Bed packing material

A bed packing material in the form of units, each unit having

• (a) a multiplicity of passages of substantially uniform cross section extending lengthwise through the unit, said passages having an effective diameter of 0.03 to 1 mm, where the effective diameter is four times the cross-sectional area of the passage divided by the perimeter of the passage cross section, and there being at least 20 passages per cm.sup.2 of the unit cross section area;
• (b) a substantially uniform cross section;
• (c) a ratio of the length, L, to the notional cross section diameter, D, of at least 0.5, said notional cross section diameter being the diameter of the circle of area equal to the cross-sectional area the unit would have if there were no passages therethrough, the minimum of said length and notional cross section diameter being at least 3 mm;
• the number of said passages, and their size relative to said length, L, and notional cross section diameter, D, being such that each unit has
• (i) a geometric voidage, GV, of not more then 0.40;
• (ii) a ratio of the geometric surface area, GSA, to the volume, V, of the cylinder of length L and diameter D, of at least 10 cm.sup.-1 ;
• and
• (iii) a ratio of GSA to the product of GV and A of at least 15, where A is the surface area of the cylinder of length L and diameter D.