Online NMP-water analysis 1

[sshep]

Any suggestions for an on-line process measurement method for water in NMP (N-Methylpyrrolidone)?

We use a target 96%NMP,4%water mix as an extraction solvent. The NMP regeneration process strips the water from the NMP, resulting in the control problem of getting our solvent back to the appropriate water level. Currently this is done by temperature inference, but the resultant variation in solvent composition is preventing us from tightening our product specifications. If there were a more direct measurement to use to control our water concentration, it would help improve our process capability greatly.

Any recommendations on NMP-water measurement or inferential alternatives (NIR, dielectric, etc) is appreciated.

best wishes,
sshep

 

[reena1957]

Hi,
My Humble suggestion: A Delta Temperature at the appropriate section of column, i.e, Rectification or stripping -NOT top to bottom- ( preferably corrected for pressure variations) may be appropriate for more precise composition control, than a single temperaure control. This has been checked to a very good accuracy in Benzene toluene-xylene systems. The pressure correction is applied by subtracting another Delta T from the other section of the column which represents variation of temperature with pressure. In the second case of using the difference of two Delta T's, it is called Double Delta T control.

 

[sshep]

Interesting, and analogous to the qualitative approach of looking at temps which most of the panel operators use to make water adjustments. Worth considering for sure. Thanks, sshep