浮阀精馏塔汽相偏流的形成机制及其调控方法的研究

Vapor channeling is one of the most important causes for the operation failure when a valve tray distillation column has scaled up. The study of this project would propose a formation mechanism for the vapor channeling. The differential valve working state as well as the differential vapor-liquid contacting state induced by the effects of hydraulic gradient on the valve tray, would lead to the instability of this flow system, and then to a gradual balance of being the two phase local flow, that is, the vapor channeling. Based on this mechanism, the effects of hydraulic gradient on valve trays caused by the two-phase flow friction on the stability of flow system would be studied, according to a cold simulator with the dimension being 1500×600 mm2. Meanwhile, the effects of the flow friction and differential vapor-liquid contacting state on the liquid height distribution would also be studied. Combined these researches with the stable conditions of a vapor-liquid flow system (i.e., the two-phase flow system has the lowest energy), the gas-liquid differential contacting state model would be established. Then the model would be used to simulate the gas-liquid flow state on valve trays, and the comparison between simulation results and the experimental results would be carried out to test the hypothesis proposed in this project. Further, the comprehensive strategies would be proposed to regulate the vapor channeling, which are direct against the two-phase flow friction, gas-liquid contacting regime, valve working state etc. It is expected that the study of this project could provide the basis for the reliable design and the mathematical simulating amplification of a valve tray column.

汽相偏流是浮阀精馏塔放大后，引起操作失效的重要原因之一。本项目基于提出的流动摩擦阻力产生液面落差诱导塔板上形成差异化浮阀工作状态及汽-液接触状态，引起汽-液流动系统失稳，进而建立汽相局部流动的两相流动结构是偏流形成机制假说的基础上，拟通过1500×600 mm2矩形冷模试验塔，研究流动摩擦阻力产生的液面落差对浮阀塔板上汽-液流动系统稳定性的影响；研究浮阀塔板上流动摩擦阻力和差异化汽-液接触状态对液层高度分布的影响；在这些研究的基础上并结合汽-液流动系统稳定的条件(汽-液流动系统能量最低)，建立差异化汽-液接触状态模型，通过该模型模拟浮阀塔板上汽-液流动状态并与试验结果对比，验证所提机制假说；进一步地分别从流动摩擦阻力、汽-液接触状态及浮阀工作状态方面针对性地提出调控浮阀塔板上汽相偏流的策略。可以预期，本项目的研究可为浮阀精馏塔可靠设计和数学模拟放大提供坚实的基础。

板式精馏塔在现代化工行业中占有重要地位，塔板上气相偏流的形成是造成工业塔设备效率显著降低的重要因素之一。为了验证项目申请者所提的气相偏流形成机制假说，本项目分别从实验和计算流体力学角度对塔板上汽-液流动规律及水力学特征进行研究，并通过建立相关模型对气相偏流的形成机制进行论证，在此过程中涉及的研究内容及重要成果如下：（1）在1500×600 mm矩形冷模F1型浮阀塔板上，考察气、液流量对塔板上气液流动状态的影响，测量在不同气液流动状态下的压降、泄漏速率、液面落差、清液层高度、鼓泡区分率等流体力学参数。基于这些实验数据得到了形成气相偏流的判断依据。同时开发出了计算精度良好的漏液速率模型、塔板压降模型、清液层高度分布模型等塔板水力学模型，为大型塔设备下限操作负荷的确定提供了基础；（2）本项目从第一原理角度建立了多尺度能量方程，来解析浮阀塔板上汽-液流动结构的形成原理。提出了描述塔板上涵盖液滴、气泡等小尺度以及鼓泡区、泡沫区及喷射区等大尺度系统的能量方程，并使用遗传算法，并通过给定约束条件（物料守恒约束、汽-液流型条件约束等）对浮阀塔板的多尺度能量模型进行了求解，求解的结果得到了实验数据的验证，证明了气相偏流的形成确实受系统能量控制这一假设；（3）使用本项目开发的新曳力系数模型，以欧拉-欧拉双流体模型为基础，建立了三维精馏塔板气液两相流场的CFD模拟模型。进一步地，将CFD模拟模型与本项目提出的气相偏流模型耦合对实验塔板进行了全工况的模拟，模拟结果成功预测了气相在塔板上的不均匀分布，所得到的流体力学数据与实验数据吻合较好，证明了气相偏流模型耦合CFD模拟预测塔板上的汽-液两相真实流动的结构可行性。这些研究对于工业塔上气相偏流的预测和调控提供了理论指导。