A raw gas collection system for collecting raw gas from a plurality of aluminium smelting pots is equipped with a plurality of branch ducts, each of which is arranged to channel a respective branch flow of raw gas from an aluminium smelting pot to a collection duct, which is common to and shared by the branch ducts. Each of said branch ducts is, near an outlet thereof, equipped with a curved section for aligning the branch flow with a flow direction of raw gas already present in the common collection duct, and a constriction for accelerating the branch flow through the branch duct outlet into the common collection duct. Furthermore, each of said branch ducts is equipped with a heat exchanger for removing heat from the respective branch flow of raw gas. The combined flow resistance of the constriction and the heat exchanger reduces the need for adjusting the respective branch flows using dampers, thereby reducing the power required to transport the raw gas.

A raw gas collection system for collecting raw gas from a plurality of aluminium smelting pots is equipped with a plurality of branch ducts, each of which is arranged to channel a respective branch flow of raw gas from an aluminium smelting pot to a collection duct, which is common to and shared by the branch ducts. Each of said branch ducts is, near an outlet thereof, equipped with a curved section for aligning the branch flow with a flow direction of raw gas already present in the common collection duct, and a constriction for accelerating the branch flow through the branch duct outlet into the common collection duct. Furthermore, each of said branch ducts is equipped with a heat exchanger for removing heat from the respective branch flow of raw gas. The combined flow resistance of the constriction and the heat exchanger reduces the need for adjusting the respective branch flows using dampers, thereby reducing the power required to transport the raw gas.

A process can utilize carbon oxides formed in the production of aluminum, by electrolytic reduction of aluminum oxide in a melt using at least one anode made of a carbon-comprising material. A pyrolysis of hydrocarbons, in particular methane or natural gas, is carried out in which pyrolysis carbon and hydrogen are formed. The pyrolysis carbon is used for the production of the at least one anode. The hydrogen formed in the pyrolysis of methane is mixed with carbon dioxide and/or carbon monoxide from the electrolytic production of aluminum, to produce a gas stream which is parsed to a further use. An integrated plant contains an electrolysis apparatus for producing aluminum by melt-electrolytic reduction of aluminum oxide, and also contains at least one reactor in which pyrolysis carbon and hydrogen are produced by pyrolysis of hydrocarbons.

A process can utilize carbon oxides formed in the production of aluminum, by electrolytic reduction of aluminum oxide in a melt using at least one anode made of a carbon-comprising material. A pyrolysis of hydrocarbons, in particular methane or natural gas, is carried out in which pyrolysis carbon and hydrogen are formed. The pyrolysis carbon is used for the production of the at least one anode. The hydrogen formed in the pyrolysis of methane is mixed with carbon dioxide and/or carbon monoxide from the electrolytic production of aluminum, to produce a gas stream which is parsed to a further use. An integrated plant contains an electrolysis apparatus for producing aluminum by melt-electrolytic reduction of aluminum oxide, and also contains at least one reactor in which pyrolysis carbon and hydrogen are produced by pyrolysis of hydrocarbons.

Apparatus and method for collecting and pretreating process gases produced in an electrolytic cell during aluminum production are disclosed. The apparatus comprises a collecting unit configured to draw off primary process gases from the electrolytic cell, for instance by drawing-off primary process gases from orifices purposely made over the electrolytic bath; and a pre-treating unit fluidly connected to the collecting unit and configured to receive a fluid bed of fluorinated alumina for pre-treating the primary process gases. The collecting and pre-treating units are within or immediately aside the electrolytic cell, in the potroom. The apparatus can be combine with a gas treatment center (GTC) located outside the potroom. Among other advantages, the technology allows collecting primary process gases directly at electrolytic bath level, separating primary process gases and hoodspace process gases to pretreat the primary process gases with alumina before the GTC, and using fluid bed reactors without filter bags.

Apparatus and method for collecting and pretreating process gases produced in an electrolytic cell during aluminum production are disclosed. The apparatus comprises a collecting unit configured to draw off primary process gases from the electrolytic cell, for instance by drawing-off primary process gases from orifices purposely made over the electrolytic bath; and a pre-treating unit fluidly connected to the collecting unit and configured to receive a fluid bed of fluorinated alumina for pre-treating the primary process gases. The collecting and pre-treating units are within or immediately aside the electrolytic cell, in the potroom. The apparatus can be combine with a gas treatment center (GTC) located outside the potroom. Among other advantages, the technology allows collecting primary process gases directly at electrolytic bath level, separating primary process gases and hoodspace process gases to pretreat the primary process gases with alumina before the GTC, and using fluid bed reactors without filter bags.

A method for preparing aluminum fluoride and aluminum oxide by decarburization and sodium removal of an aluminum electrolysis carbon residue is disclosed. The method includes: crushing the aluminum electrolysis carbon residue into fine particles not larger than 3 mm, adding decarburization agent into the carbon residue, mixing to obtain first mixture, adding the first mixture into a high-temperature furnace, conducting I-stage heating treatment in air atmosphere to obtain crude fluoride salt A; adding sodium removal agent into the crude fluoride salt A, mixing to obtain second mixture, adding the second mixture into high-temperature furnace, and conducting

II-stage heating treatment to obtain crude fluoride salt B; adding the crude fluoride salt B into stirring tank, adding industrial pure water, dissolving a sodium salt into water, and conducting solid-liquid separation to obtain precipitate C and sodium salt solution D; drying the precipitate C to obtain aluminum fluoride and aluminum oxide.

An apparatus and a method are useful for removing pollutants from process effluent gas produced by an electrolytic cell used in an aluminum production plant to produce aluminum. The apparatus and method use a flow control device to control alumina supply to an electrolytic cell and to a dry scrubber contact reactor.

An apparatus and a method are useful for removing pollutants from process effluent gas produced by an electrolytic cell used in an aluminum production plant to produce aluminum. The apparatus and method use a flow control device to control alumina supply to an electrolytic cell and to a dry scrubber contact reactor.

An electrolysis method comprising an electrolysis cell (4), which method uses at least one recirculating flushing medium (50, 60). The invention further relates to an electrolysis system, in particular for carrying out the electrolysis method.