Sulfuric acid quantity calculation for Cooling tower

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Hello everyone.

I have a question how to calculate sulfuric acid injection capacity for cooling tower. i have no experience cooling tower chemical plant so i need everyones detail opinion. Please refer to below data to calculate sulfuric acid capacity.

Make-up Alkalinity : 65ppm(as CaCO3), Cooling tower target Alkalinity(pH 7.5) : 70ppm(as CaCO3)

Cooling tower COC : 5, Cooling tower make up rate : 315.74m3/h

Sulphuric acid 98% shall be used for cooling tower chemical plant.

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3 Answers

I'm not sure what exactly ...

I'm not sure what exactly you are looking for but if you want to calculate the amount of acid you might need, you can use some applications or websites that calculate it for you. you just add the parameters and the amount of water and it'll give you an answer. but because there are some other parameters involve, you must monitor it yourself too.

by the way, often for cooling towers the optimum range is 7.8 - 8.3

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Firstly you need to ...

Firstly you need to calculate the mass of alkalinity in your cooling water (CW) system. Then you calculate what the make up and blowdown rates are per 24 hours and the mass of alkalinity for both. Add the raw water alkalinity to the total alkalinity and subtract that lost to blowdown. Subtract the mass of alkalinity at the specification value. The remainder will be the mass of alkalinity required to be neutralised to meet that specification. Calculate the mass of sulphuric acid required to neutralise it and divide by 24. Set your dosing pump to deliver that value per hour. 

 

Note that this assumes that your only source of make up is raw water. If you have varying sources of make up, it is WAY more complicated and you're best off installing an alkalinity analyser and controlling your dosing pump using the analyser analogue output. 

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Each mole of bicarbonate you ...

Each mole of bicarbonate you need to neutralize will require 1/2 mole of sulfuric acid.

at 5 cycles of concentration, you will need to reduce the incoming bicarbonate down to 14 mg/l (14 x 5 = 70).

(65-14 mg/l)(1g/1000mg)(1 mol/100g) =  5.1E-4 mol/liter

Sulfuric acid is diuretic meaning it has 2 hydrogen released per mole.

(5.1E-4 mol/liter)(1/2)(1/98%)(98 g/mol)(1000mg/g)=25.5 mg/l.

 

(25.5 mg/l H2SO4)(315.74 m3/hr)=8.05 kg H2SO4 98%/hr.

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