Control The PH And The Diffusion Rate In Supercritical Water Of Thermodynamics Theory

Supercritical water (SCW) could be used in many chemical reactions and could bethe reaction medium and reactant, which has the great prospect of widespreadconcern.However, the SCW reactor corrosion limits its wide application in industry. Inthe supercritical state, SCW has a very high reactivity,and can be a good solvent formany compounds, but also a strong oxidant, hence SCW s strong corrosion leads tosignificantly shorten the life of the SCW reactor. So far, the impact of SCW reactorcorrosion mechanism is still not clear.This paper mainly studies Supercritical Water and compounds (HCl, NaCl) sdissociation and diffusion processes in SCW, in order to further explore the impact ofsupercritical water reactor corrosion factors. The paper is divided into two parts: Thefirst part is calculated the physical and chemical properties of water under differenttemperature and pressure by MD simulations and thermodynamic properties, includingwater dissociation constant (pKw), entropy, enthalpy, concentration, volume moleculargeometry and the diffusion of particles, in order to understand the corrosion of water,especially in the supercritical region of water corrosion; the second part is calculatedcompounds dissociationand diffusion in supercritical water by the MD simulations andthermodynamic properties, including pKa, concentration, volume, molecular geometrystructure and particle diffusion, in order to understand the corrosion of compounds inwater, especially in supercritical water, to determine the impact of s upercritical waterreactor corrosion factors.Experimental results show that: in25MPa,50MPa and100MPa, the512-particlesystem of the MD simulation data is consistent with experimental data, so the modelsystem of512particles can be proved to validate. As the pressure increases, themaximum value of pure water s pKw is moved to the high temperature zone and themaximum is reduced, acid-stage is reduced,leading to reducing container corrosion.With temperature increasing, the MSD of pure water is increased; it shows that thedissociation of water molecules diffusion coefficient is minimum in high pressure andlow temperature, and container corrosion is minimum. As the pressure increases,HCland NaCl of pKa s maximum is moved to the high temperature zone and the maximumis reduced, acid-stage is reduced,leading to the corrosion of the container to reduce.HCl and NaCl diffusion rate is increased with increasing temperature, little change withpressure increasing, which is consistent with the trend of the water molecules.