Action of free oxygen jet

Velocity of the free oxygen jet is important. Axial velocity decreases as the distance downstream the nozzle increases due to entrainment of the surrounding. In the converter as the blow begins, the surrounding of oxygen jet is hot atmosphere. As the blow continues the jet surrounding changes from  carbon monoxide to slag. For most of the periods the jet is submerged into slag. The surrounding in the converter is dynamic. The velocity of the jet depends on upstream pressure, downstream axial distance and the surrounding. It is difficult to calculate the jet velocity when the surrounding is changing, but the momentum flow rate within the get is independent of the distance downstream the nozzle and can be calculated from:

(5)

Where  momentum flow rate in (Newton)

 upstream stagnation pressure (bar)

N= Number of nozzles

 Surrounding pressure

 Throat diameter of the nozzle(m)

Upstream stagnation pressure can be calculated

(6)

T= capacity in tons.

Throat diameter is function of converter capacity and number of nozzles

(7)

For a 150 ton converter, diameter of each nozzle of a 4 hole lance is calculated to be 0.035 m by equation 7.  is calculated to be 11.37 bar by equation 6 and total momentum flow rate produced by a four hole nozzle is 4057 N by equation 5. For more details the readers can look into the references given at the end of the lecture.

Jet carries with it momentum flow rate which on hitting the bath is converted into force. Thus action of free jet can be described in terms of dimensionless flow rate number

(8)

 density of liquid , g ( ) and X (m) is distance between the lance tip and liquid bath surface. If X is 3m and 1.5 m then   and . We note that the dimensionless number increases with the decrease in the lance distance. Thus dimensionless flow rate number can be used to describe the dynamic variation of the lance distance. The dimensionless momentum flow rate number signifies the action of the gas jet on the bath at a distance X against the gravity