Agrawal分壁精馏塔中多相传递和多区流场调控研究

Agrawal divided-wall column has two staggered partition walls, which can realize two-level sloppy split and one-level split of four component mixtures successively, and has significant energy saving advantages. This proposal focuses on studying gas-liquid two-phase transfer process and flow field regulation of the staggered area of two partition walls in Agrawal divided-wall column. Based on transferred key parameters and interacted boundary, a multi-zone flow field regulation model will be constructed for the double-walled trays, and the complex multi-phase transfer process of gas-liquid two-phase flow, heat transfer and mass transfer in the double-walled trays will be analyzed. On this basis, the influence of operating conditions on the flow field of the staggered area of two partition walls and its regulation mechanisms will be explored experimentally and numerically in the dynamic change process. The qualitative and quantitative relationship between the critical manipulated variables, controlled variable and flow field distribution of the staggered area of two partition walls will be obtained, which could guide the acquisition of advanced dynamic control strategy. As a result, precise dynamic control of Agrawal divided-wall column will be achieved based on the multi-zone flow field regulation mechanism. The successful implementation of this proposal not only helps to realize the dynamic control of Agrawal divided-wall column, but also guides the design of advanced columns.

Agrawal分壁精馏塔具有上下两块相错分隔壁，塔内可依次实现四组分混合物的两级非清晰分割和一级清晰分割，具有显著节能优势。本项目拟以Agrawal分壁精馏塔为研究对象，开展双隔壁相错区域气-液两相传递过程和流场调控研究。通过关键参数传递和边界交互法，构建双隔壁塔板的多区流场调控模型，剖析双隔壁塔板气-液两相流体流动、传热和传质复杂的多相传递过程。在此基础上，从实验和模拟层次上探究动态变化过程中操作条件对双隔壁相错区域气-液流场的影响和调控机制，以此关联隔壁远近关键操作变量和控制变量与气-液两相流场分布的定性和定量关系，获取先进动态控制策略，实现基于多区流场调控的Agrawal分壁精馏塔精准动态控制。本项目的成功实施不仅有助于实现Agrawal分壁精馏塔的动态控制，也为先进塔器的设计提供理论指导。

ADWC具有上下两块相错分隔壁，塔内可依次实现四组分混合物的两级非清晰分割和一级清晰分割，具有显著节能优势。但ADWC内存在上下交错的双隔壁，塔内多区域的不同变量之间高度耦合，同时，ADWC塔内复杂的气-液多相流行为显著影响利于四组分混合物高纯度清晰分割的流场分布的形成和整塔分离效率。然而，双隔壁的引入，也使分壁精馏塔内流体流型结构的非均匀性、流域的多态性及流动的非线性等复杂多相流特性变得更为突出。本项目以ADWC为研究对象，首先对比了正序分离序列、预分馏分离序列和ADWC的严格精馏模型，以最小全年总费用（Total annual cost, TAC）为目标考察了不同分离序列的节能效果及不同结构参数的影响，获取了稳态分离特征，发现ADWC在节能方面优势明显，相较于传统正序分离序列，再沸器负荷和TAC分别减少40.6%和35.1%，与预分馏分离序列相比，再沸器负荷和TAC分别减少20.0%和29.0%；基于稳态分离特征及ADWC双隔壁相错区域塔板水力学计算结果，设计了一套以ADWC双隔壁相错区域筛板塔为主体的实验装置，并分析了塔板上气-液两相非均匀流体流动特性和多相传递过程，提出了包含壁面传热和传质的CFD多区流场调控模型。基于模型化研究，并在实验装置上进行热模流场实验获取宏观流场特征，结合理论模型和实验研究，明确了操作条件对ADWC双隔壁相错区域流场的调控规律，发现气液两相间的接触状态是影响传质效果的重要因素，不同气速下的界面面积浓度的分布都是先增大后减小；随着气相的上升，传质表面从原来的气锥表面变为了泡沫层中大量气泡的液膜表面，传质面积大大增加，液相中甲醇的浓度逐渐减少。基于此，对ADWC进行动态控制研究，提出了温度-组分混合控制回路动态控制策略，既能避免控制过程中产品纯度偏差值过大，又能提高系统应对扰动的能力，实现了ADWC进料条件下大幅度扰动下（±20%）的精准动态控制。