For many years, dry abrasive blast-cleaning has been the most widely used surface preparation technique, particularly within the ship-building and repairing industry. This method (often called sand-blasting) is based on the propulsion of an abrasive material against the cleaning surface, through a high-speed stream of compressed air. Recently, such blast cleaning methods have been brought into question because of their negative environmental impact. This has been caused mainly by the abrasive material utilized (sand). The strict environmental regulations brought in as a result, have restricted or made uneconomical such open-air blasting operations throughout Greece and the rest of the EU. In recent years, a great number of international industrial research projects have been developed to reduce or eliminate this environmental impact, involving developing alternative abrasives ( olivine, garnet, steel grit etc) and new surface preparation methods (eg. Ultra High Pressure water-jetting, water blast-cleaning, vacuum blasting etc.). However, it is currently not easy to discover how widely these methods are being used within Greece, the degree of their technical or economic viability, nor the extent of their environmental impact. A partnership consortium was therefore set up to promote the investigation of the parameters of these question, and to promote new environmentally-friendly blast-cleaning techniques. This represented an important public/private collaboration between the National Technical University of Athens (NTUA) in their Laboratory of Mining Technology (LMT), an industrial partner (Neorion Shipyard), and backed by the Department of Mineral Enrichment Technology of the Institute of Geology and Mineral Exploitation (IGME).
The principal aim of the project was the transfer and application of the results of the applied research of NTUA, concerning alternative, environmentally friendly blast-cleaning techniques, in the ship-building industry. The main results anticipated were a significant reduction of the environmental impact of open-air abrasive blast-cleaning, an improvement of work conditions, and an increase of productivity and work quality. This would be achieved through three action lines: 1) The definition of the current state of play of blast-cleaning operations in Greece, especially focusing on the technical and economic viability together with the environmental impact. 2) The examination of the alternatives available, using current research from the NTUA 3) Promotion of the application of new surface preparation methods as part of a sustainable development of the Syros area. At all stages, the project was concerned to promote “ stable balanced “solutions, meeting both the requirements of environmental sustainability and technical/economic feasibility.
The main conclusions of the project were that although current blast-cleaning operations in use within Greece did not currently pose an environmental threat, the application of alternative methods could reduce the dependency on certain abrasives and limit further the environmental consequences in a more cost-effective way. The project used a wide range of research methods and tools to establish the current situation and to appraise alternatives, including market research, mathematic prediction models and the development of alternatives on three scales – laboratory, pilot-plant and industrial scale. The main findings from the first two stages were:
- The dominant blast-cleaning abrasive used in Greece was nickel slag (over 95% of the demand), leading to a worrying dependency on one material.
- This nickel slag and its waste, produced acceptably low levels of leachable metals (nickel and manganese), but needed more effective management in their disposal.
- Dust concentrations were found to be below the accepted minimum ( eg lead concentration was found to be 40 times lower) On the question of alternatives, although there did not appear to be one optimum (both environmentally-friendly and technically effective),surface preparation method, some alternatives could make a difference:
- The addition of a dust suppressant to the above process, produced 30% reduction in dust pollution.
- The water-blasting technique developed by Neorion shipyards produced a 60-95% reduction.
- UHP water-jetting produced no dust and minimized solid waste.
- Xanthi garnet could be an effective abrasive alternative.
Some of the results of the investigation were taken up and applied immediately by the industrial partner Neorion shipyards. This meant that a direct environmental impact was achieved through the introduction of the two most promising alternative methods (water blast-cleaning and UHP water-jetting), backed by a sophisticated wastewater management system which ensured zero environmental impact. The application of the GIS based model developed by NTUA, further enabled the company to monitor and control the shipyards emissions produced by the blast-cleaning operations. On a more general level, no environmental benefits were achieved immediately, but it was expected that with the changing industrial climate and stricter EU regulations, environmental management systems of this type would start to be introduced more widely, at regional, sectorial and State national level.