Dynamic Real-time Simulating Modeling Of Circulating Fluidized Bed Boiler

The circulating fluidized bed boiler (CFB) combustors has been widely used because of wide applicability for fuel, high combustion efficiency, low discharge amount of nitric oxide and high sulfur capture efficiency. The understanding of working process mechanisms in CFB is far from satisfied because of its complex process, which is one of the most important problems for its design and operation. It has been proved that the computer simulation is a convenience and fast way to analyze the dynamic characteristics of the large CFB. It is valuable to build a real-time model to analyze the overall performances of CFB boiler and solve the problems existing in its operation process.In this paper, the dynamic mathematical model has been developed based on the principle and experience equations. Solid particles balance, gas species balance, total energy balance and carbon balance are considered to construct the integrated equations for the combustion model. In this model gas-solid fluidization, char combustion, sulfur dioxide absorption and heat transfer are considered. Some reasonable simplifications to the solid particle diameter distribution and furnace parameter distribution for heat transfer coefficient calculation are adopted to meet the requirement of real-time calculation. In addition, several dynamic mathematical models of interrelated equipment have been developed, such as separator, heater, evaporator, high pressure cylinder and desuperheater.All the sub models are built based on the modular method, and the overall simulation model which is composed of these sub models is completed with Visual Fortran programming language. In order to satisfy the request of the real-time simulation, the variable step Euler method is chosen. At the same time, algorithm is separated from the model, so the model can be expanded, reused and modified easily.In order to validate the models, the static characteristics analyses and several simulation experiments have been completed. The simulation results show that the model can exactly reflect the practical working process, and the runtime is short enough to be used in real-time simulation work. Although the model is related to a particular CFB boiler, the model has can be readily adapted to other CFB boiler systems too.