URGENT - Save water in cooling towers 1

[jisita]

Hi, as I commented on my last thread (thread164-111386) I want to improve my cooling towers. Currently we are running at an extremely low 1.66 concentration cycles…

We use deep well water, and we chemically treat it with Sulfuric Acid, Biocide, Hipoclorite and multifunctional chemical.

But we need to reduce the water consumption, I have many doubts about what could be done.

1. What can we do in order to reduce the cooling towers use of water?
2. Is there a way to recover the water loss by evaporation?
3. We have a system for controlling the operation of the towers fans based on water temperature, could we also control the flow of water from the pumps? If yes, could I save water in that way?
4. They are proposing me to treat the blowdown with a Ion Exchange system in order to reuse it in the towers, do you think it is a good idea?
5. Is it better to treat the make-up water?
6. Another suggestion?

I really appreciate your help,

José

 

[oxilume]

Jose,

You should have questioned the water treatment chemical salesman long before cycles dipped below 2.

The very first thing you need to do is conduct a mass balance across the tower, heat exchangers, etc. Have your chemical salesman do this. It is part of the service.

Todd

http://www.oxilume.com

 

[LHA]

1. What can we do in order to reduce the cooling towers use of water?
The steam released is just under 40% of your total water usage. Recapture this water if possible.

2. Is there a way to recover the water loss by evaporation?
Perhaps a pre-heating system for the primary steam is possible. I don't know what your process is, and a new heat exchanger will be a very high initial cost. But it could pay for itself.

3. We have a system for controlling the operation of the towers fans based on water temperature, could we also control the flow of water from the pumps? If yes, could I save water in that way?
Install VFDs on the pump motors, then use the existing water temp and/or conductivity sensors to signal the VFDs. You will save water and electricity, but keep in mind the pumps will then operate at different (probably lower) efficiencies, so slip and wear will increase. There is much debate about the trade off of energy versus efficiency and slip. Research relative to your system characteristics before you jump to VFDs.

4. They are proposing me to treat the blowdown with a Ion Exchange system in order to reuse it in the towers, do you think it is a good idea?
That sounds expensive, labor intensive and leaves much room for operator error. It can certainly be done though.

5. Is it better to treat the make-up water?
Not enough info here to answer that, but this is certainly easier and less expensive than treating the blowdown.

6. Another suggestion?
The steam released is just under 40% of your total water usage. Its condensate would be almost pure water, and would therefore dilute your other concentrations at the same time, greatly reducing pretreatment. The feasable to capture any of the evaporated water and re-condense it is worth investigation, and will make your Feasability Report more complete.

 

[krb]

Try

http://www.aquatech.com/pdf/pilot.pdf

KRB

 

[abcmex]

Jose,
To improve your operation you need basically to check several things.Apparently you have already implemented a chemical conditioning program but you Concentration index is still low (1.6). Which is the limiting condition? Discuss this with your treatment provider and even invite a new one ot present you an alternative.

To try to treat the blowdown is always a good idea but perhaps you should evaluate if you need to pretreat the makeup. It is much easier!

Kind regards

 

[aicmexico]

Jose:

Since this is not a commercial forum I will not get into to much details, but I do know a company who owns a technology that can deal with your problem.

Try to contact them at

http://www.aquatech.com.

I know they have a local representation in Mexico

Let us know if you were succesful

 

[bimr]

The aquatech process is not going to help you on this application. The use of RO equipment (as in the aquatech scheme) is not appropriate for this water because of the low flow and high hardness and silica. Using RO on the blowdown from the cooling tower with the high hardness and silica will be a disaster.

You best bet is to treat the makeup water (not the blowdown) with a water softener followed by a RO unit. The RO unit will need to be operated at low recovery to minimize the possibility of scaling in the RO unit. Unfortunately, this will be an expensive system to operate for such a low water flow and you will also consume water in the water treatment process.

 

[aicmexico]

I generally agree with bimir on his perception of the aquatech process, basically becuase the process is good when the alkalinity/hardness ratio is bigger or equal to 1.

But I also know that this process can deal with high silica concentrations at the reject (up to 2000 ppm), that means that this proccess can tolerate up to 200 ppm in the feed and achieve 90% recovery.

Maybe the problem can be attacked from the raw water side, where hardness is not as big as in the CTBD, the High Efficency RO of aquatech will maybe be able to achieve 90% recovery and the quality of water will be good enough to increase your CT COC.

Also, and if your final goal is to reduce water consumption, this proccess can also treat a waste water stream available in your plant, process it, and make a good CT Make Up.

I do know that this process is working at a Combined Cycle Power Plant in Mexico, treating a municipal waste stream, converting it into high quality DI water for boiler make up.

You dont lose anything onto exploring this possiblity

 

[bimr]

The points that I was making are that:
1. The use of RO or IX for that matter, on ct blowdown or wastewater is problematic and should only be encouraged as a last resort.
2. Since the application here is small, the cost of operating the water treatment system is probably going to be more than the water savings.
3. The aquatech system is entirely too complex for this small application and user. Aquatech would probably not be competitive in the supply of a small RO system here either.

If jisita puts in a water softener/RO on his feed water he will reduce his water usage from 431 to 249 m3/day. The daily water saving will be 182 m3/day (48,000 gal/day). This is going to cost him $250k to $300k (installed. The RO operating cost is $.70/ cu. meter. If my numbers are correct that's $175 per day. Note that the operating cost does not include operating personnel cost.

Unless the cost of water is high, it will be hard to justify the water treatment. The average price of water in the United States is about $1.50 for 1,000 gallons or $.40/cu. meter. If he saves 182 m3/day of water, that equates to only $75 per day.

Existing With Water Treatment
water usage
water input 431 249
evaporation 168 168
blowdown 262 19
RO blowdown 0 62
Conc cycles 1.6 10