The Enforced Ebullition Process

From the gaseous mixture reaching the condenser, most of the furfural vapor and most of the water vapor are liquefied and collected in tank 12, whereas small quantities entrained by the air are recovered in the absorption column. 

The liquor input rate and the columnar reactor dimensions are calculated to ascertain that the residence time in the reactor is sufficient for a complete disappearance of the pentose. There is no need for adding acid. 

Needless to say, instead of air, other gases can be used if this is desirable. 

All furfural reactors known so far produce a vapor stream consisting of more than 90 % water, of up to 6 % furfural, and of various by-products. After liquefaction, commonly used to make secondary steam, and sometimes after a filtration or a centrifugal separation of solids, the product stream is fed into a distillation plant. 

From the first column, commonly a tray column, a fraction roughly corresponding to the azeotrope is withdrawn as a liquid side stream and fed into a decanter 2, where it separates to form two liquid phases, a light phase rich in water, and a heavy phase rich in furfural. The light phase is refluxed into the first column, somewhat below the withdrawal point of the azeotrope. 

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