Chemical Reaction Simulation

The topic we will develop a little today is on chemical reaction simulations under mixing in stirred vessels, there is another article about chemical process simulation. The main reason for discussing this topic is that with VisiMix, we succeeded to have a product that is very innovative. Until now, there was no way to establish a connection regarding the performance of the reaction in mixing stirred vessels, even in scientific studies.

We succeeded in solving this simulation and calculation problem and discovered what the scientific reason is for the performance of the reaction in stirred vessel tanks. The main idea stems from the fact that when we feed materials into our tank, and a sequence of reactions occurs simultaneously, we will likely generate one product. So, with one of the reactions we will generate our product, but other reactions can happen and normally are happening. We would like to see those reactions occur at a very low level. To do this, we need to control the mixing—the interaction between the materials—that we prefer to generate in the main product and not in the side product.

So, the idea is that when we feed our materials into a tank and talk about Turbulence Regime and miscible materials, we see those materials start to move and interact with each other. But in the field of flow and turbulent flow, we have a minimum side of group of molecules that are moving together. When we are mixing in fluids, we are not able to organize molecules. There is no possibility in the mixing, in the flow phenomena. The minimum side that we are able to control is the Eddy Size—the professional name is Kolmogorov Eddy Size. This Kolmogorov Eddy Size refers to a group of molecules that are moving together. Such a kind of size is connected with the energy we apply to move the flow , and with the geometry of the equipment we are using. These very small Eddies determine the macro mixing and micro mixing characteristics, and there are two completely different zones in our tank. The macro mixing is the zone in the tank that is bigger than the micro mixing size. The micro mixing size can be a number of few micrometers, and inside we have our materials.

How this is connected to the reaction is in the following way. All the materials that are inside the Eddies—the Kolmogorov Eddy Size—are connecting, in fact, to the second size, according to molecular diffusivity types. All the materials that are outside the Kolmogorov Eddy Size are interacting according to the inertia and the velocity of the flow. There are two completely different ways to interact, at different time rates. So, based on this, what we are doing is the following: We are, according to the geometry, density, viscosity, and volume in the tank, calculating what the flow into the tank is. We know what the materials are that we have in our tank. We know what the local concentration of every entity is in the tank. And once we know what the Eddy Size is in every part of the tank, we are able to divide the reaction rate into zones—those that are in the macro mixing control (more than the Kolmogorov level), and those that are in the micro mixing size that is controlled by diffusivity.

This kind of calculation has not been done elsewhere. We have been able to perform eight components and five reversible reactions with catalysts or inhibitors. We have been able to calculate the comparison between perfect macro mixing equipment and the actual reactor performance. We can compare what the maximum perfect yet realistic micro mixing could be versus what our actual equipment yields: a composition of some macro mixing and some local mixing.

By the way, we all think about good mixing or better, well-mixed equipment. These, of course, are not part of our calculation because it is not physically possible. The assumption that we have with perfect, well-mixed equipment is that when we feed the material into the tank instantaneously, this material will have the same concentration at every place. That, of course, is impossible; it cannot happen in the realistic and physical or liquid environment that we are dealing with.

So, well-mixed is only an assumption that is completely hypothetical. Perfect macro mixing is the maximum capabilities of our tank to generate homogeneity in realistic conditions. And the realistic results will be obtained when we include the micro mixing phenomena, controlled by the minimum Eddy Size possible—that is, the Kolmogorov Eddy Size. This is the basis of our new product; this is an innovation in the scientific world and in the process of calculations in the industry. The process happens very quickly; we are able to calculate by clicking “Enter,” generating results in less than a minute for complex reactions—as many as five or six—at different places in the tank and with different filling positions. This can be done for batch, semi-batch, or continuous flow. This explains exactly why we have such a deep deviation between what we do with one piece of equipment, even in the lab, and with other equipment that can be used in the pilot or production stage.

VisiMix Video

The Influence of Mixing in the Process
New methodology using VisiMix software for the purpose of checking the influence of mixing in the processes.

VisiMix Demo Operation
Learning how to input data into the VisiMix software and get results the will help us understand the influence of mixing in our processes.

Lab Experiments
Learning how to set up the relevant experiments at the lab scale, to develop the processes from an engineering point of view.