A Combined Power Plant Fueled by Syngas Produced in a Downdraft Gasifier

Abstract

In this paper different gas-steam combined-cycles fueled by syngas produced in a local downdraft gasifier, are analyzed. At first, the downdraft gasifier model is briefly described, where waste biomass is transformed into syngas, which can be used more efficiently than the original solid biomass to generate useful power, and can be transported much more easily. The gasifier model is able to estimate, with good approximation, the composition of the produced syngas, taking separately into account the biomass drying and the pyrolysis, oxidation and reduction processes. The gasifier operates at ambient pressure using air as gasification agent and biomass as input. Among others, pomace has been considered, since, in Italy (where the plant is supposed to be located) there are many regions, like Apulia, where this biomass is largely available. Three different plant configurations have been proposed and compared in terms of overall performance. The first two, named REXC (Regenerative cycle with EXternal Combustor) and CR (Conventional Regenerative cycle), burn the syngas in an internal combustor, whereas the third one, named SyEXC (Syngas External Combustion), considers an externally fired configuration for the syngas combustion. In the REXC cycle, a secondary external combustion system, fed by cellulosic biomass, is connected to a heat exchanger in order 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 primary internal combustion chamber, where a defined quantity of syngas reacts with the compressed air. The turbine exhaust gas (TEG), before going back into the external combustion, partially transfers its enthalpy content to a Heat Recovery Steam Generator (HRSG) of a bottoming Rankine cycle. The second plant configuration (CR cycle) is characterized by a main internal combustor fueled by the produced syngas and implements a conventional regenerative process. The TEG is reheated by an externally fired combustion before flowing in the HRSG of a bottoming Rankine cycle. The last plant configuration (SyEXC) differs from the CR one only for the main externally fired gas turbine fueled by syngas, thus avoiding any costly cleanup operation and cooling.

Modeling and Experimental Study of a Small Scale Olive Pomace Gasifier for Cogeneration: Energy and Profitability Analysis

“…The gasification process is the conversion of a solid carbonaceous material, such as biomass, in a gaseous energy carrier (syngas) through a partial high temperature oxidation [12][13][14][15]. The syngas is composed by CO, CO 2 , H 2 , CH 4 , H 2 O, N 2 , other hydrocarbons such as C 2 H 4 and C 2 H 6 and further substances such as ash, coal particles, tar and oils.…”

Convective Effects in a Latent Heat Thermal Energy Storage

“…In the last decades, the efforts to maximize the efficiency in the energy production have been focused in the integration of different energy sources [1,2]. It follows the increase of renewable energy quote with respect to the conventional systems.…”

Assessment against Experiments of Devolatilization and Char Burnout Models for the Simulation of an Aerodynamically Staged Swirled Low-NOx Pulverized Coal Burner

“…However, further developments are required to design low emission pulverized coal burners, characterized by low or negligible NO x emissions and ashes with a very low carbon content. Several approaches have been developed in order to reduce the pollutant emissions in industrial furnaces: for instance, the introduction of the moderate and intense low oxygen dilution (MILD) technology in pulverized coal combustion to reduce the NO x emissions [8,9]; the pulverized coal oxy-fuel combustion, with CO 2 capture from flue gas [10][11][12]; the combustion of syngas derived from waste biomass [13][14][15]; the co-firing of biomass and coal [16][17][18]. The research activities in this field are strictly dependent on a good understanding of the coal combustion processes in industrial applications, even though data concerning coal combustion are mostly obtained in laboratory-scale experiments, operating far from the actual industrial conditions [19].…”