Cold Model Study on Burden Bahaviour in the Lower Part of Blast Furnace.

Abstract

The motion of solid particles flowing into the raceway and the behaviours of the raceway and deadman were studied on the basis of the flow patterns obtained using a two-dimensional and a three-dimensional cold models. The lower part of the blast furnace consisted of the three characteristic regions, the converging, fast flow region with smooth steam and time lines, the deadman with motionless particles, and the quasi-stagnant region situated over the deadman, in which the particles moved very slowly with zigzag, complicated stream line. The quasi-stagnant region was formed by the particles fed within a small, limitted area near the center at the top of the bed. The radius of the area was expressed as a function of burden descending velocity only. It was suggested that the size of deadman changes depending on whether the furnace operation is carried out with all-coke or injection of pulverized coal. The periodic expansion and contraction of the raceway, therefore, the unstable burden flow in the converging flow channel, occurred when the tuyeres were not inserted into the inerior of the bed. The burden flow became more stable with higher blast gas. The boundary conditions of the fast moving region and deadman around the raceway were discussed. The plasticity theory was applicable to simulate the boundaries of such characteristic regions.