combustion issues in low-carbon fossil power plants for

Combustion issues in low-carbon fossil power

plants for the 21st Century

Robin Irons

E.ON Technologies Group, Technical Head, Zero Emission Power Plant



What is ‘acceptable’

combustion?



Combustion

Fuel

Comburent

Heat

Acceptability

Emissions

Materials

Flexibility

The Fuel Diet

UK Coal Market 2012

Coal Source Mte Domestic total

UK Deep* 6.2

UK Surface 10.2 16.8

UK Other 0.4

Import Total

Russia 18.3

Colombia 11.9

USA 10.5

Australia 2.3 44.8

EU (includes trans-

shipment)

0.7

RSA 0.6

Canada 0.1

Other 0.4

Source UK Coal website

* NB: data includes Daw Mill – Closed after fire in early 2013

UK Coal Market 2012

Coal Source Mte Domestic total

UK Deep* 6.2

UK Surface 10.2 16.8

UK Other 0.4

Import Total

Russia 18.3

Colombia 11.9

USA 10.5

Australia 2.3 44.8

EU (includes trans-

shipment)

0.7

RSA 0.6

Canada 0.1

Other 0.4

Source UK Coal website

* NB: data includes Daw Mill – Closed after fire in early 2013

The UK Coal basket is as broad as ever and fuel of

choice varies rapidly with regulation, politics and

economics

For Today’s power mix see

‘GridCarbon’ App

24 Feb data

13300MW Coal

7300MW Nuclear

5500MW Wind

3400MW Gas

2000MW French Interconector

1000MW Dutch Intrconector

1000MW Hydro

560MW Other

New Biomass plants – E.ON’s Blackburn Meadows

30MWe

CHP

Waste Wood

Fluid Bed Combustion

NE of Sheffield

Biomass-Cofiring in Existing Plants

Variables Include

Base Fuel (coal) and variability

Biomass %

Biomass Type (and variability)

Economic incentives

Boiler Design

Emissions Regulations

Emission Control technologies

Source, Alstom Website

But natural gas is just natural gas, isn’t it…….?

12

E.ON New Build & Technology

EASEE-Gas Gas Quality Specifications

42

44

46

48

50

52

54

56

Dk UK NL(H) It Be(H) F (H) Sp De (H)

Wo

bb

e I

nd

ex (

Gro

ss,

MJ

/m3)

National Max National Min Typical

Hgas Max (EN437) Hgas Min (EN437) EASEE Max

EASEE Min

Wobbe Index = GCV/(Specific gravity)0.5


Impact on NOx Emissions

40

50

60

70

80

90

100

46.5 47 47.5 48 48.5 49 49.5 50 50.5

Wobbe Index (Gross, MJ/m3)

NO

x e

mis

sio

ns (

% o

f ta

rget

maxim

um

)

Unit C

Unit D

Unit A

Unit B

Site with 4 GTs of same design

Increasing trend in NOx emissions with fuel Wobbe Index

Impact of fuel quality on NOX emissions varies between the 4 units

14


Potential for Hydrogen

Black line represents EASEE-Gas quality specification

33

35

37

39

41

43

45

47

0.5 0.55 0.6 0.65 0.7 0.75

Relative Density (-)

Calo

rifi

c V

alu

e (

Gro

ss,

MJ/m

³)

Increasing

Inerts

Increasing non-

methane hydrocarbons

Pure Methane

WI = 54MJ/m3

WI = 47MJ/m3

Typical UK

Natural Gas

5% H2

10% H2

15% H2

20% H2

Increasing H2

10% H2 + 6%

Propane

Significant amounts of hydrogen can be accommodated within the EASEE-Gas envelope

This could cause significant issues for gas turbines

15

Flashback and burner damage as seen at an E.ON GT site has been linked to high levels of higher hydrocarbons (C2+)

No longer a major issue for E.ON as flashback prone burners have been replaced by flashback resistant design

There is still potential for flashback on some burners with fuel quality changes, e.g. increasing C2+.


Flashback and Burner Damage

New Areas for Power Plant

Is CCS Relevant to Combustion Issues?

Figure courtesy Vattenfall

Oxyfuel Combustion

Corrosion in Oxyfuel

El Cerrejon Thoresby

Moisture %wt AR 5.8 4.8

Ash %wt AR 8.6 11.8

Volatile %wt AR 34.8 32.3

%wt DAF 40.7 38.7

Fuel ratio (Fixed C:VM) 1.46 1.58

Net CV kJ/kg AR 27,122 27,393

S %wt AR 0.58 1.61

%wt DAF 0.68 1.93

Cl %wt AR 0.02 0.45

%wt DAF 0.02 0.54

N %wt AR 1.42 1.55

%wt DAF 1.66 1.86

AR = As Received - DAF dry, ash-free

CORROSION - AIR

El Cerrejon Air-Fuel

1.00E-14

1.00E-13

1.00E-12

1.00E-11

1.00E-10

1.00E-09

400 450 500 550 600 650 700

Temperature (oC)

95%

ile P

ara

bolic

Rate

(cm

2s

-1)

T22

E1250

TP347HFG

HR3C

CORROSION - Low-S/Low-Cl

El Cerrejon Oxy-Fuel

1.00E-14

1.00E-13

1.00E-12

1.00E-11

1.00E-10

1.00E-09

400 450 500 550 600 650 700

Temperature (oC)

95%

ile P

ara

bolic

Rate

(cm

2s

-1)

T22

T91

E1250

TP347HFG

HR3C

San25

IN740

CORROSION - High-S/High-Cl

Thoresby Oxy-Fuel

1.00E-14

1.00E-13

1.00E-12

1.00E-11

1.00E-10

1.00E-09

400 450 500 550 600 650 700

Temperature (oC)

95%

ile P

ara

bolic

Rate

(cm

2s

-1)

T22

T91

E1250

TP347HFG

HR3C

San25

IN740

OxyCAP UK R-20 ignition chamber

Goals: a) Determine safe levels of O2 in O2/CO2 in primary recycle (PR). b) Mill safety. c) Ignition/combustion fundamentals under oxy-fuel conditions.

Task: ST1-A (P.F. experiments in oxy-combustion)

Methodology: Dust ignition tests under oxy-fuel conditions in 20 L chamber. Peak pressure and dP/dt measurement for positive ignition.

R-20 assembled (left) rated for 50 bar and R-20 bottom half with perforated nozzle (right)

OxyCAP UK R-20 ignition chamber

Example of Pressure ratio (P/R) values vs coal concentration. Positive ignition when P/R >2.5

CO2/H2

separation CO2 to

Storage

IGCC with CO2 Capture

H2 Combustion - Standalone

• Not just an IGCC issue - Possible new energy vector

• Excess Renewable power used for hydrolysis

• Requires GTs or other devices to reconvert to H2

• H2 derived from water, not fossil fuel

• Various scales may be optimal – IC engines, fuel cells, gas turbines – dependent on market drivers

Direct Contact

Cooler (DCC)

Flue Gas

Trim

Cooler

Reflux

Drum

Treated Gas

Cooler

Flue Gas

Blower

Absorber

Reflux

Condenser

CO2 Product

Stripper

Reboiler

Lean/Rich

Exchanger

Rich Solvent

Lean Solvent

Reflux

drum

Water

wash

cooler

Steam supply

Amine Capture

Novel cycles – e.g. NetPower

Source Netpower website

Aspects of the Allam Cycle

Pure O2 – from ASU

Gas

Bulk flow CO2

High Pressure

High Temperature

High inerts (CO2) concentration

High Efficiency

Industrial Emissions Directive

New limits for ‘old’ pollutants

NOx, SOx, Dust (regulatory)

National Ceiling Directive

‘New’ Pollutants

Black Carbon,

PM2.5,

Hg

Reduction Driven by process requirements

NO2, SO2, SO3 (Post combustion carbon capture)

Emissions – new substances and new regulations

Flexibility

Lower load

Emissions maintained across a wider range of loads

Improved control for faster pickup

Interaction with materials

Conclusions

The fundamentals of combustion haven’t changed

The market-place continues to change requiring new innovations as

Fuel composition changes – sourcing/blending/regulation/innovation

Emissions constraints tighten

Operational requirements mean old plants must operate in different ways

New Cycles/configurations come to market.

All offer new RD&D challenges in the field of combustion.

combustion issues in low-carbon fossil power plants for

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