CARBON DIOXIDE CAPTURE,STORAGE AND SEQUESTRATION VIVEK KUMAR
OUTLINEA. INTRODUCTION Carbon dioxide emission source About Carbon dioxide capture (CCS) Methods of CO2 capture Challenges towards CO2 captureB. CO2 STORAGEC. CO2 SEQUESTRATIOND. INDUSTRIAL APPROACH
FOSSIL FUEL??Fossil fuels are fuels formed by natural processes such as anaerobic decomposition of buried dead organisms.Levels (proved reserves) during 2005–2007 Coal: 997,748 million short tonnes (905 billion metric tonnes), 4,416 billion barrels (702.1 km3) of oil equivalent Oil: 1,119 billion barrels (177.9 km3) to 1,317 billion barrels (209.4 km3) Natural gas: 6,183–6,381 trillion cubic feet (175–181 trillion cubic metres), 1,161 billion barrels (184.6×109 m3) of oil equivalentFlows (daily production) during 2006 Coal: 18,476,127 short tonnes (16,761,260 metric tonnes), 52,000,000 barrels (8,300,000 m3) of oil equivalent per day Oil: 84,000,000 barrels per day (13,400,000 m3/d) Natural gas: 104,435 billion cubic feet (2,960 billion cubic metres), 19,000,000 barrels (3,000,000 m3) of oil equivalent per dayYears of production left in the ground with the current proved reserves and flows above Coal: 148 years Oil: 43 years Natural gas: 61 years
Carbon dioxide emission: Worldwide scenarioCarbon dioxide emissions from various fuel and technology options
Carbon Dioxide Emission source A. Power plants: Combustion of fossil fuel e.g. coal andhydrocarbons with air or oxygen, or with a combination ofoxygen and steam, such as SR (steam reforming), POX (partialoxidation) of hydrocarbons Fermentation of grain for theproduction of beer, or ethanol for spirits B. Off-gases from petroleum refineries, oxidation of ethylene,and automotive combustion C. Cement and Steel production D. Urea production and Hydrogen generation E. Natural gas wells F. Vehicular emission
Available methods for CO2 captureAbsorptionPrimary amines, including monoethanol amine (MEA) and diglycolamine (DGA).Secondary amines, including diethanol amine (DEA) and diisopropyl amine(DIPA).Tertiary amines, including triethanol amine (TEA) and methyldiethanol amine(MDEA).Cryogenic are chiefly aimed for IGCC configurations and for combustion inoxygen/recycled CO2. In this process, CO2is separated from the other gases bycondensing it out at cryogenic temperatures.Membrane based gas separation uses the difference in the interaction betweenthe membrane material and various components gases of flue gas. This selectiveaffinity for one gas causes it to permeate faster thus achieving its separation.Some examples of viable membranes materials are polymer membranes,palladium membranes, facilitated transport membranes and molecular sieves.The use of polyphenyleneoxide and polydimethyl siloxane membranes for gasseparation; polypropylene membranes for gas absorption and ceramic basedmembrane systems have their own advantages and limitations.
Gas-solid adsorption adsorb CO2on a bed of adsorbent materials such as zeolite, alumina oractivated carbon. Various techniques employed for CO2separation include-Pressure SwingAdsorption (PSA), Vacuum Pressure Swing Adsorption (VPSA), Thermal (or temperature) SwingAdsorption (TSA), Electric swing and washing processes. In PSA, CO2adsorbed on the surface isreleased by lowering the bed pressure. In VPSA, vacuum is applied to further pull the CO2out of thebed. The regeneration cycles are short (usually requiring a few seconds). In TSA, the saturated bedis heated to release the adsorbed CO2. Electric swing and washing are the commonly usedregeneration methods applied after the evolution of IGCC (Integrated Gasification Combined Cycle)supported power plants.
Summary sheet for methods of CO2 separation techniques
Practical issues towards efficient CCS ProcessFlue gas compositionRegeneration energy Why CCS not gettingFlue gas temperature commercialized?OxygenSox a) Cost of capture > Cost of FuelNox b) Environmental effectivenessFly ashSoot c) Ease of application- CCS plantWaste products performance/ Life/ maintenanceCorrosion d) Political acceptabilityCost
Challenges towards CO2 capture A. Material/AdsorbentHigh CO2 adsorption capacity-High surface area, favorable porecharacteristicsselectivity towards CO2 to capture in presence of componentgases-FunctionalizationEconomical- Low cost synthesis, inexpensive templateOperative under flue gas conditions- Thermal and HydrothermalstabilityRegenerative and capable of being operated for multicycle-Efficiency with good Mechanical stability
Adsorbents/ Materials being explored so far.....Zeolites: 13X, DDZ-70, 4A etc.Aluminophosphates (AlPO, SAPO)Silica gelActivated CarbonMesoporous adsorbents (MCM-41, SBA-15, KIT-5 etc.)Enzymatic approachAluminaLow cost adsorbents derived from flyash, rice husk and other cheap naturalsourcesHydrotalcites, metal loaded adsorbents etc.
Challenges towards CO2 capture B. Industrial acceptance 1. Cost of capture being more than the cost of fuel 2. Flexible environmental policies 3. Efficiency loss due to CO2 capture (10-25%) 4. Government policy issues 5. Unavailability of efficient techno-economical solutions towards CCS
CO2 STORAGEThe main mechanisms that trap CO2 in the subsurface are the following:—trapping as a result of the buoyancy of CO2 compared with water or brine,in structural or stratigraphic traps beneath cap rocks,—trapping as a residual saturation along the CO2 migration path within thereservoir rock,—dissolution into the native pore fluid (most commonly brine),—reaction of acidified groundwaters with mineral components of thereservoir rock, and—adsorption onto surfaces within the reservoir rock, e.g. onto thecarbonaceous macerals that are the principal components of coal.
CO2 storage: Issues1. Sedimentary basins do not occur in every country in the world. Nor are allsedimentary basins suitable for CO2 storage.2. Typical physical conditions for geological CO2 storage: One tonne of CO2 at adensity of 700 kg m−3 occupies 1.43 m3, but at 0°C and 1 atmosphere, 1 tonne of CO2occupies approximately 509 m3.3. Storage mechanisms:The main mechanisms that trap CO2 in the subsurface are the following:I) trapping as a result of the buoyancy of CO2 compared with water or brine, instructural or stratigraphic traps beneath cap rocks, ii) trapping as a residual saturationalong the CO2 migration path within the reservoir rock, iii) dissolution into the nativepore fluid (most commonly brine), iv) reaction of acidified groundwaters with mineralcomponents of the reservoir rock, and v) adsorption onto surfaces within the reservoirrock, e.g. onto the carbonaceous materals that are the principal components of coal.4. Storage capacity5. CO2 leakage
CO2 SEQUESTRATIONSequestrationTo set off or apart; separate; segregateWhy sequester CO2?Removal from atmosphere reduces the impact that anthropogenic CO2emissions has on global warming.Natural Carbon Dioxide SinksForests (terrestrial sequestration via photosynthesis)There are three major steps involved in carbon sequestration:1. Separate and capture CO2 from the flue gases and exhaust of powerplants, refineries, oil sands operation and heavy oil upgrading facilities,cement plants, steel plants, ammonia plants and other chemical plants.(EOR)2. Concentrate it for transportation to and storage in distant reservoirlocations. (In deep Ocean)3. Convert it into stable products by biological or chemical means orallow it to be absorbed by natural sinks such as terrestrial or oceanecosystem. (Chemical feedstock)
Geological SequestrationProblemsCostly to capture and separate CO2 ($65/ton)Difficult to predict CO2 movementundergroundLoss of CO2 to atmosphere???
Industrial overview and Future scope Non-carbon based energyCombustion based-Hydrogen as a fuel 2 H2 (g) + O2 (g) 2 H2O (g)-Photoelectric-Nuclear Power Costs:Time for research & development Renewable Energy Solar Geothermal Hydroelectric Wind Ocean tides Cost:Altered ecology & biodiversity Consider: Fossil fuels incur same costs
Worldwide CO2 capture statusKansai Electric Power Company and Mitsubishi Heavy Industries have been evelopingsterically hindered amines, the most well known are called KS-1 and KS-2. These amineshave the advantage of a lower circulation rate due to a higher CO2 loading differential, alower regeneration temperature and a lower heat of reaction. They are also non-corrosiveto carbon steel at 130°C in the presence of oxygen. A first commercial plant using KS-1for Petronas Fertiliser Kedah Sbn Bhd’s fertilizer plant in Malaysia has been in operationsince 1999 (Mimura et al., 2001).The membrane technology was developed by Aker Kvaerner and used in gas separationapplicationswithin the oil and gas industry (Herzog and Falk-Pedersen, 2001). Scale-upto sizes required to capture CO2 from large power plants is considered to be a difficultissue.
R&D needsR&D related to absorbents· Reduce steam consumption and temperature requirement forregenerationo More energy efficient amines required (lower energyrequirement for regeneration, lower regeneration temperature,higher concentration)o Optimise blend of amines· Reduce power consumptiono Develop amines with a higher CO2 loading that could beapplied at a higher concentration to reduce pump requirementsand equipment sizeo Optimise blend of amines· Decrease loss of amine into the flue gas or CO2o Amines with a lower vapour pressure are desirable· Reduce degradation of amineso Develop amines less sensitive to high temperature, SOx, Nox, O2o Develop inhibitors, process modifications, membranes· Develop other types of absorbents
Other R&D needsOther areas for development· Integration possibilities with power plant should be investigatedo Integration between reboiler and reclaimer and IP steamextractiono Use of heat from CO2 compression intercooling for feedwater preheatingo Find integration possibilities for use of heat from flue gas cooler, lean aminesolution cooler, reflux condenser and CO2 dryer (e.g. district heating, feedwater preheating etc.)· Reduced flue gas blower requiremento More efficient packing to reduce absorber pressure drop· Process optimisation for large scale planto Process modifications, e.g. split flow solvent process (lean and semi-leansolution)o Improve simulation tools used for optimisation to better predict performanceo Investigate possibilities for cost reductions due to economy of scale· Demonstration of long-term operational availability and reliability on afull-scale power plant using relevant fuels.
COMMERCIAL SCOPE OF CCSThe efficiency losses due to CO2 capture are relatively modest when one considersthe environmental gains, i.e., nearly 100% CO2 capture, no SOx, NOx and particulatematter emissions. In fact, both plants (NG and SG) require no smokestack. Furthermore, both plantsproduce salable byproducts: argon and nitrogen.The captured CO2 may also derive an economic revenue if it is used for enhancedoil recovery or as a chemical feedstock, or if the plant is avoiding a carbon tax. Where CCS can be utilized?1. Carbon credit2. Conversion of CO2 to useful and valuable products such as syn gas, methanol etc.3.Supply of pure CO2 to beverage industry4. CO2 heat pumps
Instruments to control carbon emissionsA. Cap and Trade schemeB. Carbon TaxC. Hybrid: Long term emission certificates coupled withcentral bank of carbonD. Baseline and CreditE. FeebateF. Emission performance standardG. CO2 purchase contract
SUMMARY1. Post-combustion carbon dioxide capture technologies can already be used undercertain conditions and pre-combustion separation uses technologies that are wellestablished in other industrial sectors, such as fertiliser generation and hydrogenproduction. However, alternative technologies are being explored to further drive downcosts and improve overall energy efficiency. New research has demonstrated how somenew methods could reduce the cost of carbon capture by 20-30 per cent whilst alsoproducing hydrogen, which could be used to fuel cars.2. Important considerations for choice of absorbent include CO 2-loading (mol CO2/molamine), high solvent concentration in the aqueous solution, heat of reaction, heat ofvaporization, reaction rate, the temperature level required for regeneration, corrosionissues and also cost.3. Adsorption > Absorption > Membrane separation > Cryogenic separation
ConclusionsSTAGE 1:Need to develop efficient adsorbents/search for a functionalmolecule1a: Evaluation of adsorption performance of adsorbents/ functionalmolecules1b: Characterization of adsorbents1c: Measurement of adsorption kinetics and equilibrium curves1d: Evaluation of adsorbent thermodynamics and dynamic (cyclic)performance(Observations in terms of: 1. Adsorption capacity, 2. Cyclic performance, 3.Heat transfer coefficient (W/m2K) optimization, 4. Specific cooling power(W/kg)and efficiency)STAGE 2: Selection of efficient coating method: 1. Dip coating, 2. Spraycoating, 3. Wet impregnation, 4. Sol-gel synthesis, 5. In-situ functionalization,6. Hydrothermal synthesis, 7. Microwave synthesis, Direct or in-situ synthesisover honeycomb substrate ( fined tubes, foams, fibres, etc), 8. Other possiblerouteSTAGE 3: Commercialization