Numerical simulation of the bubbling fluidized bed coal gasification by the kinetic theory of granular flow (KTGF)

A new numerical model based on the two-fluid model (TFM) including the kinetic theory of granular flow (KTGF) and complicated reactions has been developed to simulate coal gasification in a bubbling fluidized bed gasifier (BFBG). The collision between particles is described by KTGF. The coal gasification rates are determined by combining Arrhenius rate and diffusion rate for heterogeneous reactions or turbulent mixing rate for homogeneous reactions. The flow behaviors of gas and solid phases in the bed and freeboard can be predicted, which are not easy to be measured through the experiments. The calculated exit values of gas composition are agreed well with the experimental data. The relationship between gas composition profiles with the height of gasifier and the distributions of temperature, gas and solid velocity and solid volume fraction were discussed.     

灰熔聚流化床粉煤气化技术加压大型化研发新进展

灰熔聚流化床粉煤气化技术历经20余年的研发和工程化放大,低压气化技术已日趋成熟,并用于氮肥企业原料气改造和新建甲醇合成厂。该气化技术可使用不同灰含量和灰熔融性温度的煤,过程效率也较高,符合我国资源特点。为此在山西省发展和改革委员会的支持下,中科院山西煤化所和山西晋煤集团合作成立的“山西省粉煤气化工程研究中心”正在建设3.0MPa加压灰熔聚流化床粉煤气化中试平台,2006年年底已建成,预计于2007年3月进行加压气化试验,2007年完成加压灰熔聚流化床煤气化工业装置设计软件包的编制,形成具有我国自主知识产权、适应中国煤炭特点的大规模加压灰熔聚流化床粉煤气化技术。本文介绍了灰熔聚流化床粉煤气化过程,指出它的优点、缺点、适用范围、技术现状和发展方向,并对加压灰熔聚气化中试技术进行了简介。     

煤气化过程的模型和模拟与优化操作

介绍了煤气化过程的模型和煤气化过程采用机理模型的理由，固定床煤气化过程机理模型的建立以及模拟计算的结果，并探讨了固定床水煤气化炉和流化床水煤气炉制气过程优化操作参数的确定。开发的数学模型已用于制气炉的模拟计算，与实测数据比较符合，由气化过程的数学模拟气化过程不同条件下各种参数的变化规律，进而可得出气化过程的优化操作条件，其确定过程比试验法安全，省时，省料。     

Production of ultrapure hydrogen from biomass gasification with air

An integrated process has been proposed for the production of ultrapure hydrogen from biomass gasification with air. The process consists of an air-blown bubbling fluidized bed gasifier, a steam reformer, and a water-gas-shift membrane reactor. A non-isothermal model has been developed to simulate the fluidized bed gasifier, and a one-dimensional model has also been developed to simulate the steam reformer. The simulation results are compared with the experimental data, and good agreement is obtained. Based on the simulation results, the thermodynamic analysis of the integrated process is carried out. The simulation and analysis provide a quantitative tool for gaining insight into the process.     

灰熔聚气化炉内气体与固体混合特性的研究

气化炉内的气化剂与煤粉的混合特性直接影响着气化炉内的碳转化率和灰熔聚流化床气化炉的热效率。研究气化炉内气体和固体颗粒的混合特性,掌握炉内气体和固体颗粒的轴向和径向的运动规律,对认识床内传热和传质机理具有重要的意义。基于欧拉双流体模型,结合颗粒动力学理论,应用商用FLUENT软件,对太原化学工业集团有限公司运行的灰熔聚流化床气化炉内的气体与固体的混合特性进行了数值模拟。     

流化床煤气化技术的研究进展

结合流化床煤气化过程原理和循环流化床反应器开发应用状况,综述了流化床煤气化技术的进展,分析比较了目前广泛应用的3种煤气化流化床:鼓泡流化床,循环流化床及增压流化床的工艺及特点,并对工业上应用的典型的煤气化流化床(高温温克勒(HTW)及灰熔聚气化)的气化工艺流程具有的优势和存在的问题进行了较为详细的分析,并概括了流化床煤气化技术的发展趋势及应用前景.     

加压流化床煤气化炉衬里材料的选择与烘制

加压流化床煤气化技术是近年来随着洁净煤技术的兴起而发展起来的新一代大型、先进煤气化技术。就加压流化床煤气化炉耐火衬里的特殊要求进行了耐火材料的选型,并根据所选耐火材料特性制定了烘炉工作曲线,并比较了烘炉所需实际燃料气量和估算值,结果表明计算值与实际值吻合较好,并为大型流化床反应器的烘炉工艺制定和实施提供一种理论参考和估算方法。     

煤气化技术的发展与应用

综述了煤气化技术的现状及发展趋势,对煤气化技术的原理进行了阐述,概括介绍了固定床、流化床和气流床三种不同煤气化技术的特点,并对鲁奇炉、德士古炉、壳牌炉、恩德炉等几种常用气化炉的性能做了比较,重点介绍了恩德粉煤气化炉的发展历史、特点及应用现状,认为恩德粉煤气化技术具有自己独特的优势,是国内实力比较薄弱的合成氨企业进行技术改造的适宜技术.     

流化床-气流床耦合反应器中煤气化特性

利用化工动力学软件CHEMKIN建立了流化床-气流床耦合反应器等效网络模型,在φ300 mm反应器中的煤气化实验结果基础上,充分考虑耦合反应器不同区域物料间两相流动、传质传热,对耦合反应器各部分流体力学特征以及耦合反应器中不同区域的化学反应进行了分析。利用模型对飞灰的碳转化率、耦合反应器的碳转化率、耦合反应器内温分布及物料停留时间进行计算,结果表明,流化床耦合气流床反应器后,气流床可将出口飞灰碳转化64.1%,实现了耦合反应器对飞灰的再气化;耦合反应器煤气化系统的碳转化率由单独流化床的84.9%提高到92.2%。     

串行流化床煤气化试验

针对串行流化床煤气化技术特点,以水蒸气为气化剂,在串行流化床试验装置上进行煤气化特性的试验研究,考察了气化反应器温度、蒸汽煤比对煤气组成、热值、冷煤气效率和碳转化率的影响。结果表明,燃烧反应器内燃烧烟气不会串混至气化反应器,该煤气化技术能够稳定连续地从气化反应器获得不含N₂的高品质合成气。随着气化反应器温度的升高、蒸汽煤比的增加,煤气热值和冷煤气效率均会提高,但对碳转化率影响有所不同。在试验阶段获得的最高煤气热值为6.9 MJ•m^-3,冷煤气效率为68％,碳转化率为92％。     

我国煤气化技术的特点及应用

介绍了我国煤气化技术的发展现状;论述了固定床间歇气化技术、恩德炉粉煤流化床气化技术、灰熔聚煤气化技术、壳牌煤气化技术、德士古水煤浆加压气化技术、四喷嘴对置式水煤浆气化技术等煤气化技术的工艺特点、技术优势和不足;针对煤气化技术的选择提出了相关注意事项。     

华亭粉煤流化床气化

华亭矿粉煤经小型流化床气炉试烧表明,该煤种较为适合于直接粉煤气化,产气可作为化肥厂的原料气。     

加压喷动流化床煤部分气化数值模型

对加压喷动流化床部分煤气化进行了数值模拟,采用对流动分区法和化学反应速率法进行计算,模型考察了设计参数、运行工况、煤种特性对煤的气化影响,研究了在喷动流化床中压力对煤气化影响,模型计算结果表明,系统压力、反应温度是影响煤部分气化的最关键因素。     

昭通褐煤气化扩大试验研究

针对昭通褐煤的特点 ,在气化煤量为 0 .3t/h的焦载热流化床气化扩大试验装置上进行了试验研究 .研究结果表明 ,煤气中焦油量很小 ,有利于煤气生产的后期处理 ;与移动床气化和普通流化床气化相比 ,煤气热值和气化产率都有较大增加 ,煤气热值已接近城市煤气的要求 ;加大气化煤量可增加提升段燃烧的易燃成分 ,从而提高了燃烧温度和气化温度 ;气化煤量的变化对褐煤气化产率和产量的影响较大 .对于开发昭通褐煤资源来说 ,采用本工艺技术生产城市煤气是一个较佳的方案 .     

Experiment and mathematical modeling of a bench-scale circulating fluidized bed gasifier

The gasification of two different coals and chars with CO₂ and CO₂/O₂ mixture in a 48-mm-i.d. circulating fluidized bed (CFB) gasifier is investigated. The effects of operation condition on gas composition, carbon conversion and gasification efficiency were studied. A simple CFB coal gasification district mathematical model has been set up. The effects of coal type and CFB operating conditions on CFB coal gasification are discussed based on the CFB gasification test and model simulation. The main operation parameters in CFB gasification system are coal type, gas superficial velocity, circulating rate of solids and reaction temperature. It is found that CO concentration and carbon conversion increase with increasing solids circulating rate and decreasing gas velocity due to the increase in gas residence time and solids holdup in the CFB. The carbon conversion increases with increasing temperature and O₂ concentration in the inlet gas. The experimental results prove that the CFB gasifier works well for high volatile, high reactivity coal.     

鼓泡流化床内高灰煤气化过程的颗粒尺度特性研究

基于多相流体质点网格方法(MP-PIC)对高灰煤在三维鼓泡流化床气化过程进行了数值模拟研究。在欧拉-拉格朗日框架下将气相和固相分别视作连续介质和离散相处理。首先,将模拟得到的出口处气体组分结果与实验数据进行对比,实验数据与模拟结果具有良好的一致性。其次,研究了煤颗粒在气化炉内的温度、传热系数、速度和停留时间,从颗粒尺度揭示了鼓泡流化床气化炉内的颗粒分布特性和气固流动特征。结果表明:在气化炉入口附近煤颗粒与床层温差最大,传热系数最大;由于流化床内强非线性的气固流动,床中煤温度和传热系数的空间分布不均匀;煤颗粒和床料的瞬时速度具有稳定的波动幅度,其中垂直方向速度波动最明显,且煤颗粒的瞬时速度比床料的瞬时速度略大;由于颗粒间的剧烈碰撞,延长了煤颗粒停留时间。此外,对鼓泡流化床中煤气化过程颗粒尺度的研究,有助于深入了解固体颗粒的流动行为以及气固相相互作用特性,对鼓泡流化床反应器的设计优化具有重要意义。     

流化床水煤气炉运行结果分析

阐述了流化床水煤气炉的结构、工艺流程及其特点, 对该炉使用非粘性煤和粘结性煤的连续运行结果进行了分析, 指出该炉在中国煤气化中有着广阔的应用前景。     

A new integrated approach of coal gasification: the concept and preliminary experimental results

The total carbon conversion of conventional fluidized bed gasifier is relatively low (<90%) mainly because of carbon loss in fly-ash. In this paper, a new concept of integrated coal gasification—fluidized bed+entrained flow is introduced. Within this process, large partition of coal with higher reactivity is converted in an ash agglomerating fluidized bed reactor under moderate temperature (~1000 °C). The remaining small partition of coal (fly-ash) with lower reactivity is converted in a small integrated entrained flow gasifier under higher temperature (1200–1400 °C). Low carbon content ash is withdrawn in dry mode by ash agglomerating, with no need to be melted. Preliminary experimental results show that the whole system can be operated steadily, total carbon conversion reaches >95%, efficient gas (CO+H₂) concentration is 78–82%. Heat exchange between two reactors has been realized, the high temperature gas from entrained flow gasifier can be cooled, and in the mean time the temperature of fluidized bed nearly keeps constant. The high-temperature ash from entrained flow gasifier can be cooled by the char in dense phase of the fluidized bed and then withdrawn in agglomerating mode. All these results prove the concept correct and feasible.     

Cogasification of blended coal‐biomass in an air/steam BFB gasifier: Experimental investigation and model validation

A series of cogasification experiments were performed at a 100 kW bubbling fluidized bed (BFB) gasifier to gasify the blended pellets made from two types of coals and woody biomass, with biomass‐to‐fuel mass ratios of 0–30%. In the cogasification, a mixture of air and steam was fed from the BFB gasifier bottom as gasification agent and the blended biomass‐coal pellets were fed into the bed layer. Impacts of biomass mass fraction in the binary pellets and gasification operation temperature on producer gas composition were experimentally investigated. The experimental results have been used to validate a mathematical model developed in this study. From both experimental observation and model prediction, it was found that adding biomass into coal has overall negative impact on producer gas quality in terms of combustible substance contents, and the extents of the blending effect were different among fuel types which have different properties. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1639–1647, 2015     

Fluidized bed gasification of coal

Gasification of high ash India coal has been studied in a laboratory-scale, atmospheric fluidized bed gasifier using steam and air as fluidizing media. A one-dimensional analysis of the gasification process has been presented incorporating a two-phase theory of fluidization, char gasification, volatile release and an overall system energy balance. Results are presented on the variation of product gas composiiton, bed temperature, calorific value and carbon conversion with oxygen and steam feed. Comparison between predicted and experimental data has been presented, and the predictions show similar trends as in the experiments.