As part of an investigation by the Bureau of Mines of methods for recovering alumina from domestic nonbauxitic resources, aluminum chloride hexahydrate (ach) crystals are decomposed in two dense fluidized-bed reactors in series. In the first reactor, ach is fluidized by the gases of decomposition (hcl and h2o) produced by indirect heating of the bed and by steam. Concentrated hydrochloric acid may be recovered for use in the process. Partially decomposed solids enter a second fluidized-bed reactor for completion of the decomposition to cell-grade alumina by direct heating with combustion gases. Results from the first-stage decomposition step in a 4-in cylindrical glass reactor and in a tubular bundle reactor are reported. Test conditions included a fluidization face velocity of 0.4 M/sec, space times of 30 min or longer, heating indirectly to temperatures of 190 deg to 375 deg c, and gas compositions of 0 to 43 mol-pct hcl and 100 to 57 mol-pct steam. The direct-heated second-stage reactor, a 4-in alloy cylinder was operated at a fluidization range of 600 deg to 1,005 deg c, and with furnace gases containing steam and oxygen of 17.4 to 57.8 total vol-pct. The product is composed of coarser particles than are normally used in an alumina reduction cell, and contains 0.1 pct chloride, which is not present in Bayer alumina.
Pres. At 112th TMS-AIME Ann. Meeting, March 1982, Paper in Light Metals 1983, PP. 253-271