Abstract Supercritical water gasification (SCWG) is famous for achieving complete conversion of raw organic matter with the temperature below its ash melting point. Inorganic mineral components associated with raw organic matter will form solid slag particles after the reaction of SCWG is completed. Discharge of the slag particles from reactor is a supercritical water (SCW) transporting particles process under transcritical temperature conditions driven by pressure difference. A comprehensive three-dimensional two-fluid model (TFM) is firstly developed in this study to research the flow dynamics characteristics during the particle transport process. The effect of transport pressure difference (ΔP) and particle outlet position (ΔH) on particle transport are investigated. Results show that the particles can be transported out the reactor smoothly under the action of ΔP, and the solid-containing ratio, sr, can reach to 78.27% with ΔP of 5 MPa and ΔH of 55 mm. Large ΔP can enhance particle transport efficiency, but it may cause fluid overheating in the cooler. When the particle outlet is close to the reactor inlet, a large amount of SCW from reactor inlet will enter the particle outlet, which will decrease the particle transport efficiency. The current model can reasonably describe the flow dynamics characteristics of particle transport process, which may provide theoretical guidance for the design and optimization of slag-discharge system.

中文翻译：

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压差驱动下跨临界温度条件下超临界水输送颗粒流动动力学特性的数值研究

摘要 超临界水气化（SCWG）以在低于其灰熔点的温度下实现原料有机物的完全转化而闻名。SCWG反应完成后，与原料有机物伴生的无机矿物成分会形成固体渣粒。从反应器排出炉渣颗粒是在压差驱动的跨临界温度条件下的超临界水 (SCW) 传输颗粒过程。本研究首次开发了一个综合的三维二维流体模型（TFM）来研究颗粒传输过程中的流动动力学特性。研究了输送压差（ΔP）和颗粒出口位置（ΔH）对颗粒输送的影响。结果表明，在ΔP的作用下，颗粒能顺利运出反应器，在ΔP为5 MPa，ΔH为55 mm时，含固率sr可达78.27%。较大的 ΔP 可以提高颗粒传输效率，但可能会导致冷却器中的流体过热。当颗粒出口靠近反应器入口时，来自反应器入口的大量SCW会进入颗粒出口，这会降低颗粒传输效率。该模型可以合理地描述颗粒输运过程的流动动力学特性，可为排渣系统的设计和优化提供理论指导。但它可能会导致冷却器中的流体过热。当颗粒出口靠近反应器入口时，来自反应器入口的大量SCW会进入颗粒出口，这会降低颗粒传输效率。该模型可以合理地描述颗粒输运过程的流动动力学特性，可为排渣系统的设计和优化提供理论指导。但它可能会导致冷却器中的流体过热。当颗粒出口靠近反应器入口时，来自反应器入口的大量SCW会进入颗粒出口，这会降低颗粒传输效率。该模型可以合理地描述颗粒输运过程的流动动力学特征，可为排渣系统的设计和优化提供理论指导。