Dimethylformamide (DMF) RECOVERY PLANT

DMF RECOVERY PLANT
FOREWORD
The DMF distillation unit can be designed for a capacity from 2.000 kg/h of water solution to 15.000 kg/h or more, according to our standard design.
The DMF concentration in water can vary from 20% up to 30%, but it is even possible to take into consideration different concentrations (i.e. 10% ÷ 50%).
For plants having a capacity over 2.500 kg/h a multiple effect distillation unit has been studied, in order to reduce the energy costs, with the recovery of the heat from one effect to the other one. Recent thermal compression system has been developed.
MFC has already designed and operated a four effects plant: the first effect operates at the atmospheric pressure, the other three under vacuum up to a capacity of 50,000 kg/h at 25% of DMF.
For plants having a capacity lower than 2000 kg/h, a batch distillation unit can be designed.
PROCESS DESCRIPTION

The process application can be offered in the following fields:
DMF recovery from polyurethane synthetic leather manufacturing plants;
DMF recovery from PU elastic filament production plants;
DMF recovery from acrylic fibre production plants;
DMF recovery from pharmaceutical plants.
DMF recovery from food production plants.
Similar process can be also used for DMAC (dimethylacetamide) recovery plants.
The typical recovery plant includes the following units:
DISTILLATION UNIT
The DMF-H2O solution, coming out the above unit and the production lines, is fed from the intermediate storage tank to the evaporator of the distillation column to feed the column with a vapour-phase mixture.
Water vapours coming from the top of the distillation column are condensed and collected in a holding tank: part of the water is used for reflux and the excess is sent to the DMA stripping unit to reuse all the water into the vapour washing unit and into the production lines.
A side stream on the column is provided to purify DMF vapour removing DMA and HCOOH.
It is needed to purge the evaporator and the reboilers periodically to remove polymers, heavy products and formic acid: the purge stream is collected into a squeezing column in order to improve the recovery yield of the DMF DMA Stripping unit
The waters coming from the top of the distillation unit, contain small quantities of DMA (dimethylamine) which is a product of DMF hydrolysis. Before to recycle such waters it is necessary to remove the DMA in a proper stripping unit.The waters with a content less than 20 ppm of DMA exit the bottom of this column and can be completely reused in the process; DMA can be removed as a concentrated stream from the top and can be burned.

Squeezing Column unit
The purge streams from the distillation unit are re-evaporated again in order to have a further separation of the DMF from formic acid and low polymers.
A special design of such unit can increase the overall recovery yield up to 99,5% in relation to the purity of the DMF-H2O initial feed.
Low polymer together with formic acid can be discharged as concentrated liquid mud.

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