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Hydrate-based CO2 capture from IGCC syngas with TBAB and nano Al2O3 Ze-Yu Li, Zhi-Ming Xia, Xiao-Sen Li, Zhao-Yang Chen, Jing Cai, Gang Li, and Tao Lv Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.7b03605 • Publication Date (Web): 09 Jan 2018 Downloaded from http://pubs.acs.org on January 13, 2018
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Energy & Fuels
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Hydrate-based CO2 capture from IGCC syngas with TBAB and nano
2
Al2O3
3 4 5 6 7 8 9 10 11 12 13 14 15 16
Ze-Yu Lia,b,c,d,e, Zhi-Ming Xiaa,b,c,d, Xiao-Sen Lia,b,c,d*, Zhao-Yang Chena,b,c,d, Jing Caia,b,c,d, Gang Lia,b,c,d, Tao Lva,b,c,d a
Guangzhou institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou, 510640,
People’s Republic of China b
CAS Key laboratory of gas hydrate, Guangzhou, 510640, People’s Republic of China
c
Guangdong Provincial Key laboratory of New and Renewable Energy Research and Development,
Guangzhou, 510640, People’s Republic of China d
Guangzhou Center for Gas Hydrate Research, Chinese Academy of Sciences, Guangzhou, 510640,
People’s Republic of China e
University of Science and Technology of China, Nano Science and Technology Institute, Suzhou
215123, People’s Republic of China
17
ABSTRACT: Hydrate-based CO2 capture and/or H2 purification from IGCC syngas has been
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more and more attractive technology in both environmental and clean energy fields. This
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work focused on both microcosmic and macroscopic studies for the CO2/H2 hydrate formation
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process with synergic additives comprised Tetra-n-butyl Ammonium Bromide (TBAB) and
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nano Al2O3. The experiments were carried out with 0.5 wt % nano Al2O3 and 1, 5, 10 and 11
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wt % TBAB, respectively. The microcosmic study shows that, with the synergic additives, the
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CO2/H2 mixture hydrate formed mainly on the nano Al2O3 surface and formed semiclathrate
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structure. Additionally, the macroscopic study shows that the synergic additives could
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remarkably promote the gas uptake and separation efficiency. Noteworthy, compared with
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unitary TBAB, THF and CP, the synergic additives could increase the gas uptake for the
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CO2/H2 hydrate formation process by approximate 43.62%, 230.56% and 173.27%,
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*
29
E-mail:
[email protected].
To whom correspondence should be addressed: Telephone: +86 20 87057037. Fax: +86 20 87057037.
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respectively. The experimental results indicate that the synergic effect of TBAB and nano
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Al2O3 is helpful for hydrate-based CO2 capture from IGCC syngas.
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1. INTRODUCTION
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Global warming resulted by the increasing emission of greenhouse gas is widely
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considered to be the urgent problem in the 21st century.
1
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cycle (IGCC), as one of new clean energy technologies, has prominent contribution on
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retarding the climate change. The essential of this approach, in fact, is that the CO2 capture
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from CO2/H2 mixture gas. Removal of CO2 from mixture gas can be achieved by a serious of
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technologies such as physical absorption, chemical adsorption, membranes, cryogenic
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distillation, and so on. 2-5 However, these methods have the individual issues of large energy
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consumption, apparatus corrosion, easily caused second pollution or low capacity, and so
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forth. Hence, it is necessary to develop a cost-effective and environment-friendly
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capture/separation technology for CO2 capture and separation.
Integrated gasification combined
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Hydrate-based CO2 capture from IGCC is one of the new technologies which based on gas
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hydrate formation process to capture CO2 and purify H2. Gas hydrates are nonstoichiometric
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compounds existing in lattice structures which are made up by host molecules and guest
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molecules.
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component between hydrate phase and gaseous phase. For instance, the hydrate formation
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pressure of H2 is 300 MPa while that of CO2 is 2.91 MPa at 280 K. 7 Spencer et al. 8 made an
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economic assessment, and reported that the cost for capturing CO2 from CO2/H2 syngas by the
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hydrate methods is about 10 dollars per ton CO2, which is pretty cost-effective.
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6
The basis for the hydrate-based CO2 capture is the selective partition of CO2
However, for industrial utilization, hydrate-based CO2 capture still need further study to 2
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enhance the gas storage and to accelerate the gas hydrate formation rate. 9, 10 In order to lower
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the hydrate formation pressure and improve the hydrate formation rate, some additives such
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as TBAB, 11-13 THF (Tetrahydrofuran), 14-16 and CP (Cyclopentane) etc. 17-19 were proposed to
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enhance the gas hydrate formation process. Kamata et al.
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semiclathrate hydrate with water molecules, and it was suitable for small guest gas molecules
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separation. Li et al.
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pure system of TBAB, the experimental results indicated that it has better gas storage and
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separation efficiency for TBAB system than pure water system. Duc et al.
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0.29 mol % TBAB was the optimum concentration for reducing CO2 composition from
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CO2/N2 mixture. What else, THF hydrates have pretty well cavity structure which are suitable
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for guest gas molecules storage. Lee et al.
22
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concentration
from
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non-environmental-protection chemical and easily cause environment pollution. As for the
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study on CP by Zhang et al. 23, they found that the hydrate formation and dissociation could
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significantly enrich CO2 from 40 to 98 mol % at 282 K for pure CP system. Furthermore, Li
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et al.
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capture from IGCC syngas with 5 vol% CP is 3 mmol gas/mol.
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24
11
for
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reported the TBAB could form
studied on hydrate-based CO2 separation from CO2/H2 syngas in the
the
CO2
capture
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presented that
reported that 1 mol %THF was the optimum CO2/H2
syngas.
Whereas,
THF
is
reported that, at 4.5 MPa and 273.15 K, the gas uptake for the hydrate-based CO2
However, besides the above additives, heat and mass transfer is demonstrated to be the 25-27
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most difficult and significant for the gas hydrate formation process.
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researchers proposed the idea that using nano fluid to enhance the heat and mass transfer
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processes. Park et al.
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the gas uptake of methane hydrate by 300 %. And then the effect of the MWCNTs was
28
Recently, some
reported that the muti-carbon nanotubes (MWCNTs) could increase
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compared with the oxide muti-walled carbon nanotubes (OWMCNTs) on the methane hydrate
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formation process in terms of gas uptake, they found that the OMCNTs had a better
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performance in gas uptake. 29 Kakati et al. 30 used the nano Al2O3 and Sodium dodecyl sulfate
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(SDS) to enhance the CH4 gas hydrate formation process, and demonstrated that the gas
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uptake of 0.8 wt % nano Al2O3 and 0.03 wt % SDS was 2.5 times more than that of pure water.
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Choi et al. 31 found that the gas uptake of the 0.2 wt % nano Al2O3 and 0.6 wt % SDS system
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was 3.74 times higher than that of 10 wt % THF system, they explained that the nano Al2O3
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promoted the solution system thermal conductivity, while SDS reduced the surface tension of
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CO2 and water molecules. Indeed, the research for hydrate-based CO2 capture from IGCC
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syngas with nano fluid is still faultiness, and need further study. As a porous medium, nano
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Al2O3 has pretty performance on heat and mass transfer feature. Also, as a well-known
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thermodynamic promoter, TBAB could relieve the gas hydrate formation condition. Therefore,
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this work focused on the kinetic, separation efficiency and microcosmic study for CO2
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removal from CO2/H2 syngas with TBAB and nano Al2O3.
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2. EXPERIMENTAL SECTION
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2.1. Material. Table 1 summarizes all the materials for this work. In pre-combustion IGCC
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power station, the treated syngas mainly consists 60 mol % H2. Hence, the 40 mol % CO2 and
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60 mol % H2 mixture gas was simulated as the syngas in this work. The de-ionized water was
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prepared in the laboratory by DZG-303A, EPED. What else, all the chemicals including
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TBAB and nano Al2O3 were provided directly by purchasing without further treatment.
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The particle size distributions of the nano Al2O3 were measured by the Mastersizer 2000
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particle size analyzer (Malvern Instruments. Ltd., Britain). As shown in Figure 1, the average 4
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particle size of the nano Al2O3 sample is about 550 nm, which could mix with water and form
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homogeneous colloidal dispersion in relatively lower concentration (99.99
BEST-REAGENT,CHENGDU
Nano Al2O3
200-600 nm
XFNANO,NANJING
624
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625 626 627 628 629 630 631 632 633
Table 2. Summary of the experimental conditions and results Texpa
Pexpb
RTc
Pfinald
CCRe
CCHf
S.Fr.g
(K)
（MPa）
(min)
(MPa)
(%)
（%）
(%)
0.1 wt % Nano Al2O3
279.65
3.00
49
2.62
-
-
-
2
0.5 wt % Nano Al2O3
279.65
3.00
105
2.46
-
-
-
3
0.8 wt % Nano Al2O3
279.65
3.00
220
2.44
-
-
-
281.25
3.08
122
2.61
28.65
78.71
39.86
281.25
3.09
120
2.56
26.62
88.97
45.49
281.25
3.07
123
2.23
27.38
80.22
50.31
281.25
3.00
125
2.37
25.01
81.97
55.71
Exp. No.
System
1
4 5 6 7
634 635 636
a.
0.5 wt % Nano Al2O3+1wt%TBAB 0.5 wt % Nano Al2O3+ 5 wt %TBAB 0.5 wt % Nano Al2O3+10 wt %TBAB 0.5 wt % Nano Al2O3+11 wt %TBAB
Experimental temperature;
reaction completed;
e.
b.
Original pressure;
c.
Reaction time; (tconstant-t0); f.
d.
Final pressure when
CO2 composition in the Residual gas; CO2 composition in the hydrate phase; g.
Split fraction.
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