Blowdown Recovery - Introduction
Cooling Towers, by their very function, evaporate pure water, leaving any suspended or dissolved solids, such as minerals etc, behind in the retained water. If left unchecked this build up of solids, known as “the concentration factor” would leave the water unusable and potentially damage the system it serves.
For this reason the need to “blowdown” or bleed to waste a proportion of the system water to reduce this build up is absolute.
In the majority of the UK the total dissolved solids (TDS) of the mains supply water requires that the concentration factor within an evaporative cooling system is maintained at 3 to 3.5, requiring an amount of water equivalent to 50% of the evaporation losses is bled to waste.
Although this amount of water is relatively small, some 600 to 700 litres per hour for every mW (1000kW) of heat rejected, on large 16 to 24 hour run day systems the annual water bill can be quite significant. It has to be remembered that, unlike evaporated water, sewage charges are incurred on this water and if chemical water treatment is utilised these (and the money they cost) are thrown down the drain at the same time, impacting on the environment as well as incurring costs.
Overview
System UVEX with its (patent pending) system of filtration, de-chlorination, and reverse osmosis can effectively render 60 to 70% of this water clean and safe enough to be re-used in the cooling system. The remaining 30 to 40% can even be utilised for flushing WC's, urinals and other non critical uses such as washing machines.
The “pay back” on capital and running costs can be as little as 15 months.
The packaged equipment takes up very little space, usually less than two square meters, and can be incorporated into the System Uvex water management package.
With water becoming an increasingly precious resource, costing about £2.00 to £2.50 per 1000 litres, and set to rise, recovering as much as possible can make evaporative cooling even more attractive and the natural heat rejection method of choice.