The below paragraph explained the goals of this process, to a simpleton such as myself,  much better.

"Just to let you in a little secret, when Si is purified via a chemical process, all the impurities are removed, and that is what makes these processes very expensive (Plus the irony is that dopant has to be added to the material after to make it solar).  A metallurgical process is focussed on only removing the impurities that have a negative impact of the solar performance, and that is why overall our purity may be 5N+ but for the key problem impurities, it will be 9N."

Thank you.

HK