SEPARATION OF GLYCOL AND WATER FROM COOLANT LIQUIDS BY EVAPORATION, REVERSE-OSMOSIS AND PERVAPORATION

Coolant liquids having glycol contents in the range of 20-30% (p. wt.) have been identified as hazardous organic waste. According to the total vehicle coolant liquid consumption in the FRG of approximately 200 000 metric tons per year (t/year), less than 40% of these used liquids are submitted for disposal by methods which are in compliance with environmental legislation, such as incineration. Recently, some waste management companies have started pure distillative recovery processes resulting in a glycol quality allowing for reuse of the product. For dewatering of the used coolant to a water content of less than 5%, a membrane hybrid process has been developed offering some process and economic advantages compared to pure distillative processes. Laboratory- and bench-scale qualification tests have been performed for the different process components. The lay-out and cost estimations for a plant with a capacity of 12 000 t/year result in investment costs of 4.5-5 million DM. The operating costs for the recovery process are in the range of 430 DM/ t of coolant liquid.