Metallurgical Knowledge
BOF for electric dust blowing of converter

2017-03-27 hit:

At present, there are two main methods for the purification and recovery of oxygen converter steelmaking, one is the gas wet (OG) purification recovery system, the other is the gas dry method (LT method). The technology of electrostatic precipitation is adopted in the dry gas purification and recovery, and the flue gas purification effect, energy consumption, area and so on are obviously better than the traditional OG method. At present, the key equipment and technology used in electrostatic precipitator have been made domestically. In the actual production, because of the bad coordination between the converter and the electric dust collector, the problem of electric dust removal and explosion is often occurred. It is necessary to adopt the oxygen / nitrogen blowing method to separate the traditional OG method, which can avoid the occurrence of electric dust removal and explosion.

2, electric dust explosion venting failure analysis

The fundamental reason of the inner explosion of the electrostatic precipitation is that after the CO and O2 concentration reaches a certain proportion, the high voltage flashover caused by the high voltage flashover in the dedusting electric field causes the explosion. Mainly in the converter start blowing carbon oxygen reaction is very intense, CO quickly, if CO is produced in the mouth without complete combustion into the electrostatic precipitator, and the smoke in the air blowing before mixing, reach 12.5%~74.2% explosion limit, explosion in the dust remover, the vent valve is opened, provided to oxygen lance interrupt blowing converter.

3, solution

Using the "normal smelting" and "two times under the gun", the two ways of blowing.

3.1, the normal smelting blowing mode

In the end the first time against the hot metal converter blowing, in order to strictly control the reaction rate of molten iron and O2, produced in the early stage of the CO requirements for complete combustion in the furnace becomes CO2. Select "converting normal smelting" began to flow in 40% normal setting as the starting flow, according to the actual flow of oxygen curve reaches the set flow after 90s, namely BOF oxygen flow control according to a certain slope slow rise. In this condition, when the initial flow of low oxygen blown away, O2 and molten metal reaction is not intense, resulting in the converting process of CO to CO2 can be completely combustion in the furnace, and CO2 for non explosive gas, forming a piston type flue gas column using CO2 gas, promote the residual gas pipeline from the air. The subsequent generation of CO rich converter flue gas using O2 isolation CO2 flue gas and air non explosive in the open, CO and O2 concentration in the explosion outside the scope of control. This method is generally used for the first time after the converter iron.

3.2, "the next two gun" blowing method

Converter production is usually in the latter part of the temperature of the sample, after the completion of the need for two oxygen lance blowing 2~5min, at this time the carbon content of molten iron has been greatly reduced, while the use of the "two gun" blowing method. The specific control method: the oxygen lance leaves the blowing position to blow N2Ts, N2 enters the dust collector to dilute the oxygen content in the dust remover, achieves the purpose of avoiding the explosion. Start with the 60% to set the flow blowing, 30s to set the flow value, start the normal blowing. The way of blowing the smoke hood and avoid venting, at the same time than the "normal smelting" way of blowing oxygen curve slope is large, shorten the blowing time, improve efficiency.

In two kinds of blowing mode are starting flow control valve, considering the lag, according to field test and experience are starting valve regulating valve, in strict accordance with the curve of oxygen blowing.