Silicon nitride porous body and its production process

A process for producing a silicon nitride porous body comprising:

• adding a molding aid and water to a mixture comprising 100 parts by mass of metallic silicon particles having an average particle diameter of from 1 to 150 μm and from 0.2 to 45 parts by mass, as SiO2, of silicon oxide particles and wherein the total amount of the metallic silicon particles and the silicon oxide particles is at least 80 mass% in the mixture,
• kneading the mixture, molding aid and water to provide a kneaded product,
• extrusion molding the kneaded product to provide an extrusion molded product having a cross-sectional area per through-hole of from 1 to 100 mm2, and
• heat-treating the extrusion molded product in nitrogen to nitride the metallic silicon, thereby providing a silicon nitride porous body having a generally columnar outer shape and at least two through-holes mutually parallel to one another and which has generally perpendicularly oriented columnar crystals on the surface of the through-holes.