基于欧拉多相流模型的流化床煤气化过程三维数值模拟

以欧拉多相流模型为基础,气相采用k-ε湍流模型,固相采用基于颗粒动理学理论封闭模型,引入传热、传质、煤热解、气化过程反应模型,建立了流化床煤气化过程的三维数理模型,该模型同时考虑了稠密气固流动和相内、相间的化学反应.对直径0.22m的流化床煤气化炉不同操作参数下的气化过程进行了三维数值模拟,获得了气化炉内气化产物的组分分布、温度分布及化学反应速率变化规律.模型的计算结果与实验结果进行了比较,结果表明:数值模拟与实验吻合较好,最小相对误差仅为1%左右,最大相对误差为20%左右,平均相对误差小于14%.

流化床煤气化技术开发应用中遇到的一些问题及其解决途径

阐述流化床煤气化技术的优点与缺点,对各种流化床气化炉的情况及其发展状况进行介绍,指出目前我国对流化床煤气化技术有需求的两个可能市场及今后需解决的问题,最后对如何理解流化床气化的缺点提出观点及解决思路。

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。

一种循环流化床煤气化余热锅炉的设计开发

本文介绍了一种循环流化床煤气化余热锅炉的结构及其设计参数,可以为相关工程技术人员开发设计类似产品提供一定的参考。

新型循环流化床煤气化试验平台安装技术

新型循环流化床煤气化试验平台是进行煤炭能源清洁高效利用研究的重要试验设备,本文以大同市煤炭清洁高效利用研究所安装项目为例,对5t/d新型循环流化床煤气化试验平台中的钢架组合安装焊接和本体设备安装两个关键工艺进行总结探讨,可为类似项目安装提供借鉴。

基于MP-PIC模型的流化床煤气化过程三维数值模拟

本文以多相流质点网格模型(MP-PIC)为基础,采用欧拉-拉格朗日方法,建立了流化床煤气化过程的三维可压缩数理模型,该模型同时考虑了稠密气固流动,传热传质和相内、相间的化学反应。通过不同操作参数下模拟计算,获得反应器内的流型、气体组分分布、化学反应速率变化等规律。模型计算所得的出口气体组分与实验结果进行了比较,数值模拟与实验吻合。

灰熔聚流化床气化炉内气固两相流的数值模拟

应用欧拉双流体模型模拟了某化肥厂现运行的灰熔聚流化床煤气化炉(用ICC表示)内的气固两相流动行为,得出了所模拟ICC的合理流化气速与喷动气速的速度范围及匹配关系:流化气速不能太小,否则布风板区域会出现死区;流化气速也不能太大,否则将失去ICC的设计运行特点.当流化气速一定时,随喷动气速的增加,搅动混合增强,但过大的喷动气速会使床内的流动结构出现腾涌,不利于ICC的高效安全运行.

循环流化床气化细粉灰熔融特性研究

利用灰熔融性测定仪、X射线衍射仪、扫描电子显微镜研究了温度、气氛、残炭含量对茌平、宿迁循环流化床气化细粉灰熔融特性的影响。结果表明,弱还原气氛下两种气化细粉灰的熔融温度最低。高温下莫来石的出现导致宿迁气化细粉灰灰熔点明显高于茌平气化细粉灰。两种循环流化床气化细粉灰的熔融特征温度均随着残炭含量的上升而升高,当残炭含量超过3%,温度超过1300℃时,两种气化细粉灰均会产生碳硅石。碳硅石的存在是使气化细粉灰熔融性变差的主要原因。

粉煤流态化气化改性作用试验研究

在15 kg/h分级煤气化试验台的循环流化床单元上开展试验,利用激光粒度仪、比表面积和孔隙度分析仪、X射线衍射仪和X射线荧光光谱法等分析方法,研究流态化条件对粉煤改性作用的影响。结果表明:在进入流化床的氧气体积流量和煤的质量流量之比为0.31 m3/kg时,可以维持稳定的流态化过程,粉煤经过流态化煤气化改性,得到的半焦粒径减小,半焦的比表面积、总孔隙容积和碱性组分含量提高,灰熔融特征温度降低。

氧化亚铁对气化细粉灰熔融性的影响

循环流化床煤气化细粉灰残炭含量较高,对其进行资源化再利用能有效提高碳转化率。实验以一种气化细粉灰(来自循环流化床气化炉)为研究对象,利用X射线衍射(XRD)仪和扫描电子显微镜(SEM)、灰熔融仪,从矿物质转化以及灰渣微观结构2个方面,研究在高温还原性氛围下,氧化亚铁对灰熔融性的影响。结果表明,莫来石的存在导致气化细粉灰熔融温度升高;加入氧化亚铁后,钙长石和铁尖晶石等较低熔融温度的矿物质的生成,以及低温共熔现象的发生是灰熔融温度降低的主要原因。扫描电镜下拍摄的灰渣的微观结构验证了XRD的分析结果。

Numerical Simulation of Pressurized Spouted Fluidized Bed for Coal Semi-Gasification

Numerical simulation study is conducted for a pressurized spouted fluidized bed coal carbonizer, in which hydrodynamics of pressurized spouted fluidized bed, chemical reactions and energy balance are taken into account. The effect of operating conditions such as bed pressure, air and steam mass flow ratio, temperature on product compositions in the bed is investigated. According to the calculated results, bed pressure and bed temperature have the key effects on coal semi gasification.

Performance characteristics of fluidized bed syngas methanation over Ni-Mg/Al_2O_3 catalyst

The performance characteristics of isothermal fluidized bed syngas methanation for substitute natural gas are investigated over a self-made Ni–Mg/Al2O3 catalyst. Via atmospheric methanation in a laboratory fluidized bed reactor it was clarified that the CO conversion varied in 5% when changing the space velocity in 40–120 L·g-1·h-1but the conversion increased obviously by raising the superficial gas velocity from 4 to12.4 cm·s-1. The temperature at 823 K is suitable for syngas methanation while obvious deposition of uneasyoxidizing Cγoccurs on the catalyst at temperatures around 873 K. From a kinetic aspect, the lowest reaction temperature is suggested to be 750 K when the space velocity is 60 L·g-1·h-1. Raising the H2/CO ratio of the syngas increased proportionally the CO conversion and CH4 selectivity, showing that at enough high H2/CO ratios the active sites on the catalyst are sufficient for CO adsorption and in turn the reaction with H2 for forming CH4.Introducing CO2 into the syngas feed suppresses the water gas shift and Boudouard reactions and thus increased H2 consumption. The ratio of CO2/CO in syngas should be better below 0.52 because varying the ratio from 0.52 to0.92 resulted in negligible increases in the H2 conversion and CH4 selectivity but decreased the CH4 yield.Introducing steam into the feed gas affected little the CO conversion but decreased the selectivity to CH4. The tested Ni–Mg/Al2O3 catalyst manifested good stability in structure and activity even in syngas containing water vapor.

Three Stage Equilibrium Model for Coal Gasification in Entrained Flow Gasifiers Based on Aspen Plus

A three stage equilibrium model is developed for coal gasification in the Texaco type coal gasifiersbased on Aspen Plus to calculate the composition of product gas, carbon conversion, and gasification teml^erature. The model is divided into three stages including pyrolysis and combustion stage, char gas reaction stage, and gas p.hase reaction stage. Part of the water produced in thepyrolysis and combust!on stag.e is assumed to be involved inthe second stage to react with the unburned carbon. Carbon conversion is then estimated in the second stage by steam participation ratio expressed as a function of temperature. And the gas product compositions are calculated from gas phase reactions in the third stage. The simulation results are consistent with published experimental data.

Modularized dry coal beneficiation technique based on gas-solid fluidized bed

A 40-60 t/h modularized dry coal beneficiation process with a novel method to control the bed was designed around a gas-solid fluidized bed separator. Furthermore, the hydrodynamics of medium-solids consisting of wide-size-range magnetite powder （0.3-0.06 ram） and 〈1 mm fine coal were numerically studied. The simulation results show that the fluidization performance of the wide-size-range medium-solid bed is good. The separation performance of the modularized system was then investigated in detail using a mixture of 〈0.3 mm magnetite powder （mass fraction of 0.3-0.06 mm particles is 91.38 %） and 〈1 mm fine coal as solid media. The experimental results show that at separation densities of 1.33 g/cm^3 or 1.61 g/cm^3, 50-6 mm coal can be separated effectively with probable error, E, values of 0.05 g/cm^3 and 0.06 g/cm^3, respectively. This technique is beneficial for saving water resources and for the clean utilization of coal.

“三高”煤性质分析及其在KSY技术中的应用研究

为了拓展双流化床超大型粉煤气化技术(KSY技术)原料用煤范围,通过工业分析、元素分析、热失重实验、CO_(2)反应活性分析,探讨了山西晋阳某矿区煤(SXJYM)应用于KSY技术的可行性。分析结果表明:SXJYM灰分为24.11%,硫质量分数为3.55%,灰熔融性温度在1500℃左右,属于典型的“三高”煤,且其CO_(2)反应活性较低、热失重效果较差,单独作为KSY技术的原料用煤可能气化效果不佳;适量添加CaO可在一定程度上降低SXJYM灰熔融性温度;可通过将SXJYM与灰分较低、CO_(2)活性较好的新疆某矿区煤(XJM)进行级配,既能获得较好的气化效果,又可降低原料成本。

基于非均匀曳力模型的CFB循环特性研究

为了给工业级循环流化床(CFB)煤气化反应器的运行调试提供有效的参考依据,在操作参数之一--颗粒质量循环流率Gs未知的情况下,本文采用具有宽工况普适能力的QC-EMMS非均匀曳力模型和欧拉-欧拉数值方法,模拟了提升管内的气固两相流动,准确给出了该装置的循环特性,即不同流化风速下颗粒质量循环流率Gs与床存量的关系曲线,揭示了实际过程中可能存在的A类噎塞现象,以及发生噎塞前后,床内颗粒浓度分布的变化规律。研究表明,欧拉方法和QC-EMMS模型可在各类大型CFB系统运行的改进、放大和优化中发挥应有的重要作用。

Experimental and Modeling Investigation of Coal Gasification in a Fluidized Bed Reactor

This paper presents a new approach to study the process of coal gasification. Non-linear programming techniques are used to determine the value of the model parameters that depends on coal species and experimental conditions and thus minimize the difference between experimental results and model predictions. Model predictions being in good agreement with the experimental results show that this method of combining model with experiment is effective for modeling complex processes.

Circulating Fluidized Bed Gasification of Low Rank Coal：Influence of O2/C Molar Ratio on Gasification Performance and Sulphur Transformation

To promote the utilization efficiency of coal resources,and to assist with the control of sulphur during gasification and/or downstream processes,it is essential to gain basic knowledge of sulphur transformation associated with gasification performance.In this research we investigated the influence of O_2/C molar ratio both on gasification performance and sulphur transformation of a low rank coal,and the sulphur transformation mechanism was also discussed.Experiments were performed in a circulating fluidized bed gasifier with O_2/C molar ratio ranging from 0.39 to 0.78 mol/mol.The results showed that increasing the O_2/C molar ratio from 0.39 to 0.78 mol/mol can increase carbon conversion from 57.65%to 91.92%,and increase sulphur release ratio from 29.66%to63.11%.The increase of O_2/C molar ratio favors the formation of H_2S,and also favors the retained sulphur transforming to more stable forms.Due to the reducing conditions of coal gasification,H_2S is the main form of the released sulphur,which could be formed by decomposition of pyrite and by secondary reactions.Bottom char shows lower sulphur content than fly ash,and mainly exist as sulphates.X-ray photoelectron spectroscopy(XPS)measurements also show that the intensity of pyrite declines and the intensity of sulphates increases for fly ash and bottom char,and the change is more obvious for bottom char.During CFB gasification process,bigger char particles circulate in the system and have longer residence time for further reaction,which favors the release of sulphur species and can enhance the retained sulphur transforming to more stable forms.

The Development of Coke Carried-Heat Gasification Coal-Fired Combined Cycle

Carried-Heat Partial Gasification Combined cycle is a novel combined cycle which was proposed by Thermal Engineering Department of Tsinghua University in 1992. The idea of the system comes from the situation that the efficiency of the power plants in China is much lower than that of the advanced countries, but the coal consumption is much higher, which brings about the waste of primary energy resources and the pollution of the environment. With the deep study of the gasification technology, Coke Carried-Heat Gasification Coal-Fired Combined Cycle, as the improved system, came into birth in 1996 based on the partial gasification one. At the end of 1997, a new cycle scheme similar to IGCC was created. This paper focuses on several classes combined cycle put forward by Tsinghua University, depending on the plant configuration and carbon conversion, making the solution a viable and attractive option for efficient coal utilization.