Abstract: A system for treating pulp comprises a dewatering device (2) for dewatering the pulp to a fiber concentration of at least 20%, a closed pulp-shredding vessel (16) for shredding the dewatered pulp, and an outlet pipe (22) from the pulp-shredding vessel. A transport screw (18) is arranged in the outlet pipe for transporting the shredded pulp from the pulp-shredding vessel through the outlet pipe through a reactor vessel (6) for bleaching the shredded pulp through reaction with ozone gas. The outlet pipe (22) is designed with a heightened roof portion (27), so that an upper gas space (29) free from pulp is formed in the outlet pipe between the roof portion and the transport screw. A flow-restraining member in the form of a partition wall (31) is arranged in the upper gas space in the outlet pipe for restraining the gas flow through the gas space, whereby the pumping action of the transport screw in the outlet pipe is decreased.

Abstract: Methods and systems for the treatment of pulp are provided. The methods include dewatering pulp to a fiber concentration of at least 20%, shredding the dewatered pulp in a closed pulp shredding vessel, transporting the shredded pulp without compression continuously out of the pulp shredding vessel through an outlet pipe which is kept completely filled with passing pulp, directly transporting the shredded pulp to a reaction vessel through a gas-tight conduit gas sealed from the surroundings and communicating with the outlet pipe and the reaction vessel, bleaching the shredded pulp in the reaction vessel with ozone gas, and regulating the gas pressure in the pulp shredding vessel and in the reaction vessel so that ozone gas is prevented from leaking upstream through the outlet pipe.