Chemical Rehabilitation – Mineral Scale and Boiler Scale
Problems and troubles caused by boiler or mineral scale
The deposits formed in water-bearing systems reduce the heat transfer rate, because scale layers are very poor heat-conductors – this in turn leads to a sharp increase in energy consumption and losses in power output.
The chart below illustrates the energy losses due to mineral (lime) scale:
In addition to the rise in energy costs, heavy scaling can also cause undue thermal loads since the coefficient of thermal expansion in the scale layers is substantially lower than that in the underlying metal. This can result in cracks (frequently seen sectional boilers and steam boilers) and further costly repairs.
But even without heavy thermal loads your water pipes may – an appropriate salt contents in your water presupposed – look like that in a while:
The (dis) solution of the problems
Acids armed with special corrosion inhibitors are used to remove calcium deposits. These anti-corrosive agents have been developed to protect metals against acidic attacks – an invisible (mono-molecular) protective film abates on the metal, not affecting the scale, so that the acid is free to remove the deposits.
The kind of descaling agent to be applied depends on metals existing in the system and composition of the scale. We offer perfectly balanced multifunctional products consisting of the appropriate acid and corresponding anti-corrosive agents, enabling our clients to start with descaling immediately
Implementation of chemical descaling
When calcium deposits are dis-solved with acids, carbonic acid (CO2) is released, causing generation of foam. For this reason, the descaling method applied has to allow gases to escape. And since a certain time for reaction with the scale layers is required, the solution has to be circulated within the system. The gases generated during descaling are allowed to escape by pumping the water into an open intermediate container.
After a chemical rehabilitation the cleared system should be re-treated to prevent additional, short-term corrosion – and this has to be done with our TRINEUTRAL.
A neutralization process has to be applied before disposal of used descaling solutions; for a more detailed information on this issue see our bulletin “Neutralization of waste water after chemical descaling”.
In detail the following products are available for chemical descaling:
most frequently employed dissolvent for boiler and mineral scale as well as rust, for vessels and pipes made of iron or steel.
descaling agent especially for heat exchangers (and other vessels) made of copper and iron.
descaling agent for galvanized (zinc coated) vessels, cooling towers, pipes etc..
chlorine free descaling agent with allround inhibitors, suitable for all metallic materials.
descaling agent especially designed for vessels and pipes made of non-ferrous metals like Aluminium and stainless steel.
Descaling and rust removal agent rolled into one, prevents subsequent corrosion; not suitable for zinc or zinc-coated surfaces and low-alloy stainless steel.
For removal of different, additionally to lime existing components of boiler or mineral scale the following products can be applied:
Dissolvent for disintegration of silica based deposits – contains hydrofluoric acid.
for loosening and relief of gypsum enriched boiler scale.
for disintegration and dissolution of gypsum in predominantly gypsum containing boiler scale.