In the manufacturing processes of high value-added products in the pharmaceutical, fine chemical polymer and food industry, insufficient control might produce off-grade products. This can cause significant financial losses, or in the pharmaceutical industry, it can result in an unusable batch. In these industries, batch reactors are commonly used, the control of which is essentially a problem of temperature control. In the industry, an increasing number of heating-cooling systems utilising three different temperature levels can be found, which are advantageous from an economic point of view. However, it makes the control more complicated. This paper presents a split-range designing technique using the model of the controlled system with the aim to design a split-range algorithm more specific to the actual sys- tem. The algorithm described provides high control performance when using it with classical PID-based cascade temperature control of jacketed batch reactors; however, it can be used with or as part of other types of controllers, for ex- ample, model-based temperature controllers. The algorithm can be used in the case of systems where only two as well as where three temperature levels are used for temperature control. Besides the switching between the modes of opera- tion and calculating the value of the manipulated variable, one of the most important functions of the split-range algo- rithm is to keep the sign of the gain of the controlled system unchanged. However, with a more system-specific split-range solution, not only can the sign of the gain be kept unchanged, but the gain can also be constant or less de- pendent on the state of the system. Using this solution, the design of the PID controller becomes simpler and can be implemented in existing systems without serious changes
In the pharmaceutical, fine chemical, polymer and food industry, where high value-added products are manufactured, insufficient control might produce off-grade products. This can cause significant financial losses, or in the pharmaceutical industry, it can result in an unusable batch. In these industries, batch reactors are commonly used for the manufacturing of intermediate and final products. The control of these reactors is essentially a problem of temperature control. In the industry, an increasing number of heating−cooling systems utilizing three different temperature levels can be found. Although they are advantageous from an economic point of view, it makes the control more complicated. A pilot unit of such a system can be found in the authors' laboratory, which contains a monofluid thermoblock with three different temperature levels. It is a useful experimental facility to test control algorithms for industrial use. This paper describes a split-range algorithm that can be used as part of the jacket temperature controller in the case of a thermoblock containing three different temperature levels. The main problem from the control point of view is that the sign of the gain of the controlled object changes depending on the relation of the jacket and the actual feed temperature of the jacket recirculation loop. The main purpose of the split-range algorithm is to maintain the sign of the gain of the controlled object unchanged, thus avoiding control instability. This solution ensures that the controller utilizes all three temperature levels, especially the medium level with lower energy consumption. The algorithm was tested with simulation, and for the jacket temperature controller, a constrained PI controller was used. The parameters of the controller were identified by numerical optimization. The resulting jacket temperature controller extended with the split-range algorithm was validated on the pilot system. The same set-point profile was used for simulation and for the test measurement; this was designed to cover the entire temperature range of the system and to contain drastic changes, constant and ramped sections. Both in the case of simulation and the test measurement, good control performance was achieved; the controlled variable followed the set-point with small error both in the case of ramped and constant set-points.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.