Burner Design, Operation and Maintenance on Ammonia Plants

Burner Design, Operation and Maintenance on Ammonia Plants

Brief History Reformer Burner Types/Design Types of Reformers Combustion Characteristics Excess Air/Heater Efficiency Maintenance, Good Practice Low Nox Equipment Summary

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Usage of Fuels on Ammonia Plants Worldwide

0

50

100

150

200

250

300

350

400

450

Total NoPlants

Natural Gas Heavy FuelOil

Naphtha Syngas Others

Fuels

Num

ber

of O

pera

ting

Plan

ts


CURRENT LEGISLATIONLIMITS

Country Start Year Heat releaseFurnace Capacity

NOx CO (ppm) Particulatesmg/Nm3

Gas Oil Gas Oil Gas OilFrance 1998 >170 MMBtuh 171 219 - - 5 50UK 1998 Any 146 219 115

1999 Any 97 171 80Germany 1996 <170 MMBtuh 122 80

219 85 50<340 MMBtuh 97 50 5

TA Luft >170:<1020mmBtuh

171 219 25 87 5-100 50

97 171 25 87 5-100 50Market demand All 39 73 5 50

171 5 50EasternEurope

As Germany

Italy 1992 >170:<1020mmBtuh

171 219 5 50

USA - All 30-100


Brief History Burner design Burner Types Types of Reformers Combustion Characteristics Heater Efficiency Maintenance, Good Practice Low Nox Equipment Summary


◦ Historically trial and error

◦ Empirical methods now backed up with the following sciences Chemical engineering Process engineering Thermodynamics Materials engineering

◦ A good understanding of the above creates good combustion


◦ Computational fluid Dynamic’s (CFD) is playing a strong role. Good but be cautious

◦ Can be difficult to predict upsets Good for replacing flow modelling Model the Burner and the Furnace box to

ensure best possible results

◦ Becoming an essential tool for waste incineration predictions


Burner testing in the manufacturer’s facility should always be considered

Confirms burner performance Turndown CO,CO2,NOX Etc Always use the specified fuels

that are to be used in service Highlights flame envelope and

lift off limits, pilot/light up issues.

Air flow distribution


Brief History Burner design Types of Reformers Reformer Burner Types/Design Combustion Characteristics Heater Efficiency Maintenance, Good Practice Low Nox Equipment Summary


Side Fired

Top Fired

Terraced wall


Natural Draft Forced Draft Premix Post Mix Low Nox ◦ Fluegas Recirculation ◦ Staged Air ◦ Staged fuel

Single fuel/Dual fuel



Gas Nozzle

Primary Air

Primary Air

Pre-Mix Burners

Venturi

Primary Fuel

• Fuel & air mixed before combustion zone

• Fuel pressure drop occurs in the nozzle.




Premix

Gas

Burner


Nozzle Mix Gas Burner Included

Angle

Burner Block

Burner Throat

Port Circle Heater Refractory

Flame Holder

Pilot Gas

Air

Fuel Connection

FUE

L


Nozzle

Mix Gas

Burner

Nozzle

Mix Gas

Burner

Top or Bottom Fired


Nozzle

Mix Gas

Burner

Side fired




Nozzle Mixing Gas Burner Advantages

• No possibility of flashback

• To some extent, the ability to burn a wide variety of fuels with differing heating values.

• A high turndown ratio


Brief History Reformer Burner Types/Design Types of Reformers Combustion Characteristics Heater Efficiency Maintenance, Good Practice Low Nox Equipment Summary


Increasing excess air

• reduces flame length • reduces particulates • increases NOx to a peak, further introduction of air leads

to a reduction

• Increasing liberation • increases flame length


• Increasing fuel viscosity

• increases flame length • increases particulates • reduces NOx levels

• Increasing combustion air temperature • reduces particulates • increases NOx levels






Draught Inches WG-13

-27-41

-55

Top firebox

Bottom Firebox

FD Section

Atmosphere

AfterConvection

After damper

After ID Fan

Atmosphere

1327

4155

83


x100output Gross

output UsefulEfficiency

=

Heater Efficiency






Burners can be maintained on or off line ◦ On line less popular due to safety concerns, guns

can be with drawn ◦ basic tip changes can be carried out ◦ potential to change burner settings


◦ Off line during shutdowns (every 3-4 years)

◦ Relatively easy to perform Need for access

◦ Important to maintain settings tile to gun position tip port dimensions surface finish of holes centricity of gun condition of tile and security of fixings condition of metallurgy (oxidation)








Check Burner gas Pressures ◦ at the burners, not the just the rail

pressure Check Combustion air pressures ◦ All to often the system is not balanced

correctly For oil firing ◦ it is very important atomising steam is dry

and at the correct temperature




◦ Currently being fitted on new plants ◦ More difficult to control ◦ The very nature of low Nox burner designs requires

the flames to be produced in a much slower manner ◦ Even more sensitive to dimensional changes during

maintenance, burner’s tend to be more complex ◦ Flames tend to be less well defined, with large

whispery edges


Types ◦ Staged Air ◦ Staged Fuel

◦ Flue Gas Recirculation

Integral with the burner external to the burner

◦ Combination of all above




Good Combustion, this can only be achieved if the following is considered.

Attention to detail ◦ Good maintenance ◦ Good operation ◦ Good design

Partnership between:- Operation, Maintenance and Design.


◦ You've carefully thought out all the angles ◦ You've done it a thousand times

◦ It comes naturally to you

◦ You know what you're doing, its what you've

been trained to do your whole life ◦ Nothing could possibly go wrong, right ?


Think Again !


Technology

Burner Design, Operation and Maintenance on Ammonia Plants