first mode the speed of rotation of the impeller is in the order of 750 rpm but can be up to about 1000 rpm this will cause the material inside the vessel 202 to rotate forming a vortex at this speed the liquid or semi liquid material located at or near the walls in the process vessel in the region below the guide collar 212 will be drawn upwards and into the impeller 300 the collar cone 310 by virtue of its cone shape will support the flow into the impeller to render the transport more efficient the guide collar 212 will effectively function as a partition wall between the upper and lower part of the process vessel thereby preventing material that has been treated inside the impeller to mix too rapidly with untreated material below the collar 212 eventually of course the material will in some sense be u201c homogeneous u201d and only when new material is fed into the system an inhomogeneous situation occurs and the process of oxygenation will become operative due to the construction of the impeller 300 with its truncated cone configuration there will be created a suction due to the formation of a vortex inside the lower compartment 301 b of the impeller 300 thereby air from the environment will be sucked in through the hollow shaft and also liquid will be sucked in through the.