11 th European conference on coal research and its applications 11 European conference on coal research and its applications Session 5B – Biomass 2 University of Sheffield , 5 th -7 th September 2016 Effective utilisation of existing coal-fired plants for conversion to biomass firing: design methodology and prediction of performance Steve Mould Chief Engineer – Energy Chief Engineer Energy and Saravana Bavan Balakrishnan Principal Engineer – Boilers Aug 2016
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11th European conference on coal research and its applications11 European conference on coal research and its applicationsSession 5B – Biomass 2
University of Sheffield , 5th-7th September 2016
Effective utilisation of existing coal-firedplants for conversion to biomass firing: design methodology and prediction of g gy p
performance
Steve MouldChief Engineer – EnergyChief Engineer Energy
andSaravana Bavan Balakrishnan
Principal Engineer – Boilers
Aug 2016
INTRODUCTION2
INTRODUCTION
This presentation looks at some of the issues to be addressed within a biomass conversion studybe addressed within a biomass conversion studyStudy has to include:
Review of reasons for conversiono Review of reasons for conversiono Due diligence of boiler arrangement and equipment details o Methodology for conversiono Methodology for conversiono Performance predictionso Parameters affected by fuel changeo Parameters affected by fuel changeo Equipment refinements and modificationso Evaluations and conclusionso Evaluations and conclusions
SOME OF THE REASONS FOR CONVERSION3
SOME OF THE REASONS FOR CONVERSION
o Life extensiono Improved efficiencyo Improved efficiencyo Compliance with latest legislation requirementso Reduction in emissionso Reduction in emissionso Renewable energy obligation certificates (ROCs)o Contract for difference(CfD)o Contract for difference(CfD)
DUE DILIGENCE AND4
DUE DILIGENCE AND PLANT REMNANT LIFE ASSESSMENT
Uses the following plant documents/records Equipment datasheetso Equipment datasheets
o Operating logs/registerso Equipment maintenance recordso Equipment maintenance recordso Safety incident and events registerso Performance test reportso Performance test reports o Visual inspection
To assess:To assess:o Remnant life of pressure parts
Condition of non pressure parts and equipmento Condition of non-pressure parts and equipment
DUE DILIGENCE AND5
DUE DILIGENCE AND PLANT REMNANT LIFE ASSESSMENT CONTINUED
Remnant life of pressure partso Furnaceo Furnaceo Evaporatorso Drumo Drumo Superheatero Reheatero Economisero Miscellaneous pressure-containing components
(bl d d i i l t )(blowdown, drains, raisers, valves etc.)
DUE DILIGENCE AND6
DUE DILIGENCE AND PLANT REMNANT LIFE ASSESSMENT CONTINUED
Condition of non-pressure parts & equipmento Fuel handlingo Fuel handlingo Millingo Airheatero Airheatero Ducting – air and flue gaso Stack o Structural arrangementso Expansion joints
METHODOLOGY FOR CONVERSION7
METHODOLOGY FOR CONVERSIONSTUDY FORMAT
o Conduct due diligenceo Obtain recent or conduct performance test datao Obtain recent or conduct performance test datao Development of coal performance model o Process flow diagram for coal combustiono Establish biomass fuel optionso Calculation potential output and performance with biomass fuelo Compare fuel consumption and steam generation datao Compare fuel consumption and steam generation datao Compare and evaluate environmental emissions benefits and
compliance to latest regulationo Identify and evaluate equipment refurbishment and modificationo Identify and evaluate equipment refurbishment and modification
requirementso Establish decision tree matrix
PERFORMANCE PREDICTIONS8
PERFORMANCE PREDICTIONSEXISTING PLANT PERFORMANCE MODEL – COAL
The following slides present the basic parameters for this typical example of theoretical study for a nominal 350 MW
l fi d it i STEAMPRO t ftcoal fired unit using STEAMPRO computer software.
o Fuel comprised of mixed coal from Indian and Indonesiano Fuel comprised of mixed coal from Indian and Indonesian lignite
o Input actual boiler design physical dimensions to modelo Target performance as based on recent performance test
as excess air, primary to secondary ratios, bypass and recirculation flows until the model represents fl / /t t i f ti f PTR ithiflow/pressure/temperature information from PTR within an agreed acuracy
PERFORMANCE PREDICTIONS9
PERFORMANCE PREDICTIONSEXISTING PLANT PERFORMANCE MODEL – COAL
PERFORMANCE PREDICTIONS10
PERFORMANCE PREDICTIONSEXISTING PLANT PERFORMANCE MODEL – COAL
Key Output & Performance data:
Gross Output, kWe 363410Net Output, kWe 331975
Plant net eff (LHV), % 38.05Main steam, kg/s, °C, bar 315, 543, 171.7HRH k /HRH steam, kg/s, °C, bar 257.6, 541.4, 36.3FW, kg/s, °C, bar 315, 281, 178.6
F l lb/ Bt /lb 55 7 13838Fuel, lb/s, Btu/lb 55.7, 13838
Total Air, lb/s, 686.7
PA lb/ 49 5PA, lb/s 49.5FG exhaust, lb/s, °C 888.9, 133
PERFORMANCE PREDICTIONS11
PERFORMANCE PREDICTIONSPLANT PERFORMANCE MODEL – BIOMASS FUEL
The following slides present the typical data basis used for this theoretical study conversion of a nominal 350 MW unit to biomass and modelled using STEAMPRO computerto biomass and modelled using STEAMPRO computer software.o Biomass case study used a waste wood fuel as the
alternative heat sourcealternative heat sourceo The software has utilised the same actual boiler design
physical dimensionsP d l i i l dj ti /it ti f b ilo Programmer used only minimal adjusting/iterating of boiler operating parameters such as excess air, primary to secondary ratios, bypass and recirculation flows to give the amended flow/pressure/temperature information presentedamended flow/pressure/temperature information presented by the next slides.
o Programmer to evaluate equipment modifications that may restore output and re model or accept down ratingrestore output and re-model or accept down rating
PERFORMANCE PREDICTIONS12
PERFORMANCE PREDICTIONSPERFORMANCE MODEL – BIOMASS FUEL CONTINUED
PERFORMANCE PREDICTIONS13
PERFORMANCE PREDICTIONSPERFORMANCE MODEL – BIOMASS FUEL CONTINUED
Key Output & Performance data:
G O t t kW 349913Gross Output, kWe 349913Net Output, kWe 315205
Plant net eff (LHV) % 38 09Plant net eff (LHV), % 38.09Main steam, kg/s, °C, bar 295.9, 563, 195HRH steam kg/s °C bar 243 7 561 45 9HRH steam, kg/s, C, bar 243.7, 561, 45.9FW, kg/s, °C, bar 296.7, 295.2, 203.4
PA lb/s Not givenPA, lb/s Not givenFG exhaust, lb/s, °C 972.7, 143
PARAMETERS AFFECTED BY FUEL CHANGE14
PARAMETERS AFFECTED BY FUEL CHANGECONVERSION IMPACT ON THE BOILER
The conversion of coal-fired units to biomass are known to have impact on the following heat transfer and combustion parameters p
o Luminous heat transfer oo Non-luminous heat transfero Flame temperatureso Changes in the heat pick-up profileo Primary and secondary air ratios and total requirements
PARAMETERS AFFECTED BY FUEL CHANGE15
PARAMETERS AFFECTED BY FUEL CHANGE CONVERSION IMPACT ON BOILER - CONTINUED
o The unit conversion impacts in water-steam generationo The unit conversion impacts in water steam generation profile
o Impact on desuperheater (DSH)o Verification of modification of DSH arrangemento Verification of need for modification of heat transfer
fsurfaceso The effect of modification is optimised to considerable
PARAMETERS AFFECTED BY FUEL CHANGEKEY FACTORS OF BIOMASS FUEL
o Biomass fuel analysiso Generally lower calorific valueo Changes in volatile mattero Fixed carbon
A ho Ash o Total fuel quantity requiremento Higher residual oxygen content which affects primary too Higher residual oxygen content which affects primary to
secondary air distributions for optimum NOx control
EQUIPMENT REFINEMENTS AND MODIFICATIONS17
EQUIPMENT REFINEMENTS AND MODIFICATIONSPROCESS AND EQUIPMENT MARGINS
The changes in these key parameters andThe changes in these key parameters and factors have influence on: o Process flow diagram for biomass combustion caseso Process flow diagram for biomass combustion caseso Impact on output and performance of the existing
surface designE t bli hi h th i ti i t h io Establishing whether existing equipment has margins sufficient to accommodate the fuel change or whether new is necessary
EQUIPMENT REFINEMENTS AND MODIFICATIONS18
EQUIPMENT REFINEMENTS AND MODIFICATIONS MILLING AND FUEL HANDLING SYSTEM
o Changes in the milling plant are expectedo Use of tube mills/hammer mills rather than ball roller
millso Fuel sampling/monitoring of variations is required too Fuel sampling/monitoring of variations is required to
ensure design changes cope with full variation rangeo Changes to biomass fuel require following micro studies
• Review of corrosion effects• Ash behaviour – verification of ash melting points
EQUIPMENT REFINEMENTS AND MODIFICATIONS19
EQUIPMENT REFINEMENTS AND MODIFICATIONS AIR AND FLUE GAS CHANGES
o Optimisation of primary air and secondary air p p y ydistribution
o PA fan and SA fan optimisationo Optimisation of excess airo Optimisation of excess airo Verification of suitability of existing fanso Optimisation of FD/PA/SA fan capacitiesp po ID (& FGR if applicable) fan optimisationo Analyse air and flue gas velocities in ducts
EQUIPMENT REFINEMENTS AND MODIFICATIONS20
EQUIPMENT REFINEMENTS AND MODIFICATIONS OTHER OPTIONS OF BIOMASS FIRING
o Co-firing of biomass with coal rather than full conversionS f t d t l f t i t d ith fi io Safety and control factors associated with co-firing
o De-rating of unit and commercial impacto Burner modification or separate burners for biomasso Burner modification or separate burners for biomass
firingo Impacts on boiler operating envelope
EQUIPMENT REFINEMENTS AND MODIFICATIONS21
EQUIPMENT REFINEMENTS AND MODIFICATIONS ADDITIONAL EQUIPMENT EVALUATIONS
o Changes from ESP to Bag filterso Safety of explosion environment implementation of ATEXo Safety of explosion environment- implementation of ATEX
compliant equipmento Addition of selective (SCR)/ non-selective catalytic
conversion (SNCR) requirementconversion (SNCR) requiremento Duct modification/ routing to accommodate the SCR/SNCRo Heat gain due to reduction in flue gas exit temperature
d tireductiono Comparison of output and auxiliary powero Comparison of additional emission abatement and p
compliance with latest LCPD standardso Estimate life and economics associated with optimised power
generation and creep and fatigue issuesgeneration and creep and fatigue issues
EVALUATIONS AND CONCLUSIONS22
EVALUATIONS AND CONCLUSIONS MAINTENANCE ISSUES
o Coating of biomass ash on heat transfer surfaceso Changes in the soot blowing requiremento Changes in the soot blowing requiremento Slagging and fouling factors associated with biomass
conversiono Tar and sticky surface issues with reference biomass o Periodic maintenance for bag filters
Maintenanceperformance compliance of life operation ance
Fuel & fuel handlingChanges to heatingsurfaces &surfaces & Pres PartsAir systemFlue gas systemAdditi lAdditional FGtreatment req’d
Using simple categories of Improved/Same/Worse or High/Medium/Low cost can be used to evaluate conversion options available.
EVALUATIONS AND CONCLUSIONS24
EVALUATIONS AND CONCLUSIONS SUMMARY OF CONCLUSIONS
o Cost of conversion will be influenced by theo Cost of conversion will be influenced by the technical solutions possible
o Conversion and refurbishment provides an optiono Conversion and refurbishment provides an option to restore compliance with latest emissions legislation
o Conversion and refurbishment normally can provide a further 10 year of life and associated revenue t /istream/income
o Provides energy generation through low carbon and possible government incentivespossible government incentives