Water is removed through selectively permeable membranes.
A relatively simple and economical process and apparatus for concentrating hydrogen peroxide from aqueous solution at the point of use have been invented. The need for this or a similar invention arises for the following reasons:
- The highest commercial grade of hydrogen peroxide has a concentration of 70 volume percent.
- Concentrations of more than 80 volume percent are required in some industrial and some military propulsion applications.
- Prior methods of concentration of hydrogen peroxide are expensive and can entail production of quantities larger than can be utilized immediately. The necessity of storing and handling the excess concentrated hydrogen peroxide poses a safety problem.
The heart of the apparatus is a vessel (see figure) comprising an outer shell containing tubular membranes made of a polymer that is significantly more permeable by water than by hydrogen peroxide. The aqueous solution of hydrogen peroxide to be concentrated is fed through the interstitial spaces between the tubular membranes. An initially dry sweep gas is pumped through the interiors of the tubular membranes. Water diffuses through the membranes and is carried away as water vapor mixed into the sweep gas. Because of the removal of water, the hydrogen peroxide solution flowing from the vessel at the outlet end is more concentrated than that fed into the vessel at the inlet end.