An experimental study on the mixing characteristics of a continuous solid mixer was carried out by use of a tracer response method. The concentration of tracer in the outlet stream was measured continuously by an optical method.
The flow pattern of solids in the mixer was estimated from the dead time, the attaining time to a steady state of response and the first order moment of the residence time distribution.
The degree of mixedness was determined as the function of standard deviation at a steady state.
The following results were obtained:
1) A suitable type of the agitator for a continuous solid mixer was a double herical ribbon (S_R>70cm² where S_R: area of contacting surface of a ribbon and supporting rods within a height of 10cm of hold-up)
2) When the pitch of outer ribbon P₀ was small and the hold-up H and flow rate F were large, the degree of mixedness tended towards inferiority.
3) A good mixing condition was obtained by using the ribbon type of P₀/D₀=1.5, in the range of 7<H<15cm and rotating speed N=100r.p.m.
4) The best shape of the ribbon within the limits of the experiment was as follow:
ratio of outer pitch to outer diameter of the ribbon: P₀/D₀=1.5 setting angle of the ribbon: α=26° ratio of the projection area of the ribbon to the base area: b=0.72

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A mixing characteristics of continuous solid mixer was studied by use of tracer response method under various operating conditions.
An agitator shape used in this work was a rotary type that was divided a continuous double herical ribbon into smaller height sections and arranged with separation, distance h_scm.
The following results were obtained:
1) In the case of large hold-up, the back-flow mixing between the stages could be considerably reduced by the set of a suitable space between each ribbon.
2) The mixing region was obtained individually in each stage in the case of higher ribbon distance than 6cm and the experimental response curves were well explained by means of perfect mixers in series model.
3) The effect of the flow rate on the degree of mixedness was almost negligible. The mixing characteristics was improved as the rotating speed increased and in the case of N>100r.p.m., the mixing condition was desirable.
4) As the number of ribbon stage increased, the degree of mixedness was become better. The degree of mixedness in the outlet stream reached the fimal degree of mixedness by employing 3 stages for RA-type ribbon and 2 stages for RB-type ribbon, respectively.

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