Can Coal be used for Power Generation by Can Coal be used for Power Generation by an Environmentally Responsible Society?an Environmentally Responsible Society?

An Overview of “Clean Coal” TechnologiesAn Overview of “Clean Coal” Technologies

Ben BayerBen BayerNovember 20, 2006November 20, 2006

ChE 384ChE 384

U.S. Dependence on CoalU.S. Dependence on Coal

Coal Consumption Will RiseCoal Consumption Will Rise Energy usage to increase 1.1% per yearEnergy usage to increase 1.1% per year Coal usage expected to increase 53% by 2030Coal usage expected to increase 53% by 2030

Is the Pollution Avoidable?Is the Pollution Avoidable?

Burning of coal responsible for pollution (2005)Burning of coal responsible for pollution (2005)– 10,222,547 tons SO10,222,547 tons SO22 – acid rain – acid rain– 3,633,313 tons NOx – smog, smog acid rain3,633,313 tons NOx – smog, smog acid rain– 2,539,805,219 tons CO2 – greenhouse gas2,539,805,219 tons CO2 – greenhouse gas– 50 tons Hg (debatable) – developmental difficulties50 tons Hg (debatable) – developmental difficulties

““Clean” options for coal useClean” options for coal use– Current and future pollution control technologies for Current and future pollution control technologies for

traditional coal combustiontraditional coal combustion– FutureGen – Integrated Gasification Combined-Cycle FutureGen – Integrated Gasification Combined-Cycle

(IGCC) electricity generation(IGCC) electricity generation

SOSO22 Scrubbing Scrubbing SOSO22+H+H220 → H0 → H22SOSO44

Coal cleaning is insufficientCoal cleaning is insufficient Wet Flue Gas Desulfurization (FGD) is dominant Wet Flue Gas Desulfurization (FGD) is dominant

technology – “scrubs” SOtechnology – “scrubs” SO22 out of flue gas out of flue gasAbsorptionAbsorptionSO2 + H2O → H2SO3SO2 + H2O → H2SO3NeutralizationNeutralizationCaCO3 + H2SO3 → CaSO3 + CO2 + H2OCaCO3 + H2SO3 → CaSO3 + CO2 + H2OOxidationOxidationCaSO3 + ½ O2 → CaSO4CaSO3 + ½ O2 → CaSO4CrystallizationCrystallizationCaSO4 + 2H2O → CaSO4∙2H2OCaSO4 + 2H2O → CaSO4∙2H2O

SOSO22 Scrubbing – FGD Diagram Scrubbing – FGD Diagram

Potential SOPotential SO22 Emissions Emissions

10,222,547 → 10,222,547 → 3,020,000 tpy w/ 90% 3,020,000 tpy w/ 90% capturecapture

0.00E+00

2.00E+04

4.00E+04

6.00E+04

8.00E+04

1.00E+05

1.20E+05

1.40E+05

0 200 400 600 800 1000 1200

Electrical Output (MW)

SO2

Emis

sion

s (t

ons/

yr)

Uncontrolled

66%

90%

95%

99%

NOx ControlNOx Control NOx emissions responsible for ground-level NOx emissions responsible for ground-level

ozone and acid rain (HNOozone and acid rain (HNO33)) NOx is a function of the heat of combustionNOx is a function of the heat of combustion Combustion and post combustion control Combustion and post combustion control

– Combustion – low excess air, overfire air, low Combustion – low excess air, overfire air, low NOx burners, fuel reburning, flue gas NOx burners, fuel reburning, flue gas recirculationrecirculation

– Post Combustion – selective catalytic reduction Post Combustion – selective catalytic reduction (SCR) and selective non-catalytic reduction (SCR) and selective non-catalytic reduction (SNCR) (SNCR)

NOx Control OptionsNOx Control Options

3,633,313 → 477,000 tpy w/ 90% capture3,633,313 → 477,000 tpy w/ 90% capture

0.00E+00

5.00E+03

1.00E+04

1.50E+04

2.00E+04

2.50E+04

0 200 400 600 800 1000 1200

Electrical Output (MW)

NOx

Emis

sion

s (tp

y)

Uncontrolled

LEA

Low -NOx

SNCR/FGR/reburn

SCR

HAPs / COHAPs / CO22 Control Control

Hazardous Air Pollutants (HAPs) – mercury, Hazardous Air Pollutants (HAPs) – mercury, arsenic, cadmiumarsenic, cadmium– Sorbent technologies / traditional pollution Sorbent technologies / traditional pollution

control devicescontrol devices Greenhouse Gas ControlGreenhouse Gas Control

– Pure oxygen feed – membrane technologiesPure oxygen feed – membrane technologies SequestrationSequestration Feedstock Feedstock

– Microbial degradation Microbial degradation → biofuels→ biofuels

FutureGen Coal GasificationFutureGen Coal Gasification

““Zero” emissions power plantZero” emissions power plant– 45% thermal efficiency45% thermal efficiency

Integrated Gasification Combined Cycle Integrated Gasification Combined Cycle (IGCC)(IGCC)

Coal is reduced in gasifier to CO and HCoal is reduced in gasifier to CO and H22

– CO “shifted” to CO2CO “shifted” to CO2 HH22 combusted in turbine combusted in turbine

– Potential feedstockPotential feedstock

IGCC Process FlowIGCC Process Flow

Coal Gasification EmissionsCoal Gasification Emissions

Sulfur in coal reduced to HSulfur in coal reduced to H22SS– Elemental sulfur is recovered – salable productElemental sulfur is recovered – salable product– 99.4% removal efficiencies, no sludge99.4% removal efficiencies, no sludge

Nitrogen in fuel is converted to NNitrogen in fuel is converted to N22, NH, NH33, and , and small amounts of HCNsmall amounts of HCN

Metals either contained in glasslike slag or Metals either contained in glasslike slag or water stream – 10x fewer air emissionswater stream – 10x fewer air emissions

15-20% less CO15-20% less CO22 due to increased efficiencies due to increased efficiencies

ConclusionsConclusions

Pollution control is promising for new coal Pollution control is promising for new coal burning plantsburning plants– Pure oxygen research should continuePure oxygen research should continue– Metals could be problematicMetals could be problematic

FutureGen is still off in the future…FutureGen is still off in the future…– Technical difficultiesTechnical difficulties– Promising technologiesPromising technologies

QuestionsQuestions