Three Approaches to Mixing Polymers

Mixing Polymers

The properties of many process chemicals are controlled by the way they are mixed. The morphology of Mixing Polymers with EvenMix can impact its mechanical properties, surface energy and thermal properties. It can also affect its gas barrier and ease of processing. Mixing is a critical process step and must be performed in a manner that ensures that the final product meets specifications, without the formation of stringers or fisheyes.

Mixing polymers presents challenges that are not encountered with the mixing of smaller molecules because of the very high molecular weights of the materials under consideration. In addition, the entropy of mixing which so conveniently tends to drive the spontaneous mixing of small molecules becomes much less of a contributor to the mixability of polymers, thereby creating thermodynamically stable mixtures only over very narrow ranges of temperature and concentration.

In addition to the difficulties associated with the very high viscosity of polymer solutions, even at elevated temperatures, it is often difficult to disperse the solution uniformly into a solids flow stream such as that found in thickening and dewatering equipment units. This is because of the time it takes for the polymer solution to penetrate the dense sludge.

Adding a mechanical mixer to the system is one way of speeding up this process. However, there are a number of other issues that must be addressed as well. For example, if the mixing system is not properly sized for the application it can generate excessive shear that can break the sludge into finer particles and result in a loss of performance.

Another method is to use a non-mechanical system that uses the pressure in the vessel to achieve high levels of mixing. This type of mixing system requires a dilution water booster pump to maintain consistent incoming water pressure. This type of system can be simpler to operate than a mechanical system, but it can also be more complicated in design and maintenance.

A third approach is to utilize a combination of these two systems. The dilution water pump provides the initial high level of mixing and then the mechanical mixer can be used to provide the final high levels of mixing. This allows the system to achieve a more uniform sludge and reduces both the time it takes for the sludge to penetrate the polymer solution and the amount of dilution water required in the process.

In addition, compatibalizers can be added to the sludge to improve its adhesion to the polymer. This can further reduce the permeability of the sludge, allowing more of the sludge to be removed from the liquid stream during dewatering. This is a very common practice in wastewater treatment plants where the removal of solids from the water stream is an essential part of the overall process.