Energy-saving combination of N₂ production, NH₃ synthesis, and power generation

A novel integration of N₂ production, NH₃ synthesis, and power generation systems is designed to efficiently convert H₂ to NH₃. The integrated system employs the principles of exergy recovery and process integration to achieve high energy efficiency. The high-purity N₂ output by the N₂ production module is reacted with H₂ in an NH₃ synthesis module to produce NH₃. In addition, O₂-rich gas, which is a by-product, is utilized as an oxidant in the power-generation module. A single column is adopted in the N₂ production module, and the feed stream is split into two and fed to the middle and bottom of the column. In our tests with the N₂ production module, the two operating parameters of bottom-feed ratio and refed-stream ratio were evaluated in terms of the energy consumed, N₂ purity, and O₂ molar fraction in O₂-rich gas. Compared with previous studies on N₂ production systems, our N₂ production module can reduce energy consumption by about 43% (3.27 MW compared with 5.76 MW to produce 1 tmol-N₂ h⁻¹). In the NH₃ synthesis and power generation module, the two operating parameters of conversion rate per pass and purged-stream ratio are also evaluated. The calculation results show that a high conversion rate per pass and low purged-stream ratio increase the total energy efficiency, which includes NH₃ production efficiency and power generation efficiency. The highest total energy efficiency that can be achieved by the integrated system is 66.92%, which includes a NH₃-production efficiency of 66.69% and a net power generation efficiency of 0.23%.