Pressure-filtering apparatus and filtering method

Claim 2

An apparatus as defined in claim 1, wherein said inner and outer filter drum are coaxially journalled; the feed connection includes a feed chamber communicating with the filter chamber, the feed chamber being axially sealed off by means of rotary seals; the discharge connection including a discharge chamber also communicating with the filter chamber and similarly sealed off by means of rotary seals; and the moving means being constituted by drive means arranged to rotate the filter drums relative to one another.

Claim 3

An apparatus as defined in claim 3, wherein the inner filter drum includes flanges attached to the drum ends and inner drum shafts coaxially extending from each flange, at least one of these shafts being Hollow to permit discharge of the liquor collecting inside the inner filter drum, both inner drum shafts being journalled at an axial distance from their respective flanges, and one inner drum shaft end being connected to the drive means; the outer one of the two filter drums includes likewise flanges attached to the drum ends, said first and second outer drum shafts coaxially extending from each flange, the outer drum shafts being shorter than the inner drum shafts, both outer drum shafts being journalled near their respective flanges so as to leave an axial space between them and the inner shaft journals on each side of the drums, these axial spaces being part of the feed chamber and discharge chamber, respectively; the shafts and flanges of the drums being radially spaced from one another to form a continuous annular axial channel for the flow of material into and out of the filter chamber, respectively, as part of the feed and discharge connections; one outer drum shaft being connected to the drive means.

Claim 4

An apparatus as defined in claim 4, wherein the journals for the inner and outer drum shafts are contained in stationary journal housings on each side of the drums, one of the two journal housings enclosing the feed chamber between the journals and a stationary feed pipe opening into the feed chamber, the other journal housing enclosing a similar discharge chamber and stationary discharge pipe.

Claim 5

An apparatus as defined in claim 3, further comprising a gas-tight stationary casing surrounding the filter drums and carrying the drum journals; a gas-tight liquor-collecting receptacle connected to the casing so as to communicate with the outer liquor-discharge area surrounding the outer drum as well as with the inner liquor-discharge area inside the inner drum; and a liquor-discharge conduit to continuously remove the accumulated liquor.

Claim 6

An apparatus as defined in claim 6, wherein the axis of the each filter drum is vertical; the casing includes a bottom panel which carries a journal housing with the lower drum journals and the feed chamber arranged in the journal housing; the casing further includes an upper closure panel which carries a similar journal housing with the upper drum journals and the discharge chamber arranged therein; the liquor-collecting receptacle is mounted underneath the bottom panel of the casing so as to surround the lower journal housing, the liquor discharging from the outer filter drum passing through apertures in the bottom panel into the receptacle, while the liquor discharging from the inner filter drum passes via a sealed axial passageway from the inside of the drum across the lower journal housing into the same receptacle.

Claim 7

An apparatus as defined in claim 3, wherein the common length of the concentric filter drums is subdivided into at least one filtering zone and one wash zone of predetermined lengths, the wash zone being formed by two axially spaced transverse separation walls sealingly arranged in the cavity of the inner drum; the apparatus further includes means for supplying highly pressurized washing liquid to the wash zone, so as to force the washing liquid through the perforated wall of the inner filter drum into the pressurized product flowing through the filter chamber.

Claim 8

An apparatus as defined in claim 8, wherein the common length of the concentric filter drums includes two filtering zones and an intermediate wash zone; the length and longitudinal location of the wash zone being adjustable through axial repositioning of the transverse separation walls; the interior liquor discharge areas of the inner filter drum in the filtering zone being connected to one another by means of a sealed duct extending across the wash zone.

Claim 9

An apparatus as defined in claim 8, wherein the common length of the concentric filter drums includes several filtering zones and several wash zones in longitudinal alternation.

Claim 10

An apparatus as defined in Claim 8, wherein the washing liquid supply means includes a supply pipe sealingly extending from the outside of the drums into the washing zone along the drum axis.

Claim 11

An apparatus as defined in claim 8, wherein the wall of the inner filter drum has an inner diameter which increases in a taper from the longitudinal midpoint of the drum to both drum ends; and the transverse separation walls forming the wash zone are axially positioned by clamping them against oppositely tapering drum wall portions.

Claim 13

A filtering method as defined in claim 13, further comprising the step of continuously feeding a pressurized suspension into the filter chamber on one of its extremities; and continuously discharging the dried product cake from the filter chamber on its opposite extremity.

Claim 14

A filtering method as defined in claim 14, further comprising the step of continuously washing the product during filtering by forcibly injecting washing liquid into a portion of the filtering chamber.

Claim 15

A filtering method as defined in claim 14, further comprising the step of recirculating at least a portion of the continuously discharged product cake into the filter chamber; and washing the product cake to be recirculated before it is re-introduced into the filter chamber.

Claim 16

A pressure-filtering apparatus for the separation of a suspension into dried solid product and liquor in a continuous operation, the apparatus comprising: a. a filter chamber defined by perforated walls in an inner and outer filter drum, said drums being concentrically arranged; b. a feed connection and a discharge connection communicating with said filter chamber; c. a liquor outlet means in the apparatus; d. a first drive means coupled with said inner drum for rotating said inner drum in one direction; e. a second drive means coupled with said outer drum for rotating said outer drum in a direction opposite to the direction of rotation of said inner drum; thereby creating turbulence and a mixing action in the suspension, while the liquor is being filtered out under pressure.