Process and integrated plant for the treatment of the carbon oxides formed in the production of aluminum

A process for the treatment of an offgas stream comprising carbon oxides, the process comprising:

• purifying and/or conditioning at least a substream of the offgas stream comprising carbon oxides, to produce a gas stream comprising carbon oxides,
• reacting the gas stream comprising carbon oxides with hydrogen and reducing carbon oxides to carbon monoxide and/or methane, to produce a synthesis gas stream;
• or mixing the gas stream comprising carbon oxides with a hydrogen stream, to produce a mixed stream composed of carbon oxides and hydrogen, and
• subsequently passing the synthesis gas stream or the mixed stream composed of carbon oxides and hydrogen to utilization in a chemical or biotechnological reaction;
• wherein the offgas stream comprising carbon oxides is formed in a plant for producing aluminum by electrolytic reduction of aluminum oxide in a melt using at least one anode composed of a carbon-comprising material,
• wherein the offgas stream comprises the carbon oxides due to the electrolytic reduction of the aluminum oxide by carbon, and
• wherein at least a further substream of the offgas stream comprising carbon oxides is recirculated to the plant for producing aluminum.

An integrated plant, comprising:

• an electrolysis apparatus for production of aluminum by melt-electrolytic reduction of aluminum oxide, using at least one anode composed of a carbon-comprising material,
• at least one device for purification and/or conditioning of an offgas stream from the electrolysis apparatus, and
• at least one reactor for reaction of the offgas stream with hydrogen to form a synthesis gas and/or to form methane, and/or an apparatus for mixing the offgas stream with hydrogen;
• for subsequent utilization in a chemical or biotechnological plant to produce methanol, at least one alcohol, and/or at least one other chemical product of value,
• wherein the integrated plant comprises at least two independent conduits, and
• wherein a first offgas stream which has been cooled in an apparatus for heat exchange can be conveyed by the first conduit and, independently thereof, a second uncooled offgas stream can be conveyed directly from the electrolysis apparatus into the at least one device for purification and/or conditioning.