The video shows the "purification" of zinc metal (probably covered with an oxide layer) by heating/reacting it with powdered carbon.
This is a very common process to reduce metal oxides to the corresponding metals. In turn, carbon is oxidized to carbon monoxide and carbon dioxide. The most prominent example is the production of iron from iron oxide in a blast furnace.
However for some metals, this fails and metal carbides are formed instead.
For tin oxide, the reduction with carbon (or coke) is an established industrial process.
Alternatively, the reduction of tin oxide can can be achieved using hydrogen, see Materials Transactions, 2011, 52, 1814-1817 (PDF).