Optimizing Control of LIquid-Liquid Extraction Columns

液-液萃取是一个重要的分离过程，也是最近出现的技术的关键步骤，如有色金属的湿法冶金生产、用于金属回收和消除危险废物的稀释废物流处理、核燃料循环中铀和钚的精炼和后处理以及核废料管理。生化分离。它在石油工业的加氢脱硫等传统分离中起着重要作用。工业规模的液液萃取设备包括塔式接触器和连续流搅拌槽。缺乏柱接触器的测量技术，这是该工艺控制研究数量有限的原因之一。在PI实验室的非侵入性超声技术的发展提供了一个新的机会，主动控制提取过程。此外，锡拉丘兹大学开发的原位微型相分离装置可以与浓度测量探头（如光纤、电导率、折射探头等）结合使用，并为多变量控制和在线优化提供了新的可能性。这项工作是利用上述技术在最佳条件下对提取器进行安全、多变量控制的一次尝试。此外，这些技术是第二个目标的推动力，即开发一种多变量非线性预测控制算法以实现最优操作。对液-液萃取柱的优化控制策略进行了规划，其目标是(i)控制萃取器内的分散相含率，（ii）确保在泛流或相转化方面的安全操作，以及（iii）控制溶质浓度以提供最佳萃取效率。该过程将通过(i)具有死时间的一阶传递函数的线性模型和（ii）包括液滴破裂和聚并相互作用的种群平衡方程的非线性模型来建模。这两个模型将按以下顺序应用于过程控制：-使用线性模型对分散相持率进行自适应增益调度控制，目的是展示超声波技术在提取过程控制中的应用。-通过应用人口平衡方程对无传质的分散相持率进行非线性预测控制，以证明物理模型的有效性。-传质过程中分散相保持率的非线性预测控制。-利用扩展公式中的人口平衡方程，包括传质和浓度，对含率和浓度进行多变量非线性预测控制。

Liquid-liquid extraction is an important separation process and a key step in recently emerging technologies such as hydrometallurgical production of non-ferrous metals, treatment of dilute waste streams for metal recovery and hazardous waste elimination, refining and reprocessing uranium and plutonium in the nuclear fuel cycle and nuclear waste management, and biochemical separations. It all plays a major role in traditional separation such as hydrodesulfurization in the petroleum industry. Industrial scale equipment for liquid-liquid extraction include column contactors and continuous flow stirred tanks. There is a lack of measuring techniques for column contactors which has been one of the reasons for the limited number of control studies for this process. The development of a noninvasive ultrasonic technique in the PI's laboratory provides the opportunity of a new initiative in the control of the extraction process. Also, in situ miniature phase-separation devices developed at Syracuse University can be used in combination with concentration measuring probes (e.g., fiber optic, conductivity, refraction probes, etc.) and introduce a new possibility for multivariable control and on-line optimization. This work is an attempt to utilize the above techniques for a safe, multivariable control of the extractors at optimal conditions. Further, these techniques are the impetus for the second objective, to develop a multivariable non-linear predictive control algorithm for optimal operation. An optimizing control strategy for liquid-liquid extraction columns is planned with the objectives of (i) controlling the dispersed phase holdup inside the extractor, (ii) ensuring safe operation with respect to flooding or phase inversion, and (iii) controlling the solute concentration to provide optimum extraction efficiency. The process will be modelled by (i) linear models of first order transfer functions with dead time, and (ii) nonlinear models of population balance equations which include droplet interactions of breakage and coalescence. Both models will be applied for the control of the process in the following sequence: - Adaptive gain-scheduling control of the dispersed phase holdup by using linear models, with the objective of showing the application of the ultrasonic technique in the control of the extraction process. - Nonlinear predictive control of the dispersed phase holdup without mass transfer by applying the population balance equations, to demonstrate the usefulness of physical models. - Nonlinear predictive control of the dispersed phase holdup during mass transfer. - Multivariable nonlinear predictive control of holdup and concentration using the population balance equations in an extended formulation to include mass transfer and concentrations.