Your question is a good one, but you have failed to provide essential information, along with some unnecessary information.  The only information you need is the maximum torque of the mixer, which is power divided by speed and the tank diameter.  You have provided the motor power, which is essential, but you failed to provide the rotational speed of the mixer which is necessary to calculate the mixer torque.  The input torque from the mixer must be taken out by the baffles, so the torque load by the mixer becomes the force load on the baffles divided by the tank diameter.
 
The tank height, baffle width, and slurry density will have no effect on the maximum load on the baffles.  The only other piece of information of possible interest is the number of baffles.  The logical assumption would be that the load on each baffle would be the same and a fraction of the total imposed torque.

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