Exergy Analysis of a Syngas-Fueled Combined Cycle with Chemical-Looping Combustion and CO2 Sequestration

Abstract

Fossil fuels are still widely used for power generation. Nevertheless, it is possible to attain a short-and medium-term substantial reduction of greenhouse gas emissions to the atmosphere through a sequestration of the CO 2 produced in fuels' oxidation. The chemical-looping combustion (CLC) technique is based on a chemical intermediate agent, which gets oxidized in an air reactor and is then conducted to a separated fuel reactor, where it oxidizes the fuel in turn. Thus, the oxidation products CO 2 and H 2 O are obtained in an output flow in which the only non-condensable gas is CO 2 , allowing the subsequent sequestration of CO 2 without an energy penalty. Furthermore, with shrewd configurations, a lower exergy destruction in the combustion chemical transformation can be achieved. This paper focus on a second law analysis of a CLC combined cycle power plant with CO 2 sequestration using syngas from coal and biomass gasification as fuel. The key thermodynamic parameters are optimized via the exergy method. The proposed power plant configuration is compared with a similar gas turbine system with a conventional combustion, finding a notable increase of the power plant efficiency. Furthermore, the influence of syngas composition on the results is investigated by considering different H 2 -content fuels.

Thermoeconomic evaluation of three proposals for the energy cogeneration unit powered by natural gas, biogas, or syngas

“…However, when converting the values of syngas to a mass or volume basis, it is seen that the heating value based on the mass of the selected syngas corresponds to approximately 4.1 MJ/ Nm 3 , which is within the general range of 3.25-7.2 MJ/ Nm 3 , as shown by [6]. Because the density of the syngas is not shown in [21], the mean of the densities present in the consulted literature was adopted as the appropriate value for the simulation. Table 5 presents the data on the fuels used in the simulation of the power generation units.…”

“…In the case of biogas, it was assumed that gas produced from residential waste or landfills was used, and the data were found on the corresponding websites for this fuel. For syngas, most studies focus on coal or wood sources, and therefore, fuel produced from wood waste was assumed to be used, as shown in [21]. The heating value and exergy of syngas are reported on a molar basis, unlike other fuels.…”

“…Table 5 presents the data on the fuels used in the simulation of the power generation units. The chemical compositions and properties of natural gas, biogas, and syngas were collected from [7,21,22], respectively. The exergy of natural gas shown in Table 5 was calculated from the heating value reported by the distributor and from an φ value equal to 1.04, as shown in [23].…”

Numerical Investigation of Nickel–Copper Oxygen Carriers in Chemical-Looping Combustion Process with Zero Emission of CO and H2

“…In general, there are three distinct areas in the CLC systems. − First, the techno-economic evaluation is an important branch for extension of CLC technology. According to the comparison with conventional combustion, the CLC system displayed a significant improvement in the energy efficiency . Luo et al analyzed the energy and CO 2 capture efficiencies between the coal direct CLC and the coal gasification CLC systems with the one-dimensional simulation software, and a higher efficiency was observed in the former system.…”