Steam ejector vacuum pumps (SVPs) are mainly used on larger melt sizes up to 350 t in
integrated steel plants because of the availability of steam. The use of dry operating
mechanical vacuum pumps (MVPs) for steel degassing has made a tremendous step forward in
the past 10 years but is still confined to melts below 150 t while its progress towards
larger melt sizes is not completed. Besides the consideration of investment and operating
costs there is no restriction in using any type of modern vacuum pump system for all
vacuum processes and plant designs. Both systems fulfil all metallurgical requirements.
Considering the significant savings in operating cost offered by MVP systems it is worth
reconsidering the efforts for reducing air leaks, the use of protective gases and pressure
losses between the pump set and the metallurgical reaction vessel. Both systems have made
progress in energy optimising but the MVPs have a striking energy advantage. Only the
overall costs should be considered, including those necessary to meet emission constraints
and safety standards, and only the pressure prevailing at the reaction vessel is to be
considered when comparing vacuum pump systems. Also, the means and use of dust abatement
systems should be reconsidered since they offer cost savings by reducing the frequency of
cleaning, less wear, little sludge handling and the significantly lower design suction
capacity of SVP systems. The SVP mass flow need is to be corrected by a special
coefficient before being applied to the volume conveying MVPs. Depending on the
operational pressure required for the pump design, MVP systems can reach the same
performance at the reaction vessel with much less mass flow capacity than that needed by a
SVP system.