Mixing apparatus

A mixing apparatus, which comprises:

• a vertical cylindrical tank;
• a rotating shaft vertically installed at the center of said tank;
• a plurality of stages of paddle impellers, at least two stages of which consist of two blades vertically fixed so as to symmetrically radially extend from said shaft,
• at least one of said blades having a vertical dimension which is at least as great as a horizontal dimension thereof,
• a lowest stage impeller of the impellers consisting of two blades disposed in proximity with the bottom of said tank and having an impeller diameter of at least substantially one-half the inner diameter of said tank and defining a radial space between the cylindrical tank wall and said lowest impeller for insertion of baffle plates,
• each upper stage impeller of the impellers having an impeller diameter substantially the same as or smaller than the next lower stage impeller and being placed on said shaft so as to form a clearance from the next lower stage impeller of not more than 20% of the diameter of the tank, wherein each upper stage impeller is set at an angle of between 45 and 75 degrees as measured around said shaft in a diameter of impeller rotation from the next lower stage impeller.

A mixing apparatus, which comprises:

• a vertical cylindrical tank;
• a rotating shaft vertically installed at the center of said tank;
• and
• a plurality of stages of paddle impellers each of which consists of two blades vertically fixed so as to symmetrically radially extend from said shaft,
• each of said blades having a vertical dimension which is at least as great as a horizontal dimension thereof,
• a lowest stage impeller of the impellers having both blades disposed in proximity with the bottom of said tank and having an impeller diameter at least substantially one-half the inner diameter of said tank and defining a radial space between the cylindrical tank wall and said lowest impeller for insertion of baffle plates,
• each upper stage impeller of the impellers having an impeller diameter substantially the same as or smaller than the next lower stage impeller and being placed on said shaft so as to form a vertical space from the next impeller of not more than 20% of the diameter of the tank, and
• each upper stage impeller being set at a crossing angle of less than 90 degrees but greater than 0 degree as measured around said shaft in a direction of impeller rotation from the next lower stage impeller.

A mixing apparatus, which comprises:

• a vertical cylindrical tank;
• a rotating shaft vertically installed at the center of said tank;
• and
• a plurality of stages of paddle impellers each of which consists of a single pair of blades vertically fixed so as to symmetrically radially extend from said shaft,
• each of said blades having a vertical dimension which is at least as a great as a horizontal dimension thereof,
• a lowest stage impeller of the impellers having both blades disposed in proximity with the bottom of said tank and having an impeller diameter at least substantially one-half of the inner diameter of said tank and defining a radial space between the cylindrical tank wall and the blades of said lowest impeller allowing a radial space enough to insert baffle plates,
• each upper stage impeller of the impellers having an impeller diameter substantially the same as or smaller than the next lower stage impeller and being placed on said shaft so as to form a clearance from the next impeller of not more than 20% of the diameter of the tank wherein the next lowest stage impeller has a radially outer edge part which extends rearward with respect to the direction of impeller rotation.

A mixing apparatus which comprises:

• a rotating shaft vertically oriented;
• and
• a plurality of stages of paddle impellers each of which consists of a single pair of blades vertically fixed so as to symmetrically radially extend from said shaft,
• each of said blades having a vertical dimension at least as great as a horizontal dimension thereof, and
• each upper stage impeller having an impeller diameter substantially the same as or smaller than the next lower stage impeller and being placed on said shaft so as to form a clearance from the next impeller of not more than one-third of the diameter of said lowest stage impeller, wherein each upper stage impeller is set at a crossing angle of between 45 and 75 degrees as measured around said shaft in the direction of impeller rotation from the next lower stage impeller.

A mixing apparatus, which comprises:

• a vertical cylindrical tank;
• a rotating shaft vertically installed at the center of said tank;
• and
• a plurality of stages of vertically adjacent paddle impellers each of which consists of a single pair of blades vertically fixed so as to symmetrically radially extend from said shaft, each of said blades having a vertical dimension at least as great as a horizontal dimension thereof,
• a lowest stage impeller of said impellers having a radially outer edge part which extends rearward with respect to the direction of impeller rotation and disposed in proximity with the bottom of said tank and having an impeller diameter of at least substantially one-half of the inner diameter of said tank and defining a radial space between the cylindrical tank wall and said lowest impeller allowing enough radial space to insert baffle plates,
• at least one upper stage impeller of the impellers having an impeller diameter substantially the same as or smaller than the next lower stage impeller and being placed on said shaft at a predetermined height such that the vertical space between said upper stage impeller and the next lower stage impeller is not more than 20% of said tank diameter at a part closest to said shaft and that at the same time said impellers only partly overlap in the vertical direction at a blade edge part furthest from said shaft where either of said two impellers has at least one blade member vertically extended to the other impeller.