The concept of employing water, fresh or distilled, as a power generating source and heat exchange medium originated and was realised with the inception of the steam generator or boiler, and has been applied most successfully and beneficially in this manner ever since.

Water has the ability to transfer heat from one surface to another, thereby maintaining the system within the correct operational temperature range while generating steam to carry out work. However, water can adversely affect metal components under the operational conditions normally found in steam boilers and other heat exchange devices.

The extent of deterioration depends on the specific characteristics of the water and the system in which it is being used.

In order to counteract the detrimental properties normally attributed to water and its contaminants (dissolved and suspended solids and dissolved gases), special chemical treatment programmes have been devised.

Accepted water treatment processes and procedures are constantly being upgraded and modernized, and new methods are being developed to complement and/or replace older ones.

Although water from marine evaporators and boiler condensate return systems is essentially “pure”, minute quantities of potentially harmful salts and minerals can be carried by this composition and feed water into the boiler, where they will accrue, ultimately resulting in serious problems in the steam generating unit. In addition, the water can also contain dissolved gases, i.e. CO2 and Oxygen, which can result in corrosion of the system.

Using unprocessed fresh water (e.g. shore water) as a makeup source can present some of the same problems experienced with distilled water, but in addition, certain contaminants which are naturally present in fresh water can be extremely destructive in boiler systems if not dealt with promptly and effectively soluble salts such as Chloride, Sulphate and Carbonate are present.

as electrolytes in the untreated water, leading to galvanic and other types of corrosion, depending on the conditions in the system. In addition, Sulphates and Carbonates have the potential to form insoluble, adherent, insulating “hard water” scale deposits on heat exchanger surfaces.

Following Treatment Is Generally Done In Boiler

Phosphates-dispersants, polyphosphates-dispersants (softening chemicals): reacting with the alkalinity of boiler water, these products neutralize the hardness of water by forming tricalcium phosphate, and insoluble compound that can be disposed and blow down on a continuous basis or periodically through the bottom of the boiler.

Natural and synthetic dispersants (Anti-scaling agents): o Natural polymers: lignosulphonates, tannins o Synthetic polymers: polyacrilates, maleic acrylate copolymer, maleic styrene copolymer, polystyrene sulphonates etc.

Sequestering agents: such as inorganic phosphates, which act as inhibitors and implement a threshold effect.

Oxygen scavengers: sodium sulphite, tannis, hydrazine, hydroquinone/progallol-based derivatives, hydroxylamine derivatives, hydroxylamine derivatives, ascorbic acid derivatives, etc. These scavengers, catalyzed or not, reduce the oxides and dissolved oxygen. Most also passivate metal surfaces. The choice of product and the dose required will depend on whether a deaerating heater is used.

Anti-foaming or anti-priming agents: mixture of surface-active agents that modify the surface tension of a liquid, remove foam and prevent the carry over of fine water particles in the steam.