A method can include reducing a silica starting material to produce a first quantity of at least metallurgical grade silicon and a second quantity of silica comprising elemental carbon doping, wherein the silica starting material is reduced in the presence of a carbonaceous reducing agent. A silica material can be a silica material as prepared according to the method.

A method can include reducing a silica starting material to produce a first quantity of at least metallurgical grade silicon and a second quantity of silica comprising elemental carbon doping, wherein the silica starting material is reduced in the presence of a carbonaceous reducing agent. A silica material can be a silica material as prepared according to the method.

A circular carbon process involves: a) reacting hydrogen and carbon monoxide to produce methane and water, b) decomposing methane into carbon and hydrogen, and c) using carbon as reducing agent and/or using carbon in a carbon-containing material as reducing agent, in a chemical process to produce carbon monoxide and a reduced substance. The methane produced in a) is used in b), the carbon produced in b) is used in c), and carbon monoxide produced in c) is used in a).

A circular carbon process involves: a) reacting hydrogen and carbon monoxide to produce methane and water, b) decomposing methane into carbon and hydrogen, and c) using carbon as reducing agent and/or using carbon in a carbon-containing material as reducing agent, in a chemical process to produce carbon monoxide and a reduced substance. The methane produced in a) is used in b), the carbon produced in b) is used in c), and carbon monoxide produced in c) is used in a).

Silica sand agglomerates for silicon metal production according to the present invention may be formed in the form of lumps by mixing clay, a liquid adhesive, and silica sand having a particle size in a certain range, and thus be maintained in shape during reduction in a high-temperature carbothermal reduction furnace to facilitate heat transfer and gas circulation.

Silica sand agglomerates for silicon metal production according to the present invention may be formed in the form of lumps by mixing clay, a liquid adhesive, and silica sand having a particle size in a certain range, and thus be maintained in shape during reduction in a high-temperature carbothermal reduction furnace to facilitate heat transfer and gas circulation.

A method for forming a porous silicon material can include forming a mixture of silicon, carbon, and an etchant element, solidifying the mixture, removing the etchant element to form pores within the silicon material. The porous silicon material can include a distribution of pores with an average pore diameter between about 10 nm and 500 nm, wherein the silicon particle comprises a silicon carbon composite comprising 1-5% carbon by mass, 1-5% oxygen by mass, and 90-98% silicon by mass.

A method for forming a porous silicon material can include forming a mixture of silicon, carbon, and an etchant element, solidifying the mixture, removing the etchant element to form pores within the silicon material. The porous silicon material can include a distribution of pores with an average pore diameter between about 10 nm and 500 nm, wherein the silicon particle comprises a silicon carbon composite comprising 1-5% carbon by mass, 1-5% oxygen by mass, and 90-98% silicon by mass.

An apparatus and a process for the production of high purity silicon from silica containing material such as quartz or quartzite, using a vacuum electric arc furnace, are disclosed.

An apparatus and a process for the production of high purity silicon from silica containing material such as quartz or quartzite, using a vacuum electric arc furnace, are disclosed.