This application is being filed as a PCT International Patent application on May 30, 2018 in the name of Conwed Plastics LLC, a U.S. national corporation, applicant for the designation of the U.S., SWM Luxembourg S.A.R.L., applicant for the designation of all countries except the U.S., and Alexander James Kidwell, a U.S. Citizen; inventor for all designated states; and claims priority to U.S. Patent

Application No. 62/512,523, filed May 30, 2017, the contents of which are herein incorporated by reference in its entirety.

Field of the Technology

The present application relates to a feed spacer. More specifically, the present application relates to a feed spacer for spiral wound elements used for a pressure driven membrane separation process. These pressure driven membrane separation processes include microfiltration, ultrafiltration, nanofiltration and reverse osmosis.

Background

Membrane separation is commonly employed to extract pure or drinkable water from salt water and brackish water. Spiral wound elements are used that employ osmotic filtration membranes. Frequently spiral wound elements can result in large pressure gradients across them and can also demonstrate significant biofouling. The membranes are separated by a feed spacer net that can keep the membranes at a prescribed separation distance. The feed spacer also allows tangential flow of the pressurized input water between adjacent filtration membranes. A spacer net that produces a minimal drop in pressure as water flows through it and it resists accumulation of mineral and organic deposits (biofouling) can be desired. The spacer can also impart minimum deformation into the membrane surface during use and during assembly of the element.

Summary

Embodiments disclosed herein include a spacer for membrane separation systems, the spacer comprising a plurality of strands forming a mesh. The strands typically align at an angle of 20 to 90 degrees, with a strand count in the typical range of nine by nine per inch, down to three by three per inch. The spacers can have, for example a thickness of 15 to 50 mils. Reduction in strand angle and reduction in strand count can demonstrate reductions in bio fouling, as well as prevent (or attenuate) increases in pressure drop. This summary is an overview of some of the teachings of the present application and is not intended to be an exclusive or exhaustive treatment of the present subject matter. Further details are found in the detailed description and appended claims. Other aspects will be apparent to persons skilled in the art upon reading and understanding the following detailed description and viewing the drawings that form a part thereof, each of which is not to be taken in a limiting sense. The scope of the present application is defined by the appended claims and their legal equivalents.

Brief Description of the Figures

The technology may be more completely understood in connection with the following drawings, in which: Figure 1 is an enlarged top view of a spacer for membrane separation made in accordance with an implementation, the figure showing an angle a between the strands.

Figure 2 is a top perspective view of two test cells, showing spacers with two different constructions. The spacer on the left has an angle a between strands of approximately 90 degrees, while the spacer on the right has an angle a between strands of approximately 50 degrees.

Figure 3 A is an enlarged image of a spacer with 90 degree angles between strands, at the start of a membrane separation differential pressure test.

Figure 3b is an enlarged image of a spacer with 50 degree angles between strands and a lower strand count, at the start of a membrane separation differential pressure test.

Figure 4A is an enlarged image of a spacer with 90 degree angles between strands, at the start of a membrane separation differential pressure test at 9:30 a.m. on the first day following starting of testing.

Figure 4B is an enlarged image of a spacer with less than 90 degree angles between strands and a lower strand count, at the start of a membrane separation differential pressure test at 9:30 a.m. on the first day following starting of testing.

Figure 5A is an enlarged image of a spacer with 90 degree angles between strands, at the start of a membrane separation differential pressure test at 9:30 a.m. on the second day.

Figure 5B is an enlarged image of a spacer with less than 90 degree angles between strands and a lower strand count, at the start of a membrane separation differential pressure test at 9:30 a.m. on the second day. Figure 6A is an enlarged image of a spacer with 90 degree angles between strands, at the start of a membrane separation differential pressure test at 9:30 a.m. on the third day.

Figure 6B is an enlarged image of a spacer with less than 90 degree angles between strands and a lower strand count, at the start of a membrane separation differential pressure test at 9:30 a.m. on the third day.

Figure 7 A is an enlarged image of a spacer with 90 degree angles between strands, at the start of a membrane separation differential pressure test at a stopping point at 4:30 p.m. on the third day.

Figure 7B is an enlarged image of a spacer with less than 90 degree angles between strands and a lower strand count, at the start of a membrane separation differential pressure test at a stopping point at 4:30 p.m. on the third day.

Figure 8 is a graph and figures showing differential pressure at various times during a test, showing the membrane separators at various time intervals over three ours, including figures of corresponding fouling levels.

While the technology is susceptible to various modifications and alternative forms, specifics thereof have been shown by way of example and drawings, and will be described in detail. It should be understood, however, that the application is not limited to the particular embodiments described. On the contrary, the application is to cover modifications, equivalents, and alternatives falling within the spirit and scope of the technology. Detailed Description

Membrane separation is a water purification technology that can be used to desalinate salt water or produce clean water from brackish water. Membrane separation systems can have an input of salt water or brackish water and output of pure water or substantially pure water. Membrane separation system can also have an output of salty water or other contaminants that were included in the input but removed from the pure water output.

Embodiments disclosed herein include a spacer for membrane separation systems, the spacer comprising a plurality of strands forming a mesh. Figure 1 is an enlarged top view of a spacer for membrane separation made in accordance with an implementation, the figure showing an angle a between the strands. The spacer, typically an extruded or expanded polymeric material, generally have strands which align at an angle a of 20 to 90 degrees. In some implementations the stands align at an angle a of greater than 20, greater than 30, greater than 40 or greater than 50 degrees. In various implementations the strands align at an angle a of less than 90 degrees, less than 80 degrees, less than 70 degrees, less than 60 degrees, or less than 50 degrees. Desirable ranges of strand angles a include 30 to 70 degrees, 40 to 60 degrees, 45 to 55 degrees, 50 to 60 degrees, and 55 degrees.

Strand count can be, for example, from nine by nine per inch, down to three by three per inch, in some embodiments. Alternatively, strand counts can be

approximately eight by eight per inch, seven by seven per inch, six by six per inch, five by five per inch, or four by for per inch (as well as intermediate ranges, such as five and a half by five and a half per inch).

The spacers can have, for example, a thickness of 15 to 50 mils. In some implementations the strand thickness is less than 15 mils or greater than 50 mils. Examples include 17 to 46 mils, as well as 20 to 40 mils and 25 to 35 mils.

Suitable specific embodiments include a spacer element with a 55 degree angle and approximately five by five strands per inch and a thickness of less than 46 mils.

Figure 2 is a top perspective view of two test cells, showing spacers with two different constructions. The spacer on the left has an angle between strands of approximately 90 degrees, while the spacer on the right has an angle between strands of approximately 50 degrees.

Figures 3 A to 7B show images of membrane spacers from accelerated bio fouling tests. Figure 3 A is an enlarged image of a spacer with 90 degree angles between strands and 9 strands per inch, at the start of a membrane separation differential pressure test. Figure 3B is an enlarged image of a spacer with less than 90 degree angles (50 degrees) between strands and a lower strand count (6 strands per inch), at the start of a membrane separation differential pressure test. The two spacers show no fouling.

Figure 4A is an enlarged image of a spacer with 90 degree angles between strands, at the start of a membrane separation differential pressure test at 9:30 a.m. on the first day following starting of testing. Figure 4B is an enlarged image of a spacer with less than 90 degree angles between strands and a lower strand count, at the start of a membrane separation differential pressure test at 9:30 a.m. on the first day following starting of testing. The two spacers show very little fouling, especially the spacer with an angle of less than 90 degrees.

Figure 5A is an enlarged image of a spacer with 90 degree angles between strands, at the start of a membrane separation differential pressure test at 9:30 a.m. on the second day. Figure 5B is an enlarged image of a spacer with less than 90 degree angles between strands and a lower strand count, at the start of a membrane separation differential pressure test at 9:30 a.m. on the second day. The two spacers show some fouling, but significantly more fouling on the spacer that is arranged at 90 degrees, while the spacer at much smaller angle shows very little fouling.

Figure 6A is an enlarged image of a spacer with 90 degree angles between strands, at the start of a membrane separation differential pressure test at 9:30 a.m. on the third day. Figure 6B is an enlarged image of a spacer with less than 90 degree angles between strands and a lower strand count, at the start of a membrane separation differential pressure test at 9:30 a.m. on the third day. The spacer at 90 degree angle and higher strand count has far more fouling than the spacer with a smaller angle and lower stand count.

Figure 7A is an enlarged image of a spacer with 90 degree angles between strands, at the start of a membrane separation differential pressure test at a stopping point at 4:30 p.m. on the third day. Figure 7B is an enlarged image of a spacer with less than 90 degree angles between strands and a lower strand count, at the start of a membrane separation differential pressure test at a stopping point at 4:30 p.m. on the third day. The spacer at 90 degree angle and higher strand count has far more fouling than the spacer with a smaller angle and lower stand count.

Figure 8 is a graph showing differential pressure at various times during a test, showing the membrane separators at various time intervals over three days, including figures of corresponding fouling levels.

It should be noted that, as used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the content clearly dictates otherwise. Thus, for example, reference to a composition containing "a compound" includes a mixture of two or more compounds. It should also be noted that the term "or" is generally employed in its sense including "and/or" unless the content clearly dictates otherwise.

It should also be noted that, as used in this specification and the appended claims, the phrase "configured" describes a system, apparatus, or other structure that is constructed or configured to perform a particular task or adopt a particular configuration to. The phrase "configured" can be used interchangeably with other similar phrases such as arranged and configured, constructed and arranged, constructed, manufactured and arranged, and the like.

All publications and patent applications in this specification are indicative of the level of ordinary skill in the art to which this technology pertains. All publications and patent applications are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated by reference.

The technology has been described with reference to various specific and preferred embodiments and techniques. However, it should be understood that many variations and modifications may be made while remaining within the spirit and scope of the technology.