CoJet ® Gas Injection System
Cody Kaufman - Praxair Metal Technologies
Supersonic gas jet applications in the steel industry originated in BOF
steelmaking, open hearth steelmaking, and cutting torches. The use of
supersonic gas jets has expanded into EAF and AOD steelmaking, vacuum
furnaces and cupolas. Conventional supersonic gas jets delivered through
top lances are limited in the distance over which the supersonic velocity
is maintained, the gas flow rate that can be injected without excessive
splashing and the extent of stirring provided to the molten bath.
Praxair's Coherent Jet (superscript: TM) technology has been successfully
used in EAF, BOF and cupola operations.
CoJet is short for Coherent Jet Technology which employs a flame envelope surrounding the supersonic jet core of oxygen gas, which tends to preserve the force of the oxygen at up to five times the distance of conventional supersonic jets. The jet is useful at 50" - 100" from the injector vs. 10" - 20" for conventional supersonic jets. Concentration of oxygen is also much higher, as is the velocity of the oxygen at any specified distance. We will discuss how this is proving beneficial in EAF (Electric Arc Furnace), BOF (Basic Oxygen Furnace) and Cupola style refining of steel.
In the EAF refining process, the use of the CoJet allows the mounting of the lances in the sidewalls of the furnace (as opposed to manupulating a lance through the slag door). This offers numerous benefits:
- Lower Power Consumption (closed furnace)
- Better mixing and slag formation (multiple lances pierce the metal surface)
- Improved production rate
- Deeper penetration of the molten pool with decreased de-carburization
- Reduced emissions and maintenance of the furnace refractory
In the BOF furnace the CoJet can replace 60 foot consumable lances. Mixing comparable to bottom blowing can be achieved using CoJet technology only from the top (which improves refractory life and production rates.)
The direct reported benefits include:
- shorter mixing time
- Less Nitrogen gas entrapment at turndown
- Better Manganese retention at turndown
- A modest increase in yield (about .6 - 1%)
- Better retained homogeneity
CoJet is currently being evaluated for Cupola refining. The goals here will be to improve penetration of the oxygen into the coke bed.
[Much of the detail and graphics connected to this presentation are available at the Praxair Website. The direct link is:
CoJet Gas Injection System