Vacuum Degasser (“VD”) is used to reduce the concentrations of dissolved gases (H2, N2, O2 ) in the liquid steel; Homogenize the liquid steel composition and bath temperature; remove oxide inclusion materials from the liquid steel; and, provide the means and technical conditions that are favorable for final desulfurization.
During operations at the VD, the liquid steel is stirred to promote homogenization by percolating argon gas through a single refractory stir plug arrangement in the bottom of the ladle. The argon connection to the ladle is established when the ladle is set in place inside the vacuum tank.
The vacuum tank is evacuated to the required operating pressures by one of three ways: steam jet ejector, steam jet ejectors and a water ring pump, or, mechanical pumps. Emissions are evacuated through a vacuum pumping system and are collected prior to the pumps or they are discharged under water contained within a weir wall-equipped concrete hotwell. The process gases, including those entrained in the intercondenser discharge water, are exhausted from the hotwell via a motor driven fan to a vent stack equipped with a flare burner. Hotwell water is pumped to a cooling tower of the contact water system.
Dry pump systems are set up in a 3 - stage or 4-stage design, containing a combination of rotary lobe and screw pumps. Depending on the required suction capacity several modules can be installed.
Dry mechanical pump features:
• Lower operational costs compared to steam jet pumps;
• No contact cooling water needed;
• Compact and modular installations;
• Vacuum control by gas dilution;
• Redundant systems can be installed upon Customer's request ;
VD pump Control