A carbo-chlorination process is disclosed for selectively producing AlCl.sub.3 from an alumina-containing feedstock, comprising introducing the following into a fluidized bed reactor maintained at 600-700 C.: (a) dried and calcined feed stream comprising the alumina-containing feedstock and a carbon feed; (b) chlorinating agent; (c) selectivity agent; (d) dried air; and optionally (e) off-spec AlCl.sub.3. The process further includes removing a vapor stream from the reactor in which preferably about 75-80%, of the alumina present in the reactor is converted to AlCl.sub.3; and also removing a solid raw pozzolan stream from the reactor, wherein about 90-99% of the silica present in the reactor remains unconverted and exits the reactor through the solid raw pozzolan stream. The vapor stream comprising AlCl.sub.3 is purified to create an AlCl.sub.3 product stream comprising preferably greater than about 99.99% AlCl.sub.3. The raw pozzolan product is classified to remove coke and create a final pozzolan product having a strength activity index (SAI) in the range of 80-160, per ASTM 618.

Systems and methods for recovery of gaseous substances from molten salt electrolysis are generally described. Certain systems comprise a cell configured for molten salt electrolysis; a collector fluidically connected to the cell and configured to collect volatilized molten salt from the cell; and a gas scrubber fluidically connected to the collector and configured to at least partially remove a gas from an effluent stream of the cell. Some methods comprise, using a pressure gradient: transporting a gas comprising molten salt vapor from an electrolytic cell to and through a collector such that at least a portion of the molten salt vapor forms a solid within the collector; and transporting some or all of the gas from the collector through a gas scrubber.

A waste heat recovery and utilization system includes a material waste heat extraction subsystem, a flue gas waste heat recovery subsystem and a control subsystem; the material waste heat extraction subsystem is in communication with the flue gas waste heat recovery subsystem for extracting, by utilizing a flue gas flowing through the material waste heat extraction subsystem, a waste heat from a material with waste heat to be recovered; the flue gas waste heat recovery subsystem is used for recovering a waste heat of flue gas discharged from an aluminum electrolytic cell and a waste heat extracted from the material with waste heat to be recovered; and the control subsystem is used for regulating and controlling operational parameters of the material waste heat extraction subsystem and the flue gas waste heat recovery subsystem during waste heat recovery and utilization.

A waste heat recovery and utilization system includes a material waste heat extraction subsystem, a flue gas waste heat recovery subsystem and a control subsystem; the material waste heat extraction subsystem is in communication with the flue gas waste heat recovery subsystem for extracting, by utilizing a flue gas flowing through the material waste heat extraction subsystem, a waste heat from a material with waste heat to be recovered; the flue gas waste heat recovery subsystem is used for recovering a waste heat of flue gas discharged from an aluminum electrolytic cell and a waste heat extracted from the material with waste heat to be recovered; and the control subsystem is used for regulating and controlling operational parameters of the material waste heat extraction subsystem and the flue gas waste heat recovery subsystem during waste heat recovery and utilization.