Vane Wheel

http://www.innovativecombustion.com/raw_coal.html

Does this wheel rotates because of a torque from a shaft or does it rotates purely because of the airflow?

The vane wheel functions to direct the airflow so as to spin the fines and direct them to the outlet, while the heavier coarser pieces fall back to the bowl for further crushing.

Whether it moves or not really depends upon the design and manufacturer of the pulverizer. Some use a fixed table/bowl with rotating tires/wheels that do the crushing, in others the bowl rotates counter to the wheels.

Since the vane wheel is usually placed at the periphery of the bowl it can either be attached to it and rotate with it if it does, or fixed to the outer frame. In either case it's not the motion of the vane wheel that does the work, it's the airflow through the vanes that's important.

Thank you for your reply. So let me confirm, the vane wheel only directs the airflow so as to distribute the airflow equally through out the inside of the pulverizer, pushing the finest coal into the classifier. So if there's no vane wheel at the periphery of the bowl or if some blades of the vane wheel is broken / missing, then what happens to the overall performance of the pulverizer?

See the pulveriser as a system of which the vane wheel is a component. A faulty or damaged component compromises the system, making it more inefficient. Thus, the pulveriser becomes less able to perform the duty for which it is designed.

yes i know it will perform less then it should. I meant specifically, why and how does some missing/broken blade of the vane wheel affects the overall performance of the pulverizer?

I'm not sure the word "only" belongs there, but yes, the vane wheel was part of the evolution of the pulverizer system, there are manufacturers who can provide the vane wheel as a retrofit for improving the overall efficiency of the process.

Originally the air flow was in the annular space between the bowl and the frame providing a "wall" of air to carry out the pulverized coal, relying on gravity alone to return the heavier pieces. The vane wheel spins the air flow to provide a centrifuge-like mechanism to further clarify the particle size.

Like any mechanism, missing or damaged pieces reduce the overall performance.