When oxygen is present in the boiler the following process will happen: (2Fe3O4 + ½ O2 -> 3Fe2O3), which means that the protective magnetite film is corroded and a pitting-type corrosion in the boiler will take place. This type of corrosion can easily penetrate thick steel. The speed of corrosion will increase if the pressure and temperature are increased.
If you absorb the oxygen by using an oxygen absorbing chemical, such as sulphite, DEHA, ascorbic acid or tannins, the chemical reaction is blocked (as an example using sulphite the chemical reaction will be SO32- +1/2O2 -> SO42-). This way you avoid oxygen corrosion. (pitting)
Furthermore the formation of magnetite is stimulated (Fe + 2H2O -> Fe(OH)2+H2 and the temperature >120oC 3Fe(OH)2 -> Fe3O4 + 2H2O + H2)
Carbon dioxide leads to the formation of carbonic acid in the condensate system, which results in corrosion of the system´s parts (CO2(g) + H2O -> HCO3- + H+) = a pH value of 5-6 in the condensate.
Carbon dioxide can easily be neutralised by using volatile amines, as well as amines that are approved of according to the national “The Danish Veterinary and Food Administration’s permitted list”, internationally by the FDA.
Oxygen
Next > In untreated water you will find different amounts of mineral salts as well as other problematic substances, such as magnesium, iron, calcium, sulphates and silicates. If they exceed their own solubility due to a higher temperature in the water and a higher concentration, precipitation will happen.
These problematic substances can precipitate and will typically settle as deposits directly on the heating surfaces. The deposits form an isolating layer on fire tubes and boilers increasing the risk of deformation of the fire tubes as well as an increasing risk of under deposit corrosion. At the same time the deposits have a negative influence on the heat transmission which leads to an increased fuel consumption.
To avoid precipitations you often add different kinds of phosphates, that normally being trisodium phosphate (Na3PO4) or polyphosphates. These can be used as single components or in combination with each other. In up-to-date treatments it is common also using phosphonates and dispersing agents (e.g. ATMP – poly acrylic acids/acrylates) as well as other consumables (NaOH and copolymers/terpolymers etc.).
Each component has its own advantage and disadvantage, and therefore it is essential to choose the correct formulation, components and complete product for the protection and the blow down amount, but also in terms of the current economy of performance. The difference between an out-of-date and a modern water treatment concept can be significant – you could save up to 50-75% on the blow down.
Scale formation
Next > If the sludge is not properly spread, it will result in an accumulation of sludge, which reduces the circulation and affect the thermal efficiency.
Kemi-tech only offers environmentally friendly boiler protection programs. These programs include the use of high-tech polymers, efficient oxygen scavengers, and sludge dispersing agents. Using these will make the sludge discharge from the boiler when performing the regular blow down intervals
The products also have a foam-suppressing effect, so the highest possible concentrations are possible without the risk of priming. (carry-over)
Sludge formation etc
Next > 
