Intermittent mixer with low pressure drop

A mixer for mixing two gas streams, comprising:

• a housing having a first inlet passage for a first gas stream, a second inlet passage for a second gas stream, an outlet passage for a mixed first and second gas stream, and a mixing passage between the inlet passages and the outlet passage, the mixing passage having an axis;
• a plurality of damper vanes extending at least partly across the mixing passage and having a mixing position for mixing together the gas streams from the first and second inlet passages to supply a mixed gas stream to the outlet passage at relatively high pressure drop in the mixing passage, the vanes having a non-mixing position for passage of the gas streams from the first and second inlet passages without mixing to supply unmixed gas streams to the outlet passage at relatively low pressure drop, the vanes in the non-mixing position being parallel to, and spaced from each other, with each vane lying in a plane that is parallel to the axis of the mixing passage;
• each vane extending from a bottom to a top of the mixing passage and the vanes being spaced from each other horizontally across the mixing passage;
• and
• actuator means connected to the vanes for moving the vanes to the mixing position when mixing is needed, the actuator means moving the vanes to the non-mixing position when mixing is not needed.