Date of Graduation
Statler College of Engineering and Mineral Resources
Chemical and Biomedical Engineering
Circulating fluidized beds (CFBs) are used in many processes in the chemical industry to reduce pollution and increase efficiency. Optimization and control of CFBs are very important and require an accurate, real time, dynamic model to describe and quantify the process.;The present work focuses on modeling the transient behavior of large CFB units, whose flow characteristics were shown to yield C-shaped voidage profiles using cork as the fluidized material and air at ambient conditions.;The riser is modeled in two ways: (1) as a set of well-mixed tanks connected in series; (2) as a 1-D axisymetric cluster flow. The tanks-in-series model visualizes the riser as consisting of a series of well-mixed vessels. Using this method, the dynamic response time at different locations along the riser was estimated successfully. The cluster flow model assumes that gas and solids flows are unidirectional with no mixing in the axial direction, and the solids move upward in the riser as clusters. This model can be used to predict the smooth changes in voidage profiles for transient processes. The influence of exit is also considered and a modified cluster model can be extended to the entire riser which includes an acceleration region, developed flow region and exit region. It can also be applied to a reacting system.;A model based on the Ergun equation is developed to predict the solids flow rate and voidage in the dense phase of the standpipe. The profile of solids flow rate under unsteady state is also presented. Using this method, the dynamic response time at different locations along the standpipe is estimated successfully.;Using the pressure balance analysis, the above models are combined into an integrated CFB model. It can be applied to CFB real-time simulation under transient conditions.
Huang, Yue, "Dynamic model of circulating fluidized bed" (2006). Graduate Theses, Dissertations, and Problem Reports. 2749.