Fuels and Combustion
A liquid/gaseous fuel containing hydrocarbons and high amount of sulphur is burnt with 40% excess air. The flue gas still contains large amount of carbon monoxide. This may be due to the

Low calorific value of the fuel
Lack of thorough mixing of fuel with air
High sulphur content in the fuel
Presence of large quantity of hydrogen in the fuel

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Fuels and Combustion
Producer gas containing least amount of tar is produced by the

Partial combustion of coal
Atmospheric pressure gasification of coal (e.g., in Kopper-Totzek gasifier)
High pressure gasification of coal (e.g. in Lurgi gasifier)
Partial combustion of large size (< 50 mm) coke

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