Conference Dates

March 8-13, 2009

Abstract

Major advantages of the vapourpermeation in a distillation hybrid-process in comparison to molecular sieve adsorption are lower operating costs and steady state behaviour. Polymeric membranes are also cheap in production costs compared to inorganic membrane types. Disadvantages of state of the art organic membrane dewatering technology are sensitivity, unreliability and insufficient purified product quality.

GKSS has developed a new organic/inorganic membrane (based on polyvinylalcohol), which is longterm stable to common organic solvents (methanol, ethanol, isopropanol, etc.), temperatures up to 130°C and 15wt-% water in the feed. Higher temperatures and feed water-contents are being investigated currently in longterm tests.

Above 5wt-% water in the feed the permeat flux is significantly higher than the permeate flux of inorganic NaA and silica membranes. At 15wt-% water in the feed the permeate flux of 25kg/m²h is approx. twice as high as with a industrially produced NaA membrane [1]. These results are obtained at 120°C, 4bar retentate pressure and 0.02bar permeate pressure. Although below 5wt-% feed water-content the water fraction in the permeat (90wt-% at 1wt-% water in feed) is lower as for the NaA membrane (97wt-% at 1wt-% water in feed), low price and high packing density of the GKSS membrane are probably compensating this drawback.

The new GKSS membrane can be easily produced in industrial scale. During the membrane production it is straightforward to manipulate the flux and selectivity for different solvents and separation problems.

GKSS has developed envelope type membrane modules in recent years (0.49 to 1.25m long and 0.31m in diameter) with a high packing density, low pressure drop and easy to maintain. Customised GKSS envelope type modules can be assembled with up to 184 membrane envelopes of the new GKSS membrane (total active membrane area approx. 22m²).

Upscaling the production capacity can be done by upnumbering this modular technology.

For example, a distillation column top flux of 500kg/h with 85wt-% ethanol, 120°C and 4bar needs a membrane area of 17m² to reach a product quality of 99.6wt-% ethanol with a product flux of 420kg/h. In this simulation pressure drops in permeate and retentate side as well as polarisation effects are considered.

The whole pilot stage production process of membrane and module will be comercialised by GKSS partners.

[1] H. Richter, I. Voigt und J.-T. Kühnert, Dewatering of ethanol by pervaporation and vapour permeation with industrial scale NaA-membranes, Desalination 199 (2006) 92-93

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