Owing to various difficulties the use of ion exchange methods for complete demineralisation of sugar juices fails in many cases. An attempt was made to show by experiments, how far electrodialysis is able to provide the sugar industry with the advantages of such a process. At first it was found out that, by demineralisation of thick juice which was diluted to a concentration of 30° Bx, the colloids which remained in the juice were adsorbed by the ion exchange membranes and increased their electrical resistance to such an extend, that the use of this process became impossible because of the high consumption of energy. An economic use of electrodialysis became profitable only by adsorption of the higher molecular compounds, by means of decolorizing resins. Further, the low pH of the demineralized juice has to be adjusted. The authors realized this by percolation of part of the juice over a strong basic anion exchange resin. The advantages of demineralisation by means of ion exchange resins compared with electrodialysis are discussed on the basis of the presented analytical data.
A successful method was found to regenerate blocked membranes and a simple method to test the state of the membranes is described.
The optimal grade of demineralisation and current density and also the maximal, possible conductivity of the concentrate were determined and possibilities for using this procedure on industrial scale are discussed. It was tried, to calculate the dimensions of a unit to demineralize the juice of 1 000 tons of beet per day on the basis of the experiments done.
Contrary to the results of other authors it was found that removal of a-amino- nitrogen and betaine is very low. The sugar losses are acceptable so that the demineralisation of sugar juices by means of electrodialysis gives a profitable utilisation of the excess of electric energy of a sugar factory and the question of waste water is no problem.
Proceedings: CITS 1971
pdf download: CITS1971-411-433.pdf