Electrostatic dust collection during converter steelmaking

Abstract

The oxygen-blowing of pig iron in converters is accompanied by intensive dust generation. Particles of metal which are formed as a result of vaporization and atomization in the region where the oxygen jet enters the furnace are entrained by the jet and removed from the converter. For the dust to be deposited within the converter, the particles must be acted upon in a way that causes their trajectory to remain inside the converter. One possibility is to subject the particles to an electrostatic field (assuming that the particles are charged). The charging can be done by means of ions of a gas (due to their high mobility, electrons are not held strongly on the particles). High temperature leads to spontaneous ionization of a gas, which can be intensified by superimposing an electric field.The dependence of the degree of ionization of the gas on temperature can be described by the relation [1]:where U i is the ionization potential of oxygen, V; m is the mass of an oxygen ion, g; e is the elementary charge, cml/2.gl/2; k is Boltzmann's constant; h is Planck's constant; X is the degree of ionization; P is the gas pressure, mm Hg. In accordance with this equation, the degree of ionization at a temperature of 1900 K reaches 1.6.10 -3, or 6.5.1021 charge pairs per 1 m 3 gas.On the other hand, in a top-blown industrial converter in which the gas undergoes complete combustion, the concentration of CO dust is 1014 particles per 1 m 3 gas. The ratio of the number of charges to the number of particles makes it possible to suggest that all of the dust may be charged in this case, and the application of an electric field to such a system will cause the particles to be directed toward a collecting electrode. The metal bath could function as such an electrode under the given conditions. According to a preliminary estimate, neither the physical condition of the medium nor the energy costs would be serious obstacles to the use of an electrostatic field as a dust-collecting medium. To determine the field strength that would ensure efficient dust collection inside a steelmaking furnace, we conducted laboratory studies under conditions simulating the oxidizing blowing of pig iron in a converter. To do this, oxygen was delivered to the surface of molten pig iron through a cooled lance.The temperature of the melt was kept at the level 1500-1550~ and the temperature of the corona electrode was kept within the same limits by using a graphite heater that was three times higher than the crucible. High voltage was supplied to the electrode, which was introduced into the cavity of the lance. The collecting electrode was a heated tube made of A1203. The tube was placed in contact with the graphite heater, which had also been supplied with the necessary voltage. The degree of dust collection e was evaluated on the basis of the relative difference between the weights of filters through which the gas travelled when it left the high-temperature zone in the presence and the absence of the high-voltage field: e = 1 -AGf/AG, where AGf is the change i...

Nonlinear Effect of Electrostatic Atomization with Multiple Nozzles

“…Electrostatic atomization technology has been widely applied in industrial dedusting [1], micro/nano processing [2], atomizing combustion [3] and other fields. The electrostatic atomizing system based on induction charge usually uses the nozzle-electrode structure, liquid medium which flows through the nozzle is charged under the action of the electrostatic field and the droplets is broken down and atomized into small charged particles by overcoming the surface tension under coupling field of the electric field's force and gravity [4].…”