OVERVIEW

The teaching 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 unit operations 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 consists of an oral discussion. The discussion will start with two questions, one concerning absorption and the other concerning distillation or liquid-liquid extraction. The discussion may then cover any of the topics explained in class. With regard to theoretical topics, students will be required to demonstrate a good knowledge of equations and related proofs. With regard to exercises, students will be required to be able to discuss the simplifying assumptions that allow the theoretical and graphical methods developed in class to be applied to a specific practical problem.

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.

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

Students with disabilities or specific learning disorders (SLD) are reminded that in order to request adjustments during exams, they must first upload their certification to the University website at servizionline.unige.it in the ‘Students’ section. The documentation will be verified by the University's Services for the Inclusion of Students with Disabilities and SLD, as indicated on the federated website at the link: SUSTAINABLE POLYMER AND PROCESS CHEMISTRY 11767 | Studenti con disabilità e/o DSA | UniGe | Università di Genova | Corsi di Studio UniGe.

Subsequently, well in advance (at least 10 days) of the exam date, it is requested to send an email to the lecturer responsible of the exam, copying in Professor Sergio Di Domizio (sergio.didomizio@unige.it), the Department’s disability liaison, and the above-mentioned University's Services. The email must specify:

• the name of the course

• the date of the exam

• the student's surname, first name and matriculation number

• the compensatory tools and dispensatory measures deemed functional and requested.

The Department’s disability liaison will confirm to the teacher that the applicant is entitled to request adjustments during the exam and that these adjustments must be agreed upon with the teacher. The teacher will respond by communicating whether it is possible to use the requested adjustments.

Requests must be sent at least 10 days before the exam date in order to allow the teacher to evaluate their content. In particular, if the students intend to use concept maps for the exam (which must be much more concise than the maps used for study), if the request is not sent within the specified time frame, there will not be enough time to make any changes.

For further information on requesting services and accommodations, please refer to the document: Linee guida per la richiesta di servizi, di strumenti compensativi e/o di misure dispensative e di ausili specifici

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

Ask the professor for other information not included in the teaching schedule.