Article pubs.acs.org/EF
Cite This: Energy Fuels 2018, 32, 2598−2604
Side Reactions of Coal Tar Pyrolysis Products with Different Reduction States of Iron-Based Oxygen Carriers Cuiping Wang,*,†,‡ Mingxin Gong,‡ Yongpeng Li,‡ Jian Gong,‡ Xiude Hu,† and Boyang Bai† †
State Key Laboratory of High-Efficiency Utilization of Coal and Green Chemical Engineering, Ningxia University, Yinchuan, Ningxia 750021, People’s Republic of China ‡ College of Mechanical and Electrical Engineering, Qingdao University, Qingdao, Shandong 266071, People’s Republic of China ABSTRACT: To evaluate the effects of severe side reactions on the product yield of pyrolysis of coal tar with iron oxide oxygen carriers (OCs), simulation experiments were carried out and analyzed by thermogravimetry−mass spectrometry. The reactions occurred between iron-based OCs with different reduction states and carbon black (CB) and syngas products. The H2 present in syngas showed the lowest initial reaction temperature and the highest decrease in concentration, indicating its strong reactivity. Because CO reacted with iron-based OCs at a higher temperature and had a slow reaction rate, the relative reactivity at the lowtemperature stage is lower compared to H2. At the high-temperature stage, the reaction of CO was inhibited by CH4 and the concentration of CO was affected by the reactions of CB. CH4 had the highest initial reaction temperature and least consumption but a higher reaction rate than CO in its narrow temperature range. Therefore, CH4 clearly affected the side reactions at high temperatures. Scanning electron microscopy with energy-dispersive X-ray spectroscopy analysis of the solid residues shows that the consumption of CB is low and the Fe/O ratio in the solid residues is larger, owing to the higher relative reactivity of syngas with different reduction states of iron-based OCs.
1. INTRODUCTION Chemical looping combustion (CLC) is a new efficient technology for carbonic fuel utilization. The oxygen carrier (OC) is used to transfer lattice oxygen and heat the fuel in the fuel reactor; oxygen is obtained in the air reactor. Because no nitrogen enters the fuel reactor and the flue gas flow rate is reduced, the gas emission is mainly composed of CO2 and vapor. Therefore, it is easy to collect CO2 generated and minimize the carbon and other pollutant emissions.1−3 Apart from using CLC solely for CO2 emission reduction, studies on chemical looping gasification (CLG) and chemical looping pyrolysis (CLP) have also been reported. For liquid fuel, heavy oil or coal tar could also be realized to produce industrial carbon black (CB) by the CLP method. Most industrial CB is produced by the oil furnace method with high energy consumption and pollutant emissions.4 According to CLG and CLP studies,5−7 the CB production by CLP of coal tar was performed in a fluidized bed reactor using inexpensive but highly reactive iron-based OCs.8,9 During the fluidization of OC particles, lattice oxygen and heat were transported to coal tar. The coal tar was pyrolyzed, releasing syngas with nanoparticles of CB. As a result of a lower reaction temperature compared to the oil furnace process, the CLP method saves energy and reduces emissions.10 If the pyrolysis reaction of coal tar with OC is considered as the major reaction producing CB and syngas, then other side reactions occur in the reactor top or in the transformation pipeline as a result of a still high temperature. The main studies on side reactions showed a clear relationship to the product yield. For example, the product yield could be increased by controlling the side reactions, and then the efficiency of the vanadium cell increased.11 Although Roh and co-workers studied the reformation of CO2 with vapor to make CH4, the © 2018 American Chemical Society
side reactions affect the CH4 yield, reducing the carbon deposition on the catalyst surface.12 Wang and co-workers also investigated the kinetic parameters of side reactions and the factors influencing the combustion rate during xylol liquid oxidation.13 Similarly, it is necessary to study multiple side reactions during the CLP of coal tar to analyze the effect of side reactions on the product yield. The coal tar consists of C14H10. It easily cracks at a high temperature and releases volatiles, other hydrocarbons, and char. Active gases, such as H2, CO, and CH4, in volatiles first react with OCs. The major reaction and elementary side reactions are shown in eqs 1−13.14−16 major reaction C14 H10 + 6Fe2O3 = 12C + 9FeO + CO + CO2 + 2H 2O + 3H 2 + Fe3O4
(1)
The possible side reactions are as follows: H 2 + Fe2O3 = Fe3O4 + H 2O
−2.01 kJ/mol
(2)
H 2 + Fe3O4 = 3FeO + H 2O
+47.65 kJ/mol
(3)
H 2 + FeO = Fe + H 2O
+25.14 kJ/mol
(4)
CH4 + 12Fe2O3 = 8Fe3O4 + CO2 + 2H 2O +175.98 kJ/mol
(5)
Received: November 8, 2017 Revised: January 8, 2018 Published: January 24, 2018 2598
DOI: 10.1021/acs.energyfuels.7b03450 Energy Fuels 2018, 32, 2598−2604
Article
Energy & Fuels
quality of samples was basically the same, including the mix sample in Table 1, as shown in Table 3.
CH4 + 4Fe3O4 = 12FeO + 2H 2O + CO +428.63 kJ/mol
(6)
CH4 + 4FeO = 4Fe + H 2O + CO2
Table 3. Sample Mass Used in Mixtures
+267 kJ/mol (7)
CO + 3Fe2O3 = 2Fe3O4 + CO2
− 50.57 kJ/mol (8)
CO + Fe3O4 = 3FeO + CO2
CO + FeO = Fe + CO2
+33.10 kJ/mol
−15.29 kJ/mol
C + 3Fe2O3 = 2Fe3O4 + CO C + Fe3O4 = 3FeO + CO
C + FeO = Fe + CO
(9)
+205.64 kJ/mol
+157.04 kJ/mol
①
②
③
mixture
170.2
170.4
170.3
171.1
171.6
170.6
170.5
170.8
2.2. Experimental Procedure. The experimental studies on side reaction competitiveness during the coal tar pyrolysis with iron-based OC were carried out using TG (STA449F3) equipped with a MS (QMS 403D) analyzer. The experiments were carried out at atmospheric pressure, and the temperature ranged from 30 to 850 °C at a heating rate of 10 °C/min. During the gas−solid reactions, a gas mixture (25% CO, 25% CO2, 25% CH4, and 25% H2) was fed to the reactor with a total flow rate of 20 mL/min, together with the carrier gas (100% N2) of 80 mL/min and the protecting gas (100% Ar) of 20 mL/min. When solid−solid reactions were performed, the flow rates of carrier gas (100% N2) and protecting gas (100% Ar) were 60 and 20 mL/min, respectively.
(10)
+ 121.72 kJ/mol
sample solid samples for solid−solid reactions (mg) solid samples for gas−solid reactions (mg)
(11) (12) (13)
where eqs 2−10 are the gas−solid reactions and eqs 11−13 are the solid−solid reactions. To investigate the possible side reactions during the major reaction and product transfer, the products were mixed at measured ratios in fluidized bed experiments to study the characteristics of the above-mentioned side reactions using thermogravimetry−mass spectrometry (TG−MS). Moreover, scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM−EDS) analysis was used to characterize the components and microcosmic appearance of solid residues in TG, thus elucidating the competitiveness and influence of side reactions.
3. RESULTS AND DISCUSSION 3.1. Solid−Solid Reaction Probability Analysis. Figure 1 shows the TGA, derivative thermogravimetry (DTG), and differential scanning calorimetry (DSC) results of three states of iron-based OC with CB in TG of sample mixtures.
2. EXPERIMENTAL SECTION 2.1. Sample Preparation. On the basis of the results of former experiments performed in the fluidized bed reactor,10 the mixture of solid products consists of CB and deoxidizing iron-based OCs. Therefore, the mix sample used in TG was mixed in a fixed ratio, as shown in Table 1.
Table 1. Mass Ratio of the Mixture Sample mix
Fe2O3
Fe3O4
FeO
CB
ratio (%)
17.8
33.8
28.4
20
Figure 1. TG−DSC curve of mixture sample under nitrogen. Different states of iron-based OCs all have the possibility of continuous reaction with CB. Therefore, solid−solid reaction experiments of each iron-based OC with CB were carried out to compare their contributions on CB consumption. Another three groups of thermogravimetric analysis (TGA) experiments, ①, ②, and ③, were performed using different states of iron-based OCs mixed with CB and the same weight of total reactant, according to the ratios shown in Table 2, with the same proportion of each OC to CB shown in Table 1. Fine particles (200 μm) of Fe2O3 (99% analytically pure), Fe3O4 (99%), FeO (99%), and CB (99%) samples were obtained from the Tianjin Lihuajin Chemical Industry. Each solid mixture was thoroughly blended using a mixer until a uniform sample was obtained. The
As shown in Figure 1, with the increase in the temperature, the total mass of the sample decreased with different speeds at different reaction stages. In combination with the DTG curve, the reactions can be divided into three stages according to the initial reaction temperatures and the reaction rate peaks, to compare various decrease features in speeds, and the results are shown in Table 4. Both the temperature range and time range points in the TGA curve are marked with dotted lines in Figure 1. During the first stage, a mass loss of about 5% was observed as a result of the evaporation of moisture. The second stage mainly involves the reaction of CB with OCs, producing CO and CO2 and causing another mass loss. The initial reaction
Table 2. Mass Ratio of CB to the Sole Iron-Based OC in Samples
Table 4. Features of the Mixture Sample in the TG Process sample
Fe2O3 (%)
① ② ③
47
Fe3O4 (%)
FeO (%)
CB (%)
58.6
53 37.2 41.3
62.8
time range (min) temperature range (°C) 2599
stage 1
stage 2
stage 3
0−28.6 0−523
28.6−48 523−900
48−85 900
DOI: 10.1021/acs.energyfuels.7b03450 Energy Fuels 2018, 32, 2598−2604
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Energy & Fuels Table 5. Reaction Characteristic Parametera
temperature was 520 °C, and the highest reaction rate of a mass loss of 0.290 mg/min occurred at a temperature of 731.8 °C and time of 40 min, as shown in the combined TG and DTG curve. The DSC curve showed two endothermic peaks. The first peak shows the evaporation endotherm starting at around 10 min and rapidly ending. The second endothermic peak corresponds to the beginning of the reaction, and the heat absorption is approximately equal to the activation energy (negative for the endotherm). After the mass change, the reaction becomes exothermic, and a significant exothermic peak corresponding to the highest mass reduction rate appeared at 40 min. Then, with the decrease in the reaction rate, the exotherm became less than the endotherm. In the third stage, the reaction rate became slow and the heat flow became stable. Two adjacent descending peaks (a significant peak at 40 min and a small peak at 48 min) appeared in the second stage of the DTG curve, as shown in Figures 2. The weight of the sample
a
sample
mixture
①
②
③
Ti (°C) DTGmax (mg/min) Tm (°C) mass loss (%)
520 −0.290 674 21.1
520 −0.105 669 23.2.
653 −0.105 736 12.0
667 −0.443 828 26.5
Ti, initial temperature; Tm, DTGmax corresponding temperature.
As shown in Table 5, the solid−solid reactions of the mixture of the OC with CB mainly depend upon residual Fe2O3 for the same low initial reaction temperature and approximately the same temperature when the reaction rate is the highest. Fe2O3 reacts in a wide range of the temperature, and the residual reaction occurred even when the temperature reached 900 °C. Consequently, excessive Fe2O3 OC is not beneficial for CB production when the pyrolysis products are generated at a high temperature before the collection of CB. In addition, the side reactions caused by FeO/Fe3O4 showed weak effects on CB consumption, because they occurred at too high temperatures and in a narrow temperature range, even though FeO had the highest reaction rate. 3.2. Gas−Solid Reaction Probability Analysis. 3.2.1. Reaction of Fe2O3 with CB and the Gas Mixture. The variation in mass loss and reaction rate for the reaction of Fe2O3with CB under the atmosphere of 5 wt % gas mixture is shown in Figure 4. With the progress in time, the temperature increases at a heating rate of 10 °C/min before reaching a constant value. Significant fluctuations were observed on the DTG curve as the TGA curve decreases. The dramatic change in the reaction rate reflects the complexity of the reaction, indicating that several reactions of Fe2O3−CB with the gas mixture occur at one time range. The integrated reaction characteristics in different temperature ranges are shown in Table 6. In the first stage, at a time of 23 min and about 230 °C, the extreme rate in the DTG curve corresponds to the maximum water vapor concentration, representing the precipitation of water crystals in the solid mixture. The concentrations of CH4 and H2 gradually became stable after the water loss and adsorption of CH4 and H2 on OC until 38 min. In the second range starting from 38 min, the concentration of H2 started to decrease as a result of the reaction of H2 with Fe2O3 at 433 °C, which increased the concentration of water vapor. H2 that adsorbed in the microspores of FeO rapidly reacted with the OC in 38−50 min, including the volume reaction and surface reaction and causing the rapid reduction of the H2 concentration and increase in the water vapor concentration. Although the temperature still increased, the reaction rate is limited by diffusion velocity and the reaction became stable. The CO2 concentration started to increase at 44 min when CO started to react. In the third stage, CO2 remains at a high concentration. The decrease in the H2 concentration and increase in the water vapor concentration are in correspondence, and both reached a peak value at 55 min. In this step, CO and CB are involved in the reaction together with H2, which dominates in terms of the growth rate of products. In the fourth stage, the total mass of the sample rapidly decreased and the MS curves show that the concentrations of CO and H2O rapidly increased. When the CO concentration reached the maximum value, the solid phase had the fastest weight loss, while the concentrations of CH4 and CO2 fluctuated only within a certain range. Therefore, the increase
Figure 2. TG curves of three samples.
clearly decreased, and the reaction of CB with the OC mixture occurred above 700 °C. The higher weight loss was mainly attributed to the reaction of Fe2O3, Fe3O4, or FeO with CB. Therefore, it is necessary to combine the TG curves of the reaction of a single iron-based OC with CB to investigate the contribution of each curve to the peaks of the mixture. The experimental conditions of the reaction of each ironbased OC with CB are similar. The TG−DTG curves of samples ①, ②, and ③ are shown in Figures 2 and 3, respectively. Some differences were observed among the three reaction procedures. The important characteristic parameters of the three reactions compared to the reaction of the mixture are shown in Table 5.
Figure 3. DTG curves of three samples. 2600
DOI: 10.1021/acs.energyfuels.7b03450 Energy Fuels 2018, 32, 2598−2604
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Figure 4. TG−MS curves of CB−Fe2O3 under gas mixture atmosphere.
with CB and the gas mixture. The reaction process can be divided into four stages according to the DTG characteristics. The data of each stage are shown in Table 7.
Table 6. Reaction Features of CB−Fe2O3 under a Gas Mixture Atmosphere time (min)
range (°C)
mass loss (%)
DTGmax (%/min)
0−38 38−50 50−65 65−73 73−100 100−120
0−433 433−600 600−696 696−751 751−850 850
3.64 2.24 5.50 4.22 7.8 0.24
−0.21 −0.33 −0.43 −0.88 −0.61
Table 7. Reaction Features of CB−Fe3O4 under a Gas Mixture Atmosphere
in the CO concentration results from the rapid reaction of CB with Fe2O3, and it is the main stage of consumption of CB. The concentration of CH4 started to decrease gradually at 74 min. With the increase in the temperature at the fifth step, the concentrations of CO and H2O still increased rapidly. The concentration of CO2 decreased, and the concentration of H2 changed slightly. The change in the gas concentration shows that CH4 started to participate in the reaction, producing CO and H2O. This inhibited further oxidation of CO but had no effect on H2, indicating that the reactivity of CH4 and H2 is much higher at 751−850 °C than that of CO. In the final stage, gas−solid and solid−solid reaction rates become slower and slower at the constant temperature, and each gas concentration became stable. 3.2.2. Reaction of Fe3O4 with CB and the Gas Mixture. Figure 5 shows the TG−MS curves of the reaction of Fe3O4
time (min)
range (°C)
mass loss (%)
DTGmax (%/min)
0−34 34−62 62−72 72−120
70−411 411−706 706−769 769−850
2.06 4 3.6 12.7
−1.45 −3.16 −0.82 −0.40
In comparison to the reactions of Fe2O3−CB with the gas mixture, which are divided into several obvious phases, the reactions of Fe3O4−CB in the gas mixture overlapped and led to only three peaks on the DTG curve. Figure 5b shows several peak values for each component concentration; they were used to analyze the properties of each reaction. No reaction occurred in the first period. According to the ratio of one reactant concentration to another reactant concentration, H2 has a much higher reactivity than CO and CB in the second stage. H2, CO, and CB are involved in the reactions. A sharp weight loss peak, mainly resulting from the consumption of CB, appeared in the third stage. As a result of the participation of CB in the reaction, the concentrations of CO and CO2 rapidly increased and the concentration of H2 slightly fluctuated. At the beginning of the
Figure 5. TG−MS curves of CB−Fe3O4 under gas mixture atmosphere. 2601
DOI: 10.1021/acs.energyfuels.7b03450 Energy Fuels 2018, 32, 2598−2604
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Figure 6. TG−MS curves of CB−FeO under gas mixture atmosphere.
Figure 7. TG−MS curves of the CB−mixture under gas mixture atmosphere.
final stage, CH4 is involved in the reaction, hindering the consumption of CO. This is because H2 and CH4 are highly competitive for lattice oxygen, which inhibits further oxidation of CO, decreasing the concentration of CO2 and increasing the concentration of H2O. After the temperature increased to the preset value, the concentration of each gas became stable. 3.2.3. Reaction of FeO with CB and the Gas Mixture. In the first stage, with the time ranging from 0 to 44 min, the weight loss was mainly caused by the evaporation of water, with a water loss rate of 4.9%. In addition, the adsorption of H2 affected the weight loss. At the beginning of the second stage, H2 started to participate in the reaction, thus gradually decreasing the H2 concentration and increasing the H2O concentration rapidly with the increase in the temperature. However, a significant weight loss was not observed in the TG curve as a result of the low reactivity of FeO under low temperature conditions (Figure 6a). At 62 min, the concentrations of CO and CO2 started to increase rapidly, indicating that CB starts to react with FeO. This marks the beginning of the third period when the concentration of CH4 did not change a lot. As observed in the third stage, along with the increase in the temperature, first, the weight loss rate accelerated before reaching the maximum at 71 min. The MS curves show that CO, H2, and CB are involved in the reaction (Figure 6b); the latter two are the main reactants. Consequently, the concentrations of CO, CO2, and H2O
increased dramatically, and the concentration of each gas reached the top value at 75 min. In the fourth period, starting from 75 min at 800 °C, CH4 dominated the reaction. With the increase in the temperature, the reaction rate first increased before reaching a maximum value at 82 min, followed by a gradual decrease when in a constant temperature zone. After the temperature increased to the present value, the concentration of each gas became stable. 3.2.4. Reactions of the OC Mixture with CB and the Gas Mixture. Figure 7 shows the DTG−MS curves for the reactions of the CB−OC mixture with the gas mixture, which are similar to that of the reaction of CB−Fe2O3 with the gas mixture. The initial reaction temperature increased from 423 to 531 °C when the concentration of hydrogen decreased dramatically and the concentration of water vapor increased rapidly. In 49− 73 min, the mass of the solid phase was lost rapidly, making it the fastest weight loss period, with strong fluctuations when the DTG curve has a “W” shape. In 49−66 min, only the H2 concentration decreased and the concentrations of CO2 and H2O increased among all of the gases, even though the concentration of CO2 slightly increased, much less than the H2O concentration. This shows that the reaction of H2 with OC occurs mainly in this period and only a small amount of CB with OC particles in the reaction. At 66 min (700 °C), the concentrations of CO and CO2 increased as a result of the acceleration reaction of CB with OC. However, the 2602
DOI: 10.1021/acs.energyfuels.7b03450 Energy Fuels 2018, 32, 2598−2604
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Energy & Fuels concentration of CO2 decreased at 68 min as a result of the inhibition in further oxidation of CO caused by the competitive reaction of CH4 with OC. The concentrations of H2O and CO reached the highest when the CH4 concentration became stable, corresponding to the minimum point of DTG at 80 min (800 °C). Among the reactions of CB with different types of iron-based OC, H2 has the lowest initial reaction temperature and highest competitiveness, indicating a high reactivity throughout the reaction (Table 8). In contrast, the reactivity of CO is poor, and Figure 8. SEM of the CB−mixture residue.
Table 8. Initial Temperatures of Each Competitive Reaction initial temperature (°C) H2 C CH4 CO
Fe2O3
Fe3O4
FeO
433 520 758 485
411 653 764 508
481 667 796 548
Table 10. EDS Result of the TG Residue of the Mixture Sample under a Syngas Atmosphere
CO is not only a reactant but also a product in the reaction. The curve for the CO2 concentration shows that CO has lower competitiveness than H2 in the reaction with OC below 750 °C. When the temperature exceeds 750 °C, CH4 competes for oxygen, causing the increase in the CO concentration and decrease in the CO2 concentration. The reaction of CB with the OC mainly produces CO, and the consumption rate is characterized by a single valley, which is affected by both the contact area and gas reaction, especially H2 and CH4. 3.3. Consumption of CB. The reaction of the sample mixture in solid−solid and gas−solid reactions reflects the competitive reaction results, causing the consumption of CB under different conditions. Corresponding to the consumption of CB, the concentrations of CO and CO2 increased. Therefore, the CB consumption could be calculated from carbon balance before and after the reaction, including the changes in CO, CO2, and CH4 contents. The mass spectra of CO, CH4, and CO2 were integrated and converted into the mass percent of CB using the NETZSCH Proteus thermal analysis software, as shown in Table 9.
CO CO2 CH4
mass percent (%)
1670.5 × 10−9 429 × 10−9 190
24.39 7.05 2.94
intense calibration
mass percent (%)
atomic percent (%)
C O Fe
30.74 22.93 112.17
0.5533 0.8716 0.9037
27.13 12.75 60.12
54.18 19.55 26.27
Table 11. EDS Result of the TG Residue of the Mixture Sample under a N2 Atmosphere element
element concentration signal (eV)
intense calibration
mass percent (%)
atomic percent (%)
C O Fe
20.24 22.08 113.79
0.5193 0.9800 0.9177
21.01 12.15 66.84
47.05 20.42 32.53
synthesis gas with OC, the Fe/O ratio of the OC is lower and the degree of reduction was deeper. Thus, the formation of larger images was the coking mixture of low-cost iron oxide and CB under a syngas atmosphere.
4. CONCLUSION Solidification and gas−solid reactions were studied. The initial temperature of reactions and the maximum reaction rate corresponding to the temperature were determined. By establishment of the corresponding relationship between the MS ion concentration and gas concentration, the reactivity of gas with OC was analyzed quantitatively. The main conclusions are as follows: (1) The TG−MS analysis shows that the initial reaction temperature of hydrogen was lower and remained stable with the highest reaction rate in the overall reaction. CO was senior to hydrogen at a low temperature, and the reaction rate sharply decreased at 700 °C. The initial reaction temperature of CH4 with OC was the highest. At this time, the reaction rate was much smaller than that of hydrogen gas. DTG of three samples showed that the reaction slowed as the state of the OC converted to elemental iron. (2) The gas concentration was analyzed quantitatively at different times via the corresponding relationship between the mass spectral ion concentration and gas concentration. When CB−iron oxide under a synthesis gas atmosphere is taken as an example, the reaction rate of hydrogen was about 0.44 mL/min, much higher than that of CO (0.33 mL/min) and CH4 (0.06 mL/min). By analysis of the concentrations of CO, CO2, and CH4 and conversion to the amount of carbon, the entire process of CB consumption of 28.7% was calculated. (3) The SEM−EDS analysis indicated that the content of CB in the solid−solid
Table 9. MS Integration and Mass Calculation integration (A−1)
element
element concentration signal (eV)
Table 9 shows that the CH4 consumption was smaller, the main carbon source that increased the concentrations of CO and CO2 originated from CB, and the consumption of CB was about 28.5% in the overall reaction of the OC mixture−CB with the syngas mixture. SEM−EDS was also used to characterize the solid mixture after the TG experiment, as shown in Figure 8. Figure 8 shows a small amount of CB accumulation on a large OC surface, and the pore microstructure is superior, providing stable conditions for the gas−solid reaction. In comparison to the EDS results of Tables 10 and 11, the CB surplus under a synthesis gas atmosphere is higher than that of the solidification reaction. Therefore, the gaseous components led the reactions with varying OCs to inhibit the CB consumption. In addition, as a result of the high reactivity of 2603
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(13) Cheng, Y.; Peng, G.; Wang, L.; Li, X. Kinetics of Burning Side Reaction in the Liquid-Phase Oxidation of p-Xylene. Chin. J. Chem. Eng. 2009, 17 (2), 181−188. (14) Oh, J.; Noh, D. The reduction kinetics of hematite particles in H2, and CO atmospheres. Fuel 2017, 196, 144−153. (15) Jang, W.-J.; Jeong, D.-W.; Shim, J.-O.; Kim, H.-M.; Roh, H.-S.; Son, I. H.; Lee, S. J. Combined steam and carbon dioxide reforming of methane and side reactions: Thermodynamic equilibrium analysis and experimental application. Appl. Energy 2016, 173, 80−91. (16) Barde, A. A.; Klausner, J. F.; Mei, R. Solid state reaction kinetics of iron oxide reduction using hydrogen as a reducing agent. Int. J. Hydrogen Energy 2016, 41 (24), 10103−10119.
reaction was small; thus, the CB consumption was high. In addition, the gas−solid reaction decreased the consumption of CB as a result of excellent reaction characteristics of gas components with OCs. However, the partial exothermic characteristic makes the OC and CB coke react together, affecting the activity of the OC.
■
AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. ORCID
Cuiping Wang: 0000-0002-4249-709X Notes
The authors declare no competing financial interest.
■
ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China (51676102) and the Natural Science Foundation of Shandong Province (ZR2015EM004). The authors greatly acknowledge the support from the Foundation of State Key Laboratory of Coal Clean Utilization and Ecological Chemical Engineering (Grant 2016-07) and the Taishan Scholar Program of Shandong Province (201511029).
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REFERENCES
(1) Linderholm, C.; Schmitz, M. Chemical-looping combustion of solid fuels in a 100 kW dual circulating fluidized bed system using iron ore as oxygen carrier. J. Environ. Chem. Eng. 2016, 4 (1), 1029−1039. (2) Li, J.; Zhang, H. D.; Gao, Z. P.; Fu, J.; Ao, W. Y.; Dai, J. J. CO2 Capture with Chemical Looping Combustion of Gaseous Fuels: An Overview. Energy Fuels 2017, 31 (4), 3475−3524. (3) Zhang, Y.; Doroodchi, E.; Moghtaderi, B. Reduction Kinetics of Fe2O3/Al2O3 by Ultralow Concentration Methane under Conditions Pertinent to Chemical Looping Combustion. Energy Fuels 2015, 29 (1), 337−345. (4) Fulcheri, L.; Probst, N.; Flamant, G.; Fabry, F.; Grivei, E.; Bourrat, X. Plasma processing:a step towards the production of new grades of carbon black. Carbon 2002, 40 (2), 169−176. (5) Siriwardane, R.; Riley, J.; Tian, H.; Richards, G. Chemical looping coal gasification with calcium ferrite and barium ferrite via solid−solid reactions. Appl. Energy 2016, 165, 952−966. (6) Xiao, R.; Zhang, S.; Peng, S.; Shen, D.; Liu, K. Use of heavy fraction of bio-oil as fuel for hydrogen production in iron-based chemical looping process. Int. J. Hydrogen Energy 2014, 39 (35), 19955−19969. (7) Li, Y. P.; Gong, J.; Huang, F.; Bai, H. C.; Wang, F. Y.; Wang, C. P. Carbon Deposition and Sintering Characteristics on Iron-Based Oxygen Carriers in Catalytic Cracking Process of Coal Tar. Energy Fuels 2017, 31 (6), 6501−6506. (8) Guo, Q.; Cheng, Y.; Liu, Y.; Jia, W.; Ryu, H.-J. Coal Chemical Looping Gasification for Syngas Generation Using an Iron-Based Oxygen Carrier. Ind. Eng. Chem. Res. 2014, 53 (1), 78−86. (9) Abad, A.; Mattisson, T.; Lyngfelt, A.; Johansson, M. The use of iron oxide as oxygen carrier in a chemical-looping reactor. Fuel 2007, 86 (7), 1021−1035. (10) Jiang, X.; Zhang, L. L.; Wang, F. Y.; Liu, Y. Z.; Guo, Q. J.; Wang, C. P. Investigation of Carbon Black Production from Coal Tar via Chemical Looping Pyrolysis. Energy Fuels 2016, 30 (4), 3535−3539. (11) Liu, L.; Li, Z.; Xi, J.; Zhou, H.; Wu, Z.; Qiu, X. Rapid detection of the positive side reactions in vanadium flow batteries. Appl. Energy 2017, 185, 452−462. (12) Jang, W.-J.; Jeong, D.-W.; Shim, J.-O.; Kim, H.-M.; Roh, H.-S.; Son, I. H.; Lee, S. J. Combined steam and carbon dioxide reforming of methane and side reactions: Thermodynamic equilibrium analysis and experimental application. Appl. Energy 2016, 173, 80−91. 2604
DOI: 10.1021/acs.energyfuels.7b03450 Energy Fuels 2018, 32, 2598−2604
