Abstract: A method and apparatus thickens lime mud with a disc filter in such a way that the precoat layer on the filter surfaces of the disc filter can be cleaned. Beneath the scrapers for scraping a dry layer of lime sludge from the precoat layers on the disc filter wires surfaces one or more high pressure nozzles, and optionally a low pressure nozzle, are provided for directing jets of liquid at the precoat layer and wire surface. One high pressure nozzle may remove the precoat layer while another cleans the wire surface, and the nozzles may be reciprocated (with respect to the shaft for rotating the disc filters in a trough). The high pressure jets provide liquid at a pressure of about 30-100 bar, while the low pressure jet pressure is between 2-30 bar and may be utilized continuously, or arrested when the high pressure jets are operable.

Abstract: A method and apparatus to clean a filter drum used for thickening lime mud. The drum is rotated about a horizontal axis in a first direction so that the circumferential surface of the drum moves into contact with lime mud in a vat and a precoat layer formed on the drum, as well as an external layer of lime mud which forms a thickened lime mud cake when a vacuum is applied to the drum withdrawing liquid from the lime mud. The thickened external layer of lime mud cake is scraped from the drum at a second side of the vat, and at a first opposite side of the vat a first jet of liquid is directed onto the drum surface (e.g. at a pressure of about 30-100 bar) to remove a strip of the precoat layer, a third jet of liquid cleans the drum after removal of the precoat layer, and a second jet of liquid is directed onto the drum with sufficient intensity (e.g. a pressure of about 2-20 bar) to remove, by spreading and partially detaching, a strip from the thickened lime mud cake.

Abstract: Disk refiner for cellulose, paper or other equivalent pulp, with two mutually opposed blade disks, at least one of which is rotatable, carrying grinding surfaces facing each other and having within the circumference defined by the grinding surface of one blade disk, in the pulp inlet duct, a sieve plate concentric with the blade disks. Within the sieve plate there is a concentric guide plate so that between the sieve plate and the guide plate there is defined a gap through which the pulp to be refined goes to the grinding surfaces.