Preface

Introducing students to the analysis and evaluation of chemical processes involves integrating knowledge from all the fields within Chemical Engineering, namely, fluid mechanics, heat and mass transfer, reactor design, unit operations, and process safety and control, and it also requires a basis in simulation. Lately biology and biotechnology have also stepped inside that box. While many Chemical Engineering curricula leave this task for the sole module of Process Design, at some universities there is a specific module dealing with evaluating how traditional processes in the chemical industry have been developed, the driving forces that have changed the way of producing major chemicals (eg, sulfuric acid), and the evaluation of the units involved. Despite the tight schedules of three- or four-year curriculums required for a bachelor’s degree in Chemical Engineering, history tells us that learning from mistakes and successes via case studies allows critical thinking and provides a strong background.

This book reflects the work of many years of teaching “Introduction to Chemical Processes and Technologies” at the University of Salamanca and as a visiting professor at University of Birmingham, University of Leeds, University of Maribor, Universidad de Concepción, and Carnegie Mellon University, as well as industrial experience in my position at P&G and as a consultant for biofuels companies. I have tried to select a few processes that use all the possible raw materials—air, water, biomass, minerals, and fossil fuels—to produce a number of basic chemicals, from oxygen, nitrogen, and hydrogen, to ammonia, methanol, nitric acid, sulfuric acid, soda ash, sodium chloride, bioethanol, penicillin, FT fuels, and biodiesel. Unlike many other references dealing with similar topics, this book is not merely descriptive, but uses chemical engineering principles to analyze the processes that transform the raw materials into products. Therefore, throughout the text one can find distillation column analysis (ie, air separation, ethanol and methanol purification), reactor designs (eg, ammonia converter, SO₂ converter, sugar fermentation, biodiesel production, ammonia and methanol synthesis), absorption columns (eg, ammonia purification, CO₂ capture, sulfuric acid production), membrane analyses (eg, desalination), electrolysis (eg, water and NaCl), adsorption processes (eg, air desiccation, PSA), evaporator and crystallizer designs, power cycles, and complete process analyses (eg, air liquefaction; nitric acid, sulfuric acid, hydrogen, methanol, ammonia, and sodium carbonate production).

The organization of the book is as follows. Chapter 1, The chemical industry presents an introduction to the evolution of human needs and its effect on chemical products and processes. Chapter 2, Chemical processes presents the basics in process development and analysis. It covers the principles of process synthesis, focusing on the heuristic approach, and presents flowsheeting, the role of security and environmental issues in process design decision-making, as well as a brief summary of the chemical engineering principles that will be used throughout the rest of the book. Chapter 3, Air starts with the first raw material. I selected air because of its abundance and life-supporting function. Air is used to obtain its components, and that process is analyzed from liquefaction to final separation. Air humidity is also evaluated. Chapter 4, Water showcases water as a raw material. Apart from presenting current concerns regarding its consumption and usage, the chapter is devoted to evaluating the use of salt water to produce freshwater, and to the use of salt in the production of major chemicals. Chapter 5, Syngas presents the use of carbon-based material for the production of syngas, evaluating all the steps, including purification. The gas is later used in the production of ammonia, methanol, and synthetic fuels. Chapter 6, Nitric acid and Chapter 7, Sulfuric acid cover the use of minerals and/or gases to evaluate two important chemicals of the inorganic industry. Chapter 6, Nitric acid is devoted to nitric acid production. It is the first complete case study, analyzing all the units from ammonia to the concentration of nitric acid. Chapter 7, Sulfuric acid studies the production of sulfuric acid. The two main methods are evaluated: lead chambers and the contact process. Finally, Chapter 8, Biomass discusses the use of biomass. This chapter is linked to Chapter 5, Syngas since biomass is a particularly carbon-rich raw material. However, current attention and efforts towards a more sustainable industry are not forgotten, as well as polymerization kinetics for synthetic rubber production as an attempt to produce materials that match the natural ones. Typical biofuels, specialty chemicals such as penicillin, and synthetic rubber are evaluated. I acknowledge that other chapters could have been added, but as the reader can see, the topics selected cover a wide range of raw materials and units.

Nowadays there is an unwritten rule that the use of software must accompany any module of an engineering degree. Thus, some of the problems presented require the use of software; therefore I have used EXCEL, GAMS, MATLAB®, and gPROMS, or process simulators like CHEMCAD, to provide solutions. I thank all the software companies for their input. The text does not aim to teach the use of any one of these specific packages—there are other books better-suited to that aim—but rather how to use software in general to solve the particular problems presented throughout the book. Furthermore, other software exists that can be used to solve the same problems.

This work would not have been possible without previous professors on the subject who decided not just to focus on process description, but also to perform a systematic analysis of the processes based on the principles of chemical engineering. In addition, it was crucial to use the constructive criticism of my students, who at some point asked me, How can we study this module? (Edgar Martín, December 2014) Where can we find problems to practice? To all of them, my sincere gratitude. In particular, special thanks go to those who reviewed the manuscript: previous MSc students at the University of Salamanca such as Alberto Almena, Verónica de la Cruz, Borja Hernández, José Antonio Luceño, Santiango Malmierca and Antonio Sánchez; and prof. I.E. Grossmann from Carnegie Mellon University. I would like to thank the software companies who provided their support, and the chemical companies who granted permission to present real flowsheets and unit schemes, which are of high value to students.

A note to instructors: This book can be used in two ways. For those who teach a module on processing raw materials into products, it provides a description of a number of processes with examples for classroom seminars and end-of-chapter problems for students to evaluate their understanding of the material. Most of the problems have been exam questions over a number of years at the University of Salamanca. An appendix with the solutions is provided at the back of the book. For those professors whose programs do not have such a module, the book can be used as reference for subjects such as chemical engineering principles, reactor engineering, and unit operations, and can also provide information and case studies for putting together an open problem of process design for a classical process design class at the senior level. Furthermore, examples and problems for the use of process simulators, as well as the use of other software packages, are presented and provided.

A note to students: This book provides not only the description of the processes and the physico–chemical principles of operation, but also a considerable number of detailed examples throughout the text, including computer code for solving some of them. There is a larger collection of problems at the end of each chapter to challenge your understanding of the material in the chapters, and for you to practice and get better insight into the processes covered. You can find the results of the problems at the back of the book for guidance.

February 2016