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.

I MWth Test Facilities for Circulating Fluidized Bed Combustion

This paper presents the technical parameters and features of 1 MWth test facilities for circulating fluidized bed combustion (CFBC) at Thermal Power Research Institute (TPRI) of State Power Corporation (SP), introduces the test items that can be proceeded and trial combustion projects completed. The development status of CFBC technologies abroad and the level of China in this field are also introduced in the paper.

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.

烟气再循环对350 MW CFB锅炉深调运行特性影响

为解决超临界CFB锅炉超低负荷时流化安全性及NO_(x)超低排放,引入烟气再循环技术,以某电厂超临界350 MW CFB锅炉为研究对象,搭建了循环半干法脱硫后烟气的再循环辅助调峰系统,基于运行实测数据,研究该锅炉在30%~60%负荷率下烟气再循环对平均床温、分离器入口温度、排烟温度、炉膛出口烟气NO_(x)、CO质量浓度、飞灰及底渣可燃物含量、汽水参数等运行参数的影响,试验结果表明:烟气再循环协同下,30%~60%负荷SNCR脱硝后NO_(x)最终排放小于50 mg/m^(3),30%负荷实现锅炉原始NO_(x)超低排放;床温降低15~22℃,炉膛出口烟温提高10~13℃,主再热汽温在558℃以上;随锅炉负荷降低,飞灰及底渣含碳量升高,CO质量浓度未见大幅增加;40%负荷炉膛二次风SNCR脱硝NO_(x)降幅约15 mg/m^(3);负荷上升/下降变化最小速率1.23%Pe;30%负荷及以上保持干态运行,水冷壁壁温最大偏差55℃,屏过及屏再最大壁温差分别55、47℃,均未出现壁温超温。

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.

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 based 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.

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。

600 MW CFB锅炉汽冷式旋风分离器受热面管失效分析及优化措施

基于超临界循环流化床(CFB)锅炉汽冷式旋风分离器受热面管发生的1次失效,为防止类似失效的再次发生,对失效进行试验分析。超低排放选择性非催化还原(SNCR)脱硝系统对耐火材料和受热面管有腐蚀,在高温下分解的产物与受热面管金属发生反应,引起受热面的有效壁厚减薄,最终受热面管因无法承受内部介质的压力而发生失效。结合运行状况及失效原因分析,对耐火材料进行固定方式优化和材料优化,以及提高防磨防爆检查力度、优化雾化空气压力等优化措施,有效提升了运行的可靠性,在汽冷式旋风分离器检修管理方面有推广意义。

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。

Combustion characteristics of low-quality lignite for different bed material sphericities in a circulating fluidized bed boiler:A numerical study

This study delves into the combustion behavior of various lignite types within a circulating fluidized bed boiler(CFBB),with a primary focus on the impact of different bed material sphericity ratios(0.5,0.7,and 0.9).Utilizing bed material with a sphericity ratio of 0.9 sourced from theÇan power plant and verified through experimentation,the research reveals several key findings.Notably,furnace temperatures tended to rise with higher sphericity ratios,albeit with variations between lignite types,particularly highlighting the complexity of this relationship in the case of GLI-Tunçbilek lignite.Pressure levels in the combustion chamber remained consistent across different sphericity ratios,indicating minimal influence on pressure dynamics.Improved combustion efficiency,especially at the bottom of the boiler,was observed at lower sphericity levels(0.5 and 0.7)forÇan lignite,as reflected in CO_(2) mole fractions.While NO_(x) emissions generally decreased with lower sphericity,the sensitivity to sphericity varied by lignite type,with Ilgın lignite showcasing low NO_(x) but high SO_(2) emissions,underscoring the intricate interplay between lignite properties,sphericity,and emissions.Overall,this study advances our understanding of CFBB combustion dynamics,offering insights valuable for optimizing performance and emissions control,particularly in lignite-based power.

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。

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。

基于在线监测数据的石化企业CFB锅炉大气污染物排放综合评价

为评估CFB锅炉现有工艺的清洁生产水平及大气污染治理效果,收集了2021年1112家典型石化企业循环流化床(CFB)锅炉的3种常规大气污染物(SO_(2)、NO_(x)以及颗粒物)质量浓度和废气流量的连续小时级在线监测数据,并对污染物排放质量浓度的月均值进行了统计分析。3种污染物排放质量浓度均值分别为22.83 mg/m^(3)、5.68 mg/m^(3)和3.02 mg/m^(3),大气污染达标排放率已经达到100%。单因素方差分析表明CFB锅炉间的污染物排放质量浓度存在显著性差异。基于系统聚类分析可将12台CFB锅炉分为两类:一类污染物排放质量浓度较高,而废气流量较低,占比74.54%;另一类污染物排放质量浓度较低,而废气流量较高,占比25.46%。通过CRITIC客观赋权法构建废气排放综合指数以比较各CFB锅炉的污染排放状况,发现处于超低污染水平的CFB锅炉有2个;处于低污染排放的最多,共有7个;处于中等强度排放的有3个。废气流量对综合指数贡献大,今后在线监测达标排放仍应将污染物总量控制作为重点工作,建议结合企业废气排放口污染物排放总量数据提出企业总量管理目标。