Back-attack phenomena of gas jets with submerged horizontally blowing and effects on erasion and wear of refractory lining

Taken the refining process in an 18 t AOD vessel for example, the "back-att ack" phenomena of the horizontal rotating and non-rotating gas jets and the ir effects on the erosion and wear of the refractory lining were investigat ed 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 (includ ing the tuyere) with its prototype was 1/3. The relations of the gas blowin g 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 pre ssures were continuously monitored and measured by means of a dynamic resis tance strain-meter of YD-21 type with an anti-water pressure sensor made sp ecially. A light-beam oscilloscope of SC16A type recorded simultaneously th e back-attack waves. Also, the modeling experiment on the erosion and wear of the refractory lining was carried out. The results indicated that the ba ck-attack phenomena of the horizontal rotating and non-rotating gas jets ha ve respectively the different features from that in a bottom blowing. On th e 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 sl it pipe (sub-tuyere) streams show an evident alleviation and suppression ef fect. The circulative motion of the liquid in the bath would be another imp ortant 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 inf luence of the tuyere position (the angle included between the two tuyeres) is not so remarkable in the conditions of the present work. The rotating mo tion of a horizontal gas jet may decrease the frequency and intensity of th e back-attack action and reduce the eroded and worn rate and area of the re fractory lining under a same blowing pressure. The annular-spiral tube type tuyere with a reasonable structure may be expected to have a good latent u sing power and composite effectiveness.