A biomass fractionation apparatus includes a vessel having a processing chamber, an inlet configured to receive a biomass into the processing chamber, and an outlet configured to discharge processed biomass from the chamber. A bed plate is movably positioned within the processing chamber and includes a plurality of elongated fins extending outwardly therefrom in substantially parallel spaced-apart relationship. A cylindrical rotor is rotatably secured within the processing chamber in adjacent, spaced-apart relationship with the bed plate. The rotor has a plurality of elongated blades extending radially outwardly therefrom in circumferentially spaced-apart relationship. Upon rotation of the rotor, the blades are configured to accelerate a biomass within the processing chamber against the fins of the bed plate and to cause the bed plate to pulsate against the rotor.