OVERVIEW

The course covers at an advanced level the unit operations dedicated to the main separation processes in the chemical industry: absorption, distillation and liquid-liquid extraction. In each case, after preliminary recollections of thermodynamics, the theoretical approach is developed. The theoretical part is supported by practical exercises (design and verification), carried out either through analytical or graphical methods, or on the computer with the aid of one of the most modern specific software packages (UniSim).

AIMS AND CONTENT

LEARNING OUTCOMES

The module aims to provide advanced theoretical tools for the design of the separation unit operations of a process industry plant, from theoretical development to field implementation. The advanced criteria for selection, design and operation of some typical separation columns will also be addressed.

AIMS AND LEARNING OUTCOMES

The objective of this teaching is to provide students with the knowledge and tools for analysing the elementary phenomena governing the unit operations of the chemical process industry dedicated to separation processes.

At the end of the course, students will be able to:

• formulate conceptual models that describe the phenomenology of chemical-physical processes of interest;
• formulate continuity equations (mass and energy) in distributed parameter systems;
• manage the scale-up process from laboratory scale to industrial scale;
• formulate design equations for the preliminary sizing of equipment used in physical separations;
• select the most appropriate unit operations for the specific application;
• acquire the ability to express themselves with appropriate technical terminology.

TEACHING METHODS

The course is delivered through lectures for a total of 40 hours (equivalent to 5 CFU). 

The supporting teaching material for exam preparation will be made available on the AulaWeb instance dedicated to the course.

SYLLABUS/CONTENT

• The module deals with the columns for separation processes, i.e.e absorption, distillation and liquid-liquid extraction. In each case, after some preliminary references to thermodynamics, the equations are developed and the semi-graphical methods that constitute the conceptual basis of modern numerical calculation methods are illustrated.

  Absorption.

  Introduction: Overview of the chemical-physical principles. Simple absorption. Stripping.

  Study of local and global exchange coefficients: The absorption mechanism: the double film theory (Whitman) and the more recent theories (Higbie, Dankwertz). The double film theory: derivation from the theory of diffusion through a stagnant film. Correlations between local and global trasfer coefficients. Regimes: Gas Film Limiting, Liquid Film Limiting and Mixed.

  Absorption equipment: Comparison between packed and plate columns. Packed columns: general characteristics. The various types of packings.

  Fluid dynamic effects in packed columns: pressure losses in packed columns. Loading, Flooding and Minimum Wetting Rate.

  Thermal effects in absorption columns: methods for evaluating temperature profiles in packed and plate columns. Typical temperature profiles. Consequences of thermal increases on the minimum (L / G) ratio, and on the performance of the column. Cooling systems.

  Packed absorption columns: Calculation of the height of the column in the case of an isothermal column. Number of exchange units and height of exchange unit. Calculation of the minimum L / G ratio. Considerations on the evaluation of the minimum L / G in non-isothermal packed columns.

  Plate absorption columns: Characteristics of the plates used for absorption columns: geometries and efficiencies. Calculation of the number of plates: graphical method based on the use of the operating line and the equilibrium curve. Graphical method based on the absorption factor.

  Absorption associated with chemical reaction: Regimes: slow reaction, intermediate regime, fast reaction, instantaneous reaction.

  Distillation

  Continuous distillation of binary mixtures: Thermodynamics. Definition of volatility and relative volatility. McCabe-Thiele method: minimum reflow ratio (demonstration of the Underwood equation) and maximum (infinite). Corresponding values ​​of the number of theoretical plates: maximum (infinite) and minimum (demonstration of the Fenske equation). Modifications necessary to apply the McCabe-Thiele method to the calculation of the number of theoretical plates in the case of columns with multiple feeds and side streams. Stripping and rectification columns.

  Batch distillation of binary mixtures: Case of operation at constant product composition: calculation of the required heat and total process time. Case of operation at constant reflux ratio R: calculation of the required heat and total process time.

  Continuous distillation of multi-component mixtures: Short-cut calculation methods: Erbar-Maddox method for the calculation of the number of plates. Fenske equation for the calculation of the minimum number of plates. Underwood method for the calculation of the minimum reflux ratio. Short-cut methods for the choice of the feeding plate. Rigorous calculation methods: the MESH equation system and the numerical methods of resolution.

  Distillation column design: types of plates. Efficiency. Choice of the diameter of the column. Column fluid dynamics: weeping, coning, entrainment and flooding regimes. Packed distillation columns.

  Liquid-liquid extraction

  Introduction: chemical-physical principles and thermodynamics.

  Calculation of the number of theoretical stages: Calculation of the number of theoretical stages in the case a) flows (raffinate / extract) in co-current and partially miscible solvents; b) flows in co-current and immiscible solvents.

   

  For each topic, the theoretical part is supported by practical exercises related to the calculation (design and verification) of the columns. The exercises are carried out either through analytical or graphical methods, or at the computer (in the computer lab) by using one of the most modern specific softwares (UniSim).

RECOMMENDED READING/BIBLIOGRAPHY

All the slides projected during the lessons are available in aul@web. The books listed below are suggested as supporting texts:

Textbooks

J.F. Coulson, J.H. Harker, Chemical Engineering, Vol. 2, Fifth Edition, Elsevier Science (2002).  

R. Sinnott & G. Towler, Chemical Engineering Design, Fifth edition, Elsevier Science (2009).

R.E. Treybal, Mass-Transfer Operations, 3-rd edition, McGraw-Hill Book Co., 1980 (International Edition, softcover) (alternativo al McCabe)

W.L. McCabe, J.C. Smith, and P. Harriot, Unit Operations of Chemical Engineering, 7th edition, McGraw-Hill (2005).

Reference text:

R.B. Bird, W.E. Stewart, and E.N. Lightfoot, Transport Phenomena, 2nd edition, John Wiley (2007)

Additional materials for working students or students with specific learning disabilities is available upon request.

Note: the copies of the lecture slides are not sufficient for a good preparation for the exam; it is strongly recommended to use the textbooks and reference books.

TEACHERS AND EXAM BOARD

LESSONS

LESSONS START

This course is held on the first semester. Lesson starting is managed according to the Manifesto (avaialble at https://corsi.unige.it/corsi/11767/). The class schedule is available at https://easyacademy.unige.it/portalestudenti

Class schedule

The timetable for this course is available here: Portale EasyAcademy

EXAMS

EXAM DESCRIPTION

The exam is oral: the teacher asks questions, typical of an oral exam. Additional information:

• the dates are available on-line;
• online registration is mandatory and must be done from the webpage: https://servizionline.unige.it/studenti/esami/prenotazione; 
• the classroom chosen for the exam and the start time will be communicated by e-mail sent via aul@web.

The grade obtained in the teaching will be the average of the marks given in the two modules in which the teaching is divided.

For students with disabilities or DSA, please refer to the Further Information section.

Only in urgent cases can the exam be conducted online, in accordance with the regulations issued by the University.

ASSESSMENT METHODS

The exam will consist of an oral discussion. The exam will mainly focus on the topics covered during the lectures and will aim to assess not only if the student has reached an adequate level of knowledge, but also if she/he has acquired:

•      design skills using traditional graphic methods,
•      familiarity with the calculation methodologies implemented by modern simulation software,
•      ability to manage pre-existing columns.

The student will be asked to graphically represent the various types of columns accompanied by the main auxiliaries (eg: reboiler, condenser, etc.). The ability to describe separator columns and related processes in a clear way and with correct terminology will also be evaluated.

FURTHER INFORMATION

Students who have valid certification of physical or learning disabilities on file with the University and who wish to discuss possible accommodations or other circumstances regarding lectures, coursework and exams, should speak both with the instructor and with Professor Sergio Di Domizio (sergio.didomizio@unige.it), the Department’s disability liaison.