1999 Volume 39 Issue 8 Pages 779-786
Taken the refining process in an 18 t AOD vessel for example, the "back-attack" phenomena of the horizontal rotating and non-rotating gas jets and their effects on the erosion and wear of the refractory lining were investigated in a water model. For this refining process, the two-tuyere (lance with constant cross-sectional area) blowing of gas is operated using the annular-tube type tuyere. The geometric similarity ratio of the model unit (including the tuyere) with its prototype was 1/3. The relations of the gas blowing rate, blowing pressure, angular separation between the two tuyeres, type of tuyere and other operation parameters with the back-attack action of the gas jet and the refractory lining erosion and wear were examined under the different operating modes. The appropriate back-attack frequencies and pressures were continuously monitored and measured by means of a dynamic resistance strain-meter of YD-21 type with an anti-water pressure sensor made specially. A light-beam oscilloscope of SC16A type recorded simultaneously the back-attack waves. Also, the modeling experiment on the erosion and wear of the refractory lining was carried out. The results indicated that the back-attack phenomena of the horizontal rotating and non-rotating gas jets have respectively the different features from that in a bottom blowing. On the back-attack phenomena of these two kinds of jets, the gas streams of the inner tubes (main-tuyeres) have all a governing bearing, and the annular slit pipe (sub-tuyere) streams show an evident alleviation and suppression effect. The circulative motion of the liquid in the bath would be another important reason to bring about the back-attack phenomenon of a submerged gas jet. The buoyancy force gives a considerable influence; it is able not only to increase the back-attack intensity of a horizontal gas jet, but also to enlarge the locally eroded and worn zone of the refractory lining. The influence of the tuyere position (the angle included between the two tuyeres) is not so remarkable in the conditions of the present work. The rotating motion of a horizontal gas jet may decrease the frequency and intensity of the back-attack action and reduce the eroded and worn rate and area of the refractory lining under a same blowing pressure. The annular-spiral tube type tuyere with a reasonable structure may be expected to have a good latent using power and composite effectiveness.