cpp - Process technology for the chemical industry 02.2018

cpp ACHEMA PERSPECTIVES
Picture: Thaletec
Static mixer with hollow mixing elements which can be tempered. The elements were made additively
and individually and then welded together
pressure-resistant pressure vessel was required in order to investi -
gate chemically aggressive, toxic and explosive mixtures. This vessel
needed to be cooled quickly and efficiently. Additive manufacturing
allows the pressure vessel and the cooling jacket to be integrally
designed. The low wall thicknesses which are vital for rapid heat
transfer are hence feasible. The pressure-bearing wall is very thin
and permits good heat transfer, yet the container can be loaded
with up to 300 bar at a medium temperature of 200 °C. It would
not be possible to manufacture the cooling jacket in the form of an
integrated spiral using conventional techniques. Production in one
piece also enables the vessel to be made available promptly and
adapted easily to individual customer requirements. Furthermore,
the surfaces in contact with the product are rendered chemically
resistant with a glass lining.
What are the benefits of the additive process for the production of
gassing nozzles?
Dr. Reinemuth: The fact that gassing in the new solution is initiated
by a deliberately porous printed structure in the liquid flow is particularly
noteworthy. In order to gain the maximum advantage from
additive manufacturing, the conventional design template was analysed
with regard to its technical functions. A functionally integrated
one-piece solution which can be manufactured additively
was then designed on this basis. In contrast to the conventional
mixing nozzle, the additively manufactured version is also selfpriming.
The manufacturing costs were reduced to just 27 % compared
to the original, conventional solution, which was systematically
revamped. Instead of twelve pieces, which must be mechanically
manufactured and assembled, the additively produced so -
lution consists of only a single component.
Can all 3D printed components be glass-lined?
Dr. Reinemuth: Since all these components are made of stainless
steel, they can basically all be glass-lined. 316L and 304 stainless
steels or Inconel 625 and 728, amongst others, are suitable for glass
lining. These are also typical materials for selective laser melting. The
example of the glass-lined high-pressure reactor shows how mod -
ern selective laser melting, in conjunction with the traditional
process of technical glass lining, can lead to innovative engineering
solutions: the glass lining of the high-pressure reactor surfaces in
contact with the product expands the field of chemically corrosive
applications at temperatures up to 230 °C, where the resistance of
the additively manufactured base material would not have been
adequate. The high-pressure reactor consists of a special metal alloy
which is suitable for glass lining and allows particularly thin, but
non-porous and non-diffusive, surfaces with a roughness of less
than 1 micron.
Are there any restrictions on the glass lining material?
Dr. Reinemuth: The technological properties of the glass linings are
adapted to the respective base materials. However, their chemical
resistance and thermal shock behaviour correspond to those of
Thaletec’s normal chemical glass linings. The high-pressure reactor
was glass-lined with Thaletec TPE 2000 pharma glass lining.
What alternative is there to glass lining?
Dr. Reinemuth: Thaletec has developed the new SiOCoat coating
system for components made from standard stainless steels such as
316L (1.4404) or 304 (1.4301). SiOCoat is an inorganic, amorphous
coating which, similar to a glass lining at up to 900 °C, is
merged with the additively produced base material to form a gasand
diffusion-tight layer of approximately 0.2 mm on the surface.
The coating can be either sprayed on or applied by dipping. The
SiOCoat layer is characterised by good chemical resistance to acids
and alkalis, thermal insulation properties and a high surface quality
with a roughness depth of less than 6 μm. Components coated with
SiOCoat can thus open up more applications for additively manufactured
components without needing to lay down special requirements
for the selection of the base material.
Are the 3D printed components already used in practical
applications?
Dr. Reinemuth: Yes, of course. The examples I referred to are just a
small selection of the components which are additively manufac -
tured by Thaletec and then either glass-lined or coated with
SiOCoat. The majority are covered by customer protection. The static
mixer, though, is a Thaletec product. We regularly receive enquiries
and orders to coat components. In many cases, we also redesign
those components together with Jurec in order to optimise them
for additive manufacturing.
Why are additive manufacturing processes not yet widely used?
30 cpp 02-2018