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 Folding Over Attaching Rope Filling Tubes Jerking Rope Topping Up Checking Outage Compressed air Hand valve Inlet pressure Orifice plate Catalyst pressure drop Cam and lever to expand bung Guide ring Catalyst tube Cam and lever to expand bung  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  Catalyst drum Move rope upwards Charging hopper Inlet pigtail Catalyst tube Brushes Outlet pigtail   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 P1 P2 Orifice • • • 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  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 PD rig PD rig Inlet pigtail Empty tube catalyst catalyst Exit pigtail 4a. Exit pigtail 4b. Catalyst 4c. Inlet pigtail  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 Voids Voids Broken Pellet 40 10 30 20 5 10 0 0 -10 -5 -20 -10 -15 -30 -20 -15 -10 -5 0 5 10 Pressure Drop Variation (%) 15 20 -40 Tube Temperature Variation (°C) Flow Variation (%) 15 • 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 Well Balance Poorly Balance Mixed Gas Exit Reformer Process Gas Exit Temp (°C) (°F) 870 1598 834 - 992 1533 - 1692 872 1602 Methane/Steam Approach (°C) (°F) 2 3 1-3 1-5 9 16 3.6 1.6 - 6.5 3.9 891 1636 860 - 930 1580 - 1706 Methane Slip Max twt (% dry) (°C) (°F) Charging tube More larger particles low pressure drop high pressure drop Catalyst Support Support Grid • 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 “Bridging” Tiger Tailing Giraffe Necking Not enough catalyst, or overcompaction and breakage Settling Overcompacted Outage (Pressure Drop) Correctly Settled Amount of vibration or hammering  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 Hose Mesh Vacuum System