A fast pyrolysis heat exchanger system and method for economically and efficiently converting biomass and other combustible materials into bio-oil. The system employs multiple closed loop tubes situated inside the heat exchanger. As heat carrier is deposited at the top of the heat exchanger and caused to move downwardly therethrough, heat is transferred from the tubes to the heat carrier which is then transferred to a reactor where it is placed in contact with the combustible materials. Vapor containing char fines is discharged from the reactor into a vacuum-operated blow back filter. The blow back filter is activated when a drop in vacuum level at the output of the reactor is detected. Thereby, excess char buildup on the blow back filter elements is removed.