Techno-economic and environmental assessment of electrochemical reduction of CO 2 to formic acid

Transcription

1 Conference [avnir] November the 9 th Lilliad, Lille, FRANCE Techno-economic and environmental assessment of electrochemical reduction of CO 2 to formic acid Remi CHAUVY, Nicolas MEUNIER, Diane THOMAS and Guy De WEIRELD University of Mons (Belgium) Faculty of Engineering Thermodynamics Department remi.chauvy@umons.ac.be

2 Context: Carbon capture and Utilization Residential 6% Services 3% Other* 7% Industry 18% Industry 19% Transport 23% Electricity and heat 42% Residential 11% Services 8% Other* 5% Global anthropogenic CO 2 emissions by sector (2014) [1] Total: 37 GtCO 2 * Other: agriculture/forestry, fishing, energy industries other than electricity and heat generation, and other emissions not specified elsewhere Industrial sector: 20 to 25% of total CO 2 emissions Cement sector: Largest non-combustion sources of industrial CO 2 5 to 7% of total CO 2 emissions 2/3 of released emissions come from the decarbonation step: unavoidable [1] IEA, CO 2 Emissions from fuel combustion Highlights, IEA (2015) 2

3 Context: Carbon capture and Utilization CCS/CCU CCU CO 2 capture and purification Amine scrubbing Membrane Pressure Swing Adsoption etc. Capture and Storage (CCS) Sequestration Geological storage Saline aquifers Depleted oil and gas fields In-situ mineral carbonation technology Capture and Utilization (CCU) Conversion Chemicals Mineralization (Ex-situ mineral carbonation technology) Biological Electrochemical reduction etc. Fuels methane, methanol, ethanol, etc. Intermediates & Chemicals formic acid, acrylic acid, etc. Polymers polycarbonates, etc. Inorganic and organic carbonates calcium carbonate, etc. Carbamates Carboxylates and lactones Biomass Microalgae 3

4 Selecting emerging CO 2 utilization products for short-mid-term deployment Low unit price but significant market volume Identification More than 100 conversion pathways & projects identified, described and classified STEP 1: Pre-selection Reduction of the panel to a shortlist STEP 2: Selection Multi-criteria assessment using an original double weighted matrix to select 3/4 routes that will be modelled CO 2 -based CO 2 -conversion compound process Score Urea Organic synthesis ***** Methanol Hydrogenation **** Methane Hydrogenation **** Microalgae Biological process *** Calcium Mineral carbonation *** carbonates Ethanol Microbial process ** Sodium Mineral carbonation ** carbonates Syngas Dry reforming * High unit price but low market volume CO 2 -based CO 2 -conversion compound process Score Polycarbonates Organic synthesis ***** Formic acid Electrochemical **** reduction Dimethyl Organic synthesis *** carbonate Salicylic acid Organic synthesis ** 4

5 Formic acid Utility & Applications Key points: Liquid at ambient condition (ease of storage) Efficient hydrogen storage molecule Global demand of 1 million tons/year in 2016 Commercially available in solutions of various concentrations (85-99 wt%) Generates 600 millions /year Applications: Energy storage (hydrogen storage molecule ) Chemicals (C 1 building block) Pharmaceuticals (preservative and antibacterial agent) Textiles (leather and tanning industries, etc.) University of Mons CHAUVY R. Conference avnir Lilliad, Lille, FRANCE 09/11/2017 5

6 Approach structure Cradle Material processing Use and service Raw Material Acquisition Manufacture and assembly LCA Life cycle Inventory IA Environmental burdens Process Modelling Aspen Plus Excel / Aspen Economics CAPEX & OPEX Gate to gate approach Operating parameters vary to define the most interesting parameter from environmental point of view Multi-objective optimization Retirement and recovery Multi objective optimization Grave Treatment and disposal Coupling Process Engineering tool and LCA 6

7 Separation Separation unit Membrane Electro-reduction of CO 2 into formic acid Description of the process H 2 O recycled H 2 CO 2 H 2 CO 2 recycled Mixture: CO 2, H 2 O, HCOOH, H 2 H 2 O HCOOH Formic acid 85 wt% CO2 H 2 O - Electrochemical reactor + O 2 H 2 O Process of electro-reduction of CO 2 University of Mons CHAUVY R. Conference avnir Lilliad, Lille, FRANCE 09/11/2017 7

8 Description of the process Cathode catalyst Anode catalyst Acidic conditions Catholyte + Formic acid + H 2 + CO 2 unreacted Anolyte + O 2 (g) Ion exchange membrane Catholyte + CO 2 Anolyte Basic conditions Electrochemical reactor Total H 2 O (l) + CO 2(g) HCOOH (l) +0.5 O 2(g) (main reaction) H 2 O (l) 0.5 O 2(g) + H 2(g) (side reaction) Cathode reactions CO 2 (aq) + 2H + + 2e- HCOOH 2H + + 2e- H 2 (g) Anode reactions 2H 2 O O 2 + 4H + + 4e- Cathode reactions CO 2 (aq) + H 2 O + 2e- HCOO - + OH - 2H 2 O + 2e- H 2 (g) + 2OH - Anode reaction 4OH - 2H 2 O + O 2 + 4e- 8

9 Description of the process Water-formic acid mixture: Formation of an azeotrope Requires special methods to facilitate their separation Azeotrope Equilibrium curve: ideal case Water-formic acid equilibrium curve at 1 bar 9

10 Process Simulation: Aspen Plus v9 User define model to implement the electrochemical reactor and membrane unit under Aspen Plus 1) Electrochemical reactor unit: conversion reactor together with a split separation : Efficiency: 15% [2] 2) Membrane process: split unit : H 2 /CO 2 separation efficiency: 85% [2] Separation of the water-formic acid mixture: Pressure Swing Distillation: Option 1 High-pressure separation: Option 2 Vacuum distillation Rectification adding a third component [2] A. Robledo-Diez, 2014, Life Cycle Assessment on the conversion of CO 2 to formic acid (Master Thesis). 10

11 Process Simulation Shift of the azeotrope point Option 1: Pressure Swing Distillation water formic acid 3 bar 3 bar x az(3bar) 1 bar x az(1 bar) 1 bar Option 2: High pressure Distillation water Effect of the pressure on the azeotrope 7 bar formic acid 11

12 Process Simulation: Study case BAT cement plant: Best Available Technology Production of tpd clinker (main consistuent of cement) Release tpd CO 2 1/3 due to the combustion 2/3 due to limestone calcination during the decarbonation step in the clinker burning process calcination (550 kgco 2 per t clinker) Conversion of 5% of CO 2 emissions of 1 BAT cement plant: 125 tpd CO 2 12

13 Process Simulation: Option 1 Flowsheet: Conversion of 5% of CO 2 emissions of 1 BAT cement plant Option 1: Pressure Swing Distillation Membrane unit 3 bar 125 tpd 51 tpd 35 tpd 1 bar Electrochemical reactor Formic Simulations with Aspen Plus v9 Thermodynamic model : UNIFAC- Dortmund for liquid phase, Redlich-Kwong equation of state for gaseous phase Acidic condition considered Water-formic acid separation unit 13

14 Process Simulation: Option 2 Flowsheet: Conversion of 5% of CO 2 emissions of 1 BAT cement plant Option 2: High pressure Distillation Membrane unit 7 bar 125 tpd 51 tpd 35 tpd Simulations with Aspen Plus v9 Thermodynamic model : UNIFAC- Dortmund for liquid phase, Redlich-Kwong equation of state for gaseous phase Acidic condition considered Electrochemical reactor Formic Water-formic acid separation unit 14

15 Process Simulation: Performance indicators Mass balances (tpd per t FA@85 wt% produced) Energy requirements (per t FA@85 wt% produced) Option1 Option2 CO 2 inlet (CO 2 FEED) 0.82 H 2 O inlet (H 2 OREACT H 2 OSUP) HCOOH 85%produced 1 H 2 produced O 2 produced Electricity (without elect. reactor) (MWh) Electricity (elect. reactor) [3] (MWh) Steam (reboiler) (MJ) Option1 Option Additional consideration - Technical constraints (diameter of the columns, % FA recirculated in the reactor etc.) - Energy requirements Steam reboiler Option 2 non validated Environmental burdens! [3] A. Domingues-Ramos et al., 2015, Global warming footprint of the electrochemical reduction of carbon dioxide to formate. 15

16 Environmental assessment Goal: Environmental evaluation of the process Identification of environmental burdens Comparison with fossil-based formic acid System boundaries: Gate-to-gate LCA approach Functional unit: production of 1 ton via electro-reduction CO 2 Cement plant electricity & heat supply cooling water construction materials CO 2 capture process emissions & wastes FA plant kg System boundaries Cement production Flue gas CO 2 capture CO Formic acid O kg 2 supply (MEA based) 820 kg synthesis H 2 11 kg Clinker Chemical (MEA) Chemicals Anolyte/Catholyte water supply 562 kg 16

17 Environmental assessment Allocation approach: Price based allocation Formic acid (85wt%) : 94 % Oxygen : 0.7 % Hydrogen : 5.3 % Feedstock and utility supply CO 2 supply: considered to be reused instead of being stored: no additional energy required to capture CO 2 / environmental impact of CO 2 supply neglected Water supply Electricity supply: European mix energetic ENTSO-E Heat supply: Steam generated by natural gas boiler (76%); rest of oil as feedstock Chemicals supply: HCl (catholyte), NaCl (anolyte) Infrastructures: Literature data Environmental impacts of supply processes: LCA-database EcoInvent v3.3 17

18 Environmental assessment Life cycle Inventory [3] Functional unit: production of 1 ton via electro-reduction CO 2 Infrastructure Energy Chemicals Valuable products (final products) per t FA@85 wt% Units Electrochemical Mild steel cell body reactor Tinned copper plate kg Cathode Tin granulate 1.62 kg Anode Stainless steel mesh 4.16 g Electricity 6.82 MWh Heat MJ Catholyte HCl 2.04 kg Anolyte NaCl NaCl 2.04 kg Water t CO 2 (captured) 0.82 t Formic acid 1 t Hydrogen 0.01 t Oxygen 0.45 t [3] A. Domingues-Ramos et al., 2015, Global warming footprint of the electrochemical reduction of carbon dioxide to formate. 18

19 Environmental assessment Life Cycle impact assessment : Method : ReCiPe Midpoint (H) V1.13 / Europe Climate change Ozone depletion Terrestrial acidification Freshwater Human toxicity eutrophication Water depletion Metal depletion Fossil depletion Steam Water Infrastructure Electricity Chemicals 19

20 Environmental assessment Global warming footprint (GWP) Electricity (g CO 2 eq / kwh)) Emission factors Coal Oil 704 ENTSO-E 463 Gas 406 Photovoltaics 55 Geothermal power 45 Wind power 7.3 Nuclear 6 Hydroelectricity 4 Lignite Hard coal Heavy fuel oil Steam (kg CO 2 eq / MJ) [4] Light fuel oil Fuel mix EcoInvent v Worst case scenario kg CO 2 eq per t FA NG As usual kg CO 2 eq per t FA Best case scenario 669 kg CO 2 eq per t FA Bio GWP of classical production from methyl formate: kg CO 2 eq [4] Petrescu L. et al., 2016, Life cycle analysis applied to acrylic acid production process with different fuels for steam generation. University of Mons CHAUVY R. Conference avnir Lilliad, Lille, FRANCE 09/11/

21 A way to make the process greener (& economically viable) Flowsheet: Conversion of 5% of CO 2 emissions of 1 BAT cement plant Option 1: Pressure Swing Distillation Heat integration Reduction of steam requirements at the reboiler Water consumption Reduction of water consumption Increase CO 2 solubility Reduction of environmental impacts of water-formic acid separation Reduction of the costs! 21

22 Perspectives High energy requirements to ensure the sustainability of the process BUT the integration of RE lower the environmental impacts Further investigation regarding the water-formic acid separation process in order to select the most performant option Technico-economic evaluation of the different options and optimization of the overall process Environmental assessement of the different options Aim to propose an environmentally friendly, integrated and optimized CO 2 conversion process applied to the cement sector! 22

23 Acknowledgements to the University of Mons (UMONS, Belgium) and the European Cement Research Academy (ECRA) for their technical and financial supports. Nicolas MEUNIER acknowledges the Belgian National Fund for Scientific Research (F.R.S.-FNRS). Thank you for your attention Remi CHAUVY

24 APPENDIX Cement plant: CO 2 capture CaCO3 + heat CaO + CO 2 CO2 concentrations in cement industry flue gases 20-30% (conventional cement kilns) 70-90% (oxyfuel cement kilns) 24