10"=.8333Ft diam = .4166ft radius
WK^2 = weight*(r^2/2 + r^2/2) for a hollow cylinder. Not quite true here but should be a good estimate.
wk2=20*(.4166)^2 = 3.47#ft^2
Tq to accel = (wk2 * delta rpm)/(308 * time in sec)
Tq= (3.47*6000)/(308*10) = 6.77 #ft
HP = Tq*base speed/5250 = 6.77 * 6000/5250 = 7.74HP
This assumes no losses and that the 6000rpm is the base speed of the motor. Especially note it did not include the HP required to accel the motor itself. So if you found a 10HP, 6000rpm motor, it should work.
Note if you go to a lower base speed motor and gear up, you still will require 7.74 for the centrifuge, you still have to include the motor and you will also have to include any gearing. By choosing 6000 rpm, I was saying it was direct geared, although this is not likely.