Energy consumption during the production of a vehicle. The paint
shop is the most energy-intensive area.
Society must find ways to decrease energy consumption. One
way that is already feasible is the increasing use of regenerative
energies, including the efficient handling of them and of our resources. Dürr is committed to this, not only with the concept of
their new campus in Bietigheim-Bissingen, where about two
thousand fewer tons of CO2 are emitted annually by the use of
regenerative energies and by high energy efficiency, but particularly by the concept of the Green Paintshop. A benefit for the operator of these technologies is a clear cost reduction.
Before we undertake a tour of Dürr’s Green Paintshop, let’s
take a look at the painting process. The trend today goes towards
so-called shortened, lean processes in which individual process
steps are eliminated. With primerless painting processes, which
are mostly based on waterborne paint technology, the base coat
must take over the primer properties. The special feature of the
three-wet process, where increasingly high-solid paint systems
are used, is that all three paint coats are applied in one painting
line, wet in wet, that is, without intermediate drying. With both
processes, the separate primer painting line, as well as the subsequent dryer, are omitted. The advantages include compact installations, reduced investment and operating costs and a more
positive ecological balance.
The Green Paintshop
The Green Paintshop is an energy-optimized and resource-sav-ing paintshop. It includes more than twenty computer-oriented
measures, which are combined to a sustainable overall concept.
This article will only concentrate on some of the most important systems.
Every painting process begins with the pretreatment and the
following dip-coating. Here the rotation procedure has prevailed.
For different requirements on system capacity and flexibility, the
RoDip family has available a mechanical version, RoDip M and
an electric version, RoDip E. With the RoDip technology, especially space-saving layouts can be realized. The missing inlet and
outlet slopes, however, not only shorten the installation length,
but also reduce the tank volumes. This is combined with lower
material and energy costs, the latter are about thirty-five percent
lower compared with the conventional shuttle. Based on these
advantages and a smaller wastewater amount due to the rotation, a unit cost savings of almost sixteen percent per body is the
result in a sample calculation for an installation with an annual
throughput of 300,000 bodies. This doesn’t take into account
the better quality due to minimization of soiling, runners and
drips. More than 20 million car bodies have already been painted
with RoDip.
Let us still stay briefly with the pretreatment. With the multi-cyclone filtration system by Dürr, solid matter particles are removed especially effectively and efficiently from the degreasing
and purging baths. In comparison with conventional filter systems, an energy saving of more than thirty percent is achieved.
The tour now leads to the painting lines and the spraying
processes. The supply and exhaust air operation in the spraying
booths is state of the art. A majority of the energy that is used in
a paintshop is needed for the necessary air preparation, indeed
just less than sixty percent. Recirculation of the booth air would
save a considerable part of this energy. A clearly improved efficiency of the overspray scrubbing as compared with the wet
scrubber and no humidity increase as it occurs during the wet
washout is a pre-condition for that.
Here, Dürr breaks new ground with the EcoDryScrubber.
EcoDryScrubber is based on the principle of dry scrubbing
with the aid of limestone powder as a binding agent for the
paint particles. The particle-loaded booth air is guided through
filter modules on whose surface the solid matter is separated
and the air can be recycled into the painting process through
the supply air installation where a small part of fresh air is
added. The fresh air part that is between five and at the most
20 percent, leads in a simple way to constant booth conditions
and it does so widely independently of the exterior climate.
The saturated limestone powder is automatically replaced by
fresh powder depending on the degree of saturation, and can
be used in other manufacturing processes in an untreated state.
In other words: with this new technology there are no paint
sludge accumulations that have to be disposed of as hazardous
waste, no wastewater is to be treated and no chemicals are necessary for coagulation. If one considers the energy balance of
the entire paintshop, 30 percent of the total energy can be
saved by the use of dry scrubbing, related to the painting booth
the savings is 60 percent. The city with 50,000 inhabitants
mentioned at the beginning now shrinks to about 34,000 thousand energy consumers.
The advantages that are only briefly outlined here have already convinced many customers worldwide. Since the introduction of this technology, Dürr has already received orders for
30 lines.
Also, the actual paint application offers numerous possibilities for more efficiency and resource saving, especially important
if one considers the great portion of material costs in the total
cost of vehicle painting. For instance, with innovative color
change systems, the color change losses can be reduced to an absolute minimum. Expressed in numbers, in one color change
about 45 milliliters of paint are lost per atomizer. That is already
a relatively good default value. With the EcoLCC innovative
color change system, this value can be reduced to ten milliliters.
Here a large part of the paint material which otherwise must be
