Method for operating a claus burner

A method for operating a burner used in a thermal step of a Claus process, wherein the burner includes at least one combustion air port, at least one oxygen port, and at least one fuel port, and

• wherein an air flow is fed to the at least one combustion air port, an oxidant flow is fed to the at least one oxygen port, and a hydrogen sulphide containing feed gas flow is fed to the at least one fuel port, comprising:
• feeding the oxidant flow which includes an oxygen flow of technical pure oxygen with an oxygen concentration of at least 90 vol. % to the at least one oxygen port and optionally feeding a second gas flow to the oxygen flow for providing a mixture of air and oxygen to the at least one oxygen port;
• determining whether the oxygen flow is below a pre-set minimum flow at the at last one oxygen port;
• and
• splitting the air flow if the oxygen flow is below the pre-set minimum flow into a main air flow fed to the at least one combustion air port, and a side air flow as the second gas flow to be combined with the oxygen flow for creating an oxygen-enriched side air flow fed to the at least one oxygen port.