Motion and Separation Characteristics of Oxide Scale Particles in High Temperature and High Pressure Steam Pipe

To completely solve the problems, such as the erosion damage of steam turbine blades, the valve jam, and the blockage of the extraction and drainage system caused by the oxide particles falling off the boiler piping system, a systematically numerical simulation analysis of the steam-particle two-phase flow in the steam pipe is carried out based on the prototype of main steam pipe of an ultra-supercritical steam turbine generator unit. The effects of particle size, steam parameters and elbow curvature radius on the motion behavior of oxide scale particles are explored. Then an elbow particle separator is designed by using the original elbow structure in main stream pipe, and the separation characteristics, pressure loss and thermal system economy are calculated and analyzed. The results show that after the oxide scale particles enter the steam pipe elbow, particles of all sizes gradually tend to concentrate on the pipeline pressure surface under the action of centrifugal force. The larger the particle size, the greater the curvature radius of the elbow, the lower the steam parameter, the more concentrated the oxide scale particles get on the elbow outlet cross-section. When the optimal steam extraction ratio M equals to 0.50%, separation efficiency of the oxide scale particles above 100 μm is more than 90% by utilizing the elbow particle separator, and the pressure loss of the separation device to the main steam is about 21 kPa. A scheme of purifying the separated steam-particle two-phase mixture and transporting it to the highest parameter high-pressure heater for recycling is proposed. The effect of particle separation and steam recovery processes on the heat consumption and power of the unit in different steam extraction ratios is less than 0.2%. © 2022, Editorial Office of Journal of Xi'an Jiaotong University. All right reserved.