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In many industries process water is used. Water is applied as cooling agent, solvent and means of transport. To save costs, process water is recycled.

The recycle of process water is not a closed system. In cooling towers, open ransport systems and while emptying reactors, water evaporates. The dissolved substances remain behind in the circuit. Freshly supplied water again contains new salts. This way, the concentrations of salts and reactants in process water become ever higher.

In  open systems rain and wind introduce additional pollution, like sand, clay and bacteria. Monocells and algae will grow. 

All in all a recycle is good for saving water but unwanted matter will accumulate. Aided by dissolved oxygen, carbon dioxide and sulphur compounds from the atmosphere, the accumulating substances combine to form persistent scaling on the inside of equipment; undissolvable lime (CaCO3), sulphates, phosphates, oxides and hydroxides (corrosion), clay, algae. This way, the water recycle slowly but surely fills up with sediments:

The  Sirius Effect
There are chemical solutions to these problems. But to prevent that in the crisscross of substances new sediments are formed, or the environment is harmed, Sirius offers optimal and specific solutions.

Phosphonic acids
Phosphonic acids form complexes with metal ions (sequestrations). This way, Ca2+ and Fe2+/Fe3+ can not form lime, sulphate (CaSO4), phosphate (Ca3(PO4)2) or corrosion (FeO/Fe2O3).

  • ·          ATMP is the cheapest phosphonic acid preventing lime and corrosion. On the other hand, ATMP itself is sensitive to oxidation.
  • ·          HEDP is more proof against oxidation and protects metals even in the presence of agressive substances such as chlorine compounds.
  • ·          DTPMP excels in prevention of sulfates next to lime, even in very alkaline environment (pH 10-15). It also stabilises chlorites and peroxides.
  • PBTC is even more resistant to chlorine compounds and Fe3+. It stands out from the other phosphonic acids because PBTC contains polycarboxylic groups. This gives an extra boost in keeping equipment clean. And PBTC thus contains relatively less phosphor, making it more environmentally friendly where phosphates (eutrofication) are concerned.

 

Polycarboxylic acids
Polycarboxylic acids are water dissolvable poly acrylates with an organic acidic group. This acidic group superbly prevents lime formation. Some of these polymers also prevent phosphate formation, but to prevent precipitation of other salts, a combination with phosphonic acids remains necessary. Being good dispersants as well, the polymers also break down sediments already present.
Four special mentions:

  • HPMA: functions at high process temperatures and in alkaline environment
  • AA-AMPS: functions at high pH and high water hardness. Besides lime, AA-AMPS prevents precipitation of phosphates and zinc salts.
  • PESA and PASP: these polymers, preventing lime and phosphates, are also biologically degradable

 

Biocides

Benzalkoniumchloride; a cationic surfactant killing bacteria which feed on phosphates (eutrification), sulphates and iron. But it is not effective against molds and funghi. And cations can not be combined with anionic polycarboxylic acids. Neither does it mix with chlorophenols. In case benzalkoniumchloride causes too much foam, we add an anti foaming agent.

Isothiazolinone kills most bacteria and algae, molds and funghi. It combines well with chlorine, anionic, cationic and non-ionic substances. Moreover it is biologically degradable.

Never use a biocide too long. Bacteria, algae, molds and funghi can become resistant.

Based on your water quality and environmental constraints Sirius advises the best combination of chemical water treatment. Send us a sample of your process water or sediment and Sirius will send you a sample of the solution!

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