CO2 vs H2SO4

[zouzounia]

Hi everybody. I would like to learn the advantages & disadvantiges of using CO2 instead of H2SO4 for ph reduction in a water treatment plant.
Thank's.

 

[sshep]

The primary advantage is that CO2 has less exposure hazards than strong acid, and control is easier due to the buffer solution that forms. The buffer solution effect will mitigate the effects of over addition which can be quite serious with a strong acid based system. There may be a cost advantage also.

In several of our plants we have changed to CO2 based nuetralization with very good results. Praxair was really pushing this technology at one time so maybe they can be a good contact for evaluating a CO2 based system.

best wishes,
sshep

 

[bimr]

The big disadvantage is cost. It is difficult to dissolve the CO2 in water, so you end up with an inefficient reaction. The gas escapes into the air rather than the water. The best systems use a staged dissolving process, where you first dissolve the CO2 into a carrier water stream. The carrier stream is then added to the process stream to change the water pH.

http://www.digital-analysis.com/CarbonDioxide.htm

Additionally CO2 is not corrosive as a gas, however, since CO2 is heavier than air asphyxiation is always a hazard.

You also should be aware that the dissolved CO2 increases the water alkalinity. If you have water with hardness in it, you can create a water that has the potential to scale.

http://www.phcontrol.com/wt2.htm