Oxyfuel Research at RWE npower plc. The CRF 2012 Annual Meeting and - - PowerPoint PPT Presentation

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Oxyfuel Research at RWE npower plc. The CRF 2012 Annual Meeting and Combustion Divisional Seminar, 25th April 2012. Gerry Riley and John Smart Presented by Mark Flower RWE npower PAGE 1 Presentation overview Background Highlights from

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Oxyfuel Research at RWE npower plc. The CRF 2012 Annual Meeting and Combustion Divisional Seminar, 25th April 2012. Gerry Riley and John Smart Presented by Mark Flower

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Presentation overview

  • Background
  • Highlights from Test Programmes
  • Oxyfuel UK DTI Project
  • BOM-COM RFCS
  • EcoScrub RFCS project
  • Fuel project (RWE npower project)
  • Oxygen injection project with BOC
  • Summary
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Background: What is oxyfuel?

> Flue gas is recycled and air is replaced by oxygen > The gas inside the boiler becomes almost nitrogen-free and CO2 is then removed.

W

Furnace/Boiler Convective Zone Radiative Zone Coal Coal Mill Primary Nitrogen Oxygen Air Cooler Electro-static Precipitator Recycled O2 CO2

Separation Plant

H2O CO2 (non

Atmospheric Disposal)

Air Separation Plant

WWWW

W

Furnace/Boiler Convective Zone Radiative Zone Coal Coal Mill Primary Nitrogen Oxygen Air Cooler Electro-static Precipitator Recycled O2 CO2

Separation Plant

H2O CO2 (non

Atmospheric Disposal)

Air Separation Plant

WWWW

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ASU Boiler

N2

Fuel

Air

Wet Recycle Recycled Flue Gas (mRFG) Dry

Recycle

CO2 - Rich Product (mPFG)

H20

Background – Recycle Ratio

MRFG RR = ---------------------- MRFG + MPFG

Via FGD

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Desktop Studies

Overview of CTF programme

Safety Fuel Issues Process Development Optimisation

CTF Studies

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Desktop Studies

Overview of CTF programme

 Regulation issue - LCPD limits for

  • xyfuel

 Pre-investment issues (upfront

parameters)

 Required footprint for retrofit (e.g.

air separation unit)

Safety Fuel Issues Process Development Optimisation

 Air leakage  Optimum recycle ratio  Air heater design  Optimisation of mixing strategy (where to add

O2 - PA/SA/TA etc.)

 Gas recirculation  Oil burner operation on oxyfuel  Flexibility - start-up/shutdown limited by air

separation unit so cold-start on air

CTF Studies

 Selection of coals (optimise purchasing)  Use of biomass  Furnace slagging  Furnace Corrosion  Fouling  NOX (chemistry not well understood)  Heavy metal recycling and ash composition  Safety handling and storage of oxygen and

CO2

 Flame detection issues (higher moisture and

CO2 may affect UV and IR absorption)

 Safety of mixing oxygen/CO2  Flame stability  Safe switch-over the oxyfuel combustion  Safety of staff with CO2 /flue gas leaks etc.  Purging for safety  Burner design  Carbon burnout  Heat transfer (radiative/convective properties)

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CTF oxyfuel conversion

> Two-stage conversion of the CTF – Phase 1: Stored CO2 injection – Phase 2: Flue gas recirculation > Why a two-phase strategy? – Rapid start-up with less (though significant) engineering – air ingress – Flexibility – Identify show stoppers or new issues at an early stage – Second stage to quantify full impact of issues such as NOX, slagging, corrosion and trace elements that cannot be fully studied by CO2 injection alone

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CTF oxyfuel conversion

> Two-stage conversion of the CTF – Phase 1: Stored CO2 injection – Phase 2: Flue gas recirculation – Cancelled following strategic review > Why a two-phase strategy? – Rapid start-up with less (though significant) engineering – air ingress – Flexibility – Identify show stoppers or new issues at an early stage – Second stage to quantify full impact of issues such as NOX, slagging, corrosion and trace elements that cannot be fully studied by CO2 injection alone – Cancelled following strategic review

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Rig modifications

> CO2 injection – Storage tanks for O2 and CO2 with mixing and safety systems – Modified system of blowers and SA/TA heaters – Steam boiler – Doping gasses (SOx, NOx) – Controls and logic interface with existing CTF system

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Boiler Steam Skid Coal

Tertiary Flow

Primary Air Secondary Air

Heaters

Mixing Skid Flow Control Skid

NOx/ SOx O2 CO2

Vaporiser Vaporiser

Secondary Flow Primary Flow

OXY OFA

(Not used on this burner)

Schematic of Once Through Oxy-Fuel System

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RWEnpower’s OxyFuel facility

O2, CO2 and N2 Storage Vessels

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RWEnpower’s OxyFuel facility

Evaporators

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RWEnpower’s OxyFuel facility

Gas mixers

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RWEnpower’s OxyFuel facility

Gas Heaters

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RWEnpower’s OxyFuel facility

Burner

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Schematic of CTF Test Furnace

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BOFCOM

Heat Transfer under OxyFuel Firing Conditions

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Driver for Studying Heat Transfer Distributions – Radiative and Convective

  • Radiation

heat transfer is driven by gas temperature (T4) while convective heat transfer by gas temperature and velocity.

  • To
  • perate

as “air equivalent” the balance between radiative and convective heat transfer has to be found

  • The recycled flue gas can be either wet or dry

dependent on where the recycled flue gas taken from in the system.

  • The recycled flue gas could be take wet from the
  • utlet of the ESP (where the moisture content

would be circa 18% by volume) or after an FGD system (where the moisture content would be circa 8% by volume).

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Radiative HT - South African coal – Dry Recycle

Furnace Heat Flux Measurements South African coal, Oxyfuel (3% O2)

200 250 300 350 400 450 500 500 1000 1500 2000 2500 3000 3500

Axial Distance from Burner, mm Radiative Heat Flux kW/m2

SAcoal/Air - 3% O2 Oxyfuel RR 65% Oxyfuel RR 68% Oxyfuel RR 70% Oxyfuel RR 72% Oxyfuel RR 75%

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IFRF Burner - RR 66%, 38% Inlet O2 Hot intense flame

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IFRF Burner – RR 77%; 28% Inlet O2 Cool Flame

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Normalised Convective & Radiative Heat Flux Russian Coal - Dry Recycle

Dry Oxyfuel Operation Normalised to Air Operation

Peak Radiation Flux, Convective heat transfer and calculated flame temperature

Russian coal 0.4 0.6 0.8 1 1.2 1.4 1.6 60% 65% 70% 75% 80% Effective Recycle Ratio Normalised Adiabatic Flame Temperature 0.4 0.6 0.8 1 1.2 1.4 1.6

Normalised Radiative and Convective Heat Flux

Normalised Flame Temperature (calculated) Peak Normalised Heat Flux (measured) Normalised Convective HTC (measured) Measured Convective Heat Transfer Coefficient indicates 74% Recycle is "Air-equivalent" Calculated dry oxyfuel adiabatic flame temperatures are equivalent to air at 69% recycle Measured Peak Radiative data indicates 74% Recycle is "Air- equivalent"

New Build Retrofit Avoid

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65% rr, Total flow 567.69kg/h Sec 412kg/h@38.0% O2 (time: 14:36) 70% rr, Total flow 656.99kg/h Sec 501kg/h@29.0% O2 (time: 13:14) 68% rr, Total flow 615.71kg/h Sec 457kg/h@31.6% (time: 13:44) 65% rr, Total flow 554.74kg/h Sec 400kg/h@35.8% O2 (time: 14:19) 75% rr, Total flow 806.57kg/h Sec 650kg/h@25.4% O2 (time: 12:29) 72% rr, Total flow 722.64kg/h Sec 567kg/h@28.9%O2 (time: 12:54) 70% rr, Total flow 670.91kg/h Sec 516kg/h@31.3%O2 (time: 13:27) 68% rr, Total flow 624.70kg/h Sec 470kg/h@33.9%O2 (time: 14:04) 72% rr, Total flow 709.04kg/h Sec 552kg/h@26.5%O2 (time: 12:41)

Oxycoal - Flame Stability Flame Animations (South African Coal)

  • Images for different simulated recycle rates under low O2 settings
  • Images for different simulated recycle rates under high O2 settings
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Note: Images and temperature profiles shown here are averaged for 10 instantaneous readings over about 2 minutes.

Flame Images

75% RR: Sec.f 600kg/h@22.1%

(time: 13:41, 29-10)

72% RR: Sec.f 513kg/h@25.5%

(time: 14:18, 29-10)

65% RR: Sec.f 368kg/h@34.8%

(time: 15:18, 29-10)

68%RR: Sec.f

422kg/h@30.5%

(time: 15:05, 29-10)

62% RR: Sec.f 322kg/h@39.4%

(time: 12:32, 30-10)

  • Temperature profiles for different simulated recycle rates under

lower O2 settings

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Conclusions (Dry recycle data)

> Air operation radiative heat flux found to be equivalent to 72 – 75% recycle ratio (due to different radiative properties of carbon dioxide compared to nitrogen) > Radiative heat flux peak shifts downstream as recycle rate increases > Convective Heat Transfer equivalent to air at 74% recycle ratio (main factors here are temperature and mass flow) > Working range exists (there is a recycle ratio for which both radiative and convective transfer can be reasonable matched between air and

  • xyfuel operation. It is therefore possible to design a boiler for efficient
  • peration in both oxyfuel and air conditions).

> Flame stability decreases with increasing recycle ratio

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BOFCOM

Deposition Studies under OxyFuel Firing Conditions

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Combustion Test Facility

RWE have carried out a series of deposition runs on their pilot scale combustion test facility

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Bofcom Deposition Data – Russian Coal 2

900 1000 1100 1200 1300 64 66 68 70 72 74 76 Recycle Rate, % Temperature Deg C Furnace Exit Temperature Probe temperature

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Deposition efficiency and Deposit Type

5 10 15 20 25 1000 1020 1040 1060 1080 1100 1120

Deposit coupon temperature, Deg C Deposition Collection Efficiency, %

2 4 6 8 10

Deposition Type

Collection Efficiency % Deposition Type

{Collection Efficiency – Amount of ash sticking to probe / ash impacting on probe}

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Impact = f (deposition rate and Deposit type)

1 2 3 60 65 70 75 80

Recycle Ratio, %

Im pact of slagging

Rus 2

Major Problem Concern

Observations

As the recycle rate is reduced the ash become more fused –

stronger deposits and the deposition efficiency increases.

Temperature is a direction function of recycle rate No apparent chemical differences.

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Caption competition!

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Caption competition!

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Caption competition!

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BOC / RWE

Oxygen injection

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Oxyfuel with Centre Lance Oxygen injection

> Injection

  • f

pure

  • xygen

centrally through the burner’s core air tube instead of through the secondary air register. > Strong impact on the flame > Potential reduction in NOx

O2 injection: 39kg/h O2 injection: 52kg/h

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RWE

Fuel Flexibility

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Fuel flexibility – From Lignite to anthracite?

Radiative Heat Flux Oxyfuel (3% O2), dry

200 250 300 350 400 450 500 500 1000 1500 2000 2500 3000 3500 Axial Distance from Burner, mm Radiative Heat Flux kW/m2

SA Bituminous/Air-3% O2 SA Bituminous, OF 68% RR Russian Semi-Anthracite, OF 68% RR

Semi-Anthracite Coal, Recycle Ratio 68%, 3% O2

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Fuel Flexibility

> What has been demonstrated is that: – Using oxy-fuel combustion technology, a wider range of coals can be fired in a swirl burner configuration for application in wall fired boilers than is conventional with standard air firing. – This offers potential for greater fuel type flexibility, wider options in fuel diet and consequential fuels costs than would be normal in a conventional only air fired wall fired boiler. > This scoping study has demonstrated that flame ignition, stability and luminosity for low volatile fuel can be improved under oxy-fuel firing conditions compared to air and deserves a more systematic study.

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EcoScrub OxyFuel / Post Combustion Capture Hybrid

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Ecoscrub

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Flames

IFRF Burner - RR 66%, 38% Inlet O2 IFRF Burner – RR 77%; 28% Inlet O2 IFRF Burner – ECO Scrub Case 3B Air as Primary gas! Reduced heat capacity of N2 vs CO2

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Some Thoughts

  • Development of a low cost option for carbon capture on existing modern

coal-fired power plant using a novel combination of techniques employed for CO2 capture, such as O2 enrichment and post-combustion solvent scrubbing, together with measures to increase efficiency, reduce steam consumption and generate power requirements.

  • Definitely an interesting idea and not crazy but lots of questions to answer
  • Demonstrate the ideas
  • Commercial – Fuel flexibility; Key pluses over pure OxyF/Amine
  • Air ingress

Further work

  • Further cost analysis but needs to be site specific
  • Future developments in Amines targeted at 28% CO2 concentration
  • Lower cost oxygen production
  • Membrane development.
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Acknowledgements

> The combustion test facility conversion to OxyFuel was financed by RWE npower > The experimental programmes are co-funded by RWE npower and: > The European Commission Research Fund for Coal and Steel - BOFCom

– Heat Transfer, Wet and Dry recycle, Biomass, OFA, Deposition studies

> The UK Technology Strategy Board - Oxycoal-UK

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Conclusion

(Biased and do not represent RWE’s views!!)

> Oxyfuel is a better option than post combustion capture – Suitable for retrofit – Flexibility on fuel – It is more flexible than Post Combustion Capture

  • Where the oxygen is injected
  • Recycle rate
  • OFA port options.
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Thank you for your attention.

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Latest results – Wet / Dry comparison

Radiative Heat Flux Russian coal B, 18%H2O, 3% O2

200 250 300 350 400 450 500 550 500 1000 1500 2000 2500 3000 3500 Axial Distance from Burner, mm Radiative Heat Flux kW/m2

Russian B/Air, 3%O2 - dry OF 65% RR - dry OF 72% RR - dry OF 75% RR - dry OF 68% RR - wet OF 72% RR - wet OF 75% RR - wet OF 65% RR - wet

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Latest results – Wet (8%) / Wet (18%) comparison

Radiative Heat Flux Russian coal B, 3% O2

200 250 300 350 400 450 500 550 500 1000 1500 2000 2500 3000 3500 Axial Distance from Burner, mm Radiative Heat Flux kW/m 2

OF 68% RR, H2O 18% - wet OF 68% RR, H2O 8% - wet

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Wet (18%) and Dry Recycle Normalised Peak Radiative and Convective Heat Flux

Normalised Peak Radiative and Convective Heat Flux Russian coal, 3%O2, Dry v's Wet combustion

0.4 0.6 0.8 1.0 1.2 1.4 60% 65% 70% 75% 80% Effective Recycle ratio Normalised convective and peak radiative HF

Peak radiative - dry Peak radiative - wet Convective - dry Convective - wet Li (P k di ti Oxyfuel operation normalised to Air operation