Device for Thickening a Cryogenic Slurry using Cross-Flow Filtration

1 . A device for thickening a cryogenic slurry comprising:

a cryogenic slurry flow path, a cryogenic liquid discharge path, and a filter medium between the cryogenic slurry flow path and the cryogenic liquid discharge path, wherein the cryogenic slurry, comprising a solid and a cryogenic liquid, is fed into the cryogenic slurry flow path, generally tangential to the filter medium, causing a portion of the cryogenic liquid to cross the filter medium into the cryogenic liquid discharge path as a cryogenic liquid discharge and the cryogenic slurry to thicken to produce a thickened slurry; and,

the filter medium comprising a cryogenically-stable material such that adsorption of gases is inhibited, deposition of solids is prevented, and temperature-change induced expansion and contraction of the filter medium is optimized.

2 . The device of claim 1 , wherein the cryogenically-stable material comprises sintered ceramics, polytetrafluoroethylene, polychlorotrifluoroethylene, natural diamond, man-made diamond, chemical-vapor deposition diamond, polycrystalline diamond, or combinations thereof.

3 . The device of claim 1 , wherein optimization of temperature-change induced expansion and contraction of the filter medium comprises decreasing expansion and contraction of the filter medium to prevent damage to the filter medium or increasing expansion and contraction of the filter medium to cause the filter medium to become self-cleaning.

4 . The device of claim 1 , wherein the filter medium comprises a sparger with openings comprising an effective diameter of at most 25 microns, a hole with a diameter of at most 25 microns, or a combination thereof.

5 . The device of claim 1 , wherein a portion of the cryogenic slurry flow path and a portion of the liquid discharge path are enclosed perpendicular to the cryogenic slurry flow path and the liquid discharge path by the cryogenically-stable material.

6 . The device of claim 5 , wherein the cryogenically-stable material comprises sintered ceramics, polytetrafluoroethylene, polychlorotrifluoroethylene, natural diamond, man-made diamond, chemical-vapor deposition diamond, polycrystalline diamond, or combinations thereof.

7 . The device of claim 1 , wherein the solid comprises carbon dioxide, nitrogen oxide, sulfur dioxide, nitrogen dioxide, sulfur trioxide, hydrogen sulfide, hydrogen cyanide, water, hydrocarbons with a freezing point above the temperature of the cryogenic liquid, or combinations thereof.

8 . The device of claim 1 , wherein the cryogenic liquid comprises any compound or mixture of compounds with a freezing point below the temperature at which the solid melts.

9 . The device of claim 1 , wherein the cryogenic slurry flow path is provided with a back pressure by a restricted outlet for the thickened slurry.

10 . The device of claim 1 , further comprising:

a double-walled pipe comprising an inner pipe and an outer pipe separated by a liquid plenum;

a space inside the inner pipe defining the cryogenic slurry flow path;

the inner pipe comprising cylindrical side walls forming the filter medium, being perforated by at least one hole with a diameter of less than 25 microns;

the liquid plenum between the outer pipe and the inner pipe defining the cryogenic liquid discharge path;

the cryogenic slurry is provided to the cryogenic slurry flow path and thickened to produce the thickened slurry and the cryogenic liquid discharge;

the cryogenic liquid discharge is removed through the cylindrical side walls and passes through the liquid plenum; and,

the thickened slurry is removed through an outlet of the inner pipe.

11 . The device of claim 10 , wherein the double-walled pipe defines a generally spiral flow pattern.

12 . The device of claim 10 , wherein the double-walled pipe defines a u-tube bundle pattern.

13 . The device of claim 1 , wherein:

the device comprises a head plate, a slurry plate, an end plate, and the filter medium, the filter medium further comprising a first filter plate and a second filter plate;

the first filter plate is secured between the head plate and a first face of the slurry plate;

the second filter plate is secured between a second face of the slurry plate and the end plate;

the cryogenic slurry flow path passes through the head plate and the slurry plate into the end plate, connecting to a thickened slurry flow path in the end plate;

the thickened slurry flow path leaves the end plate and passes through the slurry plate and the head plate;

the cryogenic liquid discharge path begins in the end plate in an end plate liquid removal chamber and passes through the slurry plate and the head plate, with additional cryogenic liquid provided to the liquid discharge path in the head plate by a head plate liquid removal chamber;

the cryogenic slurry flow path in the slurry plate comprises generally spiraling paths on the first face of the slurry plate and the second face of the slurry plate, wherein the cryogenic slurry flow path is shaped generally like a half-pipe, with an open face of the half-pipe facing the first filter plate and the second filter plate;

the head plate comprises a raised lip to insert the first filter plate such that an open space is provided between the first filter plate and the head plate, the open space defining the head plate liquid removal chamber;

the end plate comprises a raised lip to insert the second filter plate such that an open space is provided between the second filter plate and the end plate, the open space defining the end plate liquid removal chamber;

the slurry plate comprises a central portion with the generally spiraling paths, the central portion rimmed with a narrower outside portion;

the head plate and the end plate are shaped in a manner that they will fit over the central portion of the slurry plate, causing the combination of the head plate, the slurry plate, the end plate, the first filter plate, and the second filter plate to form a right rectangular prism; and,

the cryogenic slurry passes through the central portion of the slurry plate generally tangential to the first filter plate and the second filter plate, causing the cryogenic liquid to pass into the head plate liquid removal chamber and the end plate liquid removal chamber and the thickened cryogenic slurry to pass through the thickened slurry flow path.

14 . The device of claim 13 , wherein the half-pipe of the slurry plate comprises a diameter that varies to provide consistent pressure.

15 . The device of claim 13 , wherein the cryogenically-stable material inhibits adsorption of gases, prevents deposition of solids, or a combination thereof, the cryogenically-stable material comprising sintered ceramics, polytetrafluoroethylene, polychlorotrifluoroethylene, natural diamond, man-made diamond, chemical-vapor deposition diamond, polycrystalline diamond, or combinations thereof.

16 . The device of claim 1 , wherein:

the device comprises a head plate, an even number of slurry plates, one fewer liquid removal plates than the total number of slurry plates, an end plate, and the filter medium, the filter medium comprising a filter plate for each face of each slurry plate, the filter plate for the head plate being a first filter plate, the filter plate for the end plate being a last filter plate, and the filter plates for use between the slurry plates and the liquid removal plates being middle filter plates;

the first filter plate is secured between the head plate and a first face of a first slurry plate;

the last filter plate is secured between the end plate and a second face of a last slurry plate;

the middle filter plates are secured between the liquid removal plates and the slurry plates;

the cryogenic slurry flow path passes through the head plate, the slurry plates, and the liquid removal plates into the end plate, connecting to a thickened slurry flow path in the end plate;

the thickened slurry flow path leaves the end plate and passes through the slurry plates, the liquid removal plates, and the head plate;

the cryogenic liquid discharge path begins in the end plate in an end plate liquid removal chamber and passes through the slurry plates, the liquid removal plates, and the head plate, with additional cryogenic liquid provided to the liquid discharge path from the liquid removal plates by two liquid removal chambers for each of the liquid removal plates, and from the head plate by a head plate liquid removal chamber;

the cryogenic slurry flow path in the slurry plates comprises generally spiraling paths on the first face of the slurry plates and the second face of the slurry plates, wherein the cryogenic slurry flow path is shaped generally like a half-pipe, with the open face of the half-pipe facing the filter plates;

the head plate comprises a raised lip to insert the first filter plate such that an open space is provided between the first filter plate and the head plate, the open space defining the head plate liquid removal chamber;

the end plate comprises a raised lip to insert the last filter plate such that an open space is provided between the last filter plate and the end plate, the open space defining the end plate liquid removal chamber;

the liquid removal plates comprise a first face and a second face, each with a raised lip to insert the middle filter plates such that an open space is provided between the middle filter plates and the liquid removal plates, the open spaces comprising the middle liquid removal chambers;

the slurry plates comprise a central portion with the generally spiraling paths, the central portion rimmed with a narrower outside portion;

the head plate, the end plate, and the liquid removal plates shaped in a manner that they will fit over the central portion of the slurry plates, causing the combination of the head plate, the slurry plates, the liquid removal plates, the end plate, and the filter plates to form a right rectangular prism; and,

the cryogenic slurry passes through the central portion of the slurry plates generally tangential to the filter plates, causing the cryogenic liquid to pass into the head plate liquid removal chamber, the end plate liquid removal chamber, and the middle liquid removal chambers, and the thickened cryogenic slurry to pass through the thickened slurry flow path.

17 . The device of claim 16 , wherein the half-pipe of the slurry plates comprises a diameter that varies to provide consistent pressure.

18 . The device of claim 16 , wherein the cryogenically-stable material inhibits adsorption of gases, prevents deposition of solids, or a combination thereof, the cryogenically-stable material comprising sintered ceramics, polytetrafluoroethylene, polychlorotrifluoroethylene, natural diamond, man-made diamond, chemical-vapor deposition diamond, polycrystalline diamond, or combinations thereof.

19 . The device of claim 1 , further comprising a head plate, a slurry plate, an end plate, and the filter medium, the filter medium further comprising a first filter plate and a second filter plate, wherein the head plate, the slurry plate, and the end plate define the cryogenic liquid discharge path and the cryogenic slurry flow path.

20 . The device of claim 1 , further comprising a head plate, an even number of slurry plates, one fewer liquid removal plates than the total number of slurry plates, an end plate, and the filter medium, the filter medium comprising a filter plate for each face of each slurry plate, wherein the head plate, the slurry plates, the liquid removal plates, and the end plate define the cryogenic liquid discharge path and the cryogenic slurry flow path.