1084 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
the floating roll via the bearing housing. The hydraulic sys-
tem is equipped with nitrogen accumulators which mimic
the behavior of a spring system. Depending on the ratio
between the initial nitrogen pressure and the hydraulic
pressure, the stiffness of this hydro-pneumatic system can
be set (Mähler 1999, Klymowksy 2002). This influences
the change in pressure with respect to the operating gap
of the rollers. Simplified examples of soft and hard spring
curves can be seen in Figure 2.
The roller surface is specially designed dependent upon
the use case and material properties. For traditional bri-
quetting presses, molds are used to form material into the
desired shape. In the case of roller compaction, specific roller
profiling promotes better de-aeration of the feed material.
For high-pressure grinding rolls used in comminution,
wear protection is the main priority. For this, different
approaches are available. Traditionally, wear resistant tyres
or hard-facing techniques are used when dealing with abra-
sive materials. The state of the art for today’s machines is
semi-autogenous wear protection consisting of tungsten
carbide containing pins, often referred to as studs, or by
using hexagonal tiles (Oberheuser 1996, Hanstein 2002).
In the space between these pins or tiles, compacted material
will accumulate and protect the roller surface. The input
material is fed via gravity or screw feeders to the variable
gap between the rollers. The products can be either flakes,
loose material or briquettes.
The specific compaction process is not only dependent
on machine parameters such as the compacting pressure or
the roller speed, but also relies on process conditions and
material properties (Zisselmar 1987). Such conditions/
properties are particle size and shape, bulk density, water
content and temperature, and lastly, the material hard-
ness or plasticity (Lupin 1983, Zisselmar 1987, Knobloch
1988).
While the material is compressed within the working
gap, there is a certain pressure profile both in the angu-
lar and axial direction. Examples are displayed graphically
in Figure 3 and Figure 4. The angular pressure profile has
been described in various works. For example, roller com-
paction processes were studied by Johanson (1965) and
comminution by Schönert (1985). As for the axial pressure
profile, the fundamentals were researched in experiments
by Anderson (1990) or Lubjuhn (1992), while Heinicke
(2013) introduces a model for describing the product fine-
ness along the axial profile.
To ensure optimal operation of both the roller press
and its effects on downstream processes and equipment,
measurement of several process variables is typical, and in
Figure 2. Examples of a hard and soft hydro-pneumatic
spring curve
Figure 3. Schematic angular pressure profile after Vinogradov and angles after Schönert
the floating roll via the bearing housing. The hydraulic sys-
tem is equipped with nitrogen accumulators which mimic
the behavior of a spring system. Depending on the ratio
between the initial nitrogen pressure and the hydraulic
pressure, the stiffness of this hydro-pneumatic system can
be set (Mähler 1999, Klymowksy 2002). This influences
the change in pressure with respect to the operating gap
of the rollers. Simplified examples of soft and hard spring
curves can be seen in Figure 2.
The roller surface is specially designed dependent upon
the use case and material properties. For traditional bri-
quetting presses, molds are used to form material into the
desired shape. In the case of roller compaction, specific roller
profiling promotes better de-aeration of the feed material.
For high-pressure grinding rolls used in comminution,
wear protection is the main priority. For this, different
approaches are available. Traditionally, wear resistant tyres
or hard-facing techniques are used when dealing with abra-
sive materials. The state of the art for today’s machines is
semi-autogenous wear protection consisting of tungsten
carbide containing pins, often referred to as studs, or by
using hexagonal tiles (Oberheuser 1996, Hanstein 2002).
In the space between these pins or tiles, compacted material
will accumulate and protect the roller surface. The input
material is fed via gravity or screw feeders to the variable
gap between the rollers. The products can be either flakes,
loose material or briquettes.
The specific compaction process is not only dependent
on machine parameters such as the compacting pressure or
the roller speed, but also relies on process conditions and
material properties (Zisselmar 1987). Such conditions/
properties are particle size and shape, bulk density, water
content and temperature, and lastly, the material hard-
ness or plasticity (Lupin 1983, Zisselmar 1987, Knobloch
1988).
While the material is compressed within the working
gap, there is a certain pressure profile both in the angu-
lar and axial direction. Examples are displayed graphically
in Figure 3 and Figure 4. The angular pressure profile has
been described in various works. For example, roller com-
paction processes were studied by Johanson (1965) and
comminution by Schönert (1985). As for the axial pressure
profile, the fundamentals were researched in experiments
by Anderson (1990) or Lubjuhn (1992), while Heinicke
(2013) introduces a model for describing the product fine-
ness along the axial profile.
To ensure optimal operation of both the roller press
and its effects on downstream processes and equipment,
measurement of several process variables is typical, and in
Figure 2. Examples of a hard and soft hydro-pneumatic
spring curve
Figure 3. Schematic angular pressure profile after Vinogradov and angles after Schönert