Cooling Water in Cooling Towers and other Open Cooling Systems
In this field you have to face all possible problems a combination of water and cooling yields:
- Deposits of minerals and lime scale
- Contamination by algae and bacteria
- Accumulation of mud and sand particles etc.
In a cooling tower only pure water is evaporated and the well known continuous enrichment of the salts dissolved in water takes place, whereby the solubility limit of the salts will be exceeded sooner or later; this results in deposits within the cooling system. Hence a part of the cooling water has to be removed (elutriated = desalinated) periodically, to preclude an overrun of the solubility limit of dissolved salts. But the more water is elutriated the bigger is the water consumption in the system and the bigger is the impact on the operating costs of the cooling system. By addition of special hardness stabilization agents the elutriation rate can be reduced and water can be saved; but thereby the “densification” C in the cooling circuit increases.
C = Concentration of salts in cooling circuit water / Concentration of salts in make-up water
Z = Make-up water quantity
C = Densification
As shown in the drawing above the water demand decreases by 50 % when densification is raised from C = 1.5 to C = 3.0.
As can be seen in the chart too, the correlation between Z and C is a hyperbolic function – which means, that further increasing of the densification leads to more but proportionate lower water savings.
What is more, since constantly air is brought to the system via cooling tower, cooling water has to be considered very abrasive. For this reason dosing of a corrosion inhibitor is highly recommended in order to enhance life time of the cooling system.
By introducing air (oxygen) into the cooling water circuit growth of algae, fungi and bacteria is promoted. These are able to form deposits which hinder heat transfer in the cooling unit and by that are reducing cooling capacity; moreover they promote above mentioned aeration corrosion. By the application of specialised biocides, which yet have to be harmonized with the hardness stabilizers applied, microbiological growth in a cooling tower can be prevented.
An example for the design of a successful automatic cooling water treatment unit can be seen below:
By means of a cooling water treatment at its best the following advantages can be realized:
- Enhancement of possible densification and hence significant water savings
- Prevention of scale and dirt deposits and hence best possible heat transfer and maximum cooling capacity
- Prohibition of microbiological deposits
- Corrosion protection and hence extension of facility life time
We offer the following product lines for cooling towers: