8 replies to this topic

[chemks2012]

Dear all,

I am working on a project wherein we will have acidic liquid waste containing HCl of about 10% to as high as 23% [by wt]. We estimate the quantity of this liquid waste would be about 800 to 1000litres per batch [estimated batch time of about 24hrs].

I am wondering which neutralising agent will be the best in terms of safety, operation, environmental issues, price etc. I think the possible neutralizing agents are Na2CO3 solution, NaOH solution and CaO powder etc but don’t know which would the best one to choose i.e. if we use Na2CO3, it will generate CO2 gas etc.

I would appreciate any input.

Thanks,

[chemks2012]

Any help/suggestion please?

[chemks2012]

Meanwhile someone suggest me what will be the better neutralising agent, I have carried out some calculations and I am wondering if someone could check please.
The attached file contains 3off work sheets

• Heat of dilution for HCl – I want someone to check if my calculation for the rise of temperature is OK
• Heat of neutralisation – NaOH - I want someone to check if my calculation for the rise of temperature as well as the amount of neutralising agent etc are OK
• Heat of neutralisation – Na2CO3 - I want someone to check if my calculation for the rise of temperature as well as the amount of neutralising agent etc are OK

Looking forward to have some inputs from genius engineers!
Thanks

Attached Files

•  Calculations Rev.0.xls   140KB   21 downloads

Edited by chemks2012, 22 February 2012 - 06:52 AM.

[Absolute Zero]

The percentage content you mentioned is quite high, try to think of recovering this quantity rather than simply just neutralization.

Usually it is better to search for a nearby industry which is generating a Basic waste containing any base such as NaOH, and then mixing the effluent of both the industries in the effluent stream to neutralize the waste. This is reduce the load of central effluent treatment plant.

[chemks2012]

Hi ZAK,

That's the good idea. Will check if it is possible.
But I still wish someone to check my calculations.

Thanks

[Absolute Zero]

Your Calculation shows that you require a high quantity of neutralizing agent either NaOH or Na2CO3 which does not seems to be economical.

You should refer to the following articles.
http://www.cheresour...lrecovery.shtml
http://eelndom1.ee.doe.gov/OIT/oitpdf.nsf/Files/beta.pdf/$file/beta.pdf

[chemks2012]

Thanks ZAK, but I am not sure if my calcs are absolutely correct!

[Dazzler]

It may also be important how pure your HCl waste liquid is, in other words what other contaminant are present that could effect neutralisation and options for reuse or recycle or mixing with other wastes.
Dazzler

[Zubair Exclaim]

ok first of all why are you calculating heat of neutralization ... secondly followingare my coments on your calculations

1-on second tab of your calculations you have taken heat of reaction from (heat of formation X moles) (Cell D36) wrong ... you already have heat of formation in KJ/Kmol multipllying with moles will cancel mol and heat of reaction wont be KJ/Kmol.........simply add and subtract heat of formations ....(multiplication is for stoichiometric coefficients in your case its all one )

2-also you have used 10% NaOH ... why? ... have you got a waste stream of 10 % NaOH from some process?,,, if no then why would you be diluting NaOH and spending water and additional cost of dilution plus problem of disposing all that volume ... commercially available solution of 50% NaOH should be used directly with a circulation pump for mixing .

3- specific heat used, whose is it... it better be the specific heat of solution after neutralization

4-for 36.5 kg of HCL you need 40kg of NaOH and 53 kg of Na2CO3 now compare their prices multiply by weight and come up with final selection of two. I think you will come up with NaOH finally

i am coming up with 32.something °C rise for NaOH against your 5°c

let me know finall results

Edited by Exclamation, 26 March 2012 - 08:28 AM.