Abstract: In a fine particle producing device, particles of a substance contained in a fluid are caused to collide with each other under extremely high pressure, whereby the particles are emulsified, dispersed or reduced to finer particles in the fluid in an instant. One of the blocks mounted in a cylindrical sealed casing has a pair of curved channel portions for guiding converging high-speed fluid streams and a turbulence pocket formed at a position where the curved channel portions are joined for temporarily holding fluid turbulence caused by collision of the high-speed fluid streams.

Abstract: Disclosed is a process for producing stone groundwood pump from wood chips, by compressing a wood chip mass into an apparent volume corresponding to 70% or less, preferably, from 40 to 60%, of the original apparent volume of the wood chip mass and by grinding the compressed wood chip mass, under pressure, with a stone grinder. The wood chips may be treated, before the grinding step, with both or either one of steam and a treating agent, such as sodium monosulfite, sodium disulfite and sodium bicarbonate.