A system like that shown in Figure 1 has been analysed in previous papers [1, 2] considering a gas turbine or an internal combustion engine as a power unit. In this paper the option to use high temperature fuel cells is considered. The goal of the system is to obtain valuable electric power and valuable fuel starting from renewable variable electric power, biomass and/or wastes. A simulation has been carried out using AspenONE® v8.4. The biomass is lignocellulosic and therefore the processor is a gasifier. However other kinds of biomass and other processors can be suitable. An electrolyser uses exceeding power from renewable energy sources to generate hydrogen and oxygen and the oxygen is used as a gasifying agent for the biomass processor, in such a way that syngas contains an almost negligible amount of nitrogen. The goal is to obtain from the power unit an exhaust gas composed almost completely by water and carbon dioxide so that it is easy to separate the carbon dioxide and send it to the Sabatier process. Usually the anodic exhaust of a high temperature fuel cell is burnt together with the cathodic exhaust. In this case there are two possible options: to use air at the cathode and oxygen to burn the anodic exhaust, or to use directly oxygen at the cathode. The choice depends not only on the efficiency gain, but also on the possibility to sell the oxygen. Moreover it is particularly interesting the case of Molten Carbonate Fuel Cells because the availability of oxygen and carbon dioxide allows to feed the cathode with an almost perfectly stoichiometric oxidant. Table I reports the power outputs. Chemical power is the HHV of the substitute of natural gas produced. Electric power is the sum of the power produced by the fuel cell and the expanders. Thermal power is the power recoverable at a temperature higher than 100 °C (see Fig.2 for cumulative cooling curves of gases). Taking into account chemical (HHV) and electric inputs (biomass and electrolysis) and outputs, the efficiency is close to 0.57 for both cases. Thermal power available corresponds to about 0.16 of total power inputs.

Cogeneration of power and substitute of natural gas using high temperature fuel cells

G. Spazzafumo
2017

Abstract

A system like that shown in Figure 1 has been analysed in previous papers [1, 2] considering a gas turbine or an internal combustion engine as a power unit. In this paper the option to use high temperature fuel cells is considered. The goal of the system is to obtain valuable electric power and valuable fuel starting from renewable variable electric power, biomass and/or wastes. A simulation has been carried out using AspenONE® v8.4. The biomass is lignocellulosic and therefore the processor is a gasifier. However other kinds of biomass and other processors can be suitable. An electrolyser uses exceeding power from renewable energy sources to generate hydrogen and oxygen and the oxygen is used as a gasifying agent for the biomass processor, in such a way that syngas contains an almost negligible amount of nitrogen. The goal is to obtain from the power unit an exhaust gas composed almost completely by water and carbon dioxide so that it is easy to separate the carbon dioxide and send it to the Sabatier process. Usually the anodic exhaust of a high temperature fuel cell is burnt together with the cathodic exhaust. In this case there are two possible options: to use air at the cathode and oxygen to burn the anodic exhaust, or to use directly oxygen at the cathode. The choice depends not only on the efficiency gain, but also on the possibility to sell the oxygen. Moreover it is particularly interesting the case of Molten Carbonate Fuel Cells because the availability of oxygen and carbon dioxide allows to feed the cathode with an almost perfectly stoichiometric oxidant. Table I reports the power outputs. Chemical power is the HHV of the substitute of natural gas produced. Electric power is the sum of the power produced by the fuel cell and the expanders. Thermal power is the power recoverable at a temperature higher than 100 °C (see Fig.2 for cumulative cooling curves of gases). Taking into account chemical (HHV) and electric inputs (biomass and electrolysis) and outputs, the efficiency is close to 0.57 for both cases. Thermal power available corresponds to about 0.16 of total power inputs.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11580/66026
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