When is a Condensate Polisher Needed?

In the realm of industrial water treatment, maintaining the purity of condensate is paramount for the efficient operation of steam-boiler systems. Condensate is the hot, high-purity water produced as a byproduct of condensing steam in various industrial processes. It is very valuable but can contain impurities that, if left untreated, can lead to detrimental effects on equipment and operations.

Hardness in the condensate can lead to insulating scale on boiler heat exchange surfaces resulting in increased fuel consumption and potential tube failures. Iron can also lead to deposits within a boiler that impede heat transfer and flow with the potential for tube failures.

What is the best approach to managing problem-causing impurities in a condensate system? There are a few answers to this question, depending upon many factors.

  • Dump the Contaminated Condensate: To quickly mitigate the negative impact of the condensate contamination on boiler operation, the first answer may be to dump the contaminated condensate down the drain. There are a few things to consider when doing this, though. Can the softeners or other pretreatment equipment handle the increased load from having less condensate returned to the boiler? What is the financial impact of replacing the condensate being sent to the drain with cold makeup that must be softened and heated? Can the drain handle the temperature and volume of water?
  • Fix the Source of the Contaminant: Leaking heat exchangers, corrosion byproducts, and boiler water carryover can all lead to unwanted impurities in condensate. Hardness in condensate is usually from one or more leaking heat exchangers. High iron levels can typically be addressed by improved corrosion protection. Eliminating boiler carryover may bring the elevated dissolved solids back down.
  • Remove the Contaminant: If the source of the problem cannot be fixed, then the next option is to remove the contaminant with a condensate polisher. Typically, ion exchange resin is used, such as softening resin to remove hardness and iron. In larger or more problem-prone systems, a condensate polisher may be added as a safeguard against times when condensate contamination is occurring until the issue can be corrected.
  • Treat for the Contaminant: When the condensate contaminants CANNOT be prevented from entering the steam boiler, the next line of defense is to chemically treat for the condensate contaminant inside the steam boiler itself. Deposit, scale, and corrosion inhibitors are commonly included in boiler water treatment programs to handle any undesirable contaminants that make it past the pretreatment equipment or get returned with the condensate. Pretreatment failures and fluctuating condensate return can make controlling these internal treatment inhibitors difficult and possibly push them to the point of failure.
  • Accept the Impacts of the Contaminant: Last and least is the option of doing nothing. The impact may require acid cleaning the boiler, replacing failed boiler tubes, turbine blade imbalance, etc. There could be serious safety impacts as well, due to boiler overheating and catastrophic failure, for example.

Condensate Polishers
As mentioned above, there are times when the source of the contamination cannot be eliminated. Larger, more complex steam systems may also increase the likelihood of condensate contamination. An example of this is a large university that uses steam to produce hot water across the campus with numerous heat exchangers. With older systems, there may be an increased probability of at least one of these hot-water heat exchangers leaking hard water to the condensate system due to thermal stresses, corrosion, etc. Installing a condensate polisher adds an extra level of protection to help keep the steam boiler free of scale and deposits that can reduce boiler efficiencies and potentially cause tube and equipment failures.

  • Common Impurities: Hardness and iron are two very common condensate contaminants. In low- and medium-pressure steam boiler systems, ion exchange units similar to a softener may be installed to remove the impurities and “polish” the water to an acceptable quality for the boiler.
  • Materials of Construction: A condensate polisher must be designed to withstand the elevated temperatures of the returning condensate. The vessel and piping are commonly made of stainless steel with a specific ion exchange resin chosen based its ability to withstand iron fouling and compatibility with higher temperatures.
  • Regeneration: Condensate polishers have a limited capacity for removing impurities such as hardness (i.e., calcium and magnesium) and iron. Prior to leakage of any impurities through the resin bed, the unit will need to be regenerated. This involves backwashing the resin to remove any debris and fluff the resin bed followed by a brine draw to remove the hardness and iron from the resin beads. (Because iron can also be a foulant to the resin bed, iron-cleaning chemistry can be automatically or manually added to the brine tank.) Next, a slow rinse and fast rinse ensure the brine has been moved through and out of the resin bed properly. Once complete, the unit is ready to go back online to polish more condensate.
  • Location: For low-to-medium pressure steam boilers, it is typical to place the condensate polisher upstream of the deaerator (or feedwater tank) and downstream of any condensate pressurization pumps.
  • Other Requirements: It is important not to forget that condensate polishers will require a drain for the regeneration process and to drain the vessel for any maintenance. A city water source is commonly required as well to supply regeneration water for the slow rinse, fast rinse, and brine tank refill steps. Pressurized air may also be needed to operate valves.

When managing the impact of condensate contamination, it is important to consider all the options. Condensate polishers are one such option and play a vital role in maintaining the integrity and efficiency of steam boiler systems. By effectively removing contaminants from condensate water, these devices can help ensure the longevity of equipment and cost-effective operation.

At Chem-Aqua, we understand the importance of water treatment in industrial settings. Our comprehensive range of water treatment solutions, including condensate polishers, is designed to meet the unique needs of our customers, ensuring optimal performance and peace of mind. Contact us today to learn more about how we can help.


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