Study on Hydrogen Production by Supercritical Water Gasification of Unsymmetrical Dimethylhydrazine under Multi-Parameters

Unsymmetrical dimethylhydrazine (UDMH) is very toxic and hard to decompose in traditional ways. In this paper, the gasification of unsymmetrical dimethylhydrazine (UDMH) in supercritical water was studied in a batch reactor under different conditions. The hydrogen production process of supercritical water gasification of UDMH in metal containers is a multiphase reaction process. The effects of reaction temperature, alkaline catalysts, residence time, and oxidation on gasification were systematically studied. COD and ammonia nitrogen of the residual liquid were tested. Results showed that the maximum molar fraction and yield of hydrogen were 87.0% and 97.9 mol/kg, respectively, with KOH at 600 °C, 23 MPa. The COD removal efficiency in relation to alkaline catalysts was in the following order: NaOH > Na₂CO₃ > KOH > K₂CO₃. The highest COD removal efficiency (up to 95%) can be obtained at the temperature of 600 °C, 23 MPa with NaOH as the catalyst, and a residence time of 20 min. Ammonia nitrogen can be decreased by adding an oxidant. The COD and ammonia nitrogen of the residual liquid can meet the requirement of the Chinese emission standard of water pollution for space propellants. In addition, the organic compounds formed under different conditions were also identified.