Research On Solar To Hydrogen And Hydrogen-cycle Power Generation Based On Separation Membrane

In the past two hundred years,human beings have consumed a large amount of fossil energy due to development needs,producing a large amount of carbon dioxide emissions.At a time when human society is facing the ecological crisis of global warming caused by the excessive emission of carbon dioxide,the development and utilization of hydrogen energy is receiving more and more attention worldwide.The current hydrogen energy is dominated by blue hydrogen from oil and natural gas.However,the production process of blue hydrogen has problems such as high reaction temperature and the production of certain amount of carbon dioxide.In terms of hydrogen energy utilization,although hydrogen fuel cells have the outstanding advantage of zero emission,the current high cost of hydrogen consumption makes it difficult to fully promote hydrogen fuel cell power generation systems from the economic aspect.Based on the above realistic problems in the development and utilization of hydrogen energy,this description conducts a series of studies for the major needs of hydrogen energy production and utilization in the future,and the main research contents and results are as follows:（1）Given the current problems of high temperatures and a certain amount of carbon dioxide byproducts in the production of blue hydrogen,a hydrogen production system of the dry reforming of methane integrating parabolic trough solar collector and Pd-Ag alloy hydrogen permeable membrane reactor is proposed in this description.In addition,to verify the effectiveness of the hydrogen permeation membrane reactor for improving methane conversion at 400°C,a 15-cm-long experimental system of hydrogen permeation membrane reactor was constructed.During the experiments,Ru/γ-Al₂O₃ doped with cerium oxide was used as the catalyst and water vapor purge gas was used to provide the driving pressure differenceΔP for hydrogen separation.The experimental results showed that the hydrogen separation pressure difference reached 108 Pa and 136 Pa at 400°C and 425°C,respectively,and the methane conversion also reached 20.27%and 30.00%,respectively,which are higher than the published studies so far.To explore the potential of a hydrogen permeation membrane reactor for improving methane conversion,a mathematical model was developed for the dry reforming of methane in a hydrogen permeation membrane.Calculations show that methane conversion of 99.10%can be achieved at a hydrogen separation pressure of 10^-5 bar at a reaction temperature of 400°C,but a membrane reactor length of 2861.62cm is required.Thermodynamic analysis（in the temperature range of 300-500°C）of the system proposed in this description shows that the system had the highest first-law thermodynamic efficiency and solar-to-fuel efficiency of 74.73%and 38.92%,respectively,at a reaction temperature of 500°C and a hydrogen separation pressure of10^-2 bar.The analysis of carbon dioxide emission reduction shows that this system can reduce carbon dioxide up to 6.26 kg/（m²·a）at 500°C with a hydrogen separation pressure of 10^-3 bar compared to the conventional fossil energy system.This study verifies the possibility and superiority of the proposed system for the production of high-purity hydrogen,which may have a greater prospect for future applications in energy and chemical industries.（2）In response to the current problem that hydrogen fuel cell power generation system is difficult to be fully promoted due to the high cost of hydrogen consumption,a hydrogen cycle cell based on oxygen permeation material YSZ is proposed in this description,and a three-dimensional multi-physical field model for the hydrogen cycle cell unit with four coupled physical fields of electrochemistry,fluid flow,matter transfer and heat transfer is established.The calculation results of the model show that there is almost no temperature gradient within the battery,which ensures the stability of the battery under long-time operating conditions.In addition,under the low discharge current density,the loss of the cell model output voltage mainly comes from the cathode and anode concentration polarization overpotential and cathode activation polarization overpotential,with the increase of discharge current density,the cathode and anode concentration polarization overpotential and cathode activation polarization overpotential gradually stabilize,and the cathode ohmic polarization and contact resistance polarization overpotential gradually become prominent.In order to reduce the concentration polarization overpotential and cathode activation polarization overpotential of the cell model,the cell model structure was optimized by increasing the cathode functional layer thickness and reducing the length in this study.At a temperature of 750°C,the peak power density of the optimized cell model was improved by about 82.1%when the anode hydrogen flow rate and cathode water flow rate were controlled to 400 sccm and 0.05 sccm at room temperature,respectively,and the voltage loss was reduced by about 14.6%when the discharge current was 200 A/m².（3）the experimental system of hydrogen cycle cell based on oxygen permeation membrane material YSZ is built in this description.The simulation results of the established multi-physical field cell model are verified by the IV curves obtained from the experimental tests,and the discharge performance of hydrogen cycle cell under different conditions is tested and analyzed.The simulation results are consistent with the experimental results,indicating that the multi-physical field cell model established in this description can describe the discharge process of hydrogen cycle cell accurately.The open-circuit voltage test of the cell showed that the open-circuit voltage could reach more than 1.0 V when high purity hydrogen and deionized water vapor were introduced,and the highest open-circuit voltage of 1.13 V was measured at 700°C.The current and power density tests of the cell showed that the system current density and power density showed a positive correlation with the experimental temperature,the hydrogen flow rate at the anode and the water vapor flow rate at the cathode,which was consistent with the simulation results.Moreover,the temperature has the greatest influence and the cathode water vapor flow rate has the least influence on the current density and power density of the cell.The impedance test results of the cell and the simulation results of the multi-physics field cell model show that this difference in the effect of different factors on the discharge performance of the cell is a result of the fact that the cathode electrochemical impedance is much larger than the anode electrochemical impedance and decreases substantially with increasing temperature.Within the range of experimental study conditions of this description,the peak power density of the cell reached a maximum value of 50.076 W/m² at 800°C,a hydrogen flow rate of 800 sccm and a water flow rate of 0.2 sccm,and even at 650°C,a peak power density close to 12W/m² was obtained.