A method for dilution for a pressure screen comprising a rotor rotating inside a screen a distance to the screen, includes supplying feeding stock into a screening zone formed in the spacing between the rotor and the screen with some of the feeding stock passing through the screen into an accept area to become accept, and the remaining feeding stock discharged into a reject area as reject flow. The amount of the dilution water added into the reject flow is 0.8 to 3.5 times the amount of the reject flow by volume. Additionally, a pressure screen comprises a dilution water adding apparatus adapted to add dilution water directly into the reject area of the pressure screen, wherein the amount of the dilution water added into the reject flow is 0.8 to 3.5 times of the amount of the reject flow by volume.

Technology improving the effect of cleaning a filter by a high pressure air current is provided. A first dust collector 27 has a housing into which a gas carrying capture material is carried; a filter 240 having a filter element 305 that captures the capture material, and an opening 305b from which air passing through the filter element 305 flows out; and an injector having a nozzle with an injection opening that injects a gas, moves the nozzle to a position in contact with the opening, and injects the gas from the injection opening 305b when the nozzle is in contact with the opening 305b.

Technology improving the effect of cleaning a filter by a high pressure air current is provided. A first dust collector 27 has a housing into which a gas carrying capture material is carried; a filter 240 having a filter element 305 that captures the capture material, and an opening 305b from which air passing through the filter element 305 flows out; and an injector having a nozzle with an injection opening that injects a gas, moves the nozzle to a position in contact with the opening, and injects the gas from the injection opening 305b when the nozzle is in contact with the opening 305b.

Variation in the amount of material that is dispersed when material containing fiber is discharged by a sieve is suppressed. A fiber processing device has a drum that screens defibrated material containing fiber, a mesh belt that accumulates first screened material discharged from the drum, and a processor that processes the first screened material accumulated on the mesh belt. The drum operates at a first speed during processing by the processor; and when the drum starts from a stationary stop, a startup operation including a state in which the drum operates at a slower speed than the first speed executes for a specific time.

Variation in the amount of material that is dispersed when material containing fiber is discharged by a sieve is suppressed. A fiber processing device has a drum that screens defibrated material containing fiber, a mesh belt that accumulates first screened material discharged from the drum, and a processor that processes the first screened material accumulated on the mesh belt. The drum operates at a first speed during processing by the processor; and when the drum starts from a stationary stop, a startup operation including a state in which the drum operates at a slower speed than the first speed executes for a specific time.

Variation in the thickness of accumulated material is suppressed when material containing fiber is dispersed by the sieve and accumulated. A sheet manufacturing apparatus includes a drum that sieves defibrated material containing fiber, a first web former that accumulates first screened material discharged from the drum, and a processor that processes a first web accumulated in the first web former. During processing by the processor, the mesh belt operates at a first speed. When operation starts with the drum not operating, a startup operation including the mesh belt operating at a higher speed than the first speed in a first period after the drum starts is executed.

Technology for efficiently extracting fiber from a feedstock containing fiber. A subunit has a mesh drum configured as a rotatable cylinder with mesh in at least part of its surface, and a case that houses the mesh drum. The case has a first opening and a second opening that communicate with a first area, and a third opening that communicates with a second area. First screened material is supplied from the first opening to the first area. The subunit discharges from the third opening waste, which is a first component of the first screened material moved by an air current from the first area to the second area, and discharges from the second opening by an air current processing feedstock, which is a second component of the first screened material that does not pass through the mesh drum with the air current and remains in the first area.

Technology for efficiently extracting fiber from a feedstock containing fiber. A subunit has a mesh drum configured as a rotatable cylinder with mesh in at least part of its surface, and a case that houses the mesh drum. The case has a first opening and a second opening that communicate with a first area, and a third opening that communicates with a second area. First screened material is supplied from the first opening to the first area. The subunit discharges from the third opening waste, which is a first component of the first screened material moved by an air current from the first area to the second area, and discharges from the second opening by an air current processing feedstock, which is a second component of the first screened material that does not pass through the mesh drum with the air current and remains in the first area.

A method for controlling a fiber fractionation system for fractionating an input material into a long fraction (LF) stream comprising LF fibers and a short fraction (SF) stream comprising SF fibers includes measuring an average LF fiber length at one or more locations post-fractionation, and maintaining the average LF fiber length within a target variability range by automatically altering a rotational speed of a rotor of the fiber fractionation system.

A method for controlling a fiber fractionation system for fractionating an input material into a long fraction (LF) stream comprising LF fibers and a short fraction (SF) stream comprising SF fibers includes measuring an average LF fiber length at one or more locations post-fractionation, and maintaining the average LF fiber length within a target variability range by automatically altering a rotational speed of a rotor of the fiber fractionation system.