| Cryogenic Paint Removal from Steel Structures Using Liquid Nitrogen | Italy | 1993 | Full scale |
MANUFACTURE OF FABRICATED METAL PRODUCTS # 22
Background
This case study was performed in February 1993. It illustrates a modified process of paint removal in a plant having treatment capacity of 2500 kg/hr of objects.
Cleaner Production Principle
Process modification
Cleaner Production Application
Conventional processes for paint removal utilize acid dripping or pyrolitic ovens and produce pollutants. This process for paint removal is based on liquid nitrogen's ability to quicken cooling. The differing rates at which the material of the structure and paint coat contract results in cracks in the paint. By means of mechanical action the paint coat is then removed. The resulting solid waste can be used for the production of plastic objects.
Specifically, objects to be treated are placed in a tank containing liquid nitrogen (-196oC). Due to the different contraction between the steel structure and paint coat, the paint cracks. The cracked paint can be removed by mechanical action. The process can be realized in a continuous and completely automated plant. Conventional processes utilize acid dripping or pyrolitic ovens and produce pollutants. Liquid nitrogen, chemically inert, is already in the atmosphere and can be obtained at low cost. This type of process does not produce liquid waste.
The technology has been fully operational since 1990. It is covered by a patent.
Environmental and Economic Benefits
The project benefits include,
| The technology produces lesser quantity of waste. |
| The solid waste that is produced can be recovered and utilized to produce plastic objects. |
| Nitrogen is a comparatively low cost raw material and the objects processed by this technology have a life span five times longer compared to those produced by other processes. |
Investment cost is estimated as $220.00 - $250.00 US, based on 2.50 kg/hr of treated objects. Payback time is 1-1.5 year.
Constraints
This process has a high productivity until 3.00 kg/hr.
Contacts
Review Status
This case study was submitted to UNEP IE in 1994 by Italy's ENEA. It was reviewed and edited by UNEP IE in July 1995.
Subsequently the case study has undergone a technical review by Dr Prasad Modak at Environmental Management Centre, Mumbai, India, in September 1998.
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