Co-firing Biomass with Coal for Power Generation Suthum Patumsawad Department of Mechanical Engineering King Mongkuts Institute of Technology North Bangkok.

Co-firing Biomass with Co-firing Biomass with CoalCoalfor Power Generationfor Power Generation

Suthum PatumsawadSuthum PatumsawadDepartment of Mechanical EngineeringDepartment of Mechanical EngineeringKing Mongkut’s Institute of Technology North King Mongkut’s Institute of Technology North BangkokBangkokThailandThailand

Fourth Biomass-Asia Workshop “Biomass: Sources of Renewable Bioenergy and Biomaterial”

20-22 November 2007, Grand BlueWave Hotel Shah Alam, Malaysia.

Presentation overviewPresentation overview

IntroductionIntroduction Co-firing: concept and technologyCo-firing: concept and technology Drivers and barriersDrivers and barriers Lessons learnedLessons learned ConclusionsConclusions

Power GenerationPower Generation

CoalCoalUsed extensively to generate Used extensively to generate

electricity and process heat for electricity and process heat for industrial applications.industrial applications.

Poses significant world Poses significant world environmental problems:environmental problems:

global warming (COglobal warming (CO22))

acid gases (NOacid gases (NOxx and SO and SO22))

Power GenerationPower Generation

Biomass: as a fuel source.Biomass: as a fuel source.

Steadily increasingSteadily increasing Biomass fuels are COBiomass fuels are CO22-neutral, -neutral,

hence reduce global warming hence reduce global warming effects.effects.

The sulphur and nitrogen The sulphur and nitrogen contents are often lower.contents are often lower.

Biomass Biomass characteristicscharacteristics Lower densityLower density Higher moisture content, often up to Higher moisture content, often up to

50%50% Lower calorific valueLower calorific value Broader size distribution, unless pre-Broader size distribution, unless pre-

conditioned by screening, crushing or conditioned by screening, crushing or pelletisingpelletising

The variability of the material as a fuel The variability of the material as a fuel will be greaterwill be greater

Biomass Biomass characteristicscharacteristics Such variations in fuel quality, Such variations in fuel quality,

compared to coal, may have a compared to coal, may have a number of implications for plant number of implications for plant applications that include process applications that include process design and operation, and design and operation, and potentially, plant availability.potentially, plant availability.

Large investment cost/MWe of electricity Large investment cost/MWe of electricity Dependent on biomass availability Dependent on biomass availability Technical issues have to be considered in design: Technical issues have to be considered in design:

erosion and corrosion, slagging and fouling of he erosion and corrosion, slagging and fouling of he ating surfaces. ating surfaces.

Lower plant efficiency than in large Lower plant efficiency than in large plantplant (scale ef (scale effects)fects)

10The features of a small ( MWe) power plann

DefinitionDefinition:: simultaneous combustion of dif simultaneous combustion of dif ferent fuels in the same boiler ferent fuels in the same boiler..

ObjectiveObjective: : to achieve emission reductions. to achieve emission reductions. This is This is

not only accomplished by replacing fossi not only accomplished by replacing fossi l fuel with biomass, l fuel with biomass,

but also as a result of the interaction of f but also as a result of the interaction of f uel reactants of different origin, e.g. bio uel reactants of different origin, e.g. bio

mass and coal. mass and coal.

Co-firingCo-firing

Emission reduction

Attitude to co-firingAttitude to co-firing

One regards coal as the problemOne regards coal as the problem

(carbon dioxide).(carbon dioxide). The other attitude sees coal as the The other attitude sees coal as the

solutionsolution

(more stable combustion (more stable combustion characteristics).characteristics).

But both attitudes are environmentally But both attitudes are environmentally sound.sound.

Co-firing: meritsCo-firing: merits

Some biomass fuels can be grown on Some biomass fuels can be grown on redundant agricultural or set-aside redundant agricultural or set-aside land, improving local economics and land, improving local economics and creating jobs.creating jobs.

Increased plant flexibility in terms of Increased plant flexibility in terms of fuels utilised.fuels utilised.

Improved plant economics through Improved plant economics through the use of zero/low cost fuel the use of zero/low cost fuel feedstocks.feedstocks.

Co-firing: meritsCo-firing: merits

Fuel feedstocks may be available Fuel feedstocks may be available locally, reducing transport costs.locally, reducing transport costs.

Replacement of part of the coal feed Replacement of part of the coal feed can reduce dependence on imported can reduce dependence on imported fuels and help maintain strategic fuels and help maintain strategic national reserves of coal.national reserves of coal.

Reduced emissions of main classes of Reduced emissions of main classes of pollutants through reduction in amount pollutants through reduction in amount of coal burnt. This can occur through of coal burnt. This can occur through simple dilution or via synergistic simple dilution or via synergistic reactions between biomass feedstocks reactions between biomass feedstocks and coal.and coal.

Co-firing: meritsCo-firing: merits

Several types of combustion and Several types of combustion and gasification technology may be gasification technology may be applicable to a particular applicable to a particular combination of feedstocks. these combination of feedstocks. these may include pulverised fuel, may include pulverised fuel, bubbling fluidised bed combustion bubbling fluidised bed combustion and circulating fluidised bed and circulating fluidised bed combustion.combustion.

Co-firing: demeritsCo-firing: demerits

Feedstock pre-preparation may be required. For Feedstock pre-preparation may be required. For instance, wood requires chipping, straw may instance, wood requires chipping, straw may require chopping up, etc. resulting in increased require chopping up, etc. resulting in increased energy requirements.energy requirements.

Some biomass materials have low bulk density Some biomass materials have low bulk density (e.g. straw), this resulting in the handling and (e.g. straw), this resulting in the handling and storage of large quantities of materials.storage of large quantities of materials.

Moisture content may be high, reducing overall Moisture content may be high, reducing overall plant efficiency.plant efficiency.

Depending on the feedstock, the complexity of Depending on the feedstock, the complexity of fuel feeding requirements may be increased; fuel feeding requirements may be increased; some materials can be co-fed using a single feed some materials can be co-fed using a single feed system whereas others require a separate, system whereas others require a separate, dedicated system.dedicated system.

Biomass co-firing Biomass co-firing (technology)(technology) Direct co-combustion in coal fired Direct co-combustion in coal fired

power plantpower plant Indirect co-combustion with pre-Indirect co-combustion with pre-

gasificationgasification Indirect co-combustion in gas-fired Indirect co-combustion in gas-fired

power plantpower plant Parallel co-combustion (steam side Parallel co-combustion (steam side

coupling)coupling)

Direct co-firingDirect co-firing

Direct co-firing of Direct co-firing of biomassbiomass

Two methods were developed: Blending the biomass and coal in t

he fuel handling system and feedi ng blend to the boiler

Separate fuel handling and separa te special burners for the biomass,

and thus no impact to the conventi onal coal delivery system

- -Biomass co firing via pre gas - -Biomass co firing via pre gasificationification (Indirect)(Indirect)

Indirect co-firing for gas-Indirect co-firing for gas-fired boilersfired boilers

-Parallel co combustion -Parallel co combustion- (steam side coupling)- (steam side coupling)

- Drivers of co firing biomas - Drivers of co firing biomasss nnnnnnn nnn nn nnnnnnn nn nnnnnnnnnn nnnnnnnnn nnn nn nnnnnnn nn nnnnnnnnnn nn

ses and other pollutants ses and other pollutants nn-nnnnnn nn nnnn nnnnnn n nnnn nnnnnnnn nnnnn-nnnnnn nn nnnn nnnnnn n nnnn nnnnnnnn nnn

nnnnn nnnn nnn nnnnnnnn nnnn nnn nnn nnn nnn nnnnnnn nnnn nnnnnn nnn nnnnnnnnnn nnnn nnn nnnnnnn nnnn nnnnnn nnn nnnnnnnnnn n

he use of biomass to produce electricity he use of biomass to produce electricity - Co firing biomass and coal takes advanta- Co firing biomass and coal takes advanta

ge of the high efficiencies obtainable in la ge of the high efficiencies obtainable in la - rge coal fired power plants - rge coal fired power plants

nn nnnnnn nnn nnnnnnn nnn nn nnn nnnn nnn nn nnnnnn nnn nnnnnnn nnn nn nnn nnnn nnn higher volatile content higher volatile content

Jobs creation Jobs creation

Technical barriers Technical barriers

Thermal behavior and efficiency Thermal behavior and efficiency Fouling and corrosion of the boiler Fouling and corrosion of the boiler

(alkalis, chlorine) (alkalis, chlorine) - Environmental constraints emissi - Environmental constraints emissi

onsons

Lessons learnedLessons learned

efficiencyefficiency

The combustion penalties involved in co-firing less than 20 th% biomass with coal are relative slight, verging on the non-existent.

SSlagging and fouling can be reduced lagging and fouling can be reduced with appropriate fuel blending.with appropriate fuel blending.

Co-firing provides means for Co-firing provides means for emissions reductionemissions reduction

RReducing NOeducing NOxx emissions emissions BBiomass blending decreases iomass blending decreases SO2 SO2

emissionsemissions Trace organic compoundsTrace organic compounds ParticulatesParticulates

Concluding remarks Concluding remarks

- Co firing represents a cost effective, short te- Co firing represents a cost effective, short te rm option at a large scale rm option at a large scale

Although biomass co-firing technologies can Although biomass co-firing technologies can already be considered as proven, there is already be considered as proven, there is a continuous demand for equipment with:a continuous demand for equipment with:

Lower investment and operational costLower investment and operational cost Increased fuel flexibilityIncreased fuel flexibility Lower emissionsLower emissions Increased reliability and efficiencyIncreased reliability and efficiency

Thank youThank you