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8/10/2019 Steamreforming Typesofreformerdesign 130924133238 Phpapp02

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Types of Reformer Design

Gerard B. Hawkins

Managing Director

GBH Enterprises Ltd.


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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




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Three main types considered Top Fired

Foster Wheeler Terrace Wall

Side Fired

Many other types Not considered

Not encountered frequently

Same principles still apply




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TopBottomSide

Wall

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Tube Support

Pigtail

Burner

Tube

Coffins

Exit Header



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Transfer Line

Risers

TubesWWW.GBHENTERPRISES.COM



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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 attube top




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Top Fired Temperature Prof iles

800

900

1000

1100

1200

1300

1400

1500

1600

0 20 40 60

Distance Down Tube (ft)

ProcessandOutside

TubeWall

Temperature

(F)

1400

1600

1800

2000

22002400

2600

2800

FluegasTemperature

(F)

Outside Tube Wall

Temperature

Process GasTemperature

Fluegas Temperature




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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




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Air

BFW

MPSteam

HPSteam

Fuel

NG Feed




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Upper Firing Level

Lower Firing Level

Convection Section

Fluegas Fans

Cell 1 Cell 2

Tubes




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GBH E i L d


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radiation from flames and

refractory

Major portion is fromrefractory

Some from flame

Some from flue gas

Heat is transferred fromflame to the walls

By convection/radiation

Radiative

heat flows

Convection



GBH E t i Ltd


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Foster Wheeler Temperature Profiles

800

1000

1200

1400

1600

1800

2000

0 20 40 60

Distance Down Tube (f t)

Temperature

(F)

FluegasTempe

rature

(F)

Outside Tube Wall

TemperatureProcess GasTemperature

Fluegas Temperature



GBH E t i Ltd


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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.



GBH E t i Ltd


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Convection section is placed

above transfer duct

Elevated - makes

modifications difficult Long tubes in coil

Multiple fans in some cases

Can include auxiliary burners



GBH E t i Ltd


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Pigtail

Tube

Burner

Outlet Collector

Peephole

Burner

Burner

Burner

Fluegas Extraction



GBH Enterprises Ltd


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Tubes

Peephole

Burners



GBH Enterprises Ltd


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Staggered

Single Lane



GBH Enterprises Ltd


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radiation from flames and

refractory

Major portion is fromrefractory

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

Radiativeheat flows



GBH Enterprises Ltd


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Side Fired Temperature Profiles

800

900

1000

1100

1200

1300

14001500

1600

1700

0 10 20 30 40

Distance Down Tube (ft )

ProcessandOutside

TubeWall

Temperature(

F)

1400

1500

1600

1700

1800

19002000

2100

2200

FluegasTempera

ture

(F)

Outside Tube WallTemperature

Process GasTemperature

Fluegas Temperature



GBH Enterprises Ltd


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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.



GBH Enterprises Ltd


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GBH Enterprises Ltd


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Issues

Variation of tube wall temperature

Tubes are at different distances from burners Leads to high methane slip

Variability of tube life



GBH Enterprises Ltd


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GBH Enterprises Ltd


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GBH Enterprises Ltd


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Most of these reformers are

Upfired

Upflow

Therefore same as a top firedreformer

Small plant capacities

Always have uneven heat flux and

therefore un-even temperatures One side hotter than the other



GBH Enterprises Ltd


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Offered by

Howmar Now designing Top Fired furnaces

Howe Baker Now designing Top Fired furnaces

Chemico



GBH Enterprises Ltd


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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





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Burner Tube Feed Header





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Burner Tube





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p



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p



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p



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p



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Burner Tube Fuel Header


p



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Burner Tube


p



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Main types include Gas Heated Reformer (GHR)

Advanced Gas Heat Reformer (AGHR)

Enhanced Heat Transfer Reformer (EHTR) KRES




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Aim is to Minimize plot area

Eliminate large fired box

Eliminate convection section

Maximise heat integration

Eliminate HP steam system



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Purifier

Saturator

GHR Secondary

Converter

Preheater

Purge

to fuel

Topping

Column

Refining

Column

Process

condensate

water

Fusel oi l

Natural gas

Oxygen

Steam

Refined

methanol

Purge

Crude methanol




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Steam

Secondary

Reformer

Steam + Gas

Air / Oxygen

GHR




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SecondaryReformer

GHR

Syngas

Gas/steam

425`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




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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




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Gas &

Steam

Scabbard

TubeCatalyst

BayonetTube

Support

GridEnd

Cap

Hot Reacted

Gas




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Gas/SteamHot

gas Twin

tubesheets

Refractory

Syngas




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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




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Retain Series reforming scheme

Shellside heat transfer enhancement

Mechanical & process design methods

Change to Non bayonet design

Hot end tubesheet

Sliding seal system




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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




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Easier to replace tubes

Easier to load catalyst

Capacity of up to 6,500 mtpd in single shell

Would need 2 conventional primaries




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APCI / KTI EHTR

Kellogg KRES

Uhde CAR

GIAP Tandem

Johnston Matthey GHR




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Feed &Steam In

To Heat

Recovery

Catalyst

Tube

Perforated

Distributor

Reformer

Effluent

Cylindrical

Distributor



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