Process efficiency plays a crucial role when the performance of different tech­nological configurations are to be considered. To reach this improved efficiency, several conventional approaches may be used, which make possible to a certain degree the intensification of processes, a necessary condition for the design of technologies with enhanced performance. But for attaining a higher degree of process intensification, the application of new concepts within the framework of a new paradigm is required—a product and process engineering paradigm, according to Stankiewicz and Moulijn (2002). These authors define process intensification as the development of new equipment and procedures leading to a “dramatic improvement” in chemical processes through the reduction of the ratio between the equipment size and the production capacity, energy consump­tion, and waste production, resulting in cheaper and sustainable technologies, i. e., any chemical engineering development leading to a significantly smaller, cleaner, and more energy-efficient technology. Process intensification can be carried out by using new types of equipment and unconventional processing methods, such as integrated processes and processes using alternative energy sources such as light, ultrasound, and the like. It also can be done by implementing new process control methods, such as intentional unsteady-state operation. In this way, pro­cess intensification can be considered as a major headway toward the design of essentially more efficient technologies with much better performance comparing them to processes based on individual unit operations preferentially connected in a sequential mode (Cardona et al., 2008).

One of the main ideas of process intensification is to combine different process functions (separation, mixing, chemical reaction, biological transformation, fluids transport; Li and Kraslawski, 2004) and to utilize the energy flows of the same process in order to achieve better process performance. The combination of func­tions implies the physical combination of unit operation and processes through their simultaneous accomplishment in the same single unit or by their coupling (conjugation). Similarly, the combined utilization of energy flows allows a better exploitation of available energy sources. This physical combination of material and energy flows leads to the integration of processes oriented to their intensifi­cation. In this way, the possibilities of improving the performance of the overall process in terms of saving energy and reducing capital costs are greater when the integration of several operations into one single unit is carried out (Cardona et al., 2008).

Process integration offers many advantages in comparison to nonintegrated processes. Particularly in the case of reaction-reaction and reaction-separation processes, integration allows increasing the conversion of reactants and, conse­quently, the volumetric productivity. This increased conversion is explained by the fact that some key components formed during the chemical or biochemical transformation are removed from the reaction zone leading to the acceleration of the direct reaction in reversible reactions, or to the reduction of the inhibition effects in the case of some biological processes (Cardona et al., 2008). For inte­grated processes, the increased conversion makes possible a better utilization of the feedstocks, and the increased selectivity allows the reduction in the amount of nondesired products, which implies the reduction of the waste streams. In this way, the process integration approach contributes to the design of environmen­tally friendly technologies. From the viewpoint of production costs, the integra­tion allows the development of more compact processes due to the reduction in the amount and size of processing units. Therefore, capital costs may be reduced as well as energy consumption. The reduction of energy costs is related to the decrease in the size of processing units. Smaller units have lower steam and cool­ing water requirements. Moreover, the integration approach allows achieving a synergetic effect in the heat transfer leading to the reduction of energy consump­tion. The reduction of the energy needs leads to the decrease in the size of the heat exchangers, which contributes to the compactness of the technological configura­tion, one of the most important features of integrated processes. Furthermore, the compactness of some integrated schemes allows the reduction in the amount of external recycling streams, which are substituted by internal recycles.

However, integrated processes exhibit some disadvantages when compared to nonintegrated processes. First of all, the controllability of integrated processes is much more complex. Often, the integration leads to the existence of multiple steady-states in the system. For this reason, integrated processes require robust control loops, which are expensive and difficult to design. In addition, the use of third substances in some integrated schemes, such as extractive reaction where the addition of an extractive agent is necessary, indicates the need for using recov­ery units in order to decrease the operating costs of the process (Cardona et al., 2008). One of the most difficult issues during the design of integrated processes is related to the lack of appropriate models for describing this type of configura­tion. Most of the developed models correspond to short-cut methods where main phenomena taking place in the system are quite simplified. These methods are mostly based on equilibrium models. However, this kind of method has allowed the preliminary and conceptual design of many integrated processes as well as the assessment of the viability of their implementation.

In a previous work (Rivera and Cardona, 2004), the classification of integrated processes was provided. Such processes can be divided into two main classes depending on whether unit operation or unit process is being combined. The inte­grated process is homogenous when two or more unit operations or two or more reactions (unit processes) are combined and heterogeneous when the combination is carried out between one unit operation (physical process) and one chemical reaction. Each case can be accomplished through either simultaneous or conju­gated configuration. In the first case, the physical and/or chemical processes are simultaneously carried out in a single unit. In the second case, the processes are carried out in different apparatuses connecting them by fluxes or refluxes, i. e., by coupling two or more units (Cardona et al., 2008). In relation to the process steps that can be combined, integrated processes can be of the following types: reaction-reaction, reaction-separation, or separation-separation.

In this context, the design of technologies with improved performance accord­ing to technical, economic, and environmental criteria for producing fuel ethanol is required. The reduction of energy consumption along with the decrease in the capital costs through process integration offers promising opportunities for the improvement of the overall process for bioethanol production. Thus, this reduc­tion can contribute to the worldwide development of the biofuels industry with its inherent economic, social, and environmental benefits. The aim of this chapter is to study and recognize the vast possibilities of process integration during the con­ceptual design and development of high-performance technologies for production of fuel ethanol from different feedstocks.

Process integration, as a mean for process intensification, is a successful approach for designing improved technological configurations for fuel ethanol production in which energy consumption, production costs, and negative envi­ronmental impacts can be reduced. This fact is remarkably important taking into account that the main objective of using liquid biofuels, like bioethanol, is the progressive displacement of fossil fuels. This implies the sustainable exploitation of the huge biomass resources of our planet and the use of clean and renewable energy sources. Solutions provided by the process integration approach have to be proved at an industrial level in order to develop energy efficient, environmentally friendly, and even “politically correct” processes for fuel ethanol production. In fact, some technologies directly involving the principle of integration for bioetha­nol production have already been successfully implemented.