INFLUENCE OF SLOW DESCENT OF SOLID UPON THE FLUIDS FLOW BEHAVIOR IN PACKED-BEDS IRRIGATED BY A LIQUID COUNTERCURRENT TO AN UPRISING GAS-STREAM

In the upper part of the dropping zone in a blast furnace, gas and liquid flow upwards and downwards and the flow behavior has been investigated by using fixed beds. However, burden continually descends there. In the present work, liquid hold-up and gas pressure loss in fixed and moving beds were measured to examine the effect of solid movement. (1 ) Measured pressure losses in both dry beds are smaller than those calculated from the Ergun equation. This is considered to be caused by the following facts: Large ratio of particle to column diameter is chosen (ca. 1/6) so that the influence of particle movement may reach the column inside, and hence the flow near the wall affects pressure loss relatively largely; stainless steel balls used as packing material are of high order of sphericity and have smooth surface. (2) As solid velocity increases, total, static and dynamic hold-ups (H(t), H(s), H(d)) decrease, while H(d)/H(t) slightly increases. The solid movement increases pressure loss in irrigated bed. (3) The following empirical correlations for pressure loss in fixed bed DELTAP(F), total hold-up in moving bed H(tM) and pressure loss in moving bed DELTAP(M) are obtained: DELTAP(wF)/DELTAP(dF) = {(epsilon-H(tF))/epsilon}-1.90 H(tM) = 2.38(v(S)/v(L))0.188.H(tF)0.420 DELTAP(wM)/DELTAP(dM) = 1+(v(L)/v(G))0.136{0.895+204(v(S)/v(G))0.669} where, H(tF): total hold-up in fixed bed, DELTAP(d), DELTAP(w): pressure losses in dry and irrigated beds, v(G), v(L), v(S): velocities of gas, liquid and solid, epsilon: void fraction of beds. These equations reproduce experimental results within errors of +/-15, +/-10 and +/-15%. The last one also reproduces those for fixed bed within an error of +/-15%.