Eisenmann
Subtitle: Environmental friendly, sustainable & economical solutions
As everyone knows, China faces huge problems with air pollutions and it´s a major goal of the government to reduce them sustainably.
Hence the government respectively the Environmental Protection Bureaus released Emission Standards for VOC.
The limitation for VOC Emission differs from province to province. In general we see, that in areas with very high pollution the limits are more stronger.
Beside limits for VOC-concentration, there are also limits for the mass of VOC per hour, means e.g. for huge exhaust air volumes the VOC-concentration could be even lower than what is requested in the Emission Standards.
EISENMANN strongly recommends, that the focus for VOC-elimination
should be shifted from so called “end-of-pipe technologies”-Thinking to
Production Integrated Environmental Protection.
This helps very much to find a sustainable balance between ecological and economical requirements in the long term, see figure 1
Figure 1: Optimization finances renewal
The question is now: “How do we achieve that?”
Knowing that,Effectivity x Efficiency = Ultra Efficiency
we need to have a paradigm change in the production.
New technologies lead to a massive reduction of resource consumption.
New recycling methods help to avoid Scrap, Waste and Emissions.
What is meant with Production Integrated Environmental Protection?
The following options should be considered to avoid respectively reduce VOC-emissions:
- Check whether, liquid paint can be substituted by using powder paint
- Change from solvent-borne to water-borne paints-systems
- Usage of high solid paints
- Install high efficient application systems(E-static etc.) to increase the efficiency and to minimize overspray
- Integrate air recycling systems in the paint booth areas, in order to minimize the exhaust air volume, which has to be treated
- Don't spray solvents from color change resp. cleaning operations into the spray booth, collect them and think about recycling via distillation
In the following two examples are described, how the above mentioned theoretical approach looks in practice
Automotive subsupplier:
Basis: Customer requests two painting lines with overhead-conveyor(OHC) after existing Zinc-Phosphating Pretreatment due to the need that 10-20% of the produced parts have to be painted several times to fulfill the quality requirements.
This concept has some disadvantages, e.g. higher footprint, one curing oven is mostly standby (waste of energy), two paint-booths create higher exhaust air volume which has to be treated.
The “Ultra Efficiency”-Concept of EISENMANN switches to one multipurpose painting line with Power+Free-Conveyor(P+F).
The advantages of this concept are:
- P+F-solution is more flexible, especially for future production extension or relocation of loading/unloading areas and allows to create storage areas
- Footprint(layout with one painting line) is much smaller
- Higher Quality of painted parts(particularly using waterborne paint), because the parts will be touched only once (at loading) during the whole painting process, compared to the basis request, where the parts must be switched manually from one OHC to the other OHC.
- Operating costs for one painting line are significantly less, because of less energy consumption(only one paint curing oven)
- this results also in a smaller Carbon(CO2)-footprint which is more environmental friendly
- Maintenance costs are also significantly less for one painting line with P+F
- Exhaust air purification with ADW and TO(see figure 2) for one painting line results in a smaller volume, which leads to a more effective treatment with
- less consumption of primary energy(natural gas) and smaller CO2-footprint
- Waste heat of TO will be used to heat ovens(water dry-off resp. paint curing)
- Heat recovery means less energy consumption, thus less Carbon footprint
- Dry separation of overspray from paint-booth compared to wet system leads to less operating costs for the exhaust air treatment, because of no need to de-humidify the exhaust before treatment in ADW(see a previous article “E|Cube: Innovative system for dry overspray removal” in this magazine from March 2015)
VOC from the exhaust air of the spray-booth will be eliminated through an adsorption process on zeolite material(Adsorption Wheel = ADW). The regeneration of the ADW is done with hot air, generated out of the TO via a desorption air heat exchanger. Highly concentrated desorption air will be treated in the recuperative Thermal Oxidizer TO, see figure 2. To save energy, the desorption air will be preheated in a TO-internal heat exchanger.
Figure 2:Thermal Oxidizer with heat recovery for treatment of desorption air from ADW
Automotive Paint-Shop
Basis: For a new automotive paint-shop the local EPA requires, that the exhaust air out of spray booth has to be treated with a combination of Adsorption Wheel ADW (concentrator) and Thermal Oxidizer TO. The removal efficiency for the adsorption process should be >90%, for the TO higher than 97%.
To fulfill the requirement for the TO is not a big challenge. EISENMANN Thermal Oxidizer operate for such case with a removal efficiency of higher than 99%.
Nevertheless the company requests a more strong removal efficiency of 95% for VOC of exhaust from spray-booth, because they think, looking forward helps them to be prepared for possibly future demands.
A comparison of the two different requirements (90% versus 95% removal efficiency) show the impact for the economy respectively for the ecology.
EISENMANN already considered in the design of the paint-shop a reuse of exhaust air from the manual zones and forwarded them in a so called “cascade-system” to the automatic zones. This measure reduces the exhaust which has to be treated by approximately 65%. A further advantage of this is, that the VOC-concentration before treatment in the ADW, see figure 3, is getting even higher and this results in less energy consumption for the thermal treatment of VOC finally.
Figure 3: Filter/Air Conditioner Unit and Adsorption Wheel ADW
To design the ADW, we look at the exhaust VOC-concentration and to limits after treatment, given by the local authorities.
In case a removal efficiency for the spray booth exhaust is requested e.g. 95%,
means for an inlet concentration of 270mgVOC/m³ that the VOC after ADW has to be less than 13mgVOC/m³, compared to the local EPA defined figure of 27mgVOC/m³ (equal with 90% removal efficiency) !
This results firstly in higher investment costs, because the configuration of the adsorption process has to be enlarged and the size of the TO, incinerates the desorption air, has also to be increased.
Secondly the operating costs – more natural gas is needed - are significantly higher. Hence the Carbon(CO2) footprint of the paint-shop will increase proportionate.
Figure 4 shows the comparison between the proposed EISENMANN-solution to meet the local VOC-limits and the customer request for a 95% removal efficiency for exhausts from spray-booths.
As you can see in figure 4, the savings for natural gas consumption are approximately 350.000 Nm³/year respectively 1.500.000 CNY/year.
The CO2-emission(greenhouse gas) will be therefore reduced by approximately 92% !
Figure 4: Comparison between the proposed EISENMANN-solution to meet the local VOC-limits and the customer request for a 95% removal efficiency for exhausts from spray-booths.
EISENMANN is always focusing to install the most ecological and economical solution, with lowest operation costs for the customer, considering the national and local emission standards.
Keeping the above described comparison in mind, the recommendation for the solution with 90% removal efficiency is natural, because it is more environmental friendly and even more economical.
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