Test Operation of a Separated-Gasification Chemical Looping

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Test Operation of a Separated-Gasification Chemical Looping Combustion System for Coal Xudong Wang, Xiaojia Wang, Shuai Zhang, Zhiwei Kong, Zhaoyang Jin, Yali Shao, and Baosheng Jin Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.8b02857 • Publication Date (Web): 23 Oct 2018 Downloaded from http://pubs.acs.org on October 29, 2018

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Test Operation of a Separated-Gasification Chemical Looping Combustion System for Coal Xudong Wang,† Xiaojia Wang,*,† Shuai Zhang,†,‡ Zhiwei Kong,† Zhaoyang Jin,† Yali Shao,† Baosheng Jin*,† †

Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School

of Energy and Environment, Southeast University, Nanjing, 210096, China ‡

Shenhua Guohua (Beijing) Electric Power Research Institute Co., Ltd., Beijing, 100025, China

KEYWORDS: chemical looping combustion; test operation; cold condition; hot experiment

ABSTRACT: Chemical looping combustion (CLC) has been one of the most attractive topics for the clean utilization of the coal. Based on the staged-gasification of the solid fuel, a separatedgasification CLC apparatus for coal was established, which mainly consisted of a gasifier (GR), a reduction reactor (RR) and an air reactor (AR). This design separated the gasification of the coal avoiding the direct solid-solid contact between oxygen carriers and coal which was beneficial to lengthen the lifecycle of the oxygen carriers. The established system was tested under both cold and hot conditions. The variable conditions of different amounts of fluidized gas and the air into AR were carried out to verify the feasibility and the stability of this system. Results indicated that the system could be operated stably under the variable conditions, showing acceptable pressure distributions in the reactor system. In the hot operation, the concentration of CO2 at the outlet of RR reached a relatively high level (92.7%-93.2%) while the CO2 concentration at the

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outlet of AR was 0.93%-1.12% during the stable durations. However, there was still a problematic condition, unstable operation of coal screw feeder, which needed improving further.

1. INTRODUCTION To deal with the greenhouse effect, the carbon capture and storage technologies have been the hot topics including integrated gasification combined cycle (IGCC), oxy-fuel combustion, CO2 absorption and separation et al. [1-8]. Chemical looping combustion (CLC) is a novel CO2 separation technology during the combustion process of fuels without extra energy consumption proposed by Richter [9]. The combustion of gaseous fuel has been deeply investigated in different kinds of sub-pilot or pilot setups [10-19]. Successful operations were conducted with different fuels (natural gas, refinery gas, methane etc.) and oxygen carriers (Ni-, Cu-, Mn-, Fe-based etc.) [12, 13, 16-21]. In the chemical looping combustion for gaseous fuel, the fuel reacts with oxygen carriers in the fuel reactor to realize the non-flame combustion. There is light and continuous attrition between the oxygen carrier and the gas to decrease the amount of oxygen carrier [22, 23]. In-situ gasification chemical looping combustion (iG-CLC) is a promising technology for solid fuels, principally shown as Figure 1. In the iG-CLC, it always consists of fuel reactor (FR) and air reactor (AR). Once the coal is fed into the fuel reactor, the pyrolysis process carries on. Meanwhile, the coal and the char from the pyrolysis are gasified by the gasification agent. Then, the gasified production, fuel gas, reacts with the oxygen carrier (MmOn) in the fuel reactor to realize the non-flame combustion, producing CO2 and H2O. After condensation, the pure CO2 can be captured. In the air reactor, the reduced oxygen carrier is regenerated with the oxidation of air.


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Figure 1. Principle diagram of iG-CLC. There have been many sub-pilot or pilot setups for solid fuels. At Chalmers University of Technology in Sweden, Berguerand et al. designed a CLC system consisting of two interconnected fluidized beds where the fuel reactor was a bubbling bed and the air reactor was a circulated fluidized bed. The tests of South African coal and petroleum coke had reached 82.5% to 96% in CO2 capture [24-26]. Linderholm et al. [27] redesigned the fuel feed of this system into the bubbling bed section to improve the contact between oxygen carrier and fuel, which significantly improved the gas conversion. Markström et al. [28, 29] improved and rebuilt a 100 kWth CLC unit, in which the fuel reactor was a circulating fluidized bed. A 20 kWth coal-fired iG-CLC system were designed and built by Adánez et al. [30, 31] at Instituto de Carboquímica (ICB-CSIC) in Spain. The FR was operated in turbulent fluidized regime while the bottom and up sections of air reactor were bubbling bed and fast fluidized bed. It also could be operated as


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the unit of 50 kW chemical looping with oxygen uncouple (CLOU). The optimized operation parameters were obtained in experiments [32]. Ströhle et al. [33, 34] designed and operated the world largest CLC pilot plant with the thermal inputs of 1 MW which consisted of two interconnected circulating fluidized bed reactors at Technische Universität Darmstadt. Bayham et al. [35,36] adopted the fast fluidized bed and counter-current moving bed as AR and FR respectively for coal direct chemical looping combustion at the Ohio State University. The coal was fed into the moving bed and reduced by oxygen carriers. Shen et al. [37, 38] established and operated 10 kW and 1 kW CLC units for solid fuels successively where the FR and AR were spout-fluid bed and fast fluidized bed respectively at Southeast University in China. The spoutfluid bed could enhance the solids mixing and lengthen the particle residence time, which were beneficial to the conversion of solid fuels. The performances were investigated in these units with different kinds of solid fuels, such as coal, sewage sludge and biomass etc. [39-43]. Wang et al. [44] have successfully operated the high-flux CFB as the coal CLC pilot. Xiao et al. [45] built a pressurized chemical looping combustion system for coal consisting of fast and turbulent fluidization beds as FR and AR respectively. The test with Shenhua coal showed high CO 2 concentration, carbon conversion and combustion efficiency. Ma et al. [46] published the operation results of an interconnected fluidized bed reactor CLC system for coal whose thermal inputs were 2 kW to 6 kW at Huazhong University of Science and Technology. The FR and AR were operated in the bubbling bed and turbulent bed regimes. No matter what kind of the chemical looping combustion system was, the solid fuels were fed into the dense phase zone in the above units. Some problems are still in the process of CLC: (1) In the iG-CLC, besides the gasification agent, the solid fuel also contacts with the oxygen carrier so that the oxygen carrier is reduced by the solid fuel simultaneously. The direct contact of these


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solids can lead to severe attrition of the oxygen carrier [47-51]. (2) The process of iG-CLC requires enough residence time for solid fuels in the fuel reactor to achieve the full conversion. If it cannot be realized, there would be much residual carbon at the outlet of the FR, resulting in a low combustion efficiency. The sufficient gasification in iG-CLC is the foundation of the full conversion for the solid fuel. It can lead to the decrease of the solid fuel particles and increase the concentrations of the gaseous fuels in the FR. The gas-solid reaction is much easier than the solid-solid reaction due to the platitudinous contact area of the reactants. In addition, the high gas concentration contributes to the reduction of the oxygen carrier. Thus, length the gasification process should be accounted into the design of the iG-CLC unit. Based on the above concepts, we designed and established a separated-gasification chemical looping combustion system for solid fuels, principally shown as Figure 2. In this system, a bubble bed was adopted as the gasifier where the coal was gasified with the heating and mixing of the bed material. A circulating fluidized bed riser was employed as the reduction reactor where the syngas reacted with the oxygen carrier. A moving bed was set in the middle of the downcomer of the circulating fluidized bed and used as air reactor. There are some merits of this design: (1) In the bubble bed, the gas velocity is relatively low, offering the condition for a long residence time of coal particles. What’s more, the solids mixing is strong and the internal circulation of the bed materials contributes to the effective heating of the coal, which is benefit to the gasification of the solid fuel. (2) In a circulating fluidized bed riser, the sufficient gas-solids contacts can promote the non-flame combustion of the syngas. (3) The set of the air reactor made the setup compact and controllable. (4) The oxygen carrier circulates in the reduction reactor and air reactor, avoiding the direct solid-solid contact with coal, which is of significance for the lifecycle of oxygen carrier.


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CO2, H2O

Dust Remover Second-stage separator

First-stage separator Air outlet Air Reactor

Air inlet

Second-stage J-valve

Reduction Reactor

First-stage J-valve

A-A sand oxygen carrier coal residual carbon/char coal ash

A-A

Gasifier Coal

Gasification agent

Figure 2. Operation mechanism and the pathways of the particles. In this work, the three-reactor iG-CLC system was put forward and established. Using the quartz sand as bed material and Chinese iron-based ore as oxygen carrier, cold experiment was conducted to validate the feasibility and operation stability of this system. The different fluidizing numbers in the reduction reactor and air reactor were changed respectively to investigate the flow characteristics and the pressure distribution in the system. Based on the operation experience of the cold experiment, hot test was carried out on this system with Chinese


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Shenhua coal as fuel. The test operation mainly focused on the thermal stability of the system and the ability of the CO2 capture, which was the foundation of the further studies for coal-fueled CLC on this system.

2. EXPERIMENTAL In iG-CLC system, the solid fuel is gasified in the fuel reactor while the gasified syngas reacts with oxygen carriers. As has been mentioned in the previous part, the direct contact between the oxygen carrier and the solid fuel could cause some problems. Based on the concept of separated gasification of solid fuels proposed in the introduction, we designed a fluidized bed reactor system for the chemical looping combustion. The separated-gasification chemical looping combustion apparatus was constructed, shown as Figure 3 and Figure 4. 2.1. Experimental Setup 2.1.1. Assembly of the Experimental Setup The reactor system consists of a gas chamber, gasifier (GR), reduction reactor (RR), air reactor, first-stage separator, first-stage downcomer, first-stage J valve, second-stage separator, second-stage downcomer, second-stage J-valve and coal feeder. The gas chamber’s inner diameter and height are 50 mm and 500 mm respectively. The gasifier and reduction reactor are configured as conventional fuel reactor. The inner diameter of the gasification reactor is 50 mm with its height of 500 mm. The reduction reactor is a fast fluidized bed and its inner diameter and height are 34 mm and 6500 mm respectively. The air reactor is a countercurrent moving bed whose inner diameter and height are 530 mm and 600 mm respectively. 2.1.2. Auxiliary Systems


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(a) Heating system. The fuel reactor, consisting of gasifier and reduction reactor, and the air reactor are provided with a plurality of auxiliary electric heating devices, which are used for heating in the startup process and ensuring the stability of the reaction temperature to cope with the heat dissipation. The Fuzzy PID is adopted as the temperature controller to stabilize the temperature deviation in the range of ±10 ℃. The other equipment and pipelines are covered with thermal insulation materials. (b) Monitoring system. Six temperature measurement points are located from the gas chamber to the upper part of the reduction reactor along the height direction while six pressure measurement points are set at the same locations whose heights are 250 mm, 850 mm, 1550 mm, 2800 mm, 4700 mm and 7400 mm from the bottom of gas chamber. A temperature measurement point is placed on the air reactor while a differential pressure sensor is put to monitor the pressure drop of the inlet and outlet air of the AR. All the temperature and pressure information are acquired and converted to electrical signals, then saved in the data processing system. The electromagnetic flowmeters used in the system has the function of displaying temperature and pressure. (c) Gas analysis system. The flue gas of fuel reactor and air reactor are filtered, desiccated and cooled separately. Then they are analyzed using MRU gas analyzer.


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measurement points

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P DP

T

25

24

vent

P

10

7 19

20

T

6

P

T

5

P

T

4

P

T

3

P

18

vent

23 T

20

19

18 T

21

12

DP

8

b P T

16 21 15 T

26

c T

9

P

P

11

21

d

14

13

A-A

T

A-A

21

P

2

21 22

27

T

1

P

a

17 1-gas chamber

26 26

2-gasifier

3-lower part of reduction reactor

6-upper part of reduction reactor

10-second-stage separator

7-first-stage separator

11-second-stage J-valve

14-second-stage superheater 15-commingler 19-gas cooler

20-gas analyzer

24-measurement system

4,5-medium part of reduction reactor 8-air reactor

12-air compressor

9-first-stage J-valve

13-first-stage superheater

16-air preheater 17-water pump 18-gas filtering and dryer

21-flowmeter

22-coal screw feeder

25-data processing and control system

26-N2 cylinder

23-expansion joint

27-steam generator

Figure 3. Apparatus sketch of the separated-gasification CLC reactor system.


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Temperature Controllers

Air Reactor Reduction Reactor

Coal Feeder Controller

Temperature & Pressure Monitoring System

Gasifier

(a)Reactor system

(b) control and monitoring system

Figure 4. Photographs of the experimental setup. 2.2. Operation Mechanism The operation mechanism of this CLC system and the particles’ pathways are shown as Figure 2. During the experimental process, the coarse quartz particles were conducted as the bed material in the bubble bed gasifier. When the solid fuel is put into the gasifier, it is gasified with the gasification agent assisted with the accumulated heat of quartz sand filled in the gasifier. In this section, the coarse particles and the low gas velocity made the flow regime in bubbling bed regime. The granular backmixing results in the internal circulation (shown as the red arrows), which is beneficial to lengthen the residence time of the fuel for full gasification. Due to the relatively long residence time in bubble bed, the concentration of syngas is high at the lower part of the reduction reactor. The oxygen carriers are recycled to the lower part of the


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reduction reactor and react with gasified syngas. The returning point of the circulating oxygen carrier is above the gasifier which can reduce (even avoid) the direct solid-solid contact between the oxygen carrier and the solid fuel. The mixture of produced flue gas in reduction reactor and the reduced oxygen carrier flows into the first-stage separator. Separated oxygen carriers after the first-stage separator fall into the air reactor. In the air reactor, the reduced oxygen carrier is regenerated by the oxidization of the air. The detailed pathway of the oxygen carrier is shown as the yellow marks in the Figure 2. The separated gas and the fine particles (such as unconverted char and coal ash) from the firststage separator flow into the second-stage cyclone separator which aims to separate the little amount of unconverted char particles in flue gas. If there are some char particles, they will be recycled into gasifier through the second-stage J-valve. After the second-stage separator, the flue gas is filtered and cleaned with the main remaining compositions of CO2 and H2O. 2.3. Experimental Material A kind of Chinese lean iron ore was chosen as the oxygen carrier. Prior the experiment, the iron ore was crushed and sieved to a size range of 0.35-0.83 mm. The apparent density of the particles is about 2930 kg/m3 while the bulk density is about 1600 kg/m3. The critical fluidization velocity umf of this oxygen carrier is 0.32 m/s at environment temperature. The BET and XRF results of the oxygen carrier were shown as Table 1 and Table 2. Table 1 BET result of lean iron ore OC item

Test result

pore diameter/nm

7.132

Specific area/m2 g-1

0.54312

pore volume/cm3 g-1

0.00117


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Table 2 The XRF analysis result of lean iron ore OC Component

Fe2O3

SiO2

Al2O3

CaO

MgO

SO3

others

Mass fraction/%

44.16

18.93

2.98

17.09

7.43

2.35

7.06

During the experimental process, the sand particles with diameter of 1.70-3.35 mm were used as bed materials in the bubbling bed whose apparent and bulk densities were about 2610 kg/m3 and 1220 kg/m3. The critical fluidization velocity and terminal velocity were 0.95-1.56 m/s and 13.73-27.05 m/s respectively under the cold conditions. The coarse particles of the sand could be fluidized in the bubble regime in the gasifier. Chinese Shenhua coal was used as the solid fuel in the thermal experiment test. The coal was also sieved to a size range of 0.35-0.83 mm. The proximate analysis and ultimate analysis were shown in Table 3. The lower heat value(LHV) was about 26.32 MJ/kg. Table 3. Proximate analysis and ultimate analysis of Shenhua coal Proximate analysis (wt%)

Ultimate analysis (wt%)

Mar

Var

FCar

ASHar

Cd

Hd

Od

Nd

Sd

9.75

31.71

52.37

6.17

73.63

4.65

13.46

0.94

0.48

3. OPERATION UNDER COLD CONDITIONS To test the reliability and stability of this new system, the experiment under cold condition were conducted. Before the process, some sieved quartz particles were added in the bubble bed with the bed height of about 300 mm. At the same time, about 155 kg oxygen carriers were put into the reactor system.


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In the initial test process of the experiment, the second-stage downcomer was not put into application. The gas flow rate of the fluidized gas and the air into AR were changed to investigate the effects of gas flow on the pressure distribution of the reactor system. 3.1. Effects of the Fluidized Gas The fluidized gas was the main gasification agent of coal. The amount of the gas directly influenced the resistance time of the coal in the gasifier and the resistance time of oxygen carriers in the reduction reactor, which would affect the combustion efficiency of the coal in the hot experiment. Thus, the fluidized gas was an important operation parameter in the system. Under the cold condition, the effects of fluidized gas were investigated. The fluidizing number in reduction reactor Nr (the ratio of the superficial gas velocity in the reduction reactor to the minimum fluidizing velocity of the oxygen carrier) was changed while the fluidizing number in the air reactor Na (the ratio of the superficial gas velocity in the air reactor to the minimum fluidizing velocity of the oxygen carrier) kept constant. The detailed test conditions were listed in Table 4. Table 4 The test conditions of fluidized gas Test

1

2

3

4

5

Nr

19.40

21.25

23.10

24.95

26.80

Na

0.13

0.13

0.13

0.13

0.13

For the test operation, the test 4 was set as the fundamental condition. The pressure changes at the measurement points 1 to 6 and the pressure drops in different sections of the system during the operation process were shown in Figure 5.


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(a)

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(b)

Figure 5. Pressure changes in the reactor system during test 4: (a) pressures changes at measurement points; (b) pressure drops in the reactor system. Figure 5 illustrated that the pressures at P1 to P6 fluctuated near the certain values correspondingly. That demonstrated that the system operated under relatively stable conditions. The pressures showed a decreasing trend from P1 to P6, whose means were about 28.83kPa, 24.42kPa, 14.80kPa,10.22kPa, 7.80kPa and 6.77kPa. From the figure, it could also be found that the fluctuation amplitudes in the lower parts of the fuel reactor were a little larger than those in the upper parts. In the Figure 5(b), the pressure drops in the different parts of the reactor system were calculated from the measured values in Figure 5(a) except for the ΔPAR. ΔPAR was obtained by the differential pressure sensor DP in Figure 3. ΔP1-2 was the pressure destruction of the distributor. ΔPFR was the pressure drops between P2 and P6 while ΔPRR was the pressure difference between P3 and P6. The pressure drops of ΔP1-2, ΔPFR, ΔPRR and ΔPAR were about 4.41kPa, 17.65kPa, 8.03kPa and 1.89kPa separately. Results demonstrated that the pressure drop in air reactor was stable with slight fluctuations. The moving bed was stabler than other kinds of fluidized beds, which was beneficial for the stability of the air reactor and the full oxidization of oxygen carriers.


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When the system operated under the conditions listed in Table 4, the mean pressures at the different measurement points were obtained, shown as Figure 6.

(a)

(b)

Figure 6. Pressure changes in the whole system during different test conditions: (a) pressure distributions in the reactor system; (b) pressure drops in different reactors. Results illustrated that the pressures in the reactor increased with the number of Nr. The highest pressure, P1, was approximately 23.91 kPa in test 1, and it increased to about 30.93 kPa in test 5 while the P6 increased from near 3.52 kPa in test 1 to 7.37 kPa in test 5. Along the height direction, the pressure declined with an accelerating trend. This demonstrated that in the lower section of the FR, the particle concentration was dense herein and it became dilute in the upper part. Pressure drops in Figure 6(b) showed that ΔP1-2 increased from 2.65 kPa to 4.32 kPa with the climbing of the fluidized gas which matched with the pressure destruction property of the distributor. The ΔPFR and ΔPRR were relative stable with a slight declination in the first three or four tests. However, the different trend occurred in the test 5. This might be due to the reason that the average pressures were obtained from the measured information with relatively large fluctuations, which might cause the deviations from the real pressure. However, it is obvious that the pressure drop ΔPAR was stable under different test conditions, which was about 1.89 kPa.


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3.2. Effects of the Air into the AR To investigate the performance of the air reactor, the number of Na was changed from 0.10 to 0.19 with the interval of 0.03 while the Nr kept constant as 24.95. The pressure drops in the reactor system were presented in Figure 7.

Figure 7. Pressure drops in the reactor system with different Na. The pressure drop ΔPAR increased with the Na showing a linear relationship, whose specific values were about 1.58 kPa, 1.89 kPa, 2.57 kPa and 3.21 kPa in different tests. In this process, the air flow could not fluidize the oxygen carrier particles in AR. The oxygen carrier particles dropped from the first-stage separator forming the contra-flow with the air in AR. The air flowed out form the AR at the outlet which could not affect the flow pattern in FR. Thus, the variation of Na had no effect on the pressure drops of ΔP1-2, ΔPFR and ΔPRR which kept constants near 4.44 kPa, 17.64 kPa and 8.03 kPa separately in the process of variable conditions. The cold experiment showed that this system was stable in the operation process. The cold operation experience could be referenced in the thermal experiment.


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4. THERMAL EXPERIMENT TEST AND DISCUSSIONS 4.1. The Test Operation Process Thermal test was conducted to investigate the coal chemical looping combustion process. The test operation was divided into five periods as shown in Figure 8, which were startup period (I), stabilization periods (II and IV), coal combustion process (III) and shutdown and blowing period (V).

Figure 8. Temperature change curves at different sensors during the thermal test. In the startup process, the reactor system was heated in the air atmosphere. The heaters were set at different temperatures which climbed gradually. The temperature of gas chamber was set 50 ℃ higher than those of other parts of the gasifier and reduction reactor to guarantee the gas could be fully heated. The final temperature of T1 was set as 900 ℃ while T2 to T6 were set as 850 ℃. During the period II, the temperatures of the system was stable. The N2 and H2O were gradually introduced to replace the air of the fluidized gas and loosen gas. Although there could


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be some small fluctuations of the temperatures, they could be steady at the set parameters quickly. The coal chemical looping combustion process was described and analyzed in details in the next section. The conditions were listed in Table 5. Table 5 the operation conditions of coal CLC process in thermal test TGR

TRR

TAR

QH2O

QN2

Coal feeding rate

850 ℃

850 ℃

900 ℃

8.64 kg/h

2.25 kg/h

1.5 kg/h

During the period IV, the fluidized gas and loosen gas were switched as air by degrees. Little temperature deviations could be eliminated by adjusting the air flow. Finally, the electric heater was cut off. Due to the insulation materials, the cooling process lasted more than 12 hours. 4.2. Coal Chemical Looping Combustion Period The coal chemical looping combustion process consisted of three durations as shown in Figure 9. About 2.3 kg coal was fed into the reactor in the initial one (III1). However, the FR gas channel and sampling tube of analyzer were blocked later, the sweeping process was following (III2). In the last duration, supplement of 4.1 kg coal was fed into the reactor by the screw again. Two processes of coal feeding could be reflected in the temperature curve and concentration curve (shown as Figure 9) evidently. The endothermic coal gasification led to the great temperature drop, later the electric heater recovered the declines, which formed the temperature valley in Figure 8. The concentrations of CO, CO2 and CH4 at the outlet of FR were plotted in Figure 9.


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Figure 9. The gas concentrations (dry and N2 free basis) at the outlet of FR in period III. In duration III1, once the coal was fed into the gasifier, it was gasified with H2O. The gasified gases reacted with oxygen carrier. In this period, the CO2 concentration increased while the CO and CH4 concentrations decreased simultaneously. Some minutes later, the CO2 concentration could reach to a relatively stable value which was 92.7% (±2.5%). The production of large amount of CO2 led to the declination of the concentrations of CO and CH4, which were near 4.2% ( ± 2.0%) and 3.1% ( ± 1.4%) respectively. Due to the system fluctuations and measurement noises, there were some changes of the curves. During time interval of III2, the air was pumped to sweep the sampling tube following the FR. At the same time, the block of gas channel made the circulation of oxygen carrier not continuous, thus the coal reacted with H2O producing higher concentrations of CO and CH4. The data acquired in this period could not reflect the real reaction situation. The undulations were caused by the instability of air. In the following duration, after dealing with the problems in III2, the produced flue gases of FR ran a similar trend with those in duration III1. It was illustrated that the stabilization time was


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longer than that of III1. The stable concentrations of CO2, CO and CH4 are 93.2% (±2.2%), 3.2% (±2.7%) and 3.3% (±1.7%) separately. The gas concentrations at the outlet of AR was illustrated in Figure 10. It demonstrated that when the coal was fed into the reactor system, gasified syngas resulted in the expansion of the gas fraction. The combustion production CO2 was greatly produced which led to the increase of pressure drop in the reduction reactor. Due to the climbing of the pressure in reduction reactor, some CO2 blew into the air reactor. In addition, more incombustible char could be carried into the air reactor, which resulted in the increase of CO2 concentration in the flue gas of air reactor. When the reactor system operated under a stable condition, the CO2 concentration and pressure drop of reduction reactor ΔPRR declined to a relatively steady state. The expansion of the gas fraction also caused the decrease of ΔP1-2 in the initial period.

Figure 10. CO2 concentration at the outlet of AR in period III. A small peak of CO2 concentration occurred when the coal was supplied for a second time. Same trend was observed in the pressure curve of ΔPFR and ΔPRR. Figure 11 illustrated that the pressure drop in air reactor was very stable, which benefited from the property of countercurrent


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moving bed and matched well with the cold condition operation results. The pressure changes in the fuel reactor almost had no effect on the air reactor.

Figure 11. Pressure drops of the reactor system in period III. However, the results also demonstrated that the coal screw feeder needed to be improved for the reason that the feeding amount was large deviating from the stable operation when the supplement was added into the bin. Due to the problematic conditions of III2, the carbon conversion could not be calculated exactly. 4.3. SEM-EDS Results of the Oxygen Carriers To evaluate the performance changes of the oxygen carrier circulated in the established separated-gasification CLC unit, the fresh oxygen carrier and the oxidized oxygen carrier after the thermal test operation (used oxygen carrier) were characterized by SEM-EDS. The results were shown in Figure 12.


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Energy & Fuels

O

Intensity

Fe

Fe MgAl

Ca

(a)

Fe

Si

0

Ca

2

4

Energy E/keV

6

8

O Fe

Intensity

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

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Fe Ca

Fe

Si

Ca

MgAl

(b)

0

2

4

6

8

Energy E/keV

Figure 12. SEM-EDS analyses of the oxygen carriers: (a) fresh oxygen carrier; (b) used oxygen carrier. The SEM results showed that the morphological characters of the oxygen carriers were different. The surface of the fresh oxygen carrier was smooth and covered with plate-like crystals compactly. After thermal operation, the surface of the oxygen carrier became rough and the plate-like crystals of the used oxygen carrier were much less than the fresh one. There were also some small grains on the rough surface. During the operation, the redox cycles of the oxygen carrier caused the movement of the lattice oxygen and Fe circularly, forming some voids and


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grains on the oxygen carrier. It was concluded that light sintering was experienced by the oxygen carrier particle during the operation. As a result, the formed voids would increase the contact area between gas and solid while the sintering would cause a reduction of the area. The spectrums of the fresh and used oxygen carriers presented a similar element distribution and a same trend as well. The major elements detected on the particles’ surfaces were Fe, O, Si and Al. It was seen that the Ca in the used oxygen carrier was obvious. That might be the effects of the ash deposition.

5. OPEN DISCUSSIONS AND FURTHER IMPROVEMENT The new system exhibited stable performance under cold and thermal operations. And the test operation of thermal experiment also obtained a relatively high concentration of CO2. However, some problems appeared in the test which need to be discussed further. (1) The heat accumulation of quartz sand in bubble bed. In the Figure 8, the temperatures decreased in gasifier when the coal was fed into the reactor. In the anticipation, the heat storage of quartz sand was expected to offer the heat required for gasification. However, there was a great declination of the temperature. This is a problem for the future auto-thermal operation of this system. The sand inventory needs to be optimized according to the coal feeding amount. (2) Unstable operation of coal screw feeder. The great temperature drop in the III2 also might be caused by the instability of the coal feeding. In the coal feeding process, there was a small amount of wind as the feeding agent which was used to avoid the block of coal due to the screw extrusion. However, due to the gas, the fed quantity of the coal by the screw deviated from the calibrated one. The large coal feeding into the reactor could cause a large temperature drop.


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(3) The blocks of sampling tube and oxygen carrier circulation. These cause the problematic conditions of III2, which were harmful for the steady operation of the system. For the sampling tube, it will be improved to be wider in diameter and a dust elimination step should be set. The block of the oxygen carrier is mainly caused by the unstable quality of the steam, which will be dealt with by setting assistance heater along the steam piping. Additionally, the temperature and pressure controllers of the steam generator should have higher control precisions. (4) Auto-thermal operation. Due to the temperature disequilibrium between air reactor and fuel reactor, the cycled oxygen carriers not only transferred the lattice oxygen, but also acted as the heat transfer medium between two reactors. The oxygen carrier would be greatly heated in the air reactor due to the exothermal reaction, then it released heat in the fuel reactor. In this case, the reaction temperature in the fuel reactor depended on the air reactor. It could not be guaranteed that the reaction in the fuel reactor took place at the optimal reaction temperature. Additionally, the oxidization reaction in the air reactor may lead to the sintering of oxygen carriers. In the future study, this unit is suspected to operate under auto-thermal condition and make the oxygen carrier free from the medium of heat transfer. There will be some oxygen added into the gasification agent. As is well acknowledged, the coal gasification with steam is an endothermal reaction while the gasification with oxygen is an exothermal reaction. By the means of the hybrid gasification agent, the thermal condition can be self-sufficient in the gasifier. The reaction conditions in the reduction reactor and the air reactor can be set as their optimal temperatures which are beneficial to increase the conversion rate and the combustion efficiency.

6. CONCLUSIONS A separated-gasification CLC system for coal was designed and established. The test operations under cold and hot conditions were conducted to investigate the stability and


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performance of this system. According to the results obtained, conclusions can be drawn as followings: (1) The designed iG-CLC system could offer sufficient gasification time for the coal in principle and the solid-solid contact between oxygen carrier and coal would be avoided. (2) Under cold conditions with different operation parameter sets, this designed unit for iGCLC could be operated with stable fluid performance, exhibiting good pressure distributions, which demonstrated the feasibility and the stability of the system. (3) The hot operation demonstrated that the system could be employed into the iG-CLC for coal. In the coal chemical looping combustion process, the CO2 capture could reach a relatively high level which was in the range from 92.7% to 93.2%. (4) Some problems occurred during the operations would be dressed further.

AUTHOR INFORMATION Corresponding Author * Baosheng Jin, Email: [email protected] Xiaojia Wang, Email: [email protected]

Notes The authors declare no competing financial interest. ACKNOWLEDGMENT


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This work has been financially supported by the National Natural Science Foundation of China (51676038, 51741603 and 51706041), the Natural Science Fund project in Jiangsu Province (BK20170669), the Fundamental Research Funds for the Central Universities (2242018K40117), and the Guangdong Provincial Key Laboratory of New and Renewable Energy Research and Development (Y707s41001).

REFERENCES 1. B. Sreenivasulu, D.V. Gayatri, I. Sreedhar, K.V. Raghavan, A journey into the process and engineering aspects of carbon capture technologies. Renew Sust Energ Rev. 2015, 41, 13241350. 2. M.E. Boot-Handford, J.C. Abanades, E.J. Anthony, M.J. Blunt, S. Brandani, N. Mac Dowell, J.R. Fernández, M. Ferrari, R. Gross, J.P. Hallett, R.S. Haszeldine, P. Heptonstall, A. Lyngfelt, Z. Makuch, E. Mangano, R.T.J. Porter, M. Pourkashanian, G.T. Rochelle, N. Shah, J.G. Yao, P.S. Fennell, Carbon capture and storage update, Energy Environ. Sci. 2014, 7, 130189. 3. J.R. Fernández, J.C. Abanades, CO2 capture from the calcination of CaCO3 using iron oxide as heat carrier. J Clean Prod. 2016, 112, 1211-1217. 4. A.M. Kierzkowska, C.R. Mller, Development of calcium-based, copper-functionalised CO2 sorbents to integrate chemical looping combustion into calcium looping. Energy Environ. Sci. 2012, 5, 661-665. 5. Y. Cao, B. He, G. Ding, L. Su, Z. Duan, Energy and exergy investigation on two improved IGCC power plants with different CO2 capture schemes. Energy. 2017, 140, 47-57.


26

Page 27 of 32 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

6. L. Petrescu, C. Cormos, Environmental assessment of IGCC power plants with precombustion CO2 capture by chemical & calcium looping methods. J Clean Prod. 2017, 158, 233244. 7. A. Nandy, C. Loha, S. Gu, P. Sarkar, M.K. Karmakar, P.K. Chatterjee, Present status and overview of Chemical Looping Combustion technology. Renew Sust Energ Rev. 2016, 59, 597619. 8. M.K. Mondal, H.K. Balsora, P. Varshney, Progress and trends in CO2 capture/separation technologies: A review. Energy. 2012, 46, 431-441. 9. H.J. Richter, K.F. Knoche, Reversibility of combustion processes, ACS Publications, 1983. 10. C. Linderholm, A. Abad, T. Mattisson, A. Lyngfelt, 160h of chemical-looping combustion in a 10kW reactor system with a NiO-based oxygen carrier. Int J Greenh Gas Con. 2008, 2, 520530. 11. S. Wang, G. Wang, F. Jiang, M. Luo, H. Li, Chemical looping combustion of coke oven gas by using Fe2O3/CuO with MgAl2O4 as oxygen carrier. Energy Environ. Sci. 2010, 3, 13531360. 12. J. Adánez, Chemical looping combustion of gaseous fuels, Elsevier, 2015. 13. A. Abad, T. Mattisson, A. Lyngfelt, M. Ryden, Chemical-looping combustion in a 300W continuously operating reactor system using a manganese-based oxygen carrier. Fuel. 2006, 85, 1174-1185. 14. S. Penthor, K. Mayer, S. Kern, H. Kitzler, D. Wöss, T. Pröll, H. Hofbauer, Chemicallooping combustion of raw syngas from biomass steam gasification – Coupled operation of two dual fluidized bed pilot plants. Fuel. 2014, 127, 178-185.


27

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 28 of 32

15. F. Zerobin, S. Penthor, O. Bertsch, T. Pröll, Fluidized bed reactor design study for pressurized chemical looping combustion of natural gas. Powder Technol. 2017, 316, 569-577. 16. C. Linderholm, E. Jerndal, T. Mattisson, A. Lyngfelt, Investigation of NiO-based mixed oxides in a 300-W chemical-looping combustor. Chem Eng Res Des. 2010, 88, 661-672. 17. S. Penthor, F. Zerobin, K. Mayer, T. Pröll, H. Hofbauer, Investigation of the performance of a copper based oxygen carrier for chemical looping combustion in a 120kW pilot plant for gaseous fuels. Appl Energ. 2015, 145, 52-59. 18. P. Moldenhauer, M. Rydén, A. Lyngfelt, Testing of minerals and industrial by-products as oxygen carriers for chemical-looping combustion in a circulating fluidized-bed 300W laboratory reactor. Fuel. 2012, 93, 351-363. 19. T. Mattisson, M. Johansson, A. Lyngfelt, The use of NiO as an oxygen carrier in chemicallooping combustion. Fuel. 2006, 85, 736-747. 20. A. Shulman, C. Linderholm, T. Mattisson, A. Lyngfelt, High Reactivity and Mechanical Durability of NiO/NiAl2O4 and NiO/NiAl2O4/MgAl2O4 Oxygen Carrier Particles Used for more than 1000 h in a 10 kW CLC Reactor. Ind Eng Chem Res. 2009, 48, 7400-7405. 21. M. Rydén, M. Johansson, A. Lyngfelt, T. Mattisson, NiO supported on Mg-ZrO2 as oxygen carrier for chemical-looping combustion and chemical-looping reforming. Energy Environ. Sci. 2009, 2, 970-981. 22. P. Knutsson, C. Linderholm, Characterization of ilmenite used as oxygen carrier in a 100kW chemical-looping combustor for solid fuels. Appl Energ. 2015, 157, 368-373. 23. F. Liu, Y. Zhang, L. Chen, D. Qian, J.K. Neathery, S. Kozo, K. Liu, Investigation of a Canadian Ilmenite as an Oxygen Carrier for Chemical Looping Combustion. Energ Fuel. 2013, 27, 5987-5995.


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Page 29 of 32 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

24. N. Berguerand, A. Lyngfelt, Chemical-Looping Combustion of Petroleum Coke Using Ilmenite in a 10 kWth Unit-High-Temperature Operation. Energ Fuel. 2009, 23, 5257-5268. 25. N. Berguerand, A. Lyngfelt, Design and operation of a 10kWth chemical-looping combustor for solid fuels - Testing with South African coal. Fuel. 2008, 87, 2713-2726. 26. N. Berguerand, A. Lyngfelt, Operation in a 10 kWth chemical-looping combustor for solid fuel—Testing with a Mexican petroleum coke. Energ Procedia. 2009, 1, 407-414. 27. C. Linderholm, A. Lyngfelt, A. Cuadrat, E. Jerndal, Chemical-looping combustion of solid fuels-Operation in a 10kW unit with two fuels, above-bed and in-bed fuel feed and two oxygen carriers, manganese ore and ilmenite. Fuel. 2012, 102, 808-822. 28. P. Markström, C. Linderholm, A. Lyngfelt, Chemical-looping combustion of solid fuelsDesign and operation of a 100kW unit with bituminous coal. Int J Greenh Gas Con. 2013, 15, 150-162. 29. A. Lyngfelt, P. Markström, C. Linderholm, Chemical-Looping Combustion of Solid FuelsOperational Experiences in 100kW Dual Circulating Fluidized Bed System. Energ Procedia. 2013, 37, 608-617. 30. A. Abad, R. Pérez-Vega, L.F. de Diego, F. García-Labiano, P. Gayán, J. Adánez, Design and operation of a 50kWth Chemical Looping Combustion (CLC) unit for solid fuels. Appl Energ. 2015, 157, 295-303. 31. J. Adánez, A. Abad, R. Perez-Vega, L.F. de Diego, F. García-Labiano, P. Gayán., Design and Operation of a Coal-fired 50 kWth Chemical Looping Combustor. Energ Procedia. 2014, 63, 63-72.


29

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 30 of 32

32. R. Pérez-Vega, A. Abad, F. García-Labiano, P. Gayán, L.F. de Diego, J. Adánez, Coal combustion in a 50kWth Chemical Looping Combustion unit: Seeking operating conditions to maximize CO2 capture and combustion efficiency. Int J Greenh Gas Con. 2016, 50, 80-92. 33. J. Ströhle, M. Orth, B. Epple, Chemical looping combustion of hard coal in a 1MWth pilot plant using ilmenite as oxygen carrier. Appl Energ. 2015, 157, 288-294. 34. J. Ströhle, M. Orth, B. Epple, Design and operation of a 1MWth chemical looping plant. Appl Energ. 2014, 113, 1490-1495 35. H.R. Kim, D. Wang, L. Zeng, S. Bayham, A. Tong, E. Chung, M.V. Kathe, S. Luo, O. McGiveron, A. Wang, Z. Sun, D. Chen, L. Fan, Coal direct chemical looping combustion process: Design and operation of a 25-kWth sub-pilot unit. Fuel. 2013, 108, 370-384. 36. S.C. Bayham, H.R. Kim, D. Wang, A. Tong, L. Zeng, O. McGiveron, M.V. Kathe, E. Chung, W. Wang, A. Wang, A. Majumder, L. Fan, Iron-Based Coal Direct Chemical Looping Combustion Process: 200-h Continuous Operation of a 25-kWth Subpilot Unit. Energ Fuel. 2013, 27, 1347-1356. 37. L. Shen, J. Wu, Z. Gao, J. Xiao, Characterization of chemical looping combustion of coal in a 1kWth reactor with a nickel-based oxygen carrier. Combust Flame. 2010, 157, 934-942. 38. L. Shen, J. Wu, J. Xiao, Q. Song, R. Xiao, Chemical-Looping Combustion of Biomass in a 10 kWth Reactor with Iron Oxide as an Oxygen Carrier. Energ Fuel. 2009, 23, 2498-2505. 39. H. Gu, L. Shen, Z. Zhong, X. Niu, W. Liu, H. Ge, S. Jiang, L. Wang, Cement/CaOmodified iron ore as oxygen carrier for chemical looping combustion of coal. Appl Energ. 2015, 157, 314-322. 40. X. Niu, L. Shen, H. Gu, S. Jiang, J. Xiao, Characteristics of hematite and fly ash during chemical looping combustion of sewage sludge. Chem Eng J. 2015, 268, 236-244.


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Energy & Fuels

41. T. Song, J. Wu, H. Zhang, L. Shen, Characterization of an Australia hematite oxygen carrier in chemical looping combustion with coal. Int J Greenh Gas Con. 2012, 11, 326-336. 42. H. Ge, L. Shen, H. Gu, S. Jiang, Effect of co-precipitation and impregnation on Kdecorated Fe2O3/Al2O3 oxygen carrier in Chemical Looping Combustion of bituminous coal. Chem Eng J. 2015, 262, 1065-1076. 43. L. Shen, J. Wu, Z. Gao, J. Xiao, Reactivity deterioration of NiO/Al2O3 oxygen carrier for chemical looping combustion of coal in a 10kWth reactor. Combust Flame. 2009, 156, 13771385. 44. X. Wang, B. Jin, X. Zhu, H. Liu, Experimental Evaluation of a Novel 20 kW th in Situ Gasification Chemical Looping Combustion Unit with an Iron Ore as the Oxygen Carrier. Ind Eng Chem Res. 2016, 55, 11775-11784. 45. R. Xiao, L. Chen, C. Saha, S. Zhang, S. Bhattacharya, Pressurized chemical-looping combustion of coal using an iron ore as oxygen carrier in a pilot-scale unit,. Int J Greenh Gas Con. 2012, 10, 363-373. 46. J. Ma, H. Zhao, X. Tian, Y. Wei, S. Rajendran, Y. Zhang, S. Bhattacharya, C. Zheng, Chemical looping combustion of coal in a 5kWth interconnected fluidized bed reactor using hematite as oxygen carrier. Appl Energ. 2015, 157, 304-313. 47. C. Linderholm, M. Schmitz, P. Knutsson, A. Lyngfelt, Chemical-looping combustion in a 100-kW unit using a mixture of ilmenite and manganese ore as oxygen carrier. Fuel. 2016, 166, 533-542. 48. C. Linderholm, M. Schmitz, 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, 1029-1039.


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49. F. Scala, Fluidized bed technologies for near-zero emission combustion and gasification, Elsevier, 2013. 50. A. Cabello, P. Gayán, F. García-Labiano, L.F. de Diego, A. Abad, J. Adánez, On the attrition evaluation of oxygen carriers in Chemical Looping Combustion. Fuel Process Technol. 2016, 148, 188-197. 51. A. Lyngfelt, Oxygen carriers for chemical-looping combustion, Calcium and Chemical Looping Technology for Power Generation and Carbon Dioxide (CO2) Capture, 2015, 221-254.


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Test Operation of a Separated-Gasification Chemical Looping

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