Recovery of Nitrobenzene

Customer:	Petrochemical industry
Location:	Western India.
Tower Name:	Waste water stripper.
Tower Diameter:	800 mm.
Mass Transfer Equipment:	Valve trays.

History:
Company is a leading manufacturer of Nitrobenzene, Aniline, and Toluene Di-isocynate.

Process Overview:
One of the main finished products, Nitrobenzene (NB) stream from the plant is washed with water to remove dissolved acids. The resulting effluent water containing some amount of NB needs to be further stripped in the steam stripper to reduce the NB concentration, thus reducing load on the ETP plant.

Customer Requirements:
Client in order to increase their capacity was in the process of revamping the NB plant. The client wanted to check if the existing steam stripper with valve trays having a capacity of 12m3/hr could handle the effluent generated from revamped plant generating 16m3/hr of effluent after revamping.

Problem analysis:

KEVIN studied the existing stream stripper and concluded:

- The existing trays would not sustain the increased load of 16m3/hr.
- Final bottoms from the existing column contained 1600-2000 ppm of NB,
this effluent resulted in increased load on ETP plant since the COD value was high.
- The pressure drop of the column was high which was resulting
in increased energy consumption.

Solutions provided:
KEVIN suggested replacement of existing steam stripper valve trays with High capacity valve trays to reduce the pressure drop across the column and increase the column capacity to 16m3/hr.

The column hydraulic ratings using Mega valve trays was done, KEVIN had internally anticipated reduction of NB concentration of effluent to 500-800 ppm level.

Accordingly the trays were manufactured, supplied & installed.

Results achieved:
The steam stripper with Mega valves after commissioning achieved
- Enhanced capacity of 16m3/hr.
- Reduction of NB concentration to 600 – 1000 ppm level.
- Recovery of 300 Kg/day additional NB from the effluent.