Steven Blankenbeker on mon 18 oct 04
On Wednesday I am going to the NC Minerals Research Lab where they are
working on the pilot setup to process the kaolin material. We are trying
to arrive at the most economical way to get kaolinitic soup of about 60%
water down to a kaolinitic powder. I apologize for the delays, but it is
imperative that we come up with a simple way to get the material into a
useful condition. I am nearly 100% positive that the material will
function in a manner similar to Avery as a flashing slip material, as my
testers have and are showing, it is just difficult to get the water out of
the slurry. We are trying to avoid filter pressing as this will drive the
cost up and require a lot of equipment for a small amount of material.
I am learning more about the material for those interested. This kaolin is
a primary kaolin, as was the Avery, but the formation is entirely
different. The Avery formed from weathered Alaskite feldspar which was
derived from a volcanic intrusion or dike into a granitic host rock.
Weathering through ground water, CO2 and such metamorphosed the feldspar to
mica, silica and kaolin. The original Harris Mining group extracted all
three from the host rock, the kaolin being the last and finest, but only
making up 10 - 15% of the whole. The new kaolin is formed from felsic
(light, nonmaffic - meaning low irons and heavy metals) volcanic ash that
was deposited in layers in quiet prehistoric seas, then was covered with
Atlantic coastal sands. The sands protected the ash from erosion, but
allowed it to consolidate while still having proximity to weathering
groundwater. This ash, under weathering conditions, then formed kaolin. I
would assume that the ash not protected by the coastal sands became
partially kaolinized, then was transported and sorted to form the prominent
kaolin belts of NC, SC and GA, as these lie south and east geologically
from the new clay deposits. Keep in mind that the kaolin clay mineral will
almost always be the finest particle sized material in any weathered mass,
and therefore will stay suspended in water longer than most anything else.
High surface to mass ratio also further increases its tendency to float.
The process of kaolin extraction from host dirt is pretty much the same as
making terra sigilata, only on a larger scale. If you are familiar with
that process, then you will understand the obstacles we face.
I will continue to keep you guys informed, and hopefully will get you
samples short
Ivor and Olive Lewis on tue 19 oct 04
Dear Steven Blankenbeker,
If this weak slurry is refusing to settle then you need to introduce a
Flocculating Agent.
This may lead to a bit of a dilemma because those that are recommended
are sure to alter the composition to the extent that it will change
the characteristics of the material and you will loose the properties
that make it desirable.
Best regards,
Ivor Lewis.
Redhill,
S. Australia.
steve baker on tue 19 oct 04
Thanks for the help. I am actually more the dirt guy here and my friends at the research center are the process gurus. One of them actually ran the Avery operation for years, and he is impressed with the way the new stuff is reacting. Actually, the material deflocs, flocs and settles extremely well, and everything to this point that has been tested has been exposed to the same defloc/floc systems, so I don't foesee any problems with the chemistry of what we are doing. More of a mechanical problem at this point. It is really just a matter of getting the material dried or at least caked.
Ivor and Olive Lewis wrote:Dear Steven Blankenbeker,
If this weak slurry is refusing to settle then you need to introduce a
Flocculating Agent.
This may lead to a bit of a dilemma because those that are recommended
are sure to alter the composition to the extent that it will change
the characteristics of the material and you will loose the properties
that make it desirable.
Best regards,
Ivor Lewis.
Redhill,
S. Australia.
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john mertens on tue 19 oct 04
Steven
Have you looked at spray drying-can be set up at reasonable cost-or use 2nd
hand centrifuges.
Regards
Jan Mertens
Tottenham-Ontario-Canada
mailtoandrew@FSMAIL.NET on fri 22 oct 04
Hello Steve,
I found your post very interesting and would certainly be interested in
further information. Some immediate thoughts were:
Given the different parent rocks of the Avery and new material how are you
so sure the new will be so similar?
What testing and assessment work have you done?
Why would filter pressing add so much to the cost? If its the capital
investment are there any facilities in your local area that can be used
under contract? It probably worth noting that mechanical dewatering is
invariably cheaper than thermal methods such as spray drying.
Best of luck, and I looking forward to your future posts.
Regards,
Andrew
steve baker on mon 25 oct 04
When I began this project, I did not know the difference in origin. I did know that geologically they were both called "primary", and I knew that that was important. When I first saw this vast deposit, my first thought was to wonder why it had not been exploited, because I knew that great efforts were made over the years to work the deposits in the mountains. The key to answering that question is to understand fully the operations that produced primary kaolin in the past. These were not just kaolin operations. They were mica and high purity silica operations as well, especially the mica. The three together made a viable operation. The kaolin alone would not. And from what I have seen of the various sized components of this clay, there is very little mica, and the coarser fraction is still carrying 12% or so alumina, so it is not very pure. The first simple tests made on this material showed a clay that flashed a nice orange, so we simply took the project to the next steps.
The chemistry was somewhat different, although I felt that the new material may actually be better, as it had more iron and more alkali, and seemed to have a nice fluxing nature to it. As it stands now, I can easily get the material to roughly a minus 10 mesh clay in a solution of a specific gravity of about 1.35, or what I guess at about 33% solids, in a flocced state. I am now exploring ways to get this dewatered. Filterpressing will only get me down to about 20% or so, as have most vaccuum dewatering systems. So some sort of drying would still be necesary. I have ample access to waste heat here at the brick yard, and am considering just drying the slurry on trays and recovering the dried cake. That sounds primitive by modern standards, but is actually very economical. We have two parallel tunnel kilns with an area between them that is like a dry heat sauna. The amount of labor involved would be minimal.
Thanks for the input.
Steve
mailtoandrew@FSMAIL.NET wrote:
Hello Steve,
I found your post very interesting and would certainly be interested in
further information. Some immediate thoughts were:
Given the different parent rocks of the Avery and new material how are you
so sure the new will be so similar?
What testing and assessment work have you done?
Why would filter pressing add so much to the cost? If its the capital
investment are there any facilities in your local area that can be used
under contract? It probably worth noting that mechanical dewatering is
invariably cheaper than thermal methods such as spray drying.
Best of luck, and I looking forward to your future posts.
Regards,
Andrew
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