39
Theory and Operation of Methanol Synthesis Gerard B. Hawkins Managing Director, CEO

Methanol Synthesis - Theory and Operation

Embed Size (px)

DESCRIPTION

Flowsheets Catalysts Catalyst Deactivation

Citation preview

Page 1: Methanol Synthesis - Theory and Operation

Theory and Operation of Methanol Synthesis

Gerard B. Hawkins Managing Director, CEO

Page 2: Methanol Synthesis - Theory and Operation

Introduction

Flowsheets Catalysts Catalyst Deactivation

Page 3: Methanol Synthesis - Theory and Operation

Methanol Flowsheet

Page 4: Methanol Synthesis - Theory and Operation

Methanol Flowsheet

Natural Gas

Sulphur Removal Saturator

Reforming

Air Condensate

Compression

BFWDemin Water

CW

CW

SynthesisDistillation

MP Steam

Purge to Fuel

Crude Methanol

ProductMethanol

Fusel Oil

Refining Column Bottoms

HP Steam

Page 5: Methanol Synthesis - Theory and Operation

Methanol Synthesis Reactions Purpose of synthesis loop is to convert H2, CO

and CO2 to methanol CO + 2H2 CH3OH ∆H = - 90.64 kJ/kmol CO + H2O CO2 + H2 ∆H = - 41.17

kJ/kmol Both reactions are revisible and exothermic Combine to give

CO2 + 3H2 CH3OH + H2O ∆H = - 49.74

kJ/kmol

Page 6: Methanol Synthesis - Theory and Operation

Methanol Synthesis Reactions

Methanol is produced from CO2

Proven by use of radioactive C14

CO is shifted to CO2 and then to methanol

Rate of reaction is given by 5.0

2

2]./[3

][][.exp.

OHPCOPActivity

dtOHdCH TRE∆−∝

Page 7: Methanol Synthesis - Theory and Operation

Equilibrium Equilibrium defined by

Which can be rearranged to

Which is far more useful

[ ] [ ][ ] [ ]322

23

..HPCOP

OHPOHCHPKp =

[ ][ ] [ ]322

23 .

][.HPCOPOHPKpOHCHP =

Page 8: Methanol Synthesis - Theory and Operation

Effect of Temperature on Kp

Page 9: Methanol Synthesis - Theory and Operation

Effect of Temperature on CH3OH %

Page 10: Methanol Synthesis - Theory and Operation

Effect of Pressure on CH3OH %

Page 11: Methanol Synthesis - Theory and Operation

Definition of ATE

Page 12: Methanol Synthesis - Theory and Operation

Effect of Operating Parameters on Equilibrium and Kinetics

For good conversion need following conditions

Parameter Equilibrium Kinetics Temperature Low High Pressure High High Catalyst Activity High High So there is a conflict for temperature

Page 13: Methanol Synthesis - Theory and Operation

Effect of Operating Temperature on Equilibrium and Kinetics

Page 14: Methanol Synthesis - Theory and Operation

Concept of Maximum Rate Line If reaction follows the max rate line then

minimum catalyst volume for maximum production

Page 15: Methanol Synthesis - Theory and Operation

Methanol Synthesis Catalyst VSG-M101

Available as • VSG-M101

Synthesis of methanol • from mixtures of CO, CO2 and H2

Copper on a ZnO-Al2O3 support Proprietary metal oxides are added to

prevent sintering and improve dispersion of copper crystallites

Page 16: Methanol Synthesis - Theory and Operation

Methanol Synthesis Catalyst History

Over 30 years manufacturing experience

45,000+ m³ of methanol synthesis catalyst made

4,000 m³ of VSG-M101series catalyst currently installed in PRC

Page 17: Methanol Synthesis - Theory and Operation

Methanol Synthesis Catalyst Properties

Effect Property Activity - Copper surface area Life - Microstructure Strength - Macrostructure Selectivity - Formulation

Page 18: Methanol Synthesis - Theory and Operation

Methanol Synthesis Catalyst Properties

Typical composition for VSG-M101 • CuO 64 wt% • Al2O3 10 wt% • ZnO 24 wt%

Page 19: Methanol Synthesis - Theory and Operation

Methanol Synthesis Catalyst Properties

Spherical Pellet • Diameter 5 mm • Height 4 - 5 mm

Bulk density 1,400 - 1,600 kg/m³ Radial crush strength >205N/m

Page 20: Methanol Synthesis - Theory and Operation

Methanol Synthesis Catalyst Poisons

Poison Sulfur Chlorine Iron Elemental Carbon Metals e.g. V, K, Na Nickel Ammonia HCN Oxygen Ethene Ethyne Particulates

Effect & Limit Activity, 0.20% mass Activity, 0.02% mass 0.15% mass Absent Selectivity, Absent Selectivity, 0.04% mass TMA, 10 ppmv Amines, Absent Activity, 1000 ppm 20 ppmv 5 ppmv Absent

ppmv figures refer to MUG composition.

% mass figures refer to accumulation on catalyst.

Page 21: Methanol Synthesis - Theory and Operation

Relationship of Copper Surface Area and Activity

0 10 20 30 40 0

0.2

0.4

0.6

0.8

1

1.2

Copper Surface Area m2/gram

Activ

ity

Copper Surface Area

Page 22: Methanol Synthesis - Theory and Operation

VSG-M101Properties

As noted before, • Catalyst deactivation is caused by thermal

sintering • Copper crystallites grow - the surface area

falls It also improves the catalyst's ability to

maintain the separation of crystallites with time • This prevents sintering and so activity is more

stable

Page 23: Methanol Synthesis - Theory and Operation

Catalyst Deactivation

Either by • Sintering • Poisoning from

Sulfur Chlorides Carbonyls

Page 24: Methanol Synthesis - Theory and Operation

Thermal Sintering Historically always believed to be due to

thermal sintering But also reactant and carbonyl poisoning Thermal sintering of copper catalysts is

unavoidable Rate is critically dependent on temperature

• Therefore the hotter the catalyst the faster the rate of deactivation

• Operation at low temperatures reduces activity loss due to sintering

Rate of sintering slows as the catalyst ages

Page 25: Methanol Synthesis - Theory and Operation

What Causes Thermal Sintering ?

Hence activity rules reflected this by defining activities by temperature bands

Also defined activities by converter type • This does include a temperature effect • Also effect of gas mal distribution • For example cold cores in Quench

Lozenge converters

Page 26: Methanol Synthesis - Theory and Operation

How does catalyst deactivate ?

Cu Cu

Cu

Cu

Cu

Cu Cu

Cu

Cu

Cu

Cu

Cu Cu

• Thermal sintering –Cu molecules migrate and join other Cu particles to

make bigger particles but with a smaller surface area

Page 27: Methanol Synthesis - Theory and Operation

Sulfur Poisoning Sulfur is a powerful poison for Cu/Zn catalysts

The ZnO component provides a sink for sulfur by formation of ZnS

An effective catalyst requires an intimate mixture of Cu and ZnO and a high free ZnO surface area

Page 28: Methanol Synthesis - Theory and Operation

Chloride Poisoning

Chloride reacts with copper to form CuCl (mp = 430oC)

CuCl provides a mechanism for loss of activity by sintering

Catalyst requires well dispersed and stabilized copper to minimize the effects of chloride poisoning

Page 29: Methanol Synthesis - Theory and Operation

Catalyst Deactivation Model

0.175

0.275

0.375

0.475

0.575

0 12 24 36 48

Time Months

Activ

ity

High Temperature Operation

Low Temperature Operation

Page 30: Methanol Synthesis - Theory and Operation

What Causes Deactivation ?

Now looking at the effect of Iron and Nickel Carbonyls

Seen some high levels 5,000 ppm on discharged catalyst samples

Looking at the most effective guard beds

Could be worth 10 % extra on activity Consider the above to be confidential

Page 31: Methanol Synthesis - Theory and Operation

Copper Surface Area’s of Catalyst

0

1 Act

ivity

Comp A Comp A2 Comp B Comp C Comp C2 VSG-M101

1.80

Page 32: Methanol Synthesis - Theory and Operation

Activity of VSG-M101

Time on line (months) 0 2 4 6 8 10

0.0 0.1

0.2 0.3 0.4

Rel

ativ

e ac

tivity

0.5

VULCAN VSG-M101

VULCAN VSG-M101D

0.6

0.7

0.8

0.9

Page 33: Methanol Synthesis - Theory and Operation

Converter Types

Many different converter types • Tube Cooled • Quench Lozenge; ARC and CMD • Steam raising

Aim is the same • Keep process gas cool • Contain the catalyst • Maximize reaction rate

Page 34: Methanol Synthesis - Theory and Operation

Loop Design

Very similar not matter what type of converter

Page 35: Methanol Synthesis - Theory and Operation

Quench Type Converters Original – very simple mechanical design not the

most efficient Replaced with slightly more complex design which

is more efficient (better mixing)

ARC Converter

Quench Converter

Page 36: Methanol Synthesis - Theory and Operation

Tube Cooled Converters

Very simple design which integrates catalyst and process gas preheat

Allows for heat recovery into saturator circuit

TCC Design

Page 37: Methanol Synthesis - Theory and Operation

Steam Raising Many types Recover heat to steam Tracks max rate line closely Each has own Pro’s and Con’s

Linde Variobar

Toyo MRF

Lurgi SRC

Page 38: Methanol Synthesis - Theory and Operation

Process Information Disclaimer Information contained in this publication or as otherwise supplied to Users is believed to be accurate and correct at time of going to press, and is given in good faith, but it is for the User to satisfy itself of the suitability of the Product for its own particular purpose. GBHE gives no warranty as to the fitness of the Product for any particular purpose and any implied warranty or condition (statutory or otherwise) is excluded except to the extent that exclusion is prevented by law. GBHE accepts no liability for loss or damage resulting from reliance on this information. Freedom under Patent, Copyright and Designs cannot be assumed.

Page 39: Methanol Synthesis - Theory and Operation