Dynamic Simulating Modeling Of 600MW Supercritical Circulating Fludized Bed Boiler

The circulating fluidized bed combustion(CFBC) technology is widely used now for it’s broad fuel adaptability, high combustion efficiency, low pollutant emission and many other advantages. At the same time because the working principle of circulating fluidized bed(CFB) is very complex, especially the working mechanism of internal flow and combustion is not fully understood, it brings to the design and running of the CFB boiler a great challenge. Therefore, based on the existing research on mechanism of CFB, analyzing the dynamic characteristics of large CFB boiler through the simulation modeling method has important practical significance.The research object is DG1900/25.4-II9 pattern CFB boiler in this paper,which is manufactured by Dongfang Boiler Group Co., Ltd..Based on former researches,a complete mathematical model of 600 MW supercritical CFB boiler has been developed. Main processes in CFB boiler such as hydrodynamics, char combustion, devolatilization of coal, formation of harmful substances and so on are considered in detail. Influence on combustor’s combustion and heat transfer is also considered when high temperature cyclone seperator, loop seal and external heat exchanger are joined. A modeling method for CFB boiler is presented which uses cell approach to simulate the axial distributions of solid and gas phases in the bed, meanwhile uses ‘core-annular’ construction to describe the radial distributions of solid particles and particle clusters. Ultimately, a quasi-two dimensional dynamic and static mathematical model is established which takes into account the influence of wide size distribution of feeding coal,limestone and bed inventory on hydrodynamics,chemical reactions and heat transfer.To build a feed-water and steam system model, a external heat exchanger(EHE) general module is developed using advanced continuous simulation language(ACSL). The dynamic mathematical model of feed-water and steam system of CFB boiler is then built using MMS(Modular Modeling System) simulation platform. Simulation of complete model is realized through the coupling of combustion system model and steam-water system model.In this paper, the dynamic simulating results of the complete model indicate that the model can correctly reflect the running characteristics of CFB boiler. Conclusions obtained can provide theoretical basis for the design, operation and enlargement of CFB boiler.