Performance and design data are presented for energy conversion of biomass in modified HAT cycles in a combined heat and power plant. The computations are performed by the heat balance software GateCycle and based on a gas turbine LM 2500 from General Electric. The processing of biomass includes drying of wet biomass fuel, gasification at atmospheric pressure, gas cooling and wet gas cleaning of the product gas and gas compression to pressure requirement of the gas turbine combustion system.

A further problem in biomass fuelled power systems and humidified gas turbine (HAT cycle) is to accomplish stable combustion in a gas turbine combustor with humidified air along with product gas having low heating value. To avoid the problem, the air humidification is performed only on a fraction of the compressed air stream, which makes it possible to use dry air (unhumidified air) for the combustion in the primary zone and humidified air for diluting and cooling. It is shown that part-airflow humidification gives similar or slightly improved performance (specific power and cycle efficiency) and also reduces the need of area for heat exchanging and recuperating.

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