The Influences Of Refroming Ways On Performance Of SOFC And SOFC-CHP Systems Both Fueled By Nature Gas

In contrast with tranditional power,making use of hydrogen to generate distributed electricity for energy supply exhibits great advantages.Much extensive research and attention have been attracted for SOFC-CHP systems which powered by SOFC fueled by natural gas as a kind of new distributed power generation.In this paper,condition optimization for steam-methane reforming?SMR?was done to confirm the composition of synthesis gas after SMR reaction firstly.Then a 3D model of SOFC single cell was established based on the COMSOL multiphysics software,and the output performance of the single cell between internal reforming?IR?and external reforming?ER?have been investigated based on this software too.At the same time,SOFC single cell was tested in the lab with reforming gas or methane,the performances were compared with the simulation results.Finally,an 1 kW-class ERSOFC-CHP system and an 1 kW-class IRSOFC-CHP system was developed based on Aspen plus coupling SOFC electrochemistry model,respectively,and the comparative performance of two kinds of system was done respectively too.The results are as follows:?1?The suitable SMR reaction condition is:reaction temperature is 973 K¹023 K,space velocity is 2400 h^-1,and steam carbon ratio is 3⁴.The composition of synthesis gas at this condition is identified based on experiment:50%H₂,3%CO,1%CH₄,6%CO₂,40%H₂O,and it would be the internal reforming gas composition for SOFC simulation in the next steps.?2?The results of SOFC simulation show that:power density and energy utilization of IR-SOFC is higher than those of ER-SOFC,but the fuel utilization of IR-SOFC is lower;The temperature of IR-SOFC change more dramatically than that of ER-SOFC and the maximum temperature gradient of IR mode is equal to 5500 K?m^-1 at the anode inlet,because there is a strong endothermic SMR reaction occurred mainly in the region;The closer near the current collector the higher current density,and the current density decrease along the fuel flow direction;thermodynamics carbon deposition do not occur on anode side of ER-SOFC,whereas it occurs as a result of CH₄ thermal decomposition reaction with IR-SOFC,and the carbon activity is more than 270 near the anode inlet.?3?The results of SOFC test show that:performance of SOFC improves with the increasing gas flow rate on both anode and cathode,and the better performance of IR-SOFC is reached when the steam carbon ratio is 4;The performance of IR-SOFC is better than that of ER-SOFC at 1073 K,but performance of both IR-SOFC and ER-SOFC is lower than the standard level.?4?Through the SOFC-CHP simulation based on the Aspen plus software,it's found that as the fuel flow rate increases,the system power increases but the system efficiency decrease.The net DC electric power(P_DC,net)and net cogeneration thermal power(Q_net)of IRSOFC-CHP system is higher than those of ERSOFC-CHP system in the range of120 W¹40 W and 110 W²00 W,respectively.The net cogeneration heat power(Q_net)and the system thermal efficiency(?_sys,Q)of IRSOFC-CHP system is higher than those of ERSOFC-CHP system when steam carbon ratio exceed 2.As the steam carbon ratio increases,the system thermal load and the thermal losses increases,leading to decreasing of the system total recycle efficiency.Increasing the fuel utilization of SOFC stack is good for increasing the P_DC,net and system DC electric efficiency?_sys,ele.The?_sys,ele of IRSOFC-CHP system is always higher than that of ERSOFC-CHP system about 5%⁷%.