Compressed air passed down the central pipe forms a froth, and pressure pushes it up the third pipe to the surface, where it runs into molds and hardens.  
Drill a hole down to the beds.  3 concentric pipes are lowered down the borehole.  Superheated steam passed down the outermost pipe melts the desired substance.  Compressed air passed down the central pipe forms a froth, and pressure pushes it up the third pipe to the surface, where it runs into molds and hardens.  FTP identify this process for extracting sulfur named after a German-born US chemist.
Drill a hole down to the beds.  3 concentric pipes are lowered down the borehole.  
Frasch process (prompt on "sulfur" before it is mentioned)