If the crushing rolls 1m in diameterare set so that the crushing surfaces are 12.5m apart & the angle of is ,?

Question

31 degree, what is the maximum size of particle which should be fed to the rolls? .(question of unit operation related to chemical engg)

Answer 1

Presumably you meant 12.5 mm separation and the angle of minimum purchase of the rollers is 31°.
d = 2[(500 + 6.25)/cos31° - 500] ≈ 181 mm

If you really did mean 12.5 m separation,
d = 2[(0.5 + 6.25)/cos31° - 0.5] ≈ 3.687 m