Operation of Dividing-Wall Columns. 1. A Simplified Temperature Difference Control Scheme

Abstract

A simplified temperature difference control (STDC) scheme, consisting of two temperature and two temperature difference control loops, is proposed for the operation of dividing-wall columns (DWCs). The two temperature control loops are located, respectively, in the rectifying and stripping sections of the main distillation column and work to maintain the top and bottom product qualities. The two temperature difference control loops are arranged, respectively, in each side of the dividing wall with their temperature measurements arranged above and below the locations for introducing feed to the prefractionator and for withdrawing the intermediate product from the main distillation column. These special arrangements serve to keep a certain degree of separation of the fed mixture in the prefractionator and the purity of the intermediate product, tightening product quality control and rendering the STDC scheme with high robustness to the changes in the thermodynamic properties of the ternary mixtures separated. Separation of three ideal ternary mixtures of hypothetical components, A, B, and C, with different ease of separation indexes (ESIs) is chosen as illustrative examples to evaluate the proposed STDC scheme and thorough comparison is conducted with the currently available temperature control (TC) and temperature difference control (TDC) schemes. It is found that the STDC scheme is much superior to the TC scheme irrespective of the great changes in the ESIs. Although with relatively lower instrumentation cost and smaller engineering effort, it can generally lead to performance comparable with the TDC scheme. Application of the STDC scheme to the DWC separating a ternary mixture of ethanol, propanol, and butanol is also attempted and similar outcomes are obtained. Since the STDC scheme behaves in good accordance with the working principle of the DWC, it should be viewed as a general and effective strategy for the operation of the DWC.

Design and control for a dividing‐wall column with a partial condenser for pretreating an industrial multi‐component reformed gasoline mixture

“…Although some general guidelines and rules for DWC control have been recommended, researchers are putting increasing efforts into the controllability and process dynamics’ understanding of DWCs . The simplest control structure is the three‐point control structure.…”

“…[12][13][14][15][33][34][35] Although some general guidelines and rules for DWC control have been recommended, [36] researchers are putting increasing efforts into the controllability and process dynamics' understanding of DWCs. [37][38] The simplest control structure is the threepoint control structure. It is simply an extension of the control of a conventional distillation column with a side stream.…”

State‐of‐the‐Art of Advanced Distillation Technologies in China

“…Research focus is mainly on kinetics, feasibility analysis, concept design, and dynamic control, which is reflected by a number of papers published in domestic and foreign journals about reactive distillation. Energy‐saving technologies such as dividing‐wall column (DWC) and internally heat integrated distillation column (HIDiC) have been developed to satisfy the requirements of energy saving 3, 4. At present, under the guidance of the scientific concept of development, sustainable economic development, especially industrial energy efficiency and emission reduction are placed in a more important position.…”

Conventional Proportional‐Integral Control of a Dividing‐Wall Distillation Column with Discrete Measurements

“…Recognizing that in practice these variables are not measured in‐line, some works propose control systems in which the temperatures of certain stages are regulated, which in turn regulates the composition of output streams around their nominal values 5, 6. Furthermore, to improve closeness inference schemes, relationships of composition with respect to tray temperatures have been proposed as well 7.…”