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本文简要介绍了有关文献中循环流化术煤炭燃烧、气化及生物质气化的数学模型。根据中数学有所使用流体动力学模型的差异,将其分为鼓泡流化床数学模型,拟流体数学模型,区段数学模型,颗粒轨道数学模型及多维数学模型,并着重叙述了各模型所用到的流体动力学模型。 相似文献
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对循环流化床气化进行数值模拟研究可为气化炉设计、制造、运行提供指导。本文从热力学平衡模型和动力学模型两个方面综述了循环流化床气化数学模型。结果表明热力学平衡模型与实际气化过程相差甚远;双流体模型假设过于理想化,偏离实际;颗粒轨道模型计算量非常大,耗时很长;多维模型发展还不完善,需引入大量的经验公式;小室模型是模拟循环流化床气化较理想的模型。 相似文献
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《煤炭加工与综合利用》2016,(6)
基于软件提供的用户自定义方程添加的化学反应模块建立煤气化数学模型,利用商用CFD模拟了灰熔聚流化床的气化,找出了灰熔聚流化床气化炉的特有结构(中心管)进氧量对气化炉气化特性(碳转化率、炉内温度以及煤气组成成分)的影响,从而完善灰熔聚流化床煤气化反应理论,为现场的经济运行提供参考。 相似文献
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以煤催化气化制合成天然气技术为研究背景,内径0.2 m,高6 m,处理量为0.5 t/d的流化床气化炉为研究对象,建立了煤催化气化流化床气化炉的数学模型。将气化炉简化为3个区域:分布板区、气泡区和自由段区,基于稳态一维模型,考虑了加压下流体力学性质(最小流化速度、射流高度和直径、气泡直径和速度以及床层膨胀比),质量和热量传递,以及催化气化反应动力学(煤焦燃烧、水蒸气气化、变换和甲烷化)等因素对气化结果的影响。计算结果表明:当射流管引入氧气后,颗粒温度迅速达到最大值随后下降最后趋于平缓;氢气和二氧化碳浓度随着床高近似线性增加,但一氧化碳和甲烷随床高增加缓慢;3.1 MPa时最大气泡直径约为0.11 m,气化炉内不会发生节涌现象。计算床温和气体组成与实验结果有良好的一致性。 相似文献
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《化学工业与工程技术》2019,(1):12-16
介绍了循环流化床流态化及工作原理,分析了立管物料反窜时前后气化炉压差及温差变化情况,确定了中试装置的循环流化床在运行过程中产生立管物料反窜的原因,并提出了稳定返料系统阀门的操作、控制物料循环流动速率、控制好密封腿的气量和料腿的料位高度、保持气化炉流化状态稳定、调整流化气速为4~6 m/s、控制粉煤粒径为0.3~0.4 mm等解决方法。经优化改进后,确保了立管物料不反窜,使床层料位稳定,气化炉流化状态稳定,实现了循环流化床的长周期稳定运行,为循环流化床的工业化推进提供技术支撑。 相似文献
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对一种新型两段式水煤浆气化炉的气化效率进行了数值计算和分析。模型中将水煤浆的气化过程分为水分蒸发、煤热解、气相反应和气固异相反应等子模型。气相反应速率需同时考虑湍流混合和化学反应机理,气固反应的速率采用未反应缩芯模型。运用可实现k-ε模型描述气相湍流流动,随机轨道模型追踪水煤浆颗粒的运动。以中试多喷嘴水煤浆气化炉为建模基础,验证了该水煤浆气化模型的准确性。模拟计算得出新型两段炉的有效气组分含量为85.91%,冷煤气效率为76.42%。 相似文献
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一、煤气化炉的分类目前正在应用和开发的气化炉有很多类型。尽管我们把所讨论的气化炉局限在已经工业化的和大型示范装置的范围内,其数量仍然相当大。为了将这些气化炉进行合理的分类,通常考虑下列方面的物理因素: 固体燃料的运动状态: ·移动床·固定式流化床·气流式流化床成灰状态: 相似文献
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综述了充分发展湍流中气泡破碎的机理和模型,将其机理归纳为湍流涡碰撞、黏性剪切、尾涡剪切脱落过程和界面不稳定性四类。对文献中气泡破碎速率和子气泡大小分布的预测模型进行了系统总结。分析讨论了现有气泡破碎模型的发展和局限性,并提出了未来的发展方向。同时,也综述了湍流中单气泡破碎的实验研究,依据产生湍流的方法归纳为四种情况:增大液体流速产生湍流,采用内构件产生湍流,搅拌产生湍流,以及圆锥反应器结合搅拌产生湍流。总结了现有气泡破碎实验的进展和局限,并进行了分析和展望。最后,通过将文献中气泡破碎速率模型预测值和实验数据进行对比,表明文献中多个破碎模型已经有了较好的预测能力。 相似文献
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单个液滴蒸发模型中不同质量传递公式的有效性分析 总被引:11,自引:4,他引:7
液滴蒸发是液体喷雾的重要物理过程,文献中使用了不同的模型计算液滴蒸发中的质量流率。依据质量传递驱动力HM的处理,可将这些模型归类于三种不同形式,即经典模型、质量类比模型和漂移流动模型。本文对这些模型的来源和假设作了分析和总结,发现漂移流动模型考虑了Stefan效应和质量迁移,应为正确的表述,而经典模型忽略了瞬态效应,质量类比模型忽略了Stefan流效应。最后以两种不同蒸发率条件下的液滴蒸发为例进行计算,研究了不同质量传递驱动力对液滴蒸发的影响, 发现经典模型和质量类比模型都对液滴的蒸发估计过低,且高蒸发率下三种模型对液滴蒸发特性的影响更显著。 相似文献
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简要阐述了径向流固定床反应器在化学工程中的重要性及研究该类流动问题的迫切性,回顾了文献中描述该反应器中流体流动的六类数学模型,提出了设计准则及均布措施,指出了存在的问题及解决的途径. 相似文献
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Among the drying models available in the literature, the REA model (which was first proposed in 1996) is semi-empirical. It was described based upon a basic physical chemistry principle. The “extraction of water from moist material” is signified by applying the activation energy concept. The single expression of the extraction rate represents the competition between evaporation and condensation. It also encompasses the internal specific surface area and mass transfer coefficient, and thus is linked to material characteristics. The REA can be classified into two categories—Lumped (L) REA and Spatial (S) REA—which can be used to deal with drying a material as a whole or considering the local phenomena within the material, respectively. Both models have been proven to be very effective. The REA is effective for generating parameters since only one accurate drying run is required to establish the relative activation energy function. Both internal and external resistances are modeled by the REA. In its lumped format, the REA is employed to describe the global drying rate, while in the S-REA, the REA is used to model the local evaporation rate. This article covers fundamentals of the REA which have not been fully explained, as well as the most recent development and applications. The application of the S-REA as a non-equilibrium multiphase model is highlighted. 相似文献
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甲醇蒸汽重整制氢技术对于解决汽车、船舶等交通工具上燃料电池的氢源问题具有重要意义,近年来已成为碳氢燃料重整制氢的研究热点。本文首先综述了甲醇蒸汽重整制氢的5种反应机理,该方面的研究仍处于定性和推理阶段,尚未达成统一的结论。然后分析了甲醇蒸汽重整反应动力学的研究进展,发现大多研究是基于Cu系催化剂提出,反应温度集中在160~350℃,反应压力多为1atm,研究表明反应物水醇比最优值为1.3~1.4。最后,整理了研究中所提出的动力学模型,指出相较于单速率和三速率模型,双速率模型可反映产物中CO的含量及其对反应速率的影响,且模型相对简单,动力学方程的求解过程也相对容易,但其适用性还有待进一步验证。本文可为甲醇蒸汽重整制氢系统的设计与优化提供理论依据。 相似文献
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The dyeing of textiles was classified into two main categories: reactive and adsorptive dyeing. A mathematical model for each case was developed on the basis of a pore model concept. The validity of the proposed models was confirmed by comparison with existing experimental data on dyeing of reactive dyes in cellulose and acid dyes in nylon. It was further desired that the proposed models be checked by experimental results in high fixation regimes. The overdyeing phenomenon may be simulated by intrafiber diffusion with simultaneous multimodal adsorption. 相似文献
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Particulate systems are of interest in many disciplines. They are often investigated using the discrete element method because of its capability to investigate particulate systems at the individual particle scale. To model the interaction between two particles and between a particle and a boundary, conventional discrete element models use springs and dampers in both the normal and tangential directions. The significance of particle rotation has been highlighted in both numerical studies and physical experiments. Several researchers have attempted to incorporate a rotational torque to account for the rolling resistance or rolling friction by developing different models. This paper presents a review of the commonly used models for rolling resistance and proposes a more general model. These models are classified into four categories according to their key characteristics. The robustness of these models in reproducing rolling resistance effects arising from different physical situations was assessed by using several benchmarking test cases. The proposed model can be seen to be more general and suitable for modelling problems involving both dynamic and pseudo-static regimes. An example simulation of the formation of a 2D sandpile is also shown. For simplicity, all formulations and examples are presented in 2D form, though the general conclusions are also applicable to 3D systems. 相似文献