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CHEE 221Chemical Processes and Systems

Fall 2015

Instructor: Robin HutchinsonDupuis 426

robin.hutchinson@queensu.ca 

Example:  Production of LDPE by radical polymerization

• Low density polyethylene– ~20 billion kg/yr produced world‐wide– One reactor: ~ 5‐20 tonnes/hr– The oldest commercial polymer (late 1930’s)– High temperature (200‐300 C), high pressure (2000‐3000 atm)

– Ethylene monomer  Polymer• Catalyzed by free‐radical initiator, very exothermic reaction

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High Pressure Autoclave Reactor (500 L)a) Stirrer motorb) Stirrer shaftc) Bursting disk ports a

b

c c

Gas in

Product outCHEE 221 3

LDPE Reactor

LDPE Reactor and Chemical Engineering• Reaction engineering:

– Combine detailed model of reaction kineticsand mechanisms with reactor configuration,operating conditions and flows (CHEE 321)

– Polymer reaction engineering (my work) –control composition and architecture ofpolymer properties

• Mixing of feed stream (cold, no polymer) with reactor contents– Fluid flow (CHEE 223), Heat and mass transfer

(CHEE 330, CHEE 33x), Transport phenomena(CHEE 412, CHEE 452)

• Maintaining reactor at desired operating conditions– Process dynamics (CHEE 222), process control

(CHEE 319)

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LDPE Production: The rest of the process

http://processflowsheets.blogspot.ca/2011/08/low‐density‐polyethylene‐process‐flow.html

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LDPE Example: Process Flowsheet

• Complexity driven by need to purify product and recycle reactants (thermodynamics: CHEE 210 and CHEE 311)

• Process design dictated by economics and environmental considerations

• Can perform material and energy balances around:• each unit• entire system• Include raw materials production and final product disposal:  “Life Cycle Assessment”

• Conservation Equation for Mass and Energy:

Accumulation = In – Out + Generation ‐ Consumption

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• Chemical Engineering involves making stuff (reactions)and purifying stuff (separations), for example:

• Mining, pulp & paper, oil refining, polymers, food,…• Power generation (and removal of waste gases)• Your kidneys (lungs, heart, etc…)

• You need to:– Minimize production of unwanted byproducts– Separate the good (product) from the bad (byproducts)– Recover the unused reactants– Maximize profit, minimize energy consumption, minimize impact on the environment

CHEE 221

Motivation for CHEE 221

•No universally accepted definition of chemicalengineering exists. Today, many areas of the economyemploy those educated as a chemical engineer.Examples include:Traditional chemical engineering: mining, pulp & paper, oil refining, materials (rubber, plastics, etc.), environmental…

Non‐traditional chemical engineering: microelectronics (semiconductor manufacturing), biotechnology (pharmaceutical processes, genetic engineering, …)…

Other: medicine, law, business and finance

• Chemical engineers excel because they are trained inanalyzing flows (material, energy, $$$) involved in thetransformation of raw materials into desired products.

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More Motivation for CHEE 221

CHEE 221

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CHEE 221:  Chemical Processes and Systems

• CHEE 221 is an introductory course that prepares you toformulate and solve material and energy balances, focusing oncontinuous processes at steady‐state (i.e. no change withtime). It is the foundation for future courses in: thermodynamics (CHEE 210, CHEE 311) kinetics and reactor design (CHEE 321)  unit operations and transport phenomena (CHEE 412, CHEE 452) process dynamics and control (CHEE 319, CHEE 434)

• The follow‐up course, CHEE 222 “Process Dynamics andNumerical Methods”, builds on the material learned in CHEE221, and introduces: transient (time‐varying) behaviour larger scale problems  systems of equations

CHEE 221

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An actual manufacturing process (4th year project)

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Textbook vs. Real Life Problems

Textbook Problems:– are clearly defined– have only one correct answer– have exactly the right amount of information needed to solve the 

problem– are designed to stress concepts and execution (this course)

Real Life Problems:– may have difficulty defining what the real problem is– may not have all the data required to solve the problem– require use of approximate correlations or assumptions based on 

common sense or experience– have more than one correct answer, each with its advantages and 

disadvantages

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A textbook Material Balance problem (F&R Ex 4.7‐3): 

Methanol is produced in the reaction of carbon dioxide and hydrogen:CO2 + 3H2 CH3OH + H2O

The fresh feed to the process contains hydrogen, carbon dioxide, and0.400 mole% inerts (I). The reactor effluent passes to a condenser thatremoves all the methanol and water formed and none of the reactants orinerts. The latter substances are recycled to the reactor. To avoidbuildup of the inerts in the system, a purge stream is withdrawn from therecycle.

The feed to the reactor (not the fresh feed to the process) contains 28.0mole% CO2, 70.0 mole% H2, and 2.00 mole% inerts. The single‐passconversion of hydrogen is 60.0%. Calculate the molar flow rates andmolar compositions of the fresh feed, the total feed to the reactor, therecycle stream, and the purge stream for a methanol production rate of155 kmol CH3OH/h.

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A simplified manufacturing process (221 style)

FreshFeed

Reactor SeparatorsProducts,Reactants,Byproducts

Recycled Reactants

Byproducts

Products

Energy In

Energy Out$$ In

More $$$ Out

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Significance of M&E Balances

• M&E balances provide a basis for modeling and analyzingon paper (or by computer) systems that would be difficultand/or expensive to study in the lab

• M&E balances assist in the synthesis of chemicalprocesses, and evaluation of design alternatives

• M&E balances provide a basis for estimating the economiccosts and benefits of a project

• M&E balances play an important role in assessing theenvironmental impact of processes/products in our world

CHEE 221

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CHEE 221: Learning Objectives

• Given a process description, you will be able to:– draw and fully label a process flow diagram (PFD);– choose an appropriate basis of calculation;– identify the subsystems for which balances might be written (for a multiple unit process); 

– perform a degree‐of‐freedom analysis for the overall system and each possible subsystem;

– formulate and simplify the appropriate material and energy balance equations, and perform the necessary calculations

You will become proficient at performing these analyses forsingle‐unit and multiple‐unit systems, for processes involvingrecycle, bypass or purge streams, and for processes involvingreactions.CHEE 221

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• Understand and apply the first law of thermodynamics(conservation of energy), calculate energy and enthalpychanges using tabulated data and heat capacities, andconstruct energy balances on closed and open systems.

• Be familiar with basic process terminology (batch, semibatch,continuous; purge and recycle; …), standard operations(reaction, distillation, absorption, extraction, …), and greenengineering concepts (life‐cycle analysis, design for wasteminimization, …).

• Have a sense of why these basic skills are required andimportant for all chemical engineers, independent of their finalcareer choice.

CHEE 221: More Objectives

CHEE 221

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CHEE 221 Textbook: Mandatory. Buy it ASAP.

“Elementary Principles of Chemical Processes” 3rd Edition, 2005 by Felderand Rousseau. It is an excellent textbook, and will be a useful reference forother courses.

Needed for assignments. Contains all the concepts covered in class, and has lots of additional good examples

Contains useful data tables and conversion factors  (Appendix B and inside the front and back covers)

“Test Yourself” questions (with answers) located throughout the text help ensure you understand the required concepts

Accompanying website: http://bcs.wiley.com/he‐bcs/Books?action=index&itemId=047168757X&bcsId=8675

Student workbook contains detailed outlines of solutions to selected chapter‐end problems

E‐book version is fine (quizzes and exam are closed book)

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CHEE 221 Lectures – Fall 2015

Monday 1:30Wednesday 12:30

Friday 11:30

Kingston Hall 101

Lecture slides are posted on the course website:  

http://www.chemeng.queensu.ca/courses/CHEE221/chee221‐course‐content

Lectures will address the main course concepts and the problem solvingprocedures to be used in CHEE 221. The concepts will be demonstrated andreinforced by working through numerous examples (with your participation);the solutions for these examples are not included with the posted slides.

Please bring copies of the lecture outlines with you to each class.

I will communicate with you via email, and announcements in class.

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Tutorials

Tuesdays 8:30 – 9:20 in Macdonald 1– Yes, it is early in the morning, but come prepared to work on the 

problems posted in advance.– Always bring a calculator, the questions, and your textbook

Yes, there is a tutorial tomorrow!  Week 1 questions provide a review of material that you are expected to know coming into the course.

For most tutorials (but not this week), there is a “pre‐tutorial exercise” that you need to complete.

See the Tutorial webpage for details

Pre‐tutorial exercises – 5%• Posted on tutorial webpage 

Assignments – 15%• 5‐7 assignments over the term, consisting of 3‐6 questions. A subset

of the questions will be marked.• Submit assignments to CHEE 221 drop box (outside Dupuis 215) by the

indicated due date and time. The box is cleared at the specified time.Late assignments are not accepted (grade of zero).

Quizzes (3) – 30%• Closed book, during tutorial or class period (approximately Weeks 4, 7 

and 11– exact timing will be announced in advance).

Final Exam – 50%• Closed book 3 hour exam based on the entire term’s work. 

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CHEE221 (fall 2015): Evaluation

CHEE 221

Passing CHEE Courses: It is Departmental Policy that students must pass theindividual examination component (comprised of quizzes, midterms and thefinal exam) of a course to receive a passing grade. If a student does not passthe individual examination component, he/she will fail the entire course andbe allocated a mark of 47% or his/her actual mark, whichever is lower.

If a student misses a midterm test or quiz for legitimate reasons, and providesthe required supporting documentation , the weight of the midterm/quiz willbe reassigned to the quizzes and/or final exam, at the discretion of theinstructor. Otherwise, a missed midterm test or quiz will be given a grade ofzero. No make‐up midterm tests or quizzes will be provided.

Don’t make holiday plans until the exam schedule is finalized. You must writethe exam on the scheduled day, unless there is a conflict recognized by theExams Office (two exams in the same slot, etc…)

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Evaluation… Important policies!

http://chemeng.queensu.ca/undergraduate‐studies/Departmental‐Undergraduate‐Polices.htmlCHEE 221

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Queen's University Policy on Academic DishonestyPlagiarism: Presenting another's ideas or phrasings as one's own without proper

acknowledgement. Examples: copying and pasting from the internet, a printedsource, or other resource without proper acknowledgement; copying fromanother student; using direct quotations or large sections of paraphrased materialin an assignment without appropriate acknowledgement; submitting the samepiece of work in more than one course without the permission of the instructor(s).

Use of unauthorized materials: Examples: possessing or using unauthorized studymaterials or aids during a test; copying from another's test paper; using anunauthorized calculator or other aids during a test; unauthorized removal ofmaterials from the library, or deliberate concealment of library materials.

Facilitation: Deliberately enabling another's breach of academic integrity. Examples:knowingly allowing one's essay or assignment to be copied by someone else forthe purpose of plagiarism; buying or selling of term papers or assignments andsubmitting them as one's own for the purpose of plagiarism.

Forgery: Submitting counterfeit documents or statements. Examples: creating atranscript or other official document; creating a medical note.

Falsification: Misrepresentation of one's self, one's work or one's relation to theUniversity. Examples: altering transcripts or other official documents relating tostudent records; impersonating someone in an examination or test; submitting atake‐home examination written, in whole or in part, by someone else; fabricatingor falsifying laboratory or research data.

http://engineering.queensu.ca/policy/Honesty.html

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Queen's University Policy on Academic Dishonesty

If you are considering copying an assignment, you arefar better off just not handing one in. Lending andcopying assignments are contrary to the Queen’s Policyon Academic Honesty, and will be dealt with harshly.Don’t do it.

But working in small groups is fine:Assignments can be completed in ones, twos, or threes(maximum is 3 people to one assignment); make sure that youwrite all names and student numbers on the submittedassignment

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CHEE 221: What’s coming up

Week Topic Textbook

Next lecture + Wk 1 tutorial Review Material Ch 2-3 + Ideal Gas Law

1 – 6 Material Balances Chapter 4

7 – 12 Energy Balances Chapters 7 – 9

10 or 11 Open-ended problem, Environmental aspects

It is not good enough to understand the “concepts” (in thiscourse these are relatively easy); you must be able to solve theproblems and get the right answers. You will need lots ofpractice (class and textbook examples, tutorials, assignments) inorder to execute the calculations well.