Spiral separation membrane element
A spiral-type separation membrane element is provided that can reduce the pressure loss without changing the outer diameter and the inner diameter of the water-collecting tube. In a spiral-type separation membrane element in which a separation membrane, a feed-side flow passageway member, and a permeate-side flow passageway member are wound in a spiral form around a porous water-collecting tube in a laminated state, the feed-side flow passageway member includes a net-constituting thread in a direction tilted relative to a feed solution flow direction; the net-constituting thread has a cross-sectional part such that a thread diameter X in a direction parallel to a feed solution flow plane is larger than a thread diameter Y in a direction perpendicular to the feed solution flow plane; and a central part between intersection parts of the net-constituting thread is made to have a thread diameter Y smaller than that of an intersection part.
1. A spiral-type separation membrane element in which a separation membrane, a feed-side flow passageway member, and a permeate-side flow passageway member are wound in a spiral form around a porous water-collecting tube in a laminated state, characterized in that
said feed-side flow passageway member includes a first net-constituting thread in a direction tilted relative to a feed solution flow direction,
the first net-constituting thread has a cross-sectional part such that a thread diameter in a direction parallel to a feed solution flow plane (X) is larger than a thread diameter in a direction perpendicular to the feed solution flow plane (Y), wherein the first net-constituting thread has a ratio (X/Y) within a range from 1.1 to 1.5, and
a central part between intersection parts of the first net-constituting thread is made to have a thread diameter in a direction perpendicular to the feed solution flow plane (Y P1 ) smaller than a thread diameter in a direction perpendicular to the feed solution flow plane (Y P2 ) of an intersection part.
2. The spiral-type separation membrane element according to claim 1 , wherein said feed-side flow passageway member further includes a second net-constituting thread tilted in a reverse direction relative to the feed solution flow direction while intersecting with said first net-constituting thread,
the second net-constituting thread has a cross-sectional part such that a thread diameter in a direction parallel to the feed solution flow plane (X) is larger than a thread diameter in a direction perpendicular to the feed solution flow plane (Y), and
a central part between intersection parts of the second net-constituting thread is made to have a thread diameter in a direction perpendicular to the feed solution flow plane (Y P1 ) smaller than a thread diameter in a direction perpendicular to the feed solution flow plane (Y P2 ) of an intersection part.
3. The spiral-type separation membrane element according to claim 1 , wherein the ratio (Y P1 /Y P2 ) of thread diameter Y at the central part (P 1 ) of the first net-constituting thread located between intersection parts, relative to thread diameter Y at intersection part (P 2 ) of the first net-constituting thread is from 0.2 to 0.8.
4. The spiral-type separation membrane element according to claim 2 , wherein the ratio (Y P1 /Y P2 ) of thread diameter Y at the central part (P 1 ) of the second net-constituting thread located between intersection parts, relative to thread diameter Y at intersection part (P 2 ) of the second net-constituting thread is from 0.2 to 0.8.
5. The spiral-type separation membrane element according to claim 2 , wherein the thickness of the intersection part of said first and said second net-constituting threads is from 0.5 mm to 2.0 mm.
6. The spiral-type separation membrane element according to claim 1 , wherein said first net-constituting thread has an elliptic cross-sectional shape.
7. The spiral-type separation membrane element according to claim 2 , wherein at least one of said first and/or second net-constituting threads has an elliptic cross-sectional shape.
8. The spiral-type separation membrane element according to claim 1 , wherein the first net-constituting thread has a ratio (X/Y) within a range from 1.1 to 1.3.