In the past, industrial painting was often seen as a straightforward production step: it used raw materials and energy, discharged liquid and gaseous effluents and generated process waste, with limited attention to the overall impact of the coating line.
Today, everyone involved in painting and coating processes has to take environmental impact into account, remembering that energy resources and raw materials must be used as efficiently as possible. Emissions and process residues must also be substantially reduced.
All of this falls under the concept of “best technique” (or best available technique) which, in the paint shop, should be implemented by adopting innovative technologies that help reduce:
- energy demand
- paint consumption
- solvent consumption
- water consumption
- particulate emissions
- wastewater and effluents to be treated
Sector studies show, for example, that a large painting department in the automotive industry can consume, in a single year, as much energy as a town of around 50,000 inhabitants. From this perspective, it becomes essential – even for subcontractors or companies that paint in-house – to keep up to date with the best available technologies.
A few examples: particular attention must be paid to the choice of spraying equipment, which should ensure the lowest possible product consumption and the lowest overspray generation, for the same dry film thickness, thanks to a high transfer efficiency of the coating to the workpiece. The range of equipment for applying liquid coatings goes from simple spray guns (with a transfer efficiency of around 30–40%) to sophisticated electrostatic rotary atomizers (with transfer efficiencies above 90%).
The choice of spray booth also requires careful evaluation, considering the operating costs of a dry booth compared with a wet booth.
A booth with a water-wash removal system will have a higher energy consumption than a dry booth, if only because of the pump motor that recirculates the water over the curtain and the motor of the sludge removal system.
Salvatore Rampinelli