Visual experimental study on the effect of heat exchange area on the evolution of biomass pyrolysis vapors in a vertical indirect condensing field

•Condensation of pyrolysis vapors was visualized with different heat exchange areas.•The vapor evolution curves were described by bio-oil inversion and function fitting.•Increasing heat exchange area failed to improve the recovery of low-boiling water.•The recovery of organic components increased by 20–40% with unchanged water recovery.•The contents of high value-added compounds increased by 30–45% at high bio-oil yield. The effect of heat exchange area on the componential evolutions of biomass pyrolysis vapors was visualized through an innovative combining method of bio-oil composition inversion and function fitting. As the maximal diameter of condenser at 340 K increased from 35 mm to 55 mm, the fitted heat maps showed that the recovery of organics increased in the top of condenser and remained steady in the bottom, whereas the water recovery only increased in the top but decreased in the bottom. The recovery proportion of furfural and phenolic compounds increased by 20–40% with unvaried water recovery, and the content enrichment of high value-added components increased by 30–45% at 37 wt% of bio-oil yield. Heat exchange area exhibited a finer regulation effect on the condensation of pyrolysis vapors than traditional condensing adjustment methods, which first provided a remarkable promotion for the recovery and enrichment of organic components without improving water recovery.