Characteristics Of Corrosion Product Migration In Steam-Water System Of Supercritical Power Plant

With the rapid development of the energy economy,the continuous improvement of the capacity and parameters of coal-fired thermal power generating units has brought severe challenges to the heating surface materials of the steam-water system,and higher requirements have been put forward.In particular,the safety,economic and life issues of the heating surface of the steam-water system in the supercritical power station are particularly sensitive to the migration behavior of corrosion products,such as low-temperature corrosion,corrosion product deposition,high-temperature oxidation,and scale peeling.In addition to the steam-water parameters of the unit during operation,the influencing factors of these processes are also closely related to the variation of the concentration of corrosion products caused by the mixed flow of steam and water formed by the steam extraction cycle.Therefore,in order to realize the research on the migration process,further grasp the distribution law of corrosion products in the steam-water circulation flow,and control the operation state of the unit in real time,we will give a In-depth research on the migration characteristics based on the fluid network theory and Kirchhoff's law on the corrosion products in the multi-cycle network.:Firstly,based on the comparison idea,network topology and fluid network analysis method,a corrosion product migration dynamics analysis method was proposed.The mechanism of corrosion product propagation dynamics,including self-reaction kinetics and branch influence dynamics,was analyzed.There is no reverse deterioration for the unidirectional network branch,but the reverse effect of the loop will occur for the loop network.This effect is not only related to the corrosion product itself,but also to the distribution of the carrier medium in the network.Then,the mathematical model of corrosion product migration is established,including the governing equation of the migration process of the corrosion products,the physical model of the fluid network of the steam-water system and the calculation method of the fluid network.The model is established based on Kirchhoff's first law to divide the system network into nodes,and divides 30 key nodes to establish the relationship between nodes.Based on the fluid network disturbance theory,a matrix algorithm is introduced,and the elementary reaction dynamics equation on the node is used as the disturbance matrix.Finally,the calculation results of the model are analyzed based on theoretical calculations,and compared with the field measured data.Firstly,the calculation result of the model can match the change trend of the test results very well.According to the calculation results,the position with the highest corrosion rate is 2#high and hydrophobic,because the concentration of corrosion products in 2#high-hydrophobic is low,forming a high The concentration potential is calculated,and at the same time,a higher mass transfer rate is formed because the dissolution rate and diffusion rate of the oxide film at this temperature.The highest deposition rate of corrosion products is around 41%and is mainly deposited in the superheater.In the first cycle,about 61.5%of the corrosion products participate in the next cycle,but are not eliminated by the finishing process.Therefore,the data of the engineering point actually contains the corrosion products that are long-term in the system,and the corrosion products can be reversed by the model.Source and contribution ratio.The establishment of the model and the analysis of the calculation results provide a theoretical basis for further realizing the safety and life assessment of the steam-side equipment.