2006/07 | ARTICLE
Innovation with all aspects
Modular lacquer manufacturing follows a completely new concept
The basic procedures in the industry for lacquer and paint have not changed since the introduction of the silo technology about 50 years ago. A recent start-up of a high-tech production for lacquer and paint eventually will set new trends. The set-up is modular, does not need any silos and produces independent from the batch size.
Production of lacquer and paint can be considered as a conservative branch with a highly empiric factor in the chemical sector. Of course there are continuous improvements of the recipes, indivi-dually optimised processing steps and computer controlled modernisation.
A real and comprehensive innovation was not in sight for a long time. In May 2006 a new production line for auto-motive hydro fillers has started up in Klingenberg that proves that there are other possibilities: the modular production facility for lacquers and paint of the medium sized automotive lacquer producer Hemmelrath is based on a completely new concept for the production of lacquer and paint.
A capacious vision was the beginning of the development. What could and should be done for a different high-tech process.
Independence from batch size
The new production should be almost independent from the given batch size. For larger orders and volumes as demanded by customers from the car manufacturing industry, until today several smaller batches have to be combined. For larger batches a processing system is required that may handle such large volumes of product – on the other side, the same system should be capable to handle medium sized batches as well.
One special demand on the to-do-list was the use of a small space only while providing a high efficiency in the same time. The large silos nowadays used in the production of lacquer and paint do not only require a lot of space but as well a lot of energy and time: raw material has to be transported under pressure into the silos and the again transported form the silo to the processing system. The new system had to be designed without the use of any silos.
Children know it from Fischer building blocks, the same principle may be applied for processing systems: a modular system. Such a concept provides a much higher flexibility of the processing system, products with different consistency may be treated, and the individual modules are only in operation when they are required.
Another crucial point was the demand for a much higher effectiveness compared to the output of conventional production systems.
For a conventional dissolver system about 80% of the energy input is converted to heat - lost energy and contra productive as well. The fast turning disc of a dissolver produces a shear gradient in a high viscosity paste. As a result, particles in the product are des-agglomerated. Due to the heating up of the product, the viscosity rapidly decreases - the shear effect is reduced and not effective anymore.
Another problem – especially when producing water based paint – is the air that is being incorporated into the product during the dispersing process. As an additional step, this air again has to be removed from the product.
The newly designed modular production system for lacquer and paint should operate in a clean area and almost free of any disposal – the demand for a completely closed system. Almost no emissions for a better environment and protection for the workers, less disposal, less cleaning requirements – an all around clean solution was the aim. The focus of all these considerations was the required quality of the products for one of the most demanding customers of the manufacturer for paint: the automobile industry.
Broaden the horizon
To realise the catalogue of requirements it was necessary to go for completely new and unknown paths. One inspiration was given by another economic sector: the food production industry. In the production of food many similar production steps are being used, same as in the production for lacquer and paint. In comparison, their technical level is much higher. Why shouldn't one or the other solution in the food industry being used in the production for lacquer and paint?Thanks to these methods it was possible to replace the existing conventional semi-automatic pro-duction with dissolvers at Hemmelrath with a maximum capacity of 5 tons per batch and a production capacity of 7.000 tons per year and the time consuming silo dosing system and the standard grinding processes with an innovative production system. The new processing system provides a production volume of 5 to 40 tons per batch a reaches a production capacity of 20.000 tons per year. In the same time it requires only 50% of the energy.
Its secrets of success:
- Rotor-Stator dispersing techniques
- Jetstream mixing technology
- Dosing of liquid raw materials (slurries, coloured paste, semiproducts)
- Efficient grinding techniques
- Online silo emptying
- Handling of the process in a closed system
- SPS controlled service and maintenance
Instead of using the conventional dissolver the dispersing of the powdery raw material to be treated now is carried out by a main module of the system. Main component of this module is an ystral Conti-TDS dispersing unit (TDS = Transporting and Dissolving System) which works according to the principle of the rotor-stator-effect (Picture 2). The medium is axially inducted into a dispersing head diverted by 90° and then squeezed through the slots of the rotor. The rotor runs wit a very high speed of up to 3.600 rpm. The stationary stator as well is equipped with slots and the medium leaves the system through the same. During this passage, the medium is exposed to very high shear energy. With-in a few milliseconds, the inducted powder is wetted and completely dispersed. One ton of powder may be wetted in about 3 minutes. As this dispersing unit is a completely closed system, no air will be incorporated into the suspension.
When specifying the parameters, the problem was clear: such a dispersing unit with the required size and the given speed profile was not available on the market. A highly specialised company was given the order to develop such a large TDS module.
This new type now operates with a power of 250 kW, a pumping rate of 90 m³/h and a maximum energy input in milliseconds. Picture 3 shows such a module
A positive aspect of the disperser according to the rotor-stator principle: because of the high speed of the rotor, a vacuum is created in the dispersing chamber. The process module uses this vacuum to induct powders from a powder container respectively Big-Bags into the dispersing unit. The powder storage container is directly fed from the silo on a truck. With this technology, the load of a truck is unloaded and dispersed – in less time than needed for the conventional pumping of the powder into a silo only. Large manufacturers of dispersed lacquer and paint use about 50% of their investment volume for the silo technology. The new technology offers the miracle to supply the powder from silos on trucks without the use of storage silos on site.
Mixing with the Jetstream mixer
From the dispersing unit the dispersed and wetted powder reaches one of the two processing tanks with a volume of 30.000 litres each. Here as well no conventional technique is being used: instead of using a standard stirrer, a ystral Jetstream mixer is installed to homogenise the product.
The principle of a Jetstream mixer as well is based on a rotor-stator- principle: in this case, the stator has the form of a guiding pipe and surrounds a fast rotating three blade rotor which again creates a liquid stream (Picture 4). The guiding pipe directs the liquid stream directly to the bottom of the vessel and thus avoids that the contents in the vessel starts to rotate. At the bottom of the vessel, the liquid stream is separated and re-diverted to the outer wall and forms an upwards directed stream towards the surface of the liquid. When it reaches the surface, the medium again is drawn to the centre of the vessel and causes a complete circulation of the medium in the vessel and thus achieves an immediate and homogeneous distribution of the product. As the rotor rotates in the lower part of the vessel, the surface of the liquid remains calm, no Vortex builds up and no air is incorporate into the product that later on again has to be removed with a lot of energy. The unit works independent from the filling level in the vessel, for his reason small batches as well as large batches may be produced in the same system. The use of a Jetstream mixing system requires much less energy compared to conventional mixers.
Not only he processing unit is equipped with Jetstream mixers, all other mixing tanks, slurry and binder semi product modules are equipped with this technology (Picture 5). The Jetstream mixers are adjustable in speed and are equipped with drives up to 30 kW.
A bead mill breaks records
Main reason for the limit of production for the production system that started in 1999 was the use of conventional milling systems. Bead mills are the bottle necks of each production as they reach a capacity of about 1 ton per hour only. The technology of the bead mills again should be part of the new production system as an especially fine and effective grinding for automobile lacquer is required by the automobile industry. Target was to drastically increase the flow rate. Until this time there was no bead mill available for the treatment of lacquer with a flow rate that even came close to the required value. The solution again was the development of a special system. This bead mill now breaks all the records and currently it is the largest existing mill in the production of lacquer and paint.
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