Study On Acid Corrosion And Experimental Design Of Acid Corrosion Process In The Initial Condensation Zone Of Supercritical H₂O/CO₂ Mixture Turbine

Supercritical H₂O/CO₂ mixed working fluid thermal power polygeneration is an innovation of green coal production and clean and efficient utilization,and supercritical mixture turbine is the key equipment to complete the thermal-power conversion.In the supercritical H₂O/CO₂ mixture turbine initial condensation zone,the problem of carbonic acid corrosion has a great impact on the safe and stable operation of the turbine,so it is very important for the simulation analysis of the carbonation corrosion process in the initial condensation zone.Firstly,the two mechanisms of direct reduction of carbonic acid and buffering effect are summarized,and the follow-up problem research is determined by the buffering effect corrosion mechanism.Then,the carbonation corrosion calculation models of De Waard model and BP?Cassandra?model were sorted and briefly described,and the carbonation corrosion calculation software CCRCS was developed based on the calculation model.In the study of the mechanism of the influence of carbonic acid corrosion factors on the corrosion rate,first of all,the CCRCS software was used to calculate the carbonic acid corrosion and plot analysis to give the relationship between the corrosion rate and its influencing factors.The corrosion rate of different corrosion models varies with influencing factors,but the general trend and law are the same.Then use COMSOL Multiphysics software to establish a one-dimensional boundary layer model at the microscopic scale for numerical simulation of carbonic acid corrosion.The corrosion simulation results are compared with the classic corrosion model,and the influence mechanism of the influencing factors on carbonic acid corrosion is given.Then,the last four stages of the 50,000KW supercritical H₂O/CO₂ mixture turbine designed by the research group were modeled and numerically simulated.Through calculation,the distribution of the number of water vapor droplets in the last four stages of the model,as well as the parameters of the pressure on the surface of each blade in the low pressure stage,the density of condensed water,the temperature of the condensed water,and the friction speed of the blade wall surface are given.And the last four stages of rotor and static blade corrosion calculation parameter calculation points of the model were extracted as the environment in which carbon dioxide corrosion occurred,which provided a basis for the subsequent calculation of turbine blade corrosion.By extracting the corrosion rate of the calculated points on the blade,It is analyzed that for the static blade,the positions of the blade that are easy to corrode are:the position of the leading edge,the position of the trailing edge,the location of the Hub,the Shroud,and the position of the pressure surface near the leading edge.For the rotor blades,the locations of the blades that are easy to corrode are:the position of the trailing edge,the location of the Hub near the trailing edge,the location of the Shroud,the position of the pressure surface and the suction surface near the trailing edge.Combined with the existing corrosion protection technology,the corresponding corrosion protection suggestions are proposed according to the characteristics of different positions of the blade.Finally,the preliminary design of the corrosion experiment plan was completed,which provided guiding suggestions for further in-depth study of the carbon dioxide corrosion law in the initial condensation zone of the supercritical H₂O/CO₂ mixture turbine.