172 v. kumar

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172 v. kumar

  1. 1. A Presentation on Carbon Dioxide Capture and Sequestration by Adsorption on Activated Carbon Presented by Vinod Kumar Singh Ph.D. Research Scholar Guided by Dr. E. Anil Kumar Assistant Professor Discipline of Mechanical Engineering Indian Institute of Technology Indore
  2. 2. OUTLINE  Introduction CCS  Objective of the Study Significance Limitations Physical Model  Mathematical Modeling Definition  Results and Discussions  Conclusions Validation Parametric Analysis Kinetic Models Governing Equations  Scope of Future Work Discretization Equations CO2 Capture Technology Importance of AC
  3. 3. Introduction  With the rapid development of modern civilization, the widespread use of fossil fuels within the current energy infrastructure is considered as the largest source of anthropogenic emissions of CO2, which is largely responsible for global warming and climate change  The International Panel on Climate Change (IPCC) predicts that, by the year 2100, the atmosphere may contain up to 570 ppm CO2, causing a rise in the mean global temperature of around 1.9 C  CCS is not the „silver bullet‟ that in and of itself will solve the climate change problem, it is powerful addition to the portfolio of technologies that will be needed to address climate change Source: Martinez et al. (2013), IPCC (2007) and Bernstein et al. (2006) 12/11/2013 Discipline of Mechanical Engineering, IIT Indore 1
  4. 4. Table : Fossil fuel emission levels (Pounds/Billions BTU of energy input) Pollutant Natural Gas Coal Oil 117000 208000 164000 Carbon Monoxide 40 208 33 Nitrogen oxide 92 457 448 Sulphur dioxide 1 2591 1122 Particulates 7 2744 84 Mercury 0 0.016 0.007 117140 214000 165687 Carbon dioxide Total IPCC Climate Change: Impacts, Adaptation and Vulnerability 12/11/2013 Discipline of Mechanical Engineering, IIT Indore 2
  5. 5. Fig. Atmospheric CO2 concentration during 1958-2012 Source: Carbon dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy 12/11/2013 Discipline of Mechanical Engineering, IIT Indore 3
  6. 6. Significance of Carbon Sequestration (ccs) Capture and  Fossil fuels will continue to be used in absence of any fast and easy alternatives used at large scale  CCS enables to continue use of fossil fuels with reduced emissions while other alternatives are being developed  CO₂ capture technologies are commercial and widely used in industrial processes mainly in petroleum industries, ammonia processing and natural gas refining  Applied to several gas fired and coal fired boilers but at smaller scales than current power plants Source: Special Report on “Carbon dioxide capture and storage.” Chapter 3, Intergovernmental Panel on Climate Change (IPCC), (2006) 12/11/2013 Discipline of Mechanical Engineering, IIT Indore 4
  7. 7. Limitations of ccs • Small Scale: Demonstrated in several industrial applications but not yet at a modern electric power plant of capacity of as high as 500 MW • Energy Penalty & High costs involved for the implementation of CCS (CO₂ separation, compression, delivery in pipeline and injection of compressed CO₂ in geologic reservoirs) Source: IPCC (2006) 12/11/2013 Discipline of Mechanical Engineering, IIT Indore 5
  8. 8. Carbon dioxide Capture and Sequestration (CCS)
  9. 9. Definition of CCS Fossil Fuels; Biomass Air or Oxygen Power Plant or Industrial Process CO2 CO2 Capture & Compress - Post – combustion - Pre - combustion - Oxyfuel combustion CO2 Transport - Pipeline - Tanker USEFUL PRODUCTS (e.g., electricity, fuels, chemicals, hydrogen) CO2 Storage (Sequestration) - Depleted oil/gas fields - Deep Saline formations - Unmineable coal seams - Deep Ocean - Mineralization - Reuse Fig. Schematic of a CCS system, consisting of CO2 capture, transport and storage Source: Rubin, E.S. (2010) 12/11/2013 Discipline of Mechanical Engineering, IIT Indore 6
  10. 10. Fig. Schematic CO2 Capture Options (Source: Figuerea et al. (2008)) 12/11/2013 Discipline of Mechanical Engineering, IIT Indore 7
  11. 11. CO2 Capture Technologies CO2 Separation and Capture Absorption Chemical Adsorption Cryogenics Adsorber Beds Membranes Gas Separation MEA Caustic Zeolite Other Activated Carbon Polyphenyleneoxide Alumina Physical Microbial/Algal Systems Polydimethylsiloxane Gas Absorption Regeneration Method Selexol Pressure Swing Rectisol Temperature Swing Other Polypropelene Washing Ceramic Based Systems Fig. Technical options for CO2 capture (The choice of method depends strongly on the particular application) Source: Rao, A.B. et al (2002) 12/11/2013 Discipline of Mechanical Engineering, IIT Indore 8
  12. 12. Importance of Activated Carbons (AC) • High Thermal Stability • Favorable Adsorption Capacity • Wide Range of Starting Materials for Production of Activated Carbons • Leads to Lower Raw Material Costs • Large Adsorption Capacity at Elevated Pressures • Desorption can Easily be Accomplished by the Pressure Swing Approach Source: Spigarelli, B.P. et al. (2013) 12/11/2013 Discipline of Mechanical Engineering, IIT Indore 9
  13. 13. Objective of the Study  To select as a suitable adsorbents for the CO2 capture and a numerical analysis is carried out to study the rate of adsorption of the gas  A one dimensional mathematical model is proposed based on the Dubinin‟s Theory of volume filling of Micropore, and analyzed along with the unsteady heat transfer  A parametric analysis is carried out to study the effect of various crucial parameters like thickness of bed, cooling fluid temperature, supply temperature and heat transfer coefficient on the adsorption amount 12/11/2013 Discipline of Mechanical Engineering, IIT Indore 10
  14. 14. Mathematical Modeling
  15. 15. Problem Formulation And Solution Methodology Physical Model D Fig. Physical model of adsorption system 12/11/2013 Fig. Side view of the reactor bed Discipline of Mechanical Engineering, IIT Indore 11
  16. 16. Assumptions 1. 2. 3. 4. 5. 6. 7. 8. 9. Reactor is one dimensional i.e. only radial variations are considered. Variation of porosity with adsorption is negligible inside the bed. There is no swelling of the solids. Thermo-physical properties of both the gas and solid phases are constant. Local thermal equilibrium exists between the gas and solid. The gas velocities in the bed are small. Hence, the gas and solid phase have sufficient time to attain equilibrium. Carbon dioxide acts like an ideal gas inside the bed. Natural convection and radiation effects are neglected. CO2 pressure within the bed is uniform (at any given instant; no radial variations). Cooling fluid temperature is taken to be constant throughout the process with convection occurring for cooling of the bed. Other gases in stream have a very low ppm hence no effect on the adsorption of CO2 by AC. Sorption capacity of AC towards moisture is very low. 12/11/2013 Discipline of Mechanical Engineering, IIT Indore 12
  17. 17. Kinetic Model for ACs  Dubinin Astakhov (D-A) and Radushkevich (D-R) Equation Na W N ao exp W0 exp n A E0 A E0 Dubinin Astakhov Equation 2 Dubinin Radushkevich Equation Where; Na = Amount adsorbed at relative pressure P/Ps Nao = Limiting amount of gas adsorbed in micropores where W0 = NaoVm A = Thermodynamic potential RT ln (Ps/P) Eο = Characteristic energy for a given adsorbent system β = Scaling factor depending on adsorbate Wο = Micropore volume Vm = Molar volume at specified pressure and temp. Source: Stoeckli, F. et al. (1995, 2001) 12/11/2013 Discipline of Mechanical Engineering, IIT Indore 13
  18. 18. Properties of Activated Carbons S. No Name of Activated Carbon Micropore Volume Wo (cm3/g) Surface area of Micropore Smi (m2/g) Average Micropore width Lo (nm) Characteristic Energy Eo (kJ/mol) 1. PSAC (coal tar) 0.26 413 1.25 20.04 2. Commercial AC MAXSORB 30 (petroleum coke) 0.34 2250 0.97 22.5 3. ACP-750-2.0 (coconut shell) 0.40 1018 0.78 25.14 Source: Guillot, A. et al. (2001), Linares (2005) 12/11/2013 Discipline of Mechanical Engineering, IIT Indore 14
  19. 19. Empirical Relations Used to calculate the Characteristic Energy Eo (Assuming single slit shaped micropore) Source: Stoeckli, F. et al. (1995) 12/11/2013 Discipline of Mechanical Engineering, IIT Indore 15
  20. 20. Governing Equations 12/11/2013 Discipline of Mechanical Engineering, IIT Indore 16
  21. 21. Boundary Conditions 12/11/2013 Discipline of Mechanical Engineering, IIT Indore 17
  22. 22. Solution through Discretization of Equations 12/11/2013 Discipline of Mechanical Engineering, IIT Indore 18
  23. 23. Internal Node Equation 12/11/2013 Surface Node Equation Discipline of Mechanical Engineering, IIT Indore 19
  24. 24. Table: Thermophysical Properties of AC and CO2 S.N. (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) Parameter Density (Kgm-3) Specific heat (JKg-1K-1) Effective thermal conductivity (Wm-1K-1 ) Diffusivity (m2s-1) Heat of adsorption (kJmol-1) Universal gas constant (Jmol-1K-1) Characteristic Energy (KJmol-1) Scaling Factor Limiting amount adsorbed (mol) Saturation Pressure (atm) Inlet Pressure of CO2 (atm) Activated Carbon (AC) 530 0.92 0.25 Carbon Dioxide (CO2) 1.98 5e-7 15 8.314 25 0.36 0.000755 1.1 0-1 Source: Guillot, A. et al. (2001), Linares (2005), Martin, C.F. et al. (2010) 12/11/2013 Discipline of Mechanical Engineering, IIT Indore 20
  25. 25. Table: Operational parameters (* represents variable quantities) S.N. Parameter Range of Value (1) Initial temperature of bed T0* (K) (2) Diameter of the bed D* (m) (3) Cooling fluid temperature Tf *(K) 273 - 303 (4) Heat transfer coefficient h* (Wm-2K-1) 50 - 250 12/11/2013 Discipline of Mechanical Engineering, IIT Indore 313 - 373 0.15 – 0.70 21
  26. 26. Results and Discussions
  27. 27. Validation of Kinetic Model Nao = Wo/Vm (Vm = Molar Volume) T = 50 C Ps = 1.1 atm Eo = 25 kJ/mol βCO2 = 0.36 Wo = 0.4 cm3/g Vm = 530 cm3/g Average Relative Error: 2.8% Fig. Graphical comparison of Theoretical and Experimental results for stream at 40°C and 0-1 atm (Experimental values: Chang et al., 2006 ) 12/11/2013 Discipline of Mechanical Engineering, IIT Indore 22
  28. 28. Parametric study of carbon dioxide capture system
  29. 29. Radial Variations of Adsorption Amount of CO2 Fig. Radial variations of Temperature Process conditions: Initial Temperature of bed: 80 C Cooling fluid temperature: 10 C 12/11/2013 Temperature & Fig. Radial variation of Adsorption Quantity (mol kg-1 of adsorbent) Heat Transfer Coefficient: 150 W/m2K Dimensions: 0.30 m diameter Discipline of Mechanical Engineering, IIT Indore 23
  30. 30. Effect of Radius on amount of CO2 adsorbed with time • Maximum quantity of CO2 adsorbed does not vary significantly while changing the diameter • Time to reach the max. adsorbed state increases as the bed thickness is increased Fig. Variation of CO2 adsorption with time for different radii (packing density kept same) Process conditions: Initial bed temperature: 80 C Cold fluid temperature: 10 C 12/11/2013 • Bed with lesser thickness facilitates heat conduction faster • At any given time, the lower thickness bed would have cooled down more than the one with more thickness Discipline of Mechanical Engineering, IIT Indore 24
  31. 31. Effect of Cold Fluid Temperature on amount adsorbed • Higher cooling fluid temperature values, the heat is dissipated faster with more adsorbed CO2 at any given time due to the lower average bed temperatures • Time to reach maximum adsorption state does not vary significantly Fig. Variation of CO2 adsorption with cooling fluid temperature Process conditions: Initial bed temperature: 80 C Heat transfer coefficient: 150 W/m2K 12/11/2013 Discipline of Mechanical Engineering, IIT Indore 25
  32. 32. Effect of Heat transfer coefficient on amount of CO2 adsorbed with time • Maximum adsorption state is reached faster for higher „h‟ values • Amount adsorbed does not increase significantly after h = 100 W/m2K Fig. Variation of CO2 adsorption with time for different heat transfer coefficient Process conditions: Initial bed temperature: 80 C Cold fluid temperature: 10 C 12/11/2013 Discipline of Mechanical Engineering, IIT Indore 26
  33. 33. Effect of Initial Bed Temperature on amount of CO2 adsorbed with time • For higher initial temperatures, the maximum amount of CO2 adsorbed is more, though insignificant differences exists • Time to reach that state is also almost the same in all cases Fig. Variation of CO2 adsorption with different inlet bed temperatures Process conditions: Heat transfer coefficient: 150 W/m2K Cold fluid temperature: 10 C 12/11/2013 Discipline of Mechanical Engineering, IIT Indore 27
  34. 34. Conclusions
  35. 35. Conclusions 1. The adsorption model (rate as a function of temperature & pressure) for AC is best described by Dubinin‟s Theory of Volume Filling of Micropores (TVFM) 2. Lower reactor bed radii are preferred to minimize the time required to reach the maximum adsorption state although the CO2 adsorbed does not have significant differences. Hence, a bed diameter of D = 30 cm is selected 3. Higher heat transfer coefficient results in faster adsorption as well as higher amount of CO2 adsorbed. But after h = 100 Wm-2K-1, the maximum amount adsorbed tends to be the same. Hence, an „h‟ value of 150 Wm-2K-1 is selected 4. Lower cooling fluid temperature results in faster adsorption. Hence, a value of 10 C is selected for the operation 5. Higher initial bed temperature results in greater amount of CO2 adsorbed with the steady state being reached in same time. It leads to the selection of To= 353K as the preferred value. Although, temperature should not be increased to a level which tends to degrade the material of the reactor bed 12/11/2013 Discipline of Mechanical Engineering, IIT Indore 28
  36. 36. Scope for Future Work • 1D study can be extended to a 2D and 3D model followed by practical implementation to realize the real-time difficulties associated with the model • AC used in the present work have the basic form without the impregnation of basic functionalities like amines. This study can thus be used to incorporate those modifications and then analyze the system • Mathematical approach discussed in the present work can be used to carry out the comparison of different adsorbents 12/11/2013 Discipline of Mechanical Engineering, IIT Indore 29
  37. 37. THANK YOU for Your Kind Attention
  38. 38. Queries ?

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