(179g) Entrainment of Heavies from a Tray Column

Quality of Mono Ethylene Glycol (MEG) got deteriorated on April 21, 2012, for the first time since the commissioning of Di-Methyl Carbonate (DMC) train.  UV 220nm transmittance of MEG reduced to almost nil, as against the specification of 80% minimum. This problem was investigated by collecting plant data, running simulation models and carrying out laboratory tests. 

The decrease in UV transmittance of MEG was due to entrainment of heavies from a Tray Column, supplying methanol to DMC train from another production facility. Heavies reacted with ethylene carbonate in DMC train and product of reaction deteriorated the quality of MEG.

A simulation model was developed for the Tray Column, from where the high boils entrained. Actual performance of the column was evaluated and the results of simulation indicate presence of high boils is not possible under normal circumstances.  Methods to prevent the presence of high boils in methanol are discussed in this report, so that production of fiber grade MEG can be sustained.

Estimated production loss was about 7200 MT, equivalent to SR. 5.4 million. Recommendations are given to prevent recurrence of deterioration in MEG quality.