A Gas-Steam Combined Cycle Powered by Syngas Derived from Biomass

In this paper, an innovative power plant, constituted by a gas turbine in combined-cycle fuelled by a synthesis gas (or syngas), produced in a local biomass gasifier, is analyzed. The plant is integrated with an external combustion sys- tem, fed by cellulosic biomass, connected to a heat exchanger able to increase the air temperature, as in a regenerative cycle. The combustion products pass through a primary heat exchanger placed in the external combustion system, heating the compressed air, which flows into the principal combustion chamber, where a defined quantity of syngas, coming from the gasifier, reacts with the compressed air in a combustion process. The expanded gas, at the tur- bine exit, before going back into the external combustor, passes through a Heat Recovery Steam Generator (HRSG1) transferring heat to the bottoming Rankine cycle. The superheated steam undergoes an expansion in a steam turbine providing electrical energy. The syngas used in the combustion chamber is produced by a gasification process, based on a Fast Internally Circulating Fluidized-Bed (FICFB). Heat is transferred from the hot syngas (coming from the gasifier) to water, through a second Heat Recovery Steam Generator (HRSG2), producing steam, which is introduced in the gasifier, reacting with the pomace biomass in order to produce the syngas; since the produced quantity of steam is not sufficient for the gasification process, a further quantity of steam is produced in an auxiliary boiler fed by diesel oil, or in different ways, as described in the paper. This kind of plant is especially interesting for regions, like Italian Apulia, where there is a wide culture diffusion for the use of biomass, particularly from olive products, where there are available technologies for use of pruning, virgin and exhausted pomace, and where there are the market conditions for the commercialization of these resources and the incentives available for their energy development. Finally, the overall plant performance is calculated, shown and discussed.