INTERNATIONAL CLEANER PRODUCTION INFORMATION CLEARINGHOUSE

CASE STUDY #10
1.   Headline: Waste reduction in steelwork painting
2.   Background: In the 'Ostrowiec' Steelworks the
     manufacture of steel products is carried out using
     production-line methods. The final operations required
     for almost all products are surface treatment and
     painting. In the Machinery Building Department these
     operations are carried out with shot-blasting machines
     and manually operated spray booths. The original painting
     method was air-atomized spraying which has the lowest
     transfer efficiency of the coating methods and yields
     large quantities of waste.
     The 'Ostrowiec' Steelworks consist of eleven
     Departments, the main production departments are
     Steelworks, Processing, Steel, Construction, Machinery
     Building and the Foundry.
3.   Cleaner Production Principle: Process modification
4.   Description of Cleaner Production Application: A
     pollution prevention audit was carried out to improve the
     environment and efficiency and working conditions in the
     painting areas. The objective of this program was to
     reduce the quantity of wastes and costs of painting by a
     combination of improvements to the technology and good
     housekeeping. The overall aim was to improve the quality
     of coating, to reduce the amount of paint raw material
     and to reduce the quantities of wastes.
     The existing painting method was compared with two more
     advanced painting technologies. The transfer efficiency
     for the different methods are as follows:
          air-atomized spray (conventional)     30-50%
          airless spray                     65-70%
          pressure atomized electrostatic spray  85-95%
     In conventional spraying compressed air is used both to
atomize the paint and carry it to the surface to be painted.
With airless spraying the paint is pumped under high pressure
to a small jet where the high velocity is sufficient to induce
atomization. The lack of any expanding compressed air stream
eliminates unwanted spray mist, reduces the loss of paint by
overspray and most of the paint adheres to the work surface.
With pressure atomized electrostatic spray, paint is delivered
at high pressure as before, but is fed to a insulated nozzle.
An electrostatic charge of about 100kV is applied to this
nozzle. The charging of the paint particles assists the
atomization and causes them to repel each other. Additionally
the charged paint moves along the field lines to the earthed
work piece. As the electrostatic field lines envelop the object
the paint particles cannot fly straight past, but 'wrap'
themselves uniformly around the surface. It is this effect that
gives high paint efficiency and reduces waste. Note that
electrostatic hand spray guns require a small mains transformer
and a very reduced current to avoid accidental electrical
shock. Tests carried out with the two improved painting methods
showed the following results:
     Comparison of raw material consumption and waste
     quantities of the different methods:
              Air-atomized      Airless      Pressure
                  spray        spray        atomized
                                          electrostatic
                                          spray
     Paints       8.0 m3       6.8 m3       5.6 m3
     Solvents     6.5 m3       1.6 m3       1.6 m3
     Wastes       2,400 kg     1,400 kg     500 kg
5.   Economics:  (Estimates, based on Trials)
                      Airless spray     Pressure atomized
                                      electrostatic
spray
     Cost saving               US$/year
     Total savings     38,500           39,400
     Capital investment US$4,800         US$13,000
     Payback period1.5 months        4 months
6.   Advantages: Reduction of high disposal costs. Reduced
running costs. Decreased financial liability by generating a
smaller quantity of hazardous wastes. Improved public
perception and acceptance in the business community. Also
indicated were potential reductions in the effluent
concentrations of about 45% for sludge and 75% for organic
solvents.
7.   Constraints: N/A
8.   Contacts:Mrs Lucyna Chrzanowska
                  Steelworks 'Ostrowiec'
                  ul Swietokrzyska 8
                  27-400 Ostrowiec Swietokrzyski
                  Poland
                  Tel: +48 472 528 81
                  Fax: +48 472 512 34
                  Telex: 0612581 hn pl
9.                   Keywords:    Poland, metal, iron and
                    steel, painting, process modification,
                    electrostatic spray, airless spray, raw
                    material saving
10. Reviewer comments: This case study was originally
published in the UNEP IE document "Cleaner Production
Worldwide". In the process of preparing the document the case
study underwent a technical review.