Steam Reforming - Catalyst Loading

Gerard B. Hawkins Managing Director

The aim of this presentation is to • Give an understanding of ◦ Best practices ◦ Sock Loading ◦ Unidense ◦ Pressure Drop Measurement ◦ Common Problems

Use approved drum handling techniques Do not roll drums Do not lift on forks of fork lift truck Do not stack more than 4 high - even on

pallets Protect from rain and standing water Keep lids on Do not expose to temperature extremes

Before loading • Inspect vessel for stress damage • Check conditions of thermocouples

– Document their location with respect to inlet flange or tangent line

• Check support balls for breakage or extraneous materials

• Check support grids for condition (e.g., damaged clips; grid binding)

• During charging – Use appropriate personnel protection Dust masks Gloves Full body coverage Fresh air in vessels

• Support workers in reactors with boards • Snow shoes

During charging – Use hopper or supersack with attached sock

– Ensure uniform distribution by moving sock

– Maximum catalyst freefall 3ft (1m)

– Minimum catalyst freefall 1ft (.3m)

– Helps ensure dense loading

Aim is to achieve • Same flow through each tube ◦ No hot tubes

• No bridging ◦ No hot spots

• Ultimately ◦ Minimize methane slip ◦ Extends tube life

Inspection • Check tubes for defects using LOTISTM or eddy

current etc

• Internal surfaces - Look smooth

• Catalyst support grids are in place

• Inlet and exit pigtails are not blocked

• Procedure is ◦ Only have one type of catalyst on

the steam reformer at any one time ◦ Ensure sock “rope” is longer than

catalyst tube ◦ Anchor free and of rope, or fit object

• to prevent rope falling into tube ◦ One end sealed for attachment of

lowering rope ◦ Other end folded over - 10cm (4”)

flap ◦ Calculate weight per sock to give

whole number of socks per tube

• Sock OD should be 20mm (3/4”) smaller than tube ID

• Filled sock length should be around 150cm (5’)

• Socks material is canvas, polythene or similar

• Fill socks with same known weight

• Label socks for different types of catalyst

Filling Tubes Folding Over Attaching Rope

Jerking Rope Topping Up Checking Outage

Compressed air

Inletpressure

Handvalve

Orificeplate

Catalystpressuredrop

Cam and leverto expand bung

Cam and leverto expand bung

Guidering

Catalysttube

Developed by Hydro Agri of Norway Proprietary technique available through a select number of

licensees Widely practiced - more than 260 steam reformer charges

have been loaded using this technique Leads to “denser” packing

– less pd variation more uniform gas flows

– easier procedure shorter loading time (70%)

– slightly higher pd effect on throughput - marginal

Outlet pigtail

Brushes

Catalyst tube

Catalyst drum

Charging hopper

Inlet pigtail

Move rope upwards

Aim to pack catalyst to uniform voidage Measure pd

– Not outage in tube at any one time – Not weight per tube – Not catalyst density – After 50% – After full loading

Use defined and consistent procedure throughout

Fixed flow of air (choked flow through orifice)

Mass flowrate through orifice function of ◦ upstream pressure ◦ orifice diameter (known) ◦ temperature (known)

Downstream pressure is measure of pd

• For air, the critical value of P2 is around 50% of P1

• If flow is sonic, then mass flow is constant • Resistance to flow downstream (pd) can be

read now as P2 value

P1 P2

Orifice

Flow must be sonic to obtain meaningful results ◦ requires a minimum upstream/downstream

pressure ratio ◦ check upstream pressure adequate

If using a shared air supply, monitor pressure carefully - other users can lead to a drop in supply pressure.

PD rig

Inlet pigtail

Exit pigtail

4a. Exit pigtail

Empty tube

PD rig

4b. Catalyst

catalyst

PD rig

4c. Inlet pigtail

catalyst

If too high then – suck out catalyst and recharge

If too low then – Vibrate tube – Use a soft faced hammer – Top up if outage too great

Voids Stacking

Voids

Broken Pellet

Voids Voids

-20 -15 -10 -5 0 5 10 15 20-15

-10

-5

0

5

10

15

-40-30-20-10010203040

Pressure Drop Variation (%)

Flow

Var

iatio

n (%

)

Tube

Tem

pera

ture

Var

iatio

n (°

C)

• If loading is poor • variety of flows in tubes

• Each tube has different exit temperature ◦ Each tube has a close approach ◦ Mixture of all tubes far from equilibrium ◦ Methane slip not linear with temperature ◦ Methane slip higher than it should be ◦ Tube temperature distribution ◦ Some tubes will be hot

• Therefore fail sooner ◦ Operational costs - High Slip ◦ Maintenance costs - Failed tubes

Mixed Gas Exit

Reformer

872 1602

9 16

3.9

Process Gas Exit (°C) Temp (°F)

Methane/Steam (°C) Approach (°F)

Methane Slip (% dry) Max twt (°C) (°F)

Well Balance

870 1598

2 3

3.6

891 1636

Poorly Balance

834 - 992 1533 - 1692

1 - 3 1 - 5

1.6 - 6.5

860 - 930 1580 - 1706

Charging tube

high pressure drop

Support Grid Catalyst Support

More larger particles low pressure drop

• This means that there is ◦ A high voidage at the walls ◦ A low voidage in the center

• This will cause flow mal-distribution ◦ More flow at walls ◦ Less in the centre

• Will cause a shortened life

Giraffe Necking

Tiger Tailing

“Bridging”

Settling

Not enough catalyst, or overcompaction and breakage

Outage (Pressure Drop)

Amount of vibration or hammering

Overcompacted

Correctly Settled

Two methods: – Vacuum from top Most desirable form informational standpoint Costly Difficult if catalyst pyrophoric

– Bottom dump Faster Cheaper

Nickel containing catalyst – Potential for nickel carbonyl – Formed by CO reacting with Ni – Stable below 200oC (390oF)

Use a device as illustrated below

15cms Clip

Mesh

Hose

Vacuum System