Handbook of Chemical Looping Technology E-Book

• Herausgeber: Wiley-VCH Verlag GmbH & Co. KGaA
• Kategorie: Fachliteratur
• Sprache: Englisch

Seitenzahl: 867

Veröffentlichungsjahr: 2018

Beschreibung

This comprehensive and up-to-date handbook on this highly topical field, covering everything from new process concepts to commercial applications.
Describing novel developments as well as established methods, the authors start with the evaluation of different oxygen carriers and subsequently illuminate various technological concepts for the energy conversion process. They then go on to discuss the potential for commercial applications in gaseous, coal, and fuel combustion processes in industry.
The result is an invaluable source for every scientist in the field, from inorganic chemists in academia to chemical engineers in industry.

Leseprobe

Table of Contents

Cover

Preface

Section 1: Chemical Looping Process Concepts

Chapter 1: The Moving Bed Fuel Reactor Process

1.1 Introduction

1.2 Modes of Moving Bed Fuel Reactor Operation

1.3 Chemical Looping Reactor System Design Considerations for Moving Bed Fuel Reactors

1.4 Counter‐Current Moving Bed Fuel Reactor Applications in Chemical Looping Processes

1.5 Co‐current Moving Bed Fuel Reactor Applications in Chemical Looping Processes

1.6 Concluding Remarks

References

Chapter 2: Single and Double Loop Reacting Systems

2.1 Introduction

2.2 Reactor Types

2.3 Gas Sealing and Solids Control

2.4 Single Loop Reactors

2.5 Double (or More) Loop Reactors

2.6 Solid Fuel Reactors

2.7 Pressurized Reactors

2.8 Solid Circulation Rate

2.9 Lessons Learned

2.10 Summary

Acknowledgements

References

Chapter 3: Chemical Looping Processes Using Packed Bed Reactors

3.1 Introduction

3.2 Oxygen Carriers for Packed Bed Reactor

3.3 Chemical Looping Combustion

3.4 Chemical Looping Reforming

3.5 Other Chemical Looping Processes

3.6 Conclusions

Nomenclature

References

Chapter 4: Chemical Looping with Oxygen Uncoupling (CLOU) Processes

4.1 Introduction

4.2 Fundamentals of the CLOU Process

4.3 CLOU Reactor Design

4.4 Status of CLOU Technology Development

4.5 Future Development of CLOU Technology

References

Chapter 5: Pressurized Chemical Looping Combustion for Solid Fuel

5.1 Introduction

5.2 Coal‐Based Pressurized Chemical Looping Combustion Combined Cycle

5.3 Fundamentals and Experiments of Pressurized Chemical Looping Combustion

5.4 Direct Coal‐Fueled PCLC Demonstration in Laboratory Scale

5.5 Tech‐economic Analysis

5.6 Technical Gaps and Challenges

References

Section 2: Oxygen Carriers

Chapter 6: Regenerable, Economically Affordable Fe

2

O

3

‐Based Oxygen Carrier for Chemical Looping Combustion

6.1 Introduction

6.2 Primary Oxide Selection

6.3 Supported Single Oxides

6.4 Natural Oxide Ores

6.5 Supported Binary Oxides System

6.6 Kinetic Networks of Fe

2

O

3

‐based Oxygen Carriers

6.7 50‐kW

th

Methane/Air Chemical Looping Combustion Tests

References

Chapter 7: Oxygen Carriers for Chemical‐Looping with Oxygen Uncoupling (CLOU)

7.1 Introduction

7.2 Thermodynamics of CLOU

7.3 Overview of Experimental Investigations of CLOU Materials

7.4 Kinetics of Oxidation and Reduction of Oxygen Carriers in CLOU

7.5 Conclusions

Acknowledgment

References

Chapter 8: Mixed Metal Oxide‐Based Oxygen Carriers for Chemical Looping Applications

8.1 Overview

8.2 Mixed Oxides for Chemical Looping with Oxygen Uncoupling (CLOU)

8.3 Mixed Oxides for iG‐CLC

8.4 Mixed Oxides for Chemical Looping Reforming (CLR)

8.5 Redox Catalyst Improvement Strategies

8.6 Mixed Oxides for Other Selective Oxidation Applications

8.7 Toward Rationalizing the Design of Mixed Metal Oxides

8.8 Future Directions

References

Chapter 9: Oxygen Carrier Structure and Attrition

9.1 Introduction

9.2 Oxygen Carrier Structure

9.3 Attrition

9.4 Attrition Modeling

9.5 Experimental Testing

References

Section 3: Commercial Design Studies of CLC Systems

Chapter 10: Computational Fluid Dynamics Modeling and Simulations of Fluidized Beds for Chemical Looping Combustion

10.1 Introduction

10.2 Reactor‐Level Simulations of CLC Using CFD

10.3 Governing Equations

10.4 Eulerian–Lagrangian Simulation of a Spouted Fluidized Bed in a CLC Fuel Reactor with Chemical Reactions

10.5 Spouted Fluidized Bed Simulation Results

10.6 Eulerian–Lagrangian Simulation of a Binary Particle Bed in a Carbon Stripper

10.7 Binary Particle Bed Simulation Results

10.8 Summary and Conclusions

References

Chapter 11: Calcium‐ and Iron‐Based Chemical Looping Combustion Processes

11.1 Introduction

11.2 CLC Plant Design, Modeling, and Cost Estimation Bases

11.3 Chemical Looping Combustion Reference Plant Descriptions

11.4 Chemical Looping Combustion Reference Plant Performance

11.5 Chemical Looping Combustion Reference Plant Cost

11.6 Chemical Looping Combustion Reference Plant Performance and Cost Sensitivities

11.7 Summary and Conclusions

References

Chapter 12: Simulations for Scale‐Up of Chemical Looping with Oxygen Uncoupling (CLOU) Systems

12.1 Introduction

12.2 Process Modeling

12.3 Computational Fluid Dynamic Simulations

References

Section 4: Other Chemical Looping Processes

Chapter 13: Calcium Looping Carbon Capture Process

13.1 Introduction

13.2 Current Status of Calcium Looping Process

13.3 Strategies for Enhancing Sorbent Recyclability and Activity

References

Chapter 14: Chemical Looping of Low‐Cost MgO‐Based Sorbents for CO

2

Capture in IGCC

14.1 Introduction

14.2 MgO‐Based Sorbent

14.3 Reaction Model for Carbon Capture and Regeneration

14.4 CFD Simulations of the Regenerative Carbon Dioxide Capture Process

14.5 Preliminary Economic Assessment

Acknowledgment

References

Index

End User License Agreement

List of Tables

Chapter 01

Table 1.1 Summary of early chemical looping process development.

Table 1.2 Economic comparison of the SCL plant for H

2

production with >90% carbon capture in an IGCC configuration.

Table 1.3 Comparison of the CDCL chemical looping technology for CO

2

capture with a base amine based CO

2

capture plant.

Table 1.4 Comparative summary of capital costs and cost of methanol production for the CTS case and the conventional baseline case.

Table 1.5 Overall integrated performance of the STS process in a full‐scale gas to liquids plant.

Table 1.6 MTS system performance with CO

2

co‐injection for a natural gas flow of 15 300 kmol h

−1

, Fe

2

O

3

:CH

4

ratio of 0.33 and a CRP = 2.

Table 1.7 Material balance for the two‐reactor modular chemical looping system shown in Figure 1.23.

Table 1.8 Key experiment and simulated performance data of 10 kW

th

sub‐pilot STS reactor.

Chapter 02

Table 2.1 Unit Summary: Tabulated here are selected units from around the world that consist of a single loop or double loop design utilizing fluid beds, spouted beds, and/or risers as part of the loop with fuel inputs of 50 kW

th

and greater. The entries are sorted by thermal size.

Table 2.2 Global metal oxide reactions and combustion heat at standard conditions (298.15 K, 0.1 MPa).

Chapter 03

Table 3.1 Summary of the energy balance and plant performance for different chemical looping combustion plants.

Table 3.2 Main reactions prevailing during chemical looping for H

2

production.

Table 3.3 Overall energy balance for the PCCL concept and comparison with benchmark technologies for different plant layouts based on IGCC (left side) and natural gas (right side).

Chapter 04

Table 4.1 Oxygen carrying capacity of pure metal oxide systems based on oxidized state.

Chapter 05

Table 5.1 Chemical composition and physical property of iron‐based OCs.

Table 5.2 Proximate and ultimate analyses of coal char.

Table 5.3 Average combustion efficiency of PCLC using RM‐1.

Table 5.4 Average combustion efficiency of PCLC using RM‐2.

Table 5.5 Average combustion efficiency of PCLC using Ilmenite OC.

Table 5.6 Operation conditions for testing of 100 kW

th

PCLC unit.

Table 5.7 Chemical composition of red mud OCs (wt%).

Table 5.8 Design Coal Characteristics.

Table 5.9 Performance of study cases.

Table 5.10 UK‐CAER's PCLC‐CC performance summary.

Table 5.11 Comparison of operating parameters and economic analysis between the DOE/NETL baseline cases and the UK‐CAER's PCLC‐CC (in 2012$).

Table 5.12 The Total plant cost breakdown for the UK‐CAER's PCLC‐CC technology.

Chapter 06

Table 6.1 Thermodynamic and reaction properties of coal CLC on various metal oxides.

Table 6.2 The reaction rates and oxygen transfer capacities of natural ores in coal CLC reaction in the fifth cycle TGA tests.

Table 6.3 Analysis of extent of reduction of various ore oxygen carriers during coal CLC and methane CLC: oxygen transfer capacities were normalized by the concentration of active CuO or FeO

x

species.

Table 6.4 Direct coal CLC reaction performance of supported copper–iron metal oxides with various compositions from TGA.

Table 6.5 CLC reaction performance of various oxygen carrier materials in the 3rd, 5th, 7th, and 9th cycle TGA tests with methane.

Table 6.6 Analysis of extent of reduction of 60% CuO/bentonite, 60% Fe

2

O

3

/bentonite, 60Cu20Fe20Al, and 40Cu40Fe20Al during coal CLC and methane CLC.

Table 6.7 Kinetic models for solid‐state reactions.

Table 6.8 Parameters obtained by fitting Equation (6.15) to experimental data for different temperatures and CH

4

concentrations.

R

2

for all curve fits was greater than 0.999.

Table 6.9 Hydrodynamic and physical properties of commercially prepared CuO–Fe

2

O

3

–alumina oxygen carrier (200–600 µm, tumbling method).

Chapter 07

Table 7.1 Overview of oxygen carriers investigated for chemical‐looping with oxygen uncoupling (CLOU) in the last few years.

Chapter 08

Table 8.1 Summary of key mixed oxide oxygen carriers for CLOU.

Table 8.2 Summary of key mixed oxide oxygen carriers for iG‐CLC.

Chapter 09

Table 9.1 List of expressions for estimating the unsteady‐state rate of particulate attrition.

Table 9.2 List of expressions for estimating steady‐state rate of particulate attrition.

Chapter 10

Table 10.1 Key modeling parameters for reacting flow simulation in a CLC fuel reactor.

Table 10.2 Properties of ilmenite particles and plastic beads used by Sun et al. 2016 [61].

Table 10.3 Key modeling parameters for reacting flow simulation in the CLC fuel reactor.

Table 10.4 Number of parcels in riser after 20 s of simulation for different fluidizing velocities.

Chapter 11

Table 11.1 Reactor modeling basis.

Table 11.2 Comparison of reference plant reactor conditions and configuration features.

Table 11.3 Fe

2

O

3

‐based chemical looping combustion power plant stream table.

Table 11.4 CaSO

4

‐based chemical looping combustion power plant stream table.

Table 11.5 Reducer reactor characteristics and vessel dimensions.

Table 11.6 Oxidizer reactor characteristics and vessel dimensions.

Table 11.7 Reference power plant performance comparison.

Table 11.8 Total plant costbreakdown comparison.

Table 11.9 Fe

2

O

3

CLC initial and annual O&M expenses.

Table 11.10 CaSO

4

CLC initial and annual O&M expenses.

Table 11.11 Cost of electricity breakdown comparison.

Table 11.12 Reducer parameters.

Table 11.13 Oxidizer parameters.

Chapter 12

Table 12.1 Flow rate and composition of the exhaust gas from the fuel reactor for CLC case.

Table 12.2 Flow rate and composition of the exhaust gas from the fuel reactor for the CLOU case.

Table 12.3 Major commercial and open source particle computational fluid dynamic codes.

Table 12.4 Summary of research utilizing CFD to model chemical looping systems.

Chapter 13

Table 13.1 The facilities of calcium looping technology around the world.

Table 13.2 Physical properties of CaO derived from various precursors.

Chapter 14

Table 14.1 Preparation parameters for HD52‐P2 sorbent.

Table 14.2 Two‐fluid model governing equations based on the kinetic theory approach.

Table 14.3 Fresh MgO‐based sorbent analysis.

Table 14.4 Boundary conditions used for the two‐dimensional simulation of the CFB with reactions.

Table 14.5 Properties of Illinois #6 Coal.

Table 14.6 Operating condition of the gasifier and syngas composition.

Table 14.7 Key sorbent properties.

Table 14.8 Operating and design variables in the carbonator and riser.

Table 14.9 Carbonator and riser sizing and design conditions.

Table 14.10 Regenerator operating and design conditions.

Table 14.11 Regenerator sizing and design conditions.

Table 14.12 Heat integration parameters.

Table 14.13 Cost basis.

Table 14.14 Major cost components of the process.

List of Illustrations

Chapter 01

Figure 1.1 Conceptual design of a moving bed chemical looping processes with a counter‐current (a) and co‐current (b) fuel reactor for full fuel conversion to CO

2

/H

2

O and for fuel gasification/reforming to syngas, respectively.

Figure 1.2 Operation lines for moving bed chemical looping fuel reactor and steam reactor.

Figure 1.3 Conceptual design of the counter‐current moving bed fuel reactor for solid fuel conversion to CO

2

/H

2

O.

Figure 1.4 Syngas production purity at varying ratios of CH

4

and oxygen carrier flow in a co‐current moving bed fuel reactor (a) and a 3‐dimensional plot of the CO

2

and H

2

O input and its impact on the syngas purity (b). Both results were simulated under isothermal operation conditions at 900 °C.

Figure 1.5 Conceptual Fe

–Ti based oxygen carrier oxidation state distribution in a fluidized bed (a) and moving bed (b) fuel reactor.

Figure 1.6 Automatic solid flow devices: (a) seal pot and (b) loop seal.

Figure 1.7 Nonmechanical L‐valve and J‐valve conceptual design (a) and solids flow rate as a function of aeration gas flow rate through an L‐valve [36] (b).

Figure 1.8 Two reactor chemical looping system with moving bed fuel reactor (b) and its pressure profile (a).

Figure 1.9 (a) Comparison between the kinetic unreacted shrinking core model and the experimental data for different Fe

2

O

3

particle sizes; (b) moving bed fuel reactor model comparison with 2.5 kW

th

bench unit test run at 1.46 CO/H

2

:Fe

2

O

3

molar flow ratio.

Figure 1.10 Oxygen carrier profile at steady state operation in the fuel react at varying CH

4

:Fe

2

O

3

molar flow ratios using a 25 kW

th

sub‐pilot chemical looping reactor system operating isothermally at 975 °C.

Figure 1.11 Process flow diagram of the SCL process for H

2

production integrated into an IGCC process.

Figure 1.12 (a) Fuel reactor gas outlet composition obtained during sub‐pilot scale demonstration of the SCL process; z‐2. (b) Oxidizer outlet gas composition obtained during sub‐pilot scale demonstration of the SCL process.

Figure 1.13 Analysis of syngas‐conversion‐sensitivity with respect to Fe

2

O

3

/syngas molar flow ratio for a fluidized bed reactor and a moving bed reactor.

Figure 1.14 Photo of 250 kW

th

–3 MW

th

SCL pilot plant at NCCC (a) and sample results of the fuel reactor performance (b).

Figure 1.15 (a) Process flow diagram of CDCL process integrated a supercritical steam cycle. Items located with the blue dotted boxes indicate existing equipment in a conventional pulverized coal power plant. (b) Image of the conceptual design of a 550 MW

e

CDCL plant.

Figure 1.16 (a) Carbon conversion profile for CDCL operation, s‐2; (b) fuel reactor gas outlet composition for long‐term CDCL operation.

Figure 1.17 Photo of the 25 kW

th

sub‐pilot CDCL unit (a) and the 250 kW

th

CDCL pilot unit (b).

Figure 1.18 Sulfur balance in CDCL sub‐pilot operation with PRB coal at 950 operating temperature.

Figure 1.19 Coal to syngas process integrated in a methanol synthesis plant.

Figure 1.20 Exemplary syngas composition from CTS bench unit experiments. (a) PRB coal only. (b) PRB coal with steam and CH

4

.

Figure 1.21 MTS process for syngas generation coupled with F–T complex for producing 50 000 bpd of liquid fuel.

Figure 1.22 CRP variation as a function of steam molar input and CO

2

molar input at a natural gas flow of 15 300 kmol h

−1

, Fe

2

O

3

:C molar ratio of 0.85,

P

 = 1 atm and

T

 = 900 °C.

Figure 1.23 Chemical looping modular system for integration into a 50 000 bpd cobalt‐based F–T process.

Figure 1.24 (a) Schematic of 10 kW

th

co‐current moving bed fuel reactor test unit and (b) fuel reactor gas outlet composition profile during demonstration of the 10 kW

th

fuel reactor.

Chapter 02

Figure 2.1 Simple sketches of a fluid catalytic reactor and a single loop chemical looping reactor. The chemical looping reactor sketch was inspired by the 10 kW

th

unit at Chalmers University of Technology, Sweden, and the 10 kW

th

unit at the Department of Energy and Environment, Instituto de Carboquímica, Spain.

Figure 2.2 National Energy Technology Laboratory's 50 kW

th

chemical looping reactor.

Figure 2.3 Typical reactor types.

Figure 2.4 Riser internals proposed to increase solids concentrations, leading to increased gas/solids contact.

Figure 2.5 Non‐mechanical valves.

Figure 2.6 Single loop reactor.

Figure 2.7 Double loop reactor, 140 kW

th

unit at Technische Universitat Wien, Austria. Source: Kolbitsch et al. 2009 [13]. Reproduced with permission of American Chemical Society.

Figure 2.8 Two stage fuel reactor.

Figure 2.9 Carbon separation in a fluidized bed.

Figure 2.10 Constant pressure adiabatic temperature change from a stream of Fe

2

O

3

at 1000 °C due to reduction reactions with CH

4

, forming Fe

3

O

4

.

Chapter 03

Figure 3.1 Conventional packed bed reactor layout for chemical looping.

Figure 3.2 Schematic representation of the evolution of the (dimensionless) axial profile of (a) the gaseous reactant concentration and (b) the temperature.

Figure 3.3 Maximum solids temperature change for different active weight contents for different oxygen carrier pairs during oxidation with air (a) and reduction with hydrogen (b).

Figure 3.4 Reactor heat management strategies.

Figure 3.5 Schematic axial temperature profile along the PBR in the two‐stage packed‐bed CLC concept.

Figure 3.6 (a) Gas temperature and flow rate at the reactor outlet and (b) axial solid temperature profiles after each step.

Figure 3.7 Sequence of operation of the 14 reactors (R1–R14) during the cycle time in co‐current configuration. OX, oxidation; P, purge; RED, reduction; and HR, heat removal.

Figure 3.8 (a) Gas conditions (temperature and composition) at the reactor outlet and (b) resulting gas condition after the overall mixing with all the streams from other reactors operated in the same step.

Figure 3.9 Schematic process of chemical looping reforming with PBRs.

Figure 3.10 Chemical looping reforming integrated with H

2

, CH

3

OH, and Fischer–Tropsch processes.

Figure 3.11 Gas conditions (temperature and composition) at the reactor outlet during the complete cycle.

Figure 3.12 Axial solid temperature profiles at the end of the reduction (RED), oxidation (OX) and during the reforming (REF) phases.

Figure 3.13 (a) Chemical looping for pure H

2

production and (b) chemical looping for H

2

/N

2

production.

Figure 3.14 Isothermal breakthrough during the reduction (a) using 0.32 Nl min

−1

of syngas at 850 °C and oxidation (b).

Figure 3.15 (a) Solid temperature profile after reduction (RED) and oxidation (OX) using natural gas and (b) syngas from coal gasification.

Figure 3.16 Schematic of the Cu–Ca process.

Chapter 04

Figure 4.1 (a) Standard chemical looping combustion, which relies on gasification of char to form CO and H

2

to react with the oxygen carrier. (b) CLOU, which releases gaseous O

2

to combust the char.

Figure 4.2 Gas concentration profile for conversion of 0.1 g petroleum coke by a copper‐based CLOU carrier in a laboratory‐scale batch fluidized bed initially at 885 °C. The fluidizing gas was switched from air to nitrogen at 100 seconds and fuel was dropped into the bed at 180 seconds. The fluidizing gas was switched back to air at 520 seconds.

Figure 4.3 Equilibrium partial pressure of O

2

for the metal oxide systems CuO/Cu

2

O, Mn

2

O

3

/Mn

3

O

4

, and Co

3

O

4

/CoO.

Figure 4.4 Typical operating regions for the air and fuel reactor of a copper‐based CLOU system processing coal.

Figure 4.5 (a) Measured oxidation rate of Cu

2

O oxidation of a copper‐based CLOU oxygen carrier and (b) depiction of oxidation driving force for Cu

2

O/CuO system.

Figure 4.6 Reduction of CuO to Cu

2

O in nitrogen as a function of temperature for a CLOU oxygen carrier of 45% CuO content on zirconia. Thermogravimetric analysis data.

Figure 4.7 Resulting fuel reactor temperatures versus degree of conversion of monometallic CLOU oxygen carriers for combustion of carbon (C) and fluidization with CO

2

preheated to 400 °C. It is assumed that the support for the 60% carriers is ZrO

2

and that particles enter the fuel reactor at 913, 775, and 850 °C for the CuO, Mn

2

O

3,

and Co

3

O

4

carriers, respectively.

Figure 4.8 Oxidation of two copper‐based oxygen carriers in air at 925°C based on TGA experiments. The time required to achieve the final 10% conversion is about as long as that required to achieve the first 90% conversion.

Figure 4.9 Schematic of a loop seal below the air reactor cyclone and feeding into the fuel reactor.

Figure 4.10 TGA curves of oxygen carrier oxidation and reduction. (a) Mass increase during oxidation in air and decrease during reduction in N

2

for an oxygen carrier of 20% CuO on SiO

2

. (b) Multiple cycles of a 45% CuO on ZrO

2

oxygen carrier.

Figure 4.11 Batch fluidized bed experimental system.

Figure 4.12 Chalmers 300 W chemical looping test reactor.

Figure 4.13 1.5 kW

th

dual fluidized bed CLC reactor at CSIC‐ICB in Zaragoza, Spain.

Figure 4.14 Chalmers 10 kW chemical looping test reactor. (1) Air reactor, (2) riser, (3) cyclone, (4) fuel reactor, (5) upper and lower particle locks, (6) water seal, (7) nitrogen, (8) natural gas, (9) nitrogen, (10) air, (11) preheater, (12) heating coils, (13) finned tubes for cooling of gas streams, (14) filters, and (15) connection to chimney.

Figure 4.15 Design of CSIC‐ICB's 50 kW

th

dual fluidized bed CLC reactor. The system is designed for both conventional CLC and CLOU operation.

Figure 4.16 Schematic Vienna University of Technology 120 kW chemical looping combustion DCFB reactor.

Figure 4.17 Schematic of University of Utah 220 kW chemical looping PDU.

Figure 4.18 Photograph of University of Utah chemical looping PDU.

Chapter 05

Figure 5.1 Schematic layout of the direct coal‐fueled PCLC system.

Figure 5.2 Chemical process involved in the fuel reactor.

Figure 5.3 Coal‐based pressurized chemical looping combustion combined cycle proposed by UK‐CAER.

Figure 5.4 Oxidation rates, burnout time, and final particle temperature during Fe

3

O

4

OC regeneration.

Figure 5.5 SEM images of iron‐based OCs: (a) RM‐1, (b) RM‐2, and (c) activated ilmenite.

Figure 5.6 Reduction reactivity of different OCs with wet simulated syngas (reduced by mixing gas of 5% CO, 10% steam, and balanced Ar at 950 °C).

Figure 5.7 Fluidized and fixed bed reactor used for coal char‐fueled PCLC experiments.

Figure 5.8 Calculated minimum velocity (

U

mf

), terminal velocity (

U

t

), and superficial velocity (

U

o

) of different solid particles involved in the PCLC experiments.

Figure 5.9 Dry gas concentration profiles of CLC at 1 bar and 6 bars when using RM‐2 and PRB char.

Figure 5.10 Instantaneous rates of char gasification of CLC with RM‐2 and that of external gasification with fused Al

2

O

3

particles when using PRB char as fuel.

Figure 5.11 Instantaneous rates of char gasification of CLC with ilmenite OC and that of external gasification with fused Al

2

O

3

when using EKY char as fuel.

Figure 5.12 Average gasification rate of PCLC and external gasification at various pressures. (a) PRB Char; (b) Western Ky Char; and (c) Eastern Ky Char.

Figure 5.13 Effect of operational pressure on combustion efficiency of the WKY char‐fueled PCLC. (a) RM‐1 OC; (b) RM‐2 OC and (c) Activated ilmenite OC.

Figure 5.14 Schematic diagram of the 100 kW

th

PCLC unit at SEU, Nanjing, China (2010–2012).

Figure 5.15 The profiles of important parameters with time for coal‐fueled CLC experiment at 0.5 MPa.

Figure 5.16 Gas concentration at the outlet of FR for coal‐fueled CLC experiment at 0.5 MPa.

Figure 5.17 Carbon and gas conversion in the FR, and CO

2

capture of PCLC unit under different operational pressures.

Figure 5.18 Combustion efficiency, q3 (energy loss due to unburned gaseous phase in exist gas of the FR) and q4 (energy loss due to unburned coal) under different operational pressures.

Figure 5.19 Diagram of 50 kW

th

PCLC unit under construction at UK‐CAER.

Figure 5.20 Aspen process flow diagram of the direct coal‐fueled PCLC‐CC plant.

Figure 5.21 Specific heat capacity of red mud OC (RM‐1).

Chapter 06

Figure 6.1 TGA profile of combustion segment of coal with CuO in nitrogen.

Figure 6.2 TGA profile of oxidation segment of coal with CuO in air.

Figure 6.3 TGA profile of 10‐cycle CLC tests of 60% CuO/bentonite with methane as fuel (Reduction time: 30 minutes; oxidation time: 30 minutes; pure CH

4

).

Figure 6.4 TGA profile of 10‐cycle CLC tests of 60% Fe

2

O

3

/bentonite with pure methane as fuel (Reduction time: 30 minutes; oxidation time: 30 minutes; pure CH

4

).

Figure 6.5 TGA profile of 10‐cycle CLC tests of 60% Fe

2

O

3

/bentonite at 900 °C under screening conditions.

Figure 6.6 (a) Bench‐scale, fixed‐bed reactor test in 20% steam/Ar of coal‐limonite and (b) MS profile of bench‐scale fixed bed reactor test of coal gasification with 20% steam/He.

Figure 6.7 Thermodynamic analysis of interaction between CuO–Fe

2

O

3

–Al

2

O

3

systems.

Figure 6.8 TGA profile of five‐cycle decomposition in N

2

/oxidation reaction with (a) 60% CuO/bentonite, (b) Fe

2

O

3

/bentonite, (c) 60% CuO–20% Fe

2

O

3

/Al

2

O

3

, and (d) 40% CuO–40% Fe

2

O

3

/Al

2

O

3

.

Figure 6.9 Reduction rates of various bimetallic CuO–Fe

2

O

3

oxygen carriers with coal.

Figure 6.10 10‐cycle TGA test of methane CLC at 800 °C with various oxygen carriers prepared by physical mixing method (Reduction with 20% CH

4

/N

2

for 10 minutes; oxidation with air for 30 minutes) (a) 60% CuO/bentonite (b) 60% Fe

2

O

3

/bentonite (c) 60Cu20Fe20Al, and (d) 40Cu40Fe20Al.

Figure 6.11 30‐Cycle TGA test of methane CLC at 900 °C with 60Cu20Fe20Al prepared by physical mixing method (Reduction with 20% CH

4

/N

2

for 10 minutes; oxidation with air for 30 minutes).

Figure 6.12 TPR of (a) 60% CuO/bentonite, (b) 60% Fe

2

O

3

/bentonite (c) 60Cu20Fe20Al, and (d) 40Cu40Fe20Al with 5% CH

4

/N

2

up to 950 °C.

Figure 6.13 Photomicrographs of 60Cu20Fe20Al: Fresh, after reduction with methane, and after reoxidation (elemental mapping: copper‐green, iron‐blue, and aluminum‐red).

Figure 6.14 Activation energy values as a function of X obtained by an isothermal operation.

Figure 6.15 Schematic of NETL's 50‐kW

th

chemical looping reactor.

Figure 6.16 Summary of the NETL 50‐kW

th

operation with oxygen carrier manufactured using the tumbling method.

Figure 6.17 Detailed performance of the tumble‐manufactured carrier during autothermal operation.

Figure 6.18 Particle size distribution of fresh oxygen carrier (OC), OC collected from the air reactor (AR), and OC from the fuel reactor (FR).

Chapter 07

Figure 7.1 Principal layout of chemical‐looping with oxygen uncoupling (CLOU). The oxygen carrier is denoted by Me

x

O

y

and Me

x

O

y

−1

, where Me

x

O

y

is a metal oxide and Me

x

O

y

−1

is a metal or a metal oxide with lower oxygen content compared to Me

x

O

y

. The fuel is here carbon (C). A fluidization gas, e.g. recirculated CO

2

or steam, is most likely needed for the case of solid fuel.

Figure 7.2 The partial pressure of gas phase O

2

over the metal oxide systems CuO/Cu

2

O, Co

3

O

4

/CoO, and Mn

2

O

3

/Mn

3

O

4

as a function of temperature.

Figure 7.3 Phase diagram of (Mn

y

Fe

1−

y

)O

x

in an atmosphere with an O

2

partial pressure of 0.05 atm.

Figure 7.4 Partial pressure of oxygen as a function of temperature for a series of combined Mn‐oxides as well as pure Mn

2

O

3

/Mn

3

O

4

. Partial pressure of O

2

is calculated from the reactions (1) 6(Mn

0.8

Fe

0.2

)

2

O

3

↔ 4(Mn

0.8

Fe

0.2

)

3

O

4

 + O

2

(g), (2) (

2

/

3

)Mn

7

SiO

12

 + 4SiO

2

↔ (

14

/

3

)MnSiO

3

+ O

2

(g), (3) (

10

/

3

)MnSiO

3

 + (

2

/

3

)Mn

7

SiO

12

↔ 4Mn

2

SiO

4

 + O

2

(g).

Figure 7.5 Heat or reaction, Δ

H

, for O

2

release for different oxygen carrier materials.

Figure 7.6 Molar fractions of metals/metalloids of investigated combined manganese oxides. Symbols indicate compositions that have been investigated in the literature according to Mattisson et al. [67] (×), Azimi et al. [88] (○), Shulman et al. [68] (•), Shulman et al. [69] (△), Jing et al. [30] (◊), Frick et al. [89] (♦), Arjmand et al. [33] (Δ), Jing et al. [90] (▪), Hallberg et al. [91] (⊳), Arjmand et al. [44] (). *Several works have studied particles in the Ca–Mn binary with a similar amount of Ca and Mn, often doped with additional metals, e.g. [46, 51, 56, 92].

Figure 7.7 (a) Illustration of the Chalmers 10 kW CLC unit. (b) Fuel conversion as a function of specific fuel‐reactor bed mass in the 10 kW unit using methane with different calcium manganite oxygen carriers. The temperatures given in the legend are for the fuel reactor.

Figure 7.8 (a) Illustration of a bench‐scale continuous CLC unit. (b) Oxygen volume fraction from the fuel reactor as a function of the temperature using different calcium manganite oxygen carriers. Here, the air reactor is fluidized with air and the fuel reactor with argon.

Figure 7.9 (a) Oxygen demand as a function of the circulation index of solids from the air reactor to the fuel reactor using two combined oxides of Ca–Mn–O and Mn–Si–Ti–O and different solid fuels in the temperature range 900–950 °C. The oxygen demand is defined as the fraction of oxygen needed for complete combustion of the gases generated in the fuel reactor. (b) The volume fraction of oxygen from the fuel reactor as a function of fuel reactor temperature. Here, nitrogen is used to fluidize the fuel reactor..

Figure 7.10 The mass‐based conversion of oxygen carrier as a function of time when manganese ore (Gloria) reacts with devolatilized wood char in a batch fluidized bed reactor. The fluidizing gas was pure nitrogen. For comparison, curves are included for when the particles are exposed only to nitrogen gas..

Chapter 08

Figure 8.1 Year‐over‐year chemical looping publication counts on the general chemical looping topic (blue bars) and mixed oxide‐based oxygen carriers (yellow bars). ()

Figure 8.2 Oxygen carrier selection criteria based on equilibrium

and thermodynamic analysis.

Figure 8.3 Thermodynamic properties of various monometallic redox pairs relative to the desired

range for CLOU (between 800 and 950 °C).

Figure 8.4 Schematic of chemical looping reforming; various regeneration options are shown.

Figure 8.5 Possible elements for occupying the A‐site or the B‐site of the perovskite structures mixed oxides.

Figure 8.6 Value creation from light hydrocarbon feedstocks to potential products.

Figure 8.7 Comparison of C

2

selectivity and methane conversion of redox OCM experiments reported by 2016.

Chapter 09

Figure 9.1 Surface area as a function of pretreatment temperature of unreacted hematite [5].

Figure 9.2 Surface area of thermally pretreated and untreated hematite oxygen carrier [5].

Figure 9.3 Thermal exposure effects on hematite.

Figure 9.4 Microstructures observed during the Fe

2

O

3

 → Fe

3

O

4

transformation: (a, b) porous magnetite; (c, d) lath magnetite (Fe

2

O

3

has the lighter appearance).

Figure 9.5 Particle model concept for hematite.

Figure 9.6 Development of lath structure into hematite material.

Figure 9.7 SEM–EDX images of cross‐cut ilmenite particles (a) calcined and after (b) 16, (c) 50, and (d) 100 redox cycles.

Figure 9.8 SEM pictures of a cross section of fresh and used Cu–Al particles at different pair FR–AR temperatures and operation times.

Figure 9.9 Activation of ZrO

2

supported iron oxides under various oxidation conditions.

Figure 9.10 Summary of structural changes observed during redox reactions with CH

4

/O

2

for variously supported iron oxides.

Figure 9.11 Particle size distributions of abrasion and erosion attrition mechanisms.

Figure 9.12 Locations of attrition in a chemical looping reactor system.

Figure 9.13 Summary of abrasion and erosion expressions.

Figure 9.14 Hardness of iron oxides and an iron silicate as a function of temperature [57].

Figure 9.15 Fracture properties of α‐iron oxide from tensile stress testing.

Figure 9.16 Fracture toughness of various metallic and oxide composites of alumina.

Figure 9.17 (a) Unsteady and steady wear as a function of sliding distance. (b)Wear volume for aluminum samples.

Figure 9.18 Impact attrition device.

Figure 9.19 Grace‐Davidson jet cup attrition device.

Chapter 10

Figure 10.1 Primary energy consumption by fuel (quadrillion Btu) [2].

Figure 10.2 Schematic representation of a chemical‐looping combustion system with (a) interconnected fluidized beds and (b) packed bed with alternating flow [5].

Figure 10.3 Schematic of particle collision model for DEM [42].

Figure 10.4 Reacting particle in the multiple surface reactions model [42].

Figure 10.5 Geometry outline with pressure taps, mesh, and wireframe of the CLC fuel reactor.

Figure 10.6 Particle tracks colored by velocity magnitude in reacting flow with F60AM1100 particles.

Figure 10.7 Static pressure at pressure taps P1–P5 in the CLC fuel reactor of Figure 10.5 at

t

 = 400 ms (a), 800 ms (b), 1200 ms (c), and 1600 ms (d) in reacting flow.

Figure 10.8 Particle tracks colored by mass fraction of Fe

3

O

4

relative to original mass of Fe

2

O

3

.

Figure 10.9 Contours of CO

2

mass fraction produced by reaction of Fe

2

O

3

with CH

4

.

Figure 10.10 Size difference between particles of coal and ilmenite used in coal‐direct CLC.

Figure 10.11 Schematic of riser‐based carbon stripper used by Sun et al. 2016 [61]. Reproduced with permission of American Chemical Society.

Figure 10.12 Effect of fluidizing velocity on the separation efficiency

λ

for a solids mass flux of 12.2 kg m

−2

‐s. Source: Sun et al. 2016 [61]. Reproduced with permission of American Chemical Society.

Figure 10.13 Geometry with detailed views used for CFD‐DEM simulation of the experiment of Sun et al. 2016 [61]. Reproduced with permission of American Chemical Society.

Figure 10.14 Static pressure at 2 mm for binary particle bed simulation with fluidizing velocity

u

g

 = 1.50 m s

−1

.

Figure 10.15 Plastic beads flow rate out of top of the riser for different fluidizing velocities.

Figure 10.16 Ilmenite flow rate out of top of the riser for different fluidizing velocities.

Figure 10.17 Ilmenite flow rate into bottom collection tank for different fluidizing velocities.

Figure 10.18 Effect of fluidizing velocity on separation ratio

λ

for a solids mass flux of 12.2 kg m

−2

‐s in the CFD‐DEM simulation of the riser‐based carbon stripper compared against the experiment of Sun et al. 2016 [61]. Reproduced with permission of American Chemical Society.

Chapter 11

Figure 11.1 Reference CLC power plant block flow configuration.

Figure 11.2 Fe

2

O

3

‐based chemical looping combustion power plant stream flow diagram

Figure 11.3 CaSO

4

‐based chemical looping combustion power plant stream flow diagram.

Figure 11.4 Reducer temperature sensitivity.

Figure 11.5 Oxidizer temperature sensitivity.

Figure 11.6 Reducer velocity sensitivity.

Figure 11.7 Oxidizer velocity sensitivity.

Figure 11.8 Carbon gasification efficiency sensitivity.

Figure 11.9 Reducer oxygen carrier conversion sensitivity.

Figure 11.10 Oxygen carrier makeup and price sensitivity.

Figure 11.11 Char–carrier separator device cost sensitivity.

Chapter 12

Figure 12.1 Schematic representation of CLOU system.

Figure 12.2 Aspen Plus process flow sheet for CLC.

Figure 12.3 Aspen Plus process flow sheet for CLOU.

Figure 12.4 Comparative operating costs for CLC versus CLOU.

Figure 12.5 Representation of the novel fuel reactor system studied.

Figure 12.6 Temperature difference between reactors for autothermal operation for CLOU system. Allothermal regions are also shown.

Figure 12.7 The difference between the MP‐PIC and coarse‐grain DEM approach. In the MP‐PIC methodology (left), five spherical particles having diameter of one unit are represented by a single parcel having diameter of one unit and statistical weight equal to five. In the coarse‐grain DEM method, the particles are represented by one larger spherical parcel having diameter of 5

1/3

units.

Figure 12.8 Instantaneous concentration profile at a residence time of 15 seconds of a batch fuel reactor utilizing nickel as the oxygen carrier and methane as the fuel.

Figure 12.9 Gas phase concentration profile of CO

2

and CO comparing simulations and experimental work.

Figure 12.10 Residence time as a function of solid recirculation rate [25]. Data versus simulation predictions are shown.

Figure 12.11 Conditions at 40 seconds (a) Particle volume fraction, (b) coal char fraction, (c) particle radius, (d) CO

2

mole fraction. Fuel reactor is on the left.

Chapter 13

Figure 13.1 Schematic diagram of calcium looping process.

Figure 13.2 Comparisons of carbonation conversion over multiple carbonation–calcination cycles for experiments conducted using different types of limestones.

Figure 13.3 The thermodynamic curve for the carbonation of CaO.

Figure 13.4 (a) Schematic and (b) view of 3 kW

th

bench‐scale system at ITRI.

Figure 13.5 Photo of 120 kW –calcination reaction (CCR) process facility for CO

2

and SO

2

capture at Ohio State University initiated in 2005 with coal‐fired stoker, rotary calciner, and entrained bed carbonator shown and with the same facility used also for Carbonation–Calcium–Hydration Cyclic Process operation.

Figure 13.6 200 kW

th

calcium looping system at University of Stuttgart.

Figure 13.7 (a) View and (b) schematic of La Robla 300 kW

th

facility.

Figure 13.8 75 kW

th

calcium looping system developed by CANMET Energy.

Figure 13.9 (a) View and (b) schematic of 1 MW

th

TU Darmstadt pilot plant.

Figure 13.10 (a) View and (b) schematic of La Pereda 1.7 MW

th

facility.

Figure 13.11 (a) View of 1.9 MW

th

and 500 kW

th

facilities; (b) schematic of 500 kW

th

cascade cyclone system.

Figure 13.12 Scheme of textural transformation of the CaO sorbent in calcination–carbonation cycles.

Figure 13.13 Sorbent (a)

scanning electron microscope

(

SEM

) image of CaAc

2

–CaO; (b) CO

2

uptake capacity of CaAc

2

–CaO.

Figure 13.14 CO

2

adsorption capacity of CaO doped with alkali metals.

Figure 13.15 Mechanism of Ca

12

Al

14

O

33

/CaO preparation.

Figure 13.16 (a) The reaction scheme of the formation of Ca

3

Al

2

O

6

[62]; (b) the formation mechanism of the aluminum‐stabilized calcium‐based sorbents under various calcination temperatures.

Figure 13.17 CO

2

uptake capacity of sorbents synthesized using various Ca

2+

/Al

3+

ratios and precursors.

Figure 13.18 Schematic representation of the sorbent morphology under various reaction environments: (a) no steam present; (b) steam present during carbonation only; (c) steam during calcination only; and (d) steam present for carbonation and calcination.

Figure 13.19 Process flow diagram of a calcium looping process integrated into a 500 MW

e

coal‐fired power plant.

Figure 13.20 Schematic diagram of a recarbonation‐integrated calcium looping process.

Chapter 14

Figure 14.1 Schematic diagram of a circulating fluidized bed (CFB) loop.

Figure 14.2 Schematic diagram of the high‐pressure packed bed unit.

Figure 14.3 Effect of K/Mg ratio on the capacity of the sorbent.

Figure 14.4 Effect of temperature on the absorption reactivity of the HD52‐P2 sorbent.

Figure 14.5 Effect of steam on sorbent reactivity and capacity.

Figure 14.6 Effect of temperature on regeneration reaction.

Figure 14.7 Schematic diagram of expanded particle.

Figure 14.8 VDM fit to carbonation reaction data (dry carbonation).

Figure 14.9 VDM fit to carbonation reaction data (10 mol% steam).

Figure 14.10 Schematic diagram of regenerated particle.

Figure 14.11 Shrinking core model fit to regeneration reaction data.

Figure 14.12 Geometry and initial solid volume fraction in the two dimensional circulating fluidized bed (CFB) loop.

Figure 14.13 Contours of CO

2

mole fraction in the system as a function of time.

Figure 14.14 Contours of instantaneous solid volume fraction and CO

2

mole fraction in the CO

2

absorber (fluidized bed No. 1) at

t

 = 20 seconds, for a solid circulation rate of 220 g s

−1

. ()

Figure 14.15 Comparison of generated CO

2

mole fraction as a function of time at two different pressures of 50 and 20 atm. ()

Figure 14.16 Heat integration scheme in the process.

Guide

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E1

Handbook of Chemical Looping Technology

Edited by Ronald W. Breault

Copyright

Editor

Dr. Ronald W. Breault

National Energy Technology Laboratory

3610 Collins Ferry Road

Morgantown, WV 26507

USA

Cover: © John Wiley & Sons, Inc.

All books published by Wiley–VCH are carefully produced. Nevertheless, authors, editors, and publisher do not warrant the information contained in these books, including this book, to be free of errors. Readers are advised to keep in mind that statements, data, illustrations, procedural details or other items may inadvertently be inaccurate.

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The Deutsche Nationalbibliothek lists this publication in the Deutsche Nationalbibliografie; detailed bibliographic data are available on the Internet at <http://dnb.d–nb.de>.

© 2019 Wiley–VCH Verlag GmbH & Co. KGaA, Boschstr. 12, 69469 Weinheim, Germany

All rights reserved (including those of translation into other languages). No part of this book may be reproduced in any form — by photoprinting, microfilm, or any other means — nor transmitted or translated into a machine language without written permission from the publishers. Registered names, trademarks, etc. used in this book, even when not specifically marked as such, are not to be considered unprotected by law.

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Preface

Chemical looping as reported in this book and in others is an old technology with a new name. The earliest technologies using a chemical looping concept date back to the early parts of the twentieth century. Fan and Tong in Chapter 1 state that there is evidence that some of the aspects of chemical looping were even present in a calcium carbide process as early as 1897 with the generally accepted earliest involving a process to produce hydrogen by looping iron oxide in 1910.

Although there are other books on chemical looping, they tend to promote a specific technology and/or a specific application. To the contrary, this book presents an overview of chemical looping technologies. As such, the book is divided into four topical areas. The first three of these look at various aspects of chemical looping combustion, while the last section provides chapters on other chemical looping technologies, namely those applied to carbon dioxide capture.

In the first section, Chemical Looping Process Concepts, there are five chapters, each dedicated to a different technology/concept to promote the commercialization of chemical looping combustion. In the first chapter, LS Fan and Andrew Tong discuss the moving bed fuel reactor concept developed at Ohio State University. In the second chapter, Justin Weber of the National Energy Technology Laboratory presents a summary of the two fluidized bed configurations –single and double loop systems. In Chapter 3, Vincenzo Spallina and his coauthors Fausto Gallucci and Martin van Sint Annaland discuss the cyclic fixed bed process being developed at Eindhoven University of Technology. The fourth chapter presents the CLOU (Chemical Looping with Oxygen Uncoupling) process by Kevin Whitty of the University of Utah, JoAnn Lighty of Boise State University, and Tobias Mattisson of Chalmers University of Technology, being developed at the University of Utah. In the final chapter of the first section, Kunlie Liu, Liangyong Chen, and Zhen Fan present a pressurized chemical looping combustion process being developed at the University of Kentucky.

The second section of the book examines oxygen carrier performance through four chapters. Hanjing Tian of West Virginia University and coauthors Ranjani Siriwardane, of the National Energy Technology Laboratory (NETL), Esmail Monazam of REM Engineering Services, and Roald Breault of NETL present a summary of the performance of iron‐based carriers for chemical looping combustion. Tobias Mattisson of Chalmers University of Technology and Kevin Whitty of the University of Utah present the second chapter in the section on oxygen carriers for chemical looping with oxygen uncoupling, a process that utilizes the thermal decomposition of the carrier to give up gaseous oxygen. In the third chapter of this section, Fanxing Li of North Carolina State University and Nathan Galinsky of NETL and the Oak Ridge Institute of Science and Engineering (ORISE) present a summary of mixed metal oxide carriers. In the last chapter of this section, Sam Bayham of NETL, Nathan Galinsky of NETL and ORISE, Esmail Monazam of REM Engineering Services, and Roald Breault of NETL present a summary of oxygen carrier structure and attrition. It should be pointed out that carrier attrition, if not overcome, will be the undoing of chemical looping technologies. This particular chapter identifies some properties that can be improved to overcome these shortcomings.

The third section of the book presents three chapters on commercial designs for chemical looping technologies. In the first chapter of this section, CFD simulations for a commercial unit are presented by Subhodeep Banerjee of NETL and ORISE, and Hongming Sun and Ramesh Agarwal, both of Washington University. The second chapter presents a cost comparison of a couple of technologies and is written by Robert Stevens of NETL, Dale Keairns of Deloitte Consulting, and Richard Newby and Mark Woods, both of KeyLogic Systems. In the last chapter of the section, Joanne Lighty of Boise State University and Zachary Reinking and Matthew Hamilton, both of University of Utah, present a summary on modeling and system simulations for a CLOU process.

The final section of the book presents two chapters on alternate chemical looping technologies. In these chapters, the focus is on CO2 capture. In the first of these chapters, Yiang‐Chen Chou, Wan‐Hsia Liu, and Heng‐Wen Hsu of Taiwan's Industrial Technology Research Institute present a summary of the calcium looping carbon capture process. Finally, in the last chapter, Hamid Arastoopour and Javid Abbasian of the Illinois Institute of Technology present a summary of the magnesium oxide process for CO2 capture that they are developing.

Section 1Chemical Looping Process Concepts

1The Moving Bed Fuel Reactor Process

Andrew Tong Mandar V. Kathe Dawei Wang and Liang‐Shih Fan

The Ohio State University, Department of Chemical Engineering, 151 W. Woodruff Ave, Columbus, OH, 43210, USA

1.1 Introduction

Chemical looping refers to the use of a chemical intermediate in a reaction‐regeneration cycle to decompose one target reaction into two or more sub‐reactions. The decomposition of the target reaction with a reactive chemical intermediate can decrease the process irreversibility, and, thus, increase the recoverable work from the system yielding a higher exergy efficiency. Further, when one or more of the reactant feedstocks consist of an inert substrate, the chemical looping reaction pathway is designed to prevent the direct contact of the inert with the desired product, minimizing the product purification steps required [1–3]. In 1987, Ishida et al. was the first publication to use the term, “chemical looping,” referring to the use of a metal oxide as the chemical intermediate to perform oxidation–reduction reaction cycles for power generation applications [4]. However, Bergmann's invention of a calcium carbide production process using manganese oxide redox reaction cycles with carbonaceous fuels suggests that the chemical looping concept was in development as early as 1897 [5]. Table 1.1 summarizes the early developments of chemical looping processes in the twentieth century [6–9, 12–21]. Though several achieved pilot scale demonstration, no early chemical looping processes were able to achieve widespread commercial realization due to limitations in the oxygen carrier reactivity, recyclability, and attrition resistance and the reactor design for maintaining, continuous high product yield.

Table 1.1 Summary of early chemical looping process development.

Process/developer

Lane [

6

–

11

]

Lewis and Gilliland

HYGAS

CO

2

acceptor

HyPr‐Ring

Year developed

1910s

1950s

1970s

1960s–1970s

1990s

Feedstock

Syngas

Solid fuel

Syngas

Solid fuel

Solid fuel

Products

H

2

CO

2

H

2

H

2

rich syngas

H

2

Chemical intermediate

Fe

3

O

4

–Fe

CuO

–Cu

2

O or Fe

2

O

3

–Fe

3

O

4

Fe

3

O

4

–Fe

CaCO

3

–CaO

CaCO

3

–CaO/ Ca(OH)

2

ARCO GTG

DuPont

Otsuka

Solar water splitting

Steinfeld

Year

1980s

1990s

1990s

1980s

1990s

Feedstock

CH

4

C

4

H

10

CH

4

H

2

O

CH

4

, iron ore

Products

C

2

H

4

C

4

H

2

O

3

Syngas

H

2

, O

2

Syngas, iron

Chemical intermediate

Supported Mn

VPO

Supported CeO

2

ZnO

–Zn or Fe

3

O

4

–FeO/Fe

Fe

3

O

4

–Fe

With growing concerns of greenhouse gas emissions, a renewed effort in developing chemical looping processes occurred at the start of the twenty‐first century as reflected in the exponential growth of research publications [1]. As of 2012, over 6000 cumulative hours of operation of chemical looping processes for power generation with CO2 capture have been demonstrated over fuel processing capacities ranging from 300 Wth to 3 MWth[22]. Nearly all chemical looping processes at the pilot scale demonstration have adopted a fluidized bed reactor design for the conversion of the fuel source to CO2/H2O, or the fuel reactor [23]. Recent developers are investigating fixed bed reactors to perform the cyclic oxidation–reduction reactions with chemical looping oxygen carriers for power generation and chemical production applications [24–27]. Alternatively, chemical looping processes utilizing a moving bed fuel reactor are under development for full and partial fuel conversion for CO2 capture/power generation and syngas production, respectively [23, 28, 29]. This chapter describes the use of moving reactors for chemical looping processes with specific application to syngas and power production with CO2 capture using metal oxide materials as oxygen carrier chemical intermediates. Two modes of moving bed operation are discussed and their application for full and partial fuel oxidation. Reactor thermodynamic modeling combined with experimental results are provided.

1.2 Modes of Moving Bed Fuel Reactor Operation

As illustrated in Figure 1.1, the moving bed fuel reactor can be operated in the counter‐current or co‐current mode based on the gas–solid flow contact pattern with Fe‐based oxygen carrier as the exemplary chemical intermediate [1]. The counter‐current moving bed fuel reactor in Figure 1.1a achieves a high oxygen carrier conversion while maintaining high CO2 product purity. The oxygen carrier conversion, as defined in Eq. (1.1), is the mass ratio of the amount of oxygen used from the oxygen carrier exiting the fuel reactor relative its maximum available oxygen.

1.1

Figure 1.1 Conceptual design of a moving bed chemical looping processes with a counter‐current (a) and co‐current (b) fuel reactor for full fuel conversion to CO2/H2O and for fuel gasification/reforming to syngas, respectively.

where mox and mred refer to the mass of the fully oxidized and the reduced sample at the outlet of the fuel reactor, respectively, and refers to the mass of the sample at the fully reduced state (e.g. metallic iron for Fe‐based oxygen carriers).

Figure 1.1b shows the co‐current moving bed fuel reactor for partial oxidation of the solid or gaseous fuel source to syngas. The co‐current process allows for accurate control of the oxygen carrier and fuel residence times, ratios, and distribution to maintain continuous high purity syngas. The present section discusses the advantages of each mode of the moving bed reactor operation and considers several applications for solid and gaseous fuel conversion for each.

1.2.1 Counter‐Current Moving Bed Fuel Reactor:

In a counter-current moving bed operation of chemical looping process, the gas species in the fuel reactor travel the opposite direction relative to the solids flow. Further, the gas species operate below the minimum superficial gas velocity and, thus, travel only through the interstitial spaces of the packed moving bed of oxygen carrier solids. For full fuel conversion, the counter‐current moving bed design is capable of maintaining high CO2 purities and reducing the oxygen carrier to a low oxidation state, ideal for metal oxides with multiple oxidation states such as iron [30, 31]. Figure 1.2 is an example of operation lines for moving bed chemical looping fuel reactor and steam reactor. The figure illustrates the phase equilibrium of a Fe‐based oxygen carrier particle at varying partial pressures (i.e. conversions) of the reducing gas at 850 °C. In the figure, the solid line represents the phase equilibrium of iron. The dashed line in the fuel reactor region represents the counter‐current reactor operation while the dotted line represents the fluidized bed/co‐current operation. The slope of the moving bed and fluidized bed operating lines are determined based on the oxygen balance between the oxygen carrier and the gas species. In the case of fluidized bed operation with iron‐based oxygen carrier, the maximum oxygen carrier conversion achievable is 11% (i.e. reduction from Fe2O3 to Fe3O4), as a higher oxygen carrier conversion will result in a decrease in product purity from the fuel reactor. Further, the high extent of reduction of the iron oxide oxygen carrier achieved in the counter‐current fuel reactor allows for thermodynamically favorable reaction of Fe/FeO with H2O to produce H2 via the steam–iron reaction. High purity H2 production from a third reactor, i.e. the steam reactor, increases the product flexibility of the processes and can serve as an advanced approach for H2 production with minimal process operations for product separation compared to traditional steam–methane reforming (SMR).

Figure 1.2 Operation lines for moving bed chemical looping fuel reactor and steam reactor.

Figure 1.3 illustrates the design of the counter‐current fuel reactor for solid fuel conversion to CO2. Here, the fuel reactor is divided into two sections [32–34]. Once the solid fuel is introduced to the high temperature fuel reactor, it devolatilizes and the solid char species travel downward co‐currently with the flow of oxygen carrier solids into the char gasification section. The volatiles travel upward counter‐currently with the flow of the oxygen carrier. In the lower bed, the solid char is gasified using an enhancer gas consisting of CO2 and/or H2O recycled from the flue gas produced from the fuel reactor. The gasified char and volatile matter are polished to CO2 and H2