Flow structure and combustion characteristic of 65 t/h oil shale-fired circulating fluidized bed riser—2: Dilute phase

In this paper, a 65 t/h oil shale-fired circulating fluidized bed (CFB) boiler was put into commercial operation in Huadian of China in 1996 and industrial hot experiment was done for studying the flow structure and combustion characteristic of CFB dilute phase regime. Flow structure and solid flux of dilute phase regime were investigated along both vertical direction and horizontal direction under different boiler loads. Particle-size distribution and carbon content of oil shale combustion residues were obtained. Experimental investigation shows that SO₂ concentration decreases with increasing the furnace height, and NO_X emission can be reduced by adopting staged combustion technology, low-temperature combustion and circulating combustion. Experimental results are valuable for adjusting the 65 t/h boiler and designing large-scale oil shale-fired CFB boiler. At the same time, the experiment lays a foundation for modeling the flow structure, combustion, heat transfer and abrasion of oil shale-fired CFB dilute phase regime.     

油页岩循环流化床燃烧特性研究

摘要:在循环流化床燃烧试验台上对油页岩的着火、稳定燃烧、燃尽特性等燃烧特性进行详细地试验方案分析,同时提出了油页岩循环流化床锅炉的设计与运行的特点。根据拟做试验方案进行试验研究,可以测试出油页岩的燃烧特性,为油页岩CFB锅炉燃烧特性的试验研究,以及大型化油页岩循环流化床锅炉的设计提供了借鉴。     

Regulating characteristics of loop seal in a 65 t/h oil shale-fired circulating fluidized bed boiler

In this paper, an industrial cold experiment was conducted for studying regulating characteristics of a loop seal in a 65 t/h oil shale-fired circulating fluidized bed (CFB) boiler. The starting characteristic of the loop seal, and the effect of the supplying air and the fluidizing air in the loop seal were investigated. Compared with other regulating modes, the combined regulating mode of keeping the fluidizing air rate constant and regulating the supplying air rate can make the loop seal obtain better regulating quality, and offer more reliable guarantee for steady operation of the CFB boiler as well. In order to prevent circulating material depositing and slagging at the bottom of the loop seal, it was suggested that the fluidizing air rate and the supplying air rate is 2-3 and 1.2-1.5 times of the minimum fluidizing velocity of circulating material, respectively. These experimental results may be used as a reference for regulating the loop seal of the 65 t/h CFB boiler in hot condition and designing a new loop seal.     

流化床内煤着火特性实验研究

为了对当前大量应用的带有床下启动燃烧器 CFB锅炉的启动运行提供指导 ,以及为从事循环流化床技术和煤燃烧理论研究提供参考 ,在电加热的小型流化床燃烧系统上 ,采用热烟气炉下点火的方式来研究煤粒在流化床内的燃烧特性 .测定了福建龙岩无烟煤的着火特性 ,分析了粒径、床温对着火点的影响 .并提出了煤颗粒在流化床内着火点测定的实验规范 .     

空气射流在密相实料层中的射流特性试验研究

循环流化床(CFB)布风板的风帽结构设计及其布置方式与风帽出口小孔空气射流在密相区的射流特性密切相关.在一可视化冷态试验台上,采用真实CFB锅炉床料,对不同直径的小孔在密相实料层中的空气射流特性进行了试验研究.提出并验证了小孔空气射流在密相实料层中的射程的定义.试验结果表明:小孔空气射流射程随射流初速和小孔直径的增大而...     

油页岩循环流化床燃烧室密相区物料颗粒与燃烧特性

在 65t/h油页岩循环流化床锅炉上进行了燃烧室密相区物料特性与燃烧特性的工业试验。得到了极具片状结构特点的油页岩颗粒特性 ,经燃烧破碎磨损后的密相区床料和循环物料的颗粒特性与燃烧特性及相应的锅炉运行参数。试验结果对油页岩循环流化床锅炉的放大设计与运行调节具有一定的参考价值。同时为进一步建立油页岩循环流化床燃烧室密相区的流动、燃烧、传热、磨损、扬析与夹带模型奠定了基础。     

Dynamic modeling and simulation of a 410 t/h Pyroflow CFB boiler

A modeling method for a large-scale circulating fluidized bed (CFB) boiler is presented. The method uses the cell approach to simulate the axial distribution of solid and gas phases in the bed and uses ‘core–annular’ construction to describe the radial distributions of solid particles and particle clusters. At the same time, it takes into account the influence of the wide size distribution of both bed and feed materials on hydrodynamics, chemical reactions and heat transfer. The steam side dynamic characteristics of the boiler are also considered based on the modular modeling method. Based on the method, simulations of static and dynamic performances of a 410 t/h Pyroflow CFB boiler are carried out. The results show that the model is capable of predicting the complete performance of the CFB boiler. The modeling method has important theoretical and engineering values for the research of combustion technology, large-scale design and operating performances of a circulating fluidized bed.     

Air Distributor Pressure Drop Analysis in a Circulating Fluidized-Bed Boiler for Non-reference Operating Conditions

The air distributor plays a key role in circulating fluidized-bed (CFB) boilers providing an even gas distribution in the cross section of the furnace. In most cases, this task under real conditions is very difficult to implement due to the destruction of the tuyeres. For this reason, the air distributors of many CFB boilers operate under conditions deviating from the design recommendations, which has a direct impact on the hydrodynamics of the fluidized bed and heat transfer conditions. This work reports studies on the performance of a tuyere-type air distributor utilized in a CFB boiler and working under non-reference operating conditions. Based on the results of simulation calculations, practical equations for a distributor pressure drop calculation have been derived taking into account a different degree of tuyere destruction.     

油页岩循环床锅炉中温分离回输系统Loop Seal工作特性的研究

在目前世界上投入商业运行最大容量的 65t/h油页岩循环流化床锅炉上 ,进行了全尺寸的中温分离系统中LoopSeal型返料装置的工作特性热态试验 ,得到了油页岩循环流化床燃烧中温分离回输系统中LoopSeal型返料装置的运行参数、温度特性及其循环物料的颗粒特性和含碳量分布 ,试验结果对油页岩循环流化床锅炉的放大设计与运行调节具有一定的参考价值     

油贡岩在流化床锅炉内着火和燃烧特性的试验研究

介绍了在自行设计的电加热流化床小型试验台上进行的桦甸油页岩着火、燃烧特性的试验结果,研究了床层温度、燃料粒径对桦甸油页着火指数的影响,并结合油页岩的元素分析、工业分析结果对实验结果进行分析。研究结果对燃用油页岩流化床锅炉的设计、优化流化床锅炉的启停和运行具有一定的参考价值。     

大型循环流化床锅炉整体动态模型的构成及其求解方法

介绍了构成大型商用循环流化床锅炉整体模型的燃烧系统、汽水系统以及烟风系统模型的建立及综合方法 ,并提出了一种求解整体模型的“双桢速”算法 .采用这种整体模型的构成及综合方法能够有效地求解具有复杂物理化学特性和结构的大型复杂系统模型     

循环流化床锅炉浅床运行技术及大型化分析研究

对小容量循环流化床（CFB）锅炉浅床运行技术进行了分析总结,浅床运行方式适合于燃用褐煤及高挥发分烟煤的CFB锅炉,可降低一次风机压头和风机电耗。对于中等容量CFB锅炉,浅床运行可能会导致密相区结焦及燃烧效率降低等问题,为降低飞灰及底渣可燃物含量,需要维持足够的床层高度或风室压力。对浅床运行模式的大型化问题进行了技术分析。     

Unburned carbon fraction with operation variables in a commercial circulating fluidized bed boiler during co-combustion of various anthracites

Reduction of unburned carbon fraction in exhaust during co-combustion of various coals in a circulating fluidized bed boiler (CFB) is required to save energy loss and to optimize coal utilization as well as to improve the boiler efficiency. In this study, the effects of operation variables such as coal, air and heat flow rates, co-combustion ratio of each coal, primary to secondary air ratio on unburned carbon fraction were analyzed and evaluated in two units of 200 MWe circulating fluidized bed boiler in the Tonghae thermal power plant. From the results, the comprehensive correlation among unburned carbon fraction and operation variables in #1 and #2 units of the CFB boiler could be derived with a good agreement. This would be expected to give a good guideline to reduce the unburned carbon content in exhaust in the CFB boiler.     

Characteristics of a Float Nozzle Designed for CFB Boilers

A float nozzle was designed and developed for use with large‐scale industrial circulating fluidized bed (CFB) boilers. The gas distributor equipped with the float nozzle has a unique pressure drop characteristic. It has a higher resistance than other nozzles which results in the formation of an effective barrier against backflow at low boiler loads, which results from the pressure fluctuation caused by bubble burst and solids coming from the recycle system. In addition, it has a relatively low pressure drop at high or full boiler loads, which can greatly reduce the energy cost of the primary air fan.     

燃煤循环流化床锅炉N_2O排放影响因素分析

阐述了CFB锅炉燃烧过程中N_2O的产生、消解机理,分析了燃料特性、床温、过量空气系数和煤中的矿物质成分等诸多因素对CFB锅炉N_2O排放的影响。分析了生物质与煤混合燃烧,炉膛后再燃,在CFB锅炉中添加催化剂以及反向分级燃烧等新型低N_2O燃烧技术,为CFB锅炉低N_2O排放技术指明了研究方向。     

流化床冷模布风板数值模拟研究

利用计算流体动力学(CFD)软件包fluent,研究流化床反应器中的气流通过冷模布风板时压降过大的问题。采用正交数值模拟仿真实验对不同的开孔形式和不同的开孔直径进行研究,分析了流化床内的速度场、压力场,确定出:(1)布风板开孔直径越小,压降越大,但流化床内的速度场越容易达到稳定;(2)布风板中心处尽量不要开孔;(3)布风板开孔直径相同时,排列方式为等边三角形比正方形时压降更小。     

Pilot Development of Polygeneration Process of Circulating Fluidized Bed Combustion combined with Coal Pyrolysis

A pilot polygeneration process of a 75 t h^–1 circulating fluidized bed (CFB) boiler combined with a moving bed coal pyrolyzer was developed based on laboratory‐scale experimental results. The process operation showed good consistency and integration between boiler and pyrolyzer. Some critical operating parameters such as hot ash split flow from the CFB boiler to the pyrolyzer, mixing of hot ash and coal particles, control of pyrolysis temperature and solid inventory in the pyrolyzer, and pyrolysis gas clean‐up were investigated. Yields of 6.0 wt‐% tar and 8.0 wt‐% gas with a heating value of about 26 MJ m^–3 at 600 °C were obtained. Particulate content in tar was restrained less than 4.0 wt‐% by using a granular filter of the moving bed. Operation results showed that this pilot polygeneration process was successfully scaled up.     

Effect of distributors on Gas—Solid Fluidization

The efficient operation of a fluidized bed is very much dependent upon distributor performance, which in turn depends on its design parameters. The work reported here deals with the characteristics of such distributors as are commonly employed in laboratories, pilot plant and large scale operations. Specifically a porous plate distributor, two bubble cap distributors of different geometries and four Johnson screen distibutors of different percent open area have been investigated in a 30.5 cm by 30.5 cm square fluidized bed as a function of air fluidizing velocity and bed height. The pressure drop data for all the distributors have been correlated by a single equation with two unknown constants. The ratio of distributor pressure drop to bed pressure drop is found to increase rapidly with increase in fluidization velocity. The bed expansion ratio is found to increase with increase in excess fluidization velocity and distributor pressure drop but decreases with increase in bed height or weight.     

水冷异型分离循环流化床燃烧技术

根据物料平衡理论分析了循环流化床锅炉分离器的选取原则,对各种分离器锅炉运行结果的测试认为分离器性能是影响燃烧效率的一个重要原因,但不能解决燃烧效率的全部问题,对循环流化床燃烧技术发展历史的回顾,认为冷却式分离 中国循环环床的发展方向。低成本的方形分离器在７５ｔ／ｈ等级的成功研制和运行的良好性能为该炉型的大型化提供了依据,目前在国家有关部门的支持下,１３０ｔ／ｈ和２２０ｔ／ｈ的设计工作已经基本完成４     

影响BT-75/4.4-M循环流化床锅炉床温因素分析

循环流化床锅炉的床温是循环流化床锅炉最重要的控制参数，它直接影响着整个锅炉的热效率和脱硫效率，从云天化股份有限责任公司的循环流化床锅炉的实际运行出发，分析了影响循环流化床锅炉床温的各种因素，其中主要因素有煤质、煤量、煤粒粒径、一次风、二次风、脱硫剂、循环灰量和床层高度等，据此选择出适合云天化循环流化床锅炉的床温，并利用返灰量来自动调节控制锅炉的床温。