The
cryogenic feeder is a specially constructed stainless
steel heat exchanger designed to optimize heat transfer,
using liquid nitrogen as a refrigerant. The feeder
is suitable for precooling a wide variety of materials,
including plastic, rubber, food and drugs to their
embrittlement temperature for cryogenic grinding operations.
Heavy-Duty components and simplicity of construction
assure a durable and reliable cryogenic cooling system.
The
cooling conveyor operates with high thermal efficiency
resulting in lower nitrogen consumption. The material
is cooled to it's embrittlement temerature traveling
through the cooling conveyor. When the material is
passed through the pulverizer it is reduced to the
required size. Some products can be reduced to as
low as -325 mesh.
The
material to be ground is loaded into a feed hopper.
From the hopper, the material enters the cooling conveyor
where liquid nitrogen at -320 F is sprayed directly
onto the material. The liquid nitrogen vaporizes to
a gas by absorbing the required heat of vaporization
from the feed material. Seeking thermal equilibrium,
the cold nitrogen gas continues to cool the feed material
to its embrittlement point.
A
thermocouple and temperature controller are used to
control and monitor the temperature within the cooling
conveyor and the grinding mill discharge hopper. The
material enters the Pulva-Sizer® Grinding Machine
where the material is ground into a powder. During
the grinding stage, additional liquid nitrogen may
be injected into the Pulva-Sizer® to remove heat
caused by grinding.
When using the cryogenic conveyor, measurable and
repeatable results are obtained for lab or productions
calculations. Grinding mills range in size from 7-1/2
HP to 200 HP. With our cryogenic grinding unit an
understanding develops with interaction of equipment
components and operating parameters. Factors such
as consistent feed rate, precise temperature measurement,
mill operating parameters and pressure control are
critical to the evaluation of cryogenic grinding and
cryogenic grinding systems.
Testing is available in Pulva's
Testing Lab.
