by: Gerard B. Hawkins

Managing Director, CEO

Water-Gas-Shift Reactor Loading & Unloading

Considerations

Fixed Beds: Catalyst Discharge Issues to consider

• reduced catalysts: self heating HTS, MTS, LTS and methanation

• inert discharge or in situ oxidation/passivation

• in situ oxidation with O2 or passivation with H2O

• carbon contamination: self heating/pyrophoric possible for HDS and ZnO

• inert or wet discharge if necessary

• agglomerated catalysts cause usually fouling or wetting

• physical breakage may be required

Catalyst history affects procedure

Fixed Beds: Catalyst Discharge

Preparation • select discharge method • cool and purge reactor • oxidize or passivate catalyst (if

required) • water can be a weak oxidant and/or

inerting medium beware of evolved H2 hazard

• metal + H2O => metal oxide + H2 water fills catalyst pores

• slows rate of O2 diffusion

Fixed Beds: Catalyst Discharge In situ oxidation with air

• purge all combustibles from process • cool with steam or nitrogen

at 600-1000 h-1 space velocity to 204 oC (400 oF) for HTS and 177 oC (350

oF) for LTS • meter 1% air into bed and monitor

exotherm 31 oC (55 oF)/% air for HTS; 14 oC (25

oF)/% air for LTS or MTS • Once exotherm stable, slowly increase

air up to 3 % initially and monitor exotherm hold peak temperature below hardware

limits

Fixed Beds: Catalyst Discharge In situ oxidation with air

(cont.) • continue to increase air level

keep below vessel or piping temperature limitations

• oxidation is complete when exotherm has passed through bed air level is 7-10%

• replace steam or nitrogen flow with air flow

• cool catalyst in air to discharge temperature below 38 oC (110 oF) for dry methods below 93 oC (200 oF) for wet method

Fixed Beds: Catalyst Discharge • Top discharge by

vacuum – Man enters from top

under vessel entry permit

– Vacuum hose is 4 - 6” dia (10 - 15 cm)

– Support material > 1” dia (2.5 cm) has to be removed by hand

Man works evenly across and down bed

For inert discharge, N2 is cooled and recycled

Fixed Beds: Catalyst Discharge Bottom discharge - dry

• most common method • requires a proper dump chute and

containers (bins or drums) for discharged catalyst

• keep positive N2 pressure for inert discharge catalyst bins must be inerted

• water hose available in case of heat generation wet catalyst during discharge if required

Fixed Beds: Catalyst Discharge

Bottom discharge - wet • less common • cool catalyst below 93 oC (200 oF) • ensure suitable isolations for H2O • fill vessel with water • dump vessel contents through bottom

drain valve • remove catalyst through bottom manway

discharge of wet catalyst is very messy water may not completely oxidise the catalyst

Fixed Beds: Catalyst Handling & Loading

Vessel inspection • inspect vessel for stress damage • thermocouples: check condition if

present document T/C locations relative to fixed

point • eg inlet flange or tangent line

• support grids: check condition if present correct any damaged clips, grid blinding, etc

• reactor clean and dry

Fixed Beds: Catalyst Handling & Loading

Pre-loading checks • ensure vessel is free from rubbish • bottom manway door and spider in place • inspect reclaimed support/hold down

materials remove broken or extraneous contaminants

• inspect new catalyst type and condition

• inspect new support/hold down materials type and condition ceramic versus alumina

Fixed Beds: Catalyst Handling & Loading

Pre-loading checks (cont.) • appropriate personal protection available

- and is used - inside and outside vessel eg dust masks

• for vessel entry air tests breathing air and/or air movers usual stringent vessel entry precautions boards to support worker inside

• minimises catalyst damage

Fixed Beds: Catalyst Handling & Loading

Loading methods • manual

most common by far • pneumatic

specialised techniques (eg from Technivac) not considered further

• dense loading specialised technique (eg from Petroval

DENSICATTM) not considered further

Fixed Beds: Typical Loading

6” (15cm) of 1”- 2” balls (25 - 50mm)

Catalyst/ absorbent

6” (15cm) of 0.5” balls (13mm)

4” (10cm) of 0.25”- 0.5” balls

(6 - 13mm)

6” (15cm) of 1”balls (25mm)

1”- 2” balls (25 - 50mm)

Support grid

Spider

Fixed Beds: Manual Loading

• Key points – use hopper or

supersack with attached sock

– move sock to ensure uniform distribution

– catalyst freefall • maximum 3 ft (1m) • minimum 1 ft (0.3 m)

– try to keep sock full – cut sock as vessel

fills

Fixed Beds: Manual Loading

Charging tube - fixed position

More smaller particles: higher pressure drop

Support Grid Catalyst Support

More larger particles: lower pressure drop

Distribution issue