Inherently Safer Design and Optimization of Intensified Separation Processes for Furfural Production

Currently furfural production has been the subject of increased interest because it is a biobased chemical able to compete with fossil-based chemicals. Furfural is characterized by flammability, explosion, and toxicity properties. Improper handling and process design can lead to catastrophic accidents. Hence it is of most importance to use inherent safety concepts during the design stage. This work is the first to present several new downstream separation processes for furfural purification, which are designed using an optimization approach that simultaneously considers safety criteria in addition to the total annual cost and the eco-indicator 99. The proposed schemes include thermally coupled configuration, thermodynamic equivalent configuration, dividing-wall column, and a heat integrated configuration. These are compared with the traditional separation process of furfural known as the Quaker Oats Process. The results show that because of a large amount of water present in the feed, similar values are obtained for total annual cost and eco-indicator 99 in all cases. Moreover, the topology of the processes has an important role in the safety criteria. The thermodynamic equivalent configuration resulted as the safest alternative with a 40% reduction of the inherent risk with respect to the Quaker Oats Process, and thus it is the safest option to purify furfural

Ranking of rectification structures separating quaternary mixtures with exergy analysis

In this paper exergy analysis is applied to select the most efficient rectification structures for separation of quaternary hydrocarbon mixtures. The basis and usage of exergy analysis is shown, as well as the benefits of its application. Exergy loss and thermodynamic efficiency is calculated from basic equations of thermodynamics. The ranking, even based on exergy analysis, highly depends on the product purification prescription. Finally it is shown that heat integration of distillation columns is exergetically beneficial in a wide product purity range

Low-cost and Energy-efficient Solutions for Multicomponent Distillation

Distillation accounts for 90-95% of all the separations on a chemical plant, and for about 3% of the world energy consumption. Even modest improvements to the process of distillation can have tremendous impact on the chemical economy world over. The goal of a major part of this thesis is to use process intensification methods to present, thoroughly investigate and systematically synthesize new processes for multicomponent separations which can serve as attractive candidates for distillation technology of tomorrow

Design of operable reactive distillation columns.

Reactive distillation is an integrated process which considers simultaneous physical and chemical transformations. It is increasingly receiving attention both from industry and academia. Significant advances have been made in the area of modelling and simulation as well as the implementation of such units industrially. However, the area of control and optimisation of such units has not been explored thoroughly. The thesis presents a general framework for simulation and design, which can handle reactive and non-reactive systems. Various different aspects of the modelling and simulation of distillation have been described in order to understand the behaviour of the reactive distillation columns. In the framework both simulation modes, steady-state and dynamic, are considered and the process is described by equilibrium and non equilibrium-based models. In a rate-based (or non equilibrium) model, mass transfer rates between liquid and vapour phase are considered explicitly, based on the Maxwell-Stefan equations. Equilibrium is attained at the phase interface in the non-equilibrium model. A switching policy makes it possible to go from one model to the other, based on the knowledge gained, by following the Gibbs free energy as a function of time. Tray efficiency has also helped in determining the switch between the non-equilibrium and equilibrium models, and has been studied for various systems. The existence of multiple steady state has been verified through simulation with the hybrid model. Bifurcation diagrams also confirmed the existence of output multiplicity obtained in the simulations. Analysis of process controllability at the design stage has been shown to provide guidance for improving process operation. In the thesis controllability measures for the reactive systems studied are presented as a first step towards control structure selection. A method for obtaining the design of reactive separation columns at minimum total annualised cost (investment and operating costs) and which will be able to maintain stable operation in the presence of variability is also presented

Energy efficient control and optimisation techniques for distillation processes

PhD ThesisDistillation unit is one of the most energy intensive processes and is among the major CO2 emitter in the chemical and petrochemical industries. In the quest to reduce the energy consumption and hence the environmental implications of unutilised energy, there is a strong motivation for energy saving procedures for conventional columns. Several attempts have been made to redesign and heat integrate distillation column with the aim of reducing the energy consumption of the column. Most of these attempts often involve additional capital costs in implementing. Also a number of works on applying the second law of thermodynamics to distillation column are focused on quantifying the efficiency of the column. This research aims at developing techniques of increasing the energy efficiency of the distillation column with the application of second law using the tools of advanced control and optimisation. Rigorous model from the fundamental equations and data driven models using Artificial neural network (ANN) and numerical methods (PLS, PCR, MLR) of a number of distillation columns are developed. The data for the data driven models are generated from HYSYS simulation. This research presents techniques for selecting energy efficient control structure for distillation processes. Relative gain array (RGA) and relative exergy array (REA ) were used in the selection of appropriate distillation control structures. The viability of the selected control scheme in the steady state is further validated by the dynamic simulation in responses to various process disturbances and operating condition changes. The technique is demonstrated on two binary distillation systems. In addition, presented in this thesis is optimisation procedures based on second law analysis aimed at minimising the inefficiencies of the columns without compromising the qualities of the products. ANN and Bootstrap aggregated neural network (BANN) models of exergy efficiency were developed. BANN enhances model prediction accuracy and also provides model prediction confidence bounds. The objective of the optimisation is to maximise the exergy efficiency of the column. To improve the reliability of the optimisation strategy, a modified objective function incorporating model prediction confidence bounds was presented. Multiobjective optimisation was also explored. Product quality constraints introduce a measure of penalization on the optimisation result to give as close as possible to what obtains in reality. The optimisation strategies developed were applied to binary systems, multicomponents system, and crude distillation system. The crude distillation system was fully explored with emphasis on the preflash unit, atmospheric distillation system (ADU) and vacuum distillation system (VDU). This study shows that BANN models result in greater model accuracy and more robust models. The proposed ii techniques also significantly improve the second law efficiency of the system with an additional economic advantage. The method can aid in the operation and design of energy efficient column.Commonwealth scholarship commissio