Thermodynamic performance analysis of ammonia synthesis systems based on different electrolyzers

To avoid greenhouse gas emissions, reduce the dependence of the traditional ammonia synthesis process on fossil energy, and achieve a low-carbon and sustainable transformation of the ammonia synthesis process, the electrolyzer-based ammonia synthesis system has gradually attracted people's attention. This paper compares and analyses the thermodynamic performance of the synthetic ammonia system when operating with different electrolyzers: alkaline water electrolyzer (AWE), proton exchange membrane electrolyzer (PEMEC), and solid oxide electrolyzer (SOEC). The results show that the energy efficiency of the synthetic ammonia system based on AWE, PEMEC and SOEC is 54.99%, 59.94%, and 77.19%, respectively, which is in positive correlation with the hydrogen production efficiency of the electrolyzer. Meanwhile, by comparing the heat integration of different synthetic ammonia systems, it is found that the heat integration processes of synthetic ammonia systems based on PEMEC and AWE are identical because the excess heat from the low-temperature electrolyzer is directly discharged to the environment through cold utilities, which means that the synthetic ammonia system can adopt the PEMEC and AWE collaborative hydrogen production solution to achieve a trade-off between system flexibility and economy. The high-temperature electrolyzer (SOEC) exhibits the advantage of high thermodynamic compatibility with ammonia synthesis reactions, enabling more efficient utilization of system waste heat and further enhancing the overall system efficiency.