CA1081559A - Silicone release agent for bituminous sands conveyor belt - Google Patents

Abstract

"SILICONE RELEASE AGENT FOR BITUMINOUS SANDS CONVEYOR BELT" A water-based emulsion with silicone fluid as the dispersed phase, wherein said fluid is a silicone polymer of short chain length having a viscosity of around 100 centistokes and having hydroxyl terminal groups, is useful, when spread over the load-bearing surface of a conveyor carrying bituminous sands, to act as a release agent to promote the clean separation of the tacky sands from the belt when the latter rounds the end roller of the conveyor system and unloads the sands.

Description

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This invention relates to a method which com-prises treating the load-bearing surface o the endless belt of a conveyor system with a release agent which is operative to cause bituminous sands subsequently deposited on the belt to separate cleanly therefrom when the belt rounds the end roller of the system.
The invention finds application with respect to a conveyor belt of nitrile or other rubber composition used to convey bituminous sands from a storage bin to a hot water process extraction circuit for recovering bitumen from the sands.
Bituminous sands, ~hen dropped onto a conveyor belt from a height o~ several feet/ tend to adhere to the belt surface when it rounds the ~nd roller. Some of the adhering sands remain attached to the belt and build up on it to form an uneven load thereon. Other portions of the sands drop off the belt as it returns to the starting point of the system.
To give some idea of the magnitude o~ this latter problem, in the 125,0Q0 barr~ls of bitumen produced per day facility being constructed by the assignees of this invention, it is estimated that, in the absence of a suitable release agent, a deposit of tar sand 17 feet high ~ould be generated be-neath the conveyor beIt each day~ Indeed, provision has been made to permit mechanical shovels to drive beneath the con-veyor belt to remove this material.
f ~ut of doors, the problem has been solved by applying a liquid hydrocarbon, such as diesel fuel, to the belt surface before the sands are deposited thereon. However, this prior art belt release agent cannot be used on the conveyor belt connecting the storage bin and the conditioning .

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drum in a hot water process extraction plant, as the belt is housed and the danger of ire or an explosion is too great.
In seeking a release agent for use on -this belt, a set of criteria which the agent must satisfy has been developed. More particularly, the release agent must:
(a) when applied to the belt in moderate volume, effectively cause the sands to release from the belt surface when it is unloading at the end roller;
(b) be non-flammable;
(c) not be harmful to the hot water extraction process;
(d) not be harmful to the conveyor belt material nor render repair difficult should damage occur to the belt; and (e) be non-toxic and non-corrosive.
SUMMARY OF THE INVE~ITION
In accordance with the invention, it has been ound that an emulsion of a certain class of silicone fluid dispersed in water, when spread over the load-bearing surface of a conveyor belt which is to transport bituminous sands, is a satisfactory release agent for use on the belt. Preferably the release agent should contain at least 1000, and most prefer-ably about 5,000 parts of silicone emulsion per million parts of water. It has been further observed however, that the surface of the conveyor retains much of the silicone so that after a short time the surface becomes conditioned, with the result that lower concentrations of the emulsion may be used.
Although silicone fluids of various types, when used as the disperse phase in water-based em~lsions, are ef-fective release agents, most are ruled out ~ecause their presence ~B 3 -81SS9 '~

in the hot water extraction process is deleterious to that process. Satisfactory siIicone fluids are charac~erized by the following:
(a) short polymer chain, such tha~ the vis-cosity of the fluid is preferably around 100 centistokes; and , (b) polymer chains terminated with hydroxyl groups.
Two such silicone emulsions are Dow Corning* 347, mar~eted by Dow Corning Ltd., Downsview, Ontario, and L-900, marketed by Union Carbide* Canada Ltd~, Calgary, ~lberta~
Broadly stated, the invention is an improvement of the process wherein bituminous sands are deposited on and transported by an endless conveyor belt to its end where the sands are unloaded as the ~elt rounds the end roller. The `
improvement comprises treatin~ the sands-bearing surface of the belt with a water-based emulsion, having as the disperse phase a silicone 1uid having short polymer chains which are hydroxyl terminated, prior to depositing the bituminous sands thereon, to provide a release agent which is operative to effect clean separation of the sands ~rom the surface during the unloading operation.
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DESCRIPTION OF THE P~EFE~P EMBODIMENT
The invention has been developed by subjecting a broad range of compounds to one or both of two tests, namely:
(1) a tar sand release efficiency test; and (2) a test to determine whether the use of the compound would have a seriously deleterious effect on the hot water extraction.
The test apparatus for release efficiency I .

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comprised a 15 ton punch press assembly. The original die set was replaced with a spring-loaded adapter designed to ac-commodate belting samples. A number of 6 x 6 x 1/8 inch samples of Goodyear* Rubber Company B3835 neoprene belt sur-facing material were used for testing. Each sample or blockof belt material was fastened in place on the adapter by means of a recessed retaining clamp to provide an exposed area of 25 sq. in. Activation of the punch press trigger mechanism forced the belt sample downward onto a tray of bituminous sands directly beneath. By maintaining a con-sistent depth o~ sands in the tray, pressure exerted was regulated by the spring tension in the adapter. Preliminary testing yielded optimum reproducibility of results at 8.8 psi with a total of nine impacts. Lateral movement of the tray allowed three repeated stamps over each of three locations on the sands bed.
The tray was filled with homogenized bituminous `
sands to a depth of 1.5 inches and levelled by guiding a straight edge along its rim. Compressed sand was discarded after each test and replenished with freshly chopped material.
Precoat materials requiring dissolution in an aqueous media were applied in aerosol form until the entire belt surface was wetted.
Tests ~ere conducted at ambient room temperature.
Belt samples were weighed before and after impacts. Values for weights of bituminous sand adhering were compared to blank determinations (employing untreated belt samples) and ex-pressed as a release efficiency.
The effect on hot water extraction of release agents which were successful in the release efficiency test was tested in a laboratory-scale batch extraction apparatus.

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This apparatus had been u~ed for other studies for application at the commercial level. ~ituminous sand was extracted with-out, and in t~e presence o~, the compounds or formulations proposed for use as release agents.
The extraction apparatus comprised a 2 litre capacity stainless steeI vessel jacketed in a steel shroud to ~`
allow passage of heat-ing water between the vessel and jacket.
The vessel ~as fitted with a driven impellor for stirring the vesseI contents. Bituminous sands and belt release agent were introduced together with slurry ~ater into the vessel.
This mixture ~as stirred therein ~or a period of time;
then additional flood water ~as added and the flotation was carried out. Following are the details of operation.
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Combosit`ion o~f Mi-xture: Grams .
bituminous sands 500 hot water ~at 82C) - slurry 145 - floofl 955 belt release agent ~Q.10 ;
Impellor r.p.m. - 6Q0 Retention time - 10 min. slurry - 10 min. primary flotation Temperature within vessel - 82C
Froth was recovered by skimming and analyzed for bitumen, water and solids by Soxhlet extraction with toluene.
Following are results obtained during these tests with reference to siIicone emulsions:
Tar sand adhering in presence of release agent x 100 Y Tar Sand adher1ng without release agent ;~.

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~OBlSS9 .

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TABLE I - Belt Release Ef~ic:iency _ ~elease Efficiency Medium Grade Rich Grade ConcentratIon Tar Sand ' Tar Sand Non-ionic silic~ne in water (11.51 wt. % (13.68 wt~ %
- emulsion ` - ''`` ppm - ''- bit'umen) ' bitumen) Distilled water 49.86 Dow Corning 3471000 29.78 72.52 (60% Silicone fluid) 5000 82.36 91.46 10000 97.90 86.97 :.
Dow Corning 37 (35% Silicone fluid) 5000 96.14 92.69 Dow Corning HV-490 150Q0 98.24 --Dow Corning 365Q00 94.32 91.83 ~8~L5S9 .
TABLE II -'Effect on *he Hot Water'E~tracti'on Process .
Tar Sand Analysis Bitumen ll.l wt. % :
Water 4.9 Mineral Solids 83.9 Additive ppm on tar Bitumen Recovery sand basis (wt. %~
- Primary Fro*h . .
None 0 70.8 non-ionic short chain length polymer hydroxyl terminated --~Dow Corning 347) 20Q 68.1 essentially non-ionic, lO,000 cs 35% solids'made from DC-200 fluid.
(Dow Corning 37) 200 26.7 essentially non-ionic, `'~
35% solids, stable to freeze-thaw made from DC-200 fluid less than lO,000 cs.
(Dow Corning 36) 200 32.8 :, anionic, 35% solids, 100,000 cs, made from DC-200 fluid. -(Dow Corning HV - 490) 0.2 43.0 :
2 42.4 27.1 Dow Corning 347, chain length increased with catalyst 164** 200 11.08 * registered trade mar]~
** By using a suitable catalyst, such as Dow Corning* Catalyst 164 the polymer chain length of Dow Corning* 347 silicone emulsion was increased~ However by so doing, the number of hydroxyl groups decreased and the silicone emulsion gradu-ally became deleterious to the hot water extraction process.

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Claims (3)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. In a process wherein bituminous sands are deposited on and transported by an endless conveyor belt to its end where the sands are unloaded as the belt rounds the end roller, said process further including recovering bitumen from the bitumin-ous sands by means of a hot water extraction step, the improve-ment comprising:
treating the sand-bearing surface of the belt, prior to depositing the bituminous sands thereon, with a water-based emulsion having as the disperse phase a silicone fluid having short polymer chains such that the silicone fluid viscosity is on the order of 100 centistokes, said polymer chains being hydroxyl terminated, to provide a release agent which is operative to effect clean separation of the sands from the surface during the unloading operation and which does not substantially and deleteriously affect the primary bitumen recovery in the extraction step.

2. The improvement as set forth in claim 1 wherein:
the release agent contains at least 1000 parts of silicone emulsion per million parts of water.

3. The improvement as set forth in claim 1 wherein:
the release agent contains about 5000 parts of silicone emulsion per million parts of water.