Off gas preparation for vacuum pumps

Abstract

Vacuum steel degassing plants generate off-gases that are hot, dangerous and dust laden.
Therefore they must be cooled down, post-combusted or conveyed in a safe manner and filtered in order to
protect the vacuum pumps and the environment.
A risk analysis is necessary for all kinds of vacuum plant regardless the pump system used.
This analysis defines the hazard zones and the necessary means to avoid such hazards or a hazard compliant
equipment to be installed. The handling of moisture and the protection against the associated corrosion effects
are a concern for the dust filters and the vacuum pumps.
The dust load requires special means of erosion protection. The dust abatement and dust extraction from
the various gears must be compliant with the dangers of impact by high speed particles, of dust ignition and
of aqueous condensates. 50 % of the dust is in a range of 0,2 to 1,5 ?m and thus a challenge for filters that
combine a high filtering efficiency with a low pressure drop.
All necessary gears in the connection between vacuum pump and metallurgical reaction vessel, that are
installed for post-combustion, gas cooling and dust abatement as well as suction duct with all its bows generate
pressure losses that could only be compensated by an increased pump capacity. Since this is an important
investment and generates higher operation cost one is tempted to take means to reduce such losses. However,
this might again require higher pump down capacities. A detailed study involving all parameters is therefore
recommended in order to evaluate the various measures to be taken.