| Energy conservation and environmental protection are the two key factors in energy development and application of China. The energy structure has determined that in a certain long time, the coal-fired power plant will still be the main part in electricity production. The supercritical pressure unit has become dominant in our country. The supercritical parameters have the merits of high efficiency, energy conservation, and environmental protection. Circulating fluidized bed is the new generation clean combustion technology developed at recent 20 years in the world. This technology not only achieves high desulfurizing efficiency, low emissions, and combustion efficiency equal to pulverized coal boiler, but also it has the advantages of fuel flexibility, good load regulation, and ash integrating application. Therefore, CFB technology has spread fast in the world. In order to adjust industry structure, optimize the technology of energy application, and promote energy conservation and environmental protection further, it becomes a new direction and trend of clean coal generating electricity technology for the development of 600MW supercritical CFB boiler. The combination of supercritical technology and CFB can make use of the virtues of the two with low technical risk.A 600MW supercritical CFB boiler is developed and designed in this paper with a single reheat supercritical cycle and moderate mass flux at water wall. The design fuel is Sichuan Baima anthracite. The boiler main steam and reheat steam pressures are 25.4 and 4.45MPa, respectively. The main steam and reheat steam temperatures are 571 and 569℃, respectively. The furnace dimension is 25.736×16.952m, and the height is 58m (from air distributor to boiler roof). The boiler is mainly composed of single furnace,6 insulated high efficiency cyclones,6 loopseals,6 external heat exchangers, rear convective pass,8 rolling ash coolers, and 2 regenerative air preheaters. The pant-leg and double air distributors are used in the furnace, membrane wall is adopted for the evaporation heating surface. The water cooled air distributor and large diameter bell-jar funnel caps are chosen for the boiler. At the top of the boiler,3 cyclones with 9.3m diameter are arranged in each side, respectively. One loopseal and one external heat exchanger are arranged under each cyclone return dip-leg. The way of feeding coal adopts return leg method. There are total 6 high temperature and 6 low temperature feeding coal points. There are total 6 feeding limestone points which are located in high temperature return tubes.The Eulerian-Eulerian two-fluid model is applied to simulate gas-solid two phase flow in the furnace of 600MW supercritical CFB boiler. The three-dimensional mathematical model is established for the simulation of gas-solid two-phase flow in high temperature loop. The control equations are discretized by finite volume methods, the mass and momentum equations are described by Eulerian approach. The characteristics of gas-solid two phase flow in high temperature loop, including the different solids concentrations and velocity vectors in the cyclone inlet, the different solids concentrations in furnace centerline section, the effect of secondary air jets on solids circulating characteristics, solid concentration distribution in return system, and the characteristics of secondary air jets penetration, are obtained through numerical simulation.The heat transfer and flow characteristics of the 600MW supercritical CFB water wall were experimentally investigated in a high temperature and pressure loop. The experimental parameters ranges are:Pressure10～30MPa, mass flux300～1450kg/(m2 s), heat flux60～380kW/m2。The correlations of heat transfer and flow, the boundary of DNB and DRYOUT, and the heat transfer characteristics after DRYOUT have been obtained through the analysis of experimental data. The water wall system can be equivalent to a network consisting of circuits, pressure grids, and connecting pipes according to boiler configuration and heat flux distribution. The mathematical model for predicting the profile of water wall flow rate and temperature is established on account of mass, momentum and energy conservations, and the corresponding program is developed. The program is verified through comparisons between the calculated values and those of power plant. It is showed that there is a good agreement between the present results of flow rate distribution in lower and upper furnace, pressure drop, outlet fluid temperature, metal wall and fin temperature, and those of plant. On the basis of verification, the hydrodynamic characteristics of the 600MW supercritical CFB boiler are obtained. The furnace and water wall screen are partitioned into 110 circuts, and one circuit is partitioned into 29 sections. There is a little change for heat flux in one section.184 nonlinear equations, including 158 momentum equations and 26 mass equations, were solved in the analysis. The characteristics of flow rate distribution and metal temperature at BMCR load, 75%BMCR load, and 30%BMCR load are calculated, and the operation safety are analyzed. In addition, the effect of heat absorption deviation on the hydraulic characteristics is discussed.The computer program for the calculation of superheater (reheater) metal temperature is developed. The program is written by Microsoft Visual Basic 6.0, and module is applied. The computation module is the key, which is connected by input module, water/steam properties calculation module, graphic module, and output module (including Word input document and BMP file output).
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