TDS Levels and Cooling Towers

If possible, get recommendations from the equipment manufacturer. In the absence of specific info, one rule of thumb is to calculate the amount water evaporated in the cooling tower or condenser, and supply twice that amount (evaporating half and bleeding off half).

may be u can consider the TDS standards for Boiler

that may help u in cooling tower blowing down

Discuss the issue with the tower treatment chemical supplier. They will err on the low side, as it is in their interests to supply more chemical.

It depends largely upon the composition of the make-up water as to the ideal blow-down setting. The remainder is based upon site-specific experience.

Also depends on your local environmental effluent discharge standards. If your standard is < 3,000ppm, then you should blow down before it reaches this figure.

Good point.

This in particular makes the set point site-specific.

As someone already pointed out, it depends upon the quality of makeup as well as your environmental restrictions if any. Not to mention the chemicals and the cost/availibility of water.

You got to start with analysis of your makeup - ca, mg. ,si, co3, so4, TDS etc. Then you need to figure out how much concentration you can allow of "each" of these consitutents. The concentration is inevitably caused by evaporation. If you serach the net you would find the limit of each of these constituent without chemical addition. This is called cycle of concentartion (COC), depending on your influent analysis the COC can be anywhere from 3 to 8. Then calculate the evaporation which depends on your cooling tower range. This can be done by heat balance, or you can use a conservative thumb rule " 1% of circulation rate evaporation for every 10°F temperature range across the cooling tower.

Once you have the evaporation, COC and the drift (assume .01% of circulation), then blowdown can be calculated (search for the formula it is widely avaialble).

Also if you find that your blowdown is too high, then you may think of adding chemicals. Before you use any propritory chemicals, first consider acid injection (typically 98% H2SO4). This will stabilise the pH as well as convert some of the insoluble co3 to more soluble so4, which means you can allow some more concentration before scaling starts. Having done this you may take professional help to find out what other chemicals you should inject (dispersent etc.) depending on the cost/avaialibility of water.

We have tried the new system with non chemical anti scaling device. we success to solve the fresh water inlet scaling and reduce the existing scaling issue.

we have tried till TDS of 8000 however scaling is not happening. we have save water blowdown quantity and chemical.

Hi John

We are also playing around with chem-free antiscaling approaches. May I ask for more detail on what exactly you are doing to achieve these impressive results?

Thanks

Dear Mr. John

IN this CR4- Link

https://cr4.globalspec.com/thread/46708/TDS-Levels-and-Cooling-Towers

You have posted a reply for a posting on TDS of COOLING TOWER WATER and the question and your reply is as follows:

Pl. post details suchas:

1. How you have maintained 8000 ppm in the cooling tower circulating water.

2. what is the Water circulation Rate in the cooling tower., What was the plant capacity, what was the Temp., limits of In and Out water of cooling tower.

3. What is the quantity and percentage of make up water used, How the blow down water was disposed and treatment details before disposal of blow down water.

4. What was the wet-bulb Temp., Raw water analysis, like TDS and pH and details of Dissolved Solids present in the raw water.

5. What was the COC maintained.

Pl. post the reply in this forum or post by mail by Personal Messaging option.

I have also posted a reply for this thread.

Thanks,

DHAYANANDHAN.S

The Original Quiery

Dear Mr.Priyan,

From your posting, it appears that you are taking only TDS is the criterion for the Cooling Tower Water, and its working.

It is NOT the TDS alone to be considered for the Cooling Tower Water, and TDS is one of the Several Factors.

There are several Factors to be considered, mainly for CORROSSION and SCALING EFFECT, in the system. Scaling will reduce the HEAT TRANSFER in the CONDENSER, and with in the cooling tower, the scale will get deposited in the fill bars and increase the load on Supports. CORROSSION will eat away the metal.

The water to be used is to be analysed for RYZNER FACTOR and LANGELIER FACTOR is to be considered and decide the treatment, which will control CORROSSION and SCALING, and elements like Calcium, Magnesium, Chlorides, Sulphates, Turbidity, Silica, etc.

However, to answer your question, the TDS of Make up Water should be 500 to 550 PPM and for Circulating Water Max. should be in the range of 3000 to 3500 PPM. If COC is to be indicated, it should be in the range of 4 to 4.5.

Thanks,

DHAYANANDHAN.S