基于流态重构的循环流化床锅炉节能燃烧技术的应用实践

针对循环流化床锅炉辅机电耗普遍偏高的问题,先后在燃烧劣质无烟煤的135 MW机组和300MW机组循环流化床锅炉上进行了降低床料存量实现流态重构的燃烧试验,分析了基于流态重构的循环流化床锅炉节能燃烧技术对改善锅炉机组性能的影响.运行实践表明:流态重构后,循环流化床锅炉辅机电耗明显下降,在风机具备变频条件下电耗可降低更多;135 MW机组锅炉运行厂用电率从8.2%降低为6.9%,300MW机组锅炉厂用电率约为4.3%,锅炉主要受热面的磨损明显减轻,飞灰可燃物含量降低3%～5%.     

循环流化床锅炉的发展前景与目前存在的问题

十多年来，对流化燃烧方式及系统的研究已成为燃烧研究领域的一个重要课题，各种循环流化床锅炉及以流化燃烧为基础的联合循环技术已逐步走向商业化。近年来，国内对循环流化床锅炉的研究取得了很大成绩。目前，循环流化床锅炉已经开始进入国内的商业市场。但是，在已运行的循环流化床锅炉中暴露出了不少问题，直接影响了这一技术的进一步发展和在商业市场竞争能力。本文阐述了循环流化床锅炉技术上的优势，总结了国内运行中的问题，     

循环流化床锅炉燃烧专家控制系统研究

从循环流化床锅炉(CFBB)的运行特性、系统特点出发，基于一台35t／hCFBB，开发了一套锅炉在线监测与燃烧控制系统。并在对循环流化床锅炉分析的基础上，详细阐述了循环流化床锅炉在线监测与燃烧控制系统的模糊专家控制算法以及系统的实现，并对循环流化床锅炉燃烧专家控制系统的性能进行了简单的对比分折。     

国内煤泥燃烧循环流化床锅炉研究现状

文中重点阐述了国内煤泥循环流化床锅炉的研究进展及现状,并结合煤泥在循环流化床锅炉中的燃烧特性,分析了煤泥的主要给料燃烧方式以及纯烧煤泥的循环流化床锅炉的技术特点,对我国纯烧煤泥的循环流化床锅炉的大型化具有一定的指导意义。     

燃煤锅炉改水煤浆锅炉的探讨

随着环境问题和能源问题日益严重,采用洁净煤技术,既能提高锅炉的热效率,又能减少环境污染.因此,常规循环流化床燃煤锅炉改造为燃水煤浆锅炉成为现在的一个发展方向.但使用循环流化床锅炉燃烧水煤浆会对炉膛的换热、循环物料的使用等产生影响,因此,本文主要根据水煤浆的特性和循环流化床锅炉的特点,对燃烧水煤浆锅炉的换热、物料循环等问题进行探讨.     

二级分离循环床锅炉技术改造

二级分离循环流化床锅炉是我国中科院工程热物理研究所八十年代末期研制开发的第一代循环流化床锅炉，经过十多年的发展，目前循环流化床锅炉的物料循环系统已经发生了根本性的变化，循环流化床锅炉燃烧技术日趋完善和成熟，由原来的二级物料循环燃烧发展为一级物料燃烧(即高温绝热物料分离循环燃烧和高温汽、水冷物料分离循环燃烧两种形式)，此项技术作为循环流化床锅炉的核心部分已经成熟。     

哈锅生产的国产最大“绿色锅炉”投运

日前,由哈尔滨锅炉厂有限责任公司自主研发的国产首台具有自主知识产权33万千瓦循环流化床锅炉在江西分宜发电有限责任公司顺利通过168小时试运行,正式投入商业运行,标志着我国大型循环流化床锅炉的研发成功,对哈锅进一步开发国内外循环流化床锅炉市场具有重要的战略意义。循环流化床锅炉之所以被称为“绿色锅炉”,是因为该锅炉可实现炉内高效廉价脱硫,一般脱硫率在90%以上,同时,炉内燃烧温度较低,氮化物生成明显降低,可有效减少对大气的污染。循环流化床锅炉还具有极强的燃料适应性,许多锅炉不能燃烧的贫煤、煤泥、煤矸石等均能充分燃烧,能变废为宝节约资源。目前,燃煤发电带来的环保问题已经引起了全世界的高度关注,循环流化床锅炉具有的一系列优点,正符合当今社会的环保要求,市场前景十分广阔。哈锅从上世纪九十年代初就开始自主研发循环流化床锅炉技术,在国内率先开发出了具有完全自主知识产权的10万、20万、30万千瓦等级的循环流化床锅炉系列产品,为我国洁净煤发电技术的发展做出了积极贡献。“循环流化床(CFB)锅炉关键技术的自主研发及应用”和“循环流化床锅炉本体和动态仿真关键技术的研究及产业化”双双获得2006年度国家科学技术进步二等奖,再一次证...     

循环流化床锅炉启动优化浅谈

循环流化床锅炉燃烧稳定,对煤种的适应性较好,但是,因其燃烧原理及结构特性,循环流化床锅炉冷态启动燃油量多。某火力发电厂循环流化床锅炉投产初期,冷态启动耗燃油达28t左右,通过对冷态启动优化操作的研究和试验,总结出节约燃油的操作方法,降低了循环流化床锅炉冷态启动燃     

循环流化床锅炉（CFB）燃烧系统及污染物排放计算探讨

循环流化床锅炉（CFB）燃烧中使用脱硫添加剂,锅炉热力计算、燃烧及污染物排放等计算公式的计算系数取值范围尚未统一。章提出广西某电厂420t/h 循环流化床锅炉燃烧系统及污染物排放计算方法,供同行参考和讨论。     

关于循环流化床锅炉热效率计算若干问题的探讨

以炉内直接脱硫的循环流化床锅炉为对象，分析了在循环流化床锅炉热效率计算中，其输入热量、燃烧所需空气量、燃烧生成烟气量及生成灰渣量与常规煤粉炉相比发生的变化。同时，文章也对循环流化床锅炉各项热损失进行了探讨。     

Matching of a DC motor to a photovoltaic generator using a step-upconverter with a current-locked loop

A photovoltaic (PV) generator is a nonlinear device having insolation-dependent volt-ampere characteristics. Because of its relatively high cost, the system designer is interested in optimum matching of the motor and its mechanical load to the PV generator so that maximum power is obtained during the entire operating period. However, since the maximum-power point varies with solar insolation, it is difficult to achieve an optimum matching that is valid for all insolation levels. In this paper it is shown that for maximum power, the generator current must be directly proportional to insolation. This remarkable property is utilized to achieve insolation-independent optimum matching. A shunt DC motor driving a centrifugal water pump is supplied from a PV generator via a step-up converter whose duty ratio is controlled using a current-locked feedback loop     

Natural convection of a non-Newtonian fluid about a horizontal cylinder and a sphere in a porous medium

The problem of natural convection of a non-Newtonian fluid about a horizontal isothermal cylinder and an isothermal sphere in the porous medium is considered. The present study is based on the boundary layer approximation and only suitable for a high Rayleigh number. Similarity solutions are obtained by using the fourth order Runge-Kutta method. The effects of the wall temperature T_W and the new power-law index n on the characteristics of heat transfer are discussed.     

Coupling a two-temperature model and a one-temperature model at a fluid-porous interface

We study a convective heat transfer problem in a fluid-porous domain in the case of the local thermal non-equilibrium assumption (LTNE). The issue of this study is to determine appropriate boundary conditions to model heat transfer, while using models with a different number of equations: a two-temperature model in the homogeneous porous region versus a one-temperature model in the free region. To proceed, a two-step up-scaling approach is used, which has the particularity to provide closed jump relations depending on intrinsic characteristic of the interface. Thus, the use of jump or continuity conditions depend only on the interface location inside the fluid-porous transition region. The pertinence of the approach is illustrated on a 2D convective heat transfer problem considering a solid heat source in the porous medium.     

Studies on a two-staged micro-combustor for a micro-reformer integrated with a micro-evaporator

A new micro-combustor configuration for a micro fuel-cell reformer integrated with a micro-evaporator is studied experimentally and computationally. The micro-combustor as a heat source is designed for a 10–15 W micro-reformer using the steam reforming method. In order to satisfy the primary requirements for designing a micro-combustor integrated with a micro-evaporator, i.e., stable burning in a small confinement and maximum heat transfer through a wall, the present micro-combustor is a simply cylinder, which is easy to fabricate, but is two-staged (expanding downstream) to control ignition and stable burning. The aspect ratio and wall thickness of the micro-combustor substantially affect ignition and thermal characteristics. For optimized design conditions, a pre-mixed micro-flame is easily ignited in the expanded second-stage combustor, moves into the smaller first-stage combustor, and finally is stabilized therein. The measured and predicted temperature distributions across the micro-combustor walls indicate that heat generated in the micro-combustor is well transferred. Thus, the present micro-combustor configuration can be applied to practical micro-reformers integrated with a micro-evaporator for use with fuel cells.     

Using a fin with a parabolic concentrator

The consequences of using a fin collector in focusing solar collectors is examined and is found to have merits.     

Bioconvection in a squeezing flow of a micropolar fluid in a horizontal channel

The bioconvection flow of an incompressible micropolar fluid containing microorganisms between two infinite stretchable parallel plates is considered. A mathematical model, with a fully coupled nonlinear system of equations describing the total mass, momentum, thermal energy, mass diffusion, and microorganisms is presented. The governing equations are reduced to a set of nonlinear ordinary differential equations with the help of suitable transformations. The resulting nonlinear ordinary differential equations are linearized using successive linearization method, and the resulting system of linear equations is solved using the Chebyshev collocation method. The detailed analysis illustrating the influences of various physical parameters, such as the micropolar coupling number, squeezing parameter, the bioconvection Schmidt number, Prandtl numbers, Lewis number, and bioconvection Peclet number on the velocity, microrotation, temperature, concentration and motile microorganism distributions, skin friction coefficient, Nusselt number, Sherwood number, and density number of motile microorganism, is examined. The influence of the squeezing parameter is to increase the dimensionless velocities and temperature and to decrease the local Nusselt number and local Sherwood number. The density number of motile microorganism is decreasing with squeezing parameter, bioconvection Lewis number, bioconvection Peclet number, and bioconvection Schmidt number.     

Comparative analysis of a Sisko nanofluid over a stretching cylinder through a porous medium

The present article examines the Sisko nanofluid flow and heat transfer through a porous medium due to a stretching cylinder using Buongiorno's model for nanofluids. Suitable similarity transformations are used to transform the governing boundary layer equations of fluid flow into nonlinear ordinary differential equations. The finite difference method is used to solve coupled nonlinear differential equations with MATLAB software. The impact of different parameters viz., the Sisko material parameter, porosity parameter, curvature parameter, thermophoresis parameter, and Brownian diffusion parameter on the velocity and temperature distribution are presented graphically. Moreover, the effect of the involved parameters on the heat transfer rate is also studied and presented through table values. It is noticed from the numerical values that the porosity parameter reduces the velocity while enhancing the temperature. The curvature parameter enhances the velocity throughout the fluid regime and reduces the temperature near the surface while enhancing the temperature far away from the surface. The study reveals that the thermophoresis and Brownian diffusion parameters that characterize the nanofluid flow reduce the wall heat transfer rate, while the curvature parameter enhances it. This investigation of wall heating/cooling has essential applications in solar porous water absorber systems, chemical engineering, metallurgy, material processing, and so forth.     

Exploration of heat transfer effect in a magnetohydrodynamics flow of a micropolar fluid between a porous and a nonporous disk

An analysis is carried out for the flow characteristics of a conducting micropolar fluid. The fluid was passed in between two parallel disks of infinite radii. The novelty of the study is to consider one of the disks as porous and the other one as nonporous, and the external magnetic field is applied along the transverse direction of the flow. The flow phenomena for the polar fluid characterized by the magnetic effect in conjunction with the temperature equation reduce to a set of coupled nonlinear ordinary differential equations using the requisite transformations and nondimensionalization. An analytical approach such as the variation parameter method is employed to tackle the system efficiently. To emphasize the effect of various physical parameters contributing to the flow phenomena, that is, non-zero tangential slip, Reynolds number, Prandtl number, magnetic parameter, and material parameter on the flow profiles of axial and radial velocities, the microrotation and temperature profiles are presented graphically. To validate the simulated results, a comparison with established results is made, and it is concluded that both are in good correlation.