Subsea Seawater Filtration Apparatus

Abstract

A filtration apparatus includes a tubular casing having a longitudinal axis and first and second casing ends. A plurality of partition plates are positioned in the casing and sealed thereto to thereby define an intake collection chamber between a first of the partition plates and the first casing end, a discharge collection chamber between a second of the partition plates and the second casing end, and a reject collection chamber opposite the second partition plate from the second casing end. A plurality of elongated filtration membrane stacks are positioned side-by-side in the casing generally parallel to the longitudinal axis. Each filtration membrane stack includes an intake end which is fluidly connected to the intake collection chamber, a discharge end which is fluidly connected to the reject collection chamber, and a permeate channel which extends between the first and second ends and is fluidly connected to the discharge collection chamber.

1 : A filtration apparatus which comprises:
 a tubular casing which includes a longitudinal axis and first and second casing ends;   a plurality of partition plates which are positioned in the casing and are sealed thereto to thereby define an intake collection chamber between a first of said partition plates and the first casing end, a discharge collection chamber between a second of said partition plates and the second casing end, and a reject collection chamber opposite the second partition plate from the second casing end;   a plurality of elongated filtration membrane stacks which are positioned side-by-side in the casing generally parallel to the longitudinal axis, each filtration membrane stack comprising an intake end which is fluidly connected to the intake collection chamber, a discharge end which is fluidly connected to the reject collection chamber, and a permeate channel which extends between the intake and discharge ends and is fluidly connected to the discharge collection chamber, wherein an end of the permeate channel located adjacent the intake end is sealed from the intake collection chamber;   an intake pipe which comprises a first end that is fluidly connected to the intake collection chamber and a second end that is fluidly connected to a first connector which is located proximate the second casing end;   a discharge pipe which comprises a first end that is fluidly connected to the discharge collection chamber and a second end that is fluidly connected to a second connector which is located proximate the first connector; and   a reject pipe which comprises a first end that is fluidly connected to the reject collection chamber and a second end that is fluidly connected to a third connector which is located proximate the first and second connectors;   wherein a fluid to be filtered is communicated to the intake collection chamber through the intake pipe and is separated by the filtration membrane stacks into a permeate which is discharged from the discharge collection chamber through the discharge pipe and a reject fluid which is discharged from the reject collection chamber through the reject pipe.   
     
     
         2 : The filtration apparatus of  claim 1 , wherein in use the casing is oriented generally vertically with the first casing end located above the second casing end. 
     
     
         3 : The filtration apparatus of  claim 2 , wherein the intake pipe extends axially through the casing from the second casing end to the intake collection chamber. 
     
     
         4 : The filtration module of  claim 3 , wherein the reject pipe extends axially through the casing from the second casing end to the reject collection chamber. 
     
     
         5 : The filtration apparatus of  claim 1 , wherein the first, second and third connectors comprise part of a single multibore subsea connector hub. 
     
     
         6 : The filtration apparatus of  claim 1 , wherein each filtration membrane stack is sealed in a corresponding hole in the first partition plate. 
     
     
         7 : The filtration apparatus of  claim 6 , wherein each filtration membrane stack comprises a plurality of filtration membranes, each of which is sealed to a corresponding hole in a corresponding partition plate. 
     
     
         8 : The filtration apparatus of  claim 7 , wherein each filtration membrane comprises an inlet end and an outlet end, and wherein the outlet end is spaced apart from an adjacent partition plate located closer to the second casing end. 
     
     
         9 : The filtration apparatus of  claim 8 , wherein each filtration membrane is sealed to the corresponding hole proximate the inlet end. 
     
     
         10 : The filtration apparatus of  claim 8 , wherein each filtration membrane comprises a permeate passage which extends axially between the inlet and outlet ends, and wherein the permeate passages of the filtration membranes in each filtration membrane stack are fluidly connected together to thereby form the permeate channel for that filtration membrane stack. 
     
     
         11 : The filtration apparatus of  claim 10 , further comprising a plurality of connector tubes, each of which extends between a corresponding permeate channel and the discharge collection chamber. 
     
     
         12 : A filtration apparatus which comprises:
 a tubular casing which includes a longitudinal axis and first and second casing ends;   a plurality of partition plates which are positioned in the casing and are sealed thereto to thereby define an intake collection chamber between a first of said partition plates and the first casing end, a discharge collection chamber between a second of said partition plates and the second casing end, and a reject collection chamber opposite the second partition plate from the second casing end;   a plurality of elongated filtration membrane stacks which are positioned side-by-side in the casing generally parallel to the longitudinal axis, each filtration membrane stack comprising an intake end which is fluidly connected to the intake collection chamber, a discharge end which is fluidly connected to the reject collection chamber, and a permeate channel which extends between the first and second ends and is fluidly connected to the discharge collection chamber;   an intake pipe which is connected to the intake collection chamber;   a discharge pipe which is connected to the discharge collection chamber; and   a reject pipe which is connected to the reject collection chamber;   wherein a fluid to be filtered is communicated to the intake collection chamber through the intake pipe and is separated by the filtration membrane stacks into a permeate which is discharged from the discharge collection chamber through the discharge pipe and a reject fluid which is discharged from the reject collection chamber through the reject pipe; and   wherein each filtration membrane stack is comprised of a plurality of filtration membranes which are each sealed to a corresponding hole in a corresponding partition plate, each filtration membrane comprising an inlet end and an outlet end and being sealed to the corresponding hole between the inlet and outlet ends, and the outlet end being spaced apart from an adjacent partition plate located closer to the second casing end.   
     
     
         13 : The filtration apparatus of  claim 12 , wherein in use the casing is oriented generally vertically with the first casing end located above the second casing end. 
     
     
         14 : The filtration apparatus of  claim 13 , wherein the intake pipe extends axially through the casing from the second casing end to the intake collection chamber. 
     
     
         15 : The filtration module of  claim 14 , wherein the reject pipe extends axially through the casing from the second casing end to the reject collection chamber. 
     
     
         16 : The filtration apparatus of  claim 13 , wherein the intake pipe, the reject pipe and the discharge pipe are connected to a multibore subsea connector hub. 
     
     
         17 : A filtration apparatus which comprises:
 a tubular casing which includes a longitudinal axis and first and second casing ends; and   a number of filtration membranes which are positioned in the casing generally parallel with the longitudinal axis;   wherein each filtration membrane includes an active top layer and a coating which renders the active top layer hydrophilic.   
     
     
         18 : The filtration apparatus of  claim 17 , wherein the coating is comprised of a combination of a hydrophilic polymer and a surfactant. 
     
     
         19 : The filtration apparatus of  claim 18 , wherein a negatively charged material is applied to the coating. 
     
     
         20 : The filtration membrane of  claim 18 , wherein the coating further comprises a charged compound which includes one or more sulfonate functionalities and one or more linkable functionalities selected from the group consisting of amine, monochlorotriazine and dichlorotriazine. 
     
     
         21 : The filtration apparatus of  claim 17 , wherein the coating is configured such that the filtration membranes are suitable for use as desulfation membranes in a Sulfate Removal Unit (SRU). 
     
     
         22 : The filtration apparatus of  claim 17 , further comprising a pre-treatment stage located upstream of the filtration membranes, the pre-treatment stage including at least one of ultrafiltration membranes, cartridge filters and sand-coated media filters which are configured to remove bacteria and suspended solids from seawater to be filtered by the filtration membranes. 
     
     
         23 : The filtration apparatus of  claim 17 , wherein the apparatus is located on the sea floor. 
     
     
         24 : The filtration apparatus of  claim 23 , wherein filtered water produced by the apparatus is suitable for use in a subsea injection well. 
     
     
         25 : The filtration apparatus of  claim 17 , wherein the filtration membranes are configured to yield 30% to 50% higher flux without degradation of sulfate rejection or rejection of total dissolved solids. 
     
     
         26 : The filtration apparatus of  claim 17 , wherein the apparatus is configured such that a de-chlorinator for removing cleaning chemicals is not required. 
     
     
         27 : The filtration apparatus of  claim 26 , wherein the apparatus is configured such that neither a chemical tank nor a de-chlorinator are required. 
     
     
         28 : The filtration apparatus of  claim 27 , wherein the filtration membranes are configured to be cleaned with hot water. 
     
     
         29 : The filtration apparatus of  claim 17 , wherein the filtration membranes are configured such that at least one of a low-dosage continuous injection of 0.5 ppm-1.0 ppm chlorine and periodic shock doses of 5 ppm chlorine will prevent bio-fouling. 
     
     
         30 : The filtration apparatus of  claim 17 , further comprising:
 a first tank which contains a coating chemical for use in coating the filtration membranes;   wherein the housing comprises an inlet to which the first tank is connected.   
     
     
         31 : The filtration apparatus of  claim 30 , further comprising:
 a mixing tank which is connected between the first tank and the inlet;   wherein the housing comprises a permeate outlet through which a permeate is discharged, the permeate outlet being connected to at least one of the second tank and a permeate tank which in turn is connected to the second tank; and   wherein the coating chemical from the first tank is combined with the permeate in the mixing tank prior to being communicated to the inlet of the housing.   
     
     
         32 : The filtration apparatus of  claim 31 , wherein the housing comprises a reject outlet through which a concentrate is discharged, and wherein the reject outlet is connected to the mixing tank for communication of the coating chemical from the housing to the mixing tank. 
     
     
         33 : The filtration apparatus of  claim 32 , further comprising a number of valves for selectively connecting either the reject outlet or at least one of the permeate outlet and the permeate tank to the mixing tank.