Distillation Control Structure Selection for Energy‐Efficient Operations

Abstract

Few studies have been reported concerning the energy efficiency of various distillation column control structures. The choice of an energy-efficient control configuration by incorporating thermodynamics second law in the selection criteria is described. In addition to a relative gain array for assessing control loop interactions, a relative exergy array is used in evaluating the energy efficiency of various control structures. The preferred control structure should have both good operability and good energy efficiency as distillation columns are the major energy consumer in the chemical industry. The performance of the control structures in the dynamic mode is analyzed in detail. The proposed method is demonstrated on two binary distillation columns: methanol-water separation and benzene-toluene separation. Dynamic simulation results prove the efficiency of the proposed distillation control structure selection method.

Controllability Analysis of Distillation Sequences for the Separation of Bio‐Jet Fuel and Green Diesel Fractions

“…This structure considers the reflux flow rate L and the vapor boil‐up rate V as control variables in the distillate and bottoms output compositions 31. Other pairings between variables can be obtained through the relative gain array (RGA), the relative exergy array (REA), and other methodologies 32. Although, in practice, it is more common to use temperature controllers, the use of composition control structures is useful for comparative studies, and they have been widely used in previous works to detect the thermally coupled distillation system with the best closed‐loop dynamic responses for both set point tracking and load rejection 10, 15, 33.…”

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

“…Also, it is important to mention that other pairings in the control loops can be considered; e.g., in the work of Mathew et al 20, regarding the control of an ideal endothermic reactive distillation column with and without heat integration, the composition of the distillate was controlled by manipulating the reflux rate and the bottom's composition was controlled by adjusting a tray temperature in the stripping section. The selection of the pairings in the control loops can be done by using the relative gain array, or this selection can be carried out in terms of exergy analysis 21. The last option obtains an energy‐efficient control structure by incorporating second law efficiency.…”

Control of Quaternary Ideal Endothermic Reactive Distillation with and without Internal Heat Integration

“…The design of efficient and easily implementable control structures for such energy-efficient distillation systems is significant for the effective realization of heat energy savings [44]. However, very few articles explored temperature inferential control of such processes [35,37,38,[45][46][47]. In this contribution, temperature-based inferential control with cascaded distillate and bottoms product purity control is evaluated for the basic and internally heat-integrated RD column designs for the generic, ideal, endothermic, twofeed, two-product RD system.…”