Simulation study to control solids flow rate in a pilot scale cold flow circulating fluidized bed

Controller scaling that is used to frequency-scale an existing PID controller for a large class of plants, eliminates the repetitive controller tuning process for plants that differ mainly in gain and bandwidth. Controller parameterization makes the controller parameters a function of a single variable, the loop-gain bandwidth, and greatly simplifies the tuning process. The controller is scaled according to the gain and frequency scales of the given plant transfer function and the bandwidth parameter whose initial value is set based on the bandwidth requirement from the transient response. This single parameter is required to be gradually adjusted according to a controller performance. However, if the explicit transfer function of a given system is not known, the gain and frequency scales can be determined from an empirical model transfer function obtained from the System Identification procedure. In this paper, we propose a new technique based on the theory of Recursive Least Squares Estimation that allows determining the bandwidth parameter as well as the closed loop model parameters online. As the technique is recursive by nature, it further avoids the adjustment of a bandwidth parameter in accordance with the controller performance.. In a simulation study of controlling solids circulation rate, the technique is applied to time series data obtained from a pilot scale cold flow circulating fluidized bed (CFCFB) present at National Energy Technology Laboratory, Morgantown, WV. If the measurement of solids flow rate were possible as in the present cold flow model, the proposed method could be tested in an industrial scale system such as a fluidized catalytic cracking (FCC) reactor.