An hydraulic jet mill is disclosed in which a high pressure line and a low
pressure line are introduced into at least one jet (or nozzle). The jet
is configured such that there is an orifice at the forward end of the jet
and the cross sectional area of the interior of the rearward portion of
the jet is significantly greater than the cross sectional area of the
interior of the forward portion of the jet. There is an incompressible
liquid such as water in the high pressure line and a material to be
milled in a slurry with an incompressible liquid such as water in the low
pressure line. The high pressure line is introduced into the rearward
portion of the jet and the low pressure line is introduced through a
venturi into the forward portion of the jet. The contents of the high
pressure line and the low pressure line mix and are forced out of the
orifice at high velocity. The material is milled when it strikes either
an impingement plate or an opposed second jet.