Research On A Horizontal Square Cyclone And Its Application In A CFB Boiler

In the thesis, a novel gas-solid cyclone separator applied for aged boilerrevamping with circulating fluidized bed (CFB) technology--horizontalsquare cyclone was studied with experimental and theoretical method. Then its application in a revamping project was researched.First a review was carried out on the main types, performance parameters and influencing factors of cyclone, on this base the performance and characteristics of main cyclones were compared. After analyzing some boiler retrofitting with circulating fluidized bed technology in different countries, four main types of CFB boiler used for boiler retrofitting and their suitable applications were summarized. Then the horizontal square cyclone was brought forward and its advantage on the separator arrangement was proved after comparing with normal cyclone on a pulverized boiler revamping project.The study about horizontal square cyclone includes three parts. The first is measuring its flow field with particle image velocemetry(PIV) system, the working process of horizontal square cyclone is visualized, and the instantaneous and average planar velocity distributions of three different planes are calculated with the gray distribution cross-correlation arithmetic. The second is building the characteristic experimental system and measuring the separation efficiency and pressure drop of horizontal square cyclone under different conditions. The results indicate that the cyclone has more than 90 % separation efficiency for particles larger than 100 m while pressure drop lower than 1000 Pa. The influence of some structure parameters to cyclone performance is experimented too and the optimal values of some parameters are obtained. A simple grade efficiency prediction model applying boundary separation theory is built and a design method about horizontal square cyclone is offered based on the previous research. The third is simulating the turbulent gas-solid flow of horizontal square cyclone, the Reynolds Stress Model (RSM) is used to simulate gas-phase flow and the Discrete Phase Model (DPM) is used to trace a moving track of solid particle. The velocity field, pressure field, turbulent intensity field and moving track of particle of different diameters are calculated and the result is compared with the previous experimental data. The performance of horizontal square cyclone under hot condition is predicted with the model and more structure optimizations are researched with model.At last a project of revamping traveling grate boiler to circulating fluidized bed boiler is introduced. The advantage of horizontal square cyclone is proved throughthe scheme and economical comparison between horizontal square cyclone and normal cyclone. The revamping results show that boiler retrofitting with circulating fluidized bed technology is proved to be a good idea through analyzing the economical and social benefits of this project.