Green Paintshop

By Dr. Ing Pavel Svejda, Du00fcrr Systems GmbH | June 9, 2011

A Contribution to More Energy Efficiency and Resource Saving in Automobile Painting

Efficiency and sustainability, these are the great trends of our time. Natural resources are restricted, and rapidly increasing energy demand, particularly in the growth markets of the newly industrialized countries, pose great challenges for national economies. In recent times, vehicles have been rated according to their CO2 output rather than their fuel consumption. In order to lower this, new drive concepts have been developed that go as far as electro-mobility. In vehicle manufacturing as well, solutions are in demand that lower energy consumption and thus the CO2 emissions, and handle available resources carefully. With its Green Paintshop concept, Dürr Systems GmbH provides an integrated solution package for maximum energy and resource efficiency in automobile painting.

In the course of its life, a vehicle emits on average twenty-one tons of carbon dioxide, which contribute to the greenhouse effect. About twenty percent of this is already released during production. Seventy percent of the energy needed for production is used in the paintshop. This is the same amount that is consumed in a city with fifty thousand inhabitants. 

Worldwide energy consumption is increasing rapidly. Among the ten largest consumers, Germany ranks in seventh place, and all four BRIC states (Brazil, Russia, India, China) are included. For the first time, China overtook the U.S. as the largest energy consumer. A Chinese person, however, uses less energy than individuals in western countries. Specifically, the typical Chinese person uses a fifth of what an American needs and forty percent of the consumption typical in Western Europe. What happens, however, if the average Chinese person increases his energy consumption to western levels?

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-saving 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 multicyclone 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 purged and rejected is used for painting. A further reduction of the color change loss can be achieved by the use of the EcoBell2 ICC. ICC stands for “integrated color changer” and it means that the color changer is built-in directly in the atomizer for a maximum of six high-runner colors. The paint loss here is as little as four milliliters. Less is not possible.

A further innovation in the field of application technology is the new EcoBell3. With this rotating atomizer it is now possible for the first time to design the exterior charge so compactly that the interior painting of vehicles is possible with it. The great advantage of this is an essential reduction of the complexity of the application system with waterborne paint. Voltage block systems can now be renounced. The EcoBell3 offers even more, resulting in exterior and interior painting with the same atomizer, and in this way, new possibilities in the layout of painting installations. This gives easy, continuous painting without the interruption frequently necessary with voltage block systems for the “refilling” of the atomizer, important in particular in bumper painting—and of course clearly higher atomizer performance. In connection with the lean color changer EcoLCC and with the new, very compact series nine paint dosing pump, the EcoBell3 offers such an extremely efficient and compact application system for all applications. 

Where can even larger energy volumes be saved in a paintshop? With the dryer technology and the corresponding exhaust cleaning. The compact design of the dryer with an asymmetrically designed stop zone, integrated air management and heat recovery in connection with the new, optimized Tarcom V burner technology by Dürr result in another 15 percent. The Tarcom V burner is designed so that existing installations can be retrofitted, and this fundamentally applies to all systems.

It is not sufficient to develop power-saving and environmentally safe technology as it must also be operated correctly. For this, Dürr expanded their process control system EcoEMOS by an interesting component—the software module EcoEMOS Energy. This tool facilitates the systematic recording and evaluation of consumption values. For instance, individual consumption places can be optimized, and superfluous ones can be identified and eliminated. In combination with the working time model saved in EcoEMOS, a systematic and automated reduction of consumers in production-free times can be realized. With this new module, Dürr with their long-standing experience offer very practical possibilities for the energy-conscious and environmentally friendly system operation in an energy-intensive environment. 

With new painting installations, so-called greenfield projects, a conclusive concept saving energy and resources is certainly easier to realize. Old installations in particular, however, also offer very great optimization potentials when looking more closely. For this, Dürr offers an assessment that is carried out by designated experts with a long-standing experience and extensive process know-how. The investigations may be adjusted to the most different aspects. According to customer preference, attention is focused on energy and material efficiency, on capacity adaptations, on increase in availability, on optimum conversion of legal specifications or on quality improvement. This way, an existing painting installation can be made fit again with a manageable investment.

A paintshop is an energy-intensive production area. With the Green Paintshop, Dürr offers a concept that enables an efficient and environmentally friendly operation of the installation. As a positive side effect, considerable costs can be saved, a two-digit million amount, calculated over the model cycle time of seven years in a paintshop with a 150,000 units per annum. There is no reason to hesitate with the conversion. 


Dürr Builds Energy-efficient Green Paintshop with Integrated Paint Process for BMW

In recent news, Dürr inked a deal to construct its Green Paintshop for the BMW Brilliance Automotive Ltd. joint venture in Shenyang, China. The automobile paintshop incorporates Dürr's latest technologies and is to consume less than 500 kilowatt-hours of energy per car body. That is a third of the level customary ten years ago.
BMW Brilliance intends to build an environment-friendly automobile paintshop in Shenyang. Among other things, the plant will use the EcoDryScrubber spray booth system, which enables energy consumption per booth to be reduced by up to 60 percent. At the base paint stage, the RoDip M rotary dip-coating process saves energy and chemicals through shorter tanks. Another "green" feature is the so-called Integrated Paint Process, which dispenses with the filler coat application and subsequent drying phase. Thirty-two Dürr painting robots are being installed for automated paint application. They are equipped with the latest atomizer generation EcoBell3 and the EcoLCC color changer. This product combination minimizes paint loss on color changes and shortens the painting process. Other measures for conserving resources include heat recovery through heat wheels, waste-heat boilers and the use of a special membrane for reducing water consumption.