Comparative Analysis of Different Control Strategies for a Train of Cryogenic ¹³C Separation Columns

Abstract

Carbon isotopes are widely used in numerous industries, especially in medicine. The advantage of using 13C‐labeled products is only shadowed by the difficulty of increasing the natural concentration. One method available is a train of cryogenic distillation columns. This paper presents a preliminary analysis of three different control strategies for a unit comprising three 7‐m‐high isotope separation columns: a decentralized multivariable proportional‐integral controller and two decoupling control algorithms. For the first one, a single controller is designed for the entire distillation column train, whereas for the second decoupling approach, three separate controllers are designed for each of the three columns. Simulation results show that the last approach provides significantly improved results when compared to the other two control strategies.

Autotuning method for a fractional order controller for a multivariable 13C isotope separation column

“…The process is characterized by large time constants and large time delays. The process and equipment have been previously described in [14], [15], [16]. Simple experiments on the column have led to a steady state gain matrix and the associated RGA number: The RGA result in (24) suggests that a diagonal pairing y mu m , with m=1,2,3, diminishes the interactions.…”

Robust Fractional Order Controllers for Distributed Systems

“…where the discrete-time gain K d is computed based on the equivalency of the continuous-time and discrete-time transfer functions from (13) and (17) in steady state (s=0 and z=1):…”

“…The actual equipment, as well as a schematic representation, are given in Figures 1 and 2. A great deal of papers have been published previously by the Authors describing the characteristics and operation of a single column or the cascade, the model of such a plant, as well as several control strategies [15][16][17][18][19][20][21].…”

“…Three boilers, installed at the bottom of each column, ensure a gaseous upstream, while the liquid downstream is produced by condensing these vapors on the cold walls of the condenser. The system operates at approximately -190 o C, in order for both liquid and gaseous phases of (CO) to co-exist [16,17,22]. Several sensors and actuators, as pictured in Figure 3, are installed for monitoring and control purposes, such as: seven flow transducers, three pressure transducers at the top of the columns, three differential pressure transducers, three thermocouples for boiler temperature measurements, three dedicated liquid carbon monoxide level transducers in the bottom of the columns, three pumps to ensure the flow between the columns, as well as, a dedicated transducer for the liquid nitrogen level in condenser [23].…”

A Portable Implementation on Industrial Devices of a Predictive Controller Using Graphical Programming

“…The efficiency of the isotope-separation process, occurring at very low temperatures, is strongly dependent upon a strict operation of these vacuum pumps. These need to be carefully controlled since a failure of the vacuum leads to the compromise of the entire separation process [9]. The efficiency of the proposed solution was highlighted by comparing it to several different implementations, a PC-based control system, one implemented on a real-time target, and one on an advanced RISC machine (ARM) microcontroller, all of them running the controller.…”