scientific session: renewable energy sources
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Scientific Session: Renewable Energy Sources
TOWARDS NON-CARBON ENERGY
PRODUCTION: TECHNICAL AND ENVIRONMENTAL
ASSESSMENT OF ENHANCED STRATEGIES IN
CO2 PURIFICATION FOR GEOTHERMAL
POWER PLANTS
Andrea Hernández Pedrero, Maryori C. Díaz Ramírez, Víctor J. Ferreira, Ana M. López Sabirón, Ana Martínez Santamaría
Follow us:
10/10/2019, Athens
ANDREA HERNÁNDEZ PEDRERO
ResearcherEmail: [email protected]
Towards non-carbon energy production:
CONTENTS
1. Context overview
1.1. Geothermal energy
1.2. Carbon capture, utilization and storage (CCUS)
2. Scope and objectives
3. Methodology
3.1. Dehydration technology selection
3.2. Second purification stage simulation
4. Results
4.1. Parametric analysis and optimization
4.2. Standard and enhanced process comparison
5. Conclusions
Technical and environmental assessment of enhanced strategies in CO2 purification for geothermal power plantsANDREA HERNÁNDEZ PEDRERO, MARYORI C. DÍAZ RAMÍREZ, VÍCTOR J. FERREIRA, ANA M. LÓPEZ SABIRÓN, ANA MARTÍNEZ SANTAMARÍA
1. CONTEXT OVERVIEW
1.1. GEOTHERMAL ENERGY
Figure 1.Scheme of a geothermal power plant(extracted from powearthful.com)
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Figure 2. Installed geothermal power capacity in 2018 by country(adapted from statista.com)
• Geothermal energy is present in underground reservoirs of hot water, steam, brines, etc.
• Steam and hot water can be tapped to generate electricity or to heat and cool buildings directly
• Advantages:
• Renewable energy
• Always available (unaffected by weather, day/night or seasonal variations)
• Potential to mitigate climate change (no combustion process emitting CO2)
• Disadvantages:
• Low geothermal gas emissions (H2S, CO2, CH4, etc.)
• Local induced seismic events
1.2. CARBON CAPTURE, UTILIZATION AND
STORAGE (CCUS)
• CCUS technologies will play a very important role in meeting energy and climate goals
• Policy support is critical
(Image extracted from sfc.ac.uk)
Figure 4. Additional CO2 emissions reductions in the Sustainable Development Scenario (SDS) vs. New Policies scenario (NPS)
(extracted from iea.org)
Figure 3. CO2 capture rate by country (adapted from iea.org)
United States10 projectsCO2 capture: 24.85 Mtpa
Canada2 projectsCO2 capture: 2 Mtpa
Brazil1 projectCO2 capture: 1 Mtpa
Norway2 projectsCO2 capture: 1.7 Mtpa
Saudi Arabia1 projectCO2 capture: 0.8 Mtpa
China1 projectCO2 capture: 0.6 Mtpa
Australia1 projectCO2 capture: 4 Mtpa
• Scope: application of a two-stage CO2 purification technology in geothermal power plants to reduce the associated environmental impacts
• First stage: amine-based selective H2S absorption
• Second stage: dehydration and CO2 capture by cryogenic separation from the non-condensable gases (NCG)
• Focus: second purification stage
• Objectives:
• Analyse, select and design the best dehydration technology to remove water from the sweet gas and allow for the cryogenic separation of CO2 from the NCG
• Convert waste gaseous streams into value-added products (high purity CO2)
1.2. CARBON CAPTURE, UTILIZATION AND
STORAGE (CCUS)
• CCUS technologies will play a very important role in meeting energy and climate goals
• Policy support is critical
(Image extracted from sfc.ac.uk)
2. SCOPE AND OBJECTIVES
Figure 5. Dehydration technology selection chart(extracted from J. Olijhoek and B. Leeuw,
CAPEX and OPEX Considerations for Gas Dehydration Technologies, 2015)
3. METHODOLOGY
3.1. DEHYDRATION TECHNOLOGY SELECTION
• Dehydration is a well-stablished process in the natural gas industry
• Different dehydration technologies: absorption, adsorption, membranes, etc.
• Main decision factor: required dehydration level
• Cryogenic separation: high purity CO2 at -55°C
(-67°F) at 60 bar
• Hydrate formation temperature ca. -65°C (-85°F)
• Advanced glycol dehydration
• Lower costs associated
• Simple operation and maintenance
• Equipment easily automated
• Triethylene glycol (TEG) is the solvent most commonly used. Advantages:
• More easily regenerated
• Lower vapor losses
• Lower operating costs
-85°F
• Cryogenic CO2 separation: compression and refrigeration of the gas stream to conditions at which CO2 can condense
• Aspen HYSYS – CPA property package: suitable for vapor/liquid equilibria of mixtures with hydrocarbons/non-hydrocarbons/polar compounds
3.2. SECOND PURIFICATION STAGE SIMULATION
• Advanced glycol dehydration:
• Main influencing factor on dehydration level: glycol concentration
• Modification to standard dehydration: injection of dry gas in the reboiler to enhance glycol regeneration, and thus increase its concentration
Standard glycol dehydration
CO2 cryogenic separation
4. RESULTS
4.1. PARAMETRIC ANALYSIS AND OPTIMIZATION
• The second purification stage is optimized following an iterative parametric analysis in order to:
• Achieve hydrate formation temperatures of -65°C
• Minimize energy consumption
• Minimize solvent loss
• Optimized parameters
BOILING POINTS:100°C for water
vs.288°C for TEG
• The second purification stage is also simulated based on an standard dehydration
• The environmental impact associated to the second purification stage is analysed• LCA approach• Functional unit: 1 kg of absorbed water• Environmental impact method: CML IA• Results based on the relative variation with respect to
the standard dehydration
4.2. STANDARD AND ENHANCED PROCESS COMPARISON
Geothermal heat
H2S content in sour gas ≈10-1 ppm
5. CONCLUSIONS
Geothermal power plants have some gas emissions associated
Policy support for CCUS technologies is essential to achieve the ambitions of the Paris Agreement
We propose a two-stage purification technology to convert waste gaseous emissions from geothermal power plants into value-added products
The first stage consists on an amine-based absorption and reduces H2S content in the gas mixture to 0.98 ppmw
The second stage involves a dehydration process and a cryogenic separation. As a result, a CO2 stream with 99.0 % purity is produced
An enhanced glycol dehydration is required to achieve a hydrate formation temperature of -64.9°C.
The enhanced glycol dehydration reduces by 70% the impact on climate change (total CO2 eq.) with regard to the standard dehydration
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Thank you for your attention
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