Know your enemy
Published: 06 November, 2015
A 200 tonne cooling tower can accumulate in excess of 275 Kg of suspended matter over the course of just one year. Allowing a cooling system to get weighed down by bacterial growth and slime build-up leaves it vulnerable to corrosion and fouling and is not worth the risk to plant operation. But do you know the enemy well enough to effectively keep microbial growth at bay?
Stagnant water in cooling tower systems and closed cooling water systems is an ideal breeding ground for microbial growth, which can lead to costly problems within your cooling system - like accumulation of slime, circulation issues and even corrosion. These issues can result in a cooling system that is, at best, inefficient, and at worst, completely shutdown. The downtime and potential loss of revenue makes treating the water in your cooling system vital, and there are many ways to do this. However, chemical treatment, when done properly, can be a bespoke solution for your specific system. Chemical treatment programs Using chemicals is an ideal way to manage a few key problems:- Scale Build Up - A major scale forming contaminant found commonly in cooling water is calcium carbonate.
Corrosion - Another problem is corrosion control, as circulation water often contains corrosion inducing chemical contaminants, which can be due to high oxygen content, carbon dioxide, low pH, or the contact of dissimilar metals within the system.
Microbiology - Control of biological growth also causes problems, as algae or green moss and slime, made up of gelatinous organic material, can result in loss of functionality.
Foaming – while not a common problem, foaming is caused by contamination of the circulation water and can cause operational problems such as overflowing. Foam depressant chemicals are used to settle the process water.
Unfortunately, there isn’t a ‘one size fits all’ solution to chemical treatment. With so much to take into consideration it’s important to get the best biocide treatment for your system’s specific needs. A custom designed water treatment solution from Chem-Aqua can significantly reduce energy, water, and maintenance costs while ensuring safe and reliable operation, according to Brian Booth, vice president of Chem-Aqua, the Water Treatment Innovation Platform of global water, energy and maintenance solutions provider NCH Europe.
Chem-Aqua’s survey engineers test samples from every cooling system the company treats to determine the exact nature and optimum measure of biocides for each system. Precisely establishing the threats, by determining pH levels, half life, and organic loading on the system, means Chem-Aqua can tailor the treatment to target specific problems. For instance, in the steel industry water is used to cool molten steel, and it is common for slag and oil to contaminate the water coolant. In this situation, typical oxidising biocides, such as sodium hypochlorite (chlorine), may be ineffective and chlorine dioxide could be more suitable. Testing done during the survey process would highlight this before treatment began. Available in liquids, solid pastes, tablets, powders and granules, Chem-Aqua oxidative solutions are delivered in appropriate measures to ensure complete dispersion throughout a system and levels are continually monitored. Bespoke treatment can increase the life of a water cooling system, not to mention the whole plant, and reduce operating costs. If you’re in any doubt that you need to treat your cooling system in such a targeted manner it’s worth remembering that a mere 0.005 inches of microbiological fouling in a 1000 tonne cooler can increase annual electricity costs by £30,000. The cost of the 275 Kg of suspended matter you might collect over a year doesn't bear thinking about.
SPIRAX SARCO has launched a pressurised deaerator system that is said to reduce the dissolved oxygen content of boiler feedwater to virtually nil without chemical treatment.
