PRE-COMBUSTION CCS IGCC POWER PLANTS Vaclav NOVOTNY, Monika - - PowerPoint PPT Presentation

ALTERNATIVE UTILIZATION OF WASTE HEAT STREAMS IN PRE-COMBUSTION CCS IGCC POWER PLANTS

Vaclav NOVOTNY, Monika VITVAROVA , Michal KOLOVRATNIK Czech Technical University in Prague POWERGEN Asia 2015 Session 8: Alternative Steam Technologies

• 3. 9. 2015 Bangkok

Integrated Gasification Combined Cycle plants with Carbon Capture and Storage

• Carbon Capture and Storage – sustainable way to

utilize abundant coal

• Pre-combustion – high effeciency with perspective of

lowest efficiency penalty

• IGCC plants

 Internal waste heat streams  Upon CCS integration  Higher heat content in waste heat including low temperature heat  Additional low temperature waste heat from capture  If heat conventionally utilized – complicated inflexible system

Model Input, Reference Plants

• 250 MWe designed power output (both with and without CCS technology)
• fuel = lignite (app. 16 MJ/kg)

Negative effects of CCS

• Efficiency penalty
• Decreased flexibility
• Large amount of heat on relatively low temperature wasted

Sophisticated system of waste heat regeneration

• Heat transfer over large distance
• Decreased flexibility
• Waste heat utilization limited to high temperature heat, large

portions of low temperature heat unutilizable

IGCC IGCC - CCS Power output [MW] 250 250 Efficiency [%] 44.7 32.1 COE [c$/kWh] (25y) 6.5 9.45

Model Input, Reference Plants

Waste heat utilization

Considered as entirely independent units

• Adjacent to heat source
• Each having own cooling tower

– Organic Rankine Cycle (ORC)

• Industrial standard for WHR
• Modular design
• Higher efficiency at low temperature sources than RC

Waste heat utilization

– Absorption Power Cycle

• Temperature match of heat source during boiling and condensation
• Most known APC is Kalina Cycle, here is proposed another one based on

aqueous Lithium Bromide solution (known from absorption cooling)

• Several advantages over ORC and Kalina Cycle

– Clean water vapour in turbine – Potential for higher turbine efficiency at low power unit (high volumetric steam flow) – Potential for higher efficiency (especially heat source below 120°C)

Waste heat utilization

– Absorption Power Cycle

• Better efficiency than ORCs below 110-120°C
• Currently under development at Czech Technical University

(planned experimental rig to confirm major aspects)

Waste heat in IGCC Air Separation Unit

• Compressor intercooling and aftercooling

– Waste heat as hot water 100-200°C

Waste heat in IGCC Coal Dryer

• Fluid bed dryer (WTA type)
• Exiting mixture of air and vapours ~100°C

Waste heat in IGCC Syngas cooling

• Cooling down syngas from ~ 160°C
• High content of condensing vapours
• Clean H2 rich gas much smaller heat capacity

Waste heat in IGCC CO2 compression

• Compressor intercooling and aftercooling
• Water at temperature > 80°C

Waste heat in IGCC Flue gas from HRSG

• Flue gas leaving HRSG at ~ 100°C
• After Rectisol CO2 capture very clean (minimum of S)
• Even with 3 pressure system hard to recover heat

below 100°C

• Therefore proposed “Superbottoming“ unit after

steam cycle

Results of WHR units application

System Stream Net output [kW] WHR unit type Output of steam integration [kW] ASU Air Compressors 359 APC Oxygen compressors 2 428 ORC (Isopentane) 1 863 Coal dryer Waste vapours stream 450 APC Syngas cooling N.A. - Used for regenerative fuel preheating CO2 compression N.A. -Capture not implemented “Super-bottoming” unit Flue gas 1 685 APC Total change in plant net output 3 059 System Stream Net output [kW] WHR unit type Output of steam integration [kW] ASU Air Compressors 500 APC Oxygen compressors 3 381 ORC (Isopentane) 2 316 Coal dryer Waste vapours stream 627 APC Syngas cooling Hot syngas 10 044 ORC (Isobutane) 8 467 CO2 compression Stage 2-7 771 APC “Super-bottoming” unit Flue gas 1 324 APC Total change in plant net output 5 864

W/o CCS With CCS

IGCC - CCS IGCC Original power output [MW] 250 250 Power output with WHR [MW] 255.9 253.1 Original efficiency [%] 32.1 44.7 Efficiency with WHR [%] 34.2 45.2 Efficiency increase [p.p.] 2.1 0.5

Results of WHR units application

• Additional power output – increase in plant

efficiency

• Higher impact on CCS plant

Technical Aspects

• ORC units are available technology
• APC in research phase, but perspective
• Possible further increase of output by connecting to plant

cooling system (but brings lower autonomy of units)

• Cooling demand partially substituted by heat engines
• Possible partial application to current plants
• “Superbottoming“ for current and non CCS plants – careful for

Sulphur content

Economic Aspects

• WHR unit installing cost around 2000 $/kWe

– IGCC plant alone

• 1400-2200 $/kWe (w/o CCS)
• 1500-3200 $/kWe (w/ CCS)
• Minimal operational cost of units

Conclusion

• Application of WHR modular units into IGCC

– Improves plant flexibility – Increases efficiency (2.1 p.p. For CCS) – Decreases cost of energy (1% for CCS, 65% capacity factor)

• Effect larger for CCS plants
• For very low temperatures proposed novel

absorption power cycle

THANK YOU FOR YOU ATTENTION