Development of Guidelines for Plantwide Control of Gas-Phase Industrial Processes, from Reactor−Separator−Recycle Results

Abstract

The reactor−separator−recycle (RSR) process, consisting of a reactor and a separator/distillation column with material recycle between them, simplifies and idealizes real chemical plants. It is an important test bed used in plantwide control (PWC) studies. Though it has been actively studied in the past 15 years, appropriate guidelines on control structure selection are lacking, and there has been no consensus on the best control system. Also, there is still a need to study RSR processes with real components in practical context (that is, with more complete flow sheets) using rigorous process simulators. Another important aspect that has not been considered is the significance and usefulness of the results from RSR studies for real complicated plants. The main aim of this paper is to study the applicability of the RSR results to designing a PWC structure for a complete plant with heat integration besides a recycle. Findings of gas-phase RSR studies are applied to the toluene hydrodealkylation, ammonia, and styrene processes. The performance of the alternative control structures is analyzed for each process. Based on a comprehensive analysis of the results, useful guidelines for PWC design for gas-phase processes are developed.

Integrated Framework Incorporating Optimization for Plant-Wide Control of Industrial Processes

“…When the fresh feed flow is the only available option as TPM, the resulting control scheme can be implemented in two ways: control of fresh feed or total feed (i.e., fresh feed plus recycle) by manipulating fresh feed control valve in either case. Based on the guidelines developed in Vasudevan and Rangaiah, 22 we recommend the latter strategy for gas-phase processes. Note that the TPM selection must be completed before identifying the economic PWC objectives in Level 4.…”

“…Appropriate locations can be selected for pressure control by simulation and careful analysis of the process flowsheet. The guidelines proposed in Vasudevan and Rangaiah 22 for pressure control in gas-phase processes can be used to arrive at the final selection.…”

“…The preferred location for control is at an earlier point in the process path, so that control action is taken before the effect of disturbances is propagated throughout the plant. 22 And, the preferred manipulator is the purge flow where the inert component is drawn off and its composition is large. 22 This recommendation has been carefully formulated based on the results of the detailed simulation studies 22 on the toluene HDA and ammonia plants.…”

“…22 And, the preferred manipulator is the purge flow where the inert component is drawn off and its composition is large. 22 This recommendation has been carefully formulated based on the results of the detailed simulation studies 22 on the toluene HDA and ammonia plants.…”

Continuous Monoisopropyl Amine Manufacturing: Sustainable Process Design and Plantwide Control

“…Even as the need for an integrated process design cycle is well recognized in the literature, reports that demonstrate it for a complete process are far and few. Most reports thus focus on either conceptual flow sheet synthesis − (e.g., conceptual design of distillation systems, purification of azeotropic mixture) or economic optimum design and control of a given flow sheet − but not both aspects together.…”