US 3530042 A
Description (OCR text may contain errors)
Sept. 22, 1970 APPARATUS Filed Nov. 20, 1967 BITUMINOUS TAR SANDS WATER AND STEAM CONDITIONING DRUM SCREEN I 4 s I \0vERs|zE J. B. GRAYBILL ETAL AND CONTROL FOR HOT WATER PROCESS 2 Sheets-Sheet 1 DILUENT COMBINED FROTH PRIMARY FROTH gg RIFUGE 34 BIITUMEN PRODUCT SETTLED SCAVENGER SCAVENGER FROTH\ 4 I 24 1 O-22 WATER SEPARATION zomz SUMP MIDDLINGS '25 SAND mums FIGUREI OIL- RICH MIDDLINGS AIR FLO TATION ZONE OIL-LEAN MIDDLINGS l9 DENSITOMETER SAMPLE CELL SCAVENGER pt- 22, 1970 J. B. GRAYBILL ETAL 3,530,042
APPARATUS AND CONTROL FOR HOT WATER PROCESS Filed NOV. 20, 1967' 2 Shets-Sheet 2 FIGURE 2 I INVENTORS JAMES B; GRAYBILL CHESTER N; WHITE JUNIOR w; LOVELAND bMM TTORNEY United States Patent US. Cl. 19614.52 6 Claims ABSTRACT OF THE DISCLOSURE This invention relates to an apparatus and method for controlling the hot water process for the treatment of tar sands. The improvement in the process comprises introducing a portion of separation cell middlings into a sampling system, settling the middlings in the system, measuring the density of the settled middlings, and regu lating the water entering and leaving the process separation zone in response to these measurements so as to control the viscosity of the middlings in the zone. The apparatus used for controlling the viscosity of the middlings comprises a sample cell, a density sensing device, and regulating means responsively connected to the sensing device to control the water withdrawn from the separation zone.
This invention relates to an apparatus for controlling the hot water process for the treatment of tar sands. Large deposits of these sands are found as the Athabasca deposits in northern Alberta, Canada. The evaluated portion of these deposits occupies about five and one-half million acres and is buried by zero to 2000 feet of overburden. It has been estimated that these deposits consist of about 600 billion barrels of reserves in place, more than 350 billion barrels of recoverable reserves of raw tar sand oil and more than 250 billion barrels of upgraded synthetic crude oil.
The tar sands are primarily composed of a fine quartz sand having a particle size greater than that passing a 325 mesh screen. The quartz sand is impregnated with a viscous bitumen in quantities of from to 21 weight percent of the total composition. More typically the bitumen content is from 8 to percent. This bitumen is quite viscous 6 to 8 API gravityand contains typically 4.5 percent sulfur and 38 percent aromatics. Its specific gravity at 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 50 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 ma terial 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 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 dropped into a stream of circulating hot water 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 portion of the middlings from a hot ice 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 otf and the bitumen is coked to a high quality crude suitable for further processing.
The present invention relates to an apparatus and process for controlling the operation of the hot water process set out in Floyd et al., U.S. patent application Ser. No. 509,589. Floyd et a1. (now US. Pat. No. 3,401,110, issued Sept. 10, 1968) teach a hot water process for recovering additional bitumen in which the water incorporated with the bituminous sands for discharge into the separation cell and the rate of passage of the middlings from the separation cell to the scavenger step are both regulated in order to maintain the density of the middlings layer within the range of 1.03 to 1.50 and/or the viscosity of the middlings within the range of 0.56 to 10 centipoises.
The present invention relates to a means for controlling the process of Floyd et al. Floyd et .al. point out that bitumen froth recovery is affected by control of the viscosity of the middlings within a specified range. It has now been found that the viscosity of the middlings should be maintained within the range of about 0.4 to about 5.7 centipoises measured at F. with typical operation at about 1 to 2 centipoises at 190 F. As Floyd et al. point out, the viscosity is relatable to middlings clay content which can be maintained by regulating the amount water incorporated with the bituminous sands in an initial pulp forming stage and the rate of passage of the middlings from the separation cell to the scavenger step. It has now been found that middlings clay content is relatable to the settled density of the middlings where settled density is defined as measured density determined when mineral material which will not pass a 325 mesh screen has substantially settled out from the middlings sample. The viscosity of the middlings in the separation cell can be maintained within the desired range of about 0.4 to 5.7 centipoises by regulating the clay content of the middlings by maintaining the settled density of the middlings within the range of about 1.03 to 1.09 g./ml.
The present invention relates to a system for measuring the settled density of the separation cell middlings and for regulating water feed rates to the process in response to these measurements. Providing such a system poses a unique problem for the following reasons: (1) the composition of the material being handled is unique; (2) accuracy and speed of measurement are required; and (3) the response to these measurements must be reliable in order to smoothly control scavenger cell feed.
The middlings dragstream on which the measurements are to be run is typically comprised of about 1 to 5 weight percent bitumen, and 20 to 35 weight percent total mineral of which about 1 to 3 percent is clay. The density of the dragstream settled is typically between about 1.05 and 1.07 g./ml. at 190 F.
The process of this invention comprises introducing a water process separation cell into a sampling system. In the sampling system entrained sand is substantially removed by settling from the portion of the sample which is to be analyzed. The density of the sample is measured as the sample settles and the water incorporated into the tar sands and the stream to the scavenger zone from the separation cell are regulated in response to the measurement so as to maintain the viscosity of the middlings in the separation cell within the range of 0.4 to 5.7 centipoises or preferably about 1 to 2 centipoises.
The process of this invention may be best described with reference to the drawings. FIG. 1 shows a flow sheet of the hot water process utilizing the improved middlings control system of the present invention. FIG. 2 is a schematic representation of the particular apparatus used in the control system.
In FIG. 1, bituminous tar sands are fed into the system through line 1 where they first pass to a conditioning drum or muller 3. Water and steam are introduced 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 10 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 210 F. and preferably to above 170 F.
An alkali metal-containing 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 the separator zone within the range 7.5 to 9.0. Best results seem to be obtained at a pH value of 8.0 to 8.5. The amount of the alkaline reagent that needs to be added to maintain a pH value in the range of 7.5 to 9.0 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 alkali metal'containing alkaline reagents can be used if desired.
lVIulling of the tar sands produces a pulp which then passes from the conditioning drum as indicated by line 4 to a screen indicated at 5. The purpose of screen 5 is to remove from the tar sand pulp any debris, rocks or oversized lumps as indicated generally at 6. The pulp then passes from screen 5 as indicated by 7 to a sump 8 where it is diluted with additional water from 9 and a middlings recycle stream 10. This recycle stream serves to provide suflicient liquid to make the tar sands pulp pumpable so that it can be transferred to the separator.
Modifications that may be made in the process as above described include sending a minor portion of the middlings recycle stream from line 10 through a suitable line (not shown) to the conditioning drum 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 5 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 to 3.0 tons per ton of the bituminous sands. The amount of water needed within this range increases as the split clay content of the bituminous sands increases. For example, when percent 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 to 0.5 ton per ton of tar sands. On the other hand, when 30 percent of the mineral matter is below 44 microns diameter, generally 0.7 to 10 tons of water should be used per ton of tar sands.
With further reference to FIG. 1, the pulped and diluted tar sands are pumped from the sump 8 through line 11 into the separation cell 12. The cell contains 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 13 and a sand tailings which settles to the bottom to be withdrawn through line 14. An aqueous middlings layer between the froth and tailings layer contains silt and clay and some bitumen which failed to form froth. Since suflicient clay is not removed in the sand tailings withdrawn from the bottom of the separation cell through line 14 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, the viscosity of the middlings layer will increases. 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. This is avoided by regulating the recycling and withdrawal of middlings and input of fresh water per the present invention. Even when the separation step is operating properly the middlings layer withdrawn through line 15 will contain a substantial amount of bitumen which did not separate. Hence the middlings layer withdrawn through line 15 is, for purpose of description, herein referred to as oil-rich or bitumenrich middlings.
The amount of bitumen removed in the oil-rich middlings layer is related to the percentage of clay and/0r silt present in the tar sands being processed, varying directly with the amount of clay and/ or silt present. For example, typical bitument recovery values for primary froth from tar sands in which 15 percent of the mineral matter is less than 44 microns and from sands in which 25 to 30 percent is less than this size are respectively percent and 60 percent. For commercial operation it is highly desirable to obtain increased froth yield in the separation zone over such vanes as those which are obtainable 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 bitumen-rich middlings stream withdrawn from the separator 12 through line 15 is sent to a scavenger zone 16 wherein an air flotation operation is conducted to cause the formation of additional bitumen froth. A sample of the middlings is withdrawn from the separation cell 12 and is conducted via line 17 to a sample cell 18.
In the sample cell 18 sand is allowed to settle from the sample and a settled density measurement is taken by means of the densitometer 19. The densitometer 19 controls variable speed pump 20 on line 15 so that if the settled density of the sample withdrawn from the separation cell 12 registers above the range 1.03 to 1.09, lead 21 increases the variable speed pump 20 thereby increasing the flow in line 15 to the scavenger cell 16. Increased flow to the scavenger cell 16 lowers the interface level between the middlings and froth in the separation cell 12. The lowering of the interface level actuates float valve 22 which by means of lead 23 opens valve 24 thus increasing the flow of fresh water addition to the sump 8 via line 9. Increased water flow through line 9 results in increased water content in the diluted pulp passing from the sump 8 through line 11 to the separation cell 12. Flow through pump 25 is decreased via lead 26 which responds to the increase in water in the diluted pulp thereby resulting in a reduction in the amount of middlings recycle diluting the separation cell feed via 10. Thereby the proportion of fresh water in the separation cell 12 is increased, bringing about a decrease in middlings density. Corre spondingly, if the settled density of the sample withdrawn via line 17 registers below the operation range of 1.03 to 1.09, lead 21 decreases the variable speed pump 20 thereby decreasing the flow in line 15 to the scavenger cell 16. Decreased flow to the scavenger cell raises the interface level in the separation cell 12. A raising of the interface level actuates float valve 22 which by means of lead 23 closing valve 24 thus decreasing the flow of fresh water addition to the sump via line 9. Decreased water flow through line 9 results in decreased water content in the diluted pulp passing from the sump 8 through line 11 to the separation cell 12. Flow through pump 25 is increased via lead 26 which responds to the decrease in Water in the diluted pulp in 11 thereby resulting in an increase in the amount of middlings recycle diluting the separation cell feed. Thus the proportion of fresh water in the separation cell 12 is decreased bringing about an increase in middlings density. The system can be operated so as to maintain the middlings density within the preferred range of 1.05 to 1.07 instead of the broad range as described supra.
Following the process further, in the scavenger zone 16 an air flotation is conducted 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 elfected 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 amounts. 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 16 through line 27 to a froth settler zone 28. An oil-lean middlings stream is removed and discarded from the bottom of the scavenger zone via line 29.
In the settler zone 28, the scavenger froth forms into a lower layer of settler tailings which is withdrawn and recycled via line 30 to be mixed with bitumen-rich middlings for feed to the scavenger zone 16 via line 15. In the settler zone 28 an upper layer of upgraded bitumen froth forms above the tailings and is withdrawn through line 31 and mixed with primary froth from line 13 for further processing.
The combined froths are at a temperature of about 160 F. They are heated with steam and diluted with sulficient naphtha or other diluent from 32 to reduce the viscosity of the bitumen for centrifuging in zone 33 to produce a bitumen product 34 suitable for further processing.
Referring again to the drawings, FIG. 2 schematically illustrates the apparatus and system of the present invention. FIG. 2 shows the apparatus and system utilizing a radiation density gauge but it should be noted that any density sensing device can be used in the present invention in place of the radiation gauge. The apparatus consists of a sampler cell 18 which in the drawing is a vertical standpipe. The sampler is located adjacent to the hot water process middlings separation cell 12 (not shown) and is connected thereto by a line 17, which is equipped with an inlet valve 35. The sampler standpipe 18 is equipped with an outlet valve 36 and an emergency overflow drain line 37. A density sensing and measuring means is located at the top of the sampler as generally indicated by 19 in FIG. 1. In FIG. 2 this means consists of a radiation density gauge comprising a radiation source 38, a radiation measuring means 39 and an amplifier, indicator and recorder indicated at 40. This amplifier, indicator and recorder 40 control valve 20 of FIG. 1 via lead 21. A float valve 41 is located within the upper standpipe 18. This float valve 41 is responsive to the liquid level in the pipe. When the liquid reaches a certain level the valve actuates a float switch 42 which closes valve 35 stopping middlings flow. in 17 from the separation cell.
The operation of the particular apparatus shown in FIG. 2 is described as follows:
Valve 35 opens and allows a middlings sample to flow from the separation cell 12 via line 17 to the sampler 18. The sample is fed into the sampler standpipe 18 where it is trapped and allowed to settle. When the liquid fills the standpipe 18 it raises the float valve which actuates the float switch 42 which then closes the input valve 35 stopping sample flow from the separation cell. Settled density is then measured by means of the. density sensing means indicated by 38, 39 and 40 described supra. The density amplifier, indicator and recorder 40 then actuates valve 20 (shown in FIG. 1) by means of lead 21 as described supra. Settled density is read batchwise for the elapse of each cycle. The bottom outlet valve 36 is then opened and the sample is dumped. The cycle is then repeated. If the input valve 35 should fail to close or the bottom valve fail to open, excess sample would flow from the sampler 18 via the emergency overflow line 37.
As mentioned supra the drawing, FIG. 2, shows the apparatus and system of the present invention utilizing a radiation density gauge. This gauge is the preferred density measuring device for this apparatus but other devices can be used in the invention. The operation of the radiation density detector shown will be described in more detail.
The source unit 38 contains a radiation emitting substance such as the radioisotope cesium 137 which emits gamma rays. The source holder is designed so that the rays enter the sample as a beam of parallel rays. The ease with which the rays from a given source penetrate a solid or liquid depends upon the density of the material; the more dense the material the less the penetration. As the fines content of the middlings sample increases, its density increases and this increase in density decreases the intensity of the radiation reaching the measuring cell 39 which is situated on the standpipe 18 opposite the radioactive source. If the fines content of the middlings decreases, its settled density decreases and the radiation reaching the measuring cell 39 increases.
The measuring cell 39 functions to detect the quantity of radiation penetrating the standpipe and sample. The radioactive energy is translated to electrical energy which is transmited to the remote amplifier, indicator and recorder 40. Here the electrical signal from. the measuring cell is amplified to operate a meter to provide visual indications of sample settled density. A recorder connection can also be provided on the amplifier-indicator.
Viscosity control of separation cell middlings can be maintained by manual adjustment of valve 20 as indicated by the density meter on the amplifier 40. However it is preferred to operate this valve automatically according to settled density readings. The settled density measurements are made batchwise and provide an intermittent electrical signal representing density. As such this signal is not best suited for automatic control purposes. A memory unit can be provided as part of the density sensing means to hold the signal from one batch measurement on over to the next measurement to provide a smooth constant control on the valve 20 via lead 21 to provide middlings viscosity control.
What is claimed is:
1. An apparatus for measuring settled density of the middlings in a hot water process separation zone which comprises:
(a) a sample cell comprising a vertical cell, provided with a discharge outlet at the bottom of said cell and a feed inlet at the side of said cell connected to said separation zone for feeding a middlings sample from said zone to said cell; a weir box positioned at the top of said cell to collect overflow from said cell; a float valve positioned in said weir box; a float switch responsively attached to said float valve so that said valve actuates said switch when said valve is raised to an upper position in said weir box; and an inlet valve located on said feed inlet and responsively connected to said float switch to close when actuated by said switch when said switch is actuated by said float valve;
(b) a density sensing device located on said sample cell for measuring the density of a settled middlings sample contained in said cell; and
(c) regulating means responsively connected to said density sensing device to control the withdrawal of a stream of middlings from said separation zone.
2. The apparatus of claim 1 in Which said density sensing device comprises a radiation density detector comprising a radiation source, a radiation measuring means positioned with respect to the said source to measure radiation from said source and an amplifier, indicator and recorder unit connected to said measuring means to translate radiation measurements to electrical energy which actuates said regulating means (c).
3. In a system for conducting a hot water process for treating tar sands comprising a conditioning drum; a separation cell; a first line for suppling tar sands pulp from said conditioning drum to said separation cell; a second line for introducing hot water into tar sands pulp in said first line; a third line for withdrawing a bitumen froth product from said cell; a fourth line for withdrawing a sand tailings layer from said cell; a fifth line for withdrawing a middlings portion from said cell; a sixth line for recycling a middlings portion from said cell to be mixed with said tar sand pulp prior to discharge into said cell; the improvement which comprises:
(a) a sampling device for withdrawing a sample of middlings from said cell to measure settled density thereof comprising a vertical cell provided with a discharge outlet at the bottom of said vertical cell and a feed inlet at the side of said vertical cell connected to said separation zone for feeding a middlings sample from said zone to said vertical cell; a weir box positioned at the top of said cell to collect overflow from said cell; a float valve positioned in said Weir box; a float switch responsively attached to said float valve so that said valve actuates said switch when said valve is raised to an upper position in said weir box; and an inlet valve located on said feed inlet and responsively connected to said float switch to close when actuated by said switch when said switch is actuated by said float valve;
('b) a density sensing device connected to said sampling device for measuring the settled density of said sample;
(c) regulating means controllably attached to said fifth line, and responsively connected to said density sensing device to control the middlings portion withdrawn via said fifth line;
(d) regulating means operating in response to said middlings withdrawn in said fifth line and connected to said second line to control the hot water intro- 8 duced to the bituminous tar sands pulp via said second line; and
(e) regulating means operating in response to said hot water incorporated in said second line and connected to said sixth line to control the middlings portion recycled to the bituminous tar sands pulp via said second line.
4. The system of claim 3 in which said density sensing device (b) comprises a radiation density detector comprising a radiation source, a radiation measuring means positioned with respect to the said source to measure radiation from said source and an amplifier, indicator and recorder unit connected to said measuring means to translate radiation measurements to electrical energy which actuated said regulating means (c) and (d).
5. The system of claim 3 in which said regulating means (c) is responsively connected to said density sensing device so as to increase the viscosity of said middlings in' said separation cell when said middlings viscosity is below 0.4 centipoise and so as to decrease the viscosity of said middlings in said separation cell when said middlings viscosity is above 5.7 centipoises.
6. The system of claim 3 in which said regulating means (c) is responsively connected to said density sensing device so as to increase the viscosity of said middlings in said separation cell when said settled middlings density is below 1.03 g./ml. and so as to decrease the viscosity of said middlings in said separation cell when said settled middlings density is above 1.09 g./ml.
- References Cited UNITED STATES PATENTS 2,903,407 9/1959 Fischer et a1. 208-11 3,004,544 10/1961 Guptill 137-1 3,009,359 11/1961 Hubby 73-438 3,014,362 12/1961 True et a1. 73-53 3,161,203 12/1964 Hathorn et a1 137-91 3,229,503 1/1966 Poole et al. 73-32 3,246,145 4/1966 Higgins 250-435 3,255,881 6/1966 Holderreed et al. 250-435 3,401,110 9/1968 Floyd 208 11 FOREIGN PATENTS 985,097 3/1965 Great Britain.
PAUL M. COUGHLAN, ]R., Primary Examiner T. H. YOUNG, Assistant Examiner US. Cl. X.R.