Artificial neural network models for biomass gasification in fluidized bed gasifiers

Artificial neural networks (ANNs) have been applied for modeling biomass gasification process in fluidized bed reactors. Two architectures of ANNs models are presented; one for circulating fluidized bed gasifiers (CFB) and the other for bubbling fluidized bed gasifiers (BFB). Both models determine the producer gas composition (CO, CO₂, H₂, CH₄) and gas yield. Published experimental data from other authors has been used to train the ANNs. The obtained results show that the percentage composition of the main four gas species in producer gas (CO, CO₂, H₂, CH₄) and producer gas yield for a biomass fluidized bed gasifier can be successfully predicted by applying neural networks. ANNs models use in the input layer the biomass composition and few operating parameters, two neurons in the hidden layer and the backpropagation algorithm. The results obtained by these ANNs show high agreement with published experimental data used R² > 0.98. Furthermore a sensitivity analysis has been applied in each ANN model showing that all studied input variables are important.     

流化床煤气化技术的工业应用

介绍了几种典型的流化床煤气化炉 ,重点阐述了一种自主开发的流化床水煤气发生炉的工艺、结构、水煤气的组成和污染物的排放等 ,分析了流化床煤气的特点并与流化床燃煤技术进行了比较。认为流化床煤气化技术的开发值得我国锅炉制造行业的重视。     

不同煤种下循环流化床灰渣特性的试验研究

在一台 0 .5MW的循环流化床燃烧炉上对 4种不同煤种分别进行燃烧试验 ,对燃烧产生的灰渣的分析结果表明了煤种特性如挥发分、灰分和含碳量等对循环流化床燃烧过程的灰渣形成及其排放特性有很大影响 ,并获得了煤中挥发分、灰分及含碳量对底渣粒径及其含碳量、飞灰粒径及其含碳量、飞灰份额及燃烧效率等影响特性 ,对循环流化床锅炉的设计和运行有一定的指导意义。     

褐煤在鼓泡流化床和循环流化床燃烧的汞迁移试验研究

对褐煤在小型电加热鼓泡流化床和小型电加热循环流化床中燃烧时的汞迁移特性进行了对比试验研究,重点考察了不同燃烧工况对汞迁移特性的影响。试验结果表明,炉膛温度和给煤量增加,鼓泡流化床和循环流化床的烟气总汞HgT均增加,飞灰颗粒汞含量Hg(p)均减少,并且循环流化床的烟气总汞HgT值均低于相同燃烧工况的鼓泡流化床值,循环流化床的飞灰颗粒汞含量Hg(p)值均高于相同燃烧工况的鼓泡流化床的值;流化风速增加,循环流化床的烟气总汞HgT减少,飞灰颗粒汞含量Hg(p)增加,鼓泡流化床烟气总汞HgT增加,飞灰颗粒汞含量Hg(p)减少。     

Experimental study on 75 kWth downdraft (biomass) gasifier system

Experimental study on 75 kW_th, downdraft (biomass) gasifier system has been carried out to obtain temperature profile, gas composition, calorific value and trends for pressure drop across the porous gasifier bed, cooling–cleaning train and across the system as a whole in both firing as well as non-firing mode. Some issues related to re-fabrication of damaged components/parts have been discussed in order to avoid any kind of leakage. In firing mode, the pressure drop across the porous bed, cooling–cleaning train, bed temperature profile, gas composition and gas calorific value are found to be sensitive to the gas flow rate. The rise in the bed temperature due to chemical reactions strongly influences the pressure drop through the porous gasifier bed. In non-firing mode, the extinguished gasifier bed arrangement (progressively decreasing particle size distribution) gives much higher resistance to flow as compared to a freshly charged gasifier bed (uniformly distributed particle size). The influence of ash deposition in fired-gasifier bed and tar deposition in sand filters is also examined on the pressure drop through them. The experimental data generated in this article may be useful for validation of any simulation codes for gasifiers and the pressure drop characteristics may be useful towards the coupling of a gasifier to the gas engine for motive power generation or decentralized electrification applications.     

Influence of CFB (circulating fluidized bed) boiler bottom ash heat recovery mode on thermal economy of units

CFB (circulating fluidized bed) boiler bottom ash contains large amounts of physical heat. A BAC (bottom ash cooler) is often used to treat high temperature bottom ash to reclaim heat, and to have the ash easily transported. The unit thermal economic indicators of three CFB power plants in China were derived based on heat balance calculation and analysis on the principled thermal system in turbine heat acceptance condition, taking the influence of two different bottom ash heat recovery modes into account. One of the two bottom ash heat recovery modes was the FBAC (fluidized bed ash cooler) mode, and the other was the RAC (rolling-cylinder ash cooler) mode. The results indicated that two modes both improved the thermal economy of units. Compared with the RAC mode, the FBAC mode obtained higher plant thermal efficiency, lower plant heat rate and less standard coal consumption. The standard coal consumption rate of the FBAC mode was less nearly 2 g/(kW h) than the RAC mode in the three CFB power plants, when the net calorific power of standard coal was 29.27 MJ/kg.     

生物质气化焦油在高温木炭床上的裂解试验研究

在高温木炭床裂解炉上,对以木粉为原料的120Kw鼓泡流化床气化炉产生的气化气中的焦油进行了裂解研究,采用溶剂冷态捕集焦油和称重分析相结合的方法对裂解前、后的焦油含量进行了测量.结果表明,在高温木炭床上发生的木炭吸附焦油、焦油的高温裂解和木炭灰催化裂解焦油等一系列的物理化学过程,可有效降低燃气中的焦油含量,同时可以获得热值为5MJ/m^3的可燃气.     

流化床启动过程中底料磨损行为研究

以国内首台自主研发的65t/h低倍率油页岩循环流化床锅炉底料灰为研究对象,在小型流化床试验台上考察了流化风速、流化时间和床层温度等因素对底料磨损程度的影响,据此建立了二阶磨损模型.结果表明：流化状态下页岩灰的磨损先后经历快速衰减和稳定磨损2个阶段,页岩灰在流化床内的质量保持率呈指数衰减趋势;随着流化风速增大,床层温度升高,磨损相对加剧;二阶磨损模型能够很好地描述流化床内页岩灰质量的变化规律.     

循环流化床锅炉物料平衡分析

循环流化床物料平衡是循环流化床燃烧的核心和基础,它影响到循环流化床燃烧效率和脱硫效率,并决定燃烧室内的热负荷分布。循环流化床“一进二出”的物料平衡系统是循环流化床的核心概念,也是理解循环流化床物料平衡的关键。本文介绍并分析了循环床物料平衡的某些问题,如循环流化床定态设计、床料质量和物料平衡模型等。循环流化床运行需要高的“床料质量”和较大物料循环量,要求流化床锅炉分离器分离效率曲线存在一个清晰的100％分离粒径截止点。循环流化床内物料平衡除了受分离器效率影响外,还受到给煤成灰及磨耗特性、床内颗粒分层、排渣方式及效率等因素的影响。     

循环流化床锅炉飞灰中碳的形成机理

通过对循环流化床(CFB)锅炉飞灰含碳量分布及飞灰残碳形态的测量、CFB燃烧温度下焦炭失活过程的试验研究以及流化床条件下煤颗粒燃烧过程的分析.探讨了循环流化床锅炉飞灰中碳的形成机理.结果表明:实际运行的CFB锅炉飞灰中含碳量具有明显的不均匀性,残碳集中于25～50 μm的飞灰颗粒内;真实密度和XRD测量均表明,焦炭失活的2个条件是温度和时间,温度高于800℃,焦炭失活开始发生,并且随着时间的增加,失活程度提高;焦炭颗粒长时间停留在主循环回路中,反应活性下降,由于颗粒的碎裂和磨耗,形成了飞灰中粒径较小的残碳;煤中的细小煤粒首次通过炉膛时未燃尽且未被分离器收集,形成了飞友中较大颗粒的残碳.     

有关循环流化床锅炉的几个问题探讨

本文就循环倍率、炉膛温度、炉膛高度等循环流化床 (CFB)锅炉中常遇见的问题进行了分析和探讨。目前CFB锅炉存在的主要问题之一是如何降低飞灰可燃物含量和提高锅炉燃烧效率 ,相应的研究飞灰可燃物的形成、燃烧特性等对CFB锅炉的设计有着现实的意义。     

循环流化床燃烧技术在改造GD35／3．82—114B型沸腾床锅炉中的应用

本文介绍了DG35／3．82－114B型沸腾床锅炉存在的能耗高,污染严重等问题,提出了采用循环流化床燃烧技术对其进行改造的技术方案和措施,并对其改造后的效果和经济效益进行了分析。     

Gasification of lignocellulosic biomass in fluidized beds for renewable energy development: A review

A literature review on gasification of lignocellulosic biomass in various types of fluidized bed gasifiers is presented. The effect of several process parameters such as catalytic bed material, bed temperature and gasifying agent on the performance of the gasifier and quality of the producer gas is discussed. Based on the priorities of researchers, the optimum values of various desired outputs in the gasification process including improved producer gas composition, enhanced LHV, less tar and char content, high gas yield and enhanced carbon conversion and cold gas efficiency have been reported. The characteristics and performance of different fluidized bed gasifiers were assessed and the obtained results from the literature have been extensively reviewed. Survey of literature revealed that several industrial biomass gasification plants using fluidized beds are currently conducting in various countries. However, more research and development of technology should be devoted to this field to enhance the economical feasibility of this process for future exploitations.     

A cold model experimental study on the flow characteristics of bed material in a fluidized bed bottom ash cooler in a CFB boiler

IntroductionA fluidized bed bottom ash cooler is often used totreat high temperature bottom ash to reclaim heat andfine particles from the ash, and to have the ash easilytransported. Among the large CFB boilers in operation inthe world, there are many ash coolers that often workabnormally['-','].There are six fluidized bed bottom ash coolers in theimported 410im CFB boiler that was built and operatedin Gaoba power plant, Sichuan province, China in 1996N].High temperature slag-bond and jam …     

生物质混流式固定床气化炉运行特性分析

以桉木为原料,对1.5 t/h生物质混流式固定床气化炉运行特性进行了测试分析与评价,与文献报导报道的相关炉型包括上吸式、下吸式、两段式等炉型运行结果进行了比较。实验以气化炉空气通入量作为主要控制变量,对有或无水蒸气条件下的气化炉温度及压力分布、燃气组成、焦油与飞灰含量、气体产率等参数进行了较长周期的测试,结果表明：气化炉运行效果符合设计要求,各项指标相当于或优于传统的下吸式气化炉;气化炉运行温度与压力比较稳定;以冷燃气计算的燃气热值一般约为4 900 ~ 5 500 kJ/Nm3;气化效率约为70% ~ 78%;燃气焦油含量约600 ~ 3 500 mg/Nm3,运行负荷在50%以上时,焦油含量一般低于1 500 mg/Nm3。研究结果有望为混流式气化炉的改进和操作提供优化建议,同时可为其他气化工艺设计提供参考依据。     

Effect of circulating ash from CFB boilers on NO and N2O emission

NO and N₂O emissions from circulating fluidized bed (CFB) boilers are determined by their formation and destruction rates in the furnace. The effect of circulating ash from a CFB boiler on NO and N₂O emissions were investigated in a laboratory-scale fluidized bed reactor. The results show that the residue char in circulating ash and the CO generated from the char play an important role in NO reduction and N₂O formation; however, active components of circulating ash such as CaO, Fe₂O₃ accelerate the decomposition of N₂O. Experiment was also conducted on a 75 t/h CFB boiler fueled with the mixture of anthracite and biomass. The lower residue carbon content of circulating ash in this experiment is lower; therefore, the reacting rate of NO deoxidize is limited. This result verified the conclusion of laboratory research.     

生物质气化过程中焦油的生成

总结了生物质气化过程中焦油的生成和分类,以及气化炉炉型、温度与氧量对焦油生成量和组成的影响规律。初级、二级和三级焦油是应用最为广泛的一种分类方法;不同炉型气化炉产气中焦油质量浓度从大到小依次为:上吸式流化床下吸式,分别在100,10,1g/m~3的量级,两段式等改进炉型在焦油控制上更有优势;上吸式气化炉焦油多为初级组分,下吸式则以无取代基的多环芳香烃等三级焦油为主,而流化床的焦油涵盖了二、三级焦油组分;温度的升高使得焦油量下降,且趋向于转化为化学结构更稳定的三级组分;氧量的增多对焦油的生成具有抑制作用。     

Physicochemical properties and gasification reactivity of the ultrafine semi-char derived from a bench-scale fluidized bed gasifier

Zhundong coalfield is the largest intact coalfield worldwide and fluidized bed gasification has been considered as a promising way to achieve its clean and efficient utilization.The purpose of this study is to investigate the physieochemical properties and gasification reactivity of the ultrafine semi-char,derived from a bench-scale fluidized bed gasifier,using Zhundong coal as fuel.The results obtained are as follows.In comparison to the raw coal,the carbon and ash content of the semi-char increase after partial gasification,but the ash fusion temperatures of them show no significant difference.Particularly,76.53％ of the sodium in the feed coal has released to the gas phase after fluidized bed gasification.The chemical compositions of the semi-char are closely related to its particle size,attributable to the distinctly different natures of diverse elements.The semi-char exhibits a higher graphitization degree,higher BET surface area,and richer meso-and macropores,which results in superior gasification reactivity than the coal char.The chemical reactivity of the semi-char is significantly improved by an increased gasification temperature,which suggests the necessity of regasification of the semi-char at a higher temperature.Consequently,it will be considered feasible that these carbons in the semi-char from fluidized bed gasifiers are reclaimed and reused for the gasification process.     

流化床燃烧煤的成灰磨耗特性

循环流化床燃烧条件下，煤的成灰磨耗特性是影响床的流化特性和锅炉整体性能的重要因素之一。将煤在床内爆裂和燃尽引起的尺寸减损和颗粒的磨耗视为相互独立的两个过程，利用静态燃烧然后冷态流化的方法，得到成灰与磨耗参数，提出煤种的本征成灰数据概念，认为煤种的本征成灰数据应视为只与煤种本身特性有关的燃料特性参数，建议将其作为设计循环流化床锅炉的燃料数据。     

CFB锅炉物料循环实现的条件

提出了大量物料参与循环是ＣＦＢ锅炉区别ＢＦＢ锅炉的主要特征的观点,讨论了ＣＦＢ锅炉物料循环实现的条件,并对国产ＣＦＢ锅炉出力不足的原因进行了分析。