Physicochemical processes in the linings of pellet-roasting machines

Abstract

At the NorthMining-BeneficiationCombine (NlVIBC) pellets are roasted in two imported machines (service life more than 6 years) and two home-produced OK-306 machines (service life more than 3 years). Their design features are shown in Fig. 1, together with the sites at which samples of slag and the liping were taken. The pellet-roasting regimes are characterized by the mean temperatures and pressures over the zones of the roasting machines (Fig. 2).During these investigations we observed "inverting" of the cone, leading to a temperature rise in the branch pipes of the return flow manifold and to fusion of the lining. .C:ooUng , Gas-ai~ chamber numbers H) above pellet layer; 1) in gas--air chambers; 2) above pellet layer; 3) total pressure.All-Union Institute of Refractories. North Min|ng-Beneflciation Combine. Translated from Ogneupory, No. 10, pp. 33-40, October, 1979. 0034-3102/79/0910-0621 $07.50 9 1980 Plenum Publishing Corporation 621 The following m a t e r i a l s a r e used for the lining of the home-produced machines: high-alumina MKO-72 and MLO-62 artifacts, ShB-1 chamotte brick for laying the roasting, recuperation, and I cooling zones; VGL-1.3, ShLB-1.3, and SkLB-0.4 heat-insulating brick, kaolin wool, and heat-insulating gunite concrete, developed by the E a s t e r n Institute of R e f r a c t o r i e s (30% of M500 alumina cement, 30% of chamotte filler, and 40% of chrysotile asbestos of 7-450 brand); the t e m p e r a t u r e of the lining during use reaches 1000~The concrete is used for gtmiting the forward flow manifold and the branch pipes to the precombustion c h a m b e r s . Heatinsulating m a t e r i a l s constitute up to 50?o of the lining volume.To investigate the physicochemical effect on the r e f r a c t o r y lining we determined the g r a i n -s i z e and chemical compositions of the dust and gases. The g a s e s (the combustion products of natural gas of the Shebelinsk deposit) contained 0~ CO, 0.2-0.6% CO2, and 19.75-20.8% 0 2. The dust content of the g a s e s was 1.31 k g / m S ; the m o i s t u r e content was 10 g / m 3 (under n o r m a l conditions).The m e a n -s i z e composition of the dust (broken pellets) was as follows: 1.1% of the --2/~m fraction, 18.2% 5-10/~m, 23.8% 10-20t~m, 21.50/o 20-40/~m, 8.7% 40-60/zm, 4.2% 6 0 -8 0~m , 2.6% 80-100/~m, 4.1% t o r y . The s t r u c t u r e of the slag is c h a r a c t e r i z e d by i s o m e t r i chematite grains, the size of which ranges f r o m 0.02 to 0.08 ram, and a vitreous substance (Fig. 4). Table i shows the phase composition of the mullite--corundum brick with slag.The l e a s t -a l t e r e d zone is yellowish, dense, and uniform. Microscopic examination r e v e a l s s e c t o r s of mullite and corundum aggregates and a porous binder. The mullite aggregates consist of dense intergrowths of c r y s t a l s ; the corundum aggregates a r e l e s s dense. The vitreous substance is distributed in the binder fairly uniformly, but predominant filling of the p o r e s is observed.The intermediate zone is m a c r ...

Processes of the action of iron and its compounds on a refractory lining

“…Their mineral composition consists of concretions of fine grains of hematite and an insignificant quantity of calcium ferrites, quartz, and glass, that is, similar to the composition of the dust and pellets [3]. The chemical composition* of the crust is (wt.%) 77.96 Fe203, 7.37 A1203, 11.56 SiO2, and 1.56 CaO (the content of these same oxides in the pellets is 84.2, 1.87, 9.9, and 2.98%, respectively).…”