Optimization of sonochemical ammonia synthesis in non-Newtonian fluids

This study investigates the theoretical energy intensity of ammonia production via sonochemical reactions in non-Newtonian test fluids. A single, freely oscillating microbubble containing nitrogen and hydrogen is modelled using the Keller–Miksis equation, the first law of thermodynamics, and a detailed reaction mechanism. The goal is to assess whether modifying fluid properties can improve the energy intensity compared to conventional methods. Key parameters—including bubble size, ambient pressure, gas composition, and rheological properties—are varied systematically. The total energy input includes bubble expansion work, hydrogen production via electrolysis, and gas compression energy. The lowest energy intensity achieved is 682.6 GJ/t, which is 17.5 times higher than the Haber–Bosch process using renewable hydrogen. Compared to previous studies in water, a 5.3% improvement is observed, attributed primarily to the increased sound speed. The non-Newtonian rheology had only minor influence, suggesting that future efforts should focus on optimizing acoustic parameters and fluid compressibility rather than rheological properties.