Apparatus and method for liquids and gases

An apparatus for mixing a gas with a liquid, the apparatus comprising:

• a tube having a longitudinal axis and two ends, with a first end being a liquid input end and a second end being a liquid outlet end, the tube providing a first portion of a main fluid path that extends through the apparatus;
• a helical vane disposed inside the tube, dividing the first portion of the main fluid path into two fluid path regions;
• a tubular structure extending from the first end of the tube and located upstream of the helical vane and aligned with the longitudinal axis of the tube, the tubular structure providing a second portion of the main fluid path and having a sidewall configured to allow gas to flow there through at a plurality of locations around a circumference of the tubular structure;
• a joint pipe having an inner wall defining an inner diameter sized to receive the tubular structure and the first end of the tube, and to provide an annular space between the inner wall and the sidewall of the tubular structure;
• a gas injection port associated with the joint pipe and located upstream of the helical vane, the gas injection port adapted to inject gas into the annular space, through the sidewall of the tubular structure and into the second portion of the main fluid path provided by the tubular structure;
• and
• a ring structure located upstream of the helical vane and downstream of the gas injection port and the tubular structure, the ring structure extending around an outer wall of the tube and positioned between the inner wall of the joint pipe and the outer wall of the tube to define a downstream end of the annular space.