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Hosokawa Alpine has been
supplying toner systems in a great variety of different designs
to every renowned toner manufacturer around the world for over
20 years. Our engineering services also include turnkey delivery
of complete toner systems.
In the case of off-line mode, which many of our customers prefer,
the material is filled into containers after each process step,
which then serve as feed bins for the next process step. Some
system components can be cleaned or maintained while other components
are in use. Each process step can be individually optimised.
Preparation, weighing, preliminary mixing:
The individual components are prepared, weighed and then filled
into high-speed preliminary mixers for pre-mixing.
The pre-mixed raw materials are metered to an extruder. The
pasty toner mass is discharged from the extruder into a cooling
unit with downstream nibbler.
Dependent on the grindability and the wear behaviour of the
material, the following Hosokawa Alpine mills can be used:
Rotoplex
granulator
Fine
impact mill UPZ
Sieving mill
The advantage of the UPZ fine impact mill is its high endurance
against wear and that this process step can be in pressure-shock-proof
design. Preground to granules, the material is collected in
a cyclone or filter and then filled into a container.
A vibrating table empties the preground granules out of the
container. The toner is now metered via a flap valve to the
opposed jet mill. Dependent on the grindability of the different
toner types, either Laval or particularly efficient megajet
nozzles are employed. The level of material in the mill is monitored
and regulated by load cells. If necessary, the metering unit
is adjusted accordingly. The ground material is conveyed further
to a cyclone and then either discharged into a container or
– upon request – direct into the downstream classifier.
The classifier can either be fed from a container or from the
cyclone of the fine grinding step. The problem specification
dictates which of the two specially developed toner classifiers,
i.e. TSP or TTSP, is employed. A specially designed flap valve
serves as the air seal for the coarse material discharge. The
fines are collected either in a cyclone or a filter. The advantage
of off-line mode is that the classifier can be operated and
optimised independent of the mill.
In order to improve the flow behaviour and to influence the
surface properties, the toner is coated with different additives.
The container with the coarse material from the classifier then
becomes the feed bin. Both toner and additives are metered by
gravity into a high-speed fluid mixer, after which the blended
material is either refilled into a container or fed to a screening
machine via an intermediate bin.
Any flakes still remaining in the product are removed here.
In most cases, a tumbler screening machine with a screen mesh
width of 125 µm is used. The coarse material is waste
and the fine material is the finished toner, which is filled
via airtight devices into containers or drums positioned on
floor scales.
The finished toner is then filled into crates or is sold direct
in bulk.
Here too, Hosokawa Alpine has lots of experience and a great
variety of solutions.
Toner is a material which is prone to dust explosions. Because
of this, special measures must be taken. The following concepts
are in use:
Pressure venting
Explosion suppression
Pressure-shock-proof design
Provided all relevant system sections are in pressure-shock-proof
design, there are very few restrictions regarding system set-up,
and the maintenance costs can also be minimised. All valves
and material locks are designed to be pressure-shock-proof to
10 bar overpressure and are flame-propagation-proof, so that
the maximum explosion pressure which can develop in the system
is containable. In the worst case, system components might deform,
but they will not rupture or burst. This is synonymous with
a high degree of safety for the system user and operator.
These days, switching systems with visualisation options are
extremely popular. Individual process steps, flowcharts and
actual values are represented graphically on PCs, and the operating
status can be monitored and retrieved at any time. All error
messages are registered and can also be printed out at any time.
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