,767. However, even when the separation step is operating properly the middlings layer withdrawn through line 11 will contain a substantial amount of bitumen which did not separate. Hence the middlings layer withdrawn through line 11 is,.for purpose of description herein referred to as oil-rich middlings, or bitumen-rich middlings.

The amount of bitumen remaining in the middlings layer appears to be more or less related to the percentage of clay and/or silt present in the tar sands being processed, varying directly with the amount of clay and/or silt present. For example, typical oil recovery values for the froth from tar sands in which 15% of the mineral matter is less than 44 microns and from sands in which 25-30% is less than this size are respectively, and 60%. For commercial operation it is highly desirable to obtain increased recoveries over such values as these which are obtained heretofore by the hot water process. This is particularly true when the tar sands as mined contain a relatively high proportion of clay and silt components.

The oil-rich middlings stream withdrawn from separator 21 through line 11 is sent to a scavenger zone 22 wherein an air flotation operation is conducted to cause ing formation of additional bitumen froth. The processing conducted in the scavenger zone involves air flotation by any of the air flotation procedures conventionally utilized in processing of ores. This involves providing a controlled zone of aeration in the flotation cell at a locus where agitation of the middlings is being effected so that air becomes dispersed in the middlings in the form of small bubbles. The drawing illustrates a flotation cell of the sub-aeration type wherein a motorized rotary agitator is provided and air is fed thereto in controlled amount. Alternatively the air can be sucked in through the shaft of the rotor. The rotor effects dispersion of the air in the middlings. This air causes the formation of additional bitumen froth which passes from the scavenger zone 22 through line 12 to a froth settler zone 23. An oil-lean middlings stream is removed and discarded from the bottom of the scavenger zone 22 via line 13.

In the settler zone 23, the scavenger froth forms into a lower layer of settler tailings which is withdrawn and recycled via line 14 to be mixed with oil-rich middlings for feed to the scavenger zone 22 via line 11. In the settler zone an upper layer of upgraded bitumen froth forms above the tailings and is withdrawn through line 15 and mixed with primary froth from line 9. The use of gravity settling to upgrade scavenger cell froth is disclosed and claimed in Dobson, US. patent application Ser. No. 627,958, filed Apr. 3, 1967. The combined froths are at a temperature of about 160 F. They are heated with steam and diluted with suflicient naphtha or other diluent from 16 to reduce the viscosity of the bitumen for centrifuging in zone 24 to produce a bitumen product 17 suitable for further processing.

Referring to FIGURE 2 there is shown the conditioning drum which is the subject of the present invention and which was indicated generally in FIGURE 1 as 18. The drum includes a cylindrical drum 25 which is rotatable about its longitudinal axis. The feed end of the drum is indicated generally at 26 and pulp discharge is indicated at 27. The main steam line is indicated at 28. The steam line 28 introduces steam to the sparge valve 29. The sparge valve transfers the steam to steam conduits 30 which are perforated (not shown) for providing initimate contact of the steam with tar sands. Feed flights for pushing the feed away from the entry port and into the drum are indicated at 31, and are provided with knife blades 32 for breaking up large tar sand lumps. Pitched retarder blades shown at 33 are mounted in rows on the drum circumference. The blades are pitched to kick the lumps back toward the feed end of the drum. The blades increase lump residence time and insure thorough disintegration of tar sand lumps and intimate contact of the sands with hot water introduced via the feed end 26 and with steam from the steam conduits 30. These blades are an optional feature of the present invention. If the drum is provided with blades, residence time of the tar sands in the drum can be controlled by spacing alteration or pitch variation. The drum is also provided with a rock ejector 34 for discarding rocks and large lumps of sands which pass through the drum without disintegrating.

FIGURE 3 is a sectional view of the conditioning drum from the line AA of FIGURE 2. The figure shows the cylindrical drum 25, and the sparge valve 29. The sparge valve comprises stationary seat 37 of circular cross section with a port 38 at its lower circumference and an outer sleeve with sleeve ports 36 connected to steam conduits 30.

The following description of the mulling operation illustrates the invention.

On an hourly basis sufficient amount of tar sands to give 1000 tons in the feed after screening is fed along with hot water into the conditioning drum feed end 26. In the drum the sands are mulled by the rotating action of the drum and the impact of the retarders 33. The retarders are pitched to tend to direct the tar sand lumps back to the feed end so as to increase residence time of the lumps in the drum to insure intimate mulling with the feed water and steam which is injected into the sands from the steam conduits 30. At the same time the retarders allow relatively free passage of properly mulled pulp to the discharge end. The total amount of steam and water added to the sands during mulling is about 300 tons. The steam conduits 30 inject steam into the drum only when the conduits are submerged in the mulling mixture, i.e., only when the conduits are at the lowperiod of their rotation with the drum. This is made possible by the sparge valve 29 the stationary seat 37 of which is provided with steam ejection port 38 only at its lower circumference. Steam passes from the steam inlet through seat port 38, sleeve ports 36, to conduits 30 only when the sleeve ports 36 to the conduits are in line with seat port 38 so that steam passes only to those conduits which are, at any moment in rotation, near the bottom of the drum. The thoroughly mulled pulp of water and tar sands is ejected from the drum via the pulp discharge 27 to the screen 19 where any remaining debris, rocks or oversized lumps are removed. The pulp then passes through the process as described supra with reference to FIGURE 1. This description illustrates the thorough mulling of tar sands to produce pulp provided by the apparatus of the present invention.

What is claimed is:

1. A tar sand conditioning vessel comprising:

(a) a cylindrical vessel rotatable around its longitudinal axis, said vessel having at least one axial opening at each end whereby solid materials to be conditioned can be fed into one end of said vessel and extracted from the opposite end of said vessel by way of said openings;

(b) a sparge valve disposed at one end of said vessel for receiving steam and comprising a rotatable outer sleeve with a plurality of ports spaced along the circumference of said sleeve and a stationary seat of circular cross section with at least one port at the lower portion of said seat for conducting steam through said sleeve ports when said spaced ports are in line with said seat ports; and

(c) a plurality of steam conduits adjacent to the vessel wall extending longitudinally therein and from the ports in said sparge valve outer sleeve to rotate therewith and receive steam therefrom, said conduits being perforated for injecting steam from said valve into the interior of said vessel.

2. The vessel of claim 1 additionally comprising pitched retarder blades mounted in rows on the inside circumference of the said cylindrical vessel for controlling the forward flow of material through said vessel.

References Cited UNITED STATES PATENTS EDWARD 1. MICHAEL, Primary Examiner

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