Bitumen and your chemistry are almost the same density, even at 145 F. How is it possible that you are achieving such great separation in a short period of time? Stokes Law would suggest otherwise.
Separation occurs because of the great shear that we exert on the oil sands particles that are dispersed equally. Instead of attritor it may be useful to think of high speed dispersers. The goal that we have is to attain an even dispersion so as to allow natural forces to operate. The Carbonaceous material is attracted to agglomerate together. Though they are separated in an aqueous solution the chemistry disallows the association of fines, sands and clays to reattach to the Bitumen. The Bitumen never forms froth. That is the bitumen does not go into an emulsion. The chemistry is the viscosity of water where the viscosity of the bitumen is much higher. The better the shear the less likely we are of taking on water (chemistry). Though counterintuitive, shear is our ally. We operate with top speeds in the area of 27 m/sec, which creates a lot of shear. The better the dispersion the faster everything will separate.
What is the mechanism of the chemistry (ie. What is the fundamental science going on)?
CAC-24 is a supersaturated aqueous based chemistry that has a Specific Gravity that is higher than bitumen and a viscosity that is similar to water. This combination keeps emulsions from forming under high shear. The saturation level of the chemistry is one of the keys utilized to keep emulsions from forming.
Why do the middlings not contain mineral fines? They can’t settle out in an aqueous solution, so where are they going and how?
In accordance with answers 1 & 2 with no emulsions present and complete dispersion taking place they will settle in an aqueous solution, as there is no other place for them to go. The Specific Gravity of the minerals is high enough so they settle readily.
What is the residence time of your PSV?
The Bitumen pops to the top within seconds of being released into the PSV. The settling time of solids and fines depends on the thickener design or use of centrifuge.
Why are there no diluents used in the process?
Diluents or solvents are used in the Clark system to break the emulsion that occurs. As the VPC Process creates no emulsions, there is no need for solvents.
How is CAC-24 supplied?
CAC-24 is made under license at the operator’s facility with readily available raw materials.
Can CAC-24 be reused?
CAC-24 can be reused. Its titration and pH are all that needs to be monitored and maintained.
Have you tried to wash the chemistry out of the solids to support your claims of 2% loss?
Yes we have. The chemistry will wash readily out of the solids.
Is the 70/50 to 50/50 chemistry to oil sands ratio based on weight or volume?
The water loss you calculated will be reduced in a commercial plant. Do you have any estimates of what it really will be, since this will be the area of biggest energy input?
Currently we have an open system that makes no effort to minimize and control this part of the process. We are not utilizing condensers, heat exchangers, etc. We agree that this will be the single largest energy consumer. Standard good engineering practice will minimize but as to what degree we are not prepared to say right now.
Have you tried doing the tests with less shear? I expect you can get by with a lot less shear than you are currently introducing.
As stated in previous answers the higher the shear the better the results. If the shear/dispersion is not high enough the settling time of the fines is greatly increased.