AbstractA rotary screw pyro‐oil reactor was designed for powdery biomass for a feeding capacity of 40 kg h−1 with a moisture content of <10%. The pyro‐oil reactor temperature was maintained at 450–550 °C. The pyro‐oil vapors produced were quickly drafted out of the reactor for quenching to yield 16–24 L h−1 from 40 kg h−1 of biomass feed. The flash‐pyrolysis technique, which is capable of directly turning biomass into a liquid fuel, was used to produce liquid fuel (bio‐oil). It was carried out at a pressure at 0.03 bar and at a medium temperature of about 550 °C. The flash‐pyrolysis technique converts the entire biomass matter, excluding the ash. In this method the powdery biomass is converted into three components: bio‐oil (the yield is typically 70% on an energy basis, a powdery biomass feed at a moisture content of 10%); pyrolysis gas (typical yield 14%) and char (typical yield 16%). The temperature of the fixed bed was adjusted in the experiment, but the other variables remained constant, such as the amount of feed, the pyrolysis time of the gas product, the reactor pressure and the bed height. A biomass particle size range of 1–3 mm and a biomass residence time of 20 s in the reactor resulted in optimal bio‐oil production of 70%. This work demonstrated how precise pyrolysis mechanism processes and bio‐oil yields can influence the maximal reaction temperature in the 450–550 °C range. The performance analysis reveals that the fixed bed reaction temperatures of biomass rapid pyrolysis give reliable control over the bio‐oil reactor type and size. This paper provides an overview of the design and thermochemical liquefaction process used to convert powdered biomass to biofuel. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd