Recovery of Cooling Water Tower blowdown 1

[22854]

I am very interested to know of different alternatives to for the recovery and reutilization of cooling water tower blowdown, instead of sending it as wastewater.-

For any of the alternatives it will be of great help to know which are the processes required to treat this water for the proposed use.

 

[Zoobie]

This is a difficult question to answer without more details as to the processes associated with the system. For example, I used to work in a plant where we sent our cooling water and boiler blowdown to our solution mining operations (brine well) for dissolving salt. Since the upwell brine was to be treated anyways, the TDS (and other junk) in the cooling water was irrelevant. My point is that this was an excellent way to reuse cooling water blowdown, but it was entirely dependent on what kind of plant it was.

It would be very difficult to provide a general answer. Things that need to be considered include:

1) What's in your cooling water....this can vary A LOT depending on geography, treatment systems, process, etc.
2) What can your end use tolerate? This can vary even more. Some process waters need to be very pure, in other cases you might only need to filter the water.
3) Only after looking at 1&2 can you begin to assess treatment options...softening, demineraliztion, precipitation, filtration, reverse osmosis, etc, etc, etc.

If you can provide a bit more detail to your query, you will likely be able to get much more informed responses. With enough money, you can turn your cooling water blowdown into the finest drinking water on the planet. However that would probably be a tough sell to management.

If you are looking at one particular plant or complex, I would start by making a list of all the places water is used and the relative quantities (in relation to your typical blowdown volumes). After removing all the items that don't make sense (like the coffee maker in the control room) you can begin to get into details.

 

[cub3bead]

A lot depends on the quality of the source water. In freshwater applications, silica is usually the limiting constituent. Unfortunately, removing silica from either the source water or the cooling water is costly.

Brine concentrators are a good way to recovery 90% or better of the cooling tower blowdown. The product water is very good, < 10 uS/cm easily achieved. The downside is the CAPEX and the OPEX.

As Zoobie points out there are a number of unit process that can and have been applied for reclamation and reuse of cooling tower blowdown, some in rather complex designs. The more complex the better as they become life time jobs programs for chemical engineers and chemists.

I would avoid trying to turn cooling tower blowdown into drinking water, way too much liability. Boiler feedwater though is a great choice. Producing and selling drinking water would do management in, remember lawyers are more expensive than ChEs, if the cost of building the facility hasn't gotten to them first.