thereof as syncrude with the particles of material for removing the contaminant will be described hereinafter in carrying out the invention as outlined hereinbefore the guard beds are formed by depositing pellets or other particles of the material into respective pessure vessels the guard beds are labeled in the figure as low temperature guard bed lo temp grd bed and high temperature guard bed hi temp grd bed respectively the vessels are adapted to withstand the pressure and temperature necessary to effect the removal of the contaminant arsenic or selenium whether in elemental or combined form the particles of material may have any shape and any of the sizes that are employable in this art specifically the particles must not be so small as to pack into a flow blocking mass or so large as to render internal area of the particles of contaminant removing material inaccessible to the fluid and contaminant ordinarily the particles of material will comprise extrudates or pellets of from 1 32 to 1 4 inch or more in diameter and 1 8 inch or more in length or spheroidal particles within the diameter range of 1 32 to 1 4 inch the contaminant removing material may comprise active material.