The Absorption Breakthrough Characteristics of Hydrogen Chloride

Feb 2, 2016 - Hydrogen Chloride Removal from Flue Gas by Low-Temperature Reaction with Calcium Hydroxide. Alessandro Dal Pozzo , Raffaela Moricone , G...
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The Absorption Breakthrough Characteristics of Hydrogen Chloride Gas Mixture on Potassium-Based Solid Sorbent at High Temperature and High Pressure Jae-Young Kim,† Young Cheol Park,† Sung-Ho Jo,† Ho-Jung Ryu,† Jeom-In Baek,‡ and Jong-Ho Moon*,† †

Low Carbon Process Research Laboratory, Korea Institute of Energy Research, 152 Gajeong-ro, Yuseong-gu, Daejeon 34129, Korea KEPCO Research Institute, 103-16 Munji-dong, Yuseong-gu, Daejeon 305-380, Korea

‡

ABSTRACT: In this study, the hydrogen chloride gas mixture absorption breakthrough behaviors of potassium (K)-based solid sorbents (K2CO3/Al2O3, KEPCO-RI, Korea) were studied with varying inlet HCl concentration (175−700 ppmv), temperature (200−500 °C), and pressure (1−20 bar) in a fixed-bed reactor (15 cm tall bed with 0.5 cm i.d.). The sorption capacity increases with increasing temperature and increasing pressure, whereas it was not affected by the inlet concentration. KCl crystals are formed on the sorbent surface when K+ ions from the K2CO3/Al2O3 sorbent are reacted with the Cl− ion from HCl. Its optical, physical, and chemical characterizations were examined by SEM, EDAX, BET, TGA, and XRD before and after the breakthrough tests. The main purpose of this study is to provide basic information of HCl sorption characteristics on K2CO3/Al2O3 solid sorbents for developing a high temperature and high pressure halogenide halide removal process.

1. INTRODUCTION Recently, the integrated gasification combined cycle (IGCC) process has received big interest because of better thermal efficiency than the conventional pulverized coal firing (PC) process. However, their product, coal derived synthesis gas, contains several kinds of acid gases with strong toxicity. Among them, the most toxic, corrosive, and dangerous contaminant is hydrogen chloride (HCl). In general, the concentration of halogenide halide including HCl is about 50−700 ppmv in the coal derived synthesis gas. In order to introduce synthesis gas to the IGCC process, the HCl concentration should be controlled under 1 ppmv. If the synthesis gas with high HCl concentration remains in the process for a long time, it can cause serious damage, such as gas turbine or pipe corrosion. In order to increase the thermal efficiency of the whole IGCC process, the adequate working temperature for HCl removal is in the range of 300−500 °C. Moreover, in newly developed coal combustion systems, such as oxy combustion,1 MILD (moderate or intense low oxygen dilution) combustion,2−4 oxy-CFBC (circulating fluidized-bed combustor),5,6 and coal CLC (chemical looping combustion),7,8 the high temperature HCl removal technology is also important because long-term exposure to HCl can lead to severe corrosion of equipment, pipe lines, catalysts, and bed materials. Among various kinds of HCl removal technologies, the hot gas cleanup process using fixed beds or fluidized beds are most suitable in view points of working temperature and pressure. For fixed-bed and fluidized-bed operations, appropriate solid sorbents should be developed. They should have high HCl sorption capacity and, at the same time, endure high temperature, high pressure, and particle attrition. Typical solid sorbents for HCl removal are activated carbonmetal oxides and activated alumina-metal oxides. They are made by impregnating the oxide form of alkali metals and alkaline earth metals onto active carbon supports or active alumina supports. Alkali metal or alkaline earth metal oxides, © 2016 American Chemical Society

such as CaO, MgO, and K2O, form metal halide (metal chloride) by reacting with HCl gas at high temperature and high pressure conditions. Once metal chloride is formed on the sorbent surface, it is very difficult to regenerate it back to its original oxide form. Therefore, it is necessary to develop an appropriate dry sorbent that is inexpensive to produce or reusable or easily disposable. Duo et al. found that the HCl sorption capacity of a CaCO3 is comparatively low at 400 °C, and HCl sorption capacity of Na2CO3 is larger at 400−500 °C than at 300 or 600 °C.9 Verdone and Filippis showed that Na2CO3 has the highest HCl sorption capacity at 400−500 °C.10 Dou et al. removed HCl to less than 1 ppmv using a solid particle that includes based on Na−-, Ca−-, and Mg−-based compounds in a fixed-bed reactor at 550 °C.11,12 Chen et al. developed solid particles synthesized by adding NaOH solution to CaO and CaCO3.13 Mura and Lallai,14 Chyang et al.,15 Coda et al.,16 Weinell et al.,17 and Partanen et al.18 studied HCl sorption behaviors by CaO and CaCO3 solid sorbents at high temperature over 500 °C. Li et al. also evaluated HCl sorption performance by using various solid particles, of which their main substances are meerschaum, Ca(OH)2, Na2CO3, and NaHCO3.19 The optimum working temperature was 550 °C, and the HCl sorption mechanism was governed by the chemical reaction rather than by the diffusion. In order to develop inexpensive solid sorbents, Krishnan et al. suggested nahcolite, a natural carbonate mineral that is converted to Na2CO3 at temperatures higher than 150 °C.20 Dou et al. carried out a sorption breakthrough test at 550 °C using a solid particle in a pelletized form, with a main substance of montmorillonite (30−70 wt %), a natural mineral, and MgO.21 Ohtsuka et al. performed a breakthrough test using a Received: October 20, 2015 Revised: January 31, 2016 Published: February 2, 2016 2268

DOI: 10.1021/acs.energyfuels.5b02473 Energy Fuels 2016, 30, 2268−2275

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Energy & Fuels

Figure 1. Schematic diagram of a fixed-bed reactor.

2. EXPERIMENTAL SECTION

solid particle with main substances of NaAlO2 and Na2CO3 by using simulated synthesis gas in a fixed-bed reactor at 400 °C.22 As mentioned above, carbonate-based HCl sorbents, such as Na2CO3, NaHCO3, CaCO3, and K2CO3, have been focused on due to their strong affinity to chloride. Among them, K2CO3 is the strongest active component for HCl sorption at the range of hot syngas cleaning up process. However, related researches are hardly found so far. The reaction path is as follows: K2CO3 + 2HCl → 2KCl + CO2 + H2O. Kim et al. carried out a HCl breakthrough test using a K2CO3 impregnated dry sorbent, and it was confirmed that the optimum sorption property was at the highest pressure and temperature conditions (20 bar and 400 °C).23 Kim et al. also reported HCl breakthrough behaviors of zeolite 13X pellet at low temperature condition.24 Most recently, Baek et al. carried out HCl removal experiments using K-based sorbent.25 In a fixed-bed reactor system, HCl concentration decreased from 150 to 900 ppmv to under 5 ppmv. The saturated chloride sorption capacity was over 15 wt % at 20 bar and 300−500 °C. Furthermore, in a bubbling fluidized-bed reactor system, HCl concentration decreased from 130 to 390 ppmv to under 1 ppmv. They confirmed that those K-based sorbents are feasible for applying to the HCl removal process. In this study, the hydrogen chloride sorption characteristics of K-based dry sorbents (K2CO3/Al2O3, KEPCO-RI, Korea) were studied in a fixed-bed reactor. Breakthrough tests were carried out with varying experimental conditions such as inlet HCl concentration, reaction temperature, and reaction pressure. Before and after the breakthrough tests, optical, physical, and chemical characteristics of K2CO3/Al2O3 sorbents were analyzed by BET, SEM-EDAX, XRD, and TGA.

2.1. Preparation of K-Based Sorbent (K2CO3/Al2O3). Potassium-based solid sorbents, K2CO3/Al2O3 powder, were supplied from KEPCO Research Institute (KEPCO-RI). They were synthesized by a spray drying method that can produce a large quantity of sorbent with uniform property. Those sorbents consist of active materials, support, and inorganic binders. The active material was K2CO3, and its initial content in the raw materials was 40 wt %. The major component of the raw support material was γ-Al2O3. The above materials were well mixed in pure water with adding organic additives such as dispersant, defoamer, and organic binder. The mixed slurry was comminuted with a ball mill to make a homogeneous colloidal slurry and was sprayed to form spherical particles. They were calcined at 550−750 °C in a muffle oven for 3 h under atmospheric condition after predrying at 120 °C overnight. The organic additives were burned out during the calcination. More detailed preparation of sorbents was described in Baek’s previous paper.25 2.2. Physical Properties of K-Based Sorbent (K2CO3/Al2O3). Bulk densities were measured 7 times, and the average value of 5 measurements was adapted after excluding the maximum and the minimum values. In order to find changes in surface area, pore volume, and average pore size of the sorbent before and after the breakthrough experiments, a surface area analyzer (BET, ASAP 2420, Micromeritics Instrument Co., USA) was used. A thermogravimetric analyzer (TGA, SDT Q-600, TA Instruments Co., USA) was used to find the weight changes and regeneration temperature range of the sorbent. The weight loss of the sorbent was measured with increasing temperature from 25 to 600 °C (5 °C/min) at the N2 condition. To find the change in the sorbent surface before and after the breakthrough experiments, a cold type field emission scanning electron microscope (SEM, SEM-4800, HITACHI Ltd., Japan) was used. Changes in the composing substances of the sorbents before and after the experiments were observed by energy-dispersive X-ray spectroscopy (EDAX, X-max, HORIBA Ltd., Japan). To identify the change of crystal structure of the sorbent after the HCl sorption, the X-ray diffractometer (XRD, D-max 2500PC, Rigaku Co., Japan) was used. 2269

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Energy & Fuels Table 1. Summary of Experimental Conditions item

run no.

flow rate (NL/min)

HCl conc. (ppmv)

temp. (°C)

pressure (bar)

effect of concentration

1 2 3 4a 5 6 7a 8 9 10 11 12 13a

0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5

175 350 525 700 700 700 700 700 700 700 700 700 700

400 400 400 400 200 300 400 500 400 400 400 400 400

20 20 20 20 20 20 20 20 1 5 10 15 20

effect of temperature

effect of pressure

a

Base case (reference conditions).

2.3. Fixed-Bed Reactor. The equipment drawing of the fixed-bed reactor used in the test is shown in Figure 1. The equipment is divided into 3 parts: the gas feeding part, reaction part, and analysis part. Three MFCs (mass flow controller, 5850E, Brooks instrument Co., USA) with 99.0% accuracy were installed on the feeding part to control the concentration of reaction gas (HCl) and inlet flow rate. Diluted HCl (1000 ppmv) with balanced pure N2 (99.99+%) gas was introduced into the reactor. Reaction gas was injected in the up-flow direction from the bottom of the reactor. A fixed-bed reactor with an inner diameter of 0.5 cm and height of 15 cm was installed vertically in the electric heater of the reaction part. In order to prevent the partial cooling that occurs when cold gas flows into the lower part of the reactor, a preheater was installed at the front of the reactor to minimize the temperature difference. The temperature inside the reactor was adjusted using the temperature controllers (UT35A, Yokogawa Electric Corp., Japan). K-type thermocouples were installed on the top, middle, and bottom parts of the reactor to measure the inside temperature. The reactor pressure was adjusted by installing a back pressure regulator (BPR, TESCOM Co., Ltd., USA) onto the outlet of the reactor. Electric pressure transmitters (SIEMENS AG., Germany) with 99.935% accuracy were installed in order to observe the pressure at the inlet and the outlet of the reactor. On the analysis part, a real-time FT-IR (Fourier transform infrared) gas analyzer (DX4000, Gasmet Technologies Inc., Finland) with sub-ppmv level accuracy was installed to measure the outlet gas concentration during the reaction. 2.4. Experimental Conditions and Methods. In order to evaluate the HCl sorption characteristics of the K-based sorbent, breakthrough tests were carried out using a fixed-bed reactor with varying inlet gas (HCl) concentration (175, 350, 525, 700 ppmv), reaction temperature (200, 300, 400, 500 °C), and reaction pressure (1, 5, 10, 15, 20 bar). Detailed experimental conditions are summarized in Table 1. Before every test, the adsorbent was degassed (regenerated) for 8 h at 300 °C and vacuum condition. As packing materials for a fixed-bed reactor, a powder-type solid sorbent (K2CO3/Al2O3) and quartz sand (SiO2) were used. They were loaded in the weight ratio of 1 to 9 with considering their bulk densities. Glass wools were inserted between the sorbent layer and the quartz sand layer to prevent solid mixing. Weights of K-based sorbent and quartz sand were 0.428 and 3.74 g, respectively. After loading sorbents onto the bed, temperature and pressure were slowly increased up to the setting values while flowing N2 single gas. Then, the reaction gas (HCl + N2) was introduced, and the breakthrough test was carried out until the sorbent became saturated. Outlet gas concentration was measured using an FT-IR gas analyzer. The outlet gas after the test was released after being neutralized with a 0.1 N sodium hydroxide solution. Its optical, physical, and chemical characterizations were evaluated by SEM, EDAX, BET, TGA, and XRD to compare before and after the breakthrough tests. Fresh state

sorbents were loaded into the bed at every experiment for fair comparison.

3. RESULTS AND DISCUSSION In this study, the HCl sorption characteristics of K-based sorbents were examined by the breakthrough tests. When coal derived synthesis gas was used as a raw material for Fischer− Tropsh reactions, gas turbines, and fuel cells, the desired HCl concentration is less than 1 ppmv. Thus, the breakthrough time was determined when the HCl concentration exceeded 1 ppmv. The saturation time was determined when the HCl concentration reached to the prereaction level (over 99%). 3.1. HCl Sorption Characteristics of a K-Based Sorbent. Breakthrough experiments were carried out to examine the characteristics of HCl sorption by a K-based sorbent (K2CO3/Al2O3) under the various conditions (at different inlet HCl concentrations, temperatures, and pressures). As the reference experimental conditions, the inlet flow rate, the inlet HCl concentration, the reaction temperature, and the reaction pressure were 0.5 NL/min, 700 ppmv, 400 °C, and 20 bar, respectively. Figure 2 shows the breakthrough curves according to (a) the changes of inlet HCl concentration, (b) the changes of reaction temperature, and (c) the changes of reaction pressure. The HCl concentration changes after the reaction were normalized and expressed as C/Co, where Co and C represent the inlet HCl concentration and the outlet HCl concentration exhausted at a given time, respectively. The exhausted concentration of the HCl gas mixture introduced at the concentration of 175−700 ppmv was maintained under 1 ppmv over a certain period of time (breakthrough time). After the breakthrough time, the HCl concentration was sharply increased. The saturation time was determined when the HCl concentration reached the prereaction level (over 99% of feed concentration). Figure 2a shows that the breakthrough time and saturation time were shortened as HCl concentration was increased. On the other hand, the breakthrough time became longer as reaction temperature (b) and reaction pressure (c) were increased. Moreover, the breakthrough curve became steeper as the reaction temperature and reaction pressure were increased. Figure 3 shows the breakthrough time and saturation time according to (a) the changes of HCl concentration, (b) the changes of reaction temperature, and (c) the changes of reaction pressure. As it is shown in Figures 2a and 3a, the breakthrough times were reduced down to 791, 356, 209, and 2270

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Figure 3. Breakthrough time and the saturation time of K2CO3/Al2O3 sorbent at different operating conditions: (a) inlet concentration (0.5 NL/min, 400 °C, 20 bar), (b) reaction temperature (0.5 NL/min, 700 ppmv, 20 bar), (c) reaction pressure (0.5 NL/min, 700 ppmv, 400 °C). * Base case (0.5 NL/min, 700 ppmv, 400 °C, 20 bar).

Figure 2. HCl breakthrough curves of K2CO3/Al2O3 sorbents at different operating conditions: (a) inlet concentration (0.5 NL/min, 400 °C, 20 bar), (b) reaction temperature (0.5 NL/min, 700 ppmv, 20 bar), (c) reaction pressure (0.5 NL/min, 700 ppmv, 400 °C). * Base case (0.5 NL/min, 700 ppmv, 400 °C, 20 bar).

Figure 4 shows the sorption capacity of the sorbent (K2CO3/ Al2O3) according to (a) the changes of HCl concentration, (b) the changes of reaction temperature, and (c) the changes of reaction pressure. As can be seen in Figure 4a, although HCl concentration was increased, the sorption capacities of the sorbent (K2CO3/Al2O3) were almost the same, about 7.98− 8.30 mmol/g. This means that HCl concentration has little impact on the sorption capacity, whereas the breakthrough time became much longer at the lower inlet HCl concentration, as shown in Figure 3a. As can be seen in Figure 4b,c, the sorption capacity of the sorbent (K2CO3/Al2O3) was increased as the reaction temperature and the reaction pressure were increased. As temperature and pressure increases, the movement of HCl molecules in the bed becomes more active. Since both external and internal diffusion rates into the K2CO3 particles become faster, the breakthrough time becomes longer and the saturation time becomes shorter (Figure 3b,c). For the same reasons, as can be seen in Figure 2b,c, when temperature and

161 min and the saturation times were also shortened to 1,296, 840, 696, and 648 min as the inlet HCl concentration was increased to 175, 350, 525, and 700 ppmv. According to Figures 2b and 3b, the breakthrough times were increased to 50, 105, 161, and 164 min and the saturation times were decreased to 756, 720, 648, and 624 min as the reaction temperatures were increased to 200, 300, 400, and 500 °C. Figures 2c and 3c demonstrate that the breakthrough times were increased to 93, 112, 122, 131, and 161 min and the saturation times were decreased to 804, 786, 750, 708, and 648 min as the reaction pressures were increased to 1, 5, 10, 15, and 20 bar. The results imply that the breakthrough time becomes longer and the saturation time is shortened as the reaction temperature and the reaction pressure are increased. The results imply that HCl removal becomes more efficient at higher temperature and higher pressure conditions. 2271

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affecting the reactivity of the sorbent. Therefore, the property analysis was performed to compare the characteristics of the sorbent before and after the breakthrough experiments at each temperature and pressure condition. The optical, physical, and chemical characteristics of the sorbents were examined by TGA, SEM, EDAX, and XRD. Table 2 shows the physical properties of the fresh sorbent (K2CO3/Al2O3) and quartz sand. Table 2. Physical Properties of K-Based Sorbent and Quartz Sand shape average particle size (μm) bulk density (kg/m3) surface area (m2/g) pore volume (cm3/g) average pore diameter (Å)

sorbent

quarts-sand

powder 120 1.174 4.836 0.022 179

powder 332 1.453 0.299 0.001 110

Figure 5 represents TGA results showing the weight changes of fresh and used sorbents according to the temperature. As it is

Figure 5. Weight changes of K2CO3/Al2O3 sorbents (fresh and used sorbents). Used: after reaction under reference conditions (0.5 NL/ min, 700 ppmv, 400 °C, 20 bar).

Figure 4. Sorption capacity of HCl on K2CO3/Al2O3 sorbent under different operating conditions: (a) inlet concentration (0.5 NL/min, 400 °C, 20 bar), (b) reaction temperature (0.5 NL/min, 700 ppmv, 20 bar), (c) reaction pressure (0.5 NL/min, 700 ppmv, 400 °C). * Base case (0.5 NL/min, 700 ppmv, 400 °C, 20 bar).

demonstrated, there is no significant difference in the weight before the reaction and after the reaction up to 770 °C. The weight of the used sorbent is significantly reduced at the temperature above 770 °C (melting point of KCl). It is thought that thermal deformation of KCl induced the weight reduction over 770 °C. However, the weight reduction of fresh sorbent is much smaller than that of used sorbent at the temperature range between 770 and 891 °C (melting point of K2CO3). Figure 6 represents the SEM analysis results showing the surface images of the sorbent (K2CO3/Al2O3) before and after the reaction at different conditions and magnifications. At high temperature and low pressure condition ((b) 400 °C, 1 bar), though the KCl presumed crystals were formed on the sorbent surface, the microshape was very similar to that of fresh sorbent. However, at high temperature and high pressure conditions ((c) 400 °C, 20 bar; (d) 500 °C, 20 bar), since a large amount of KCl crystals were formed and covered on the surface, surface shapes were quite different from those of fresh sorbents. As shown in Figure 4b,c, at high temperature and high pressure, the HCl sorption capacity K2CO3/Al2O3 became

pressure were increased, the breakthrough curve became steeper. This involves that the sorption capacity, the breakthrough time, and the saturation time of the sorbent (K2CO3/Al2O3) improves at a higher temperature and a higher pressure. In this study, it showed the best performance at 500 °C and 20 bar. That working condition is within the ranges of temperature (400−500 °C) and pressure (30 bar) for hot gas cleanup, such as a desulfurization reaction, in the precombustion process. This also means that the application of a high temperature and high pressure HCl removal process for the precombustion CO2 capture process is feasible. 3.2. Property Analysis of Absorbent before and after the Reaction. In the above section, HCl sorption breakthrough behaviors of K-based dry sorbents (K2CO3/Al2O3) were evaluated. The breakthrough experimental results revealed that temperature and pressure are important influential factors 2272

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Figure 6. SEM images of K2CO3/Al2O3 sorbents under different operating conditions: (a) fresh sorbent, (b) reaction pressure (0.5 NL/min, 700 ppmv, 400 °C, 1 bar), (c) reference (0.5 NL/min, 700 ppmv, 400 °C, 20 bar), (d) reaction temperature (0.5 NL/min, 700 ppmv, 500 °C, 20 bar) * Base case (0.5 NL/min, 700 ppmv, 400 °C, 20 bar).

Table 3. EDAX Analysis of K2CO3/Al2O3 Sorbents (at 20 bar) (Unit: wt %) fresh sorbent 200 °C 300 °C 400 °Ca 500 °C a

O

Al

Si

K

Cl

other elements

47.49 42.84 30.01 28.93 33.19

10.28 12.84 10.74 8.84 8.07

3.39 4.70 3.77 2.85 3.21

28.56 16.94 25.45 27.68 21.11

10.14 18.07 21.83 23.38

9.98 12.28 11.97 9.87 11.03

Base case (reference conditions).

4. SUMMARY AND CONCLUSION This study examined the characteristics of HCl sorption by a Kbased sorbent (K2CO3/Al2O3) at various inlet HCl concentrations, temperatures, and pressures. The breakthrough characteristics, such as sorption capacity, breakthrough time, and saturation time, were investigated using a fixed-bed reactor. Property analysis of the sorbents before the reaction and after the reaction was performed by TGA, SEM, EDAX, and XRD analysis. (1) The HCl gas mixture introduced at the concentration of 175−700 ppmv was maintained under 1 ppmv for a certain period of time after the reaction with the K-based sorbent. Afterward, HCl concentration was rapidly increased and the K2CO3/Al2O3 sorbent in the sorption bed was saturated with HCl. (2) Although the breakthrough time and the saturation time became shorter as the inlet HCl concentration was increased, the sorption capacities of HCl at every inlet concentration were almost the same. This implies that the inlet HCl concentration has little impact on the sorption capacity of K2CO3/Al2O3 sorbent. (3) The breakthrough time and the HCl sorption capacity were increased as the reaction temperature and reaction pressure were increased. This means that the sorption capacity of K-based sorbents improves at a higher

larger and the amount of KCl formation also became larger. Therefore, the surface became coarser after the reaction, especially at high temperature and high pressure experimental conditions, comparing to that before the reaction. The surface elements of the sorbent (K2CO3/Al2O3) according to the reaction temperature analyzed by EDAX are shown in Table 3. Cl (chloride) was not found from the surface before the reaction, whereas, after the reaction, it was detected with the maximum percentage of 23.38%. In addition, the Cl content increased as the reaction temperature increased. Figure 7 represents the XRD results showing the crystalline structures of the sorbent (K2CO3/ Al2O3) according to the reaction temperature and system pressure. The major components of the sorbent (K2CO3/Al2O3) before the reaction (a) and after the reaction (b, c) were K2CO3 and KCl, respectively. There is a change in the crystalline structure of the sorbent (K2CO3/Al2O3) after the reaction (b, c), comparing to that before the reaction (a). The major component of the sorbent, K2CO3, is reacted with HCl, transforming KCl. Moreover, the KCl intensities were increased as the reaction temperature (b) and the reaction pressure (c) were increased. Those results coincided with the EDAX results in Table 3 and the results of breakthrough tests in Figure 4b,c. The sorption capacity of the sorbent (K2CO3/Al2O3) was increased as the reaction temperature and the reaction pressure were increased. 2273

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Figure 7. X-ray diffractogram of K2CO3/Al2O3 sorbents under different operating conditions: (a) fresh sorbent, (b) reaction temperature (0.5 NL/min, 700 ppmv, 20 bar), (c) reaction pressure (0.5 NL/min, 700 ppmv, 400 °C) * Base case (0.5 NL/min, 700 ppmv, 400 °C, 20 bar).

temperature and a higher pressure so that the application of the HCl removal process for the precombustion CO2 capture process at a high temperature and a high pressure becomes easier. (4) XRD and SEM-EDAX analysis results showed that KCl is formed when K+ ions of the K2CO3/Al2O3 sorbent is reacted with the Cl− ion of HCl. The sorption capacity of KCl was increased as the reaction temperature and the reaction pressure were increased.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Phone: +82 42-860-3696. Fax: +82 42-860-3134. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was financially supported by the Energy Efficiency & Resources Programs (No. 201120102004B and No. 20152010201840) of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by the Korea Government Ministry of Trade, Industry & Energy (MOTIE).

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DOI: 10.1021/acs.energyfuels.5b02473 Energy Fuels 2016, 30, 2268−2275