25t/h循环双流化床锅炉运行分析

从技术特点、试生产后的情况、效益等方面对25t/h循环双流化床锅炉进行分析,在合成氨厂可以推广应用。     

双流化床反应器间气体泄漏规律的数值模拟

建立了描述双流化床化学链燃烧反应器内气固两相流动的数学模型,采用计算流体动力学方法,模拟考察了提升管和鼓泡床相耦合的双流化床内不同单元之间气体泄漏产生原因和影响因素。化学链燃烧系统压力平衡的分析结果表明,反应器间的气体泄漏主要发生在溢流装置和鼓泡床之间;增大溢流装置表观气速,气体泄漏增大,而增大提升管或鼓泡床表观气速时,气体泄漏会随之减小;化学链燃烧系统内颗粒总藏量增加时,气体泄漏会减小;颗粒粒径减小后反应器之间气体泄漏降低。其研究结果对其他循环流化床反应器的设计与工程放大也有一定的借鉴作用。     

小议锅炉燃烧控制

从四个方面入手研究锅炉燃烧控制问题,解决燃煤锅炉的控制难、提高燃烧效率及减少燃烧效率问题。     

双流化床生物质气化动力学建模与分析

为进一步研究双流化床生物质气化器中合成气含量分布,将气化器鼓泡床层分为气泡相和乳化相,依据动力学反应分别进行各相质量和热量衡算,计算结果与实验值吻合较好. 随气化温度升高,CO含量增加,而H2和CO2含量降低;蒸汽与生物质质量比(S/B)增加促进水蒸汽变换和重整反应,消耗CO和CH4,生成H2和CO2,当S/B从0变化到1.2时,CO/H2变化44%,说明S/B增加主要促进了水蒸汽变换反应. 气化温度870℃及S/B=0.75条件下,当气化器高度为0~0.5 m时,H2O含量急剧下降,H2含量急剧上升,CO与CO2含量逐渐上升,当该高度大于0.5 m后,气化反应基本完成.     

煤燃烧解耦双流化床气化反应基础研究

为确定燃烧解耦双流化床气化的气化反应条件和气化反应器的设计,在直径60 mm和高700 mm的小型流化床反应器中,采用粒径8 mm以下的锅炉烟煤以间歇气化方式在1 133 K的条件下,研究了进料方式、气化剂中水蒸汽和O2含量、以及煤料粒径等因素对煤气化生成燃气反应过程的影响,重点考察了各因素对煤转化速率的作用规律.综合各因素对C转化为燃气的速度、最大C转化率及生成气热值的影响趋势,确定了适宜的煤气化操作条件为;从流化颗粒表面附近加料,气化剂中O2体积分率5%、水蒸汽体积分率35%,煤粒径小于5 mm.在该条件下,实现60%的C转化为燃气所需要的停留时间大致为600s.     

锅炉催化燃烧节能减排双见效

由北京金源化学集团有限公司开发的燃煤催化燃烧技术，近日在淮化集团有限公司与合肥红四方化工公司成功试用。鉴于该成果对于促进煤炭资源综合利用、降低燃煤过程污染物排放、提高生产安全性等方面具有突出效果，安徽省决定将其作为首批节能技术和产品在全省推广。     

循环流化床锅炉SO_2超低排放技术研究

针对循环流化床锅炉污染物生成量较低的特点,分析了锅炉SO_2生成量的影响因素,不同脱硫工艺的优缺点,结合试验研究结果和工程应用实例提出了循环流化床锅炉实现SO_2超低排放的技术。结果表明:循环流化床锅炉SO_2生成量取决于煤的硫分中可燃硫所占比例、煤灰中CaO等碱金属氧化物含量和锅炉运行参数,运行参数中床温影响最大;通过优化锅炉运行参数降低SO_2生成量,炉内干法高效脱硫和烟气脱硫相结合的深度脱硫技术可以实现SO_2超低排放的目标,并具有更高的调节灵活性和运行可靠性;烟气脱硫工艺的选取上,CFB-FGD半干法脱硫工艺相对于石灰石-石膏湿法脱硫工艺更具有经济优势。     

黄磷尾气在循环流化床锅炉中的掺烧使用

国内大部分中小型黄磷企业受制于矿、电因素无法连续稳定生产,给黄磷尾气的净化和规模化综合利用造成很大困难。为适应这一工况,提高黄磷尾气的利用率,分析黄磷尾气对热工设备的腐蚀机制,在降低投资和净化成本的基础上,探索出在循环流化床锅炉中掺烧黄磷尾气的方法,并辅以脱硫固磷、超音速喷涂等防腐蚀措施,并对防腐机理进行分析。锅炉近十年运行安全平稳,达到了节能减排的目的。     

超临界循环流化床锅炉低负荷掺烧试验研究

为掌握世界首台600 MW超临界循环流化床锅炉低负荷工况下燃料变化对锅炉燃烧稳定性和设备运行可靠性的影响,进行了不同比例设计煤与神华煤的实炉掺烧试验,对比研究了4个试验工况下燃烧系统、汽水系统、烟风系统和主要污染物排放参数的特性,试验结果表明:超临界循环流化床锅炉在60%额定负荷工况下掺烧50%神华煤时,锅炉仍能够保持稳定可靠运行,锅炉热效率平均达到90%以上,过热蒸汽和再热蒸汽参数满足设计要求,SO_2和NO_x排放值均低于200 mg/m~3,满足四川地区现阶段排放限值要求。     

循环流化床锅炉炉内脱硫技术的应用

介绍了炉内脱硫技术在循环流化床锅炉上的应用及优化改造情况,通过可行性分析、试验,采用合理的整体方案工艺及流程设计,实现了SO2达标排放。     

Mixing and combustion in a shallow coal-limestone fluidized bed combustor

A model based on the Monte Carlo approach was developed to simulate the mixing and combustion behavior of a shallow coal-limestone fluidized bed combustor. The model involved the coupling of two sub-models: a combustion sub-model based on the two-phase concept of fluidization and a mixing sub-model based on our previously developed dynamic mixing model. The combustion sub-model considered both the volatile and char combustion. It assumed that the combustor consisted of three distinct phases, i.e., jet, bubble and emulsion, with combustion occurring only in the emulsion phase. The mixing sub-model considered the upward or downward movement of a coal particle in the bed as being governed by certain probability laws; these laws were, in turn, affected by the bubbling hydrodynamics. In all, the combustor simulation model took into consideration the effects of coal feed rate, coal size distribution, limestone size, air flow rate and combustor temperature on the combustor behavior. The simulation results included the dynamic response of coal concentration profile, coal size distribution, coal particle elutriation rate as well as the mixing status between the coal and limestone particles.     

循环流化床锅炉和煤粉锅炉的优劣对比

从结构、运行情况、对燃料的适应性及环保等多方面对循环流化床锅炉和煤粉锅炉进行了比较，凸显出选用循环流化床锅炉的优越性。     

Devolatilization and combustion of large coal particles in a fluidized bed

Devolatilization and combustion of large particles of Eastern Canadian coals (Evans and Minto), 5-50 mm dia., were studied in a bench-scale atmospheric fluidized bed reactor at 1023-1173 K with 0.5 mm sand particles as the bed material. The devolatilization time, mass loss history, changes in proximate volatiles content and C/H mass ratio, and temperature history at the centre of the particle during devolatilization were determined. The mass loss during devolatilization is correlated with the proximate volatiles content of the parent coal. The devolatilization time is correlated with the initial particle diameter by a power-law relation with an exponent of 1.54-1.64. The results show insignificant effect of superficial velocity on devolatilization.     

加压循环流化床富氧燃烧中试研究

二氧化碳捕集和封存技术(CCUS)是减少温室气体排放,实现全球环境可持续发展的有效技术手段。加压富氧燃烧技术是一种低成本CCUS技术。循环流化床燃烧技术(CFB)是目前商业化程度最好的清洁煤燃烧技术之一,加压循环流化床富氧燃烧耦合了加压富氧燃烧和循环流化床燃烧的诸多优点,具有很强的工业应用前景。但加压循环流化床富氧燃烧系统结构复杂,燃烧工况的切换和烟气再循环导致其在启动、控制、运行等方面面临巨大挑战。目前对于加压循环流化床富氧燃烧的研究大多处于理论建模、机理研究和小试试验阶段。为了更深入地探究加压循环流化床富氧燃烧的启动和运行方法,中国科学院工程热物理研究所在MW级加压循环流化床富氧燃烧中试试验平台上进行了中试研究,实现了加压富氧燃烧的稳定运行,获得了中试尺度加压富氧燃烧运行模式,以及启动和运行过程中温度、压力、给煤量和风量的变化曲线。加压富氧燃烧工况运行中整体O₂体积分数为29%,压力为0.30 MPa,功率为0.84 MW,尾部烟气中CO₂体积分数达91%,可较好地实现CO₂产品的捕集和压缩纯化。中试尺度加压富氧燃烧启动和运行的主要流程为:启动阶段-常压O₂/N₂燃烧阶段-常压富氧燃烧-加压富氧燃烧阶段,各阶段切换平稳。     

Modelling of circulating fluidized bed combustion of a char

The combustion of a char in the 41 mm ID riser of a laboratory circulating fluidized bed combustor has been investigated at different air excesses and rates of solids (char and sand) circulating in the loop. Riser performance was characterized by an axial oxygen concentration profile as well as by the overall carbon content and particle size distribution. The proposed model accounts for carbon surface reaction, intraparticle and external diffusion, and attrition. External diffusion effects were relevant in the riser dense region where char was potentially entrapped in large clusters of inert solids. Experimental data and results of the model calculations are in satisfactory agreement.     

Calcium sulphide formation in fluidized bed boilers

Analyses of samples of bed ash from a stationary fluidized bed boiler show the presence of calcium sulphide. In some samples, half of the total sulphur was present as sulphide. The samples containing CaS were obtained under unstaged conditions and with a high excess air ratio, 1.3 to 1.4. The samples were taken after a stop in the limestone addition, i.e. at high SO₂ emissions of about 1000 mL/m³ (ppm). No CaS was found during limestone addition when the SO₂ emission was 300–400 mL/m³. This indicates that formation of large amounts of CaS may be initiated as the SO₂ concentration exceeds some critical level.