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

report (PTR)o Programmer adjusted boiler operating parameters sucho Programmer adjusted boiler operating parameters such

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

Fuel lb/s Btu/lb 116 5 6735Fuel, lb/s, Btu/lb 116.5, 6735

Total Air, lb/s, 785.5

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

economic/commercial aspectseconomic/commercial aspects

PARAMETERS AFFECTED BY FUEL CHANGE16

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

EVALUATIONS AND CONCLUSIONS 23

OPTIMISATION & DECISION MATRIX TABLESOutput & performance

Emissioncompliance

Extensionof life

Economy of operation

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

25

Discussion and QA

Thank you