An Investigation into the Design and use of Reverse Osmosis as a Pre-Concentration Technology in the Sugar Industry

Evaporation is one of the most energy intensive unit operations in sugar factories. It has two main drawbacks. Firstly, it consumes a huge amount of energy due to high latent heat of water (2270 kJ/kg) and secondly, heating may decompose the sugar molecules resulting in low quality and dark coloured sugar . The potential of developing reverse osmosis (RO) process as a concentration technique to remove water from fruit juices has been of interest to the fruit juice industry for about 30 years. Reverse osmosis has shown good results as a pre-concentrator in agro-food productions. The advantages of RO process over traditional evaporation are in lower thermal damage to product, increase in aroma retention, less energy consumption and lower equipment costs. One main disadvantage of RO is its inability to reach the concentration of standard products produced by evaporation because of high osmotic pressure limitation . Reverse osmosis can be used as a pre-concentrator prior to conventional evaporation. In the present work RO/Nanofiltration has been investigated for use in sugar industry before the multiple-effect evaporators as a pre-concentrator to reduce the load on the multiple-effect evaporator or to increase the capacity of the evaporation step and produce high quality sugar. Initial testing with different membranes (reverse osmosis and nanofiltration) of different manufacturers has been done.

Simplified Flowsheet of Conventional Sugar Manufacturing Processes

Proposed Simplified Flowsheet of Sugar Manufacturing Processes