Water Conservation: An Innovative Approach towards Minimization of Blow-Down for Recirculating Cooling Water System

Water is the preferred cooling media in numerous industrial applications. Recirculating cooling water system with cooling tower is a common setup in thermal power plants, iron & steel plant, petroleum refinery and other industries. Cooling Tower working in the principle of evaporative cooling allows a small fraction of circulating water to pass into the vapour phase dissipating the thermal load from water as latent heat. As water molecule evaporates, concentration of dissolved species in circulating water build-up with consequence of deposition of scales like CaCO 3 , CaSO 4 inside heat-exchanging equipment. Scaling is the biggest danger for heat transfer process. The preventive mechanism is to discharge a portion of cooling water termed as “blow-down” along with dosing of scale inhibiting chemical in the circulating water. The blow-down constitutes a major portion of the total makeup water demand of the cooling water circuit. The current article demonstrates an innovative scheme of ion-exchange based side-stream softening treatment (3ST) for a small fraction (~ 1%) of circulating water is capable of reducing blow-down quantity significantly with simultaneous reduction of scale-formation possibility. While reduction in blow-down helps conservation of water, additional benefits are lower scale problems and better equipment (Heat exchangers, pipes) health, and a possible reduction in dosing of scale inhibiting chemical. From theoretical viewpoint with 3ST technique, a close approach to “zero blow-down” is possible with negligible quantity of forced blow-down in the form of drift loss.