Water Treatment Boilers Requirements

External and Internal Treatment
Water treatment is required to provide the physical plant with properly treated water in sufficient quantities to meet plant needs. All system require water treatment by using speciality chemicals such as corrosion and scale inhibitors , however open systems require constant water treatment to deal with the constant need for treated water to make-up for system losses of often up to 100%. Closed systems also require water treatment, but due to minimal system losses, that treatment commonly occurs only at the system fill source.

Industrial water treatment for cooling water systems , water treatment boiler requires advanced water technologies ,keeping in mind chemistry of water and use of advanced formulations of corrosion and scale inhibitors .

Three tools can be used to improve water quality:

• Internal Treatment – conditioning the boiler water to pre-determined levels by using a variety of chemicals.
• Demineralization/ Reverse Osmosis / Electrodialysis - the replacement of specific inorganic salts by ion exchange.
• Deaeration – the removal of dissolved oxygen and carbon dioxide by heating and atomizing the water with steam.
  

While demineralization and deaeration can be accomplished easily by investment in the appropriate support equipment, internal treatment calls for a more concerted effort. However, most organizations large enough to have in-house maintenance will find that the combination of these three tools will more than pay for themselves in defrayed operating costs. A well-implemented program will ensure -

• Increased heat transfer
• Lower fuel expenditures
• Lower chemical consumption

Except for steam trap maintenance, water treatment has the most potential for reducing annual operating costs in a power plant.

Objectives of Water Treatment boiler

Prevention of scaling in boiler.( use speciality chemicals such as scale inhibitors to counter it )

Prevention of corrosion in boiler. (use speciality chemicals such as corrosion inhibitors to counter it )

Prevention of stress corrosion cracking.

Prevention of steam contamination.

What is an External Treatment?

Treatment of water that are done outside of the boiler is called pre-boiler or external treatment. The main physical methods for improving quality of water for boiler include flocculation, clarification, deaeration, oil removal, colour removal, suspended solids removal and blow down. When preparing water for boilers operated at less than 150 psi, all necessary chemical treatments can be accomplished in a clarifier, but as pressure increases; the quality of feed water must improve. The purpose of external treatment is to reduce suspended solids, demineralize the feed water and remove silica. This purpose can be achieved by

• Coagulation with chemicals
• Demineralization/ Reverse osmosis/ Electrodialysis (cold lime, soda process, hotlime-soda process, mixed bed exchange)
• Silica removal (coagulation with chemical, Demineralization, Reverse Osmosis, Electrodialysis)

What is an Internal Treatment?

There are number of treatments that are made within the boiler to minimize the adverse effects of small concentration of components that remain in the feed water after the external treatment. In spite of various external treatments, it is not possible to attain an absolute perfect quality of boiler feed water. Chemical treatment or internal treatment of water inside the boiler is essential to take care of various impurities entering into the boiler such as hardness, dissolved solids, oxygen, and silica.

In many cases, external treatment of water supply is not necessary specifically in low or moderate pressure boilers or where large amount of condensed streams are used or when raw water available is of very good quality.

taken from http://www.watertreatmentbooks.com