Aspen Methanol Workshop

Reach Your

True

Potential

Full-Scale Plant Modeling Workshop Objective:  Practice and apply many of the techniques used in this course and learn how to best approach modeling projects

Introduction to Aspen Plus  ® 

258

 ©1998 AspenTech. All rights reserved.

Full-Scale Plant Modeling Workshop Objective: Model a methanol plant. The process being modeled is a methanol plant. The basic feed streams to the plant are Natural Gas, Carbon Dioxide (assumed to be taken from a nearby Ammonia Plant) and Water. The aim is to achieve the methanol production rate of approximately 62,000 kg/hr, at a purity of at least 99.95 % wt. This is a large flowsheet that would take an experienced  engineer more than an afternoon to complete. Start  building the flowsheet and think about how you would  work to complete the project. Septiembre 12, 2001  ® 

Introduction to Aspen Plus

Slide 259  ©1998 AspenTech. All rights reserved.

General Guidelines • Build the flowsheet one section at a time. • Simplify whenever possible. Complexity can always be added later.

• Investigate the physical properties.  Use Analysis.  Check if binary parameters are available.  Check for two liquid phases.  Use an appropriate equation of state for the portions of the flowsheet involving gases and use an activity coefficient model for the sections where non-ideal liquids may be present. Septiembre 12, 2001  ® 

Introduction to Aspen Plus

Slide 260  ©1998 AspenTech. All rights reserved.

Full-Scale Plant Modeling Workshop Air

FURNACE

Fuel

MEOHRXR

SYNCOMP

SPLIT1

COOL4

E121

SPLIT2

FL3 COOL2 COOL3 MKUPST

M2 FEEDHTR

FL2

MIX2

COOL1

CIRC E122 FL4

BOILER FL1 H2OCIRC

REFORMER

CO2 CO2COMP M1

NATGAS

E223

E124

SATURATE

TOPPING

CH4COMP REFINING

M4

MKWATER

Septiembre 12, 2001  ® 

Introduction to Aspen Plus

Slide 261  ©1998 AspenTech. All rights reserved.

FL5

Part 1: Front-End Section From Furnace

MKUPST

M2

FEEDHTR To BOILER

REFORMER

H2OCIRC CO2

CO2COMP

NATGAS

Septiembre 12, 2001  ® 

M1

SATURATE

CH4COMP

Introduction to Aspen Plus

Slide 262  ©1998 AspenTech. All rights reserved.

Part 1: Front-End Section (Continued) 1. Front-end Section Carbon Dioxide Stream – CO2 • Temperature = 43 C • Pressure = 1.4 bar • Flow = 24823 kg/hr • Mole Fraction  CO2 - 0.9253  H2 - 0.0094  H2O - 0.0606  CH4 - 0.0019  N2 - 0.0028 Natural Gas Stream - NATGAS • Temperature = 26 C • Pressure = 21.7 bar • Flow = 29952 kg/hr • Mole Fraction  CO2 - 0.0059  CH4 - 0.9539  N2 - 0.0008  C2H6 - 0.0391  C3H8 - 0.0003 Septiembre 12, 2001  ® 

Circulation Water - H2OCIRC • Pure water stream • Flow = 410000 kg/hr • Temperature = 195 C • Pressure = 26 bar Makeup Steam - MKUPST • Stream of pure steam • Flow = 40000 kg/hr • Pressure = 26 bar • Vapor Fraction = 1 • Adjust the makeup steam flow to achieve a desired steam to methane molar ratio of 2.8 in the Reformer feed REFFEED.

Introduction to Aspen Plus

Slide 263  ©1998 AspenTech. All rights reserved.

Part 1: Front-End Section (Continued) Carbon Dioxide Compressor - CO2COMP • Discharge Pressure = 27.5 bar • Compressor Type = 2 stage Natural Gas Compressor - CH4COMP • Discharge Pressure = 27.5 bar • Compressor Type = single stage Reformer Process Side Feed Stream Pre-Heater - FEEDHTR • Exit Temperature = 560 C • Pressure drop = 0 Saturation Column - SATURATE • 1.5 inch metal pall ring packing. • Estimated HETP = 10 x 1.5 inches = 381 mm • Height of Packing = 15 meters • No condenser and no reboiler. Reformer Reactor - REFORMER • Consists of two parts: the Furnace portion and the Steam Reforming portion • Exit Temperature of the Steam Reforming portion = 860 C • Pressure = 18 bar

Septiembre 12, 2001  ® 

Introduction to Aspen Plus

Slide 264  ©1998 AspenTech. All rights reserved.

Part 2: Heat Recovery Section SYNCOMP To Methanol Loop

COOL4 FL3

COOL2

COOL3

FL2

COOL1 From Reformer BOILER

FL1

To REFINING

Septiembre 12, 2001  ® 

To TOPPING

Introduction to Aspen Plus

Slide 266  ©1998 AspenTech. All rights reserved.

Part 2: Heat Recovery Section (Continued) 2. Heat Recovery Section

•

This section consists of a series of heat exchangers and flash vessels used to recover the available energy and water in the Reformed Gas stream.

BOILER • Exit temperature = 166 C • Exit Pressure= 18 bar

FL1 • Pressure Drop = 0 bar • Heat Duty = 0 MMkcal/hr

COOL1 • Exit temperature = 136 C • Exit Pressure = 18 bar

FL2 • Exit Pressure = 17.7 bar • Heat Duty = 0 MMkcal/hr

COOL2 • Exit temperature = 104 C • Exit Pressure = 17.9 bar

FL3 • Exit Pressure = 17.4 bar • Heat Duty = 0 MMkcal/hr

COOL3 • Exit temperature = 85 C • Pressure Drop = 0.1 bar

SYNCOM • Two Stage Polytropic compressor • Discharge Pressure = 82.5 bar • Intercooler Exit Temperature = 40 C

COOL4 • Exit temperature = 40 C • Exit Pressure = 17.6 bar Septiembre 12, 2001  ® 

Introduction to Aspen Plus

Slide 267  ©1998 AspenTech. All rights reserved.

Part 3: Methanol Synthesis Section MEOHRXR To Furnace

SPLIT1 From SYNCOMP E121 SPLIT2 MIX2

CIRC E122

FL4 E223

E124 To FL5

Septiembre 12, 2001  ® 

Introduction to Aspen Plus

Slide 269  ©1998 AspenTech. All rights reserved.

Part 3: Methanol Synthesis Section (Continued) 3. Methanol Synthesis Loop Section Methanol Reactor - MEOHRXR • Tube cooled reactor • Exit Temperature from the tubes = 240 C • No pressure drop across the reactor • Reactions − CO + H2O CO2 + H2 − CO2 + 3H2 CH3OH + H2O − 2CH3OH DIMETHYLETHER + H2O − 4CO + 8H2 N-BUTANOL + 3H2O − 3CO + 5H2 ACETONE + 2H2O

(Equilibrium) (+15 C Temperature Approach) (Molar extent 0.2kmol/hr) (Molar extent 0.8kmol/hr) (Molar extent 0.3kmol/hr)

E121 • Exit Temperature - 150 C • Exit Pressure - 81 bar

FL4 • Exit Pressure = 75.6 bar • Heat Duty = 0 MMkcal/hr

E122 • Cold Side Exit Temperature - 120 C

CIRC • Single stage compressor • Discharge Pressure = 83 bar • Discharge Temperature = 55 C

E223 • Exit Temperature - 60 C • Exit Pressure - 77.3 bar E124 • Exit Temperature - 45 C • Exit Pressure - 75.6 bar Septiembre 12, 2001  ® 

SPLIT1 • Split Fraction = 0.8 to stream to E121 SPLIT2 • Stream PURGE = 9000 kg/hr • Stream RECYCLE = 326800 kg/hr Introduction to Aspen Plus Slide 270  ©1998 AspenTech. All rights reserved.

Part 4: Distillation Section To Furnace

From FL4

From COOL1

FL5

From COOL2

TOPPING REFINING

M4

MKWATER

Septiembre 12, 2001  ® 

Introduction to Aspen Plus

Slide 272  ©1998 AspenTech. All rights reserved.

Part 4: Distillation Section (Continued) 4. Distillation Section Makeup Steam - MKWATER • Stream of pure water • Flow = 10000 kg/hr • Pressure = 5 bar • Temperature = 40 C • Adjust the make-up water flow (stream MKWATER) to the CRUDE stream to achieve a stream composition of 23 wt.% of water in the stream feeding the Topping column (stream TOPFEED) to achieve 100 ppm methanol in the Refining column BTMS stream. Topping Column - TOPPING • Number of Stages = 51 (including condenser and reboiler) • Condenser Type = Partial Vapor/Liquid • Feed stage = 14 • Distillate has both liquid and vapor streams • Distillate rate = 1400 kg/hr • Pressure profile: stage 1 = 1.5 bar and stage 51 = 1.8 bar • Distillate vapor fraction = 99 mol% • Stage 2 heat duty = -7 Mmkcal/hr • Stage 51 heat duty Specified by the heat stream • Reboiler heat duty is provided via a heat stream from block COOL2 • Boil-up Ratio is approximately 0.52 • Valve trays • The column has two condensers. To represent the liquid flow connections a pumparound can be used between stage 1 and 3. Septiembre 12, 2001  ® 

Introduction to Aspen Plus

Slide 273  ©1998 AspenTech. All rights reserved.

Part 4: Distillation Section (Continued) Distillation Section (Continued) Refining Column - REFINING • Number of Stages = 95 (including condenser and reboiler) • Condenser Type = Total • Distillate Rate = 1 kg/hr • Feed stage = 60 • Liquid Product sidedraw from Stage 4 @ 62000 kg/hr (Stream name – PRODUCT) • Liquid Product sidedraw from Stage 83 @ 550 kg/hr (Stream name – FUSELOIL) • Reflux rate = 188765 kg/hr • Pressure profile: stage 1= 1.5bar and stage 95=2bar • Reboiler heat duty is provided via a conventional reboiler supplemented by a heat stream from a heater block to stage 95 • Boil-up Ratio is approximately 4.8 • Valve trays • To meet environmental regulations, the bottoms stream must contain no more than 100ppm by weight of methanol as this stream is to be dumped to a nearby river. FL5 • Exit Pressure • Heat Duty

5 bar 0 MMkcal/hr

M4

•

For water addition to the crude methanol Septiembre 12, 2001

 ® 

Introduction to Aspen Plus

Slide 274  ©1998 AspenTech. All rights reserved.

Part 5: Furnace Section

To REFORMER From FL5 Air

From SPLIT2 FURNACE

Fuel

Septiembre 12, 2001  ® 

Introduction to Aspen Plus

Slide 276  ©1998 AspenTech. All rights reserved.

Part 5: Furnace Section (Continued) 5. Furnace Section Air to Furnace - AIR • Temperature = 366 C • Pressure = 1 atm • Flow = 281946 kg/hr • Adjust the air flow to achieve 2%(vol.) of oxygen in the FLUEGAS stream. Fuel to Furnace - FUEL • Flow = 9436 kg/hr • Conditions and composition are the same as for the natural gas stream

Septiembre 12, 2001  ® 

Introduction to Aspen Plus

Slide 277  ©1998 AspenTech. All rights reserved.