Effective site water management is heavily dependent on the ability to optimize cooling tower operation. Cooling towers and the associated condenser loop of chillers represent major components of the total water footprint on site. The condenser system is a critical system for the fab, responsible for the entire site energy management. It represents a significant percentage of total site water usage and maintaining reliable operation can be a large expense. Failure to effectively maintain this system may lead to excessive cost or water consumption. In a worst-case scenario, failure to properly maintain this system could ultimately lead to a factory shutdown.

What factors affect the operation?

Make-up water qualityCritical quality parameters include concentrations of calcium, alkalinity, chloride, and silica. These parameters have direct effect on corrosion and scaling control, chemical treatment consumption, and amount of blowdown flow needed. Today’s industry trend increasingly uses reclaim water to enable control of these parameters in the make-up water and to therefore have better control of these parameters in the condenser loop.

Corrosion Management Three factors can influence the corrosion rate within a cooling tower and condenser loop:

• Biological Fouling
• Scaling
• Blowdown Rate

The first two are naturally occurring and can be controlled by using chemicals. The chemical cost will depend on the rate of biological fouling and scaling. Reducing TOC in the makeup water quality will reduce bio-growth and therefore the rate of biological fouling. Thus, lowering the cost of chemicals.

Controlling parameters such as calcium in the condenser loop is critical. These non-volatile contaminants will not be evaporated, and if left untreated will be concentrated within the cooling tower. The only way to reduce them is to send them to blowdown.

A second reason for blowdown is that there are some treatment chemicals that will not be stable for a long period of time and will start to decompose. In this case the chemical program must ensure that the treatment chemicals are active and have the maximum chemical retention.

Corrosion management method, including biological and fouling/scaling control Three major risks for any cooling tower system are corrosion, scaling and fouling/biofouling. The leading approach in the industry today is to use chemical treatment to be able to control these processes that occur naturally in the condenser loop system. The chemical cost will depend on two parameters:

1. Process rate of corrosion, scaling, fouling/biofouling
2. Blowdown Rate

Controlling the make-up water quality will help to reduce these risks. For example: if we reduce the incoming total organic carbon (TOC), we will reduce the bio-growth rate and thereby the biofouling process. This will reduce the required chemical treatment injection and associated chemical cost.
Environmental compliance considerations Today’s regulations become more and more strict with respect to compliance requirements. Cooling towers can be a major contributor of parameters such as organic carbon, phosphorus, and nitrogen while chemical treatment can also impact inorganic parameters (e.g., metals). Having better control on the chemical injection and system management to reduce blowdown and added chemicals can reduce not only the cost of the chemicals, but also the impact on environmental compliance.
Water Reuse Strategy Using reclaim water, you can lower your freshwater demand and reduce the cost of purchasing city water. While this action can lead to better condenser loop management, it can also lead to increased risks to your system at the same time. The risk is mainly driven by the fact that overall site water balance is shifted towards increasing concentration of the chemistry in the outfall, adding pressure for environmental compliance, often defined in the units of concentration. Collaboration with local authorities often helps to resolve the tension by redefining the compliance requirements in the alternative way, i.e., using load-based compliance.

What can I do to optimize cooling tower operation?

While the condenser loop system is a significant water consumer and critical system at any semiconductor facility, it is possible to bring the system to a stable operating condition that will minimize changes or decisions needed during day-to-day operation. To get to this point you will need to ask yourself the following questions:

1. Is my make-up water the best water that I can get to the cooling tower?
2. If not, do I have a plan how I will get the right make-up water?
3. Do I have chemical treatment that suits my system and takes into account the specific needs of the system and site?
4. Do I have clear change management process to ensure right decisions?
5. Do I have the right process and tools to monitor the system?
6. Do I have the right expertise and focus to monitor and take needed actions?
7. Do I want to increase my system reliability and reduce the risk and operation cost?

By answering the question above you can better understand what is missing and how you can optimize cooling tower operation. While condenser loops are well-known systems, there are pioneering and approved ideas and technology that can help you to increase reliability of your cooling tower system while reducing the risks and operation cost of your system.

If you are looking for additional information about best practices for cooling tower operation or pioneering approach of blowdown management, please contact FTD Solutions.