Investigation of the start-up procedure of a circulating fluidized bed test unit using a commercial steady state simulation tool

Abstract The present work describes a pseudo-dynamic approach to describe transient changes in operating conditions. A steady state solver is repeatedly called and the new calculation is based on results of the preceding step. This allows the introduction of a time variable and numerical description of transient changes. Results are presented for varied scenarios and an optimized start up procedure is proposed. It is concluded that the relatively simple approach implemented as an add-on to existing commercial tools can enlarge the focus of steady state simulation tools to basic dynamic problems such as plant start up or changes between operating cases. Introduction Reasonable prediction of plant behaviour during plant start up is crucially important for design of start-up supporting components and during commissioning of full size installations. Plant designers commonly use only steady state calculation at defined operating cases. Such process models allow description on a reasonably detailed level, but they usually do not allow calculation of transient states between operating cases. Sound dynamic tools used for control system optimization, on the other hand, usually do not allow inclusion of the whole system because of over-boarding complexity. This work is describing a new method, which can be easily implemented to existing commercial tools and allows a sound estimate of the facilities temperature during heating-up procedure or other dynamic problems. Compared to other proposed dynamic models [Galgano et al., 2005; Chen et al., 2006; Hadavand et al., 2008; Yang et al., 2008], the main advantage of this method is the possibility of considering the whole process instead of calculating only single process units. A similar approach based on a process simulation tool has been presented for dynamics of a diesel engine by Chrenko et al. [2009]. This advantage is crucially important in order to get an overall picture during transient changes between operating cases.