detailed engineering analysis of retrofit and new-build
TRANSCRIPT
untitledDetailed Engineering Analysis of Retrofit and New-Build
Oxyfuel Power Plants Gerry Hesselmann & Karsten Riedl
Doosan Babcock / UniperDoosan Babcock / Uniper
OverviewOverview
Engineering assessment of the oxyfuel process applied to retrofit and new-build plant
Parametric Assessment • Establish viable operational envelope • High level study investigating the impact of FGR flow, location of FGR extraction point,
excess O2, and coal quality using Excel spreadsheet and OEM expertise
Engineering Study • Establish impact of process parameters on the performance of boiler plant • Identify optimum operating conditions and any requirement for pressure part modification • Detailed calculations of furnace and boiler thermal performance using OEM design software
Potential for Efficiency Gains I ti t t ti l ffi i i f f l l t ti i ti• Investigate potential efficiency gains for oxyfuel plant optimisation
• Analysis of the full plant (air separation, boiler/turbine island, gas clean-up) using commercial software (Thermoflow)
11th ECCRIA : Sheffield : 5th~7th September 2016 Page 2 Doosan Babcock
Retrofit and New-Build BoilersRetrofit and New-Build Boilers
Retrofit • 350MWe • Subcritical steam conditions:
• Main steam 541°C, 172barg • Reheat steam 541°C, 39barg
• Two-Pass boiler configuration • Opposed wall fired with low NOx burners & OFA • Domestic bituminous coal (Fuel ratio = 2.1)
New-Build • 600MWe • Supercritical steam conditions (boiler outlet)
• Main steam 602°C, 287barg R h t t 623°C 60b• Reheat steam 623°C, 60barg
• Two-Pass boiler configuration • Opposed wall fired with low NOx burners & OFA
S th Af i bit i l (F l ti 2 4)• South African bituminous coal (Fuel ratio = 2.4)
11th ECCRIA : Sheffield : 5th~7th September 2016 Page 3 Doosan Babcock
Furnace ModelFurnace Model
Establish furnace thermal performance
Furnace model (Hottel’s Zone Method) • Full furnace (no assumption of symmetry) • 3396/4290 gas zones for retrofit/new-build boiler (adequate
resolution of geometric features) • Extends to FEGT plane (interface with boiler model) • Includes radiant pendant surfacesIncludes radiant pendant surfaces
Air firing and oxyfuel firing conditions analysed • Thermal boundary conditions fixed (wall conductance etc. y (
derived from plant test) • Numerous cases considered to investigate the effect of FGR
rate (52~80%), FGR extraction point, excess O2 (1~6%), and coal type (Indonesia USA South Africa)coal type (Indonesia, USA, South Africa)
• FGR options considered were: • Hot/Wet – i.e. FGR from ESP outlet • Cold/Wet – i.e. FGR from FGD outlet, no moisture removal, • Cold/Dry – i.e. FGR from FGD outlet with moisture removal
11th ECCRIA : Sheffield : 5th~7th September 2016 Page 4 Doosan Babcock
Boiler ModelBoiler Model
Boiler model • “Simple” furnace module; furnace performance taken from
zone model prediction • Detailed convective pass model; modules for banks, cavities,
slings, drum, spray attemporators
Air firing and oxyfuel firing conditions analysed • Thermal performance calibrated to air fired plant data; bank
factors held constant for oxyfuel firing y g • Furnace and boiler model thermal performance converged • Same conditions investigated as for furnace model
11th ECCRIA : Sheffield : 5th~7th September 2016 Page 5 Doosan Babcock
Parametric Pre-StudyParametric Pre-Study
A high-level parametric pre-study identified several operational constraints.
Minimum achievable FGR rate is ~50% • SFGR tends to zero as we need to maintain a
fixed PFGR flow for coal transport • SFGR O2 concentration increases with reducing
FGR rate and tends to 100%FGR rate, and tends to 100% • Need direct O2 injection or higher PFGR O2
concentration to operate at low FGR rates
FGR option has a major impact on SO2 concentration (and, by inference, SO3) • Hot/wet SFGR (i.e. SFGR has no SO2 removal)
leads to significantly higher SO2 concentration in the boiler and recycle gas ducts
11th ECCRIA : Sheffield : 5th~7th September 2016 Page 6 Doosan Babcock
Retrofit Boiler - “Simulated Air” Operation – FGR OptionRetrofit Boiler - Simulated Air Operation FGR Option
67% FGR commonly considered to deliver boiler thermal performance comparable to air
Operating Mode (FGR Option) Air Cold/Wet Cold/Dry Hot/Wet Walls & Roof (MW) 319 7 339 5 361 9 339 9Walls & Roof (MW) 319.7 339.5 361.9 339.9 Primary Platen (MW) 84.3 77.4 76.2 78.4 Secondary Platen (MW) 83.3 86.0 84.7 86.0y ( ) Arch Temperature (°C) 1399 1514 1532 1515 FEGT (°C) 1041 1072 1071 1072
Wet FGR at 67% gives furnace performance comparable to air firing • But the balance of heat pick-up between the lower and upper furnace is changed (higher arch
l l t t )level gas temperature)
Wet vs. dry FGR generally has a modest impact E t th t d FGR l d t i ifi t i i h t t ti d t i fi i• Except that dry FGR leads to a significant increase in heat to evaporation compared to air firing
Excess O2 and coal had a minimal impact
11th ECCRIA : Sheffield : 5th~7th September 2016 Page 7 Doosan Babcock
Retrofit Boiler – Impact of FGR FEGT
Retrofit Boiler Impact of FGR FGR flow dominates furnace thermal performance
FGR rate has: • Only a modest impact on FEGT (±100°C) • A significant impact on furnace heat absorption (evaporation)
and platen heat absorption (superheat) R di ti t t i FGR fl d H t t W ll & R f• Radiating temperature increases as FGR flow reduces
• Minimal impact of wet vs. dry FGR At ~67% FGR the furnace performance is comparable to air firing
I d FGR d h t i k t th di t ( ti )
Heat to Walls & Roof
Increased FGR reduces heat pick-up to the radiant (evaporative) furnace, and will have a significant impact on the convective pass • Too much evaporation in the furnace (low FGR flows) leads to
increased flow through the superheaters and a consequentialincreased flow through the superheaters and a consequential steam temperature shortfall
• To little evaporation in the furnace (high FGR flows) leads to higher steam temperatures, and hence increasing
Heat to Platen
attemporator spray flows • In conventional air firing FGR is one of the possible measures
for reheat steam temperature control. It works by redistributing the balance of heat absorption between the radiantthe balance of heat absorption between the radiant (evaporative) furnace and the convective (superheat/reheat) boiler. The same principles are seen to be in effect under oxyfuel firing conditions.
11th ECCRIA : Sheffield : 5th~7th September 2016 Page 8 Doosan Babcock
Retrofit Boiler – Impact of FGRRetrofit Boiler Impact of FGR
Acceptable boiler thermal performance can only be hi d l ti l f FGRachieved over a relatively narrow range of FGR
As FGR flow is reduced the evaporation, and hence t fl i i dsteam flow, is increased
• There is a consequential shortfall in main steam temperature at low FGR rates
At high FGR flow the evaporation, and hence steam flow, is reduced • This would if unchecked lead to increased main• This would, if unchecked, lead to increased main
steam temperature • Steam temperatures are controlled by attemporator
spray flow whereby water is injected into thespray flow, whereby water is injected into the superheat steam circuit and is evaporated
• At high FGR flows the required spray flow is excessive
Economiser outlet gas temperature is insensitive to FGR flow
11th ECCRIA : Sheffield : 5th~7th September 2016 Page 9 Doosan Babcock
New-Build BoilerNew-Build Boiler
Greater scope for new-build boiler design to be optimised for low FGR (lower cost)
67% FGR – “Simulated Air” • Demonstrated oxyfuel burner technology • Conventional air fired boiler design can be used • Impact of FGR comparable to retrofit boiler; increased heat to walls as FGR reduces leads to higher
furnace exit steam temperature in a once-through supercritical boiler
60% FGR – 2nd Generation Oxyfuel Burner • Enhanced oxyfuel burner with direct O2 injection required. Concept tested at CIUDEN (4x5MWt) • Significant adaptation of conventional boiler design requiredg p g q
• Reduced economiser and furnace surface (furnace tube material constraint limits allowable steam temperature)
• Increased superheater and reheater surface so that design steam temperatures are achieved
54% FGR – 3rd Generation Oxyfuel Burner • FGR to primary (coal transport) stream with no FGR to secondary (windbox) stream; requires a
completely new burner designcompletely new burner design • Not viable to adapt a conventional boiler design as the changes required are too great
11th ECCRIA : Sheffield : 5th~7th September 2016 Page 10 Doosan Babcock
Exergetic Evaluation – New BuildExergetic Evaluation New Build Oxyfuel fired plant efficiency is ~9%age points lower than for air firing, due to ASU & CPU Key to plant efficiency → efficient combustionKey to plant efficiency efficient combustion
11th ECCRIA : Sheffield : 5th~7th September 2016 Page 11 Uniper
Efficiency Gains – New-BuildEfficiency Gains New-Build
Improvements to the combustion system lead to Air Oxy Opt appreciable efficiency gains, especially for new-build
Assumptions for optimised oxyfuel plant: • Second generation burner • Excess oxygen level: 15% → 10% • Flue gas recycle rate: 67% → 60% • Oxygen in primary combustion gas: 21 vol.-% → 30
vol.-% • Cold flue gas recycle → Hot flue gas recycle
Results: • Net electric efficiency: 35.0% → 36.7%
E ti ffi i i 1 7 % i t• Energetic efficiency gain: +1.7 %age point • Adapted boiler design cf. air fired reference
E i ti i t ll ti t i t li it ffi i i f• Existing installation constraints limit efficiency gains for oxyfuel retrofit to +0.8 %age point
11th ECCRIA : Sheffield : 5th~7th September 2016 Page 12 Uniper
ConclusionsConclusions
Oxyfuel is technically viable
There are practical limits on the operational envelope for the oxyfuel process • E.g. minimum FGR rate is constrained by burner design and boiler configuration
Existing air-fired boilers can be retrofitted with oxyfuel • Use of “Simulated Air” (i.e. ~67% FGR) avoids the need for pressure part modifications &
burner upgrades • Hardware constraints limit the potential for optimising efficiency when oxyfuel firing
The design of new-build boilers can be optimised for oxyfuel firing • 2nd generation burners facilitate firing at low FGR rates • Adapting the heating surface arrangement accommodates the redistribution of furnace heat
b ti i t th ti ( h t & h t )absorption into the convective pass (superheaters & reheaters)
New-build plant is inherently more efficient, and offers more opportunity for process optimisation Mi i i ti f b il ASU d CPU l t ib ti• Minimisation of boiler, ASU and CPU loss contribution
• Optimal burner design at minimum excess O2 level and FGR rate
11th ECCRIA : Sheffield : 5th~7th September 2016 Page 13 Doosan Babcock / Uniper
AcknowledgementsAcknowledgements
The work presented here was carried out as a part of Tasks 5.5 & 5.6 of the RELCOM project. The project was undertaken with the financial support of the European Commission under Grant Agreement Number 268191.
The following directly contributed to the work presented here: • S Black, K Kuczynski, C McGhie, S Balasubramanian, D Couling (Uniper/EON)
Additionally the following were active in Tasks 5.5 & 5.6: • P Kilgallon (DPS), S Grathwohl (USTUTT), M Louis-Louisy, A Neveu-Dubosc (EDF), F Verplaetsen (KUL)
Doosan Babcock / UniperDoosan Babcock / Uniper
OverviewOverview
Engineering assessment of the oxyfuel process applied to retrofit and new-build plant
Parametric Assessment • Establish viable operational envelope • High level study investigating the impact of FGR flow, location of FGR extraction point,
excess O2, and coal quality using Excel spreadsheet and OEM expertise
Engineering Study • Establish impact of process parameters on the performance of boiler plant • Identify optimum operating conditions and any requirement for pressure part modification • Detailed calculations of furnace and boiler thermal performance using OEM design software
Potential for Efficiency Gains I ti t t ti l ffi i i f f l l t ti i ti• Investigate potential efficiency gains for oxyfuel plant optimisation
• Analysis of the full plant (air separation, boiler/turbine island, gas clean-up) using commercial software (Thermoflow)
11th ECCRIA : Sheffield : 5th~7th September 2016 Page 2 Doosan Babcock
Retrofit and New-Build BoilersRetrofit and New-Build Boilers
Retrofit • 350MWe • Subcritical steam conditions:
• Main steam 541°C, 172barg • Reheat steam 541°C, 39barg
• Two-Pass boiler configuration • Opposed wall fired with low NOx burners & OFA • Domestic bituminous coal (Fuel ratio = 2.1)
New-Build • 600MWe • Supercritical steam conditions (boiler outlet)
• Main steam 602°C, 287barg R h t t 623°C 60b• Reheat steam 623°C, 60barg
• Two-Pass boiler configuration • Opposed wall fired with low NOx burners & OFA
S th Af i bit i l (F l ti 2 4)• South African bituminous coal (Fuel ratio = 2.4)
11th ECCRIA : Sheffield : 5th~7th September 2016 Page 3 Doosan Babcock
Furnace ModelFurnace Model
Establish furnace thermal performance
Furnace model (Hottel’s Zone Method) • Full furnace (no assumption of symmetry) • 3396/4290 gas zones for retrofit/new-build boiler (adequate
resolution of geometric features) • Extends to FEGT plane (interface with boiler model) • Includes radiant pendant surfacesIncludes radiant pendant surfaces
Air firing and oxyfuel firing conditions analysed • Thermal boundary conditions fixed (wall conductance etc. y (
derived from plant test) • Numerous cases considered to investigate the effect of FGR
rate (52~80%), FGR extraction point, excess O2 (1~6%), and coal type (Indonesia USA South Africa)coal type (Indonesia, USA, South Africa)
• FGR options considered were: • Hot/Wet – i.e. FGR from ESP outlet • Cold/Wet – i.e. FGR from FGD outlet, no moisture removal, • Cold/Dry – i.e. FGR from FGD outlet with moisture removal
11th ECCRIA : Sheffield : 5th~7th September 2016 Page 4 Doosan Babcock
Boiler ModelBoiler Model
Boiler model • “Simple” furnace module; furnace performance taken from
zone model prediction • Detailed convective pass model; modules for banks, cavities,
slings, drum, spray attemporators
Air firing and oxyfuel firing conditions analysed • Thermal performance calibrated to air fired plant data; bank
factors held constant for oxyfuel firing y g • Furnace and boiler model thermal performance converged • Same conditions investigated as for furnace model
11th ECCRIA : Sheffield : 5th~7th September 2016 Page 5 Doosan Babcock
Parametric Pre-StudyParametric Pre-Study
A high-level parametric pre-study identified several operational constraints.
Minimum achievable FGR rate is ~50% • SFGR tends to zero as we need to maintain a
fixed PFGR flow for coal transport • SFGR O2 concentration increases with reducing
FGR rate and tends to 100%FGR rate, and tends to 100% • Need direct O2 injection or higher PFGR O2
concentration to operate at low FGR rates
FGR option has a major impact on SO2 concentration (and, by inference, SO3) • Hot/wet SFGR (i.e. SFGR has no SO2 removal)
leads to significantly higher SO2 concentration in the boiler and recycle gas ducts
11th ECCRIA : Sheffield : 5th~7th September 2016 Page 6 Doosan Babcock
Retrofit Boiler - “Simulated Air” Operation – FGR OptionRetrofit Boiler - Simulated Air Operation FGR Option
67% FGR commonly considered to deliver boiler thermal performance comparable to air
Operating Mode (FGR Option) Air Cold/Wet Cold/Dry Hot/Wet Walls & Roof (MW) 319 7 339 5 361 9 339 9Walls & Roof (MW) 319.7 339.5 361.9 339.9 Primary Platen (MW) 84.3 77.4 76.2 78.4 Secondary Platen (MW) 83.3 86.0 84.7 86.0y ( ) Arch Temperature (°C) 1399 1514 1532 1515 FEGT (°C) 1041 1072 1071 1072
Wet FGR at 67% gives furnace performance comparable to air firing • But the balance of heat pick-up between the lower and upper furnace is changed (higher arch
l l t t )level gas temperature)
Wet vs. dry FGR generally has a modest impact E t th t d FGR l d t i ifi t i i h t t ti d t i fi i• Except that dry FGR leads to a significant increase in heat to evaporation compared to air firing
Excess O2 and coal had a minimal impact
11th ECCRIA : Sheffield : 5th~7th September 2016 Page 7 Doosan Babcock
Retrofit Boiler – Impact of FGR FEGT
Retrofit Boiler Impact of FGR FGR flow dominates furnace thermal performance
FGR rate has: • Only a modest impact on FEGT (±100°C) • A significant impact on furnace heat absorption (evaporation)
and platen heat absorption (superheat) R di ti t t i FGR fl d H t t W ll & R f• Radiating temperature increases as FGR flow reduces
• Minimal impact of wet vs. dry FGR At ~67% FGR the furnace performance is comparable to air firing
I d FGR d h t i k t th di t ( ti )
Heat to Walls & Roof
Increased FGR reduces heat pick-up to the radiant (evaporative) furnace, and will have a significant impact on the convective pass • Too much evaporation in the furnace (low FGR flows) leads to
increased flow through the superheaters and a consequentialincreased flow through the superheaters and a consequential steam temperature shortfall
• To little evaporation in the furnace (high FGR flows) leads to higher steam temperatures, and hence increasing
Heat to Platen
attemporator spray flows • In conventional air firing FGR is one of the possible measures
for reheat steam temperature control. It works by redistributing the balance of heat absorption between the radiantthe balance of heat absorption between the radiant (evaporative) furnace and the convective (superheat/reheat) boiler. The same principles are seen to be in effect under oxyfuel firing conditions.
11th ECCRIA : Sheffield : 5th~7th September 2016 Page 8 Doosan Babcock
Retrofit Boiler – Impact of FGRRetrofit Boiler Impact of FGR
Acceptable boiler thermal performance can only be hi d l ti l f FGRachieved over a relatively narrow range of FGR
As FGR flow is reduced the evaporation, and hence t fl i i dsteam flow, is increased
• There is a consequential shortfall in main steam temperature at low FGR rates
At high FGR flow the evaporation, and hence steam flow, is reduced • This would if unchecked lead to increased main• This would, if unchecked, lead to increased main
steam temperature • Steam temperatures are controlled by attemporator
spray flow whereby water is injected into thespray flow, whereby water is injected into the superheat steam circuit and is evaporated
• At high FGR flows the required spray flow is excessive
Economiser outlet gas temperature is insensitive to FGR flow
11th ECCRIA : Sheffield : 5th~7th September 2016 Page 9 Doosan Babcock
New-Build BoilerNew-Build Boiler
Greater scope for new-build boiler design to be optimised for low FGR (lower cost)
67% FGR – “Simulated Air” • Demonstrated oxyfuel burner technology • Conventional air fired boiler design can be used • Impact of FGR comparable to retrofit boiler; increased heat to walls as FGR reduces leads to higher
furnace exit steam temperature in a once-through supercritical boiler
60% FGR – 2nd Generation Oxyfuel Burner • Enhanced oxyfuel burner with direct O2 injection required. Concept tested at CIUDEN (4x5MWt) • Significant adaptation of conventional boiler design requiredg p g q
• Reduced economiser and furnace surface (furnace tube material constraint limits allowable steam temperature)
• Increased superheater and reheater surface so that design steam temperatures are achieved
54% FGR – 3rd Generation Oxyfuel Burner • FGR to primary (coal transport) stream with no FGR to secondary (windbox) stream; requires a
completely new burner designcompletely new burner design • Not viable to adapt a conventional boiler design as the changes required are too great
11th ECCRIA : Sheffield : 5th~7th September 2016 Page 10 Doosan Babcock
Exergetic Evaluation – New BuildExergetic Evaluation New Build Oxyfuel fired plant efficiency is ~9%age points lower than for air firing, due to ASU & CPU Key to plant efficiency → efficient combustionKey to plant efficiency efficient combustion
11th ECCRIA : Sheffield : 5th~7th September 2016 Page 11 Uniper
Efficiency Gains – New-BuildEfficiency Gains New-Build
Improvements to the combustion system lead to Air Oxy Opt appreciable efficiency gains, especially for new-build
Assumptions for optimised oxyfuel plant: • Second generation burner • Excess oxygen level: 15% → 10% • Flue gas recycle rate: 67% → 60% • Oxygen in primary combustion gas: 21 vol.-% → 30
vol.-% • Cold flue gas recycle → Hot flue gas recycle
Results: • Net electric efficiency: 35.0% → 36.7%
E ti ffi i i 1 7 % i t• Energetic efficiency gain: +1.7 %age point • Adapted boiler design cf. air fired reference
E i ti i t ll ti t i t li it ffi i i f• Existing installation constraints limit efficiency gains for oxyfuel retrofit to +0.8 %age point
11th ECCRIA : Sheffield : 5th~7th September 2016 Page 12 Uniper
ConclusionsConclusions
Oxyfuel is technically viable
There are practical limits on the operational envelope for the oxyfuel process • E.g. minimum FGR rate is constrained by burner design and boiler configuration
Existing air-fired boilers can be retrofitted with oxyfuel • Use of “Simulated Air” (i.e. ~67% FGR) avoids the need for pressure part modifications &
burner upgrades • Hardware constraints limit the potential for optimising efficiency when oxyfuel firing
The design of new-build boilers can be optimised for oxyfuel firing • 2nd generation burners facilitate firing at low FGR rates • Adapting the heating surface arrangement accommodates the redistribution of furnace heat
b ti i t th ti ( h t & h t )absorption into the convective pass (superheaters & reheaters)
New-build plant is inherently more efficient, and offers more opportunity for process optimisation Mi i i ti f b il ASU d CPU l t ib ti• Minimisation of boiler, ASU and CPU loss contribution
• Optimal burner design at minimum excess O2 level and FGR rate
11th ECCRIA : Sheffield : 5th~7th September 2016 Page 13 Doosan Babcock / Uniper
AcknowledgementsAcknowledgements
The work presented here was carried out as a part of Tasks 5.5 & 5.6 of the RELCOM project. The project was undertaken with the financial support of the European Commission under Grant Agreement Number 268191.
The following directly contributed to the work presented here: • S Black, K Kuczynski, C McGhie, S Balasubramanian, D Couling (Uniper/EON)
Additionally the following were active in Tasks 5.5 & 5.6: • P Kilgallon (DPS), S Grathwohl (USTUTT), M Louis-Louisy, A Neveu-Dubosc (EDF), F Verplaetsen (KUL)