Trip report from June 10, and July 21-22, 2003
After making a proposal to a client on how to improve their
current polymer process, the client wanted confidence that the proposal had a
good chance of working, prior to making expensive retrofit purchases. Post
Mixing proposed doing experiments at a mixing lab. The client chose to
do these at LIGHTNIN in Rochester,
NY.
On June 10, we used a model substance to simulate the actual
process in LIGHTNIN's PTL (Process Technology Lab). The experimentation
went better than planned. Lab Technician Gary Hodenius did a marvelous job
of catering to all our needs. The results were significantly better than
current practice, but also used a completely different style of agitation.
Upon reviewing the results, our client wanted even more
confidence in our proposal. The best way to achieve this is to perform the
actual process. Because of the solvents involved, the testing needed to be
preformed in an explosion proof environment. LIGHTNIN does these
types of process tests in their XP lab.
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To be on the safe side, the client decided to run the test for
24 hours (over mixing is not a problem). They rented LIGHTNIN's lab for 2
days, from July 21-22. With this we got the use of the Lab and a
technician. We got a lot done in 2 days!
Prior to the XP experiment, we did flow visualization studies
with a model fluid. We had to do this again, because the tank in the XP
lab had a different tank diameter than those tests we did on June 10. The
model fluid allowed us to operate at about a Reynold's Number Re = 6
(non-Newtonian flow characteristics were measured). It was good that we
did this, because we found that the optimum condition was different than in the
smaller tank trials done earlier. Our designated technician, Richard Howk,
went out of his way to help us out. We tried 4 different diameter
combinations, 2 different spacing combinations, and different number of
impellers all within 3 hours. We also had assistance from the Lab
Administrator, Craig Bahr, who helped us with data acquisition and computer
set-up.
Using the optimum configuration we repeated the tests in the XP
lab with the real chemicals. We were able to measure impeller speed,
torque, and power remotely or directly while we were in the lab. The
extent of the equipment was impressive. The stainless steel tank was
jacketed and we heated the reactor to the reaction temperature. It was
possible to reproduce every detail of our client's dope.
We were finished adding all the ingredients and taking the first
two hours of measurements by 7:30 PM. Richard stuck with us the entire
time. While we were watching the initial reaction, Richard started
preparing another reactor that was almost the size of the client's full-scale
unit. Amazingly enough, LIGHTNIN has such a vast array of impellers handy,
they were even able to dig up some very large impellers to maintain the D/T in
this fairly large tank. While we went to dinner, Richard stayed back and
installed a bottom steady bearing just so we would not loose any time with
testing the next day. He also left instructions for Chris on 3rd shift to
take speed and torque readings of our reaction through the night.
When we got back to LIGHTNIN the next morning, the mixing was uninterrupted
the whole night and the batch looked perfect. While we waited for the 24
hour reaction time to lapse, we did flow visualization studies using the much
larger tank with its new steady bearing in what LIGHTNIN designates as its High
Bay Lab. This is the area of some very large mixing equipment and
tanks. The good news is that by doing a 1:1 test with model fluids, we no
longer needed to be unsure about the scale-up procedure. We were testing
actual conditions and we were measuring torque through a very large LeBow torque
cell. We were also able to duplicate the clients current mixing system for
a visual comparison.
After our preliminary quality control measurements, we were
quite sure that the reaction proceeded successfully. The material was
drummed and prepared for shipment to the client's facility for in-depth
testing. Lab Technician Jeff Flint was very resourceful and located items
for the safe transportation of the final product.
During all of this testing, closed-circuit cameras were video taping
our experiments for later review.
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Conclusions
There is nothing like being able to test mixing proposals in a
lab and seeing the effects of impeller design, diameter, number of impellers and
positioning in a tank on mixing. Most very large companies have their own infrastructure
to do mixing experiments in there own labs (but they might not have the personnel
experienced in mixing to perform and understand the impact of what they are
doing). For companies that stick to their core competencies (making
products!), they can rent a lab and perform their own experiments and
have the same benefit. Hopefully, they will also hire the services of Post
Mixing to assist in the experimental design and analysis of the data to
minimize the time needed to be in the lab and come to a quick optimization.
The technicians at LIGHTNIN did a marvelous job. They really are craftsman and understand what they are doing. You don't
have to be afraid that you will get stuck with someone that does not. The
collective experience of the lab technicians is greater than 100 years. LIGHTNIN has many impeller designs and sizes for studying. They have 3
main labs for testing with a wide torque and horsepower range. The XP lab
is great for studying hazardous reactions and the cameras make it easy to watch
what is going on from a safe difference. They also have a lot of
analytical tools to your disposal.
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