What is high-temperature plasma?
Plasma is an energised gas. In an arc-heated plasma system, electrical energy is coupled into a process gas via an electric arc. This energy input causes dissociation and ionisation, creating plasma. The heated gas leaves the burner as a concentrated high-temperature jet, delivering process heat and—depending on the gas and operating conditions—chemically active species.
At its centre, the generated plasma jet reaches temperatures of up to 20,000 °C; the average temperature of the exiting gas stream is 2,000–6,000 °C. This gas stream acts as an effective heat-transfer medium, without the need for oxygen or combustion. In addition, reactive radicals from the working gas can enable chemical reactions—for example, the formation of HF from CFCs when water vapour is used as the plasma gas.
Technical specifications
Parameter
Value
Electrical power
10–150 kW (higher power ratings in development)
Working gases
Ar, N₂, air, water vapour, CO₂, H₂, CH₄, NH₃
Process gases and their applications
Water vapour as plasma gas
Compared with typical plasma gases, water vapour is a very cost-effective process gas. Its chemical properties support a range of processes: water-vapour plasma torches are used primarily for CFC disposal, plasma pyrolysis and syngas conditioning, as well as a source of process heat.
Hybrid plasma torch (methane/hydrogen + oxygen)
Using oxygen as the plasma gas and adding methane or hydrogen produces a combination of electrical and chemical heat, which serves as a high-temperature heat source.
Power range currently available: up to 50 kW electrical and up to 70 kW chemical output. One example of an application is heating molten glass.
Methane as a plasma gas
Methane pyrolysis produces turquoise hydrogen and black carbon. Green hydrogen (electrolysis) requires around three times as much electricity per kilogram of H₂ as turquoise hydrogen produced by plasma methane pyrolysis. The system scope of a 100 kW setup includes a plasma burner using methane as the plasma gas, peripherals installed modularly in a container, a high-temperature reactor, gas cooling and a dry filter for carbon separation. At its core is a 100 kW hollow-cathode burner using 100% methane as the plasma gas. The carbon is a valuable by-product that can, for example, be used in battery production or steelmaking.
Nitrogen as a plasma gas
Burn-and-wet technology is established in the semiconductor industry for exhaust gas treatment. It uses natural gas burners to combust CFC-containing gases generated during chip production. To decarbonise these processes, nitrogen plasma burners are expected to replace natural gas burners in the future. In recent years, the first systems have been industrially qualified for use in production; the burners’ electrical input power ranges from 5 to 30 kW.
CO₂ as plasma gas
CO₂ can be used as a heat-transfer medium in processes where it is circulated in a closed loop to avoid emissions (e.g. in the cement industry). Tested, among other applications, with a 7 kW CO₂ plasma burner and a 50 kW CO₂ plasma burner in a reactor for cement production.
Ammonia as a plasma gas
These plasma sources can be used to break down ammonia into nitrogen and hydrogen.