DuPont mixers get into gear

One of the biggest challenges in designing many processes is how to mix various substances. It's particularly tricky when the substances have different viscosities.

Process technicians at DuPont have adapted one of the most common mixing technologies, gear pumps, to make a version which they believe could provide an answer.

Gear pumps are supposed to pump and mix in the same process, but in practice it tends not to work well: systems that pump well don't mix, and vice-versa. Moreover, the process tends to generate heat.

The DuPont mixer differs from most gear pumps in that the mixing rotors are driven by gears outside, rather than inside, the housing. The intermeshed, counter-rotating rotors never touch, so they create a free-flowing 'nip zone' between the roots and faces of the rotor blades. In this zone, there is non-rotating shear flow which 'stretches' the materials inside the pump and encourages them to mix, no matter how different their viscosities.

The process requires very little extra heat, so is suitable for mixtures which are heat sensitive, or even for reacting mixtures, says DuPont.