Method for air pollution control combined with safe recovery and control

Abstract

A gas collector hood is located close to the mouth of a converter vessel and has a diameter which is not much greater than the mouth of the vessel. A mixture of oxygen together with entrained powdered materials based on process requirements and a hydrocarbon fluid as cooling agent are blown through tuyeres in the bottom of the vessel and diffuse through the hot metal in the vessel. The inherently finer dust produced from the bottom-blown oxygen process requires that for proper air pollution control a non-combustion system be used to take advantage of the increased agglomerating properties of iron oxides when produced in reducing atmospheres. When blowing is initiated in this process carbon monoxide and hydrogen evolve immediately and in order to render the gases inert, air is aspirated into the gas collector hood so that an inert gas plug is formed which purges the exhaust system of combustion air. A short time after blowing is initiated, the hood is brought down to proximity with the vessel in which case only a small percentage of the theoretically required air for combustion is aspirated. Nitrogen is injected as required into the hood in addition to air aspirated to artificially create inertization to turn down a heat at high carbon levels, for emergency vessel turn down, and for special heats. Near the end of a normal low carbon heat, air is again aspirated into the hood so that an inert gas plug is formed for safe turn down of the converter. Control of the system is achieved through high response sensors based on a gas analysis system independent of the components and products of combustion in the gas phase, operated together with automatic suction control incorporated as part of the gas cleaning system.