Process and apparatus for separating valuable or harmful liquids from slurries

Abstract

This invention relates generally to a filtration process and apparatus for separating valuable or harmful process liquids from mixtures or slurries that contain such liquids and solid particles. In particular, the invention relates to a filtration process for separating Process Liquid from a feed slurry that comprises a mixture of the Process Liquid and solid particles, the process employing a Sweep Liquid that is less dense than the Process Liquid.

1 - 25 . (canceled) 
     
     
         26 . A filtration process for separating Process Liquid from a feed slurry that predominantly comprises a mixture of the Process Liquid and solid particles, the process including the steps of:
 (a) introducing the feed slurry into an Inlet Chamber of a reservoir, said reservoir including i) a substantially horizontal Filter Medium that allows filtrate to flow through the Filter Medium while blocking the passage of most or all of the solid particles in the feed slurry through the Filter Medium, ii) a slurry agitation means configured to cause fluid to flow from a central suction zone radially outward and across at least a portion of the upstream surface of the Filter Medium and thereby prevent an excessive accumulation of solid particles on the upstream surface of the Filter Medium iii) a Housing which at least partially encloses the upstream surface of the Filter Medium and at least a portion of the feed slurry that is in close proximity to the upstream surface of the Filter Medium, said Housing having at least one large inlet opening that allows slurry to enter freely from the Inlet Chamber and flow into the central suction zone and then be moved radially outward and across at least a portion of the upstream surface of the Filter Medium, and iv) one or more mechanical components configured to prevent overmixing of Sweep Liquid and Process Liquid,   wherein said introduced feed slurry fills the central suction zone and is in contact with the upstream surface of the Filter Medium, and;   (b) introducing into the Inlet Chamber of the reservoir a Sweep Liquid that is less dense than and at least partially miscible with the Process Liquid to create within the Inlet Chamber a lower liquid layer in contact with the upstream surface of the Filter Medium and predominantly comprising Process Liquid, and an upper liquid layer predominantly comprising Sweep Liquid and an Interface Zone between the two liquid layers, and;   (c) operating the slurry agitation means to cause at least a portion of the slurry in close proximity to the Filter Medium to flow from the central suction zone radially outwards and across a portion of the upstream surface of the Filter Medium, said slurry motion being sufficient to prevent the excessive accumulation of solid particles on the upstream surface of the Filter Medium, and;   (d) allowing a recirculating portion of the slurry that flows radially outward from the central suction zone and across at least a portion of the upstream surface of the Filter Medium as a result of applying the slurry agitation means step (c) to flow back into the central suction zone, and;   (e) applying a pressure differential across the Filter Medium, wherein said pressure differential causes liquid to flow through the Filter Medium as filtrate, and;   (f) applying one or more mechanical means of avoiding unwanted currents in the Inlet Chamber that could otherwise disturb the liquids in or close to the Interface Zone and thereby cause overmixing of Process Liquid with Sweep Liquid, and;   (g) allowing the flow of liquid filtrate through the Filter Medium in accordance with steps (c), (d), (e), and (f) to continue until at least a portion of the Process Liquid has been displaced out of the feed slurry through the Filter Medium thereby forming a depleted slurry above the Filter Medium that comprises solid particles and Sweep Liquid and is depleted of Process Liquid, and;   (h) recovering at least a portion of the filtrate from the reservoir.   
     
     
         27 . The process as claimed in  claim 26  wherein the flow of a recirculating portion of slurry that results from applying step (d) is restricted to cause an increase in fluid pressure over the upstream surface of the Filter Medium, thereby assisting filtrate to flow through the Filter Medium 
     
     
         28 . The process as claimed in  claim 26  wherein the process further includes the step of adding a dispersing agent to the feed slurry. 
     
     
         29 . The process as claimed in  claim 28  wherein the Process Liquid and the Sweep Liquid are at least partially miscible with water. 
     
     
         30 . The process as claimed in  claim 28  wherein the Process Liquid comprises one or more non-polar liquids selected from the group consisting of: crude hydrocarbon liquids; hydrocarbon fuels; other refined hydrocarbon liquids; organic polymers; organic coolants and cutting fluids used in metal cutting and metal forming; organic solvents used in metal extraction and refining; synthetic oil; organic liquors used in crystallisation processes; organic fluids used in the oil and gas industry when drilling wells; liquids contained in slurries removed from equipment and piping during descaling or cleaning operations; non-aqueous automotive and aircraft fluids; non-aqueous heat transfer fluids and hydraulic fluids; lubricating oils; organic liquids used during the manufacture of cosmetics, pharmaceuticals, plastics, petrochemicals, pulp and paper products and electronics; toxic industrial liquid effluent components that are substantially non-miscible with water; and combinations thereof. 
     
     
         31 . The process as claimed in  claim 30  wherein the Sweep Liquid comprises a liquid selected from the group consisting of: naphtha; natural gas liquids; pentane; hexane; heptane; white spirit; mineral turpentine; diesel; gasoline; other light hydrocarbon liquids; organic solvents; and a mixture thereof. 
     
     
         32 . The process as claimed in  claim 31  wherein the process further includes after step (g) the additional step of applying a depleted slurry treatment method that separates at least a portion of the Sweep Liquid from the depleted slurry. 
     
     
         33 . The process as claimed in  claim 32  wherein the depleted slurry treatment method includes at least one step selected from the group consisting of: filtering the depleted slurry so as to reduce its liquid content, and; vaporising at least a portion of the Sweep Liquid in the depleted slurry, and; introducing water into the reservoir underneath the depleted slurry in sufficient quantity so that the level of introduced water rises through at least a portion of the depleted slurry so as to separate by flotation at least a portion of the Sweep Liquid from the depleted slurry, and; removing at least a portion of the depleted slurry from the reservoir and placing water and said removed depleted slurry into a second reservoir to create an aqueous lower layer of liquid that predominantly comprises water wherein at least a portion of the solid particles that had been contained in the removed depleted slurry are allowed to accumulate by gravity settling and to create an upper layer of liquid that predominantly comprises Sweep Liquid that floats on the aqueous lower layer. 
     
     
         34 . The process as claimed in  claim 26  wherein the slurry agitation means is a means selected from the group consisting of: the rotation of an Impeller in a plane that is substantially parallel to and proximate the upstream surface of the Filter Medium, and; the rotation of the Filter Medium about a substantially vertical axis of rotation. 
     
     
         35 . A filtration process for recovering Process Liquid that is at least partially miscible with water from a feed slurry that predominantly comprises a mixture of the Process Liquid and solid particles, the process including the steps of:
 (a) introducing the feed slurry into a reservoir above a substantially horizontal Filter Medium therein and wherein the Filter Medium allows liquids to flow through it while blocking the passage of most or all of the solid particles in the feed slurry through the Filter Medium, and;   (b) introducing into the reservoir above the Filter Medium a Sweep Liquid that is less dense than and not miscible with water, and less dense than and non-miscible with the Process Liquid to create a lower layer of liquid that is in contact with the upstream surface of the Filter Medium and predominantly comprises Process Liquid and an upper layer of liquid that predominantly comprises Sweep Liquid and an interface between the two liquid layers, and;   (c) applying a pressure differential across the Filter Medium, wherein said pressure differential causes liquid to flow through the Filter Medium as filtrate, and;   (d) preventing an excessive accumulation of solid particles on the upstream surface of the Filter Medium by agitating at least a portion of the slurry that is in close proximity to the Filter Medium and;   (e) allowing the flow of liquid through the Filter Medium in step (c) and the prevention of excessive accumulation of solid particles onto the surface of the Filter Medium in step (d) to continue until at least a portion of the Process Liquid has been displaced out of the slurry through the Filter Medium thereby forming a depleted slurry above the Filter Medium that comprises solid particles and Sweep Liquid and is depleted of Process Liquid, and;   (f) recovering at least a portion of the filtrate from the reservoir.   
     
     
         36 . The process as claimed in  claim 35  wherein the Sweep Liquid includes a liquid selected from the group consisting of: naphtha; natural gas liquids;
 pentane; hexane; heptane; white spirit; mineral turpentine; diesel; gasoline; other light hydrocarbon liquids; organic solvents; and a mixture thereof. 
 
     
     
         37 . The process as claimed in  claim 35  wherein the process further includes after step (e) the additional step of applying a depleted slurry treatment method that separates at least a portion of the Sweep Liquid from the depleted slurry. 
     
     
         38 . The process as claimed in  claim 37  wherein the depleted slurry treatment method includes at least one step selected from the group consisting of: filtering the depleted slurry so as to reduce its liquid content, and; vaporising at least a portion of the Sweep Liquid in the depleted slurry, and; introducing water into the reservoir underneath the depleted slurry in sufficient quantity so that the level of introduced water rises through at least a portion of the depleted slurry so as to separate by flotation at least a portion of the Sweep Liquid from the depleted slurry, and; removing at least a portion of the depleted slurry from the reservoir and placing water and said removed depleted slurry into a second reservoir to create an aqueous lower layer of liquid that predominantly comprises water wherein at least a portion of the solid particles that had been contained in the removed depleted slurry are allowed to accumulate by gravity settling and to create an upper layer of liquid that predominantly comprises Sweep Liquid that floats on the aqueous lower layer. 
     
     
         39 . The process as claimed in  claim 35  wherein the process further includes the step of adding a dispersing agent to the feed slurry. 
     
     
         40 . The process as claimed in  claim 35  wherein the slurry is agitated in step (d) by moving the Filter Medium back and forth horizontally, or by rotating the Filter Medium about a vertical axis of rotation, or by moving an agitator in a plane that is parallel to and in close proximity to the upstream surface of the Filter Medium. 
     
     
         41 . An apparatus for performing a filtration process for separating Process Liquid from a feed slurry that predominantly comprises a mixture of the Process Liquid and solid particles; the apparatus comprising:
 a reservoir including a substantially horizontal Filter Medium that is configured to allow filtrate to flow through it while blocking the passage of most or all of the solid particles in the feed slurry through the Filter Medium and an Inlet Chamber within the reservoir which is configured to hold liquids and slurries on an upstream side of the Filter Medium, and;   one or more inlets configured to introduce slurry and liquid into the reservoir by which the feed slurry and a Sweep Liquid that is less dense than and at least partially miscible with the Process Liquid can be introduced into the Inlet Chamber to create within the Inlet Chamber an upper liquid layer predominantly comprising Sweep Liquid above a lower liquid layer predominantly comprising of Process Liquid and an Interface Zone between the two liquid layers, and;   a slurry agitation means configured to cause at least a portion of the slurry in the Inlet Chamber to flow radially outwards and across at least a portion of the upstream surface of the Filter Medium, said slurry motion being sufficient to prevent the excessive accumulation of solid particles on the upstream surface of the Filter Medium, and;   a Housing within the reservoir configured to enclose at least a portion of the slurry that is in close proximity to the upstream surface of the Filter Medium, said Housing having at least one large inlet opening that allows slurry to enter freely from the Inlet Chamber and flow into the central suction zone and then be moved radially outward and across at least a portion of the upstream surface of the Filter Medium, and   a recirculation means within the reservoir configured to allow a recirculating portion of the slurry that flows radially outward and across at least a portion of the upstream surface of the Filter Medium as a result of the operation of the agitation means to flow out of the Housing and back into the central suction zone, and;   a slurry flow restriction means configured to restrict the flow of the recirculating portion of slurry out of the Housing resulting from the operation of the agitation means and the recirculation means so as to cause the fluid pressure over the upstream surface of the Filter Medium to rise and to thereby assist filtrate to flow through the Filter Medium, and;   one or more mechanical components configured to avoid unwanted currents in the liquid in the Inlet Chamber that could otherwise disturb the liquids in or close to the Interface Zone and thereby cause overmixing of Process Liquid with Sweep Liquid, and;   a first outlet configured to allow filtrate to flow out of the reservoir, and;   a second outlet configured to allow slurry to flow out of the reservoir.   
     
     
         42 . The apparatus as claimed in  claim 41  wherein the one or more mechanical components configured to avoid unwanted currents in the liquid in the Inlet Chamber include at least one component selected from the group consisting of: conical or sloped surfaces above the Filter Medium configured to direct a substantial portion of the liquid that is moving downwards towards the Filter Medium to preferentially flow towards the central suction zone;
 substantially horizontal plates configured to block excessive upward movement of the flow of the recirculating portion of slurry created by operation of the slurry agitation means and recirculation means; plates, baffles, perforated screens, a loose layer of beads or stones or other solid matter the means being placed above at least a portion of the Filter Medium and configured to block, deflect, dissipate or dampen upwardly moving currents. 
 
     
     
         43 . The apparatus as claimed in  claim 41  wherein the slurry agitation means is selected from the group consisting of
 a Filter Medium that is rotatable, and 
 installing a rotatable Impeller inside the Inlet Chamber above a fixed Filter Medium, 
 and wherein the rotatable Impeller or the rotatable Filter Medium, whichever is present, is configured to be rotated at a speed to cause at least a portion of the slurry in the Inlet Chamber to flow radially outwards and across at least a portion of the upstream surface of the Filter Medium, said slurry motion being sufficient to prevent the excessive accumulation of solid particles on the upstream surface of the Filter Medium.