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2372 results in Chemical engineering

Page 28 of 119

  • 3 - Countercurrrent Separation Processes

  • David Pfister, Lucrèce Nicoud, Massachusetts Institute of Technology, Massimo Morbidelli, Eidgenössische Technische Hochschule Zürich
  • Book:
    Continuous Biopharmaceutical Processes
    Published online:
    22 September 2018
    Print publication:
    11 October 2018, pp 84-109

  • Summary

    This chapter provides basic concepts about multi-column counter-current chromatography. The benefit of counter-current contact in separation processes is demonstrated considering cascades of equilibrium stages. Based on this, the true moving bed (TMB) process and the simulated moving bed (SMB) process are introduced. Then, the design space of the TMB and SMB processes leading to a complete separation is identified, starting with simplistic systems and progressively introducing more complex effects, namely non-linear adsorption isotherms and mass transfer limitations. Finally, two process design approaches for multi-column chromatographic processes are presented: an empirical one, which allows to obtain a first guess of the operating conditions from a single-column experiment, and a model-based one, which allows a more rigorous determination of the process variables.

  • 5 - Countercurrent Chromatography for the Polishing Steps

  • David Pfister, Lucrèce Nicoud, Massachusetts Institute of Technology, Massimo Morbidelli, Eidgenössische Technische Hochschule Zürich
  • Book:
    Continuous Biopharmaceutical Processes
    Published online:
    22 September 2018
    Print publication:
    11 October 2018, pp 153-202

  • Summary

    This chapter focusses on the polishing steps encountered during protein purification by chromatography. The first part provides a detailed description of the mechanistic phenomena at stake, whose complexity may greatly vary from one case to the other depending on the number and type of impurities, the selectivity for the target protein as well as non-linear and competitive effects. Several multi-column counter-current processes allowing the implementation of the polishing steps in a continuous manner are presented in the second part of the chapter. Modifications of the classical SMB process introduced to better cope with the specific needs of the biopharmaceutical industry are discussed. These modifications primarily aim at recovering more than two fractions and at implementing modifier concentration gradients. Two process design approaches for multi-column processes are presented: an empirical one, which provides a first guess of the operating conditions from single-column experiments, and a model-based one, which allows a more rigorous determination of the process variables. The model-based approach is used to compare the performance of multi-column and single-column processes.

  • 6 - Protein Conjugation

  • David Pfister, Lucrèce Nicoud, Massachusetts Institute of Technology, Massimo Morbidelli, Eidgenössische Technische Hochschule Zürich
  • Book:
    Continuous Biopharmaceutical Processes
    Published online:
    22 September 2018
    Print publication:
    11 October 2018, pp 203-246

  • Summary

    This chapter deals with protein bioconjugation, which has emerged as an attractive technique to enhance therapeutic properties of protein-based drugs (e.g. in-vivo circulation, potency). The first part of this chapter aims at answering questions regarding the coupling chemistry and the modelling of the kinetics of bioconjugation. Then, the purification of conjugated proteins is addressed. In particular, chromatography is presented as a technique to purify conjugated proteins according to their extent of conjugation on the one hand and to the position of the conjugated groups on the other hand. Moreover, continuous technologies for both the conjugation reaction and the purification by chromatography are discussed. Finally, the potential benefits from the integration between the reaction and the purification steps in bioconjugation processes are examined. This chapter combines theoretical aspects, model simulations and experimental results from practical examples, for instance dealing with PEGylated proteins and antibody-drug conjugates.

Cybernetic Modeling for Bioreaction Engineering
  • Doraiswami Ramkrishna, Hyun-Seob Song
  • Published online:
    29 September 2018
    Print publication:
    18 October 2018
  • Uniquely focusing on dynamic modeling, this volume incorporates metabolic regulation as a survival mechanism for cells, by driving metabolism through optimal investment of its resources for control of enzyme synthesis and activity. Consequently, the models have a proven record of describing various uptake patterns of mixed carbon substrates that have become significant in modern applications of biomass for the production of bioenergy. The models accurately describe dynamic behavior of microbes in nutrient environments with mixtures of complementary substrates, such as carbon and nitrogen. Modeling of large metabolic networks (including prospects for extension to genome scale) is enabled by lumped hybrid cybernetic models with an unparalleled capacity to predict dynamic behavior of knockout strains. This is an invaluable, must-have reference for bio-researchers and practicing engineers.

Continuous Biopharmaceutical Processes
  • Chromatography, Bioconjugation, and Protein Stability
  • David Pfister, Lucrèce Nicoud, Massimo Morbidelli
  • Published online:
    22 September 2018
    Print publication:
    11 October 2018
  • This innovative reference provides a coherent and critical view on the potential benefits of a transition from batch to continuous processes in the biopharmaceutical industry, with the main focus on chromatography. It also covers the key topics of protein stability and protein conjugation, addressing the chemical reaction and purification aspects together with their integration. This book offers a fine balance between theoretical modelling and illustrative case studies, between fundamental concepts and applied examples from the academic and industrial literature. Scientists interested in the design of biopharmaceutical processes will find useful practical methodologies, in particular for single-column and multi-column chromatographic processes.

  • 2 - Energy

  • William C. Reynolds, Piero Colonna, Technische Universiteit Delft, The Netherlands
  • Book:
    Thermodynamics
    Published online:
    15 June 2019
    Print publication:
    20 September 2018, pp 16-31

  • Summary

    In the first chapter we reviewed the concept of energy as it arises in mechanical systems. We interpreted work as a transfer of energy and used this idea to develop expressions for kinetic and potential energy. These were special instances of the general concept of energy, which is perhaps the most fundamental concept in all of science. In thermodynamics, another relevant mode of energy transfer is heat. Once all these concepts are clear, they can be used together with the first law to analyze and design an infinite variety of systems and devices, which are at the foundation of current and future societies.

    Concept of Energy

    The Energy Hypothesis

    The ideas inherent in the general concept of energy are encapsulated in what we call the Energy Hypothesis:

    Matter can be treated as having a property, called energy, that is an extensive, conserved scalar measuring its ability to cause change; work is a transfer of energy.

    The terms used above are very important:

  • • extensive means that the energy of a system is the sum of the energies of its parts;

  • • conserved means that the total amount of energy in an isolated system does not change;

  • • scalar means that energy is a quantity without directional (vector) character;

  • • work is a transfer of energy; it provides the key to the quantitative evaluation of the energy contained by matter.

    • In Section 1.4 we used these ideas to obtain expressions for the kinetic and potential energy of matter. Other energy forms are evaluated in the same way. Since the energy hypothesis is itself used in the evaluation and measurement of the energy of matter, it is not possible to test the hypothesis of energy conservation by experimental measurements of energy. However, one can use the energy hypothesis to predict how matter will behave, and these predictions (when done correctly!) are always confirmed by experiment. Countless working devices, designed using energy analysis, provide enormous evidence of the validity and utility of the energy hypothesis. Believe in the concept of energy; it works!

    Microscopic Energy Modes

    A macroscopic quantity of matter contains a huge number of molecules, and its energy is the sum of the individual energies of all these molecules. Molecules and systems of molecules can have energy in a variety of different microscopic modes.

  • Remembering Bill Reynolds

  • William C. Reynolds, Piero Colonna, Technische Universiteit Delft, The Netherlands
  • Book:
    Thermodynamics
    Published online:
    15 June 2019
    Print publication:
    20 September 2018, pp xx-xx

  • Summary

    I started to work at this book in a very emotional situation, and those strong feelings accompanied me during the time I dedicated to its writing since then.

    Professor Bill Reynolds, whom I first met in 1994 as my mentor while pursuing a Masters degree at Stanford University, contacted me in June 2003 and told me of the new thermodynamics textbook he had started to write some time before. He mentioned that he had health problems. He then asked me if I wanted to visit him before the end of the year to talk about the book. I had been spending periods at Stanford working with him since I graduated there in 1995. As always, I enthusiastically accepted the invitation and arrived at Stanford in November of 2003. The moment I met Bill in his office I understood that something was not quite right.

    After a very short preamble, he told me “You remember our plan to work together on a new thermo book and to add your material on properties of mixtures, energy systems, and the rest? Well, I would like you to pick up from where I am leaving this book and finish it, as I am going to die soon of a brain tumor.” I was shocked and immensely sad, and at the same time I felt honored and committed. Those last days I spent with him were extremely intense and moving. We only managed to exchange ideas about the book very briefly, as his health was rapidly deteriorating.

    I will never forget the moment I parted from him. I was standing next to his bed in his home, holding his hand, with my eyes full of tears, in silence, while I was mentally thanking him for all he had done for my education. He was looking back at me, with tenderness. It was December 26th, 2003. Bill died on January 3rd, 2004.

    I had become involved with this book earlier, during my Masters studies at Stanford. I was taking ME270-Engineering Thermodynamics, taught by Bill.

    He was the most extraordinary lecturer, as anybody who has ever followed one of his classes can testify. Meanwhile, I was one of his research assistants, working on thermodynamic property models for multicomponent fluids.

  • 7 - Energy Conversion Systems

  • William C. Reynolds, Piero Colonna, Technische Universiteit Delft, The Netherlands
  • Book:
    Thermodynamics
    Published online:
    15 June 2019
    Print publication:
    20 September 2018, pp 144-193

  • Summary

    One of the most dazzling applications of thermodynamics is the study and design of devices to convert energy to obtain some useful effect. Modern societies are based on the extensive use of electricity, heating, and refrigeration for a broad variety of goals. These services are supplied by a system in which some sort of working substance, usually in the gas or liquid phase, flows through several devices at various temperatures. The same holds for engines, which provide the stunning mobility which is also a pillar of modern times.

    Here we therefore describe and analyze systems such as stationary power plants, propulsion engines, refrigerators, heat pumps, and the like. Stationary power plants convert one kind of energy, like the chemical energy of a fuel, the thermal energy of a geothermal reservoir, or solar radiation into electricity. Propulsion engines do the same, but usually the primary energy source is a liquid fuel and the final objective is to obtain mechanical power or thrust to put something into motion. Refrigeration systems and heat pumps make use of electrical, mechanical, or thermal power in order to keep the temperature of a certain space at a value different from that of the natural environment.

    Analysis of Thermodynamic Systems

    Most energy systems involve a working fluid, like water or air, which is circulated through one or more components, often arranged in a cycle. The working fluid undergoes therefore a sequence of processes, which together form a thermodynamic cycle. In steam power plants (Figure 7.1a) the cycle is usually closed, but thermodynamic cycles can be open (closed by the atmosphere), as is the case for a turboprop engine (Figure 7.1b).

    The basic methodology for the analysis of thermodynamic processes and systems has been laid down in Chapter 4, while in this chapter we will use that procedure, together with knowledge on the estimation of fluid properties (Chapter 6), in order to study some notable examples of energy conversion systems. In addition, we can make use of the many consequences of the second law of thermodynamics to discuss their performance and limitations.

    In Section 3.6 we have already stressed the importance of thermodynamic charts and of sketching relevant processes on such charts. Graphical representation of concepts is a very powerful tool for the understanding of thermodynamics.

  • 9 - Exergy Analysis

  • William C. Reynolds, Piero Colonna, Technische Universiteit Delft, The Netherlands
  • Book:
    Thermodynamics
    Published online:
    15 June 2019
    Print publication:
    20 September 2018, pp 233-256

  • Summary

    Application of the First and Second Laws of Thermodynamics, together with entropy analysis, has already showed us that a useful effect like work, cooling, or heating can be obtained if a thermodynamic system is not in equilibrium with its surroundings. The Carnot efficiency tells us which is the maximum amount of work (or power) that we can extract from a thermal source with a device operating between the temperature of the thermal source and a lower temperature. We also know that all the processes in a Carnot cycle are reversible, and this is an unattainable limit for real processes. Similar reasoning can be applied to refrigeration systems, whereby mechanical work is used to obtain the cooling effect. Entropy production always occurs in real processes and we generally speak of thermodynamic losses associated with entropy production.

    Now we look closer at this concept, which becomes a powerful analysis and optimization tool in energy conversion engineering.

    What for?

    We are about to define another thermodynamic function, called exergy. This function is useful to evaluate thermodynamic losses in quantitative terms and to answer questions like:

  • • Given a certain thermodynamic system, made of several components each realizing a certain set of processes of different nature (think for example of a Rankine cycle power plant, with heat exchangers performing heat transfer, turbines expanding vapor to obtain mechanical power, and pumps used to compress liquid water), which of the processes is most responsible for thermodynamic losses?

    • By using exergy analysis you can compare a heat exchanger with a turbine and decide which of the two components is more dissipative with respect to the desired energy conversion goal of the entire system. If you know which components account for more irreversibility within a system, thus depleting the efficiency of the entire process with respect to the ideal limit of the Carnot cycle, you can decide how to best invest resources to improve your system design.

  • • Given two thermodynamic processes or energy systems operating between different temperature levels, which one of the two performs best (has the best thermodynamic quality)?

Page 28 of 119