YG240型循环流化床锅炉临界流化风量的确定

循环流化床锅炉的临界流化风量是锅炉设计、运行的重要参数,结合ＹＧ２４０－３．８２／４５０型循环流化床锅炉临界流化风量的测试,提出了临界流化风量的测试方法,同时对影响循环流化床锅炉临界流化风量的测试,提出了流化风量的测试方法,同时对影响循环流化床锅炉临界流化风量参数的重要因素进行讨论。     

循环流化床锅炉循环回路的数值模拟与仿真

为研究循环流化床锅炉循环回路内的流动特性并提高燃料利用率,建立锅炉循环回路三维模型,并结合质量守恒方程和流动介质运动方程进行气-固两相流数值模拟与仿真分析。通过对横截面内固相含量分布云图的观察与剖析,得到了固相在炉膛内的分布规律。通过对不同截面固相体积分数的计算,获得了炉膛内轴向方向上固相的变化规律。对不同时间段炉膛内的压强进行计算,得到了炉膛内压强随时间变化的规律。通过分析速度矢量图,得到了炉膛内速度在空间上的分布规律。研究结果为循环流化床锅炉的改进设计和提高热利用率提供有利的借鉴。     

外循环流化床锅炉运行使用原理

据统计,目前已有上千台各种循环流化床锅炉投入运行．循环流化床锅炉的主要特点是物料（燃料和脱硫剂）经过多次循环．在炉膛内反复进行燃烧和脱硫反应,物料在燃烧过（略）状态．床温是保证循环流化床锅炉设备安全性和运行经济性的重要参数之一,是监视炉膛密相区燃烧和流化情况、防止炉膛结焦的重要依据,是控制炉膛燃烧的重要温度点,是灭火保护动作的重要条件。     

循环流化床底部区域流动特性的数值模拟

基于欧拉两相流模型计算循环流化床底部区域的流动特性。在低气速(1.0～2.5m/s)、低循环量下(5.2～34.5kg/(m2·s)),模拟时黏性采用层流模型取得了较好的效果。实验采用光导纤维探头测量仪测量流化床底部区域3个截面的局部颗粒浓度,模拟计算了循环流化床底部3个截面的颗粒浓度的径向分布,并同循环流化床装置的实验数据进行了对比。结果表明,数值模拟计算与实验结果相吻合。     

控制性气流粉碎技术制备等积球形墨粉

采用自制的控制性气流粉碎机制备等积球形墨粉,通过改变粉碎强度、第一级分级机转速和第一级分级机二次风量来控制墨粉的颗粒形貌,通过改变第二级分级机转速和第二级分级机二次风量来控制墨粉粒度分布的集中性。结果表明,在流化床粉碎强度为0.6 MPa,流化床底部二次风量为86 m3/h,第一级分级机电机变频器频率为17 Hz,第二级分级机电机变频器频率为36 Hz,第二级分级机二次风量为287 m3/h时,制得墨粉的粒度分布最集中,形貌最均匀,球形度最高,此时第二级分级机产量为72.5 kg/h,成品率为79.2%。     

循环流化床锅炉二次送风结构影响的数值模拟

利用CFD软件Fluent,基于颗粒动力学理论的双流体模型对循环流化床锅炉的3种二次风送风结构对炉膛内气-固两相流宏观流动特性的影响进行数值模拟,将3种结构下的计算结果进行对比分析。结果表明:二次风通常采用90°垂直入射的情况下,炉膛内颗粒的环-核分布结构及上稀下浓的分布不均匀性达到最大;二次风进口入射角为与轴向方向成60°向上入射情况下,炉膛内颗粒主要分布在炉膛中上部区域,不均匀程度减小,最有利于炉膛内的燃烧和提高传热效率,同时得到二次风的射流深度最大;二次风送入结构为渐缩型入射口的情况时,二次风射流深度最小,炉膛内偏流现象明显,在本文的操作条件下,并没有达到喷射的设计效果,还有待于进一步的研究。     

440t／h循环流化床锅炉床温及汽温的调整

循环流化床锅炉运行中经常碰到床温偏差大，或局部床温异常，通常出现这种情况的原因是给煤不均匀或流化风量不均。左右床温的偏差，会使炉膛左右温度偏差及炉膛出口温度偏差，造成炉膛内布置的屏式过热器与屏式再热器吸热不均，使过热汽温与再热汽温出现偏差。这时应及时调整左右给煤的均衡。     

循环流化床锅炉床温偏差大原因及分析

该文研究了某厂410 t/h哈尔滨锅炉厂制造的循环流化床锅炉在启动运行时发生的左右侧床温偏差大,左右侧床压偏差大的问题。通过从锅炉流化床的流化机理、布风板的设计原理、锅炉运行相关实际运行参数对比、锅炉风道和炉膛的结构等方面,进行了床温偏差大、床压偏差大的相关原因分析,同时还分析了引起炉内形成沟流造成流化下降的主要因素,合理解释了相关产生床温偏差的机理,最后从操作方面和改造方面制定了相关改善床温偏差大的有效措施。     

浅谈循环流化床锅炉生产运行技巧

大庆石化热电厂现有两台循环流化床锅炉,在燃用设计煤种时锅炉负荷为220t／h,短时最大工况可达240t／h,锅炉保证脱硫效率大于80%。锅炉在燃用设计煤种时,不投油长期安全稳定运行的最低负荷为锅炉的50％负荷,锅炉在大于等于60％负荷情况下保证设计蒸汽参数,锅炉各种运行情况下床温均匀,床表面温差最大不超过50℃,锅炉两侧烟温度不大于50℃。给煤机将煤送人落煤管,然后由风吹入炉膛,与流化状态下的的循环物料掺混燃烧,循环物料经炉膛进入分离室,锅炉燃烧所需空气分别由一、二次风机提供。     

液-固流化床最小流态化速度的数值模拟与验证

为使用计算颗粒流体力学(CPFD)的数值模拟法代替实验法，建立单管的液-固两相流化床实验系统；实验测量5种颗粒的最小流化速度；应用CPFD方法对单管液-固流化床模型进行数值模拟，比较5种颗粒的最小流态化速度的实验值与模拟值，并进行误差分析，验证数值模拟方法的正确性。结果表明：5种实验颗粒的最小流态化速度实验值分别为0.021 6、 0.036 7、 0.029 3、 0.055 5、 0.084 5 m/s; 2种公式验算值与实验值的最大相对误差小于10%,平均相对误差小于5%,证明实验结果是可靠的；5种模拟颗粒的最小流态化速度模拟修正值分别为0.024、 0.044、 0.041、 0.069、 0.062 m/s;颗粒S₁、 S₂、 S₄、 S₅的模拟修正值与颗粒E₁、 E₂、 E₄、 E₅的实验值之间的最小流态化速度的误差分别为11.1%、 19.9%、 24.3%、 26.6%,均为正向偏差且在工程允许范...     

Circulating particle flow and air bubble behavior at various superficial air velocities in two-dimensional gas–solid fluidized beds

Circulating particle flow and behavior of air bubbles in a two-dimensional gas-solid fluidized bed of various superficial air velocities are investigated by recording videos of movement of a plastic pellet put into the fluidized bed and rising air bubbles using a video camera. The movement velocity of the plastic pellet and properties of the air bubbles such as the bubble rising velocity and the bubble distribution coefficient, which shows the proportion of the bubbles erupting at the center of the bed surface, are measured by analyzing the videos. It is found that the plastic pellet moves following the circulating particle flow; the particles rise up at the center of a column and fall down near the side walls, and that the movement velocity increases with the superficial air velocity. The bubble rising velocity, the apparent erupting bubble size and the bubble distribution coefficient increase, and the bubble eruption frequency slightly decreases, with the superficial air velocity. These results indicate that the circulating particle flow is generated by the rising air bubbles. In particular, the fact that the air bubbles rise at the center of the column and coalesce with other bubbles is closely related to the generation of the circulating particle flow.     

Experimental study on gas-solid flow characteristics in an internally circulating fluidized bed cold test apparatus

A self-designed internally circulating fluidized bed cold test apparatus was built to investigate the gas-solid flow characteristics in a new kind of internally circulating fluidized bed furnace. The test material was circulating ash from a power plant CFB boiler. Optical fiber probes and differential pressure transmitters were employed for the measurements. The particle internal circulation rate and the solids holdup in the upper space of the furnace were studied by changing the fluidization air velocity in the main chamber, the height of partition wall and the initial static bed height. The results showed that with the increase of fluidization air velocity in the main chamber, the particle internal circulation rate increased at first then decreased. Meanwhile, the particle internal circulation rate decreased with the increase of the partition wall height and increased with the increase of initial static bed height in the main chamber. The solids holdup in the upper space of the internally CFB cold test apparatus was 1–4% of that in the normal CFB cold test apparatus. The proportion of particle external circulation rate was relatively low in the circulating system.     

粒径分布对循环床内颗粒速度分布的影响

利用激光相位多普勒粒子分析仪（PDPA），在截面尺寸为100mm×15mm的二维循环流化床实验装置上测量比较了平均粒径基本相同的3种不同粒径分布的玻璃珠颗粒在相同操作气速下的颗粒时均速度、脉动速度与数量密度的截面分布特性；初步考察了粒径分布对气固并流上行两相湍流流动行为的影响问题。     

Evaluation of direct quadrature method of moment for the internally circulating fluidized bed simulation with ultrafine particles

In the framework of the Euler-Euler gas–solid two-fluid model, the particle population balance equation is solved by the direct quadrature method of moment. The dynamic process of ultrafine particle movement and aggregation in an internally circulating fluidized bed is simulated. The distribution of the concentration and velocity of the agglomerates in the flow process is given, and the changes of the moments in the bed are shown. The effects of different breakage coefficients and inlet gas rates on the concentration distribution of agglomerates are compared. The results show that the particle size decreases with the increase of breakage coefficient, and the time required to reach steady fluidization state increases; the higher the inlet velocity, the better the effect of circulating particles in the bed. When there is a certain gas velocity difference between the two sides, the effect of circulating particles in the bed is better.     

稀相气-固流化床分选电厂磨机返料中黄铁矿的实验与模拟

为了降低燃煤电厂的磨机功耗,减少锅炉燃烧后的污染排放,通过分析磨煤机分离器返料的粒度和密度分布,对电厂采样物料进行稀相流化床分选去除黄铁矿等矿物质的实验研究,并对物料分选过程进行数值模拟。结果表明,粒径小于0.500 mm的分离器返料在流化床中具有较小的起始流化速度1.62 cm/s,流化床各层的密度和粒度具有很好的稳定性;物料中的黄铁矿等矿物质得到分离,上层和底层物料灰分质量分数分别为33.34%、73.42%,硫分质量分数分别为1.12%、8.96%,底层物中硫主要以黄铁矿的形式存在;气-固两相流稀相分选床的流场形态及颗粒运动数值模拟验证了实验结论。     

循环流化床锅炉用旋风分离器性能的实验研究

结合水煤浆流化-悬浮燃烧的特点,通过全面测定循环流化床锅炉用旋风分离器在不同操作参数下的分离效率,研究了入口气速、入口颗粒浓度、入口颗粒物性等对旋风分离器的压降和分离性能的影响规律。实验结果表明,影响旋风分离器分离性能的主要物性参数是颗粒的中位粒径、密度,在入口颗粒的中位粒径相差较大时分离性能主要受粒径的影响,而当入口颗粒粒径相差较小时密度对分离器分离性能的影响则更为显著。     

Evaluation of sorption-enhanced reforming over catalyst-sorbent bi-functional particles in an internally circulating fluidized bed

An internally circulating fluidized bed (ICFB) has been applied in various industrial processes owing to its potential in the reduction of heat loss and compact size. In this work, the sorption-enhanced reforming process in the ICFB is investigated. The dense discrete phase model (DDPM) is employed to evaluate the performance of catalyst-sorbent bi-functional particles, considering the particle size distribution. The results demonstrate that the utilization of bi-functional particles can significantly increase hydrogen production. The impacts of operating parameters including solid loading and regenerator velocity on solid circulation rate and gas leakage are examined. It is found that the gas leakage between reactors is increased by 46.6% when the regenerator gas velocity varies from 1.8 m/s to 2.4 m/s so as to weaken the hydrogen yield.     

PIV investigations on particle velocity distribution in uniform swirling regime of fluidization

In this study, hydrodynamics of spherical particles in uniform swirling regime of a fluidized bed were investigated using MATLAB supported particle imaging velocimetry (PIV). A least investigated mesh-type distributor was used to fluidize the bed particles, at different air entry angles, for future applications in coating and granulation industry. A quarter of the bed was photographed using high speed imaging technique and the respective velocity fields of the swirling particles were produced using PIV technique. The Gaussian distribution of the particle velocity profiles was predicted at low superficial air velocity; particles near the border of the bed showed relatively low velocity than that swirled in the middle of the test section. However, at high superficial velocity, the particles near the central cone moved with velocity comparable to the particle velocity in the middle of the test section. Contrarily, the particles in the vicinity of the outer bed-wall maintained their steady state motion at all superficial air velocities. The average particle velocity experienced monotonic increase for more angular air intake. The magnitude of the particle velocity reduced by 6.35% for each \(3^{\circ }\) increment in the air entry angle.     

Experimental fluid dynamics of particles in a dielectric barrier discharge plasma-enhanced spouted bed

This study proposed the fluidized particles with dielectric barrier discharge (DBD) plasma in a slot-rectangular divergent-base spouted bed and focused on the dynamics of solid particles with the plasma irradiation. Two bed materials (Polypropylene (PP) particles and Polyamide (PA) particles) with same diameter (3 mm) were fluidized in this study. Fluidization parameters included gas velocity (7.4–14.9 m/s), particle amount (100–500), and plasma parameter (apply voltage, 0 and 7 kV) as the applied voltage were investigated here. Particle velocity profiles were analyzed through the methods of particle image velocimetry (PIV) and particle tracking velocimetry (PTV). Results show that the particle velocity was increased with the plasma irradiation, mainly by the enhancement in the vertical direction. The location of the highest particle velocity area related to the fluidization behavior of particles. With the increase of superficial gas velocity, the location of the highest particle velocity area raised along the central line but not reached the top of the solid bed. While the electron temperature of Ar plasma decreased with the addition of particles. Two electric fields (external electric field and surface charge electric field) presenting in the system were assumed to give the reason for the changes of the particle fluid dynamics.