Boilers

A boiler is a vessel in which water is continually vaporised into steam by the application of heat. Primary objectives in boiler design, operation and effective treatment include: efficiency in heat transfer, minimisation of energy usage, production of pure steam and safe, reliable operation.

‘Feed water’ is the water added to a boiler to replace that lost due to evaporation and blow down losses. Often steam is condensed and returned to the boiler as part of the feed water. ‘Make up water’ is the additional water needed to supplement the returned condensate in the feed water.

The main aims of a successful boiler water treatment regime are to prevent feed water system scale and corrosion, prevent corrosion in the steam condensate system, prevent deposition and corrosion in the boiler, avoid oil and process contamination and to ensure proper lay-up of out-of-service boilers

Both external and internal treatment of the boiler water is used in order to ensure optimal operation. External treatment of the make up water reduces or removes impurities. There are many types of external treatment (water softening, dealkalisation, deaeration, ion exchange and reverse osmosis). The type of external treatment used will depend on the purity of the make up water required. This in turn will be determined by the volumes of feedwater required and the boiler design (pressure, heat transfer rate etc.) The water purity is of particular importance in high pressure boilers were virtually all impurities must be removed from the water.

Internal treatment, generally by the controlled addition of boiler water treatment chemicals, is the conditioning of impurities within the boiler system. The reactions occur either in the feed lines or in the boiler itself.

Below are the main components of an effective internal boiler treatment program:

• An oxygen scavenger which will eliminate oxygen from the feed water and thus prevent corrosion.
• A dispersant component is required which will react with any residual hardness present in the incoming feed water, and prevent precipitation of scale onto the boiler surface. This will also condition hardness sludge in the boiler and prevent its adherence.
• Supplementary alkalinity which ensures enough alkalinity is present to prevent boiler corrosion.
• On occasion an antifoam may be required in order to allow a reasonable concentration of dissolved and suspended solids in the boiler water without foaming.
• In addition, a complete treatment program should prevent corrosion and scaling of the Feedwater system and protect against corrosion in the steam-condensate lines.

The correct selection of chemicals and accurate proportioning and feeding of these chemicals is essential to ensure that the recommended amount of treatment is maintained continuously. Keeping the boiler water dissolved and suspended solids below set maximum limits is accomplished through blow down.

B & V Water Treatment has an extensive range of boiler water treatment chemicals for low, medium and high pressure boilers which includes: oxygen scavengers, dispersants, alkalinity builders, return line treatments and multifunctional products.

In order to ensure that the requirements for your specific boiler are met, and that optimal performance is achieved and maintained, please contact us. One of our experienced water treatment representatives will be able to advise you on all aspects of your boiler water treatment in order to find the most effective means of obtaining the required quality and boiler reliability.