The Collaborative International Dictionary of English v.0.48:

Refiner \Re*fin"er\ (-f?n"?r), n.
   One who, or that which, refines.
   [1913 Webster]

WordNet (r) 3.0 (2006):

refiner
    n 1: one whose work is to refine a specific thing; "he was a
         sugar refiner"

Easton's 1897 Bible Dictionary:

Refiner
   The process of refining metals is referred to by way of
   illustrations in Isa. 1:25; Jer. 6:29; Zech. 13:9; Mal. 3:2, 3.