Secondary Reforming Burners
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Transcript of Secondary Reforming Burners
History Design Operational Improvements Fabrication Delivery Installation
Contents
Ring burners have been around for a long time, in fact nearly 25 years
Prior to this shower head types have been used Straight pipes with simple mixers can be used
providing long necks exist
In the Secondary Reformer process gas is mixed with air
This provides the nitrogen necessary for ammonia synthesis
The reaction can be described as taking place in two parts: ◦ combustion of hydrogen ◦ reforming of methane
Combustion of hydrogen provides the heat required to achieve a very low exit methane concentration
CH4 + 2CO = CO2 + 2H2O
2H2 + O2 = 2H2O
Exothermic - gives out heat
Flame 2500oC mixed gas 1500oC
Gas feed very hot > 630oC
Gas feed contains hydrogen
Gas ignites automatically
Autoignition >615oC
No need for spark or pilot
Must maintain gas above 615oC
Only 20% of flammable gas is burnt
Excess methane is left
Remaining methane reforms with steam
Oxygen increases temperature
Reverse of normal combustion
After combustion gas at 1500oC
Hot enough to react in gas volume
Gas will cool to 1100oC - 1200oC
Substantial amount of methane reacts
Steam reforming CH4 + H2O = 3H2 + CO
Endothermic - cools down gas
Water gas shift
CO + H2O = CO2 + H2
Slightly exothermic
Catalyst completes reaction to 950oC
Exit methane content approx 0.5% (dry)
Catalyst is Ni on ceramic
Can be ringed or shaped catalyst as for Primary Reformer
Bit of black art, originally Now backed up by some science Process calculations are carried out for flows in gas
side, air side ensure pressure drops not too large CFD has improved our designs immensely, but is
expensive Mixing and proportions are important All designs are similar but not Identical Velocity exit nozzles is important
780°C
450°C
2500°C
? ~1500°C
1100-1200°C
950°C
? ~1500°C
1100-1200°C
1300°C
Pipe design
Shower Head
TI
TITI
Gas from Primary
Gas to Process
Water inlet
Water inlet
Steam vents
Oxygen inlet
Catalyst
Arch
Waterjackets
Burner gun
Refractory
Distributor
All materials are Incoloy 800 (UNS 8810) (Alloy 600 is not stronger or more temp resistant at these operating temps, only more expensive)
Oxidation resistance is very important Special Heat treatment ◦ To ensure oxidation resistance is maintained ◦ Improve the grain structure, improve creep resistance
Some components are tightly bent, grains become flattened and weaker. Typically around manifolds and feeders, we correct this.
Equipment needs to be a good fit to prevent damage
Top hung in the unit, hence why central pipe is thick
Site welding is carried out by customer, we provide weld procedure,Customer provides weld procedure qualification, Consumables
Better Mixing Reduced Methane Slip 0.5-0.3% or better Improved Catalyst Performance better bed usage
Bending of manifolds is difficult, require skill Welding needs to be well controlled, distortion is an
issue Flow Straighter is Laser cut, SS cannot be flame cut,
plasma cutting needed; this distorts the plates (end up looking like pringles
Not the norm around the world, however this has become the norm in FSU
Sufficient detail on the drawing to allow competent operator to install
Welded on site, the unit and lowered in. Take care with dimensions, try to obtain “As Built”
drawings
Proposal 0.2Place order 0.1Process Design 1Mechanical Design 1Client Approval 1Fabrication 9Delivery 2
Weeks 14
Weeks
We try to achieve 10 weeks ! Raw materials are on 6 weeks delivery !!!!!!
Delivery usual methods Sea/Road, Air is expensive
Weight approx 1.2 te Packaging:- crated and sealed Need to allow 2 weeks In Europe/FSU ROW 6 weeks Shut downs can be decided in 14 weeks !