Combined Chemical Looping: New Possibilities for Energy Storage

Subscriber access provided by UNIVERSITY OF ADELAIDE LIBRARIES

Communication

Combined Chemical Looping: New Possibilities for Energy Storage and Conversion Vladimir V. Galvita, Hilde Poelman, and Guy B Marin Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.7b02490 • Publication Date (Web): 26 Aug 2017 Downloaded from http://pubs.acs.org on August 28, 2017

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Energy & Fuels is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 17

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Combined chemical looping: new possibilities for energy storage and conversion

Vladimir V. Galvita*, Hilde Poelman, Guy B. Marin Laboratory for Chemical Technology, Ghent University, Technologiepark 914, B-9052 Ghent, Belgium *E-mail: [email protected]

TOC GRAPHICS

Air

H2O

Zone 2 Zone 1 heat Chamber 1 Ni Fe heat

Fe

Chamber 2

Fe2O3

N2

Fe3O4

H2

Abstract A novel concept of energy storage and conversion was demonstrated in a laboratory scale test. The proposed combined chemical looping is able to store and release energy from chemical looping combustion for heat generation and hydrogen production by steam-iron processes integrated in one reactor. The reactor contains two concentric chambers which are both filled

ACS Paragon Plus Environment

1

Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 17

with iron based material. In a first step, all material is reduced to the metallic form, thus ‘charging’ the reactor. For the second step or ‘discharging’, steam is fed to the inner chamber and air to the outer one. The inner chamber is used for hydrogen production, the external chamber for heat generation. In addition to iron, the external chamber contains a highly pyrophoric Ni based layer at the air entry point to enable the startup of heat generation at room temperature. This concept of combined chemical looping was successfully tested: heat was generated by metal oxidation in air and H2 was produced following contact of the reduced sample with H2O with average space time yield 0.2 molH2/kgFe/s.

A reliable supply of energy is a basic requirement for sustainable development and economic growth of our society 1. Currently, energy can be stored in different forms: as chemical energy of reactants and fuels, as mechanical energy, in an electric or magnetic field, or as nuclear fuel 2. In a typical energy storage process, one type of energy is converted into another form which can be used at will. Developing new materials and processes that provide high-performance energy storage combined with flexibility towards a wide range of technological applications is one of the most important topics in the 21st century 3-11. At present, the world's energy needs are met predominantly through the combustion of fossil fuels1. Chemical looping combustion (CLC) is emerging as a particularly promising technology which offers an elegant and efficient route towards clean combustion of fossil fuels 12-13. In CLC, the combustion is broken down into two separated half-steps: (i) the oxidation of an oxygen carrier with air and (ii) the subsequent reduction of this carrier via reaction with a fuel. The overall reaction is equivalent to a conventional combustion. While initial interest in chemical looping focused only on combustion 13, current research demonstrates that it can provide a highly


2

Page 3 of 17

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

flexible technology platform for fuel conversion 14-16. For metals which are oxidizable by H2O or CO2 (Fe, Sn, Ce, In, W), substituting air with these oxidizers yields the chemical looping equivalent to steam or dry reforming, resulting in either the production of high purity hydrogen streams without the need for further clean-up steps, or a novel route for efficient CO2 activation via reduction to CO

17-22

. Recently, a “super-dry” CH4 reforming

23

reaction was developed for

enhanced CO production from CH4 and CO2. Ni/MgAl2O4 was used as a CH4 reforming catalyst, Fe2O3/MgAl2O4 as a solid oxygen carrier, and CaO/Al2O3 as a CO2 sorbent. The isothermal coupling of these three different processes resulted in higher CO production compared with conventional dry reforming by avoiding the water gas shift

reactions. Apart from clean

combustion, chemical looping also holds promise as a novel approach for energy storage. The coupling of two such processes into combined chemical looping was demonstrated as novel concept of energy storage in a laboratory scale test 24. The proposed technology is able to store and release energy from redox chemical looping reactions combined with calcium looping. This process uses Fe3O4 and CaO, two low cost and environmentally friendly materials, while CH4 + CO2 serve as feed. During the reduction of Fe3O4 by CH4, the so-called “charging step”, both carbon and metallic iron are formed. CO2 acts as mediation gas to facilitate the metal/metal oxide redox reaction and carbon gasification into CO. CaO, on the other hand, is used for storage of CO2. During the so-called “discharging step” temperature rise, CaCO3 releases CO2, which reoxidizes the carbon deposits and reduced Fe, thus producing carbon monoxide. After each redox cycle, the material is fully regenerated, so that it can be used repeatedly, providing a stable process. The thus generated CO could be used in a solid oxide fuel cell (SOFC). We propose a simple, safe and environmentally benign technology for the storage, transport and supply of fuel or energy to any device. The objective of the present study is the experimental


3

Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 4 of 17

validation of a novel concept of energy storage and conversion based on an combination of two chemical looping processes in one unit. The first process, metal oxidation by oxygen (CLC) is applied for heat generation. This heat is utilized in the second process, chemical looping steam reforming (CLSR) for H2 production. The working principle of the “combined chemical looping” system is schematically shown in Figure 1.

Figure 1. H2 production unit combining two fixed-bed reactors into one reactor with two chambers. Air feed provides heat for steam conversion into hydrogen by interaction with iron (A); Schematic working principle of combined chemical looping for energy storage and conversion: half cross-sectional reactor view during (B) materials charge step, (C) materials discharge step.

The unit contains two concentric reaction chambers, based on two metal tubes with different diameter. The smaller tube is placed inside the larger one and both are filled with iron oxide based materials. The inner tube is used for hydrogen production via the steam-iron process


4

Page 5 of 17

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

CLSR, while the outer one provides heat generation by CLC. Metals react easily with oxygen in air to form stable, non-toxic solid oxides upon combustion and they have higher volumetric energy density than gasoline or other fossil fuels when burned with air

4, 7, 25-26

. Given adequate

insulation of the outside reactor wall, the efficiency of heat transfer towards the inner chamber will be strongly enhanced. The operation of the “chemical charge” and “discharge” cycles can be described as follows. During the “charge process” (material reduction step), fuel is fed into both chambers with iron oxides. Interaction of fuel with iron oxide leads to formation of metallic iron. The reduced iron oxide can be stored in this “charged” condition at room temperature. For the “discharge” (material oxidation step), the temperature of the sample is increased by feeding air or oxygen into the outer CLC chamber to oxidize the reduced metal (Eq. 1). The heat thus generated is transferred through the metallic wall which separates the CLC and CLSR chambers. At the same time H2O(l) is injected into the inner chamber. The interaction between H2O and the hot metallic iron leads to production of steam and further to hydrogen (Eq. 2). 2Fe + 3/2O2 → Fe2O3+ heat

Δ‫ܪ‬°ଶଽ଼௄ =-405kJ/molFe

(1)

4H2O + 3Fe → Fe3O4 + 4H2

Δ‫ܪ‬°ଶଽ଼௄ =-100kJ/molFe

(2)

The generated H2 could then be fed, for example, into a fuel cell where it is electrochemically oxidized, producing electricity and H2O, or into a hydrogen internal combustion engine 27. Once the iron material has been oxidized in the reactor to Fe3O4 and Fe2O3, it can be again reduced by any fuel: gaseous (solar hydrogen, CH4, syngas,..), a liquid (ethanol, methanol, gasoline, …) or solid fuel (coal, carbon, wood, …).


5

Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 6 of 17

Samples of 100wt%Fe2O3 and 80wt%Fe2O3-CeO2 were investigated. The following chemicals were used in the preparation of the mixed oxides: Fe(NO3)3·9H2O and Ce(NO3)3·6H2O (99.99%, Sigma-Aldrich). Samples were prepared by co-precipitation by adding an excess of ammonium hydroxide. This mixture was kept at room temperature for 24 h. Hereafter, the sample was separated as precipitate from the solution, washed with ethanol, and dried overnight in an oven at 110°C. Finally, the materials were calcined at 750°C for 6h. The 50wt%NiO-Al2O3 was prepared by co-precipitation. Precipitation was carried out from aqueous solutions of metal nitrates: Ni(NO3)2·6H2O and Al(NO3)3·9H2O. Ammonium bicarbonate was used as a precipitation agent. Coprecipitated samples were thoroughly washed with distilled water, dried at 110°C in air, and then calcined in air at 600°C for 4 h. Crystallographic analyses of the tested catalysts were performed by means of in situ Xray diffraction (XRD) measurements in θ–2θ mode using a Bruker-AXS D8 Discover apparatus with Cu Kα radiation of wavelength 0.154 nm and a linear detector covering a range of 20° in 2θ with an angular resolution of approximately 0.1° 2θ. While the minimal capturing time is 0.1s, a collection time of typically 10s was used during these experiments. The evolution of the catalyst structure during Temperature Programmed Oxidation (TPO) was investigated in a flowing gas stream of O2 from room temperature to 800°C. The in situ experiments were carried out using a home-built reactor chamber with Kapton foil window for X-ray transmission. A 10 mg sample was evenly spread in a shallow groove of a single crystal Si wafer. Interaction of the catalyst material with the Si holder was never observed. The chamber atmosphere was pumped and flushed with a rotation pump (base pressure ∼4 × 10–2mbar) before introducing the reducing gas flow.


6

Page 7 of 17

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

The sample was heated from room temperature to 800°C at a heating rate of 20°C/min. In situ XRD during O2-TPO immediately followed upon Temperature Programmed Reduction (H2-TPR). Activity measurements were carried out at atmospheric pressure in a quartz tube microreactor (i.d. 10 mm) and a metal reactor tube (i.d. 2 mm) placed inside the quartz tube,

positioned in an electric furnace (Figure S4). Typically, 1g of 100Fe or 80Fe-Ce

sample was packed between quartz wool plugs and used for heat generation. For a typical experiment of H2 production, 250mg of 80Fe-Ce was packed inside the metal reactor. The temperature of the material zone inside of metal tube was measured with K-type thermocouples inside of the reactor. In all experiments, the material was reduced by hydrogen at 700°C for 20 min. The total flow rate of the gas feed into the reactor was maintained constant by means of Brooks mass flow controllers into each chambers independently. The space time yield (STY, mol/s/kg) was calculated from the difference between the inlet and outlet molar flow rates, as measured relative to an internal standard (Ar) using an online quadrupole mass spectrometer, i.e. STY = (F0, − F)/m, where Fi, mol/s, is the molar flow rate of component i, and m is the amount of Fe in the sample. In order to simulate steady-state chemical looping operation based on a single reactor H2 space time yield, the space time yield for a multi-tubular reactor concept was calculated. Such multitubular reactor is perceived as a bundle of fixed bed reactors, operated in parallel. The core of the simulation concept is that all single reactors are operated in chemical looping regime, but one after the other, i.e. with a delay relative to the previous one. A redox cycle is established in each single reactor by switching the feed valves at discrete times, leading to an oscillating H2 space


7

Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 8 of 17

time yield and eventually generating a permanent periodic regime for the multi-tubular reactor concept. Two samples of Fe2O3 (100Fe) and 80Fe2O3-CeO2 (80Fe-Ce) were investigated in this study. 80Fe-Ce preciously showed improved performance and high stability in chemical looping processes for H2 and CO production 28-29. The 100Fe sample was used as a reference material. In situ XRD measurements were performed during O2-TPO in order to understand the transformation of the sample during the reduction process. According to literature, the oxidation reaction of Fe and Fe-CeO2 can run through several stages: Fe → FeO → Fe3O4→ Fe2O3 15. O2TPO was performed immediately after cool down in Ar following H2 reduction at 700°C during 15min (Reduction of 80Fe-Ce sample presented in Figure S1). The in situ time resolved XRD patterns for both samples are presented in Figure 2a and b, showing the characteristic Fe diffraction ~45°, which gives way to diffraction peaks of Fe2O3. The temperature at which the Fe phase transition occurs increases from 225°C for 80Fe-Ce up to 425°C for Fe. No intermediate FeO phase is apparent for both samples and Fe3O4 was observed only for the monometallic sample. The test results for the heat generation with these samples are shown in Figure 3. At room temperature, no ignition was observed for both materials. 100Fe produced heat only at an initial sample temperature of 400°C. 80Fe-Ce produced a significant amount of heat from an initial temperature ~175°C. When the same sample was reduced and re-oxidized, the amount of produced heat decreased. Figure 3 shows that after the third cycle 100Fe only generated a maximal temperature of 425°C. On the other hand, 80Fe-Ce still yielded a maximum temperature of 450°C after the third, fourth and fifth cycle.


8

Page 9 of 17

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Figure 2. 2D XRD pattern recorded during O2-TPO for 100Fe (A) and 80Fe-Ce (B); TPO measuring conditions: 20°C/min, 20%O2 in He.


9

Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 10 of 17

Figure 3. Comparison of heat generation vs. time on stream during air feeding to prereduced 100Fe (A) and 80Fe-Ce (B) for different redox cycles. The insets present the photographs of the used samples.

■

- 1st,

● - 2nd ,

▲-.3rd, ▼.- 4th and

♦.-5th redox

cycles. Reduction: 100%H2 at 700°C, time = 20min, air = 100Nml/min, W=1g.

When the sample was removed from the reactor, strong sintering of the 100Fe sample into agglomerates was observed (see inset in Figure 3A). It is well known that pure iron oxide is prone to fast sintering during reduction-oxidation cycles 28. In contrast, 80Fe-Ce did not exhibit strong agglomeration and came out of the reactor as a powder (inset in Figure 3B). STEM did not show drastic changes in this sample morphology (Figure S2, Supporting Information). However, the average crystalline size did increase from 50 nm to 200 nm. As confirmed by other researchers, the size of reacting particles has a profound effect on heat generation

30

. For a fixed total amount of material, sintering leads to decrease of

surface area. A lower surface area requires more initial heat to bring the reacting system up to its activation state, leading to a lower amount of net heat being released by the exothermic reaction. The experimental results demonstrate that iron particles in 80Fe-Ce react exothermically with oxygen in air and produce iron oxide with ignition at ~175°C and maximum temperature ~730°C. Hence, sintering needs to be limited to preserve the heat generation capacity. Then again, the same relation between particle size and temperature can be used to bring down the ignition temperature to room temperature. The research involving ignition of powders with different size distributions and, in particular, nanopowders, has shown that the ignition temperature is a strong


10

Page 11 of 17

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

function of particle size

26, 30

. Reduced supported metals like Ni, Co, Fe, become extremely

pyrophoric when the metal crystallites are nanosized. If these catalysts are exposed to air, the metal particles instantaneously oxidize, generating large amounts of heat such that the particles glow red. This heat may be directly used for ignition of 80Fe-Ce. In the present study, a reduced Ni-Al2O3 (Ni-Al) sample was applied as highly pyrophoric material, burning spontaneously in air without application of heat (Eq. 3). Experiments with a 50Ni-Al sample showed that temperature rose from 30°C up to 250°C in 15 seconds. This temperature is sufficient to initiate the iron oxidation. 2Ni +O2 =2NiO

Δ‫ܪ‬°ଶଽ଼௄ = -469kJ/mol

(3)

This pyrophoric property can be utilized in the new reactor concept as illustrated in Figure 4a. The chamber for heat generation now contains two consecutive fixed zones. Within the first, holding the 50Ni-Al catalyst, air oxidizes Ni so that the temperature of this zone increases. Preheated air then reaches the second 80Fe-Ce catalyst zone, starting the metal iron oxidation which will generate even more heat. An experimental test of low temperature iron oxide initiation using this segmented chamber was performed with 50Ni-Al and 80Fe-Ce. After reduction by hydrogen at 700°C for 30 min, the flow was switched to Ar and the temperature of the reactor decreased. Figure 4b present the temperature of the Fe-Ce zone as a function of time on air stream. Shortly after air is fed into the reactor, the temperature of the zone increases and exhibits a maximum as high as 650°C after 2 min and then slowly decreases toward 450°C after another 2 min (see also video in the Supporting Information). The test results indicate that the use of pyrophoric 50Ni-Al and 80Fe-Ce in a two zones configuration provides a higher heating value than that of a single Fe-Ce zone (Figure 3B) and is therefore more suitable for use as a heat source.


11

Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 12 of 17

Figure 4. H2 production unit using concentric chambers with air feed at room temperature into the outer chamber, segmented into two zones for metal oxidation, and providing heat to the inner chamber for steam conversion into hydrogen (A); Heat generation vs. time on stream during the air feed into the two-zone reactor with Ni-Al as a first zone and 80Fe-Ce as a second zone (B); space time yield of H2 during the feed of air into heat generation chamber and H2O/Ar for hydrogen production over pre-reduced materials (C); Wife-Ce = 1g, WNi-Al = 0.25g, T = 40°C, H2O = 30Nml/min + Ar = 30Nml/min, air = 100Nml/min. The error bar indicates twice the standard deviation.


12

Page 13 of 17

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Finally, the concept of combined chemical looping with two concentric chambers was tested for actual hydrogen generation. The inner chamber for hydrogen production contained only 80FeCe. The outer chamber had two consecutive zones with 50Ni-Al at the inlet and 80Fe-Ce beyond. Hydrogen was fed into these reactors at 700°C for 30 min for materials reduction. When the temperature of the reactor had dropped to 30°C, air was fed into the outer chamber of the reactor. As soon as the temperature of the reactor reached 300oC, the H2O feed to the inner chamber was started. H2 was produced following contact of the reduced 80Fe-Ce sample and H2O. Figure 4c presents the evolution of H2 production: the space time yield for H2 increases, passes through a maximum at 490°C and then steadily decreases towards zero at 600°C because complete oxidation of Fe into Fe3O4 by steam. Continuous production of H2 using such a process can be achieved if multiple reactors will operate in parallel23. The H2 space time yield for a multi-tubular reactor concept was calculated by a dynamic simulation of redox cycles based on steady-state chemical looping operation of a single reactor. The space time yield was determined based on the concept that all single reactors are operated in chemical looping regime, but one after the other, i.e. with a delay relative to the previous one23,

31

. The time delay and the number of reactors in operation are based on the

experimental results obtained for a single reactor. The average space time yield for such a multireactor configuration reaches ~0.2 molH2/kgFe/s. To assess the process viability, the stability of the materials and their activity was examined during repeated charge and discharge cycles. The space time yield of hydrogen remained close to constant after the 5th cycle, which confirmed the stability of the 80Fe-Ce materials' activity. In addition, this 80Fe-Ce sample was tested at 600°C during 100 redox cycles, presenting high


13

Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 14 of 17

stability after the first 25 cycles (Figure S3, S5, Supporting Information). However, after the first oxidation procedure the temperature of the Ni-Al zone had to be increased from 30°C to 160°C to guarantee enough heat production for the 80Fe-Ce oxidation. Sintering lead to an increase of crystallite size of Ni and, hence, smaller surface area which required a higher ignition temperature. The latter illustrates that the future of this process depends greatly on material advancement. Innovation can be achieved through adopting different synthesis strategies, such as core-shell preparation and stabilization of the active metal for heat generation in the pores of high surface area materials.

Summary and Outlook. The proposed combined chemical looping is able to store and release energy from chemical looping combustion for heat generation and hydrogen production by steam-iron processes integrated in one reactor. The reactor contains two chambers which are both filled with iron based material. The reactor can be ‘charged’ at high temperature (700oC) by the material reduction to the metallic form. In addition to iron, the chamber for heat generation contains a highly pyrophoric Ni based layer at the air entry point to enable the startup of heat generation at room temperature during ‘discharging’. A novel concept in a laboratory scale test demonstrate H2 production with average space time yield 0.2 molH2/kgFe/s. This technology should certainly be applicable well beyond the steam-iron process. Extension can be made to, for example, catalytic hydrogen production by dimethyl ether (DME) or methanol steam reforming which operate at moderate temperature, generation of CO from CO2 for solid oxide fuel cell (SOFC)

24

, or generation of thermoelectric power

30

. As an extended

proof of concept, methane was used as a fuel instead of hydrogen in the proposed process. It is well know that interaction of methane with Ni leads to H2 and carbon formation and hence


14

Page 15 of 17

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

catalyst degradation. During the oxidation with H2O, the produced H2 contains carbon monoxide due to gasification of surface carbon. In order to overcome this problem, a mixture of CH4 and CO2 was applied for material reduction (Figure S6). As shown in this paper, the primary candidate for use in this process, that can be oxidized in the chemical looping process and subsequently used for hydrogen production by interaction with H2O, is iron. Millions of tons of iron are currently produced world-wide for the powder metallurgy, chemical and electronic industries. Iron–air batteries are being developed for economic reasons due to the abundance and low cost of iron resources

32-33

. An important

property of iron is that it is readily recyclable with well-established technologies. Iron can be obtained from iron oxide powders by reaction with hydrogen or syngas at moderate temperatures below 800°C. All of these make iron an ideal energy carrier, which is why more and more scientists are rediscovering iron.

Acknowledgments: This work was supported by the Long Term Structural Methusalem Funding of the Flemish Government, and the Interuniversity Attraction Poles Programme, IAP7/5, of the Belgian State–Belgian Science Policy. The authors acknowledge support from Prof. C. Detavernier with the in situ XRD equipment (Department of Solid State Sciences, Ghent University) and from Dr. Vitaliy Bliznuk (Department of Materials Science and Engineering, Ghent University) for the HRTEM measurements. Additionally, we would like to thank Daria Galvita for producing the video during her school project at the Laboratory for Chemical Technology.


15

Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 16 of 17

References 1. Hoffert, M. I.; Caldeira, K.; Benford, G.; Criswell, D. R.; Green, C.; Herzog, H.; Jain, A. K.; Kheshgi, H. S.; Lackner, K. S.; Lewis, J. S.; Lightfoot, H. D.; Manheimer, W.; Mankins, J. C.; Mauel, M. E.; Perkins, L. J.; Schlesinger, M. E.; Volk, T.; Wigley, T. M. L., Advanced Technology Paths to Global Climate Stability: Energy for a Greenhouse Planet. Science 2002, 298 (5595), 981-987. 2. Kousksou, T.; Bruel, P.; Jamil, A.; El Rhafiki, T.; Zeraouli, Y., Energy storage: Applications and challenges. Solar Energy Materials and Solar Cells 2014, 120, 59-80. 3. Qin, L.; Cheng, Z.; Guo, M.; Xu, M.; Fan, J. A.; Fan, L.-S., Impact of 1% Lanthanum Dopant on Carbonaceous Fuel Redox Reactions with an Iron-Based Oxygen Carrier in Chemical Looping Processes. ACS Energy Letters 2017, 2 (1), 70-74. 4. Bergthorson, J. M.; Goroshin, S.; Soo, M. J.; Julien, P.; Palecka, J.; Frost, D. L.; Jarvis, D. J., Direct combustion of recyclable metal fuels for zero-carbon heat and power. Applied Energy 2015, 160, 368382. 5. Sun, Y.-K., Future of Electrochemical Energy Storage. ACS Energy Letters 2017, 2 (3), 716-716. 6. Li, Y.; Lu, J., Metal–Air Batteries: Will They Be the Future Electrochemical Energy Storage Device of Choice? ACS Energy Letters 2017, 2 (6), 1370-1377. 7. Beach, D. B.; Rondinone, A. J.; Sumpter, B. G.; Labinov, S. D.; Richards, R. K., Solid-State Combustion of Metallic Nanoparticles: New Possibilities for an Alternative Energy Carrier. Journal of Energy Resources Technology 2006, 129 (1), 29-32. 8. Muhich, C. L.; Evanko, B. W.; Weston, K. C.; Lichty, P.; Liang, X.; Martinek, J.; Musgrave, C. B.; Weimer, A. W., Efficient Generation of H2 by Splitting Water with an Isothermal Redox Cycle. Science 2013, 341 (6145), 540-542. 9. Brownson, D. A. C.; Kampouris, D. K.; Banks, C. E., An overview of graphene in energy production and storage applications. Journal of Power Sources 2011, 196 (11), 4873-4885. 10. Leung, P.; Shah, A. A.; Sanz, L.; Flox, C.; Morante, J. R.; Xu, Q.; Mohamed, M. R.; Ponce de León, C.; Walsh, F. C., Recent developments in organic redox flow batteries: A critical review. Journal of Power Sources 2017, 360, 243-283. 11. Wang, X.; Dong, C.; Lou, M.; Dong, W.; Yuan, X.; Tang, Y.; Huang, F., Tunable synthesis of Fe-Ge alloy confined in oxide matrix and its application for energy storage. Journal of Power Sources 2017, 360, 124-128. 12. Nandy, A.; Loha, C.; Gu, S.; Sarkar, P.; Karmakar, M. K.; Chatterjee, P. K., Present status and overview of Chemical Looping Combustion technology. Renewable and Sustainable Energy Reviews 2016, 59, 597-619. 13. Moghtaderi, B., Review of the Recent Chemical Looping Process Developments for Novel Energy and Fuel Applications. Energy & Fuels 2012, 26 (1), 15-40. 14. Bhavsar, S.; Najera, M.; Solunke, R.; Veser, G., Chemical looping: To combustion and beyond. Catalysis Today 2014, 228, 96-105. 15. Fan, L. S., Chemical Looping Systems for Fossil Energy Conversions. Wiley 2011. 16. Fan, L.-S.; Zeng, L.; Luo, S., Chemical-looping technology platform. AIChE Journal 2015, 61 (1), 222. 17. Galvita, V. V.; Poelman, H.; Detavernier, C.; Marin, G. B., Catalyst-assisted chemical looping for CO2 conversion to CO. Applied Catalysis B: Environmental 2015, 164, 184-191.


16

Page 17 of 17

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

18. Hu, J.; Galvita, V. V.; Poelman, H.; Detavernier, C.; Marin, G. B., A core-shell structured Fe2O3/ZrO2@ZrO2 nanomaterial with enhanced redox activity and stability for CO2 conversion. Journal of CO2 Utilization 2017, 17, 20-31. 19. Galvita, V. V.; Poelman, H.; Bliznuk, V.; Detavernier, C.; Marin, G. B., CeO2-Modified Fe2O3 for CO2 Utilization via Chemical Looping. Industrial & Engineering Chemistry Research 2013, 52 (25), 84168426. 20. Tang, M.; Xu, L.; Fan, M., Progress in oxygen carrier development of methane-based chemicallooping reforming: A review. Applied Energy 2015, 151, 143-156. 21. Najera, M.; Solunke, R.; Gardner, T.; Veser, G., Carbon capture and utilization via chemical looping dry reforming. Chemical Engineering Research and Design 2011, 89 (9), 1533-1543. 22. Bhavsar, S.; Najera, M.; Veser, G., Chemical Looping Dry Reforming as Novel, Intensified Process for CO2 Activation. Chemical Engineering & Technology 2012, 35 (7), 1281-1290. 23. Buelens, L. C.; Galvita, V. V.; Poelman, H.; Detavernier, C.; Marin, G. B., Super-dry reforming of methane intensifies CO2 utilization via Le Chatelier’s principle. Science 2016, 354 (6311), 449-452. 24. Galvita, V. V.; Poelman, H.; Marin, G. B., Combined chemical looping for energy storage and conversion. Journal of Power Sources 2015, 286, 362-370. 25. Mandilas, C.; Karagiannakis, G.; Konstandopoulos, A. G.; Beatrice, C.; Lazzaro, M.; Di Blasio, G.; Molina, S.; Pastor, J. V.; Gil, A., Study of Oxidation and Combustion Characteristics of Iron Nanoparticles under Idealized and Enginelike Conditions. Energy & Fuels 2016, 30 (5), 4318-4330. 26. Yetter, R. A.; Risha, G. A.; Son, S. F., Metal particle combustion and nanotechnology. Proceedings of the Combustion Institute 2009, 32 (2), 1819-1838. 27. Verhelst, S.; Wallner, T., Hydrogen-fueled internal combustion engines. Progress in Energy and Combustion Science 2009, 35 (6), 490-527. 28. Galvita, V.; Hempel, T.; Lorenz, H.; Rihko-Struckmann, L. K.; Sundmacher, K., Deactivation of Modified Iron Oxide Materials in the Cyclic Water Gas Shift Process for CO-Free Hydrogen Production. Industrial & Engineering Chemistry Research 2008, 47 (2), 303-310. 29. Dharanipragada, N. V. R. A.; Meledina, M.; Galvita, V. V.; Poelman, H.; Turner, S.; Van Tendeloo, G.; Detavernier, C.; Marin, G. B., Deactivation Study of Fe2O3–CeO2 during Redox Cycles for CO Production from CO2. Industrial & Engineering Chemistry Research 2016, 55 (20), 5911-5922. 30. Huang, D. H.; Tran, T. N.; Yang, B., Investigation on the reaction of iron powder mixture as a portable heat source for thermoelectric power generators. Journal of Thermal Analysis and Calorimetry 2014, 116 (2), 1047-1053. 31. Hu, J.; Buelens, L.; Theofanidis, S.-A.; Galvita, V. V.; Poelman, H.; Marin, G. B., CO2 conversion to CO by auto-thermal catalyst-assisted chemical looping. Journal of CO2 Utilization 2016, 16, 8-16. 32. Jin, X.; Zhao, X.; Zhang, C.; White, R. E.; Huang, K., Computational Analysis of Performance Limiting Factors for the New Solid Oxide Iron-air Redox Battery Operated at 550 °C. Electrochimica Acta 2015, 178, 190-198. 33. Narayanan, S. R.; Prakash, G. K. S.; Manohar, A.; Yang, B.; Malkhandi, S.; Kindler, A., Materials challenges and technical approaches for realizing inexpensive and robust iron–air batteries for largescale energy storage. Solid State Ionics 2012, 216, 105-109.


17

Combined Chemical Looping: New Possibilities for Energy Storage

Recommend Documents