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Waterbased cleaning of mixing vessels 1. Introduction
In the production and use of solvent-borne paints and coatings, substantial quantities of VOCs are emitted to the surroundings. Therefore, for environmental protection, measures must be implemented to reduce these emissions. The best and most practical measure for reducing VOC emissions is substitution by alternative and less critical solvents. In this connection, water-borne paints and coatings are gaining in importance. Where substitution of organic solvents is not possible, as a further measure reduction of the proportion of organic solvents in the products may be considered, such as the development of so-called "high solids" coatings. Nevertheless, for certain applications currently no substitution possibilities for organic solvents are foreseeable. For this reason, over both the short and medium terms, solvent-borne products will continue to be used. When manufacturing solvent-borne paints and coatings, VOCs are emitted at various points of the production process. Prior to constructing costly air pollution purification plants, measures for reducing the emissions of VOCs as well as for reducing the volumetric flow should be implemented. Apart from these purely economic considerations, regarding the implementation of emission reduction measures, also other criteria like practicability (no negative effects on operation, access, etc.), ecology (abatement of solvent emissions), safety, and so on have to be taken into account. To give manufacturers of solvent-borne paints and coatings a basis for coming to a decision on new investments in production facilities and/or pollution abatement technology, the Danish Paintmakers’ Association has initiated in the project:
with one report concerned with "VOC emissions from manufacturing processes" and another report with "Water-based cleaning of mixing vessels and equipment". The general aim of the project is to qualify the individual companies within the industry to handle an additional product liability and at the same time to implement technology in the manufacturing phase that is actually cleaner. The results of "VOC emissions from manufacturing processes" are described in a separate study. The study deals with measures for preventing or reducing solvent-containing emissions. In this report "Water-based cleaning of mixing vessels and equipment"- the focus will be on the possibilities of using water-based cleaning of mixing vessels and equipment, and to provide companies with a sound basis when confronted with new investments in cleaner water-based technology. This will benefit both the general environment and the working environment. Both reports are available on the Internet - www.mst.dk - homepage of the Danish EPA (Danish versions) and on – www.fdlf.dk - homepage of the Danish Paintmakers’ Association (English versions). The project period was from January 1999 to February 2000. The project has been carried out by Fichtner · Carl Bro a|s, with the participation of representatives from the company Teknos Technology A/S. Laboratory and full-scale tests were conducted by two suppliers of cleaning technology, Renzmann, Germany, and Riobeer, Switzerland. 1.1 Description of problemThe application and release, of volatile organic compounds can, due to their properties, cause harm to human health and/or contribute to local or trans-boundary formation of photochemical oxidants in the boundary layers of the troposphere, leading to environmental degradation. To prevent, or mitigate, emissions of volatile organic compounds over the long term, in March 1999 the European Union issued Directive 1999/13/EC of the Commission on the Limitation of Emissions of Volatile Organic Compounds, referred to in the following as the VOC Directive. This requires registration of all plants or plant components covered by this Directive. Furthermore, their operators must initiate measures, within the stated transition periods and as far as necessary, to prevent or reduce VOC emissions. VOC emissions from cleaning mobile mixing vessels and equipment are estimated to amount to 25-30% of the total VOC emissions from the production of solvent-borne paint /Appendix B/. The total VOC emissions from the Danish paint and coating production are estimated as approx. 450 tons per year /Appendix B/. It might be possible to abate emissions of VOC by an amount of some 110 tons per year by changing to water-based cleaning of the mixing vessels and equipment. The purpose of this study The purpose of this study is to verify the possibility of water-based cleaning (e.g. water and detergents) of mobile mixing vessels. Based on the know-how of manufacturers and suppliers in implementing and operating water-based cleaning technology and based on laboratory tests and full-scale tests, the technology has to be evaluated to determine whether it would be practicable to scale it up for installation in factories dealing with similar products and raw materials. Furthermore, the environmental impact and costs for implementation and operation have to be described. Laboratory tests and full-scale tests are carried out with Teknos Technology A/S products. |