Treatment of wastewater from biomass pyrolysis and recovery of its organic compounds with char-assisted drying

This study proposes a new process that treats pyrolytic wastewater (PWW) from biomass pyrolysis with charassisted drying. It can be operated at two modes: (I) one-stage drying for PWW treatment; and (II) two-stage drying and condensation for both treating PWW and recovering valuable chemicals (e.g., acetic acid). The process is proved via drying the mixture of a char and a synthetic PWW solution containing acetic acid, acetol, furfural, and phenol at different temperatures (60, 80, and 105 degrees C) and char-to-PWW mass ratios (1.0, 1.5, and 2.0). The results, supported by density functional theory (DFT) calculations, demonstrate that under Mode I, the char captures over 97.1% of the organic compounds in the PWW at 60 degrees C and a char-to-PWW ratio of 2.0, while evaporating almost all the water. The evaporated stream can be potentially discharged into the atmosphere without condensation or condensed into wastewater with a significantly reduced content of total organic carbon. Under Mode II, the char-PWW mixture is sequentially dried at 60 and 105 degrees C, with the exhaust gases being separately condensed. This yields a stream of purified acetic acid solution (concentration: -76 wt%) concentrated by a factor of -6.3 (compared with the PWW), with a recovery rate of -29%.

Automated summary

This study introduces a novel process for treating pyrolytic wastewater from biomass pyrolysis, using char-assisted drying to simultaneously treat wastewater and recover valuable chemicals. The process can be operated in two modes, enabling efficient treatment of organic compounds in wastewater and recovery of valuable chemicals under different temperature and char-to-PWW mass ratio conditions. The results demonstrate the effectiveness of the process in treating wastewater and recovering organic compounds, with potential applications in sustainable waste treatment and chemical recovery.