Effluent gas recycling and recovery in electrolytic cells for production of aluminum from aluminum chloride

Claim 2

IN A PROCESS FOR ELECTROLYSIS OF ALUMINUM CHLORIDE DISSOLVED IN A MOLTEN METAL HALIDE ELECTROLYTE CONTAINING AT LEAST ONE HALIDE FROM THE GROUP CONSISTING OF AKALI METAL HALIDES AND ALKALINE EARTH METAL HALIDES TO PRODUCE ALUMINUM AT ABOVE 660*C, WHEREIN EFFLUENT GAS CONTAINING GASEOUS ALUMIMIUM CHLORIDE AND AT LEAST ONE GASEOUS HALIDE OF THE SAID ELECTROLYTE IS EVOLVED, THE STEPS COMPRISING SELECTIVELY CONDENSING AND SEPARATING FROM SAID EFFLUENT GAS A MIXTURE OF ALUMINUM CHLORIDE AND AT LEAST ONE SUBSTANCE SELECTED FROM THE GROUP CONSISTING OF ALKALI METAL HALIDES AND AKALINE EARTH METAL HALIDES, AND SUBSEQUENTLY CONDENSING REMAINING ALUMINUM CHLORIDE FROM THE RESIDUAL GASEOUS EFFLUENT.

Claim 3

The process of claim 1, wherein the said condensed mixture is returned to the said electrolyte.

Claim 4

The process of claim 1, wherein the said subsequently condenssed aluminum chloride is returned to said electrolyte.

Claim 5

The process of claim 1, wherein both the said condensed mixture and the subsequently condensed aluminum chloride are returned to the said electrolyte.

Claim 6

The process of claim 1, wherein chlorine is recovered from the residual gaseous effluent subsequent to said subsequent condensing of aluminum chloride.

Claim 7

The process of claim 1, wherein the selective condensing is effected at a temperature of about 100*-250*C, and the subsequent condensing is effected at a temperature lower than the temperature employed in said selective condensing.

Claim 8

The process of claim 1, wherein the alkali metal halide is alkali metal chloride, and the alkaline earth metal halide is alkaline earth metal chloride.

Claim 9

The process of claim 1, wherein the said step of subsequently condensing remaining aluminum chloride in the residual gaseous effluent is effected at a lower temperature than the said selective condensing step.

Claim 10

In a process for electrolysis of aluminum chloride in a metal halide electrolyte containing at least one halide from the group consisting of alkali metal chloride and alkaline earth metal chloride to produce aluminum at above 660*C wherein effluent gas containing aluminum chloride is evolved, the steps comprising cooling a stream of the effluent gas generated by such electrolysis of aluminum chloride to a temperature of 100* to 250*C, thereby condensing from said effluent gas aluminum chloride and at least one substance selected from the group consisting of alkali metal chloride and alkaline earth metal chloride, separating the resulting condensate from the said gas stream, subsequently cooling the remaining gas stream to a temperature lower than the temperature employed in said first cooling step to condense remaining gaseous aluminum chloride therein, and thereafter filtering said gas stream.

Claim 11

In a process for electrolysis of aluminum chloride in a metal halide electrolyte containing at least one halide from the group consisting of alkali metal chloride and alkaline earth metal chloride to produce aluminum at above 660*C wherein effluent gas containing aluminum chloride is evolved, the steps comprising cooling a stream of the effluent gas generated by such electrolysis of aluminum chloride to a temperature of 100* to 250*C, thereby condensing from said effluent gas aluminum chloride and at least one substance selected from the group consisting of alkali metal chloride and alkaline earth metal chloride, separating the resulting condensate from the said gas stream, subsequently cooling the remaining gas stream to a temperature lower than the temperature employed in said first cooling step to condense remaining gaseous aluminum chloride therein, and thereafter filtering said gas stream.

Claim 12

In a process for electrolysis of aluminum chloride dissolved in a molten metal halide electrolyte containing at least one halide from the group consisting of alkali metal halides and alkaline earth metal halides to produce aluminum at above 660*C, wherein effluent gas containing gaseous aluminum chloride and at least one gaseous halide of the said electrolyte is evolved, the steps comprising selectively condensing and separating from said effluent gas a mixture of aluminum chloride and at least one substance selected from the group consisting of alkali metal halides and alkaline earth metal halides, and subsequently desubliming reMaining aluminum chloride from the residual gaseous effluent.

Claim 13

In a process for electrolysis of aluminum chloride dissolved in a molten metal halide electrolyte containing at least one halide from the group consisting of alkali metal halides and alkaline earth metal halides to produce aluminum at above 660*C, wherein effluent gas containing gaseous aluminum chloride and at least one gaseous halide of the said electrolyte is evolved, the steps comprising selectively condensing and separating from said effluent gas a mixture of aluminum chloride and at least one substance selected from the group consisting of alkali metal halides and alkaline earth metal halides, and subsequently desubliming reMaining aluminum chloride from the residual gaseous effluent.

Claim 14

In a process for electrolysis of aluminum chloride dissolved in a molten metal halide electrolyte containing at least one halide from the group consisting of alkali metal halides and alkaline earth metal halides to produce aluminum at above 660*C, wherein effluent gas containing gaseous aluminum chloride and at least one gaseous halide of the said electrolyte is evolved, the steps comprising: a. selectively first condensing and separating from said effluent gas at a first predetermined temperature a mixture of aluminum chloride and at least one substance selected from the group consisting of alkali metal halides and alkaline earth metal halides; b. subsequently condensing remaining aluminum chloride from the residual gaseous effluent at a second predetermined temperature; and c. recovering chlorine from the residual gaseous effluent subsequent to said two condensing steps; whereby aluminum chloride, alkali metal halide, alkaline earth metal halide, and chlorine values may be recovered from said effluent for subsequent use.

Claim 15

In a process for electrolysis of aluminum chloride dissolved in a molten metal halide electrolyte containing at least one halide from the group consisting of alkali metal halides and alkaline earth metal halides to produce aluminum at above 660*C, wherein effluent gas containing gaseous aluminum chloride and at least one gaseous halide of the said electrolyte is evolved, the steps comprising: a. selectively first condensing and separating from said effluent gas at a first predetermined temperature a mixture of aluminum chloride and at least one substance selected from the group consisting of alkali metal halides and alkaline earth metal halides; b. subsequently condensing remaining aluminum chloride from the residual gaseous effluent at a second predetermined temperature; and c. recovering chlorine from the residual gaseous effluent subsequent to said two condensing steps; whereby aluminum chloride, alkali metal halide, alkaline earth metal halide, and chlorine values may be recovered from said effluent for subsequent use.