Vacuum filtration system and method of filtering pulp fibers from pulp slurry using the same

A cylindrical structure having an interior volume and a longitudinal axis and being supportable within a vessel, for rotation about said longitudinal axis in a predetermined rotational direction, said vessel containing a selected level of liquid suspension having solids dispersed in liquid filtrate, said cylinder structure comprising:

• elements including,
• a filter surface pervious to said filtrate and substantially impervious to said dispersed solids;
• a filtrate outlet tube disposed along said longitudinal axis;
• and
• a plurality of filtrate conduits, each said filtrate conduit having first and second conduit portions, each said first conduit portion having a filtrate inlet port extending beneath and along a portion of said filter surface in a direction substantially parallel to said longitudinal axis, and each said second conduit portion being operably connected with one said first conduit portion and having a filtrate outlet port operably connected to said filtrate outlet tube, and said filtrate outlet port of each said filtrate conduit being radially offset from said associated filtrate inlet port in said predetermined rotational direction so that, as said cylinder structure rotates in said predetermined rotational direction and a vacuum source is operably connected to said filtrate outlet tube, filtrate from said vessel is suctioned through said filter surface and along at least a selected number of said filtrate conduits and thence through said filtrate outlet port, and dispersed solids are suctioned against said filter surface to form a sheet of said dispersed solids on said filter surface;
• said elements being sized, spaced and dimensioned, such that, as said cylinder structure rotates, each said filtrate conduit below said selected level within said vacuum activation region fills with filtrate, and said filtrate is subjected to hydraulic pressure which cooperates with the vacuum pressure supplied to said filtrate conduits so as to induce the flow of filtrate into said filtrate conduits;
• and
• each said filtrate conduit emerging above said selected level is filled with filtrate, and said filtrate is subjected to hydrostatic pressure which cooperates with the vacuum pressure supplied to said emerged filtrate conduits so as to induce the flow of filtrate into said filtrate conduits.

A method of filtering pulp fibers from a liquid filtrate contained in pulp slurry, said method comprising the steps:

• (a) installing a stationary vacuum tube along a reference axis;
• (b) connecting an activatable vacuum source to said stationary vacuum tube;
• (c) supporting a cylindrical structure within at least a portion of a vessel, for rotation in predetermined rotational direction about said reference axis, said cylinder structure having an interior volume and elements including:
• (i) a filter surface pervious to said filtrate and substantially impervious to said pulp fibers,
• (ii) a filtrate outlet tube disposed along said longitudinal axis, and
• (iii) a plurality of filtrate conduits, each said filtrate conduit having first and second conduit portions, each said first conduit portion having a filtrate inlet port extending beneath and along a portion of said filter surface in a direction substantially parallel to said longitudinal axis, and each said second conduit portion being operably connected with one said first conduit portion and having a filtrate outlet port operably connected to said filtrate outlet tube, and said filtrate outlet port of each said filtrate conduit being radially offset from said associated filtrate inlet port in said predetermined rotational direction;
• (d) maintaining a desired volume of pulp slurry in said vessel so that said pulp slurry fills said vessel up to a selected level;
• and
• (e) activating said vacuum source and rotating said cylindrical structure about said reference axis in said predetermined rotational direction, whereby filtrate from said vessel is suctioned through said filter surface and along at least a selected number of said filtrate conduits and thence through said vacuum outlet port, and pulp fibers are suctioned against said filter surface to form a sheet of said dispersed solids on said filter surface;
• sizing, spacing and dimensioning said elements such that, as said cylindrical structure rotates each said filtrate conduit below said selected level within said vacuum activation region fills with filtrate, and said filtrate is subjected to hydraulic pressure which cooperates with the vacuum pressure supplied to said filtrate conduits so as to induce the flow of filtrate from said vessel into said filtrate conduits;
• and
• each said filtrate conduit emerging above said selected level is filled with filtrate, and said filtrate is subjected to hydrostatic pressure which cooperates with the vacuum pressure supplied to said emerged filtrate conduits so as to induce the flow of filtrate from said vessel into said filtrate conduits.