Module 5 process integration of heat and mass chapter 10
Download
1 / 34

Module 5: Process Integration of Heat and Mass Chapter 10 - PowerPoint PPT Presentation


  • 392 Views
  • Uploaded on

Module 5: Process Integration of Heat and Mass Chapter 10. David R. Shonnard Department of Chemical Engineering Michigan Technological University. Module 5: Outline. The environmental performance of a process depends on both the

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Module 5: Process Integration of Heat and Mass Chapter 10' - iden


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Module 5 process integration of heat and mass chapter 10 l.jpg

Module 5: Process Integration of Heat and MassChapter 10

David R. Shonnard

Department of Chemical Engineering

Michigan Technological University


Module 5 outline l.jpg
Module 5: Outline

The environmental performance of a process depends on both the

performance of the individual unit operations, but also on the level

to which the process steams have been networked and integrated

  • Educational goals and topics covered in the module

  • Potential uses of the module in chemical engineering courses

  • Review of heat integration concepts

  • Introduction to the tools of mass integration and synthesis of mass exchange networks - Chapter 10

  • Cast study - heat integration of the MA flowsheet


Module 5 educational goals and topics covered in the module l.jpg
Module 5: Educational goals and topics covered in the module

Students will:

  • learn about efficient utilization of waste streams as raw materials through application of source/sink mapping

  • are introduced to graphical tools of mass exchange network synthesis, composition interval diagrams and load line diagrams.

  • apply mass exchange network synthesis to simple flowsheets


Module 5 potential uses of the module in chemical engineering courses l.jpg
Module 5: Potential uses of the module in chemical engineering courses

Mass/energy balance course:

• dilute contaminant balance calculations around process units

• source/sink matching of energy streams

Continuous/stagewise separations course:

• applications to in-process recovery and recycle of contaminants

Design course:

• graphical design tools for mass integration of waste streams


Module 5 analogies between process heat and mass integration l.jpg
Module 5: Analogies between process heat engineering coursesand mass integration

Heat Integration

the optimum use of heat exchangers and streams internal to the process to satisfy heating and cooling requirements.

Tools: 1. Temperature interval diagram

2. Heat load diagram (pinch diagram)

Mass Integration

the optimum use of mass exchangers and streams internal to the process to satisfy raw material requirements, maximize production and minimize waste generation (water recycle/reuse applications).

Tools: 1. Source/sink mapping and diagrams

2. Composition interval diagram

3. Mass load diagram (pinch diagram)


Module 5 heat exchange networks key features l.jpg
Module 5: Heat exchange networks - engineering courseskey features

T - Heat Load Diagram

• composite curves

• pinch analysis

• minimum external utilities

Heat exchange network

• internal

• external

[(mCp)1 + (mCp) 2]-1

89% reduction in

external utilities

Seider, Seader, and Lewin, 1999, “Process Design Principles”, John Wiley & Sons, Ch. 7


Module 5 heat exchange networks illustrative example before heat integration l.jpg
Module 5: Heat exchange networks - engineering coursesIllustrative example - before heat integration

per sec

1 kg/s, Cp = 1 kJ/(kg-˚C)

2 kg/s, Cp = 1 kJ/(kg-˚C)

per sec


Module 5 heat exchange networks temperature load pinch diagram l.jpg
Module 5: Heat exchange networks - engineering coursesTemperature - load (pinch) diagram

per sec

Placement of each load line vertically is arbitrary

2 kg/s

Cooling load for external network, 160 kJ/s

Heat transfer load by internal network,

140 kJ/s

1 kg/s

Heating load for external network, 30 kJ/s

10 ˚C minimum temperature difference defines the pinch


Module 5 heat exchange networks illustrative example after heat integration l.jpg
Module 5: Heat exchange networks - engineering coursesIllustrative example after heat integration

82.4% reduction in cooling utility

per sec

140 kJ/s transferred

46.7% reduction in heating utility

per sec


Module 5 mass integration objectives and methods l.jpg
Module 5: Mass integration: engineering coursesobjectives and methods

Methods

objective is to prepare source streams to be acceptable to sink units within the process or to waste treatment

1. Segregation

avoid mixing of sources

2. Recycle

direct sources to sinks

3. Interception

selectively remove pollutants from source

4. Sink/generator manipulation

adjust unit operation design or operation

Pollutant-rich streams

Pollutant-lean streams

El-Halwagi, M.M.1997, “Pollution Prevention Through Process Integration: Systematic Design Tools”, Academic Press


Module 5 motivating example chloroethane process before mass integration l.jpg
Module 5: Motivating example: engineering coursesChloroethane process before mass integration

Mass balance in terms of CE, the minor component

Objective is to reduce the concentration of CE sent to biotreatment to < 7 ppm and a load of < 1.05x10-6 kg CE/s

El-Halwagi, M.M.1997, “Pollution Prevention Through Process Integration: Systematic Design Tools”, Academic Press


Module 5 motivating example chloroethane process after mass integration l.jpg
Module 5: Motivating example: engineering coursesChloroethane process after mass integration

Interception

CE load to biotreatment =

2.5x10-7 kg/s

Recycle

El-Halwagi, M.M.1997, “Pollution Prevention Through Process Integration: Systematic Design Tools”, Academic Press


Module 5 mass integration tools source sink mapping l.jpg
Module 5: Mass Integration Tools: engineering coursesSource-sink mapping

the purpose of source-sink mapping is to determine if waste streams can be used as feedstocks within the process - direct recycle

Recycle source “a” directly

A range of acceptable flowrates and composition for each sink , “S”

or mix sources “b” and “c” to achieve the target flowrate - composition using a Lever Rule - like calculation

El-Halwagi, M.M.1997, “Pollution Prevention Through Process Integration: Systematic Design Tools”, Academic Press


Module 5 source sink mapping acrilonitrile an process before recycle l.jpg
Module 5: Source-sink mapping: engineering coursesacrilonitrile (AN) process before recycle

0 ppm NH3

0 ppm AN

required

≤ 10 ppm NH3

may contain AN

450 ˚C,

2 atm

2-phase stream always with 1 kg/s H2O but no H2O in the AN layer

mass fraction of AN always equal to 0.068

NH3 equilibrium

CW = 4.3 CAN

NH3 partitioning

CSTEAM = 34 CPRODICT


Module 5 source sink map acrilonitrile an process l.jpg
Module 5: Source-sink map engineering courses acrilonitrile (AN) process

Sinks for water

Sources for water



Module 5 mass balances on an units for remaining flow rates and compositions l.jpg
Module 5: Mass balances on AN units for remaining flow rates and compositions

Aqueous streams from condenser and distillation column

4.7 kg/s H2O

0.5 kg/s AN

12 ppm NH3

From fresh water supply

1.0 kg/s H2O

0 kg/s AN

0 ppm NH3

Scrubber

Gas stream

from condenser

0.5 kg/s H2O

4.6 kg/s AN

39 ppm NH3

to decanter

? kg/s H2O

? kg/s AN

? ppm NH3


Module 5 flow rates and compositions from scrubber to decanter l.jpg
Module 5: Flow rates and compositions and compositionsfrom Scrubber to Decanter

And similarly for other units


Acrilonitrile an process after recycle l.jpg
acrilonitrile (AN) process after recycle and compositions

freshwater feed 30% of original

AN production rate increased by 0.5 kg/s; $.6/kg AN and 350 d/yr = $9MM/yr

rate of AN sent to biotreatment is 85% of original

60% of original


Module 5 mass exchange network men synthesis l.jpg
Module 5: and compositionsMass exchange network (MEN) synthesis

1. Similar to heat exchange network (HEN) synthesis

2. Purpose is to transfer pollutants that are valuable from waste streams to process streams using mass transfer operations (extraction, membrane modules, adsorption, ..

3. Use of internal mass separating agents (MSAs) and external MSAs.

4. Constraints

i. Positive mass transfer driving force between rich and lean process

streams established by equilibrium thermodynamics

ii. Rate of mass transfer by rich streams must be equal to the rate of

mass acceptance by lean streams

iii. Given defined flow rates and compositions of rich and lean streams


Module 5 mass integration motivating example phenol containing wastewater l.jpg
Module 5: Mass integration motivating example - Phenol-containing wastewater

El-Halwagi, M.M.1997, “Pollution Prevention Through Process Integration: Systematic Design Tools”, Academic Press

Outlet streams for recycle or sale

Mass separating agents

to waste

water

treatment

- Minimize transfer to waste treatment -

to wastewater

treatment


Module 5 outline of men synthesis l.jpg
Module 5: Outline of MEN synthesis Phenol-containing wastewater

1. Construct acomposition interval diagram(CID)

2. Calculate mass transfer loadsin each composition interval

3. Create acomposite load linefor rich and lean streams

4. Combine load lines on a combined load line graph

5. Stream matching of rich and lean streams in a MEN using the CID


Module 5 hypothetical set of rich and lean streams stream properties l.jpg
Module 5: Hypothetical set of rich and lean streams - stream properties

Equilibrium of pollutant between rich and lean streams

y = 0.67 x


Module 5 composition interval diagram a tool for men synthesis l.jpg
Module 5: Composition interval diagram - propertiesa tool for MEN synthesis

x scale matched to y scale using

y = 0.67 x


Module 5 mass transfer loads in each interval l.jpg
Module 5: propertiesMass transfer loads in each interval

Rich Streams

negative mass load denotes transfer out of the stream


Module 5 composite load line for the rich stream l.jpg
Module 5: propertiesComposite load line for the rich stream

Region 1 & 2

Region 3

Region 4

Region 5


Module 5 combined load line for rich and lean streams l.jpg
Module 5: propertiesCombined load line for rich and lean streams

mass load to be added to lean stream externally

mass load to be transferred internally

Rich Stream can be moved vertically

mass load to be removed from rich stream by external

MSA


Module 5 stream matching in men synthesis l.jpg
Module 5: propertiesStream matching in MEN synthesis


Module 5 heat integration of the ma flowsheet l.jpg
Module 5: propertiesHeat integration of the MA flowsheet

-9.23x107 Btu/hr

2.40x107 Btu/hr

9.70x107 Btu/hr

Reactor streams

generate steam

-4.08x107 Btu/hr

Without Heat Integration


Module 5 heat integration of reactor feed and product streams l.jpg
Module 5: Heat integration of propertiesreactor feed and product streams


Module 5 heat integration of absorber outlet and recycle streams l.jpg
Module 5: Heat integration of propertiesabsorber outlet and recycle streams


Module 5 maleic anhydride flowsheet with heat integration l.jpg
Module 5: Maleic anhydride flowsheet propertieswith heat integration


Module 5 heat integration summary l.jpg
Module 5: propertiesHeat integration summary

Greater energy reductions are possible when steam generated from the reactors is used for the reboiler, purge and feed heaters

76.8% reduction

27.4% reduction


Module 5 recap l.jpg
Module 5: Recap properties

  • Educational goals and topics covered in the module

  • Potential uses of the module in chemical engineering courses

  • Review of heat integration concepts

  • Introduction to the tools of mass integration and synthesis of mass exchange networks - Chapter 10

  • Cast study - heat integration of the MA flowsheet


ad