A method for preparing an aqueous suspension may include providing a fibrous substrate comprising cellulose having a Canadian Standard freeness equal to or less than 450 cm.sup.3, and microfibrillating the fibrous substrate in an aqueous environment by grinding in the presence of a grinding medium consisting essentially of mullite. The grinding may be carried out in the absence of grindable inorganic particulate material. The grinding medium may be present in an amount of at least about 10% by volume of the aqueous environment. The microfibrillated cellulose may have a fibre steepness of from about 20 to about 50.

Pulp fiber containing little ash is effectively recovered from a used sanitary product containing the pulp fiber and a polymer absorbent. The method according to the present invention comprises: a step for treating the used sanitary product with an ozone-containing gas and thus decomposing and removing at least a portion of the polymer absorbent in the used sanitary product; and a step for stirring the used sanitary product, that has been treated with the ozone-containing gas, in water or an aqueous solution containing an antiseptic and thus decomposing the used sanitary product into constituents. If required, the method may further comprise a step for separating the pulp fiber from the decomposition product obtained by the decomposition step.

Pulp fiber containing little ash is effectively recovered from a used sanitary product containing the pulp fiber and a polymer absorbent. The method according to the present invention comprises: a step for treating the used sanitary product with an ozone-containing gas and thus decomposing and removing at least a portion of the polymer absorbent in the used sanitary product; and a step for stirring the used sanitary product, that has been treated with the ozone-containing gas, in water or an aqueous solution containing an antiseptic and thus decomposing the used sanitary product into constituents. If required, the method may further comprise a step for separating the pulp fiber from the decomposition product obtained by the decomposition step.

A sheet manufacturing apparatus includes a classifier unit configured to classify by air flow an introduced material that has been introduced, a screening unit configured to allow a classified material, which comprises fibers, that has been classified by the classifier unit to pass through a plurality of openings to screen the classified material, and a forming unit configured to use a passed material that has passed through the openings to form a sheet. The classified material is supplied to the screening unit by the air flow.

A sheet manufacturing apparatus includes a classifier unit configured to classify by air flow an introduced material that has been introduced, a screening unit configured to allow a classified material, which comprises fibers, that has been classified by the classifier unit to pass through a plurality of openings to screen the classified material, and a forming unit configured to use a passed material that has passed through the openings to form a sheet. The classified material is supplied to the screening unit by the air flow.

A device and method for cleaning contaminated solid-liquid mixtures by removing impurities and contaminants from an aqueous paper fiber suspension by flotation. Apparatus includes a first conduit (2) for a liquid, a second conduit (3) for a solid-liquid mixture, a third conduit (4) connecting first and second conduit (2, 3), a Venturi mixing element (5) with cones (7, 11), having small through-opening into chamber (9) which forms a cavity with small through-opening (12, 13) of the cones; the through-opening of first cone (7) connected with first conduit (2) and the rough-opening connected to second conduit (2), the small through-opening (12) of first cone (7) and the non-conical conduit sections arranged in longitudinal axial alignment, a fourth conduit (6) for conveying gas, wherein the fourth conduit (6) opens to the Venturi mixing element (5), and a fractionator arranged downstream of the second conduit (3) for removing the foam produced by flotation.

A method for treating composite materials of aluminum and plastics mixes the composite materials in a working area of a processor under high shear forces with a spiral in order to remove the aluminum layer from the plastic layer and to suspend it. The particles which are separated by a screen from the working area are treated in a hydrocyclone in order to separate aluminum from the liquid, wherein fibers present in the underflow are fed back with the liquid to the processor.

A method for treating composite materials of aluminum and plastics mixes the composite materials in a working area of a processor under high shear forces with a spiral in order to remove the aluminum layer from the plastic layer and to suspend it. The particles which are separated by a screen from the working area are treated in a hydrocyclone in order to separate aluminum from the liquid, wherein fibers present in the underflow are fed back with the liquid to the processor.

A method for separating fibers using a container, a vacuum pump which is connected to the container volume via a vacuum valve, and a ventilation line with a cross-sectional opening and a valve. The valve can be switched between a closed and open state in a time domain of 19-41 ms and from the open state into the closed state in a time domain of 20 to 45 ms. The method has the steps of filling the container with water and fiber composite, closing the container, mixing the water and the fiber composite using mechanical energy, by stirring, generating kinetic energy in the fiber composite by lowering the container internal pressure to a value between −700 to −950 hPa, and equalizing the pressure in the container to generate cavitation in the fiber composite. The pressure equalization taking place within at least onetime domain of 0.001-1 s.

A method for separating fibers using a container, a vacuum pump which is connected to the container volume via a vacuum valve, and a ventilation line with a cross-sectional opening and a valve. The valve can be switched between a closed and open state in a time domain of 19-41 ms and from the open state into the closed state in a time domain of 20 to 45 ms. The method has the steps of filling the container with water and fiber composite, closing the container, mixing the water and the fiber composite using mechanical energy, by stirring, generating kinetic energy in the fiber composite by lowering the container internal pressure to a value between −700 to −950 hPa, and equalizing the pressure in the container to generate cavitation in the fiber composite. The pressure equalization taking place within at least onetime domain of 0.001-1 s.