Sagar Jiyani
Mechanical
07 Mar 2019

Naoh Scrubbing system required amount of naoh

for naoh scrubbing system how much naoh required  for 22620 kg/hr flue gas and 0.13% so2 by volume.?

Can we get a calculate?

07 Mar 2019

Theoretically two gm moles of NaOH will absorb one gm mole SO2 . However many other factors have to be considered in scrubbing flue gas. The following two papers may be of help.

Sagar Jiyani

Mechanical
07 Mar 2019

As a practically i need to give a data to our client that how much naoh required in a day or in a hour for 22620 kg/hr flue gas flow rate and 0.13% so2 by volume.

Sagar Jiyani

Mechanical
07 Mar 2019

As a practically i need to give a data to our client that how much naoh required in a day or in a hour for 22620 kg/hr flue gas flow rate and 0.13% so2 by volume.

07 Mar 2019

Assuming 1.3 kg/mFluegas density and taking into account the properties of SO2 one gets 1.86 x 40 or about 75 kg NaOH consumption/hr.

Since the efficiency may be less than theoretical a bit more maybe needed.

This is a back of the envelope kind of quick and dirty calculation. If commercial issues are involved better get it checked.

Sagar Jiyani

Mechanical
08 Mar 2019

But we can get 12 ph value of water and naoh solutions so per ltr of water 0.4 gm naoh required.so  if we used 12000 ltr water then how much naoh required per hour by reacting with sox

08 Mar 2019

From the data you indicated, the theoretical requirement to absorb the nearly 60 kg/hr SO2 produced is about 75 kg NaOH/hr.

Are you using 12 mwater/hr? Then minimum this much NaOH/hr must be dissolved in the 12 mwater used.

Sagar Jiyani

Mechanical
12 Mar 2019

sir,if we are using naoh with water solution then there is possibility to less naoh absorption? because if there is 75 kg/hr naoh required then per day 1800 kg naoh required and industrial cost increase. so there is any other sollution?

on above problem?

12 Mar 2019

Actually you will need more than that amount. 75 kg/hr is the theoretical amount of Naoh needed to absorb the amount of SOthat is present in the flue gas as specified.

You are talking about cleaning 546 tons of flue gas in a day.

Room temperature water can absorb 0.2 kg SO. So 300 litres water can absorb 60 kg SO2. This translates to only 7200 litres water per day.You have to throw away this water subject to local environment laws. You can completely avoid using NaOH.

Since you said something about 12000 litres water you may not need any NaOH.

Sagar Jiyani

Mechanical
12 Mar 2019

but our procedure is like we are adding naoh into 12000 ltr water and maintaining its ph value 10-12 ph. and this solutions we will spray on scrubber tower which convert sox into sulphuric and sulphuras acid.

and we must have to add naoh in water and solution spray in tower with number of nozzles by using 15 hp centrifugal pump. so there is any calculations or according your experience how many naoh required?

12 Mar 2019

If your requirement is only pH maintenance 4.8 kg NaOH in 12 mwater will give a pH of 12 as you mentioned before.

But the chemical reaction between SOand NaOH does need 75 kg NaOH/hr for the contamination level you have given. I am unable to suggest a way around that.

Sagar Jiyani

Mechanical
12 Mar 2019

Ok.sir..i get your mean. But if we get ph value 12 ph then reaction occurs with sox in flue gas and according gpcb norm there is 100 ppm sox allow for release atmosphere.

13 Mar 2019

The problem is that NaOH reacts with SOand gets consumed. This will drop the pH. You have to add more NaOH to bring it back to 12. According to the contamination level specified this will be 75 kg/hr.

Sagar Jiyani

Mechanical
13 Mar 2019

Ok sir..i get it ..in short i have to require 75 kg/hr naoh for complete sox remove.

13 Mar 2019

Not really. You can do it with water alone as mentioned earlier. But if a pH of 12 is specified, then you need that much NaOH to maintain pH 12 and remove the SOx by NaOH.

Sagar Jiyani

Mechanical
13 Mar 2019

as u mentioned erlier that only water spray also can remove sox from flue gases. is that possible? if es then which procedure we should follow?

13 Mar 2019

@Sagar Jiyani , I am writing from just the chemistry point of view. I have not done anything on flue gas scrubbing.We id have a small incinerator at work for bio waste, which had a scrubber for washing the exhaust gases from bio waste combustion, which did not have much SOx. We just used waterspray more to cut down dust and smoke. It has been working for many decades now.

There are stringent environment regulations now on flue gas emissions. You have to conform to applicable rules. One option that may be cheaper is to use a spray tower with limestone powder slurry.