Practical Cooling Tower Range 1

[JoeChem]

Greetings,

I am considering the installation of a cooling tower for use in an essential oils distillation plant. The tower will be used for cooling hot water from overhead condensers. The exiting condenser cooling water is very hot, around 170-180 F. Is there a practical maximum entering temperature for cooling towers? Will a high temperature range such as indicated cause excessive fouling problems and require excessive chemical treatment? I am sure the evaporation losses will exceed 10%.

Any help/insight will be greatly appreciated.

JoeChem

 

[pmureiko]

The water treatment folk can give better info., but my guidance has been to design for a maximum of 130 to 140 oF on CTW exiting a heat exchanger. At higher temperature you will accelerate fouling and scale. Also the cooling tower will require special fill design, since the plastic fill on new, high-efficiency units is limited to a return temperature of about 150 oF.

Can you increase the water flow rate through the cooler to reduce the water exit temperature? This will help reduce the cooler area since the Delta T will go up.

With these high temperatures, you may want to consider heat integration to recover this energy or using an air cooler unit which would give good service.

 

[MJCronin]

joe,

Try the folks at Marley Cooling Tower (

http://www.marleyct.com)

You should try to stay with a standard CT model....they will calculate evaporation and "drift" for you

I believe 130-140F was the range that I was quoted fo a unit some timie ago...

What is your flowrate and desired outlet temperature ?

MJC

 

[JoeChem]

MJC

Thanks for the reply. I have looked into some literature from Marley...lots of good stuff on their web site.

I am about to investigate the feasibility of using a cooling tower further. I need to get into the distillation plant and find out some details (actual temperatures and flows). I believe the flow rate of water to be cooled is currently about 50-60 GPM. The is city water that is used and sent to the sewer - hence the idea of adding a closed loop/tower. If the exiting temperature of the condenser cooling water is as high as 180 F, we will certainly consider higher flow rates in a closed flow loop to lower the tower inlet temperature to a more manageable range, say 120-130 F.

The tower water outlet temperature will need to be in the 90-95 F range for a reasonable sized tower. This temperature is higher than the current city water temperature so we have some heat transfer calculations to do.

After we have some more data I am certainly going to check in with Marley.

Thanks for the help

JoeChem

 

[krecian]

JoeChem,

As the folks have already suggested:

1. consider using heat recovery exchanger before sending the hot water to CT. Reduce the temperature to manageable range

2. Increase water flow rate in the condensers to reduce CT inlet temperature

3. Evaporation losses will be 8-10 % if your CT brings it down to 90-95 deg F. But check max and min wet bulb temperature in your area. You can cool the water in CT by 6-8 deg F above WB.

4. As you are loosing nearly 10% water by evaporation if you use CT, check your water cost. (In many places water is more precious than oil). You can consider recycling that water if you use alternative method for cooling.

KRECIAN

 

[StoneCold]

If you only have a small flow (50-60gpm) you may want to consider a closed loop cooling unit instead of a tower. We have small towers and the water gets very dirty very fast, and the constant addition of chemicals is a problem. I would caution you about changing the cooling water temperature on small distillations as well. I have seen some problems with subcooling develop when the cooling water temperature was changed. Good Luck

 

[davefitz]

at 170-180 F it may be feasible to have a 2 stage cooling process. Stage 1 may be a dry cooling tower , possibly natural draft with the high heat head available.

The discharge from stage 1 would feed stage 2 , which is a wet cooling tower. This assumes your process needs cold water from stage 2 at wet bulb temp + 6F.

Krecian had a better thought- first use a heat recovery loop if some other process requires the heat.