Composite porous hollow fiber membrane, composite porous hollow fiber membrane module, and operation method for composite porous hollow fiber membrane module

A composite porous hollow-fiber membrane comprising a first layer and a second layer which each comprise a fluororesin-based polymer, wherein

• at least a part of molecular chains of the fluororesin-based polymer is oriented in a longitudinal direction of the composite porous hollow-fiber membrane,
• the molecular chains of the fluororesin-based polymer have a degree of orientation π in the longitudinal direction of the composite porous hollow-fiber membrane of 0.4 or higher but less than 1.0, the degree of orientation π being calculated with the following formula (1),
• the first layer has a columnar texture oriented in the longitudinal direction of the composite porous hollow-fiber membrane,
• the columnar texture has a short-side length of 0.5 μm to 3 μm and has an aspect ratio of 3 or higher,
• the second layer has a three-dimensional network texture and has an average surface-pore diameter of 5.0 nm to 5.0 μm:
• Degree of orientation π=(180°−H)/180° (1),
• provided that H is a half-value width (°) of a circumferential-direction diffraction intensity distribution of a wide-angle X-ray diffraction image, and
• the short-side length and the aspect ratio of the columnar texture are measured by the following procedure:
• the composite porous hollow-fiber membrane is cut along the longitudinal direction of the composite porous hollow-fiber membrane to obtain a section;
• the section obtained is examined using a scanning electron microscope (SEM);
• three arbitrarily selected fields of view each including five columnar textures are examined to obtain values of longitudinal length of the columnar textures, and an average value of the obtained values of longitudinal length of the columnar textures is determined as a representative value of the longitudinal lengths of the columnar textures;
• in the three arbitrarily selected fields of view and at each of a given number of arbitrary measuring points, wherein the given number of arbitrary measuring points is a value obtained by dividing the longitudinal length (μm) by 1 μm while omitting any figures below the decimal point, a short-side length of one columnar texture is measured, and an average value of the obtained values of the short-side lengths is determined as a representative value of short-side length;
• and
• the aspect ratio of the columnar texture is calculated from the representative value of longitudinal length and the representative value of short-side length.