A geometrical isomer of an acrylonitrile compound represented by the formula or of its salt, or a mixture thereof: . The plurality of pressurizers 31, 32 operate complementarily manner, thereby a constant pressure is applied to the discharge material fed to the feeder part 41. In one embodiment, one or more of the alignment tools includes at least one alignment pin which extends through a bolt hole of the first flange and beyond the face of the flange so that the alignment pin can engage one of the bolt holes of the second flange and thereby maintain rotational alignment of the flanges.