Kraft-lignin pyrolysis and fractional condensation of its bio-oil vapors

•Fractional condensation proves successful in recovering nearly water free bio-oil.•The fractionated bio-oil contains 94% of the phenolic compounds present in the original bio-oil.•The heating value of water free bio-oil is same as ethanol.•Nearly 98% of energy present in the original bio-oil is recovered in water free bio-oil.•The fractional condensation system uses electrostatic precipitator-cum-condenser (C-ESP).

Kraft lignin has been pyrolyzed in a modified bubbling bed reactor coupled with an internal stirrer, and the resulting bio-oil vapors have been fractionated using a series of three condensers maintained at different temperatures. The temperatures of the condensers have been optimized in order to selectively separate most of the water present in the bio-oil vapor stream and increase the quality of the remaining bio-oil. The condenser train comprised of an electrostatic precipitator-cum-condenser (C-ESP) installed between two cyclonic condensers. The fractionated bio-oil was found to be rich in phenolic compounds with a water content of less than 1 wt%. The effect of pyrolysis temperature on the fractionated bio-oil yield and characteristics is also discussed.