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首页> 外文学位 >Modeling circulating fluidized bed riser and downer reactors and their application to fluid catalytic cracking.
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Modeling circulating fluidized bed riser and downer reactors and their application to fluid catalytic cracking.

机译：模拟循环流化床提升管和下降管反应器及其在流化催化裂化中的应用。

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Circulating Fluidized Beds (CFB) are highly effective reactors for fast gas-solid reaction systems. In spite of extensive research in this area, the degree of understanding of these types of reactors is far from complete. The importance of further improving the CFB operation becomes especially evident when applied to Fluid Catalytic Cracking (FCC). Due to the large throughput rates in FCC, any betterment in the CFB technology leads to significant economic and environmental impacts for this process.; In this work, hydrodynamic models are presented describing each of the conventional CFB riser and the relatively new CFB downer. These two models predict flow parameters along the reactor axis based on fundamental fluid mechanics, which is supplemented with empirical correlations when necessary. Simulation results of the riser and downer hydrodynamic models compare favourably with extensive data collected on a state-of-the-art experimental unit having a riser and a downer of equal dimensions, each operated under similar conditions. The fact that both models match this data very well indicates that the computer programs depict the up-flow and down-flow CFB fluid dynamics realistically, and the riser and downer models are used to conduct a comparative study of riser and downer hydrodynamics.; The FCC reaction kinetics is incorporated in both the riser and downer hydrodynamic models for prediction purposes. Resulting riser and downer FCC models calculate flow and reaction parameters, including conversion rates, product yields and selectivity. Predictions for both riser and downer FCC operation match available data well, which verifies both reactor models. A comparative study of downer vs. riser FCC performance is carried out for conditions that prevail in industry in order to discern the circumstances under which either reactor may supply more desirable results such as higher conversion rates and improved product yields. A sensitivity analysis is conducted that encompasses the effect of reactor temperature, catalyst-to-oil ratio, the attainable suspension density within the reactors, the various types of catalysts and the degree of backmixing, on reactor performance. These findings may be useful for optimal operation of industrial units as well as for suggesting when it may be worthwhile to switch from riser to downer operation.
机译：循环流化床（CFB）是用于快速气固反应系统的高效反应器。尽管在该领域进行了广泛的研究，但是对这些类型的反应堆的理解程度还远远不够。当应用于流化催化裂化（FCC）时，进一步改善CFB操作的重要性变得尤为明显。由于FCC的吞吐率高，因此CFB技术的任何改进都会对该流程造成重大的经济和环境影响。在这项工作中，提出了描述每个常规CFB立管和相对较新的CFB立管的流体力学模型。这两个模型基于基本流体力学来预测沿反应堆轴线的流动参数，必要时可通过经验相关性对其进行补充。提升管和下降管流体动力学模型的仿真结果与在具有相同尺寸的提升管和下降管的最新实验装置上收集的大量数据相比具有优越性，每台均在相似的条件下运行。这两个模型都很好地匹配了该数据，这一事实表明计算机程序真实地描述了CFB向上和向下流动的流体动力学，而上升和下降模型则用于对上升和下降流体力学进行比较研究。 FCC反应动力学同时纳入上升和下降流体动力学模型中，以进行预测。最终的上升和下降FCC模型计算流量和反应参数，包括转化率，产物收率和选择性。上升和下降FCC运行的预测与可用数据很好地匹配，从而验证了两个反应堆模型。为了确定工业上普遍使用的条件，对下降管和上升管的FCC性能进行了比较研究，以便确定在哪种情况下反应器可以提供更理想的结果，例如更高的转化率和更高的产品收率。进行了敏感性分析，其中包括反应器温度，催化剂与油的比率，反应器内可达到的悬浮液密度，各种类型的催化剂以及反混程度对反应器性能的影响。这些发现对于工业设备的最佳运行以及建议何时从立管转换为下管运行可能是有用的。

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