Hamburg University of Technology CO 2 Quality and Other Relevant Issues Oxyfuel Process (Post-Combustion Capture) (Pre-Combustion Capture) Introduction and Objectives of the Meeting 2 nd Working Group Meeting on CO 2 Quality and Other Relevant Issues 7 th September 2009, Cottbus A. Kather Institute of Energy Systems

CO 2 purity  Introduction ▸ What are the barriers for a successful deployment of the Oxyfuel Process? ▸ Why considering the impurities?  General Boundary Conditions of the Oxyfuel Process ▸ Flue gas recycle demand; O 2 excess; O 2 concentration  Impact of Impurities on the CO 2 Concentration ▸ Where do the impurities come from?  R&D Project COORAL ▸ Definition of required CO 2 purity  Possibilities to increase CO 2 Purity 2

CO 2 purity  Introduction ▸ What are the barriers for a successful deployment of the Oxyfuel Process? ▸ Why considering the impurities?  General Boundary Conditions of the Oxyfuel Process ▸ Flue gas recycle demand; O 2 excess; O 2 concentration  Impact of Impurities on the CO 2 Concentration ▸ Where do the impurities come from?  R&D Project COORAL ▸ Definition of required CO 2 purity  Possibilities to increase CO 2 Purity 3

What are the barriers for a successful deployment of the Oxyfuel Process?  Combustion: no problem ▸ higher oxygen content in comparison to air case ▸ enhanced NOx reduction in comparison to air case  Efficiency of overall process: very important ▸ The Oxyfuel Process is competing with other Capture Processes ▸ Oxyfuel will only succeed if its efficiency is better than Post-Combustion Capture  CO 2 Purity: very important ▸ Purities between 85% and 99.9% are achievable ▸ An increase in purity influences CAPEX, OPEX and capture rate and thus the economy of the process ▸ Oxyfuel will only succeed if its overall cost is lower than or equal as for the other capture technologies 4 ► Introduction

CO 2 purity  Introduction ▸ What are the barriers for a successful deployment of the Oxyfuel Process? ▸ Why considering the impurities?  General Boundary Conditions of the Oxyfuel Process ▸ Flue gas recycle demand; O 2 excess; O 2 concentration  Impact of Impurities on the CO 2 Concentration ▸ Where do the impurities come from?  R&D Project COORAL ▸ Definition of required CO 2 purity  Possibilities to increase CO 2 Purity 5

Why considering the impurities? Directive 2009/31/EC ( 23 April 2009) Article 12 CO 2 stream acceptance criteria and procedure 1. A CO 2 stream shall consist overwhelmingly of carbon dioxide. To this end, no waste or other matter may be added for the purpose of disposing of that waste or other matter. However, a CO 2 stream may contain incidental associated substances from the source, capture or injection process and trace substances added to assist in monitoring and verifying CO 2 migration. Concentrations of all incidental and added substances shall be below levels that would: (a) adversely affect the integrity of the storage site or the relevant transport infrastructure; (b) pose a significant risk to the environment or human health; or (c) breach the requirements of applicable Community legislation. 6 ► Introduction

Why considering the impurities?  CO 2 Purity: very important ▸ Purities between 85% and 99.9% are achievable ▸ An increase in purity influences CAPEX, OPEX and capture rate and thus the economy of the process ▸ Oxyfuel will only succeed if its overall cost is lower than other capture technologies 7 ► Introduction

Why considering the impurities?  CAPEX, OPEX and capture rate  15:30 – 17:15  Requirements for the storage site  13:15 – 15:15 ▸ Geologists must define the concentration limits ▸ Will there be different limits for different storage options?  Requirements for the transport (mainly pipeline)  11:55 – 12:20 ▸ Will there be different limits for the different transport options?  Requirements for the recycled flue gas ▸ Internal question of boiler design considerations, mainly related to corrosion  Requirements for health, safety and environmental (HSE) reasons ▸ Not subject of today’s discussion 8 ► Introduction

CO 2 purity  Introduction ▸ What are the barriers for a successful deployment of the Oxyfuel Process? ▸ Why considering the impurities?  General Boundary Conditions of the Oxyfuel Process ▸ Flue gas recycle demand; O 2 excess; O 2 concentration  Impact of Impurities on the CO 2 Concentration ▸ Where do the impurities come from?  R&D Project COORAL ▸ Definition of required CO 2 purity  Possibilities to increase CO 2 Purity 9

10 Air 15 %CO 2 6 %H 2 O 76 %N 2 3 %Ar, O 2, … 66 %CO 2 26 %H 2 O 8 %Ar, N 2, O 2, … Air Separation Unit N2N2 O 2 Oxyfuel Process – simplified process scheme Flue Gas Recycle H2OH2O 89 %CO 2 11 % N 2, Ar, O 2, … 2/3 1/3 Flue Gas Drying CO 2 Separation Unit 18 % 82 % 47 %CO 2 53 %Ar, N 2, O 2, … nearly pure CO 2 all percentages as molar percentage Coal exhaust gas 98 %CO 2 2 % N 2, Ar, O 2, NO x, SO 2 ► General Boundary Conditions of the Oxyfuel Process

11 Factors influencing the recycle requirement (I) Main boundary conditions for the boiler:  Steam temperature in the boiler wall is limited to 470 °C due to material reasons  Flue gas temperature at the exit of the combustion chamber should not exceed the temperature in the air case (slagging)  Both conditions can approximately be fulfilled (for t Recycle < 400°C) if the condition t adiabatic, Air = t adiabatic, O 2 +Recycle is used. t Recycle tO2tO2 t Coal t adiabatic 1250 °C ► General Boundary Conditions of the Oxyfuel Process

12 Factors influencing the recycle requirement (II)  Condition: t adiabatic, Air = t adiabatic, O 2 +Recycle  Underlying assumptions: t Air = 320 °C t O 2 = 25 °C t Coal = 40 °C O 2 excess: 15 % O 2 purity:98 % t Recycle tO2tO2 t Coal t adiabatic recycle demand ► General Boundary Conditions of the Oxyfuel Process

CO 2 purity  Introduction ▸ What are the barriers for a successful deployment of the Oxyfuel Process? ▸ Why considering the impurities?  General Boundary Conditions of the Oxyfuel Process ▸ Flue gas recycle demand; O 2 excess; O 2 concentration  Impact of Impurities on the CO 2 Concentration ▸ Where do the impurities come from?  R&D Project COORAL ▸ Definition of required CO 2 purity  Possibilities to increase CO 2 Purity 13

Durch konstruktive Maßnahmen zu erzielender Falschluftanteil ▸ Fuel’s nitrogen and sulfur  SO x, NO x Where do the impurities come from? ► Impact of impurities on the CO 2 concentration 14

,20,40,60,81 standardized pollutant formation rate standardized concentration (dry) Air Oxyfuel (treated recycle) Oxyfuel (untreated recycle) 15 Pollutant formation Air NO x treated SO 2 treated NO x untreated SO 2 untreated Effects: - smaller specific flue gas mass flow - increase of flue gas density - increase of water content in the flue gas ► Impact of impurities on the CO 2 concentration

16 ▸ Fuel’s nitrogen and sulfur  SO x, NO x ▸ Nearly all recycled NOx is reduced ▸ No sense to install DeNOx plant before the flue gas recirculation ▸ Only a small part of SO 2 is reduced ► Impact of impurities on the CO 2 concentration Where do the impurities come from?

17 0,001 0,01 0,1 p H 2 SO 4 in mbar 10 Air Oxyfuel SO x  higher SO x concentration due to missing nitrogen (factor 4 - 5)  SO 3 formation promoted by higher concentrations of oxygen and water  K higher acid dew point temperature of the flue gas temperature vapour pressure curve of sulphuric acid Low temperature corrosion ► Impact of impurities on the CO 2 concentration

18 76°C Untreated recycle H2OH2O to CO 2 capture O2O2 Coal 14% 347°C 100°Cfeed water preheating FGD 160°C  Elevated classifier exit temperature of 160 °C necessary (above acid dew point)  No full load operation in air case due to SCR and FGD restrictions 76°C 320°C 80°C 350°C 55% degree of dust removal in recycle P primary fan MW P secondary fan MW P FGD MW P FGD fan MW ΣP MW η gross % completely ► Impact of impurities on the CO 2 concentration

19 Treated recycle H2OH2O coal 260°C 15% 53% 350°C 320°C  Classifier exit temperature can be maintained at 100 °C  No full load operation in air case due to SCR restrictions (not FGD) 100°C 76°C P primary fan MW P secondary fan MW P FGD MW P FGD fan MW ΣP MW η gross % feed water preheating to CO 2 capture 100°C FGD 73°C O2O2 80°C ► Impact of impurities on the CO 2 concentration

20 Residual oxygen in flue gas In the Oxyfuel process the following applies for the residual oxygen in the flue gas: ▸ The smaller the recycle rate the larger the concentration of residual oxygen ▸ The concentration of residual oxygen is always significantly higher than in the air case (4.8 vs. 2.8 vol.-%, dry) % vol. % (dry) recycle rate 11 % 12 % 13 % 14 % 15 % 16 % 17 % 18 % 19 % 20 % oxygen excess for combustion residual oxygen ≈ 4,8 air case ► Impact of impurities on the CO 2 concentration

Durch konstruktive Maßnahmen zu erzielender Falschluftanteil ▸ Fuel’s nitrogen and sulfur  SO x, NO x ▸ Oxygen excess  3 – 3.5% / 4.5 – 5% O 2 -residue 21 ► Impact of impurities on the CO 2 concentration Where do the impurities come from?

Durch konstruktive Maßnahmen zu erzielender Falschluftanteil 22 ▸ Fuel’s nitrogen and sulfur  SO x, NO x ▸ Oxygen excess  3 – 3.5% / 4.5 – 5% O 2 -residue ▸ Air separation unit  98% O 2 -purity:2%Ar  95% O 2 -purity:3.8%Ar + 1.2% N 2 ► Impact of impurities on the CO 2 concentration Where do the impurities come from?

23 Energy demand for ASU and CO 2 separation Boundary conditions: capture rate = 90 %, CO 2 -purity > 96%, 87 % of oxygen delivered by ASU, South African hard coal, 2 % leakage air Overall net efficiency increase by decreased O 2 purity by approx. 2.3 %-points ► Impact of impurities on the CO 2 concentration O 2 purity - ASU technology

Durch konstruktive Maßnahmen zu erzielender Falschluftanteil 24 ▸ Fuel’s nitrogen and sulfur  SO x, NO x ▸ Oxygen excess  3 – 3.5% / 4.5 – 5% O 2 -residue ▸ Air separation unit  98% O 2 -purity:2%Ar  95% O 2 -purity:3.8%Ar + 1.2% N 2 ► Impact of impurities on the CO 2 concentration Where do the impurities come from?

25 ▸ Fuel’s nitrogen and sulfur  SO x, NO x ▸ Oxygen excess  3 – 3.5% / 4.5 – 5% O 2 -residue ▸ Air separation unit  98% O 2 -purity:2%Ar  95% O 2 -purity:3.8%Ar + 1.2% N 2 ▸ Air leakage  approx. 3 % of flue gas flow for a new conventional power plant  up to 10 % over the years for power plants in use  Air leakage is a major source of impurities and needs to be reduced by appropriate design Air Leakage ► Impact of impurities on the CO 2 concentration Where do the impurities come from?

26 Impurities in the Flue Gas  N 2, Ar ▸ Sources: oxygen, air ingress,… ▸ Inert components which have no significant impact underground ▸ Increase auxiliary power demand for liquefaction of the CO 2 (as shown above this is not very much) ▸ Removing them during air separation (to achieve purer O 2 ) increases the auxiliary power demand of the air separation unit (as shown above this is very much)  Need for optimization between air separation and CO 2 liquefaction (considering also air leakage) ► Impact of impurities on the CO 2 concentration

27  O 2, NO X, SO 2,CO, Hg, Cl ▸ May negatively influence the geological storage site by causing geochemical reactions or the transport in pipelines  The maximum permissible concentrations for these impurities are still to be defined Impurities in the Flue Gas ► Impact of impurities on the CO 2 concentration

CO 2 purity  Introduction ▸ What are the barriers for a successful deployment of the Oxyfuel Process? ▸ Why considering the impurities?  General Boundary Conditions of the Oxyfuel Process ▸ Flue gas recycle demand; O 2 excess; O 2 concentration  Impact of Impurities on the CO 2 Concentration ▸ Where do the impurities come from?  R&D Project COORAL ▸ Definition of required CO 2 purity  Possibilities to increase CO 2 Purity 28

29 COORAL CO 2- Reinheit für Abtrennung und Lagerung (CO 2 purity for capture and storage)  Partners: ▸ BGR, BAM, DBI, MLU, TUHH ▸ Industry: Alstom, E.ON, Vattenfall, EnBW, VNG  Includes the whole CO 2 chain from production to storage: Production Storage Transport Injektion I II III IV Project COORAL ► R&D project COORAL

30 COORAL - Objectives  Estimation of impurities in CO 2 (Post-Combustion, Oxyfuel, Pre-Combustion)  Possibilities to influence the CO 2 impurities by ▸ operation of the power plant ▸ CO 2 separation processes (Post-Combustion, Oxyfuel, Pre-Combustion) ▸ CO 2 treatment (mainly Oxyfuel)  Examination of the effects caused by impurities on ▸ the transport chain ▸ the injection chain ▸ the geological site (geochemical reactions)  Optimisation between economic and plant-specific demands Definition of the required CO 2 purity for capture and storage ► R&D project COORAL

Expected impurities in separated CO 2 Component Post-Combustion Oxyfuel Pre-Combustion N 2 Yes O 2 Yes (Yes) ArYes H 2 OYes NO X Yes No SO X Yes No NH 3 YesNo Hg,...NoYes H 2 No Yes H 2 SNo Yes HCNNo Yes CH 4 No Yes COYes COSNo Yes Residues from WashingYesNoYes 31 ► R&D project COORAL

Scenarios of Expected Impurities - Post-Combustion  Post I ▸ 99,93 Vol.-% CO 2 ▸ 150 ppm O 2 ▸ 450 ppm N 2 + Ar ▸ 20 ppm NO X ▸ 10 ppm SO 2 ▸ 100 ppm H 2 O ▸ 10 ppm CO  Post II ▸ 99,92 Vol.-% CO 2 ▸ 150 ppm O 2 ▸ 450 ppm N 2 + Ar ▸ 20 ppm NO X ▸ 10 ppm SO X ▸ 100 ppm H 2 O ▸ 10 ppm CO ▸ 50 ppm NH 3 *  Post III ▸ 99,81 Vol.-% CO 2 ▸ 300 ppm O 2 ▸ 900 ppm N 2 + Ar ▸ 40 ppm NO X ▸ 20 ppm SO X ▸ 600 ppm H 2 O ▸ 20 ppm CO 32 * approximation. ► R&D project COORAL

Scenarios Expected Impurities - Pre-Combustion  Selexol ▸ 97,95 Vol.-% CO 2 ▸ 1,0 Vol.-% H 2 ▸ 0,9 Vol.-% N 2 ▸ 300 ppm Ar ▸ 100 ppm H 2 S + COS ▸ 600 ppm H 2 O ▸ 400 ppm CO ▸ 100 ppm CH 4  Rectisol ▸ 99,7 Vol.-% CO 2 ▸ 20 ppm H 2 ▸ 0,21 Vol.-% N 2 ▸ 150 ppm Ar ▸ 20 ppm H 2 S + COS ▸ 10 ppm H 2 O ▸ 400 ppm CO ▸ 100 ppm CH 4 ▸ 200 ppm Methanol 33 ► R&D project COORAL

Scenarios of Expected Impurities - Oxyfuel  Oxyfuel I (Zero Emission) ▸ 85,0 Vol.-% CO 2 ▸ 4,70 Vol.-% O 2 ▸ 5,80 Vol.-% N 2 ▸ 4,47 Vol.-% Ar ▸ 100 ppm NO X ▸ 50 ppm SO 2 ▸ 20 ppm SO 3 ▸ 100 ppm H 2 O ▸ 50 ppm CO  Oxyfuel II  Oxyfuel IV (Distillation) ▸ 99,94 Vol.-% CO 2 ▸ 100 ppm O 2 ▸ 100 ppm N 2 ▸ 100 ppm Ar ▸ 100 ppm NO X ▸ 50 ppm SO 2 ▸ 20 ppm SO 3 ▸ 100 ppm H 2 O ▸ 50 ppm CO 34  Oxyfuel III (Concentration) ▸ 98,0 % CO 2 ▸ 0,67 % O 2 ▸ 0,71 % N 2 ▸ 0,59 % Ar ▸ 100 ppm NO X ▸ 50 ppm SO 2 ▸ 20 ppm SO 3 ▸ 100 ppm H 2 O ▸ 50 ppm CO ► R&D project COORAL

CO 2 purity  Introduction ▸ What are the barriers for a successful deployment of the Oxyfuel Process? ▸ Why considering the impurities?  General Boundary Conditions of the Oxyfuel Process ▸ Flue gas recycle demand; O 2 excess; O 2 concentration  Impact of Impurities on the CO 2 Concentration ▸ Where do the impurities come from?  R&D Project COORAL ▸ Definition of required CO 2 purity  Possibilities to increase CO 2 Purity 35

36 p-T-diagram for Single-Stage Cryogenic CO 2 Liquefaction ► Possibilities to increase CO 2 purity Conditions: Air leakage:2.0% O 2 -purity:99.5 % Range of interest

Impact of distillation on overall power demand for CO 2 capture 37 ► Possibilities to increase CO 2 purity CO 2 capture rate Overall power demand for CO 2 capture in MW  Consider a certain minimal temperature level (e. g. -40 °C): ▸ higher flue gas pressure necessary to achieve a similar CO 2 capture rate ▸ increase in power demand  The additional distillation reduces the efficiency of the overall power plant process by 0.2 %-pts. for a capture rate of 90 %.

CO 2 liquefaction plant photos 38 ► Possibilities to increase CO 2 purity

39 Experiments with Oxyfuel flue gas ► Possibilities to increase CO 2 purity  Oxyfuel Flue Gas: Combustion of hard coal in CO 2 mixture with 30 %vol O 2, residual oxygen ~4 %vol  Experiments at different pressure and temperature conditions ▸ Composition of vapour and liquid phase ▸ Experimental experience ▸ Sulphur and nitrous components

CO 2 purity  Introduction ▸ What are the barriers for a successful deployment of the Oxyfuel Process? ▸ Why considering the impurities?  General Boundary Conditions of the Oxyfuel Process ▸ Flue gas recycle demand; O 2 excess; O 2 concentration  Impact of Impurities on the CO 2 Concentration ▸ Where do the impurities come from?  R&D Project COORAL ▸ Definition of required CO 2 purity  Possibilities to increase CO 2 Purity 40 Thank you for your attention!

Hamburg University of Technology CO 2 Quality and Other Relevant Issues Oxyfuel Process (Post-Combustion Capture) (Pre-Combustion Capture) Introduction and Objectives of the Meeting Thank you for your attention! 2 nd Working Group Meeting on CO 2 Quality and Other Relevant Issues 7 th September 2009, Cottbus A. Kather Institute of Energy Systems