【作者】 张彦军；

【导师】 高翔； 骆仲泱； 岑可法；

【作者基本信息】 浙江大学 ， 工程热物理， 2009， 博士

【摘要】 节能和环保是我国能源开发和利用中的两大主题。我国能源结构决定了今后相当长的一段时间内,燃煤发电始终是电力生产中的主要部分。超临界机组已成为我国发电行业主力机组,超临界参数具有高效、节能和环保的优点。循环流化床(CFB)是近二十年来在国际上快速发展起来的新一代高效低污染清洁燃烧技术,不仅能实现的脱硫效率、低排放和与煤粉炉相近的燃烧效率,而且还具有燃料适应性广、负荷调节性能好和灰渣易于综合利用等众多优点,因此在国际上得到迅速的商业推广。为了进一步调整产业结构,优化能源利用技术,促进节能和环保,发展600MW等级的超临界循环流化床锅炉发电技术就成为洁净煤发电技术的一个新的方向和趋势。超临界汽水技术和流化床燃烧技术相结合,能够充分发挥二者的优势,并且技术风险不大。设计开发了具有中质量流速的一次中间再热600MW超临界循环流化床锅炉。设计燃料为四川白马无烟煤,锅炉主蒸汽/再热蒸汽压力为25.4/4.45MPa,主蒸汽/再热蒸汽温度为571/569℃,炉膛尺寸为25.736×16.952米,炉膛高度为58米(布风板至顶棚)。锅炉主要由单炉膛、6个高效绝热旋风分离器、6个回料阀、6个外置式换热器、尾部对流烟道、8台滚筒冷渣器和2个回转式空预器等部分组成。炉膛采用裤衩腿、双布风板结构,炉膛内蒸发受热面采用膜式水冷壁结构。采用水冷布风板,大直径钟罩式风帽。炉膛上部左右两侧各布置有3个内径为9.3米的绝热分离器。每个分离器回料腿下布置一个回料阀和一个外置换热器。采用回料点给煤方案,锅炉共有六个高温和六个低温给煤点。共有6个石灰石给料点,布置在6个高温返料管上。采用Eulerian-Eulerian两流体模型对600MW超临界流化床内的气固两相流动进行数值模拟。建立了高温回路内气固两相流动三维数学模型。控制方程采用有限体积方法离散,质量和动量方程用欧拉方法。通过计算,得到了分离器入口通道中心截面颗粒浓度与速度矢量分布、分离器入口通道中心截面不同粒径颗粒浓度分布、炉膛中心截面不同粒径颗粒浓度分布、二次风对床内颗粒内循环特性的影响规律、炉膛中心沿宽度方向纵截面布风板区域颗粒浓度与速度矢量分布、回料系统内颗粒浓度的分布以及二次风穿透能力等高温循环回路内气固两相流动特性。在高温高压汽水两相试验台上对超临界CFB锅炉水冷壁流动传热特性进行了试验研究。试验参数范围为：压力10-30MPa,质量流速300-1450kg/(m2s),热负荷60-380kW/m2。得到了亚临界、近临界、超临界区宽广参数范围内换热系数及摩擦系数的关联式,以及偏离核态沸腾(DNB)、蒸干(DRYOUT)发生的边界条件及蒸干后传热规律。针对垂直管圈结构和炉内热负荷分布特点,将水冷壁划分为由流量回路、压力节点和连接管组成的流动网络系统。根据质量守恒、动量守恒和能量守恒方程,建立了超临界锅炉水冷壁流量和壁温计算的数学模型,并开发了计算程序。以A电厂1000MW超超临界锅炉为校核对象,全面比较了不同负荷下的上炉膛与下炉膛各回路流量分配、压降、出口汽温、壁温与鳍端温度等参数,结果表明计算值与电厂提供值符合的非常一致,程序是正确可靠的。在此基础上,对所开发的600MW超临界CFB锅炉水动力特性进行了计算分析。根据水冷壁和中隔墙在炉膛内的受热情况,炉膛及中隔墙共划分为110个回路,每一回路划分为29个计算管段,管段划分原则是确保同一管段长度内管子热负荷沿高度方向变化较小。计算中共求解184个非线性方程,其中动量守恒方程158个,流量守恒方程26个。对BMCR、75%BMCR、30%BMVR负荷下的流量分配特性和壁温分布特性进行了计算,并对水冷壁运行安全特性进行了分析。另外,还对吸热偏差对水动力特性的影响进行了分析。开发了CFB锅炉屏式过(再)热器计算程序。程序由Microsoft Visual Basic6.0中文版开发完成,采用模块化方式。计算模块是程序的核心模块,与此模块相连接的还有用户参数输入模块、水蒸气热力性质数据库模块、画图模块和结果输出模块(包括WORD文档输出和BMP格式文件输出模块)。更多还原

【Abstract】 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).更多还原