Effects of particle type on the particle fluidization and distribution in a liquid–solid circulating fluidized bed boiler

A liquid-solid circulating fluidized bed boiler is designed and built for visualization research by applying the fluidized bed heat transfer and fouling prevention technology to the water side of the boiler. Four types of engineering plastic particles with different physical properties are selected as the solid working media. The effect of particle types on the fluidization and distribution of particles in the boiler is investigated under different feedwater flow rates and amount of added particles by using the charge couple device image measurement and acquisition system. The results show that all kinds of particles can't be normally fluidized and accumulate in the drum at low amount of added particles and feedwater flow rate. The particles with great density and low sphericity are more likely to accumulate. The average solid holdup in the riser tubes increases with the increase in feedwater flow rate and the amount of added particles. The non-uniform degree of particle distribution in the riser tubes generally decreases with the increase in feedwater flow rate and the amount of added particles. The particles with small density and settling velocity have high average solid holdup in the riser tubes under close sphericity. In generally,the smaller the density and settling velocity, the more uniform the particle distribution in the riser tubes.Three-dimensional diagrams of the non-uniform degree of particle distribution in the riser tubes of the boiler are established.

Compatibility of Fly Ash and Slag from Circulating Fluidized Bed Boiler for Concrete Beam

The applications of fly ash and slag from circulating fluidized bed boiler were studied as mineral admixture and aggregate for steel reinforced concrete beam.The results show that the concrete beam with fly ash and slag from circulating fluidized bed boilers has a similar ultimate cracking load coefficient as the ordinary cement concrete and a higher bending moment limit.Under the same load,it has a smaller deformation than the ordinary concrete.

Model prediction of the operating behavior of a circulating fluidized bed boiler

An improved mathematical model for a circulating fluidized bed (CFB) boiler baaed on the model developed earlier by the authors was applied to simulate the operation of a 12 MW CFB boiler.The influences of the excess air ratio, primary air ratio, coal particle size distribution, coal properties (ash content and volatile content) and Ca/S ratio on the boiler operation were analyzed. The results showed that the model simulation may be applied to the optimum design and economic operation of the CFB boiler.

Hardening Properties of Foamed Concrete with Circulating Fluidized Bed Boiler Ash, Blast Furnace Slag, and Desulfurization Gypsum as the Binder

Recently, a large amount of circulating fluidized bed boiler ash (CFBA) and desulfurization gypsum (DSG) has been produced, and it is essential to develop technology to utilize them. These materials have CaO and SO3, which are considered to be a stimulant for blast furnace slag (BFS). This study presents an experimental investigation of the compressive strength and heavy metal ions immobilization properties of cement-free materials comprising CFBA, BFS, and DSG. The feasibility of manufacturing foamed concrete using these materials was examined, and field test of foamed concrete was conducted. Experimentally, the flow, compressive strength, and heavy metal ions concentration were evaluated via inductively coupled plasma atomic emission spectroscopy (ICP-AES) of the paste and foamed concrete. The experimental investigation revealed the self-healing hardening ability of fluidized bed boiler ash. In addition, the compressive strength was increased with the increasing replacement rates of BFS and DSG in the CFBA paste, and the compressive strength of 14.6 - 17.2 MPa was recorded over 28 days of curing. From the result obtained, the feasibility of manufacturing foamed concrete with a foam volume of 120 L, incorporating the aforementioned materials, is confirmed. It was also found that after 28 days of age, a 7.9-MPa compressive strength of the foamed concrete was attained, and heavy metal ions elution in this foamed concrete was also significantly reduced. Therefore, CFBA, BFS, and DSG could be used as a binder for the foamed concrete.

基于TF-NGO算法的CFB锅炉床温系统建模研究

床温是循环流化床(CFB)锅炉重要的运行参数之一。针对床温耦合性强、干扰因素多、控制复杂的问题,亟需建立床温的数学模型,以实现床温控制,从而保证CFB锅炉安全、平稳地运行。为此,首先引入了混沌映射、切线飞行(TF)和柯西变异策略改进北方苍鹰优化(NGO)算法,并用实际工况的系统模型测试TF-NGO算法。测试结果表明,TF-NGO算法拥有更快的收敛速度和更高的寻优精度。其次,采集并预处理山西某电厂350 MW超临界CFB锅炉的现场运行数据。最后,采用TF-NGO算法对所建模型的参数进行辨识,并用实际工况数据进行模型验证。辨识和验证结果表明,由TF-NGO算法辨识的床温模型与实际输出拟合度高,能有效反映床温的动态特性,证明所建模型的有效性。该研究为后续对350 MW超临界CFB锅炉床温的优化控制研究奠定了基础。

Emissions of SO_2, NO and N_2O in a circulating fluidized bed combustor during co-firing coal and biomass

This paper presents the experimental investigations of the emissions of SO2, NO and N20 in a bench scale circulating fluidized bed combustor for coal combustion and co-firing coal and biomass. The thermal capacity of the combustor is 30 kW. The setup is electrically heated during startup. The infuence of the excess air, the degree of the air staging, the biomass share and the feeding position of the fuels on the emissions of SO2, NO and N2O were studied. The results showed that an increase in the biomass shares resulted in an increase of the CO concentration in the flue gas, probably due to the high volatile content of the biomass. In co-firing, the emission of SO2 increased with increasing biomass share slightly, however, non-linear increase relationship between SO2 emission and fuel sulfur content was observed. Air staging significantly decreased the NO emission without raising the SO2 level. Although the change of the fuel feeding position from riser to downer resulted in a decrease in the NO emission level, no obvious change was observed for the SO2 level. Taking the coal feeding position R as a reference, the relative NO emission could significantly decrease during co-firing coal and biomass when feeding fuel at position D and keeping the first stage stoichiometry greater than 0.95. The possible mechanisms of the sulfur and nitrogen chemistry at these conditions were discussed and the ways of simultaneous reduction of SO2, NO and N2O were proposed.

Hydrothermal synthesis of zeolitic material from circulating fluidized bed combustion fly ash for the highly efficient removal of lead from aqueous solution

The utilization of coal fly ash derived from circulating fluidized bed combustion(CFBFA)still faces great challenges because of its unique characteristics.In this study,a zeolitic material with Na-P1 zeolite as the main phase was successfully synthesized via a hydrothermal method by using CFBFA as the raw material.The effects of hydrothermal temperature,time,and added CTAB amount on the characterizations of synthesized materials were investigated by XRD,SEM,and XPS.The properties of the optimal zeolitic material and its adsorption performance for Pb^(2+)in aqueous solution were evaluated.The influences of pH,initial concentration,dosage,and temperature on Pb^(2+)adsorption were also examined.Results revealed the following optimal parameters for the synthesis of zeolitic material:NaOH concentration of 2 mol·L^(-1),solid-to-liquid ratio of 1:10 g·ml^(-1),hydrothermal temperature of 110℃,hydrothermal time of 9 h,and CTAB amount of 1 g(per 100 ml solution).The adsorption capacities of the zeolitic material reached 329.67,424.69,and 542.22 mg·g^(-1) when the pH values of aqueous solution were 5,6,and 7,respectively.The Pb^(2+)removal efficiency can reach more than 99%in aqueous solution with the initial concentrations of 100-300 mg·L^(-1) under pH 6 and suitable adsorbent dosage.The adsorption and kinetics of Pb^(2+)on the zeolitic material can be described by Langmuir isotherm and pseudo-second-order kinetic models,respectively.The ion exchange between Pb^(2+)and Na^(+)and chemisorption are the main adsorption mechanism.All these findings imply that the synthesis of low-cost adsorbent for Pb^(2+)removal from weak acid and neutral aqueous solution provides a highly effective method to utilize CFBFA.

循环流化床锅炉(CFB)系统流程模拟

以某石化项目450 t/h超高压循环流化床锅炉系统为对象,采用Thermoflex软件建模并对其进行变工况分析,通过与锅炉厂提供的实际数据进行对比,验证了该流程模拟的准确性。利用该模型进行了不同煤种工况对系统的影响因素分析,研究结果可为该锅炉系统设计和设备选型提供理论依据,对该项目动力站实际生产运行提供指导。

探讨CFB锅炉结焦事故原因和应对措施

循环流化床锅炉在实际生产中,因锅炉煤炭燃烧、物料流化不良、风帽大面积损坏、操作控制不当等各种原因,导致锅炉出现结焦,严重影响设备安稳运行。通过对锅炉结焦原因和案例分析,进行技术改造和参数优化,加强日常管理,避免了锅炉结焦事故,确保了装置长周期运行。

基于ISO-PSO的350 MW超临界CFB锅炉主汽温建模研究

针对火电厂目前主蒸汽温度数学模型不准确、不能有效地反应实际生产过程、辨识结果偏差较大等问题,使用学习因子动态调整及随机惯性权重策略改进的二阶振荡粒子群优化(ISO-PSO)算法进行建模。首先,采用学习因子动态调整、随机惯性权重策略对二阶振荡粒子群算法进行改善。测试结果表明,改进算法拥有更好的收敛速度及寻优精度。其次,处理山西某电厂350 MW超临界循环流化床(CFB)锅炉在300 MW工况下采集到的主蒸汽温度数据。最后,对比ISO-PSO算法和粒子群优化(PSO)算法。辨识结果及验证结果表明,ISO-PSO算法辨识的主蒸汽温度模型与实际输出的拟合度更高,能够更加准确、快速地反映主蒸汽温度的变化。所建立的主蒸汽温度模型可以及时跟踪实际曲线。该研究为后续350 MW超临界CFB锅炉主蒸汽温度优化控制研究奠定了良好的基础。

基于改进差分进化算法的CFB锅炉主蒸汽压力建模

建立准确的主蒸汽压力数学模型对提升循环流化床(CFB)锅炉主蒸汽压力控制系统性能有着实际意义。受现场条件制约,近年来基于数据驱动的闭环建模已趋于实用化。针对模型参数辨识过程寻优速度和精度指标,提出一种引入两个权重系数的改进差分进化(IDE)算法。与传统差分进化算法相比,改进后的算法在模型参数辨识过程中的寻优速度和精度均有提升,辨识所得模型更加准确。该结果证明了改进后算法的稳定性。通过采集山西某电厂350 MW超临界CFB锅炉现场的实际运行数据并进行预处理,将燃料量和汽机阀门开度同时作为输入、主蒸汽压力作为输出,并利用IDE算法寻优得到主蒸汽压力的最佳模型参数。对比结果表明,模型有着更高的拟合度。该研究对350 MW超临界CFB锅炉主蒸汽压力优化控制有一定的指导意义。

CFB中基于赤泥催化的N_(2)O/NO_(x)/SO_(2)协同降低技术路线

随着污染物排放标准越发严格,为进一步发挥循环流化床污染物控制成本低的优势,需要明晰各个运行参数和因素对N_(2)O/NO_(x)/SO_(2)排放的影响规律,挖掘N_(2)O/NO_(x)/SO_(2)协同超低排放的可能性。基于“十四五”规划的要求和N_(2)O/NO_(x)/SO_(2)的研究现状,初步形成了一条或实现N_(2)O/NO_(x)/SO_(2)协同降低的技术路线:在保证燃烧效率的前提下,选择合适的床料(如赤泥)在炉内通过催化或反应脱除N_(2)O,通过平衡赤泥中的铝铁比例,实现N_(2)O和NO_(x)的双低排放,同时由于赤泥良好的吸附能力和较强的碱性,可进一步实现SO_(2)的脱除。如必要,通过流态重构或超细石灰石等将剩余的NO_(x)和SO_(2)降至合理水平,或通过SNCR和脱硫塔分别处理剩余的NO_(x)和SO_(2),使其达到排放标准,从而实现N_(2)O/NO_(x)/SO_(2)的协同超低排放。

深度调峰运行下某CFBB水冷壁管热应力分析

随着大量新能源发电的并网,火电机组循环流化床锅炉(circulating fluidized bed boiler, CFBB)参与电网调峰时,机组的负荷在不断变化,机组的安全性受到了挑战,研究调峰时锅炉受热面管的温度与应力是必要的。通过数值模拟的方法对深度调峰运行下的二维膜式水冷壁管的温度、变形量和热应力进行分析。研究结果表明:CFBB深度调峰时热负荷由锅炉最大连续蒸发量(boiler maximum continuous rating, BMCR)至20%BMCR,膜式水冷壁管的温度、变形量和热应力都在逐渐减小;BMCR工况时,水冷壁管的温度、变形量和热应力最大分别为431.53℃、0.263 mm、131 MPa,均在水冷壁管材允许的范围内。热负荷由BMCR到20%BMCR和由20%BMCR到BMCR不断的调峰过程中,CFBB膜式水冷壁管的温度、变形量和热应力在不断交替变化,水冷壁管在交变的温度、变形量和热应力作用下疲劳损伤不断累积,最终因疲劳而失效。

240t/h CFB锅炉布袋除尘器升级改造

文中针对某发电公司2×240t/h循环流化床锅炉布袋除尘器的升级改造方案进行阐述,除尘器升级改造后,粉尘排放浓度从30mg/Nm^(3)降至10mg/Nm^(3)以内,满足了《陕西省锅炉大气污染物排放标准》的新标准,各项技术指标均达到了设计要求,并取得了良好的经济效益和社会效益。

660 MW超超临界CFB锅炉失电壁温计算及运行措施

超超临界循环流化床锅炉发生失电时,保证锅炉受热面安全至关重要。对超超临界循环流化床锅炉在失电事故后影响受热面安全性的因素进行分析,根据质量、动量、能量守恒以及金属管壁蓄热方程组成的锅炉汽水系统非稳态流动传热计算模型,开发出锅炉汽水系统动态特性计算软件,用于计算锅炉失电工况受热面工质温度及金属壁温随时间的变化规律。通过计算得到了锅炉发生失电事故后保证受热面安全措施为高压旁路阀以40%BMCR的流量进行排汽,且最短排汽临界时间为110 s,同时省煤器进口需以140 t/h的流量补水。可知该工况下水冷壁、低温过热器、中温过热器、高温过热器工质温度及管壁温度随时间先上升再下降,管壁温度最高值均低于受热面选材的允许使用温度。该措施可保证超超临界CFB锅炉在失电事故下各受热面的安全,解决了CFB锅炉发生失电事故后受热面超温问题,为电厂运行提供指导。

CFBB燃烧系统耦合分析与DMC控制器设计

循环流化床锅炉(CFBB)燃烧系统耦合关系复杂且难以控制,该文将CFBB燃烧过程简化为一个二入二出对象,并针对其中最难控制工况下的标称参数模型进行控制。采用逆奈氏阵列法(INA方法)对CFBB系统的耦合性进行分析,得出利用单位矩阵静态解耦法对系统进行初步解耦的结论。考虑最小化CFBB系统的ITSE指标,提出一种基于遗传算法的CFBB系统DMC控制器参数寻优方法。仿真表明,提出的DMC参数寻优方法能快速响应主汽压和床层温度的变化,具有不错的鲁棒性和跟踪性能。

火电厂CFB锅炉的燃烧技术优化对策

火电厂CFB锅炉是近些年被快速推广应用的全新燃烧技术之一,能够实现多次的低温燃烧,同时可以循环应用脱硫剂实施脱硫,从而大大提升脱硫效率(可以达到90%),整体燃烧效率与传统煤粉炉大体相当。近些年我国对绿色环保日益重视,针对氮氧化物的排放制定了更高的标准。虽然CFB锅炉可以一定程度上实现低氮燃烧,但是为了有效满足当今超低污染物排放的要求,需要对其进一步进行技术改造优化。以某发电厂2×300 MW的CFB锅炉为例,阐述其技术优化的内容,同时比对分析锅炉的燃烧效率,结果表明,技术优化后,锅炉的燃烧效率明显提升,同时大大了降低氮氧化物的排放量,对于进一步推动火电厂实现绿色环保发展具有参考意义。

解开CFB锅炉惯性产生之谜:一种全回路动态模型方法

“双碳”目标背景下,循环流化床机组亟需加快变负荷速率,而目前尚缺乏对变负荷过程中惯性生成机理的准确阐释。基于质量平衡、能量平衡、化学反应平衡,并考虑气固流动特性的差异,构建了炉侧全回路动态模型,以描述变负荷过程中流动、传热、燃烧的物理机制。模型应用于一台135 MW循环流化床锅炉机组进行验证,结果表明该模型能较为准确地预测稳态、变负荷工况的运行参数,相对误差不超过3%。探讨了锅炉的固有动态响应特性,揭示了变负荷过程中三大惯性的耦合机制,确立了流动惯性的主导地位,为提出加快变负荷速率的策略奠定基础。

660 MW超临界CFB锅炉受热面常见问题分析

本文针对660 MW超临界循环流化床(CFB)锅炉投运2年以来水冷壁和外置床发生的设计问题及运行过程中易出现的故障进行了全面原因分析,并提出了主要解决措施。通过对受热面出现的一系列问题原因进行分析,为后续更大容量循环流化床机组的设计提供借鉴,通过采取针对性措施,大大提高了锅炉运行的稳定性和可靠性。