Post Mixing Optimization and Solutions


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.

Craig Bahr, Tom Post, and Richard Howk

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.


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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