Mixing a gas into a liquid is usually a complicated process. An entraining rotor recently invented at the National Institute of Standards and Technology (www.nist.gov), however, mixes the two in seconds, a task that previously could take hours. It consists of a left-handed deep-pitch screw with a ceramic magnet mounted in its base. The screw is hollow with several holes in it.

The entire device is placed in a vessel containing liquid to be mixed with a gas. A magnet spinning under the vessel couples with the ceramic magnet in the base, causing the rotor to spin and a vortex to build in the liquid. As the rotor turns at up to 400 rpm, the screw's vanes generate turbulence and mix or entrain vapor into the liquid. Vanes also draw vapor down into the liquid from above the rotor. Some of the vapor entrained into the liquid is pulled through the holes in the shaft and travels out the top. The hollow shaft serves as a draft tube and sets up a circulation that lets gas continually mix with the liquid.

The magnet drive eliminates the need for seals and reduces the risk of leaks. It also lets the entraining rotor work in pressurized vessels.