OSMOTIC CONCENTRATION OF PRODUCED AND PROCESS WATER USING HOLLOW FIBER MEMBRANE

Abstract

The invention relates to a method and apparatus for treatment of produced or process water from hydrocarbon production to reduce the volume of the produced or process water while simultaneously reducing the salinity of a highly saline stream, for example, the brine from a seawater desalination plant. The method includes causing a feed stream comprising produced or process water to flow through the lumen of a hollow fiber osmotic membrane 4 which is immersed in an open channel 2 or tank of flowing draw solution 6 which has high salinity. In this way, water from the feed stream is drawn through the osmotic membrane 4 by an osmotic pressure differential caused by the difference in salinity between the feed stream and the draw solution 6.

Claims

1. A method for the treatment of produced or process water from hydrocarbon production to reduce the volume of the produced or process water, the method comprising: a) causing a feed stream comprising produced or process water to flow through a lumen of a hollow fiber osmotic membrane; b) causing a draw solution comprising saline water of higher salinity than the produced or process water to flow past the outside of the hollow fiber osmotic membrane; c) whereby water from the feed stream is drawn through the osmotic membrane by osmotic pressure differential caused by a difference in salinity between the feed stream and the draw solution; wherein d) the saline water flows in an open channel or tank and the hollow fiber osmotic membrane is arranged in an immersed membrane configuration in the open channel or tank.

2. The method claimed in claim 1 wherein the feed stream is passed through between 1,000 and 10,000,000 hollow fiber membranes, preferably between 50,000 and 1,000,000, in a combination of series and parallel arrangements.

3. The method claimed in claim 2 wherein the feed stream is passed through more than 2 hollow fiber membranes connected sequentially in series, such as between 2 and 40 fiber membranes in series.

4. The method claimed in claim 1 wherein the membrane is part of a membrane module, the module comprising a plurality, such as between 250 and 5,000, fiber membranes mounted therein with respective ends of the fiber membranes mounted in an inlet header and an outlet header of the module.

5. The method of claim 4, wherein two or more said membrane modules are arranged in a frame.

6. The method of claim 5, wherein the lumens of two or more fiber membranes in respective modules and/or respective frames communicate in series.

7. The method claimed in claim 1 wherein the volume of the produced or process water is reduced by more than 25%, optionally more than 50%.

8. The method claimed in claim 1 wherein the volume of the produced or process water is reduced by between 25% and 90%, for example between 50% and 75%.

9. The method claimed in claim 1 wherein the draw solution is seawater, saline effluent from a water desalination plant or hypersaline groundwater.

10. The method claimed in claim 1, further comprising taking the feed stream downstream of the osmotic membranes and injecting it into a disposal well.

11. The method claimed in claim 1, further comprising taking the feed stream downstream of the osmotic membranes and treating it further prior to disposal.

12. The method claimed in claim 1, further comprising taking the draw solution downstream of the osmotic membranes and passing it into a desalination process or into the sea.

13. The method as claimed in claim 1, wherein the osmotic pressure differential is in the range 5 to 250 bar, optionally 10 to 60 bar.

14. The method as claimed in claim 1, wherein the produced or process water is subject to pre-treatment processes including suspended solids removal and oil removal.

15. The method of claim 1, wherein the interior diameter of the lumens of the hollow fiber membranes is between 0.1mm and 2.0 mm and the length of each hollow fiber membrane is between 0.25 m and 2.0 m.

16. The method of claim 1 wherein the feed water passes along the lumen of a continuous fiber membrane or series of sequentially connected fiber membranes of total length between 0.25 m and 80 m, optionally between 1 m and 40 m, such as between 5 m and 20 m, more particularly between 2 m and 10 m, and wherein the internal diameter of the fiber lumen is between 0.1 mm and 2.0 mm, optionally between 0.6 mm and 1.6 mm.

17. Apparatus for the treatment of produced or process water from hydrocarbon production to reduce the volume of the produced or process water, the apparatus comprising a plurality of hollow fiber osmotic membranes mounted in modules adapted for immersion in an open channel or tank, wherein at least two of said fiber membranes communicate in series.

18. The apparatus as claimed in claim 17, wherein two or more said membrane modules are provided, and wherein the lumen of at least one fiber membrane in one of said modules communicates in series with the lumen of at least one fiber membrane in a second one of said modules.

19. The apparatus as claimed in claim 17, wherein two or more said membrane modules are arranged in a frame adapted for immersion in said open channel or tank.

20. The apparatus as claimed in claim 19, wherein at least two said frames with modules mounted therein are connected such that the lumen of at least one fiber membrane in one of said frames communicates in series with the lumen of at least one fiber membrane in a second one of said frames.

21. The apparatus of claim 17, wherein the fiber membrane lumens have an internal diameter between 0.1 mm and 2.0 mm and said at least two series connected fiber membranes have total combined length of lumen between 0.25 m and 80 m, optionally between 1 m and 40 m, such as between 5 m and 20 m, more particularly between 2 m and 10 m.

22. A system comprising the apparatus as claimed in claim 17 together with an open channel or tank containing flowing draw solution in which the said apparatus is immersed, and a pumped supply of produced or process water communicating with the lumens of the fiber membranes, the draw solution having a higher salinity than the produced or process water.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] A more complete understanding of the present invention and benefits thereof may be acquired by referring to the following description taken in conjunction with the accompanying drawings in which:

[0035] FIG. 1 is a side sectional view of a water channel in which is located an immersed hollow fiber forward osmosis module; and

[0036] FIG. 2 is an isometric view of an open top tank containing a number of membrane frames, each frame containing a number of modules of the type shown in FIG. 1.

DETAILED DESCRIPTION

[0037] Turning now to the detailed description of the preferred arrangement or arrangements of the present invention, it should be understood that the inventive features and concepts may be manifested in other arrangements and that the scope of the invention is not limited to the embodiments described or illustrated. The scope of the invention is intended only to be limited by the scope of the claims that follow.

[0038] Referring to FIG. 1, a hollow fiber osmotic membrane module 1 is installed in an open concrete channel 2. The membrane module 1 consists of an inlet membrane header 3, a plurality of hollow fiber osmotic membranes 4 and an outlet membrane header 5. The channel 2 contains a flowing stream of high salinity draw solution 6, in this embodiment seawater. Alternatively, the draw solution 6 could be brine from a seawater desalination plant or hypersaline groundwater. A feed header 7 communicates with the inlet membrane header 3 of the module 1, whilst a concentrate header 8 communicates with the outlet membrane header 5 of the module.

[0039] In this embodiment, the module 1 has 1200 hollow fibers 4 connected in parallel between the inlet and outlet membrane headers 3, 5. However, in alternative arrangements it is possible to have the fibers divided into groups, with the fibers of each group connected in series. For example, a module may comprise 3 groups, each of 400 fibers connected in series.

[0040] Feed water, in this embodiment produced water from an oil and gas operation, is pumped to the feed header 7 and supplied from the feed header to the inlet membrane header 3. Alternatively, the feed water could be process water from nearby oil and gas processing operations or a blend of the two streams. The feed water flows upward through the osmotic membrane fibers 4. As the feed flows through the lumen of the fibers, because of the difference in salinity between the feed and the draw solution, water flows from the feed solution through the walls of the fiber and into the draw solution 6, but larger dissolved solids such as sodium or chloride ions or other impurities are unable to pass through the membrane. In this way, the feed solution is concentrated while the draw solution is diluted. The concentrated feed collects in the outlet membrane header 5 and is discharged from the system through the concentrate header 8.

[0041] The hollow fiber membrane construction can be comprised of a fabric base e.g. polypropylene, a polymer support layer, for example polyethersulfone and an active membrane separation layer made from, for example, m-phenylenediamine, caprolactam, sodium dodecyl sulfate, trimesoyl chloride and hexane by interfacial polymerization. The fiber can be constructed using information described in Wang et. al., “Characterization of novel forward osmosis hollow fiber membranes”, Journal of Membrane Science, 355, 158-167, (2010). Other possible chemistries for hollow fiber osmotic concentration membranes include membrane separation layers from cellulose triacetate, polybenzimidazole, cellulose acetate, polyether sulfone, or polyamide on polysulfone-based, sulfonated or cellulose acetate propionate support layers. The outside diameter of a hollow fiber membrane can range from 0.5 mm to 4 mm, preferentially between 1 and 2.5 mm. The inside diameter of the fiber can range from 0.1 mm to 2 mm, preferentially 0.6 to 1.6 mm. The length of the fiber can be 0.25 to 2 m, preferentially 0.5 to 1.5 m.

[0042] One module is depicted in FIG. 1, but the system consists of multiple membrane modules assembled in frames or racks.

[0043] Referring to FIG. 2, an open top membrane tank 11 contains four membrane frames 12 each comprising an array of eight membrane modules 13. Each membrane module 13 comprises inlet and outlet headers and 1200 hollow fiber osmotic membranes 14 extending between the headers, as described above in relation to FIG. 1. The modules are configured in a parallel arrangement, whereby the feed water flows through the lumens of all fibers and all modules in parallel and is collected in the outlet pipe 20. Alternative arrangements are possible, e.g., i) more or less than 8 modules per frame, or ii) where two or more of the modules are grouped so that the feed flow is in series, first through one group of modules and then through a second or more groups of modules one after the other. The arrangement and number of modules in series can be adjusted as required to meet the required overall volume reduction. Similarly, the number of modules in a parallel configuration can be adjusted as required to meet total flow requirements.

[0044] The tank 11 includes a draw solution inlet nozzle 15, a diluted draw solution outlet nozzle 16, a produced and process water feed solution header 17 and a concentrated produced and process water header 18. The membrane frames are provided with a feed downcomer 19 and a membrane outlet pipe 20. Between the membrane frames, vertical baffles 21 can be provided to prevent draw solution from bypassing the membrane frames. Similarly, valves 22 can be provided at appropriate places to facilitate frame isolation and maintenance.

[0045] In a similar manner to the arrangement of the modules, the frames can be arranged in series or parallel or a combination, as required to achieve the required flow rate and volume reduction. In this example, the four frames are configured in two parallel sets; each set comprised of two frames connected in series, i.e. the outlet 20 from one frame connected to the inlet downcomer 19 on the adjacent frame by crossover pipe 23. The configuration of the number of frames in parallel and series is flexible and is dependent of application specific criteria.

[0046] In operation, the higher salinity draw solution, e.g. seawater or concentrated brine, enters the tank through nozzle 15 and flows amongst and between the fibers. The lower salinity feed solution, e.g. the produced and process water from oil and gas operations, is pumped into the feed solution header 17, flows downward through the downcomers 19 and flows upward through the lumen of the hollow fiber osmotic membranes 14.

[0047] As noted in the description for FIG. 1, water flows from the lumen through the wall of the osmotic membrane fiber and into the draw solution because of the difference in salinity. The vast majority of the other materials in the feed do not pass through the membrane and hence become concentrated in the feed. The concentrated feed solution is collected in the outlet pipe 20.

[0048] If sufficient volume reduction has been achieved, the concentrated feed can be discharged to the header 18 ultimately to be discharged; if additional volume reduction is required, the concentrated feed can be routed via the crossover pipe 23 to the downcomer 19 on another frame in a series configuration. The diluted draw solution exits the tank through the outlet nozzle 16 and can be discharged, e.g. to another membrane tank, to the sea or returned as feed to the desalination plant.

EXAMPLE 1

[0049] The objective in this design example is two-fold: i) reduce the volume of a 50 m.sup.3/h feed stream of produced and process water by 50%, and ii) simultaneously reduce the salinity of a 100 m.sup.3/h thermal desalination plant brine by 25%. 60 osmotic membrane fiber modules are assembled in a frame, each module arranged vertically with its inlet membrane header at the bottom and outlet membrane header at the top, the membrane headers communicating respectively with a feed header and a concentrate header on the frame. Each module comprises 1,500 fiber membranes, each membrane having a length of 1.5 m and an inner lumen diameter of 1 mm.

[0050] A detailed description of how to make the fiber membranes can be found in the Wang article, full details of which are cited above, together with U.S. Pat. No. 8,181,794 (McGinnis et al.). Briefly, the fibers are made of a polyamide membrane separation layer as described in the Wang article on a polyethylene terephthalate support layer on a polypropylene fabric base as described in the McGinnis patent. The membrane separation layer is created by an interfacial polymerization technique. A solution of m-phenylenediamine (MPD) is brought into contact with the surface of the substrate, followed by interaction with a trimesoyl chloride (TMC) and hexane solution. Between the contact of the fibers with MPD and TMC solutions, a drier is used to remove droplets on the surface of the fibers. The fiber membranes have a design flux of about 15 l/m.sup.2-h.

[0051] 4 frames are installed in an open channel carrying 100 m.sup.3/h of brine, having a salinity of 60 g TDS/L. The 50 m.sup.3/h feed stream having a salinity of 2 g TDS/L is pumped through the membrane fibers. The average osmotic pressure differential is estimated to be 44.5 bar assuming 35° C. temperatures for both streams. The calculations below indicate that 4 such frames will provide the desired reduction in feed stream volume. These 4 frames will be configured into 2 sets, each with 2 frames in series. Details are given in Table 1 below.

TABLE-US-00001 TABLE 1 Fiber ID 1 mm Fiber length 1.5 m Design flux 14.7 L/m.sup.2-h Feed flow 50 m.sup.3/hr Feed volume reduction 50% Draw solution salinity reduction 25% Modules/frame 60 Fibers per module 1500 Feed velocity inside fiber 9.83 cm/s Area/fiber 0.00471 m.sup.2 Flow/fiber 0.0694 l/h per fiber No. of fibers needed 360,000 No. of modules 240 No. of frames 4.0 Feed flow/set of frames 25 m.sup.3/hr No. of sets of frames 2 No. of frames in series per set 2 Salinity of upstream draw solution 60 g TDS/L Salinity of downstream draw solution 48 g TDS/L Salinity of the feed PPW 2 g TDS/L Salinity of the concentrated PPW 4 g TDS/L Average osmotic pressure differential 44.5 bar

[0052] In closing, it should be noted that the discussion of any reference is not an admission that it is prior art to the present invention, especially any reference that may have a publication date after the priority date of this application. At the same time, each and every claim below is hereby incorporated into this detailed description or specification as additional embodiments of the present invention.

[0053] Although the systems and processes described herein have been described in detail, it should be understood that various changes, substitutions, and alterations can be made without departing from the spirit and scope of the invention as defined by the following claims. Those skilled in the art may be able to study the preferred embodiments and identify other ways to practice the invention that are not exactly as described herein. It is the intent of the inventors that variations and equivalents of the invention are within the scope of the claims while the description, abstract and drawings are not to be used to limit the scope of the invention. The invention is specifically intended to be as broad as the claims below and their equivalents.

REFERENCES

[0054] All of the references cited herein are expressly incorporated by reference. The discussion of any reference is not an admission that it is prior art to the present invention, especially any reference that may have a publication date after the priority date of this application. Incorporated references are listed again here for convenience: [0055] 1. Wang, R., et al., “Characterization of novel forward osmosis hollow fiber membranes”, JMS, 355, 158-167. (2010) [0056] 2. Minier-Matar et al., “Advances in Application of Forward Osmosis Technology for Volume Reduction of Produced/Process Water from Gas-Field Operations”, IPTC-18380-MS, 6-9 December 2015 [0057] 3. Minier-Matar et al., “Application of Forward Osmosis for Reducing Volume of Produced/Process Water from Oil and Gas Operations”, Desalination 376 (2015) 1-8 [0058] 4. Minier-Matar et al., “Application of Hollow Fiber Forward Osmosis Membranes for Produced and Process Water Volume Reduction: An Osmotic Concentration Process”, Environmental Science & Technology 50, No. 11, 6044-6052 (2016).