SIMULATION AND ANALYSIS OF A POLYGENERATION PLANT WITH THE INTEGRATION OF A CeO2/Ce2O3 CHEMICAL LOOPING

Climate changes, carbon depletion, greenhouse emissions and worldwide raising energy demand are becoming increasingly important problems. This opens the door to innovative and green pathways for electric/thermal power and fuels production. In the present study, a polygeneration plant integrated with a chemical looping fed by concentrated solar power for the production of electricity, heat, dimethyl-ether, methanol and syngas is analysed and discussed. The prime mover of the plant is the two-step chemical looping, operating at 1.2 bar and 900°C. The redox pair CeO2/Ce2O3 coupled with biomethane partial oxidation is chosen for its manifested advantages compared to other materials. The reduction reaction is endothermic, heat is provided by concentrated solar energy. The prime mover produces the fuel for the secondary devices of the plant: a Solid Oxide Fuel Cell (supplied by the syngas obtained in the reduction reaction) and a DME synthesis and distillation unit (supplied by the syngas obtained in the oxidation reaction). This last section of the system is integrated with a solar aided biomethane reforming reactor for syngas production at 800°C. SOFCs can only operate properly at base-load conditions, the main problem in the coupling of the FC with the solar syngas is given by the yearly, seasonally and daily intermittence of solar energy, which produces a discontinuous operation of the chemical looping and, consequently, a discontinuous production of syngas. This issue is solved under-sizing the SOFC compared to the CL; the surplus of syngas obtained from the reduction reaction during the operation of the chemical looping is stored in an AISI316L tank to be used in those periods of unavailability of solar energy. Thus, the SOFC unit operates continuously throughout the year, while the CL and DME synthesis and distillation unit, whose products are DME, methanol and syngas, only operate when there is a sufficient high irradiance irradiating the receiver-reactor of the CL. To have an idea of the possible yearly operating hours of the chemical looping, the seasonal daily average temperature curves of the receiver at the focus of the Dish system installed on the roof of the Energy Center are considered; when this receiver reaches a temperature higher/equal than 900°C, the CL is in on state. The obtained plant is sustainable, green and emission free because Carbon Capture and Utilization is applied through the use of the separated CO2 from the anodic exhausts of the SOFC and from the exhausts of the DME synthesis and distillation unit in the oxidation reactor of the CL and in the reforming reactor respectively. Another important output of the system is thermal power, which could be used for auto-consumption or for the supply of different users. The plant performance both under the presence of sunlight and not is studied through the software Aspen Plus v8.8. The electric power production of this system reveals to be much lower than another similar plant available in literature. Two attempts to increase the electricity production of the plant are made by decoupling the CL operation from the intermittence of solar energy and feeding the reduction reaction with the heat produced by the SOFC. However, these two other plants present the problem of sequestration of the CO2 because the lack of solar energy should be compensated through the oxyfuel combustion of biomethane. An experimental analysis of the CeO2/Ce2O3 chemical looping is also executed.