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[hiren_d]

Dear All,

 

We are running multi product pharma plants, which are generating high COD effluent streams.

 

The high COD stream is mainly containing, 

1. low boiler mixed solvents(Boiling point < 100 C) like MeOH, Ethyal Acetate, IPA,MDC, Acetone, THF,EDC,n-Hexane ,Acetonitrile etc.
2. Water solble Organics+ Inorganics which are coming from either excess raw material or by products of the reactions .
3. High boiler solvents like Toluene, DMF, DMSO etc. (Boiling point > 100 C).
4. Reverse osmosis plant reject stream with arround 25000-35000 ppm Total Dissolved Solids.

The stream COD ranges from 1,00,000 to 3,00,000 ppm.

 

We are having zero discharge system consisting Stripper + Multiple effect evaporator + Agitated thin film dryer to seperate solvent - Concentrating effluent- & finally removal of dry organics+salt.

 

COD reduces 50% after stripper stage, which is carring forward to MEE & ATFD ,due to dissolved organic +inorganic & high boiler solvents.

 

The problems we are facing are:

 

1)The stripper can remove low boilers solvent (& some water also) only & Organic+Inorganic salts+ high boiler solvents are carried forward & at last stage (From ATFD) we get sludge + slurry instead of dry powder which comes in molten form & solidifies very hard in the wet cake collection container and ATFD itself.

Frequent shutdown reduced efficiency of the unit & increases maintanance cost for de-chocking.

 

2) Recovered solvent from stripper top (@ 85 C stripeer top temperature) contains about 50% solvent & 50% water?This solution again needs seperation in batch still/packed column to get mixed solvent recovery.

This increses overhead costs.

 

I am thinking to add any oxidising agnets which can oxidise this organic+inorganic mass(responsible for stickyness in salt wet cake).

 

Examples of such additives are: 

Hydrogen paroxide

Sodium Hypochloride

Chlorine    

   

Please suggest me wheather I am going in proper direction or any other way to break this organic & inorganic.

% w/w of organic , inorganic & low boiler, high boiler are unknown due to multi product facility.

Thank you in advance.

 

Regards,

Hiren Dave  

[sgkim]

Hi, Dave,

 

Even with the oxidizing agents listed could not solve the residual matter problems because the solvents and inorganic matters are not so reactive.   Organic materials which contains chlorine or sulfur in the molecule shall be collected separately, incinerated and recovered as hydrochloric acid solution and sulfate salts respectively.  The other mixed solvents with residual organic matters could be incinerated together with residual water in the mixture.

 

Sticky wet cakes from the ATFD would be troublesome making frequent shut-downs.  I recommend, drawing it off as <slurry> rather than as <sticky cake> from the film dryer, and mix the slurry with <complete dry powder> of the cake itself, then dry in a separate dryer completely.   The <amount of the dry cake> to be mixed would be "critical" to solve your problem.  Some try-and-error might be required.       

 

ZD (zero discharge) would commence from each specific source of wastes.  No valuable material could be recovered economically from "hodgepodge".

 

Stefano G. Kim