Gasification of rice straw in a fluidized-bed gasifier for syngas application in close-coupled boiler-gasifier systems

The feasibility and operation performance of the gasification of rice straw in an atmospheric fluidized-bed gasifier was studied. The gasification was carried out between 700 and 850 °C. The stoichiometric air–fuel ratio (A/F) for rice straw was 4.28 and air supplied was 7–25% of that necessary for stoichiometric combustion. Mass and power balances, tar concentration, produced gas composition, gas phase ammonia, chloride and potassium concentrations, agglomeration tendencies and gas efficiencies were assessed. Agglomeration was avoided by replacing the normal alumina-silicate bed by a mixture of alumina-silicate sand and MgO. It was shown that it is possible to produce high quality syngas from the gasification of rice straw. Under the experimental conditions used, the higher heating value (HHV) of the produced gas reached 5.1 MJ Nm−3, the hot gas efficiency 61% and the cold gas efficiency 52%. The obtained results prove that rice straw may be used as fuel for close-coupled boiler-gasifier systems.

► Rice straw was effectively gasified in an atmospheric fluidized-bed gasifier.
► The addition of MgO to the standard alumina-silicate bed avoided agglomeration.
► Stable flames were produced using 10–15% of the air needed for complete combustion.
► A high quality syngas was obtained: 10% H2, 18% CO, 4% CH4 and HHV of 5.1 MJ Nm−3.
► Gasification of rice straw produced a syngas low in tar content and CGE of 52%.