Simulation of the 200 MWe tonghae thermal power plant circulating fluidized bed combustor by using IEA-CFBC model

The 200 MWe Tonghae thermal power plant CFB boiler (2-units) is the largest boiler to fire a Korean anthracite coal for generation of electric power. The #1 unit CFB has been operated commercially since October 1998, and the #2 unit CFB, which will begin commercial operation in October 1999, is currently under construction. However, there is little operational data of the large CFB combustor firing anthracite coal, so it is necessary to predict the performance of the CFB combustor with variation of the operation conditions. Therefore, in this study, the simulation of the Tonghae CFB has been carried out to predict the performance with various nominal rates, coal particle size distribution and operating conditions. The simulation results with various loads could be fitted well to the design values at the given operation conditions. At the various operation conditions, the simulation results could explain the performance of the Tonghae CFBC well.     

循环流化床锅炉床温动态简化模型

在分析了循环流化床锅炉床温动态特性的基础上,将循环流化床锅炉沿着炉膛高度方向分为密相区和稀相区2个部分,各个部分集中参数化,分别对2个部分进行氧浓度、床料质量、残碳质量以及总能量进行衡算,提出了以给煤、一次风、二次风以及排渣为操作变量的床温动态简化模型.最后采用MATLAB 6.5软件对所建方程进行求解仿真,结果证实了该模型的正确性.     

Effect of air flowrate on particle velocity profile in a circulating fluidized bed

The research was conducted in a cold flow circulating fluidized bed (CFB). The diameter and height of riser are 5 and 200 cm, respectively. The objective is to study effect of gas velocity on hydrodynamic of glass beads having mean diameter of 547 micron and density of 2,400 kg/m³. The measurement of particle velocity profile was achieved by using a high-speed camera and an image processing software. A probe of 0.5 cm in diameter was inserted into the riser at the height of 110 cm from gas distributor and was set at 3 positions along the radius of the riser; 0, 0.6, and 1.8 cm from center. Transport velocity (U _tr ), core-annulus velocity (V _CA ) and minimum pneumatic velocity (V _mp ) were employed in determining solid flow pattern in the riser. It was observed that the flow regimes changed from fast fluidization to core-annulus and to homogeneous dilute bed when the gas velocities increased from 7, 8 and 9 m/s, respectively. The results from high-speed camera showed that glass beads velocity existed a maximum value at the center of the riser and gradually decreased toward the wall for all three gas velocities. It was also found that most of solid traveled upward in the core of the riser, however, solid traveled downward was identified at the wall layer.     

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.     

Hydrodynamic behaviour of solid transport for a closed loop circulating fluidized bed with secondary air injection

The aim of this work was to study the mechanism of solid circulation in a Circulating Fluidized Bed pilot as a function of secondary air flow rate A rectangular column of 7 m height equipped with a U type siphon was used for this purpose The results obtained showed that the solid circulating phenomenon depends on different limiting steps like feeding step (dense bed), siphon circulating capacity and suspension saturation capacity.     

Fluidized bed ash cooler used in a circulating fluidized bed boiler: An experimental study and application

The performance of a fluidized bed ash cooler was studied using a cold experiment bench. The air flow rate, particle size of the solids and air distributor type are considered to be the key parameters of the operation of a fluidized bed ash cooler (FBAC). It was found that the amount of fluidizing air directly affects the conveying of ash and that they have a quadratic relationship. An acceptable particle size distribution for the solids is d₅₀ < 450 μm. Furthermore, the experiment reveals that the height of the weir in the FBAC does not affect the conveying of the ash flow. The influence of injected air on the transportation of ash is not significant. Optimal air nozzle dimensions are presented.     

电石渣用于循环流化床锅炉脱硫工艺的探讨

简要介绍了热电厂循环流化床锅炉运行现状，针对电石渣脱硫工艺进行了试验与分析，论证了电石渣应用于流化床锅炉脱硫的可行性。     

Characteristics of clinker formation in a circulating fluidized bed boiler firing Korean anthracite

To shed light on the causes of clinker formation during the initial operation period of the Tonghae circulating fluidized bed (CFB) boiler, which uses Korean anthracite as fuel, the properties of ash, sand and limestone particles and the mixtures of each gradient have been characterized. The clinkers formed in the loopseals and the fluidized bed ash cooler (FBAC) of the CFB boiler were also characterized by analyzing the composition, the surface phenomena and the crystal structure of the clinkers. As a result, the black clinker was found to come from the sand particles and the composition of the white clinker was found to be similar to that of ash particles. The cause of the clinker formation in the FBAC proved that ash was sticking to molten or sintered phases in the high temperature regions in the boiler. On the other hand, the composition of the ash changed with the particle size, showing an enrichment of Fe₂O₃ as the particle size decreased. Also, the ash particles between 75–100 μm contained more than 11% CaO which resulted in low initial deformation temperature of the particles. So it is possible to explain that the amount of Fe and Ca in the fine particles of the ash plays a crucial role in the formation of agglomerates in the CFB boiler.     

余热电站循环流化床锅炉给煤系统的改造

我公司回转窑余热电站HG—CPC65（45）-3．82／450℃型补燃锅炉机组是哈尔滨锅炉厂采用美国CPC公司技术设计制造的细粒子低速循环流化床锅炉。该炉以燃用煤矸石为主要燃料。给煤系统由变频调速圆盘喂料机控制给煤量，并通过给煤皮带机和机械风力抛煤机向炉膛供煤。     

Countermeasures against alkali-related problems during combustion of biomass in a circulating fluidized bed boiler

The purpose of this work was to study different ways to mitigate alkali-related problems during combustion of biomass in circulating fluidized beds. Wood chips and wood pellets were fired together with straw pellets, while the tendency to agglomerate and form deposits was monitored. In addition to a reference case, a number of countermeasures were applied in related tests. Those were addition of elemental sulphur, ammonium sulphate and kaolin to a bed of silica sand, as well as use of olivine sand and blast-furnace slag as alternative bed materials. The agglomeration temperature, composition and structure of bed-ash samples were examined. The flue-gas composition, including gaseous alkali chlorides, was measured in the hot flue gases and in the stack. Particles in the flue gas were collected and analysed for size distribution and composition. Deposits were collected on a probe in hot flue gases and their amount and composition were analysed. Addition of kaolin was found to be the best method to counteract the agglomeration problem. The deposition problem is effectively counteracted with addition of ammonium sulphate, while kaolin is too expensive to be used commercially against deposits, and sulphur is less effective than ammonium sulphate.     

20t/h循环流化床锅炉的运行调试

某化肥厂 2 0 t/ h循环流化床锅炉运行过程中存在过热器超温、飞灰含炭量高以及冒黑烟等问题 ,通过对锅炉运行的调试 ,找出了问题的原因 ,并提出了相应的对策 ,对今后继续开发和使用循环流化床锅炉具有一定的现实意义     

流化床锅炉旋风分离器中心筒的运行和检修

针对75t／h循环流化床锅炉旋风分离器中心筒多次损坏（开裂、变形、倾斜、脱落、挂钩脱落等）的原因进行了认真分析,有针对性的提出防范措施,并且不断完善修复方案,经检修改造后,该炉一直运行稳定。     

FW-420T/H型循环流化床锅炉安装特点及常见问题处理

结合天津石化100万t/a乙烯工程3x420t/h的循环流化床锅炉现场安装经验,对循环流化床锅炉的施工组织及施工方法进行了分析。针对流化床锅炉特有的膨胀节、风帽、锚固件、砌筑炉墙等部件的安装过程进行了详细探讨,同时也对试运过程中常见缺陷的处理进行了介绍。     

循环流化床锅炉粉煤灰的特点及其在水泥工业中的应用

详细地论述了循环流化床锅炉排放的粉煤灰（简称CFB锅炉粉煤灰）的特点及其在水泥工业中的应用。对比普通粉煤灰性能,CFB锅炉粉煤灰具有颗粒形貌不规则、产CaO和SO3含量高,以及以硬石膏和石灰作为主要矿物组成等特点。归纳介绍了CFB锅炉脱硫粉煤灰的应用情况,可代替部分原料用于生产水泥熟料或作为混合材用于生产水泥,但应用中要注意克服高f-CaO和SO3含量所带来的安定性问题。     

Analysis of model parameters affecting the pressure profile in a circulating fluidized bed

This study focuses on continuum model validation of the flow of air and small catalyst particles in a circulating fluidized bed. Comparison with available experimental data of pressure drop and solids circulation rate in the riser clearly demonstrates the need to modify the homogeneous drag model to accurately predict the formation of clusters of particles, which are typically observed in the fluidization of small particles. The need to correct the drag law is also demonstrated in simulations of polydisperse powder flows wherein three solids species are used to represent a typical catalyst size distribution. Finally, particle‐wall friction is found to have the most significant effect on the vertical gas pressure gradient while particle–particle friction has only a minor effect. Published 2011 American Institute of Chemical Engineers AIChE J, 58: 427–439, 2012     

A model for the pressure balance of a low density circulating fluidized bed

The pressure balance along the solid circulation loop of a circulating fluidized bed equipped with a solid flux regulating device has been modelled and the influence of the pressure balance on the riser behaviour has been predicted.The solid circulation loop has been divided into many sections, where the pressure drop was calculated independently: riser, cyclone, standpipe, control device and return duct. A new theoretical model, that is able to predict the pressure losses in the return path of the solid from the standpipe to the riser, has been built. A new correlation for cyclone pressure loss with very high solid loads has been found on the basis of experimental data.The pressure loss in the riser has been calculated by imposing the closure of the pressure balance, ΣΔP = 0. Once the riser pressure drop had been calculated, the holdup distribution along the riser was obtained by imposing a particular shape of the profile, according to the different fluid-dynamics regimes (fast fluidization or pneumatic transport). In the first case, an exponential decay was imposed and the bottom holdup was adjusted to fit the total pressure drop, in the second case, the height of the dense zone was instead varied.The experimental data was used to develop the sub-models for the various loop sections have been obtained in a 100 mm i.d. riser, 6 m high, CFB. The solid was made of Geldart B group alumina particles. The tests were carried out with a gas velocity that ranged between 2 and 4 m/s and a solid flux that ranged between 20 and 170 kg/m²s. A good agreement was found between the model and experimental data.     

Emissions during co-firing of RDF-5 with bituminous coal, paper sludge and waste tires in a commercial circulating fluidized bed co-generation boiler

Biomass fuel is the largest renewable energy resource and the fourth largest primary energy supply in the world. Because of its complex characteristics when compared to fossil fuel, potential problems, such as combustion system stability, the corrosion of heat transfer tubes, the qualities of the ash, and the emission of pollutants, are major concerns when co-firing the biomass fuel with fossil fuel in a traditional boiler. In this study, co-firing of coal with a biomass blend, including fuel derived from densified refuse, sludge, and waste tires, were conducted in a 130 ton/h steam circulating fluidized bed co-generation boiler to investigate the feasibility of utilizing biomass as a complemental fuel in a traditional commercial coal-fired boiler. The properties of the fly ash, bottom ash, and the emission of pollutants for various fuel ratios are analyzed and discussed in this study.     

循环床锅炉炉膛压降及轴向固体浓度的计算

本文提出了循环流化床锅炉炉膛的轴向压力及固体浓度分布的计算式。当给出表观气、循环固体流率以及颗粒性质时，可准确地预测炉膛压降与轴向固体浓度分布，为炉膛设计提供了计算依据。     

75t/h循环流化床锅炉爆管事故原因分析及处理

本文根据循环硫化床锅炉膜式壁爆管的现场调查,详细分析了锅炉爆管的原因,针对循环硫化床锅炉运行的实际情况和特点,提出了合理的处理意见和建议,进行了认真整改,进行了化学清洗钝化并加强锅炉水处理工作和日常管理工作,取得了良好的效果。     

Evaluation of new parboiled rice process using humidified hot air fluidized bed drying

This study aims to experimentally investigate the drying characteristics and quality of a paddy dried by hot air (HA) and humidified hot air (HHA) fluidization technique. Qualities such as head rice yield (HRY), white belly, degree of gelatinization (DSG), and color of dried paddy were evaluated. A paddy with an initial moisture content of 14% d.b. was soaked in hot water at a temperature of 70?°C for 5?h then dried at a temperature of 130,150, and 170?°C, relative humidity in the range of 0.3–12%, an air velocity of 3.9 m/s, and a bed height of 10?cm. The results showed that the drying time of the paddy in the HHA condition took longer than the HA drying condition. Because HHA provided a higher grain temperature and a slow rate of drying, the degree of starch gelatinization was significantly higher when compared to HA. The subsequent HRY was relatively higher than using HA drying. However, the color of the sample obtained from the HHA condition was relatively browner, but the parboiled rice product still had a light brown color for the drying temperature range used in this study. To produce parboiled rice, HHA could be operated up to the temperature of 170?°C, relative humidity of 6%, and DOM of 10%.