Descending bed, continuously regenerating type filter with an adjustable length wash chamber

A liquid filtering method comprising the steps of:

• passing liquid to be filtered through a bed of particulate or granular filtering medium having lower and upper parts, thereby accumulating filtered liquid above said upper part of said bed provided in a vessel,
• transferring dirty filter medium from said lower part of said bed to a filter-medium washer, said filter-medium washer being provided with two radially spaced apart walls having a vertical extension and defining a wash chamber therebetween,
• passing said dirty filter medium through said wash chamber in one direction toward said upper zone,
• passing said filtered liquid through said wash chamber in a direction opposite to said one direction, thereby obtaining washed filter medium,
• transferring said washed filter medium from said filter-medium washer to said upper part of the bed;
• and
• adjusting said vertical extension of said walls of said wash chamber in response to prevailing operating conditions.

A liquid filtering method comprising the steps of:

• (a) providing filter medium selected from the group consisting of granular and particulate medium to form a filter bed in an elongated vessel which extends along a longitudinal axis, said filter bed having upper and lower axial zones,
• (b) passing washing liquid to be filtered through said filter bed, thereby obtaining a filtered washing liquid above said upper axial zone of said filter bed;
• (c) continuously displacing dirty filter medium from said lower zone through a washing chamber in one direction, said washing chamber being defined between two radially spaced apart walls;
• (d) simultaneously with step (c) continuously displacing said filtered washing liquid through said washing chamber along said filter-medium path in a direction opposite to said one direction, thereby obtaining washed filtering medium delivered to said upper zone of said filter bed;
• and
• (e) adjusting a length of said walls in response to prevailing operating conditions.