Cross-flow filtration of fruit juice

1. Introduction

General aim

The general aim of this project is to develop and implement a system to filter process fluids from the Food, Pharmaceutical and Chemical industries in order to substitute the use of filters aids, i.e. kieselguhr,

Applied aim

The applied aim of this project is to develop a filtration system to clarify juice keeping and / or improving the quality of the juice.

Kieselguhr filtration

The mineral-based Kieselguhr filter is the most widely used filtration technique, because it meets required turbidity standards while maintaining good taste levels. However, this technique involves significant costs (DE filters cost between 60,000 and 100,000 Euro per year to small and medium-sized fruit juice manufacturers), unhealthy (the handling of DE powder during the replacement of the filter involves dust inhalation that can cause lung diseases), and polluting (because of the deposition of sludge or "filter cakes" after use). Some European governments are considering banning the use of Kieselguhr because of the dangers it represents to public health and to the environment. Moreover, the disposal of DE is becoming more and more costly as a result of the harmonization policy of the European Commission with regard to disposal costs. For instance, while disposal costs in Germany range between 30 and 120 Euro per ton of disposed materials, these costs will be set to a level of 600 Euro per ton in the coming years. European brewing and beverage industries are thus exploring alternative filtration techniques.

Membrane filtration

Membrane technology is currently a "proven technology" within a few main areas i.e., food and dairy industry, water purification and treatment of liquid effluent streams and this technology is presently being introduced into a wide variety of other applications. There is clearly a very positive trend for the development of industrial membranes, which will strongly influence the way industry evaluates separation processes in the immediate future.

This new technology will offer a competitive and attractive alternative to the filtration technique that currently dominates the market because of its efficiency and because it is harmful to public health and environment. Usually process solutions using integrated hybrid membrane systems will often be the best solution to a specific industrial separation problem.

The lifetime of the membrane material is crucial for the integration of membrane modules in industrial process streams which will usually transport fairly large amounts of gas and liquids at pressures and temperatures where the durability of the membrane materials over time are not yet fully exploited. If the membranes have to be replaced too often or if the membrane is easily damaged, the solution may be too expensive.

Membrane technology can work as well or better than the existing technology regarding product quality, energy consumption and environmental issues. The costs of this technology are not currently at a level, which will make the implementation attractive for all applications, but this is on its way. Membrane technology demands that basic research within material science is coupled to the understanding of problems related to the specific industrial process where the membrane module is to be integrated. Too often research at laboratory scale shows promising results, but a stronger involvement of industry is necessary in order to develop the membrane to commercial level and to promote the incorporation of membrane modules in a process together with other unit operations. The argument for doing so is the obvious advantages of this technology: cleaner and simpler process solutions, less chemical additives and lower energy consumption. The demand on industry for better environmental solutions and cleaner technology is also pushing the development and implementation of membrane technology.