共查询到16条相似文献,搜索用时 203 毫秒
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固态渣层能够保护气流床气化炉的水冷壁,防止其受到高温合成气直接辐射以及液态熔渣的侵蚀。本文提出一种数值模拟渣层热应力的改进方法,并应用该改进方法对降温阶段渣层热应力的变化进行模拟研究。在渣层热应力的数值模拟研究中,经常假定水冷壁渣层的热应力变化基于一个固定的参考温度(比如环境温度25℃)。然而对于降温阶段的水冷壁气流床气化炉,一个固定的参考温度值并不能表征渣层"无应力"的初始状态,在此基础上计算将会得到一个不合理的渣层应力分布结果。针对该问题,提出了一种改进方法:将水冷壁渣层分割为多个子计算域,每个子计算域内单独设置参考温度,以此实现在整个水冷壁渣层上施加一个近似为降温初始时刻的参考温度分布,从而使渣层在降温初始时刻处于"无应力"状态。同时,对前人文献中的三维水冷壁渣层结构在降温过程中的热应力变化情况进行计算,以此测试改进方法的准确性,改进方法得到的模拟结果与其他参考文献得到的渣层热应力变化趋势一致。 相似文献
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《耐火材料》2018,(6)
针对水冷壁式粉煤气化炉在使用过程中由热应力引起的耐火材料和渣层损毁现象,建立了水冷壁的局部热应力模型,运用ANSYS有限元分析软件对水冷壁式粉煤气化炉使用过程的应力场进行了数值模拟研究。结果表明:1)水冷壁式气化炉的最大应力出现在锚固钉与耐火材料的界面以及耐火材料与渣层的界面,渣层最大应力的位置在渣层表面。2)渣层厚度的增加可显著降低锚固钉与耐火材料界面处的热应力,但是会导致渣层与耐火材料层间的热应力增大。3)当热导率为2~6 W·m~(-1)·K~(-1)时,随着热导率增加,会导致热应力迅速升高;而当热导率为6~10 W·m~(-1)·K~(-1)时,热应力基本稳定。4)降温速率越快,炉衬各点的温度和热应力下降得越快。 相似文献
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通过将3D气化炉模型、熔渣一维流动传热模型和颗粒壁面捕捉模型耦合,对工业水煤浆水冷壁气化炉内的熔渣流动特性进行模型研究。重点分析了颗粒壁面行为对气化炉结渣的影响以及氧煤比变化对于渣层厚度的影响,并简要分析了水冷壁气化炉和耐火砖气化炉的差异。研究结果表明:大粒径颗粒易于被壁面捕捉,利于穹顶和直筒段渣层的形成,但不利于碳转化率的提高;小粒径颗粒具有高碳转化率,是下游细灰的主要来源,容易加剧下游受热面和灰黑水系统的负担;水冷壁气化炉内形成的固态渣层是气化炉热阻的主要组成部分,能够起到"以渣抗渣"的作用。 相似文献
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浅议壳牌气化炉的炉温调节 总被引:1,自引:0,他引:1
0引言壳牌气化炉内部采用膜式水冷壁结构,用来转移反应产生的热量,并产生废热蒸汽。水冷壁表面附着一层耐火材料,煤粉和氧气、蒸汽在1 600℃的高温下瞬间完成燃烧反应并生成熔融态灰渣,在4个烧嘴对喷产生的旋流作用下,熔融灰渣被甩到水冷壁表面。原始开车时,液态熔渣在耐火衬里及其内置的金属销钉的热传导作用下冷却固化,附着在水冷壁上形成了原始挂渣,渣层增厚到一定程度时热传导作用减弱,外表渣层就变成了熔融态,并向下流淌而使渣层厚度减薄。当厚度降低到一定程度时,热传导作用增大,使熔渣温度降低而固化,渣层重新聚积增厚,这样不断维持动态平衡,实现“以渣抗渣”,保护水冷壁免受高温烧蚀和熔渣冲蚀。渣层的厚度主要取决于炉内温度,炉温的波动会造成渣层厚度的变化。过厚的渣层会使气化炉下部堵渣而停车;过薄的渣层会失去对水冷壁的保护作用。 相似文献
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水冷壁气流床气化炉的核心思想是"以渣抗渣",因此对熔渣沉积形态与流动规律的研究尤为重要。文中在实验室小型水冷壁气化炉热模装置上,以神府煤气化灰渣、柴油和纯氧气为原料模拟气流床水冷壁气化实验,采用高温内窥镜并结合数字图像处理技术研究了熔渣的沉积、流动过程。实验结果表明:气化炉操作温度高于熔渣临界黏度温度时,渣层表面灰渣处于熔融状态;运动到壁面处的灰渣颗粒主要被熔融渣层吸收;熔渣的流动速度和渣层表面温度有关系,渣层表面温度越高,熔渣流动速度越大。在实验条件下,熔渣层表面速度约为0.002 6—0.003 m/s。 相似文献
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Numerical modeling for non-steady thermal stress analysis of slag layer in a membrane wall entrained-flow gasifier 总被引:1,自引:0,他引:1
Membrane wall entrained-flow gasifier (MWEFG) generally has a long service life for the protection of the solid slag layer adhered to the metal wall during operation. However, cracking will generate in the slag layer when the temperature changes greatly in the gasifier, which results from the thermal stress exceeding the strength of slag deposit. In this study, the gasification experiment was performed in a bench-scale MWEFG and a three-dimensional model was developed for non-steady thermal stress analysis of slag layer. Based on experimental data, the thermal stresses of cooling process were numerically simulated using transient thermal analysis. The results indicate that the thermal stresses of the slag layer are tensile during the cooling and the Von Mises stresses (SEQVs) increase with the reduction of temperature. Comparing the results of the selected nodes, it is found that the SEQV always increases from the slag surface to the slag-SiC interface. The contributions of slag porosity and thickness were also investigated. We draw a conclusion that the maximum SEQV decreases with the increasing porosity, while it increases with the increasing slag thickness. 相似文献
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建立了气流床煤气化炉煤灰渣颗粒沉积和壁面反应模型,相应完善了渣层流动、传热传质和相变模型,发展了数值模拟方法,并以国内某型两段式干煤粉加压气流床煤气化中试炉为对象进行了模拟。利用建立的模型可以得到壁面反应速率、渣层含碳量、固态渣层厚度、液态渣层厚度、渣层平均温度和液态渣层平均速度等。结果表明:氧煤比升高,渣层平均温度升高,固态渣层厚度、液态渣层厚度和气化炉出口灰渣含碳量降低。计算得到的灰渣含碳量在14%左右,整体碳转化率为95.2%左右,与实际值相近。通过模拟发现壁面反应对于所分析气化炉的碳转化率、排渣含碳量、壁面渣层流动和温度状态具有重要影响,进而影响气化炉的安全稳定运行。 相似文献
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Conclusions A model and a computer program using it have been developed making it possible to evaluate the influence of the electrical conditions after melt-down in an electric arc steel melting furnace on the thermal operation of tubular water cooled elements of the lining.The calculation is made for steady and nonsteady thermal conditions and makes it possible to determine the following parameters of thermal operation of the element: the temperature distribution across the layer of lining slag and tube wall; the temperature losses with the water and the water temperature at the exit of the element; the equilibrium lining slag thickness for a specified arc radiant power and heat exchange conditions in the furnace space.The heat losses with the water of a tubular wall panel of a DSP-100I6 furnace (tube diam. 76 mm and wall thickness 12 mm, lining slag thickness 20 mm, water consumption 5 m3/h per m2 of panel) after meltdown of the heat were calculated.The equilibrium thickness of the lining slag decreases with a reduction in its melting point and in increase in arc radiant power Pa.rad.Translated from Ogneupory, No. 6, pp. 40–43, June, 1988. 相似文献
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超/超超临界锅炉垂直水冷壁中间集箱附近的水冷壁异形鳍片区域向火侧易出现横向裂纹,可能导致水冷壁泄漏或爆管。以某660 MW超超临界锅炉为对象,介绍了水冷壁异形鳍片区域温度和热应力的数值计算模型。针对横向裂纹问题,基于计算数据分析了该区域的温度和热应力分布特征,以及锅炉负荷变化和水冷壁尺寸的影响。结果表明,异形鳍片旁的管壁向火侧顶点的轴向拉应力和等效应力大,锅炉变负荷运行易产生交变热应力,导致横向裂纹;异形鳍片中心为整个模型温度最高处,轴向应力和等效应力值也较大,需要重点关注;异形鳍片与管壁交接处等效应力大,材料失效时容易产生裂纹,可能向旁边的异形鳍片区域管壁向火侧延伸。 相似文献
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Cheol-Oong Kim Ryang-Gyoon Kim Zelin Wu Chung-Hwan Jeon 《Korean Journal of Chemical Engineering》2016,33(6):1767-1776
A mathematical model is developed to simulate a pilot Shell entrained-flow coal gasifier. Submodels of specific structures of the gasifier are established to simulate the complicated gasification process. The model includes the total energy conservation equation and mass conservation equations for the gas components, solid flow, and gas flow. It simulates the influence of the gasifier structure and dimensions and can calculate the effects of changing almost every important operation parameter, e.g., the syngas composition, gasification temperature, carbon conversion ratio, walllayer temperature, and slag mass flow rate. The model can predict the syngas composition under a limited residence time condition. Furthermore, it considers the heat transfer coefficient of each layer of the water wall to calculate its heat loss and temperature. Thus, the model also reflects the influence of performance parameters of the gasifier’s water wall. The slag mass flow rate on the wall is calculated using a slag submodel. 相似文献
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A new type of entrained flow gasifier with membrane wall and two-stage oxygen supply is being developed in China. The fraction of the secondary oxygen in total oxygen (FSO) is an important parameter for this kind of gasifier. A dynamic reduced order model (ROM) based on a reactor network model (RNM) is developed for this gasifier, which is used to investigate the effects of FSO on the slag layer thickness profile on the wall and explore the potential of FSO in dynamic slag control. The ROM adopts a flexible RNM blocking method, which varies with FSO to account for the influence of FSO on the flow pattern in the gasifier. Available industrial data was used to validate the model and a detailed sensitivity analysis for the calculation of slag layer thickness was performed. Static analyses show that FSO has a marked effect on the slag thickness distribution and higher FSO leads to lower heat loss through the wall. Finally, a slag control system, which introduced FSO as an auxiliary regulator, is proposed. Dynamic simulation shows that the new control system offers an improved performance in slag control and can broaden the regulating range of operating temperature. 相似文献