Chemical Looping Combustion (CLC) is a combustion technology that inherently captures carbon dioxide. It involves circulating an oxygen carrier between two reactors, oxidizing the carrier in one reactor using air and then combusting the fuel with the reduced carrier in the other reactor. This produces a flue gas stream with only CO2 and H2O, avoiding the need for costly separation of CO2. CLC has advantages over other CO2 capture methods like post-combustion capture in that it has no efficiency penalty and near-zero emissions. Research is ongoing to improve oxygen carriers and reactor designs to optimize the efficiency and stability of CLC systems.

1. CHEMICAL LOOPING COMBUSTION Presented By-Group 1 Antara Chakraborty Rajan D. Lanjekar Ramesh Singh Shekher Sheelam

3. Process description of CLC

4. Details of oxygen carrier

5. Application of CLC

6. Advantages of CLC

7. Disadvantages of CLC

8. Conclusion

10. Currently total amount of CO2 captured and stored are only a few million tons per year.

11. Significant additional technology developments required to meet Kyoto Protocol i.e. average one-percent-per-year emission reduction by European Union.

12. Challenge of future energy supply not only based on renewable but also on efficient fossil fuel conversion and subsequent capture and sequestration of the greenhouse gas CO2.

13. Cost effectiveness of CO2 capture and sequestration plays vital role.

14. CO2 emission in sector basis:

15. Three Main Options in Energy Conversion Process to Abate CO2

16. Comparison of these processes Post Combustion Process Pre Combustion Process % of CO2 captured Post Combustion Process Pre Combustion Process

18. Solid Oxygen Carrier Circulates between Oxidizer and Reducer

19. Oxygen Carrier: Carries Oxygen and Heat

20. Carrier picks up O2 in the Oxidizer, leaves N2 behind

21. Carrier Burns the Fuel in the Reducer

22. Heat produces Steam for Power

23. Inherent separation of greenhouse gas CO2 from other flue gas components

25. Syn-gas (without water-gas shift)

26. Hard coal

27. Petroleum coke

28. Bio gas (CO2-removal unnecessary)

29. Schematic view: (1) Air reactor and riser (2) Cyclone (3) Fuel reactor

30. Block diagram of process

32. Reaction (2) is always exothermic.

33. The total amount of heat evolved from reaction (1) plus (2) is the same as for normal combustion where the oxygen is in direct contact with the fuel.

35. Packed bed

36. Rotating reactor

37. Membrane assisted

38. Combination of these setups

40. Metal oxides are supported by an inert material.

41. Inert material increases reactivity and helps to maintain internal structure of particles through out redox reactions.

42. Characterization is done both for fresh and reacted species.

43. Commonly used oxygen carriers-Fe2O3,Mn3O4,NiO.

45. Low fragmentation and abrasion

46. Low tendency for agglomeration

47. Low production cost and preferably being environmentally sound.

48. Able to convert the fuel to CO2 and H2O to the highest degree possible (ideal 100%)

49. Types of oxygen carrier: Category 1:Oxide based oxygen carrier Metal oxides-NiO,Fe2O3,Mn3O4, Support-Al2O3,SiO2,TiO2, Category 2:Sulphate based oxygen carrier CaSO4 SrSO4 BaSO4 (Ni/Cu/Mn/Co)Al2O4,ZrO2, MgAl2O4

51. Polyvinyl alcohol is added to the slurry as binder.

52. Spherical particles are produced by freeze granulation after spraying into liq. Nitrogen.

53. Frozen water in particles are removed by sublimation in freeze- drier.

54. Particles are sintered between 950-1600`C for 6h

55. Finally they are sieved to obtain well-defined size.

56. Fresh granulated oxygen carrier

57. Investigated oxygen carrier: Sintering Temperature( °C) Sintering Temperature( °C)

58. Investigated oxygen carrier: Sintering Temperature( °C) 40% NiO/48% NiAl2O4 + 12% Bentonite Sintering Temperature( °C)

60. Sintering Temperature

61. Crushing strength: normally increases with sintering temperature Figure. Crushing strength as a function of the sintering temperature for iron particles of different composition

62. Rate Index Vs Crushing Strength of Fe(a),Mn(b) & Ni(c) oxide:

64. Particles get de-fluidized at some point of reaction(indicated by circle)

65. Problem of de-fluidization can be avoided by using larger height/width ratio of the bed, or by simply avoiding the reduction of the particles to too low degrees of conversion

67. Ni oxides and Cu oxides are by far the most reactive oxygen carriers.

69. Nickel oxides can not totally convert the fuel gases to CO2 and H2O.

70. Reduced NiO catalyzes steam reforming and carbon formation.

71. The reduction reactivity is faster with H2 and CO as a fuel than with CH4.

72. Reactivity generally increases with reaction temperature.

73. No real correlation between particle size and reactivity has been established.

75. Syn-gas Production

76. Combustion of solid fuel

79. Schematic diagram:

81. Instead of burning the fuel, it is partially oxidized using a solid oxygen carrier and some steam to produce an undiluted stream of H2, CO, H2O and CO2.

82. Actual composition of this mixture depends upon air ratio, i.e. fraction of oxygen supplied to fuel by oxygen carriers in fuel reactor to that needed for complete oxidation.

83. This gas could then be converted to a mixture of pure H2 and CO2 in a low temperature shift reactor.

84. Depending upon purity of H2 required and pressure CO2 can be removed by either absorption or adsorption processes.

86. Natural gas reacts with steam at high pressures inside tubes containing suitable catalysts.

87. Steam reforming tubes are here placed inside fuel-reactor in a CLC unit.

88. Reformer tubes are not heated by direct firing but rather by oxygen carrier particles in the normal CLC process.

89. The syngas passes through a shift-reactor and a condenser before high purity H2 is obtained through pressure swing adsorption (PSA).

90. Offgas from the PSA unit, consisting of a mixture of CH4, CO2, CO and H2, is then the feed gas to fuel reactor.

91. CLC of Solid fuels-coal

93. Solid fuels react indirectly with oxygen carrier, via gasification step.

94. Char may fallow particles to air reactor => incomplete capture.

95. Gasification slow => large residence time=> large solids inventory in fuel reactor.

96. Less effective contact between fuel gas and oxygen carrier.

97. Ash may reduce oxygen carrier life time.

98. It would be an advantage if the solid fuel could be introduced directly to the fuel reactor.

99. The fuel reactor would act both as a gasifier and as an oxidizer.

100. A classifier would be needed between the fuel reactor and air reactor to separate fuel particles from the oxygen carriers

102. Potential of near-zero CO 2 emission.

103. Cost of process is also low .

104. CLC concept is extended to the combustion of solid fuels and CO 2 free hydrogen production.

105. Potential 100% CO2 capture

106. No NOx formation

107. Small efficiency penalty at turndown

108. No energy penalty for oxygen production and for CO2 separation

110. Cyclone is required to separate the particles from hot air steam.

111. Coking.

112. Sulphur sensitivity.

113. Lifetime

114. Pressure drop

116. Stability of the process after several runs

117. CO2 capture/power output optimization

118. Turndown ratio

119. CO2 capture/power output ration at 80%/ 60%/ 40%/ 20% of the maximum capacity

120. Solving the coking issue

121. Different membranes

122. Reactor tubing effects

123. Catalyst effects

124. Tuning hydrodynamics to minimize methane-slip

125. Maximize heat generation

126. Maintaining a low pressure drop while avoiding laminar flow

128. Extensive research currently being performed and the results with respect to oxygen carrier development and prototype testing is highly promising.

129. The process studies performed have shown high efficiencies in comparison to other capture techniques.

131. Comparison of oxygen carriers for chemical looping combustion by marcus johansson,tobiyas mattison and anders lingfelt, BIBILID: 0354-9836, 10 (2006), 3, 93-107

132. Chemical Looping Combustion of Coal by Puneet Gupta, Luis G. Velazquez-Vargas, Fanxing Li and L.-S. Fan

133. Hydrogen and power production with intigrated CO2 capture by chemical looping reforming by magnus rayden and lyngfelt

134. Investigation of Chemical Looping Combustion by Solid Fuels. 1.Process Analysis by Yan Cao and Wei-Ping Pan, Energy & Fuels 2006, 20, 1836-1844

135. CO2 capture by means of chemical looping combustion by Didier Pavone , from the Proceedings of the COMSOL Multiphysics User's Conference 2005 Paris

136. CLC-a novel combustion technology for CO2 capture by Rong Yan*, Baowen Wang, David Tee Liang, Workshop on Carbon Capture and Utilization”, August 11-12, 2008

137. Thank You