Processing Pigments and Dyestuffs
A distinction is made between organic and inorganic pigments
and dyestuffs, and these in turn can be broken down into natural
and synthetic materials. In view of the fact that each product
is different, especially with regard to the individual coating
behaviour, Hosokawa Alpine offers its comminution, classifying
and sieving machines in a great variety of special designs.
|
The following
text details three examples of processing systems that
were laid out and delivered to meet the individual problem
specifications. The type of grinding mill and classifier
mill selected was based in each case on the characteristic
properties of the pigment, i.e. the coating behaviour
and hazard class, etc. |
a) System with Alpine fine impact mill UPZ
UPZ in pressure-shock-proof design to 10 bar overpressure. End-product
fineness range: d97
< 10 µm - 500 µm, dependent on the grindability
of the product and the choice of grinding elements (pin discs,
plate beaters with grinding track, sieve, etc.).
 |
1 = Feed screw
2 = Metal detector
3 = Silencer
4 = Explosion-venting valve
5 = Rotary valve
6 = Fine impact mill UPZ
7 = Aut. reverse jet filter
8 = Butterfly valve
9 = Fan
10 = Control cabinet
A = Feed product
B = End product |
b) System with Alpine Zirkoplex classifier mill ZPS
ZPS for sticky pigments in pressure-shock-proof design to 10
bar overpressure. End-product fineness range: d97
8 - 150 µm.
 |
This machine
is characterised by:
 |
Optimum accessibility and thus
simple cleaning |
|
Plug-in beaters |
|
Low speeds inside the mill
between the grinding zone and the classifying wheel,
and thus hardly any product contact with the walls |
|
Selection of materials (stainless
steels) |
|
Surface quality (roughness) |
|
Coating of critical parts with
teflon, for example |
|
Enlarged fines discharge (reduces
the exit speed) |
|
Special fluidisation unit at
critical points |
|
 |
1 = Silencer
2 = Rotary valve
3 = Metal detector
4 = Zirkoplex classifier mill ZPS
5 = Hydraulics
6 = Aut. reverse jet filter
7 = Explosion-venting valve
8 = Fan
9 = Butterfly valve
10 = Control cabinet
A = Feed product
B = End product |
c) System with Alpine fluidised bed opposed jet mill AFG
 |
The fluidised
bed opposed jet mill is suitable for processing hard and
abrasive pigments. This classifier mill permits the production
of extremely high fineness values at steep particle size
distributions and top size limitation. End product fineness
range: d97 2 -150 µm. |
The flow chart below shows the process
sequence of a processing system in pressure-shock-proof design
to 10 bar overpressure for organic pigments. End product fineness:
< 3 µm. The system was laid out to conform with the
94/9/EC (ATEX) Directive, and the flow chart shows how the system
is divided into different danger zones.
 |
Legend
1 = Feed metering screw with feed bin and shut-off valve
2 = Fluidised bed opposed jet mill AFG
3 = Automatic reverse jet filter with bin and fluidisation
unit
3.1 = Filter head
4 = Rotary valve
5 = Explosion-protection valve
6 = Safety filter
7 = Fan
8 = Packing machine
9 = Control cabinet |
The feed and discharge zones
(pos. 1 and 8) are both located in Zone 21, i.e. a zone in
which it can be expected that a potentially explosive atmosphere
in the form of a cloud of combustible dust in air arises occasionally
during normal operation, and if this is the case, only briefly.
The areas affected here are also those areas surrounding system
components from which dust can leak out and where dust deposits
can build up.
The AFG classifier mill (pos. 2) with filter up to the head
plate and including filter bin with fluidisation unit, rotary
valve and the associated ductwork is assigned to Zone 20.
This is a zone in which a potentially explosive atmosphere
in the form of a cloud of combustible dust in air is present
constantly or over long periods or frequently.
The filter top section, explosion-protection valve, safety
filter and fan including the ductwork (pos. 3.1, 5, 6 and
7) are assigned to Zone 22. This is a zone in which it is
not expected that a potentially explosive atmosphere in the
form of a cloud of combustible dust in air arises in normal
operation, and if it does so, then only briefly.
The zone divisions refer to the inside of the mill and system
accessories. The entire area surrounding the system at a distance
of 1.5 metres from the individual components is assigned to
Zone 22.
|
