Thermodynamic properties of dissociated steam

Abstract

Abstract. In connection with the development of hydrogen technologies and the generation of dissociated steam as a result of the oxidation of hydrogen in an oxygen environment, it became necessary to determine the calorific parameters of dissociated steam. In the existing tables, the caloric parameters of dissociated steam are presented at a reference temperature of 0 K. By contrast, the authors have developed tables of dissociated steam using a reference temperature of 0°C, within the pressure range 0.01-20.0 MPa and the temperature range 1250-4000 K, along with a system of equations for the industrial calculation of the properties of dissociated steam within the temperature range 1250-2300 K and pressure range 0.01-10.0 MPa, followed by a temperature range of 2200-3600 K. During the dissociation of steam, a mixture of eight components are formed including hydrogen H, oxygen O, radicals OH and HO2, molecules of hydrogen H2, oxygen O2, steam H2O, and hydrogen peroxide H2O2. All existing tables of the properties of dissociated steam are based on a mixture of six components: H2, O2, OH, H, O, and H2O. For evaluate whether this is an oversimplification, the composition of the mixture comprising all eight components was calculated, taking into account additional chemical reactions for the formation of НО2 and H2O2. At a pressure of 0.01 MPa, the maximum mole fraction of НО2 was 2.8•10 -5 at a temperature of 3000 K, and at a pressure of 10 MPa, the maximum mole fraction was 5•10 -5 at a temperature of 4000 K. The mole fraction of H2O2 was much lower. Thus at temperatures up to 3000 K, calculations of the properties of dissociated steam are restricted to six components.