Salt deposiotion on and around seawater cooling tower? 4

[mjohnqa]

we have recently commissioned a seawater cooling tower in the middle east region with a heat duty of 1305MW. This is achieved through a circulation of 120,800t/h of ciruculatiion of seawater. However we have noticed that during high humidity seasons, there is high salt deposit on and around the cooling tower?
Any similar experience and ways on how to combat it?

 

[rmw]

Change the cooling tower to fresh water?????

Well, seriously, you can't change it. The drift eliminators prevent most of the drift, but they don't get it all and what falls on the tower / ground evaporates and leaves behind the minereals (and chemicals if you treat at all) in the water on whatever it fell.

You might mitigate the issue somewhat by going to a more efficient drift eliminator, but none will be 100% efficient, so there will always be some fallout from the plume.

And... there are types of cooling towers that re-heat the plume to prevent visual plumes, but I doubt it can be changed now.

rmw

 

[TD2K]

RMW, that was originally my thinking but then I noticed the poster had said the salt deposition (seems) to be a problem during high humidity periods, that didn't seem to make sense to me if drift was causing the salt problems.

 

[rmw]

During periods of lower humidity, cooling tower plumes are less prominent meaning that they contain less visible moisture. It is this "visible moisture" - meaning that the plume contains more droplet sizes that can be seen with the naked eye - that is falling out and leaving the salt and minerals and chemicals behind that the OP mentions.

On a dry day, the cooling tower is more efficient and less moisture leaves in the airstream as visible droplets - with, of course the better performance and wet bulb temp. The same amount of moisture leaves the tower however, - thermodynamics dictates that, just less as visible plume.

I live in a climate where it is humid to some extent most of the times, but on those hot summer afternoons when it is dryer you really have to look closely at some CT's to see if their units are on line, and you know that they are that time of day. Driving by the same tower in the humid early morning hours, and it is like two different towers.

A perfect cooling tower would be one that evaporated the water needed to cool water adequately without having any carryover. Since that is easier to do on dryer days, there is less carryover. On humid days, every tower struggles.

rmw

 

[mjohnqa]

Exacly as said by TD2K, this usually happens during high humid climates. However changing to fresh water is not a feasible solution as the cost of production of fresh/desalinated water is very high and proximity of sea is an added advantage. The vendor of the cooling tower has guaranteed a drift loss of 0.0005%, which is yet to be proven. Main problems is the corrosion occurring on the surrounding area with pumps and instruments.

By experience we have also seen that all the cells' fans should be kept running to keep the "rain" of falling water "curved" into the tower and avoid splashing out of the air intake louvers.

Thank you rmw and TD2k for your response!!!

 

[EdStainless]

In most humid coastal areas frequent rains will tend to wash the salts and as long as you don't have any trapped or covered areas you are fine.
In your case you don't get much rain. You may need to periodically wash the effected areas with less salty water. It does not need to be potable, just clean enough to dissolve the salts.
My real concern is that you are also forming mineral scales that will be insoluble in water. This could be a source of serious under-deposit corrosion. Better coatings in the effected areas may be your only option at this point.

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