Thomas Bisgaard

Optimal operation and stabilising control of the concentric heat-integrated distillation column (HIDiC)

Abstract This paper presents the application of a systematic control configuration design procedure on the HIDiC with a reboiler. The application is illustrated through two case studies of industrial relevance, namely the separation of benzene/toluene and a multicomponent mixture of aromatic compounds. Results of static optimisations and dynamic simulations are presented based on a realistic column model, which accounts for dynamic pressure drops and liquid holdups, dynamic energy balances and more. Using a decentralised control scheme, good stabilising and economic performance are achieved by controlling both column section pressures and the temperature profile in one of the sections, while the economic variables are controlled by cascade control loops. Guidelines for the design of both the regulatory control layer and the supervisory control layer are provided.

Dynamic Effects of Diabatization in Distillation Columns

Abstract The dynamic effects of diabatization in distillation columns are investigated in simulation emphasizing the heat-integrated distillation column (HIDiC). A generic, dynamic, first-principle model has been formulated, which is flexible enough to describe various diabatic distillation configurations. Dynamic Relative Gain Array and Singular Value Analysis have been applied in a comparative study of a conventional distillation column and a HIDiC. The study showed increased input-output coupling due to diabatization. Feasible SISO control structures for the HIDiC were also found and control-loop feasibility was demonstrated.

Active disturbance rejection control of a heat integrated distillation column

Heat integrated distillation columns (HIDiC) can save around 50% of energy consumption compared to conventional distillation columns. To reach this amount of energy saving, the HIDiC should be properly controlled. The high thermally coupled nature of HIDiC leads to high loop interactions making HIDiC difficult to control. In order to improve control performance, inferential active disturbance rejection control (ADRC) for HIDiC is proposed in this paper. The proposed control scheme integrates ADRC strategy with inferential feedback control. Tray temperatures are used as secondary measurements to estimate the product compositions. Due to the strong collinearity in tray temperatures, principal component regression (PCR) is used to build the soft sensor from process operation data. The proposed technique is applied to a simulated HIDiC for separating Benzene-Toluene mixture. Simulation results demonstrate the effectiveness of the proposed approach.

A Modeling Framework for Conventional and Heat Integrated Distillation Columns

Abstract In this paper, a generic, modular model framework for describing fluid separation by distillation is presented. At present, the framework is able to describe a conventional distillation column and a heat-integrated distillation column, but due to a modular structure the database can be further extended by additional configurations. The framework provides the basis for fair comparison of both steady state and dynamic performance of the different column configurations for a given binary or multicomponent separation.