Chapter 1 Introduction to Material Balancess

<span class='text_page_counter'>(1)</span>Undergraduate  Lectures  on  .  . Material  Balances  for  Chemical  Engineers   June  5-­‐  20,  2014. Chapter  1:  Lecture  1:   Overview! Brian  G.  Higgins   Department  of  Chemical  Engineering  and    Materials  Science   University  of  California,  Davis   Class  Web  Site:  h.ps://sites.google.com/site/ekayasolu9onsteachingvietnam/    .

<span class='text_page_counter'>(2)</span> Our  schedule  for  the  next  two  weeks   • • • • • • •. Monday-­‐Friday:  9:00-­‐12:00  noon   Tuesday/Thursday:  13:00-­‐15:00   First  exam:  Friday  9:00-­‐11:00  June  13,2014   Second  Exam:  Friday  9:00-­‐11:00,  June  20,2014   Homework  problems  due  almost  every  day   Lectures  will  follow  textbook  closely.   Most  of  problems  taken  from  textbook  .

<span class='text_page_counter'>(3)</span> How  this  class  relates  to  other  classes  in  the  program  . • Junior  Year   – – – – –. Fall:  ECH152A  Chemical  Thermodynamics  Chapters  3,  4  and  5)   Winter:  ECH141  Fluid  Mechanics  (Chapters  3  &  4)   Spring:  ECH142  Heat  Transfer  (Chapter  8)   Spring:  ECh143  Mass  Transfer  (Chapters  3,4,5,6,8)   Spring:  ECH152b  Thermodynamics  (Chapters  6,7,8)  . • Senior  Year   – Winter:  ECH146  Kine9cs  and  Reac9on  Engineering  (Chapters  6,7,8,9)  .

<span class='text_page_counter'>(4)</span> What  is  Chemical  Engineering?   Chemical  engineering  deals  with  the  transforma9on  of  ma.er  through  chemical    reac9ons  to  form  new  chemical,  materials  and  products.        . What  is  the  role  of  Chemical  Engineers?  . Chemical  engineers  draw  on  fundamental  sciences  with  sound     engineering  prac9ce  to  design  environmentally  safe  processes  that     are  economical  in  the  global  market.     Chemical  engineers  use  principles  of  op9miza9on,  design  and  process  control  in   developing  new  processes  .

<span class='text_page_counter'>(5)</span> Examples   – Petrochemical  industry:  . • Manufacture  of  gasoline,  jet  fuel,  lubrica9ng  oils,  waxes,  asphalt,  coke  . – Chemical  Industry:   • New  chemicals  . – Food  Industry:  . • Use  of  heat  to  transform  ma.er,  cerviche  (“cold  cooking”),  process  foods  . – Packaging  industry  . • Novel  packaging  for  food  products,  biodegradable  plas9c  bo.les  . – Prin9ng  Industry  . • High  speed  prin9ng,  on-­‐demand  prin9ng,  printable  electronics  . – Electronics  Industry:  . • Manufacture  of  semiconductor  chips,  op9cal  switches,  polymer  photo-­‐voltaics,  fuel   cells  . – Biochemical  Industry:  . • Pharmaceu9cals,  enzymes  bio-­‐fuels  .  .

<span class='text_page_counter'>(6)</span> What  is  material  balances  all  about?   Mass  is  conserved   or     Mass  is  neither  created  or  destroyed   Example:  Combus9on  process  . SO2  needs  to  be   removed  from   stack  gases  . What  is  happening  in  a  combusSon  process?   The  need  to  keep  track  of  atoms/molecular  species!  .

<span class='text_page_counter'>(7)</span> What  is  happening  in  a  scrubber  process?   Limestone  -­‐  Ca(OH)2  is  used  to  absorbed  unwanted    SO2  . (Homogeneous  versus  heterogeneous  reacSon)  . Limestone/water  slurry  . Need  to  keep  track  of  atoms  .

<span class='text_page_counter'>(8)</span> Material  Balances  and  Environmental   QuesSons   Water  balance  for  Mono  Lake,  Northern  Sierras,  Nevada     Sources  and  sinks  of  water  must  be  in  balance  . Note:  two  major  sinks:  evapora9on  and  water  “export”  to  Los  Angeles   What  is  the  final  shape/quality  of  the  lake.    .

<span class='text_page_counter'>(9)</span> Environmental  Disaster:  Aral  Sea  in  Kazakhstan  . Lake    Balkhash    13th  largest  lake    is  now  also  threatened.  . In  1980’s  Aral  Sea  was  the  4th  largest  freshwater     lake  in  the  world.  Now,  it's  only  10%  of  its     former  size!  .

<span class='text_page_counter'>(10)</span> Chemical  Processes  . Flow  sheet  of  a  chemical  process  for  manufacture    of  ethyl  alcohol  from  ethylene     Need  to  keep  track  of  atoms/molecular  species  .

<span class='text_page_counter'>(11)</span> Key Principles for Analysis of Reacting Systems Topics  for  this  class  . • Mass must be conserved • Atomic species of a reacting systems cannot be created or destroyed. Topics  for  future  classes  . • Balance of momentum must be satisfied • Balance of thermal energy must be satisfied • Thermodynamic relations must be satisfied.

<span class='text_page_counter'>(12)</span> Analysis of Chemical Reactors and the Connecting Disciplines Fluid  Mechanics  . Thermodynamics  . Kine9cs  . Heat  Transfer  . Chemical   Reactor  . Mathema9cs  . Mass  Transfer  . Chemical reactors are the linchpin in a chemical plant for controlling, optimizing, manipulating the transformation of matter through chemical reactions.

<span class='text_page_counter'>(13)</span> Example of Reacting System Incomplete combustion of ethane Output of reactor can be measured. Reactor. How is the reactor performance dictated by: reactor temperature? (how does T varying within reactor) residence time of reactor? inlet/exit compositions? (how does Ci varying within reactor) laminar vs turbulent flow? use of catalysts?(homogeneous vs hetrogeneous reactions).

<span class='text_page_counter'>(14)</span> Industrial Reactors Catalytic cracker (petroleum refinery) Multiphase slurry reactor. Fermentors (Pharmaceuticals).

<span class='text_page_counter'>(15)</span> Microfluidic  Reactors   (Lab  -­‐on  -­‐  Chip)  . Reaction front. Huang & Higgins 2008.

<span class='text_page_counter'>(16)</span>     Biochemical  Reactors:   An  area  of  increasing  importance  for  chemical   engineers  . In  a  chemostat,  nutrients  and  oxygen  enter  a  well-­‐mixed  tank  containing     a  cell  culture,  and  biological  reac9ons  generate  new  cells  that  are  harvested     in  the  product  stream.  This  biological  process  are  analyzed  using  Material  Balances  .

<span class='text_page_counter'>(17)</span> Hierarchy  of  length  scales  associated  with  the   producSon  of  ethyl  alcohol.    . Concept  of  control  volumes  to  analyze  process  at  different  length  scales  .

<span class='text_page_counter'>(18)</span> The  analysis  of  a  scrubber  . The  concept  of  analyzing  small  parts  of  a  problem  and  then  assembling    the  small  parts  into  a  comprehensive  representaSon  of  the  whole  problem    is  extremely  important.      In  addiSon,  the  concept  of  studying  the  whole  problem  and  then  breaking    it  apart  into  smaller  problems  is  also  extremely  important    .

<span class='text_page_counter'>(19)</span>