Cooling Tower ChemicalsWhat is a Cooling Tower?
The purpose of a having a cooling tower is to reuse water and to minimize the amount of water used to cooling your process. Without the use of a cooling tower, the system would essentially operate as a once through water system. This is important to understand in order to under stand why chemicals are used in cooling towers. Watch free cooling water training videos online today! or download free public information from the Army Core on Cooling Tower Lessons learned.
What does reuse water mean?
Reusing water (Watch the Videos on that link) means as the water cools the system it returns back to the cooling tower again and again. As the water keeps recirculating, some of the water evaporates off into the atmosphere. As the water evaporates, additional fresh water is added to the cooling tower. With the addition of fresh water comes additional calcium and magnesium. As the process continues, more pure h20 is evaporated off and calcium and magnesium (referred to as hardness) is added to the recirculating water with the makeup water. So if the initial makeup water to the tower is 20 ppm of calcium and if more fresh water is added, the higher the concentration of calcium and magnesium becomes in the recirculating water. The number of time you reuse your fresh water is referred to as "cycle of concentration". At some point, this recirculating water reaches a point where the solubility of calcium and magnesium are exceeded and these elements begin to precipitate out.
Calculation of Percent Blowdown for Cooling Tower Chemicals|
Cycles for Cooling Towers and Condenser Water Systems
Cooling Water TreatmentWhy are chemicals used as in cooling tower water treatment?
The addition of chemicals allows of the hardness concentration to stay in solution rather then scaling out. So without chemicals you may operate at 4 cycles, but with the use of chemicals you may know reach 8 cycles. Without them you may develop scale and corrosion.
So why does increasing my cycles matter?
The cycles of concentration are reversely proportional to the amount of blowdown released from the tower. So if you are at 4 cycles and you start blowing the cooling tower down to avoid scaling your blowdown rate is 25% (1/4). If use chemicals your blow down rate is 10% (1/10). Remember the purpose of a cooling tower is to reuse water. So if you are not using chemicals, you are maximizing the reason for the cooling tower in the first place.
Do I have to use chemicals?
No, you can treat your system like a once through system. Problem solved? No. Now you have a new problem. When you continuous flush water through your system, you introduce more and more fresh h20. If you have iron pumps and copper in the system, you will begin to see rust. So even if you choose to not use chemicals to maximize your water cycles, a new problem arises. Chemicals will not only allow you to maximize your water reuse, but they protect your system from corrosion if properly implemented.
What are two most important things for creating a good cooling tower chemical program?
Simply put. Always use a bleed and feed cooling tower controller with your chemical treatment program. And always perform chemical testing with a complete test kit. If you dont take this advice, good luck!
How do you measure Cycles of Concentration?
Conductivity is the electrical resistance measurement of the dissolved solids, suspended solids, and dissolved gases of the water and is expressed in mico ohms (uomhs). You monitor the fresh make up water and compare this to the concentration in the recirculating water. Knwo your system volume is always important as well.
For example, if the makeup water to the cooling tower is 100 uomhs and your tower recirculating is 800 uomhs, your cycles are calculated as follows: Cycles = Cooling Tower Recirculating Conductivity / Cooling Tower Make-up Water
For this Example: Cycles = 800 uomhs / 100 uomhs or 8 % blowdown for the tower is calculated the following way:
Percent Blowdown = ( 1 / Cycles) x100 For this Example: % Blowdown = (1/8) x100 = 12.5%
This means 12.5% of the water is being lost to blowdown.
Knowing your tower cycles is important for minimizing water usage and reducing the amount of water lost to blowdown. Determining proper cylces or conductivity set point is dependent on the water alkalinity and calcium. Every system is unique.
This covers the need for why you need cooling tower chemicals for corrosion and scaling reasons. Now you have a second problem. Bacteria.
My cooling tower water has plants growing from it. What should I do?
This gets into the second chemical for Cooling Tower Treatment. You need a biocide to control bacteria in the recirculating water. A cooling tower is nothing more then a big vacuum cleaner. It will flush any debris in the air into the water system. This debris commonly is pollen and sources for bacteria development. Your makeup water is typically supplied with small traces of chlorine to prevent bacteria development, but once this fresh water hits the recirculating water the chlorine concentration is not high enough to kill off bacteria. As a result, you may see plants growing in your tower, green or black slime, and worse case very black bacteria that has a bad odor. Be careful if your tower looks like this. Water is the source of 98% of all the world's diseases. Dont take this lightly, cooling tower are major concern for the development of Legionella. Legionella is a water borne pathagon and may enter your body through a light mist if you are near the cooling tower. You must use a biocide to kill off bacteria in your cooling tower.
What type of Biocide should I use for my Cooling Tower Treatment program?
There are two types non-oxidizers and oxidizers.
Can I implement my own water treatment program? Do I need a license?
In most states no. The only concern is you may need a pesticide license for the use of the biocide (At least this is what your current water treatment provider will scare you with if you try to do it yourself). You can check with your states Pesticide restriction to double check. We just went through this process with a plant Connecticut and we found out they could use implement a biocide without a pesticide license. Do not let your currect water treatment provider use this salesman scare tactic with you.
How concentrated is the product?
Every chemical is a blend of multiple components that serve different purposes in preventing scale or minimize corrosion, so this depends on the chemical. What you need to find out is what ppm (parts per million) do you need to feed the product at. The higher the dosage rate, the more diluted the product.
How do I cross reference Cooling Tower Chemicals?
Sometime a MSDS may have some information on what you are using, but in most cases they will only list haz mat products like sodium hydroxide. This is not rocket. There is basically 4 chemicals groups to choose from depending on corrosive your makeup water is or what your scaling tendencies are. If you have city water most likely a basic chemical will do. There are easy test that can be perform to determine your program.
Do you have any Cooling Water Training videos I can watch?
Yes, we do. Click here.
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