Investigation on a Supercritical Water Gasification System with CO_(2)as Transporting Medium

As a benign energy vector,hydrogen has been discussed for a long time.Supercritical water gasification was one of good ways to produce hydrogen.However,supercritical water gasification system with H_(2)O transporting was energy consuming in the process of heating due to the high specific heat of H_(2)O.A new supercritical water gasification system was established in this paper with supercritical CO_(2)as medium instead.Phenolic plastics were used as the sample transported by CO_(2).Production yields,energy flow and exergy flow of the system were collected and the influence of temperature,pressure,gasification concentration and transporting concentration was investigated.Mass flow of H_(2)O input into the reactor was 1000 kg/h.The typical condition was as follow:temperature 923.15 K,pressure 23 MPa,and the mass ratio of water,sample and transporting medium was 100:9:9.Yield of H_(2),CH4,CO and CO_(2)at this condition was 8.1 kg/h,39.6 kg/h,6.6 kg/h and 137.5 kg/h,respectively.Similar system with H_(2)O transporting was used to compare with the supercritical CO_(2)transporting system and proved that system with CO_(2)transporting could reduce the loss of both energy and exergy while the reduce of each gas production yield was less than 0.1 mol/mol.