Gas dissolution accelerating device

A gas dissolution accelerating device to be installed above a diffuser, the device comprising:

• a first box member having a first opening facing downward when installed and including a first top plate with a first through-hole;
• a first cylindrical member located parallel to a vertical direction when installed;
• a second box member having a second opening facing downward when installed and including a second top plate with a second through-hole;
• and
• a second cylindrical member located parallel to the vertical direction when installed,
• wherein the first cylindrical member is received in the first through-hole with a length extending downward from the first top plate falling within a depth of the first box member,
• the second cylindrical member is received in the second through-hole with a length extending downward from the second top plate falling within a depth of the second box member,
• the first box member has, at a position excluding the first through-hole in the first top plate, a first conical protrusion protruding downward from the first top plate, and the first protrusion has a width in a longitudinal cross section gradually reducing toward an apex and a concavely curved side surface, and has a height falling within the length of the first cylindrical member extending downward from the first top plate, and
• the second box member has, at a position excluding the second through-hole in the second top plate, a second conical protrusion protruding downward from the second top plate, and the second protrusion has a width in a longitudinal cross section gradually reducing toward an apex and a concavely curved side surface, and has a height falling within the length of the second cylindrical member extending downward from the second top plate, and the second box member is located below the first box member with an upper end of an opening of the second cylindrical member located immediately below a tip of the first protrusion in the first box member.