Steam Reforming - Types of Reformer Design

Types of Reformer Design

Gerard B. Hawkins Managing Director

GBH Enterprises Ltd.

Four main types • Pre reformers • Primary reformers ◦ Main different designs

• Secondary reformers • Compact reformers

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• Need ◦ To contain the catalyst - use tubes ◦ High heat transfer area - lots of narrow ID tubes ◦ To supply heat - combustion of fuel ◦ To distribute feed - headers ◦ To collect effluent - headers ◦ To supply fuel/combustion air - headers & duct ◦ To contain combustion gases - casing ◦ To recover heat - flue gas duct and coils



• Three main types considered ◦ Top Fired ◦ Foster Wheeler Terrace Wall ◦ Side Fired

• Many other types ◦ Not considered ◦ Not encountered frequently ◦ Same principles still apply



Top Bottom Side Wall

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Tube Support

Pigtail

Burner

Tube

Coffins

Exit Header


Transfer Line

Risers

Tubes WWW.GBHENTERPRISES.COM


Nearly all heat transfer is by radiation Radiation from the flue gas to

the tubes Little direct radiation from

refractory to tube Refractory acts as a reflector Radiation from flame to tube at

tube top



Top Fired Temperature Profiles

800900

1000110012001300140015001600

0 20 40 60

Distance Down Tube (ft)

Proc

ess

and

Out

side

Tu

be W

all

Tem

pera

ture

(°F)

1400

1600

1800

2000

2200

2400

2600

2800

Flue

gas

Tem

pera

ture

(°

F)

Outside Tube WallTemperatureProcess GasTemperatureFluegas Temperature



• The key advantages of this design are • Small catalyst volume • A relative small number of burners • Combustion air preheat is simple to install

• The key disadvantages of this design are ◦ High heat fluxes at the top of the tubes can lead to carbon

formation and hence to hot bands • The heat flux down the tube can not be varied • Burner control is coarse due to the low number of burners

used on top fired reformers • A temperature pinch between the flue gas and process gas at

the exit of the tubes



Air

BFW

MP Steam

HP Steam

Fuel

NG Feed



Upper Firing Level

Lower Firing Level

Convection Section

Fluegas Fans

Cell 1 Cell 2

Tubes





• Nearly all heat transfer is by radiation from flames and refractory ◦ Major portion is from

refractory ◦ Some from flame ◦ Some from flue gas

• Heat is transferred from flame to the walls ◦ By convection/radiation

Radiative heat flows

Convection



Foster Wheeler Temperature Profiles

800

1000

1200

1400

1600

1800

2000

0 20 40 60


Tem

pera

ture

(°F)

Flue

gas

Tem

pera

ture

(°

F)




• The key advantages of this design are, ◦ Ability to alter the firing between the two levels to either, Reduce methane slip, Or increase the flue gas temperature and hence raise more

steam, ◦ A low heat flux which means carbon formation should not be

an issue. • The key disadvantages of this design are, ◦ Relatively high catalyst volume, ◦ The feed and fuel gases must be balanced between the two

cells, ◦ A large number of burners.



Convection section is placed above transfer duct

Elevated - makes modifications difficult

Long tubes in coil Multiple fans in some cases Can include auxiliary burners



Pigtail

Tube

Burner

Outlet Collector

Peephole

Burner

Burner Burner

Fluegas Extraction



Tubes

Peephole

Burners



Staggered

Single Lane



• Nearly all heat transfer is by radiation from flames and refractory ◦ Major portion is from

refractory ◦ Some from the flames - less

than for Foster Wheeler • Some from flue gas • Heat is transferred from flame

to the walls ◦ By convection/radiation

Convection

Radiative heat flows



Side Fired Temperature Profiles

800900

10001100120013001400150016001700

0 10 20 30 40


Proc

ess

and

Out

side

Tu

be W

all

Tem

pera

ture

(°F)

140015001600170018001900200021002200

Flue

gas

Tem

pera

ture

(°

F)




• The key advantages of this design are, ◦ Ability to alter the firing between the burner levels to either, Reduce methane slip, Or increase the flue gas temperature and hence raise more

steam, ◦ A low heat flux which means carbon formation should not be

an issue. • The key disadvantages of this design are, ◦ Relatively high catalyst volume, ◦ The feed and fuel gases must be balanced between the two

cells, ◦ A large number of burners.





Issues • Variation of tube wall temperature • Tubes are at different distances from burners • Leads to high methane slip • Variability of tube life







• Most of these reformers are ◦ Upfired ◦ Upflow ◦ Therefore same as a top fired

reformer • Small plant capacities • Always have uneven heat flux and

therefore un-even temperatures • One side hotter than the other



Offered by • Howmar ◦ Now designing Top Fired furnaces

• Howe Baker ◦ Now designing Top Fired furnaces

• Chemico





• Use low grade heat from flue gas duct to preheat air

• Maximize efficiency as stack temperature is reduced

• Minimizes fuel used • No preheating in primary of

the combustion air • Must ensure symmetry ◦ Prevents mal-distribution



Burner Tube Feed Header



Burner Tube WWW.GBHENTERPRISES.COM










Burner Tube Fuel Header WWW.GBHENTERPRISES.COM


Burner Tube







Main types include • Gas Heated Reformer (GHR) • Advanced Gas Heat Reformer (AGHR) • Enhanced Heat Transfer Reformer (EHTR) • KRES



Aim is to • Minimize plot area ◦ Eliminate large fired box ◦ Eliminate convection section

• Maximise heat integration • Eliminate HP steam system



• Developed for ammonia process - LCA • Early 1980’s - Paper exercise • Mid 1980's - Sidestream unit at Billingham • Mid 1980's - LCA design developed • Late 1980's - ICI Severnside plants start up • 1991 - BHPP LCM plant designed • 1994 - BHPP plant start up • 1998 - AGHR Start Up • 1998 - MCC Start Up



Purifier

Saturator GHR Secondary

Converter

Preheater

Purge to fuel

Topping Column

Refining Column

Process condensate

water

Fusel oil

Natural gas

Oxygen Steam

Refined methanol

Purge

Crude methanol



Steam

Secondary Reformer

Steam + Gas

Air / Oxygen

GHR



SecondaryReformer

GHR

Syngas

Gas/steam425`C

701`C

975`C

515`C

742`C

21,000 Nm3/Hr

Oxygen30`C

1200`C

2,590 Nm3/Hr

43.7 Barg 39.2 Barg

38.6 Barg

37.9 Barg

22.0% Methane

16.6% Methane

0.4% Methane

40.6 Barg



• Shellside heat transfer usually poor • Minimize tube count with expensive alloys • Tubes are externally finned • Designed as double tubes

• Sheath tube • Produces much smaller tube bundle • Allows scale up to higher capacities

Catalyst tube Fins Double tube

Hot shellside gas WWW.GBHENTERPRISES.COM


Gas & Steam

Scabbard Tube Catalyst

Bayonet Tube

Support Grid End Cap

Hot Reacted Gas



Gas/Steam Hot gas Twin

tubesheets

Refractory

Syngas





• GHR operates in extremely corrosive duty • Metal dusting - catastrophic carburization • Need for materials research • Suitable high temperature alloys identified • Many years of operation in LCA plants • Also confirmed in Methanol plant



• Retain • Series reforming scheme • Shellside heat transfer enhancement • Mechanical & process design methods

• Change to • Non bayonet design • Hot end tubesheet • Sliding seal system



• Novel seal system • Prevents leakage from tubeside to shellside • Not sensitive to wear of sliding surfaces • Allows independent tube expansion • Proven in full scale pilot plant tests



• Easier to replace tubes • Easier to load catalyst • Capacity of up to 6,500 mtpd in single shell ◦ Would need 2 conventional primaries





• APCI / KTI • EHTR

• Kellogg • KRES

• Uhde • CAR

• GIAP • Tandem

• Johnston Matthey • GHR



Feed & Steam In

To Heat Recovery

Catalyst Tube

Perforated Distributor

Reformer Effluent

Cylindrical Distributor



Date post:	02-Nov-2014
Category:	Technology
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Steam Reforming - Types of Reformer Design

Technology