Spent Brine Recovery from Ion Exchange Effluent: The Environmentally Friendly De-colourization Option

摘要

Sugar melt de-colourisation through ion exchange resin is becoming more popular because of its simplicity, regeneration in place, lower capital and operating cost. Traditionally, this technology was not environmentally friendly because of the generation of large quantities of spent brine which has a high chemical oxygen demand (COD). This is because it contains high inorganic and organic material, the former due to salt and the latter due to desorbed colourants. Recent advances in the spent brine treatment have reduced significantly, the volume of effluent discharged by subjecting the spent brine with the following unit operations: 1. Nano filtration (NF) 2. Brine concentration 3. Spray drying In terms of chemical saving, the NF process recovers 75% - 80% of the salt in the spent brine. The recovered brine and associated water are recycled to be reused in the regeneration of the de-colourization columns. This paper describes the design philosophy employed at a brand new 1000 tpd port based refinery and describes in detail the NF process, the brine retentate concentration process and the spray drying process. The only waste emanating from this process is a crude salt with about 5 % moisture. The process completely eliminates any water or air pollution which is characteristic of other de-colourization systems thereby confirming its place as the best environmentally friendly de-colourization process to date.