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Chemical Looping Combustion

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Information about Chemical Looping Combustion

Published on March 11, 2009

Author: amolrajan

Source: slideshare.net

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

Outline: Inspiration behind the concept of CLC Process description of CLC Details of oxygen carrier Application of CLC Advantages of CLC Disadvantages of CLC Conclusion

Inspiration behind the concept of CLC

Process description of CLC

Details of oxygen carrier

Application of CLC

Advantages of CLC

Disadvantages of CLC

Conclusion

Inspiration behind the concept: Around 25 billion tons of CO2 released annually from human activities all over globe . Currently total amount of CO2 captured and stored are only a few million tons per year. Significant additional technology developments required to meet Kyoto Protocol i.e. average one-percent-per-year emission reduction by European Union. 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. Cost effectiveness of CO2 capture and sequestration plays vital role.

Around 25 billion tons of CO2 released annually from human activities all over globe .

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

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

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.

Cost effectiveness of CO2 capture and sequestration plays vital role.

CO2 emission in sector basis:

Three Main Options in Energy Conversion Process to Abate CO2

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

Chemical Looping Combustion-Introduction Flameless combustion technology requiring no direct contact between air and fuel Solid Oxygen Carrier Circulates between Oxidizer and Reducer Oxygen Carrier: Carries Oxygen and Heat Carrier picks up O2 in the Oxidizer, leaves N2 behind Carrier Burns the Fuel in the Reducer Heat produces Steam for Power Inherent separation of greenhouse gas CO2 from other flue gas components Suitable for the combustion of Natural gas (high CO2 concentration is no problem) Syn-gas (without water-gas shift) Hard coal Petroleum coke Bio gas (CO2-removal unnecessary)

Flameless combustion technology requiring no direct contact between air and fuel

Solid Oxygen Carrier Circulates between Oxidizer and Reducer

Oxygen Carrier: Carries Oxygen and Heat

Carrier picks up O2 in the Oxidizer, leaves N2 behind

Carrier Burns the Fuel in the Reducer

Heat produces Steam for Power

Inherent separation of greenhouse gas CO2 from other flue gas components

Suitable for the combustion of

Natural gas (high CO2 concentration is no problem)

Syn-gas (without water-gas shift)

Hard coal

Petroleum coke

Bio gas (CO2-removal unnecessary)

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

Block diagram of process

Chemical Reaction Involved: Fuel reactor: (2n + m)M yOx + CnH2m ® (2n + m)MyOx - 1 + mH2O + nCO2 (1) Air reactor: (2n + m)MyOx - 1 + (n + ½m)O2 ® (2n + m)MyOx (2) Net reaction: CnH2m + (n + ½m)O2 ® mH2O + nCO2 Reaction (1) is either endothermic or exothermic, depending on type of fuel and oxygen carrier, Reaction (2) is always exothermic. 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.

Reaction (1) is either endothermic or exothermic, depending on type of fuel and oxygen carrier,

Reaction (2) is always exothermic.

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.

Different possible set-ups: Fluidized bed Packed bed Rotating reactor Membrane assisted Combination of these setups

Fluidized bed

Packed bed

Rotating reactor

Membrane assisted

Combination of these setups

Oxygen Carrier: Feasible candidates-some metal oxides of the transition state metals Fe,Mn,Ni. Metal oxides are supported by an inert material. Inert material increases reactivity and helps to maintain internal structure of particles through out redox reactions. Characterization is done both for fresh and reacted species. Commonly used oxygen carriers-Fe2O3,Mn3O4,NiO.

Feasible candidates-some metal oxides of the transition state metals Fe,Mn,Ni.

Metal oxides are supported by an inert material.

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

Characterization is done both for fresh and reacted species.

Commonly used oxygen carriers-Fe2O3,Mn3O4,NiO.

Characteristics of good oxygen carrier High reactivity with fuel and oxygen Low fragmentation and abrasion Low tendency for agglomeration Low production cost and preferably being environmentally sound. Able to convert the fuel to CO2 and H2O to the highest degree possible (ideal 100%)

High reactivity with fuel and oxygen

Low fragmentation and abrasion

Low tendency for agglomeration

Low production cost and preferably being environmentally sound.

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

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

Preparation of Oxygen Carrier: Water-based slurry of metal oxide or composite material in chemical powder form(< 10-6m)& small amount of polyacrylic acid as dispersant are prepared by ball milling for 24 h. Polyvinyl alcohol is added to the slurry as binder. Spherical particles are produced by freeze granulation after spraying into liq. Nitrogen. Frozen water in particles are removed by sublimation in freeze- drier. Particles are sintered between 950-1600`C for 6h Finally they are sieved to obtain well-defined size.

Water-based slurry of metal oxide or composite material in chemical powder form(< 10-6m)& small amount of polyacrylic acid as dispersant are prepared by ball milling for 24 h.

Polyvinyl alcohol is added to the slurry as binder.

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

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

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

Finally they are sieved to obtain well-defined size.

Fresh granulated oxygen carrier

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

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

Characterization index of oxygen carriers: Degree of oxidation/conversion X=m-mred/mox-mred where m= actual mass of sample mred =mass of sample when fully reduced mox =mass of sample when fully oxidized Oxygen ratio-maximum mass fraction of the oxygen-carrier that can be used in the oxygen transfer Ro=mox-mred /mox Rate Index-Comparison of reaction rates between different oxygen-carrier as the normalized rate rate index=60*100*(dw/dt)norm Crushing strength Sintering Temperature

Degree of oxidation/conversion

Oxygen ratio-maximum mass fraction of the oxygen-carrier that can be used in the oxygen transfer

Rate Index-Comparison of reaction rates between different oxygen-carrier as the normalized rate

Crushing strength

Sintering Temperature

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

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

Continued: Graphs are different for different oxygen carriers Particles get de-fluidized at some point of reaction(indicated by circle) 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 The tendency that hard particles are less reactive is clearly seen for the iron- and manganese particles. Hard particles normally are less porous, hence less reactive. Ni oxides and Cu oxides are by far the most reactive oxygen carriers.

Graphs are different for different oxygen carriers

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

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

The tendency that hard particles are less reactive is clearly

Hard particles normally are less porous, hence less reactive.

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

Continued: Copper oxides have a disadvantage of being apt to de-fluidize and agglomerate Nickel oxides can not totally convert the fuel gases to CO2 and H2O. Reduced NiO catalyzes steam reforming and carbon formation. The reduction reactivity is faster with H2 and CO as a fuel than with CH4. Reactivity generally increases with reaction temperature. No real correlation between particle size and reactivity has been established.

Copper oxides have a disadvantage of being apt to de-fluidize and agglomerate

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

Reduced NiO catalyzes steam reforming and carbon formation.

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

Reactivity generally increases with reaction temperature.

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

Applications of CLC: Hydrogen Production Syn-gas Production Combustion of solid fuel

Hydrogen Production

Syn-gas Production

Combustion of solid fuel

Chemical looping reforming Systems: 1.autothermal chemical looping reformer system 2 . steam reforming using chemical-looping combustion Major route for production of hydrogen is through catalytic reforming of methane with steam. Hydrogen Production

Chemical looping reforming

Systems:

Major route for production of hydrogen is

Schematic diagram:

Autothermal Chemical Looping Reforming: CLR is similar to CLC 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. 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. This gas could then be converted to a mixture of pure H2 and CO2 in a low temperature shift reactor. Depending upon purity of H2 required and pressure CO2 can be removed by either absorption or adsorption processes.

CLR is similar to CLC

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.

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.

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

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

Steam reforming using chemical-looping combustion: Natural gas is converted to syngas by this process. Natural gas reacts with steam at high pressures inside tubes containing suitable catalysts. Steam reforming tubes are here placed inside fuel-reactor in a CLC unit. Reformer tubes are not heated by direct firing but rather by oxygen carrier particles in the normal CLC process. The syngas passes through a shift-reactor and a condenser before high purity H2 is obtained through pressure swing adsorption (PSA). Offgas from the PSA unit, consisting of a mixture of CH4, CO2, CO and H2, is then the feed gas to fuel reactor.

Natural gas is converted to syngas by this process.

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

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

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

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

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

CLC of Solid fuels-coal

Solid fuel combustion: Introduction of a separate gasification process. Solid fuels react indirectly with oxygen carrier, via gasification step. Char may fallow particles to air reactor => incomplete capture. Gasification slow => large residence time=> large solids inventory in fuel reactor. Less effective contact between fuel gas and oxygen carrier. Ash may reduce oxygen carrier life time. It would be an advantage if the solid fuel could be introduced directly to the fuel reactor. The fuel reactor would act both as a gasifier and as an oxidizer. A classifier would be needed between the fuel reactor and air reactor to separate fuel particles from the oxygen carriers

Introduction of a separate gasification process.

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

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

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

Less effective contact between fuel gas and oxygen carrier.

Ash may reduce oxygen carrier life time.

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

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

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

Advantages of CLC: CLC is favorable ,because of environmental impact. Potential of near-zero CO 2 emission. Cost of process is also low . CLC concept is extended to the combustion of solid fuels and CO 2 free hydrogen production. Potential 100% CO2 capture No NOx formation Small efficiency penalty at turndown No energy penalty for oxygen production and for CO2 separation

CLC is favorable ,because of environmental impact.

Potential of near-zero CO 2 emission.

Cost of process is also low .

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

Potential 100% CO2 capture

No NOx formation

Small efficiency penalty at turndown

No energy penalty for oxygen production and for CO2 separation

Disadvantage: Transport of oxygen carrier. Cyclone is required to separate the particles from hot air steam. Coking. Sulphur sensitivity. Lifetime Pressure drop

Transport of oxygen carrier.

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

Coking.

Sulphur sensitivity.

Lifetime

Pressure drop

Research going on…… Efficiency of the chemical looping cycles Stability of the process after several runs CO2 capture/power output optimization Turndown ratio CO2 capture/power output ration at 80%/ 60%/ 40%/ 20% of the maximum capacity Solving the coking issue Different membranes Reactor tubing effects Catalyst effects Tuning hydrodynamics to minimize methane-slip Maximize heat generation Maintaining a low pressure drop while avoiding laminar flow

Efficiency of the chemical looping cycles

Stability of the process after several runs

CO2 capture/power output optimization

Turndown ratio

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

Solving the coking issue

Different membranes

Reactor tubing effects

Catalyst effects

Tuning hydrodynamics to minimize methane-slip

Maximize heat generation

Maintaining a low pressure drop while avoiding laminar flow

Conclusion: CLC is fundamentally different from the major paths for CO2 capture studied, which all involve a major step of gas separation. Extensive research currently being performed and the results with respect to oxygen carrier development and prototype testing is highly promising. The process studies performed have shown high efficiencies in comparison to other capture techniques.

CLC is fundamentally different from the major paths for CO2 capture studied, which all involve a major step of gas separation.

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

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

References: Second Nordic Minisymposium on Carbon Dioxide Capture and Storage , Göteborg, October 26, 2001. available at http://www.entek.chalmers.se/anly/symp/symp2001.html Comparison of oxygen carriers for chemical looping combustion by marcus johansson,tobiyas mattison and anders lingfelt, BIBILID: 0354-9836, 10 (2006), 3, 93-107 Chemical Looping Combustion of Coal by Puneet Gupta, Luis G. Velazquez-Vargas, Fanxing Li and L.-S. Fan Hydrogen and power production with intigrated CO2 capture by chemical looping reforming by magnus rayden and lyngfelt Investigation of Chemical Looping Combustion by Solid Fuels. 1.Process Analysis by Yan Cao and Wei-Ping Pan, Energy & Fuels 2006, 20, 1836-1844 CO2 capture by means of chemical looping combustion by Didier Pavone , from the Proceedings of the COMSOL Multiphysics User's Conference 2005 Paris 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

Second Nordic Minisymposium on Carbon Dioxide Capture and Storage , Göteborg, October 26, 2001. available at http://www.entek.chalmers.se/anly/symp/symp2001.html

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

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

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

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

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

CLC-a novel combustion technology for CO2 capture by Rong Yan*, Baowen Wang, David Tee Liang, Workshop on Carbon Capture and

Thank You

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