In emulsion polymers, there are cross-linked polymers. This type of polymer resists better to high shear rates and are therefore very useful to keep flocs...
Flocculating polymers can be in several forms. They can be in powder form, i.e. a dry polymer, or they can be in emulsion form, i.e. a liquid polymer. Both forms of polymers have advantages and disadvantages that must be considered.
Mainly, powdered polymers require a low concentration solution. Solutions are generally found at a concentration between 2 and 5 g/L. This is due to the 100% active agent percentage in powder polymers. The operating and logistical costs will therefore be lower than those of emulsion polymers since less polymer is needed to reach the required concentration of active agents.
Storage is also a notable advantage of dry polymers. Bags of powdered polymer can be stored for over a year in a cool, dry place. Just make sure the polymer is not in contact with any source of water or moisture.
The curing time required before a dry polymer solution can be used is approximately 1 hour. This period allows the polymer molecules to develop, making them active and completely effective.
The curing time of powder polymers and their preparation creates a need for additional infrastructure. This implies a high capital cost in contrast to the facilities required for emulsion polymers. The quality of the solution is also an issue, since it is necessary to avoid forming polymer agglomerations. If these agglomerations form in the mixing tank, then the efficiency of the solution will be reduced, as some of the polymer will not be brought into solution.
Emulsion polymers require only one step, dilution, and can be used without any curing time. This greatly simplifies the infrastructure and reduces the capital costs required to prepare emulsion polymer solutions compared to those required for powder polymers.
In emulsion polymers, there are cross-linked polymers. This type of polymer resists better to high shear rates and are therefore very useful to keep flocs intact when dewatering sludge by centrifugation.
The percentage of active agents for this type of polymer is 50% maximum since it is diluted in oil to stabilize it. The concentrations are generally between 2.5 and 10 g/L, which implies a higher cost per volume of polymer than the cost for powdered polymers.
The shelf life of emulsion polymers is approximately 9 months in a cool, dry place. As with powdered polymers, contamination by water and exposure to cold should be avoided. It is possible, during storage, that the oil and polymer molecules settle. The effectiveness of the product is then affected. Frequent stirring of the emulsion polymer tanks is necessary to avoid this settling.
|Cross-links are only available in dry polymer version
Cross-links resistant to high shear rates
|100% active agents
(Solutions between 2 and 5 g/L)
|Maximum 50% active agents
(Solutions between 2.5 and 10 g/L)
|More than one year
About 9 months
|Store in a cool, dry place
Store in a cool, dry place.
Needs to be mixed to avoid settling.
|Needs more attention
Requires less attention
|Health and safety