INTEGRATED PROCESS OF PYROLYSIS, ELECTRODE ANODE PRODUCTION AND ALUMINUM PRODUCTION AND JOINT PLANT

Abstract

An integrated process contains the following steps of: (i) pyrolysis of hydrocarbons to carbon and hydrogen, (iia) removal of at least a part of the produced carbon in step (i) and at least partly further processing of said carbon into a carbon containing electrode, and (iib) removal of the hydrogen produced in step (i) and at least partly using said hydrogen for providing energy, preferably electric energy or heat, for the electrode production in step (iia). A joint plant is also useful, which contains (a) at least one reactor for a pyrolysis process, (b) at least one reactor for the production of electrodes for an aluminum process, (c) a power plant and/or at least one gas-fired burner, and optionally, (d) at least one reactor for the electrolysis for producing aluminum.

Claims

1: An integrated process, containing the following: (i) conducting pyrolysis of hydrocarbons, to produce carbon and hydrogen, (iia) removing at least a part of the carbon produced in (i), and at least partly further processing said carbon into a carbon containing electrode and optionally, using the carbon containing electrode for producing aluminum, (iib) removing the hydrogen produced in (i) and at least partly using said hydrogen for providing energy for the carbon containing electrode production in (iia) and/or for aluminum production.

2: The process according to claim 1, wherein at least part of the hydrogen produced in (i) is used to enrich natural gas in burners for providing energy.

3: The process according to claim 1, wherein 5 to 30% of natural gas, used as fuel, is replaced by the hydrogen produced in (i).

4: The process according to claim 1, wherein at least a part of the hydrogen produced in (i) is used for generating electricity to heat the pyrolysis of (i) and/or for smelting cells of the aluminum production.

5: The process according to claim 1, wherein 80 to 100 weight-% of the carbon produced in (i) is further processed into the carbon containing electrode.

6: The process according to claim 1, wherein a substrate is used for the pyrolysis of (i) as a fixed bed, a moving bed, a fluidized bed, or as entrained flow.

7: The process according to claim 1, wherein a density of the carbon produced in (i) is in the range of 1.6 to 2.3 g/cc.

8: The process according to claim 1, wherein a particle size of the carbon produced in (i) has at least 50% by weight greater than 0.5 mm.

9: The process according to claim 1, wherein a part of the hydrogen produced in (i) is exported to neighboring industrial plants for chemical processes needing hydrogen as a reducing agent.

10: The process according to claim 1, wherein the carbon containing electrode produced in (iia) is used for producing aluminum.

11: The process according to claim 1, wherein said carbon produced in (i) is further processed into a carbon containing anode.

12: A joint plant, containing: (a) a reactor for a pyrolysis process, (b) a reactor for a production of anodes for an aluminum process, (c) a power plant and/or at least one gas-fired burner, and (d) optionally, a reactor for an electrolysis for producing aluminum.

13: The process according to claim 1, further comprising: (iii) producing aluminum.

Description

EXAMPLES

Example 1

[0088] An aluminum smelter which historically averages 1.36 kWh/kg Al product on the anode baking step, supplied by direct combustion of natural gas, replaces 50% of its anode carbon with pyrolytic carbon. This gives direct reduction of 50% of the sulfur emissions from the smelting step. The methane pyrolysis produces an additional 0.07 kg of H2 and requires 0.88 kWh energy to perform the pyrolysis per kg of final Al production. Direct combustion of the Hydrogen byproduct is used to heat the pyrolysis step. Because the byproduct gasses with the hydrogen will be mostly methane, purification is not required if the hydrogen is used in combustion burners. The residual H2 after heating the pyrolysis reactor is used to heat the anode baking step, completely displacing the natural gas demand in baking and resulting in net reduction of 500 kg CDE (Carbon dioxide emissions) per metric ton of Al. The remaining excess 0.12 Nm3 of H2 per kg of Al and can sold or flared or used elsewhere in the system.

Example 2

[0089] As in Example 1, an aluminum smelter which historically averages 1.36 kWh/kg Al product on the anode baking step, supplied by direct combustion of natural gas, replaces 50% of its anode carbon with pyrolytic carbon. This gives direct reduction of 50% of the sulfur emissions from the smelting step. The methane pyrolysis produces an additional 0.07 kg of H2 and requires 0.88 kWh energy to perform the pyrolysis per kg of final Al production. Direct combustion of the Hydrogen byproduct is used to heat the pyrolysis step, and residual H2 is blended with natural gas for direct use in existing combined cycle power generation turbines. The resultant power is used to provide electrical power to the smelters. The total generated pyrolysis hydrogen displaces 15% by volume of the total natural gas. Hydrogen enrichment to 30% can be used with little or no modification to existing burners. This results in a direct reduction of 350 kg/metric ton Al CDE (CO2 emissions).

Example 3

[0090] As in Example 2, an aluminum smelter which historically averages 1.36 kWh/kg Al product on the anode baking step, supplied by direct combustion of natural gas, replaces 50% of its anode carbon with pyrolytic carbon. This gives direct reduction of 50% of the sulfur emissions from the smelting step. The methane pyrolysis produces an additional 0.07 kg of H2 and requires 0.88 kWh energy to perform the pyrolysis per kg of final Al production. The Hydrogen byproduct is blended with natural gas for direct use in existing combined cycle power generation turbines. The resultant power is used to provide electrical power to the pyrolysis reactor and the smelters. The total generated pyrolysis hydrogen displaces 20% by volume of the total natural gas. This results in a direct reduction of 170 kg/metric ton Al CDE (CO2 emissions).