Performance & Operation Improvements using VULCAN Series

VSG-F101 High Temperature Shift Catalysts

By:

Gerard B. Hawkins Managing Director, CEO

Improvements in High Temperature Shift Catalysts

The high temperature shift duty introduction and theory

HTS catalyst characteristics developments over time

Typical HTS operational problems Improved catalysts

VULCAN Series VSG-F101 Series Summary

Improvements in High Temperature Shift Catalysts

The high temperature shift duty Introduction and theory

HTS catalyst characteristics Typical HTS operational problems Improved catalysts and loading regimes Summary

Introduction What is the Shift Reaction ?

Water gas shift reaction has two effects: • generates hydrogen from carbon

monoxide & steam • converts CO to CO2

CO + H2O <=> CO2 + H2

From Steam Reformer HTS LTS Methanation

LTS (optional)

H2

Introduction How to include a Shift Section ?

Liquid CO2

Removal

PSA HTS From Steam Reformer H2

Theory - Equilibrium

CO + H2O CO2 + H2 (+ heat)

• Reaction is reversible

• Forward reaction - moderately exothermic

– equilibrium at lower temperature favors • more CO converted • more H2 produced

• Cannot beat equilibrium !

Theory - Reaction Rate

Reaction Rate depends on • distance from equilibrium

further from equilibrium => larger driving force

• catalyst formulation/activity • operating temperature

Catalyst enables reaction to proceed Higher temperature drives rate

Ideal catalyst promotes rate to achieve equilibrium at low temperature

Improvements in High Temperature Shift Catalysts

The high temperature shift duty HTS catalyst characteristics

developments over time Typical HTS operational problems Improved catalysts and loading regimes Summary

High Temperature Shift Operating Conditions

Inlet CO 8 - 15 % / outlet CO 2 - 4 % (dry)

Bulk of CO conversion > 75 % Typical inlet temp of 335 - 360OC (640 -

680OF) • recent improvements down to 300oC

(575oF) Temperature rise 55 - 65OC (100 - 120OF) Typical lives 3 - 5 years

High Temperature Shift Catalyst Issues

Over-reduction at low steam/dry gas ratio

Cr6+ content Sulfur content Activity Strength

High Temperature Shift Modern Catalyst Features

Iron/chromium/copper oxides catalyst • typical composition 87 % / 10 % / 3% (wt)

Active phase is magnetite, Fe3O4

• supplied as haematite, Fe2O3 • requires reduction

Activity supplemented by Cu • helps avoid over reduction of Fe3O4

Low Cr6+ and SO42-

• typically < 50 (Cr) & < 300 ppmw (S) or better

High Temperature Shift Catalyst Features

To overcome the catalyst issues • Over-reduction

copper promotion • Cr6+ content and sulfur content

production route • High stable activity & high strength

dispersion of iron oxide, Cr2O3 and Cu crystallites low hexavalent chromium copper promotion micro-structure, particularly iron oxide catalyst pellet size options

VULCAN Series VSG-F101 incorporates all the required features

High Temperature Shift Catalyst Structure - General

Small crystals of magnetite high surface area => high activity

Good dispersion of Cr2O3 (Cr3+) gives strength to resist breakage in process

upsets (eg wetting) gives high thermal stability

prevents sintering of Cu and Fe3O4 slows activity loss & increases life

Good dispersion of Cu small crystallites => high Cu surface area =>

high activity slows Cu sintering

50-700 A pore o

Chrome Oxide Crystal

Iron Oxide Crystals

High Temperature Shift Catalyst Structure

Cu Crystals

Amorphous Structure (achieved in VSG-F101)

Microstructure of HTS Catalysts

Crystalline Structure (Competitor)

HTS Catalyst - Addition of Copper 1. Activity

Activity increase due to Cu addition • much higher intrinsic activity than Fe3O4 • increases shift activity

Benefits are • at same SOR inlet temperature, maintain

equilibrium for longer - extend life • achieve equilibrium at lower SOR inlet

temperature - lower CO slip, higher H2 make, slower sintering (deactivation)

• for same SOR inlet temperature and life - decrease catalyst volume

HTS Catalyst - Addition of Copper 1. Activity

Cu issues - overcome by catalyst design • Cu sinters rapidly at HTS operating

temperatures • high Cu levels weaken catalyst structure

=> stabilize by the Fe3O4/Cr2O3 micro-structure

• Pore diffusion controls overall reaction rate

cannot achieve full benefit of Cu intrinsic activity

=> optimize pore structure to maximize benefit

HTS Catalyst - Addition of Copper 2. Over-reduction

Fe3O4 => FeO => Fe • causes increased Fischer-Tropsch activity • C laydown (2CO <=> C + CO2)

For over-reduction to occur • need R ~ 1.5 or higher • corresponds to S/C approx 2.8 in reformer

Reducing (CO)+ (H2)Oxidising (CO2) + (H2O)= Pc = R

HTS Catalyst - Addition of Copper 2. Over-reduction

CO2/CO phase equilibrium Cu increases activity

• rapidly increases p[CO2]/decreases p[CO]

300 350 400 450 500 5500.5

0.70.91.11.31.51.71.9

Temperature (oC)

P[CO2]/P[CO]

Fe

Fe3O4

HTS Catalyst - Addition of Copper 2. Over-reduction

H2O/H2 phase equilibrium • rarely close to boundary • Cu tends towards lower temperature

operation

300 350 400 450 500 5500.1

0.20.3

0.50.7

1

Temperature (oC)

P[H2O]/P[H2]

Fe

Fe3O4

FeO

High Temperature Shift Chromium (VI) Issues

Cr6+ content must be low • Cr6+ can form during manufacture

means less Cr2O3 so affects stability • Cr6+ is a Category 1 carcinogen • Cr6+ is water soluble

can be washed out of catalyst into condensate system (particularly during start-ups)

loss of catalyst strength • upon reduction, Cr6+ gives an exotherm

40OC (72OF) per 1% danger of over-temperature (catalyst;

vessel)

Low Cr6+ High Cr6+

High Temperature Shift Chromium (VI) Issues

High Cr6+ Low Cr6+

Boiling water test Water soak test

Low Cr6+ : typically < 10 ppmw

High Temperature Shift Sulfur Removal Issue

Sulfur source • residual sulfate from metal salts used in

catalyst manufacture Sulfur problem during initial reduction

• liberate H2S during initial catalyst reduction • poison for LTS catalyst or PSA absorbent

vent exit gas to prevent poisoning if not, consumes up to 1 volume LTS catalyst

per 20 volumes HTS catalyst • duration depends on catalyst sulfate level • prolongs commissioning

High Temperature Shift Sulfur Removal Issue

Sulfur level • depends on manufacturing route

sulfate route (older) ~ 5000 ppmw nitrate route (newer) ~ 200 ppmw

Effect of de-sulfiding on reduction time • duration depends on catalyst type

nitrate route: complete in ~4 hours after process gas

sulphate route: hold for 5 - 10 hours extra

Improvements in High Temperature Shift Catalysts

The high temperature shift duty HTS catalyst characteristics Typical HTS operational problems Improved catalysts and loading

regimes Summary

HTS Operational Problems Catalyst Start Up

Exotherm on steam addition • Temperature “spike” sometimes observed

new HTS catalyst; all vendors • often 100 oC (180 oF) and up to 250oC (450oF)

Root cause analysis

• not understood for many years • correlated with long hold on N2 flow at >> 200 oC • catalyst surface becomes “super dry” • steam re-hydrates surface (heat of hydration)

1st Steam Introduced

0 20 40 60 80 100

250

300

350

400

450

500

600

700

800

Time, minutes

Tem

pera

ture

(°C

)

Tem

pera

ture

(°F)

Inlet

Top

Mid

Bot

Exotherm on Steam New HTS Catalyst

Large European Plant

HTS Operational Problems Catalyst Start Up

Exothermic Rehydration Case Study • VSG-F101 Series installed • subsequent performance unaffected • demonstrates good catalyst thermal

stability Rehydration phenomenon

• avoid by controlling drying conditions during start-up

HTS Operational Problems Catalyst Start Up

Exotherm due to H2 ingress • passing valve allowed H2 entry

before reduction started on hold at 200+ oC

• new VSG-F101 Series installed • significant exotherm • subsequent performance unaffected

on line > 4 years • demonstrates good catalyst thermal

stability

HTS Operational Problems Upstream Boiler Leaks

Boiler leaks • relatively common • more likely at high plant rates

Effects • possible catastrophic catalyst failure due

to thermal shock • pressure drop increase due to

boiler solids fouling of the catalyst catalyst breakage (droplet

impingement)

HTS Operational Problems Upstream Boiler Leaks

Boiler leak case study - background • large new Syngas plant • Vulcan Series catalysts throughout

including VSG-F101 • observed increase in HTS pressure drop • data consistency check indicated showed

high steam ratio in the shift section • boiler leak suspected

HTS Operational Problems Upstream Boiler Leaks

Boiler leak case study - actions/outcome • catalyst inspected • boiler leak confirmed • catalyst skimmed • plant restarted at 100% rate with 40%

less HTS catalyst space velocity increased to 9000 h-1

• catalyst still achieved maximum conversion

HTS Operational Problems Unplanned Catalyst Oxidation

Exothermic Catalyst Oxidation • activated (reduced) catalysts

reacts with air rapidly and exothermically catalyst oxidizes with possible thermal

damage

Case Study from a large syngas plant • air machine delivery valve failed • huge HTS catalyst temperatures increase

middle = 635oC (1175oF) and exit = 540oC (1100oF)

• temperatures stayed high ~30 minutes

HTS Operational Problems Unplanned Catalyst Oxidation

Catalyst Oxidation Case Study - outcomes • catalyst activity impaired

flatter reaction profile CO slip has increased from < 3% to

>4% • VSG-F101 remains operable

capable of an acceptable performance until a convenient change is planned

despite significant over-temperature

Improvements in High Temperature Shift Catalysts

The high temperature shift duty HTS catalyst characteristics Typical HTS operational problems Improved catalysts

VSG-F101 Series

Summary

VSG-F101 Series Step change improvement for HTS

Launched almost three years ago Reformulated catalyst

• similar bulk composition to previous grades • modified iron oxide pore structure

patented use of acicular iron oxide Increased activity by 20%

• reduced diffusion limitation Increased in-service strength +100%

VSG-F101 Series Properties

Composition Fe Ni Cu (+ Al2O3 )

Form VSG-F101 9 mm (dia) x 5 mm pellets VSG-F101 5 mm (dia) x 8 mm spheres

Charged bulk density 0.8-1.1 kg/l (50-69 lb /ft3)

VSG-F101 Series Improved HTS Catalyst

Structural promoter • Improves strength

better able to withstand plant upsets such as boiler leaks

higher strength through life • Modifies pore structure

wider pore distribution allows easier diffusion through wide pores

to high surface area active sites in small pores

increases activity

Structural promoter

Micrograph showing catalyst enlarged x140,000

VSG-F101 Series Modified Microstructure

Rad

ial C

rush

Str

engt

h (K

g/cm

)

VSG-F101 Competitor A Competitor B Competitor C 0

2

4

6

8

10

12 VSG-F101 Series Reduced Strength

Crush strength after 2

weeks operation

Months on Line 0

0

10

20

30

40

50

10 20 30

Start of Leak

Comp. A

VSG-F101

Limit

VSG-F101 Comparison Boiler Leak

Months in Operation

Cat

alys

t Act

ivity

2

3

4

5

6

7

8

9

10 20 30 40 0

Design for VSG-F101

Expected for VSG-F101

Measured Activity

VSG-F101 in a Large Syngas Plant in China

VSG-F101 Large Size for Low Pressure Drop

VSG-F101DG • 14 mm dia x 5 mm height domed pellets • pressure drop is 40 % lower than VSG-

F101 • larger pellet => stronger

better resistance to plant upsets • activity ~90 % that of VSG-F101 at 360 oC

THUS exceeds that of VSG-F101

Improvements in High Temperature Shift Catalysts

The high temperature shift duty HTS catalyst characteristics Typical HTS operational problems Improved catalysts and loading regimes Summary

Summary

Fundamentals of HTS Catalysis HTS catalysts have improved

• VULCAN Series VSG-F101 Operational issues still affect HTS

catalysts • start up exotherms; boiler leaks;

catalyst breakage; reoxidation Active and robust VSG-F101 Series