The multi-stage ejector system can have as many as five stages, or four stages with a liquid ring pump replacing the fifth stage (as shown). A hogger is used to meet evacuation time requirements. This system is only one possible solution.
Vacuum degassing of steel takes place after the molten steel has left the furnace and before the steel is poured into ingots or processed through a caster. The main objectives of steel degassing are:
After leaving the furnace, molten steel is moved in a ladle to the degassing area and positioned inside the degasser. The ladle is covered with a layer of slag that is penetrated approximately 18” deep by the snorkels. As the snorkels are inserted, the Nash steam ejectors create a vacuum of 0.5 mm HgA in the vacuum chamber to draw the steel into the chamber. The lower partial pressure within the vacuum chamber removes both hydrogen and nitrogen gases from the liquid steel, which are both vented as the steel is continuously circulated. The evacuation time is usually five minutes or less.
In order to design your degassing system, you will need the following information:
Each degassing system is designed to meet the steel mill’s specific requirements. 100 years of design experience with liquid ring pumps and steam jet ejectors makes Nash the top choice for your system. Steam jets work on a constant mass flow basis, while liquid ring vacuum pumps work on a constant volume basis. Used together, an economic break-even point may be reached to take advantage of the best characteristics of each. Your Nash engineer can help you determine the optimal solution.