Filter for continuous filtration of a suspension under pressure

Patent metadata

Field	Value
Publication number	US-9833732-B2
Application number	US-201414509472-A
Country	US
Kind code	B2
Filing date	Oct 8, 2014
Priority date	Oct 11, 2013
Publication date	Dec 5, 2017
Grant date	Dec 5, 2017

Abstract

The invention relates to a filter for continuous filtration of a suspension under pressure, with a pressure vessel ( 1 ), rotating filter elements ( 2 ) disposed in the pressure vessel ( 1 ), where the filter element ( 2 ) passes through one filter cycle for each rotation, with filter zones in liquid and gaseous phase, also with filtrate channels ( 4′ ) that are connected between the filter elements ( 2 ) and separate filtrate outlets ( 14, 14′, 215 ) for each filter zone, as well as a device to control the individual filtrate zones by means of a control disc ( 44 ), where the control disc ( 44 ) has filtrate outlets ( 114, 115 ) for liquid and gaseous phase. It is primarily characterized in that a venting zone ( 46 ) is provided before the filtrate outlet of the liquid phase, viewed in the direction of the filter cycle. Thus, the compressed air in the filter elements ( 2 ) and filtrate channels ( 4′ ) can be carried off and pressure-relieved in a favorable manner.

First claim

The invention claimed is:

1. In a filter for continuous filtration of a suspension in a pressure vessel pressurized over atmospheric pressure ( 1 ),
including rotating filter elements ( 2 ) disposed in the pressure vessel ( 1 ), and subject to said overpressure,
where a filter element ( 2 ) passes through one filter cycle for each rotation, with filter zones ( 2 ′, 2 ″) in liquid and gaseous phase,
also with filtrate channels ( 4 ′) that are fluidly connected between the filter elements ( 2 ) and separate filtrate outlets ( 14 , 215 ) for each filter zone,
as well as a control head to control the individual filter zones by a control disc, where the control disc has a cake formation zone ( 114 ) and a dewatering zone ( 115 ) operatively associated respectively with the liquid and gaseous phases, whereby for each rotating filter element, filtrate is discharged through the filtrate outlet for the cake formation zone and thereafter filtrate and air are discharged through the filtrate outlet for the dewatering zone, such that during rotation of each filter element a portion of the filter element containing primarily air is operatively disconnected from the dewatering zone and the cake formation zone;
wherein the control disc further includes a snap blow zone ( 45 ) and said snap blow zone ( 45 ) is between the dewatering zone ( 115 ) and the cake formation zone ( 114 ), viewing in the direction of the filter cycle;
the improvement comprising that a venting zone ( 46 ) is provided in the control disc ( 44 ) after the snap blow zone ( 45 ) and before the cake formation zone ( 114 ), viewed in the direction of the filter cycle, and the venting zone ( 46 ) is connected to said portion of the filter element and to a separation tank ( 25 ) via a separate pipe ( 46 ′) to release the primarily air in said portion of the filter element ( 2 ) and connected filtrate channel ( 4 ′) to atmospheric pressure.

2. Filter according to claim 1 , wherein the separate filtrate outlets ( 14 , 215 ) are connected to said separation tank ( 25 ) arranged at a lower elevation than the pressure vessel ( 1 ).

3. Filter according to claim 2 , wherein the separation tank is connected to the filtrate outlets via barometric drop legs ( 114 ′, 115 ′) with a vertical length of 6 to 10 m.

4. Filter according to claim 2 , wherein
one outlet ( 215 ) is fluidly connected to the dewatering zone ( 115 ) of the control disc for collecting dewatering filtrate;
a second outlet ( 14 ″) is fluidly connected to the cake formation zone ( 114 ) of the control disc for collecting cloudy cake filtrate;
a third outlet ( 14 ′) is fluidly connected to the cake formation zone ( 114 ) of the control disc for collecting clear cake filtrate;
barometric drop legs ( 114 ′, 115 ′) fluidly connect the filtrate outlets ( 14 ′, 14 ″, 215 ) to said separation tank ( 25 ).

5. Filter for continuous filtration of a suspension under pressure, comprising:
a pressure vessel ( 1 ) for operation at atmospheric overpressure;
at least one filter element ( 2 ) constituted by a plurality of filter segments, rotatable on a filter shaft ( 4 ) in a filter cycle direction through a liquid suspension region and an air region within the pressure vessel ( 1 ) and subject to said overpressure, where each filter element ( 2 ) passes through one filter cycle for each rotation, first forming an accumulation of solids on the filter element when immersed in the suspension region and with filtrate drawn into the filter element, followed in the air region where filtrate and air pass through the accumulated solids and enter the filter element;
separate filtrate channels ( 4 ′) in the shaft, where filtrate is collected from within the segments of the filter element and delivered to one end of the shaft;
a control head at said one end of the shaft, including a control disc ( 44 ) with a cake formation zone ( 114 ) operatively associated with some filtrate channels ( 4 ′) and associated segments in the suspension region during the rotation and a dewatering zone ( 115 ) operatively associated with other filtrate channels ( 4 ′) and associated segments and the air region during the rotation;

wherein the control disc further includes a snap blow zone ( 45 ) and said snap blow zone ( 45 ) is between the dewatering zone ( 115 ) and the cake formation zone ( 114 ), viewing in the direction of the filter cycle,
filtrate outlets ( 14 , 215 ) for each zone, whereby for each segment of each rotating filter element, filtrate is discharged through the filtrate outlet for the cake formation zone and thereafter filtrate and air are discharged through the filtrate outlet for the dewatering zone, such that during rotation of each filter element a segment of the filter element containing primarily air is operatively disconnected from the dewatering zone and the cake formation zone;
wherein said control disc includes a distinct venting zone ( 46 ) after said snap blow zone ( 45 ), provided before a given filtrate channel ( 4 ′) operatively associated with said segment portion reaches the cake formation zone ( 114 ),viewed in the direction of the filter cycle, with the venting zone ( 46 ) connected to a separation tank ( 25 ) via a separate pipe ( 46 ′) to release said primarily air from the disconnected segment of the filter element ( 2 ) and operatively associated filtrate channel ( 4 ′) to atmospheric pressure without the released air coming into contact with the cake formation zone.

6. Filter according to claim 5 , wherein the filtrate outlets ( 14 , 215 ) are connected to said separation tank ( 25 ) arranged at a lower elevation than the pressure vessel ( 1 ).

7. Filter according to claim 6 , wherein the separation tank is connected to the filtrate outlets via barometric drop legs ( 114 ′, 115 ′) with a vertical length of 6 to 10 m.

8. Filter according to claim 5 , wherein during the rotation of the shaft ( 4 ′) through one cycle, a specific filtrate channel 4 ′ first passes the cake formation zone ( 114 ), then the dewatering zone ( 115 ) and is followed by removal of the accumulated solids on the filter element by the passage of air through said snap blow zone ( 45 ), and just before the start of another cycle, said specific filtrate channel passes the venting zone ( 46 ), viewed in the direction of the filter cycle.

9. Filter according to claim 6 , wherein
one outlet ( 215 ) is fluidly connected to the dewatering zone ( 115 ) of the control disc for collecting dewatering filtrate;
a second outlet ( 14 ″) is fluidly connected to the cake formation zone ( 114 ) of the control disc for collecting cloudy cake filtrate;
a third outlet ( 14 ′) is fluidly connected to the cake formation zone ( 114 ) of the control disc for collecting clear cake filtrate;
barometric drop legs ( 114 ′, 115 ′) fluidly connect the filtrate outlets ( 14 ′, 14 ″, 215 ) to a separation tank ( 25 ) arranged at a lower elevation than the pressure vessel ( 1 ).

Assignees

• Andritz Ag Maschf

Inventors

• Prader Rainer

Classifications

• B01D33/48

  by flushing, e.g. counter-current air-bumps · CPC title

• B01D33/21

  with hollow filtering discs transversely mounted on a hollow rotary shaft · CPC title

• B01D36/001 Primary

  Filters in combination with devices for the removal of gas, air purge systems · CPC title

• B01D33/466

  scrapers · CPC title

• B01D24/32 Primary

  Rotation · CPC title