Cooling towers are an essential part of industrial processes. In order to prevent scaling, corrosion and biofouling a mix of chemicals is added to the cooling water. In addition, regular blow down is used to prevent the conductivity of the system from exceeding recommended levels. This leads to large quantities of water and chemicals being flushed away as waste, with the associated costs.
Voltea, a spin-off from Unilever, has developed a water conditioning technology called Capacitive DeIonisation (CapDI) that is designed to remove dissolved salts from a variety of water sources ranging from tap water and process water to brackish ground water and also cooling towers.
The basics of the CapDI system are simple. Ions pass through an electrical field and are temporarily stored on porous electrodes. When the electrodes are saturated the electrical field is reversed and the ions are released in a small concentrated stream and the process can start again. During the regeneration, ion selective membranes prevent the ions from passing to the opposite electrode effectively trapping the ions in the waste stream. This allows for a thorough cleaning of the electrodes during the regeneration cycle and prevents fouling of the electrodes.
CapDI can be used in a variety of industrial processes. One of its key uses is in re-circulating cooling systems where it offers water and chemical savings and boosts the performance of the cooling system. Up to 40% water savings and 80% chemical savings are achievable.
The water and chemical savings are a direct result of the system's ability to remove salts from the make-up water. Consequently the cooling system can be operated at five times higher cycles of concentration (CoC). For example a cooling system initially operated at CoC of three, can be operated at CoC of 15 with CapDI.
