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Experimental research on desorption of ammonia decarbonization solution coupled sound wave
International Journal of Greenhouse Gas Control 52 (2016) 231–236
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International Journal of Greenhouse Gas Control journal homepage: www.elsevier.com/locate/ijggc
Experimental research on desorption of ammonia decarbonization solution coupled sound wave Ma Shuangchen ∗ , Chen Gongda, Gao Ran, Zhu Sijie, Weng Xiaoyu, Jiao Kunling School of Environment, North China Electric Power University, Baoding 071003, China
a r t i c l e
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Article history: Received 25 April 2016 Received in revised form 30 June 2016 Accepted 11 July 2016 Available online 19 July 2016 Keywords: Decarbonization Ammonia solution Desorption Sound wave
a b s t r a c t Currently, regeneration of decarbonization liquid and separation of pure CO2 have been realized by heating ammonia decarbonization solution. However, elevated temperature will lead to significant ammonia escape and energy consumption with traditional desorption method. Given the role of sound in degassing, sound wave was used to desorb decarbonization solution in this research. On self-designed experimental equipment, desorption of decarbonization liquid was studied coupled sound wave. To discuss multi-factor influences on sound wave desorption, basic characteristics of sound wave for desorption under different temperatures and concentrations were revealed. In the experiment, under 16 W sound wave, the desorption rate of NH4 HCO3 solution increased from 9.8% to 13.76% at 50 ◦ C, compared with no sound wave condition; while at 70 ◦ C, the desorption rate raised from 25.4% to 30.51%. By adding sound wave, the increment of desorbed CO2 was higher than that of escaped ammonia. The possibility of applying sound wave to desorption process in ammonia decarbonization was discussed, and a method of accelerating desorption was provided in the paper. © 2016 Elsevier Ltd. All rights reserved.
1. Introduction In recent years, excessive emissions of CO2 and other greenhouse gases that cause climate change have become a worldwide environmental problem (Han et al., 2013; Liang et al., 2016a,b; Luo et al., 2015; Macfarlane and Scott, 2012; Mondal et al., 2012). CO2 mainly comes from fossil fuels burning, especially the combustion in power plants. Therefore CO2 emission reduction in power plants is crucial to curb global climate anomalies (Davison, 2007; Lei et al., 2013; Ma et al., 2013). Among many carbon abatement methods, ammonia solution was regarded as a feasible absorbent for its low cost, high absorption efficiency and low corrosion (An and Bai, 1999; And and An, 1997; Liang et al., 2015; Liu et al., 2009; Ma et al., 2014; Qin et al., 2010; Zeng et al., 2011). Regenerated ammonia decarbonization where the decarbonization liquid is generated by heating is the main research direction (Ciferno et al., 2005; Corti and Lombardi, 2004). In ammonia decarbonization process, desorption of decarbonization liquid is mainly relied on heating and relevant researches have been studied worldwide. Fang et al. (2009) heated solution to 60–90 ◦ C at constant pressure, and found that temper-
∗ Corresponding author. E-mail address: [email protected] (S. Ma). http://dx.doi.org/10.1016/j.ijggc.2016.07.013 1750-5836/© 2016 Elsevier Ltd. All rights reserved.
ature and concentration of solution have an important influence on desorption. Experiments were conducted by NETL (Resnik et al., 2006, 2004) to study CO2 desorption, and relevant desorption data at 48.9–87.8 ◦ C conditions were obtained. In desorption experiments performed by Yeh et al. (2005), CO2 desorption ratio was reached to 60%, when 20% ammonium bicarbonate solution was heated and kept at 87.8 ◦ C. Ma et al. (2012) presented that desorption ratio of CO2 is only 32.82% at 60 ◦ C, and desorption rates were increased to 59.04% and 67.94% at 80 ◦ C and 90 ◦ C respectively. Moreover, increasing temperatures were considered to cause significant ammonia escape, meanwhile temperature was the leading factor to energy consumption in traditional heating method (Ma et al., 2015). Overall desorption method with both high efficiency and low temperature is needed. The special performance of sound wave in degassing has caused widely concern in researchers. Wilhelm’s research group from France (Laugier et al., 2008; Lekhal et al., 1997; Monnier et al., 1999; Pandit et al., 2004; Ratoarinoro et al., 1992; Sochard et al., 1998) studied the gas solubility and gas-liquid mass transfer in different type of ultrasonic reactor, and the results showed that the effect of ultrasonic on reduction of apparent solubility was not significant (less than 12%),while gas-liquid mass transfer was promoted through “micro-mixing” effect of ultrasonic. According to results, the degassing efficiency could be increased by more than 2 times, and gas removal and gas-liquid mass transfer at low frequencies
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were better than those at the high frequencies. Xu, Wang et al. from Lanzhou University (Wang, 2001; Xiao-Ming et al., 2006) treated high concentration NH3 -N wastewater with ultrasonic technology. Experimental data proved that compared with conventional stripping techniques, the removal rate of NH3 -N increased by 17% to 64%. Hui et al. (2009) applied ultrasonic to sodium alkali desulfurization solution, and found the promotion by ultrasonic on SO2 desorption in rich liquid. The enhancement on SO2 removal by ultrasonic was based on the acceleration of H2 SO3 decomposition which amplified the total volumetric mass transfer coefficient. Currently there are few researches on decarbonization solution desorption using sound wave. Relative data have been still insufficient. Therefore, based on the effect of sound wave in degassing, sound wave was studied on main components of decarbonization solution in the paper. Characteristics of CO2 desorption under sound wave were obtained at different temperatures and concentrations. Influences of different factors on sound wave desorption were analyzed. 2. Mechanism analysis on CO2 desorption with sound wave Under traditional heating conditions, regeneration process is reverse reaction of chemical absorption essentially. Various products generated in absorption process, such as NH4 HCO3 , (NH4 )2 CO3 and NH2 COONH4 , are heated and decomposed by heating. The main reactions in the conventional heating desorption are as follows (Chen et al., 2012; Ma et al., 2011):
3.2. Experimental apparatus Fig. 1 reveals the experimental apparatus used in the experiment. N2 was sent into desorption reactor through a mass flow controller (CS200, Beijing SevenStar Huachuang electronics Co., Ltd., China) as the blow gas, blowing out desorbed CO2 . Desorption reactor consisted of custom-made jacket beaker and ultrasonic generator. The jacket beaker was connected to super thermostatic water bath, to maintain the reaction temperature at 30–80 ◦ C. The main part of sound generator was piezoelectric ceramic transducer (17 kHz, 16 W). 140 mL solution was injected in every experiment. A tetrafluoroethylene blade was installed on the liquid surface right above transducer (the radius of blade was smaller than that of liquid surface), to prevent the fogging of solution. After desorption, mixed gas was sent into CO2 gas analyzer (GS1003, Shenzhen Bester analytical instrument Co., Ltd., China) after condensation (maintained by another super thermostatic water bath to keep condenser temperature at 20 ◦ C), pickling and drying to determine the outlet CO2 concentration as well as recording. The recording time for NH4 HCO3 was 25 min, and for (NH4 )2 CO3 the time was 30 min. When it turned to detect NH3 volume concentration, the gas path was converted. The temperature of condenser was set the same as jacket beaker. After CO2 was removed by NaOH solid particle, gas was sent to NH3 gas analyzer (SR-2000A series, Shandong Huafen-Sunrise analytical instrument Co., Ltd., China), in range of 0–2.5%.
NH2 COONH4 (aq) + H2 O(l) → NH4 HCO3 (aq) + NH3 (aq)
H = 30.70 kJ/mol
(1)
2NH4 HCO3 (aq) → (NH4 )2 CO3 (aq) + CO2 (g) + H2 O(l)
H = 27.51 kJ/mol
(2)
2NH4 HCO3 (aq) → NH3 (aq) + CO2 (g) + H2 O(l)
H = 64.87 kJ/mol
(3)
(NH4 )2 CO3 (aq) → 2NH3 (aq) + CO2 (g) + H2 O(l)
H = 102.23 kJ/mol
(4)
Formula (1) is endothermic hydrolysis process of carbaminate. As the solution temperature rises, the reaction moves toward right. Formula (2)–(4) is the thermal decomposition process of carbonate and bicarbonate in the solution. Meanwhile part of NH3 and H2 O in solution will leave solution with regeneration gas stream. Coupling sound wave does not change the original chemical reaction process in principle. On one hand, sound wave accelerates molecular vibrations in solution, promoting diffusion. On the other hand, especially in ultrasonic condition, ultrasonic cavitation phenomenon also affects desorption. CO2 dissolved in the liquid after decomposition can form cavitation bubbles in the sound wave field, then grow and gather into larger bubbles, finally rise to liquid surface and release CO2 . Sound wave degassing can be divided into three stages: (1) cavitation bubble nucleation stage; (2) bubbles growing stage; (3) escape stage when large bubbles float to the liquid surface and collapse (Henglein, 1987; Mason, 1991, 1992, 2003; Xu et al., 2007; Yanagida, 2008). 3. Experiment 3.1. Reagents The reagents used in the experiment: ammonium bicarbonate (AR), ammonium carbonate (AR), ammonium sulfate (AR), anhydrous calcium chloride (AR), sodium hydroxide (AR), were purchased from Tianjin Kermel Chemical reagent Co., Ltd.; concentrated sulfuric acid (AR) was purchased from Tianjin (Hong Kong) Xintong fine Chemical Co., Ltd.; N2 (99.996%) was purchased from Baoding North Special gas Co., Ltd.
3.3. Parameters CO2 desorption rate reflects the degree of CO2 desorption in decarbonization solution, defined as follows: CO2 =
1000 × MCO2 [C] × V
(5)
where [C] is the carbon concentration in the initial solution, mol/L; V is the initial volume of the solution, mL; MCO2 is total amount of CO2 desorption, mol, calculated as follows: MCO2 =
CCO2 MN2 t 100 − CCO2
(6)
where CCO2 is volume concentration of CO2 gas at the outlet, vol%; MN2 is flow rate of blow gas, mol/min, which can be calculated through the data obtained by the mass flow controller; t is time interval in the process of recording, min. Similar to Formula (6), the amount of ammonia escape is calculated by Formula (7): MNH3 =
CNH3 MN2 t 100 − CNH3
(7)
where CNH3 is volume concentration of CO2 , vol%. The increments of CO2 desorption and ammonia escape can be obtained by calculating the difference between inlet and outlet.
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Fig. 1. Schematic view of the experimental apparatus.
4. Results and discussion 4.1. Desorption performance of sound wave under different temperature Gas solubility in the liquid phase decreases as the temperature rises, so elevating temperature may promote desorption of gas in the solution. In this study, desorption performance of sound wave to NH4 HCO3 and (NH4 )2 CO3 at different temperatures were studied. The concentration of NH4 HCO3 and (NH4 )2 CO3 is 1 mol/L; blow flow of N2 is at 100 sccm. Fig. 2 is the volume concentration curve of CO2 at the outlet with and without sound wave under different temperature. The symbol ‘−’ represents curves without sound waves while ‘+’ represents those with sound waves. According to the trends in Fig. 2, as desorption time went by, CO2 volume concentration at the outlet increases dramatically at the first and then levels off; the reaction is intense in the first 15 min and CO2 volume concentration reaches the maximum at about the fifth min, up to more than 50 vol%. This mainly depends on reactant
Fig. 2. Desorption performance of NH4 HCO3 at different temperature.
concentration, furthermore, initial solution has the highest concentration. On the basis of online recording data in Fig. 2, differences between the results of ‘+’ and ‘−’ at the same temperature conclude that CO2 was desorbed by NH4 HCO3 with sound waves faster than that without sound waves. Moreover, in order to compare easily, data was processed according to Equations (5) and (6), and results are shown in Fig. 3. All the following figures were obtained in the same way. The CO2 desorption rate of NH4 HCO3 and (NH4 )2 CO3 at different temperatures are as shown in Figs. 3 and 4. Whether there is sound wave or not, desorption rate increases rapidly as the temperature rises; without sound wave, desorption rate of NH4 HCO3 increases from 4.83% at 30 ◦ C to 35.81% at 80 ◦ C, indicating that temperature was the dominating factor. It can be seen from Figs. 3 and 4 that desorption rate of NH4 HCO3 solution can be 35.8% if heated to 80 ◦ C, while (NH4 )2 CO3 solution can only be 12.7%. Besides, the enthalpy data in Formula (2)–(4) also demonstrate the fact that desorption rate of NH4 HCO3 is higher than that of (NH4 )2 CO3 . Comparison between curves with and without sound wave proves the promotion in desorption rate at various temperatures, and
Fig. 3. NH4 HCO3 desorption rate at different temperatures.
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Fig. 4. (NH4 )2 CO3 desorption rate at different temperatures.
Fig. 6. (NH4 )2 CO3 desorption rate under at different (NH4 )2 CO3 concentrations.
Fig. 7. Desorption rate under at different (NH4 )2 SO4 concentrations. Fig. 5. NH4 HCO3 desorption rate under at different NH4 HCO3 concentrations.
elevating temperature also enhances the degassing ability. From comparison in desorption amount increments, it shows clear evidence that sound wave promoted desorption in both NH4 HCO3 solution and (NH4 )2 CO3 solution. Desorption increments of both solution are almost the same beyond 50 ◦ C. This is mainly related to constant energy of sound wave. Sound wave promoted desorption of NH4 HCO3 solution more effectually than that of (NH4 )2 CO3 solution below 50 ◦ C. This is because that (NH4 )2 CO3 hardly decomposes below 50 ◦ C while NH4 HCO3 decomposes easily at the same temperature. Therefore it can be concluded that the effect of sound wave (17 kHz, 16 W) mainly enhances diffusion of CO2 instead of decomposition reaction. 4.2. Desorption performance under different carbon concentration NH4 HCO3 and (NH4 )2 CO3 solution at 0.2–1 mol/L were prepared; experiment was conducted at 50 ◦ C, 100 sccm blow flow. After data processing, results of different substances at different concentration are shown in Figs. 5 and 6. In NH4 HCO3 and (NH4 )2 CO3 solutions, CO2 desorption rate gradually increases with solution concentration elevating, indicating that the higher rich liquid concentration was beneficial for desorption in carbon capture process. By comparison, sound wave enhances desorption both in NH4 HCO3 and (NH4 )2 CO3 at different concentrations. Desorption rates of NH4 HCO3 and (NH4 )2 CO3 solution at 0.8 mol/L increases from 7.53% and 1.36% to 11.27% and 2.84% respectively. Desorption increment is relatively small at low con-
centrations. This is due to the directionality of piezoelectric ceramic transducer energy. Not all solution can be effectively affected. The effect is limited when the concentration is too low, and gradually stabilizes when concentration increases. Therefore increasing concentration had positive effect. Moreover Xu Hui’s research pointed out that sound wave promotes SO2 removal mainly because it accelerated the decomposition of H2 SO3 . In the process, sound wave could enhance the decomposition reaction as a kind of energy when sound wave provided enough energy (Hui et al., 2009). But this phenomenon has not appeared obviously in Figs. 5 and 6. This is possibly caused by insufficient energy using 16 W transducer. 4.3. Desorption performance with existence of (NH4 )2 SO4 According to the characteristics of carbon capture systems and environmental protection equipment in power plants, SO2 remained after desulfurization can be gathered in the carbon capture system. It may generate into (NH4 )2 SO4 and stay in the solution. In the experiment to study the effect of (NH4 )2 SO4 on desorption, (NH4 )2 SO4 was added into NH4 HCO3 solution and the total concentration of both substance were kept at 1 mol/L. The recording time was 25 min; N2 blow flow was 100sccml; temperature was 50 ◦ C. After data processing, the results are shown in Fig. 7. The initial pH of the solution was measured, and the results are in Fig. 7. According to desorption rate with (NH4 )2 SO4 in Fig. 7, it can be deduced that the existence of (NH4 )2 SO4 will not significantly affect sound wave energy conduction. Compared with curve without (NH4 )2 SO4 , however, CO2 desorption rate showed an opposite trend when (NH4 )2 SO4 existed. (NH4 )2 SO4 is strong acid
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amount were fitted, and regression curve was shown in Fig. 9. According to Line A, only 54 ◦ C is required theoretically with sound wave to reach the CO2 desorption rate in 60 ◦ C, and the amount of NH3 escape is as low as that at 57 ◦ C. In Line B, desorption amount at 75 ◦ C with sound wave is theoretically equivalent to 80 ◦ C, while NH3 escape is as low as that in 77 ◦ C. In conclusion, the enhancement in CO2 desorption is much higher than the increase in NH3 escape under sound wave. NH3 escape caused by coupling sound wave was limited in the process of enhancing CO2 desorption. 5. More discussions
Fig. 8. NH3 escape under sound wave at different temperatures.
Fig. 9. Increment of NH3 escape and CO2 desorption rate.
weak base salt, showing weak acid after hydrolysis. Increasing (NH4 )2 SO4 leads to decline in pH which is conducive to decomposition of NH4 HCO3 and CO2 desorption. Therefore, desorption rate increased with the presence of (NH4 )2 SO4 . But excessively enriched (NH4 )2 SO4 may improve ionic strength, affecting absorption capacity after desorption, or even causing crystallization blockage. Consequently, (NH4 )2 SO4 can be allowed in desorption solution, as long as the content is limited. 4.4. NH3 escape under sound wave condition Sound wave can promote molecular motion and diffusion, not only enhancing CO2 desorption, but also affecting the NH3 escape in desorption process. In order to explore the effect of sound wave on NH3 escape, the original CO2 monitoring was turned into monitoring on NH3 volume concentration after desorption. The blow flow was 100 sccm and NH4 HCO3 concentration was controlled at 1 mol/L. The amounts of NH3 escape after data processing are shown in Fig. 8. CO2 desorption and NH3 escape under sound wave are compared in Fig. 9. In Fig. 8, NH3 escape increases rapidly as the temperature rises whether with sound wave or not. Within 25 min, NH3 escape rises from 0.000933 mol at 40 ◦ C to 0.01079 mol at 70 ◦ C, without sound wave. From 30 to 50 ◦ C, the curves of NH3 escape are close and well within the usual margins of error. NH3 escape increases with the temperature elevating beyond 50 ◦ C, meanwhile the existence of sound wave enhances NH3 escape to some extent. Therefore, NH3 escape has to be considered when desorption rate is enhanced by high temperature (>50 ◦ C). CO2 desorption amount and NH3 escape
The experimental results show that sound wave was theoretically available in enhancing CO2 desorption and reducing requirement of temperature for desorption. However, the application of sound generator in industrial process is not so easy as that in the laboratory. In the application, the installment of sound generator can be divided into two ways: external connection to desorption vessels or inner installment. If the vessels are connected outside, the energy distribution is better, but the overall vibration problem cannot be ignored. If they are placed inside, the overall vibration will not be affected, but high sealing and anti-corrosion properties of generator are required in the ammonia environment. Ammonia easily corrodes active metals, such as copper. Stainless steel and other corrosion-resistant materials are required. What’s more, laboratory conditions is different from actual ammonia decarbonization project, accordingly, the actual situation cannot be simulated thoroughly. In this research, the promotion of sound wave in NH4 HCO3 desorption was proved. Enhancement of sound wave in desorption under various condition was demonstrated, but the microscopic mechanism has not been researched due to limited equipment conditions. Further exploration remains to be conducted in terms of frequency, amplitude and so on, which are meaningful for microscopic mechanism clarification and energy consumption assessment. Further mechanism research should be the focus in future research. 6. Conclusions (1) Whether there is sound wave or not, desorption rates increased rapidly as the temperature raised. Without sound wave, desorption rate of NH4 HCO3 increased from 4.83% at 30 ◦ C to 35.81% at 80 ◦ C. The temperature remained the dominating factor. Comparison of curves with and without sound wave has proved the promotion of sound wave on desorption rates at any temperature. Sound wave had a promoting effect on NH4 HCO3 and (NH4 )2 CO3 at different concentrations. Desorption rates of 0.8 mol/L NH4 HCO3 and (NH4 )2 CO3 were increased from 7.53% and 1.36% to 11.27% and 2.84% respectively. (2) From comparison in desorption amount increments, it can be found that sound wave promoted desorption in both NH4 HCO3 solution and (NH4 )2 CO3 solution. Desorption increments of both solution were almost the same beyond 50 ◦ C. This is mainly related to constant energy of sound wave. Sound wave promoted desorption of NH4 HCO3 solution more than that of (NH4 )2 CO3 solution below 50 ◦ C. This is because that (NH4 )2 CO3 hardly decomposes below 50 ◦ C while NH4 HCO3 decomposes easily at the same temperature. Therefore it can be concluded that the effect of sound wave (17 kHz, 16 W) mainly enhanced diffusion of CO2 instead of decomposition reaction. (3) Increasing (NH4 )2 SO4 lead to decline in pH which is conducive to NH4 HCO3 decomposition and CO2 desorption. Therefore, desorption rate increased with the presence of (NH4 )2 SO4 . But excessively enriched (NH4 )2 SO4 may improve ionic strength, affecting the absorption capacity after desorption, or even caus-
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ing crystallization blockage. Consequently, (NH4 )2 SO4 can be allowed in desorption solution, as long as the content is limited. (4) Whether there was sound wave or not, ammonia escape increased rapidly. Without sound wave, ammonia escape increased from 0.000933 mol at 40 ◦ C to 0.01079 mol at 70 ◦ C in 25 min. Therefore, ammonia escape should be considered while improving desorption efficiency of CO2 through temperature. However, the enhancement in CO2 desorption was much higher than the increase in NH3 escape under sound wave. NH3 escape caused by coupling sound wave in the process of enhancing CO2 desorption is limited. Acknowledgements The authors are highly thankful for the financial supports of the Fundamental Research Funds for the Central Universities of North China Electric Power University (2014ZD39, 2016 XS113). References An, C.Y., Bai, H., 1999. Comparison of ammonia and monoethanolamine solvents to reduce CO2 greenhouse gas emissions. Sci. Total Environ. 228, 121–133. And, H.B., An, C.Y., 1997. Removal of CO2 greenhouse gas by ammonia scrubbing. Ind. Eng. Chem. Res. 36, 2490–2493. Chen, H., Dou, B., Song, Y., Xu, Y., Wang, X., Zhang, Y., Du, X., Wang, C., Zhang, X., Tan, C., 2012. Studies on absorption and regeneration for CO2 capture by aqueous ammonia. Int. J. Greenh. Gas Control 6, 171–178. Ciferno, J., Dipietro, P., Tarka, T., 2005. An Economic Scoping Study for CO2 Capture Using Aqueous Ammonia. Final Report. Corti, A., Lombardi, L., 2004. Reduction of carbon dioxide emissions from a SCGT/CC by ammonia solution absorption—preliminary results. Int. J. Thermodyn. 7. Davison, J., 2007. Performance and costs of power plants with capture and storage of CO2 . Energy 32, 1163–1176. Fang, L., Wang, S., Xi, Z., Sun, X., Chen, C., 2009. Study on ammonium bicarbonate decomposition after CO2 sequestration by ammonia method. Huanjing Kexue Xuebao 29, 1886–1890. Han, K., Chi, K.A., Man, S.L., Chang, H.R., Kim, J.Y., Chun, H.D., 2013. Current status and challenges of the ammonia-based CO2 capture technologies toward commercialization. Int. J. Greenh. Gas Control 14, 270–281. Henglein, A., 1987. Sonochemistry: historical developments and modern aspects. Ultrasonics 25, 6–16. Hui, X.U., Zhang, S.T., Wang, W.Z., Tong, S.U., 2009. Desorption of SO2 from sodium alkali solution by ultrasonic. Meitan Xuebao/J. China Coal Soc. 34, 542–545. Laugier, F., Andriantsiferana, C., Wilhelm, A.M., Delmas, H., 2008. Ultrasound in gas–liquid systems: effects on solubility and mass transfer. Ultrason. Sonochem. 15, 965–972. Lei, L., Ning, Z., Wei, W., Sun, Y., 2013. A review of research progress on CO2 capture, storage, and utilization in Chinese Academy of Sciences. Fuel 108, 112–130. Lekhal, A., Chaudhari, R.V., Wilhelm, A.M., Delmas, H., 1997. Gas–liquid mass transfer in gas–liquid–liquid dispersions. Chem. Eng. Sci. 52, 4069–4077. Liang, Z.W., Rongwong, W., Liu, H.L., Fu, K.Y., Gao, H.X., Cao, F., Zhang, R., Sema, T., Henni, A., Sumon, K., Nath, D., Gelowitz, D., Srisang, W., Saiwan, C., Benamor, A., Al-Marri, M., Shi, H.C., Supap, T., Chan, C., Zhou, Q., Abu-Zahra, M., Wilson, M., Olson, W., Idem, R., Tontiwachwuthikul, P., 2015. Recent progress and new developments in post-combustion carbon-capture technology with amine based solvents. Int. J. Greenh. Gas Control 40, 26–54. Liang, Z., Idem, R., Tontiwachwuthikul, P., Yu, F., Liu, H., Rongwong, W., 2016a. Experimental study on the solvent regeneration of a CO2 -loaded MEA solution using single and hybrid solid acid catalysts. AIChE J. 62, 753–765. Liang, Z.W., Idem, R., Tontiwachwuthikul, P., Yu, F.H., Liu, H.L., Rongwong, W., 2016b. Experimental study on the solvent regeneration of a CO2 -loaded MEA solution using single and hybrid solid acid catalysts. AIChE J. 62, 753–765.
Liu, F., Wang, S., Chen, C., Xuchang, X.U., 2009. Research progress of CO2 capture by using ammonia from flue gas of power plant. J. Chem. Ind. Eng. Soc. China 60, 269–278. Luo, X., Fu, K.Y., Yang, Z., Gao, H.X., Rongvvong, W., Liang, Z.W., Tontiwach-Wuthikult, P., 2015. Experimental studies of reboiler heat duty for CO2 desorption from triethylenetetramine (TETA) and triethylenetetramine (TETA) plus N-methyldiethanolamine (MDEA). Ind. Eng. Chem. Res. 54, 8554–8560. Ma, Sun, Zhao, S., Fang, Y., Han, Y., Liang, W., Pizhao, J., 2011. Experimental and mechanism research on CO2 capture from simulating flue gas using ammonia solution. Acta Chim. Sin. 69, 1469–1474. Ma, ShuangChen, Wang, MengXuan, Han, TingTing, Chen, WeiZhong, Lu, DongLi, 2012. Research on desorption and regeneration of simulated decarbonization solution in the process of CO2 capture using ammonia method. Sci. China Technol. Sci. 55, 3411–3418. Ma, S., Wang, M., Han, T., Song, H., Zang, B., Lu, D., Chen, W., 2013. Kinetic experimental study on desorption of decarbonization solution using ammonia method. Chem. Eng. J. 217, 22–27. Ma, S., Chen, G., Guo, M., Zhao, L., Han, T., Zhu, S., 2014. Path analysis on CO2 resource utilization based on carbon capture using ammonia method in coal-fired power plants. Renew. Sustain. Energy Rev. 37, 687–697. Ma, S., Chen, G., Han, T., Zhu, S., Yang, J., 2015. Experimental study on the effect of Ni(II) additive on ammonia escape in CO2 capture using ammonia solution. Int. J. Greenh. Gas Control 37, 249–255. Macfarlane, J.W., Scott, T.B., 2012. Reduction of carbon dioxide on jet spray formed titanium dioxide surfaces. J. Hazard. Mater. 211–212, 247–254. Mason, T.J., 1991. Industrial sonochemistry: potential and practicality. Meeting of European Society of Sonochemistry, 192–196. Mason, T.J., 1992. Current Trends in Sonochemistry, Sonochemistry Workshop for French Industrialists. Mason, T.J., 2003. Sonochemistry and sonoprocessing: the link, the trends and (probably) the future. Ultrason. Sonochem. 10, 175–179. Mondal, M.K., Balsora, H.K., Varshney, P., 2012. Progress and trends in CO2 capture/separation technologies: a review. Energy 46, 431–441. Monnier, H., Wilhelm, A.M., Delmas, H., 1999. The influence of ultrasound on micromixing in a semi-batch reactor. Chem. Eng. Sci. 54, 2953–2961. Pandit, A.B., Kumar, A., Gogate, P.R., 2004. Gas–liquid mass transfer studies in sonochemical reactors. Ind. Eng. Chem. Res. 43, 1812–1819. Qin, F., Wang, S., Hartono, A., Svendsen, H.F., Chen, C., 2010. Kinetics of CO2 absorption in aqueous ammonia solution. Int. J. Greenh. Gas Control 4, 729–738. Ratoarinoro, N., Wilhelm, A.M., Berlan, J., Delmas, H., 1992. Effects of ultrasound emitter type and power on a heterogeneous reaction. Chem. Eng. J. 50, 27–31. Resnik, K.P., Yeh, J.T., Pennline, H.W., 2004. Aqua ammonia process for simultaneous removal of CO2 , SO2 and NOx . Int. J. Environ. Technol. Manag. 4, 89–104. Resnik, K.P., Garber, W., Hreda, D.C., Yeh, J.T., Pennline, H.W., Resnik, K.P., Garber, W., Hreda, D.C., Yeh, J.T., Pennline, H.W., 2006. A Parametric Study for Regenerative Ammonia-Based Scrubbing for the Capture of CO2 . Sochard, S., Wilhelm, A.M., Delmas, H., 1998. Gas–vapour bubble dynamics and homogeneous sonochemistry. Chem. Eng. Sci. 53, 239–254. Wang, Y., 2001. Treatment of ammonia nitrogen wastewater by ultrasonic stripping. Technigues & Equipment for Enviro.poll.cont. Xiao-Ming, X.U., Wang, Y.L., Yan, L.I., 2006. Experimental investigation of processing conditions for treatment wastewater containing ammonia nitrogen with ultrasonic stripping. J. Lanzhou Univ. Technol. 32, 67–69. Xu, H., Meek, T.T., Han, Q., 2007. Effects of ultrasonic field and vacuum on degassing of molten aluminum alloy. Mater. Lett. 61, 1246–1250. Yanagida, H., 2008. The effect of dissolve gas concentration in the initial growth stage of multi cavitation bubbles: differences between vacuum degassing and ultrasound degassing. Ultrason. Sonochem. 15, 492–496. Yeh, J.T., Resnik, K.P., Rygle, K., Pennline, H.W., 2005. Semi-batch absorption and regeneration studies for CO2 capture by aqueous ammonia. Fuel Process. Technol. 86, 1533–1546. Zeng, Q., Guo, Y., Niu, Z., Lin, W., 2011. Mass transfer performance of CO2 absorption into aqueous ammonia in a packed column. CIESC J. 62, 146–150.
Contents lists available at ScienceDirect
International Journal of Greenhouse Gas Control journal homepage: www.elsevier.com/locate/ijggc
Experimental research on desorption of ammonia decarbonization solution coupled sound wave Ma Shuangchen ∗ , Chen Gongda, Gao Ran, Zhu Sijie, Weng Xiaoyu, Jiao Kunling School of Environment, North China Electric Power University, Baoding 071003, China
a r t i c l e
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Article history: Received 25 April 2016 Received in revised form 30 June 2016 Accepted 11 July 2016 Available online 19 July 2016 Keywords: Decarbonization Ammonia solution Desorption Sound wave
a b s t r a c t Currently, regeneration of decarbonization liquid and separation of pure CO2 have been realized by heating ammonia decarbonization solution. However, elevated temperature will lead to significant ammonia escape and energy consumption with traditional desorption method. Given the role of sound in degassing, sound wave was used to desorb decarbonization solution in this research. On self-designed experimental equipment, desorption of decarbonization liquid was studied coupled sound wave. To discuss multi-factor influences on sound wave desorption, basic characteristics of sound wave for desorption under different temperatures and concentrations were revealed. In the experiment, under 16 W sound wave, the desorption rate of NH4 HCO3 solution increased from 9.8% to 13.76% at 50 ◦ C, compared with no sound wave condition; while at 70 ◦ C, the desorption rate raised from 25.4% to 30.51%. By adding sound wave, the increment of desorbed CO2 was higher than that of escaped ammonia. The possibility of applying sound wave to desorption process in ammonia decarbonization was discussed, and a method of accelerating desorption was provided in the paper. © 2016 Elsevier Ltd. All rights reserved.
1. Introduction In recent years, excessive emissions of CO2 and other greenhouse gases that cause climate change have become a worldwide environmental problem (Han et al., 2013; Liang et al., 2016a,b; Luo et al., 2015; Macfarlane and Scott, 2012; Mondal et al., 2012). CO2 mainly comes from fossil fuels burning, especially the combustion in power plants. Therefore CO2 emission reduction in power plants is crucial to curb global climate anomalies (Davison, 2007; Lei et al., 2013; Ma et al., 2013). Among many carbon abatement methods, ammonia solution was regarded as a feasible absorbent for its low cost, high absorption efficiency and low corrosion (An and Bai, 1999; And and An, 1997; Liang et al., 2015; Liu et al., 2009; Ma et al., 2014; Qin et al., 2010; Zeng et al., 2011). Regenerated ammonia decarbonization where the decarbonization liquid is generated by heating is the main research direction (Ciferno et al., 2005; Corti and Lombardi, 2004). In ammonia decarbonization process, desorption of decarbonization liquid is mainly relied on heating and relevant researches have been studied worldwide. Fang et al. (2009) heated solution to 60–90 ◦ C at constant pressure, and found that temper-
∗ Corresponding author. E-mail address: [email protected] (S. Ma). http://dx.doi.org/10.1016/j.ijggc.2016.07.013 1750-5836/© 2016 Elsevier Ltd. All rights reserved.
ature and concentration of solution have an important influence on desorption. Experiments were conducted by NETL (Resnik et al., 2006, 2004) to study CO2 desorption, and relevant desorption data at 48.9–87.8 ◦ C conditions were obtained. In desorption experiments performed by Yeh et al. (2005), CO2 desorption ratio was reached to 60%, when 20% ammonium bicarbonate solution was heated and kept at 87.8 ◦ C. Ma et al. (2012) presented that desorption ratio of CO2 is only 32.82% at 60 ◦ C, and desorption rates were increased to 59.04% and 67.94% at 80 ◦ C and 90 ◦ C respectively. Moreover, increasing temperatures were considered to cause significant ammonia escape, meanwhile temperature was the leading factor to energy consumption in traditional heating method (Ma et al., 2015). Overall desorption method with both high efficiency and low temperature is needed. The special performance of sound wave in degassing has caused widely concern in researchers. Wilhelm’s research group from France (Laugier et al., 2008; Lekhal et al., 1997; Monnier et al., 1999; Pandit et al., 2004; Ratoarinoro et al., 1992; Sochard et al., 1998) studied the gas solubility and gas-liquid mass transfer in different type of ultrasonic reactor, and the results showed that the effect of ultrasonic on reduction of apparent solubility was not significant (less than 12%),while gas-liquid mass transfer was promoted through “micro-mixing” effect of ultrasonic. According to results, the degassing efficiency could be increased by more than 2 times, and gas removal and gas-liquid mass transfer at low frequencies
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were better than those at the high frequencies. Xu, Wang et al. from Lanzhou University (Wang, 2001; Xiao-Ming et al., 2006) treated high concentration NH3 -N wastewater with ultrasonic technology. Experimental data proved that compared with conventional stripping techniques, the removal rate of NH3 -N increased by 17% to 64%. Hui et al. (2009) applied ultrasonic to sodium alkali desulfurization solution, and found the promotion by ultrasonic on SO2 desorption in rich liquid. The enhancement on SO2 removal by ultrasonic was based on the acceleration of H2 SO3 decomposition which amplified the total volumetric mass transfer coefficient. Currently there are few researches on decarbonization solution desorption using sound wave. Relative data have been still insufficient. Therefore, based on the effect of sound wave in degassing, sound wave was studied on main components of decarbonization solution in the paper. Characteristics of CO2 desorption under sound wave were obtained at different temperatures and concentrations. Influences of different factors on sound wave desorption were analyzed. 2. Mechanism analysis on CO2 desorption with sound wave Under traditional heating conditions, regeneration process is reverse reaction of chemical absorption essentially. Various products generated in absorption process, such as NH4 HCO3 , (NH4 )2 CO3 and NH2 COONH4 , are heated and decomposed by heating. The main reactions in the conventional heating desorption are as follows (Chen et al., 2012; Ma et al., 2011):
3.2. Experimental apparatus Fig. 1 reveals the experimental apparatus used in the experiment. N2 was sent into desorption reactor through a mass flow controller (CS200, Beijing SevenStar Huachuang electronics Co., Ltd., China) as the blow gas, blowing out desorbed CO2 . Desorption reactor consisted of custom-made jacket beaker and ultrasonic generator. The jacket beaker was connected to super thermostatic water bath, to maintain the reaction temperature at 30–80 ◦ C. The main part of sound generator was piezoelectric ceramic transducer (17 kHz, 16 W). 140 mL solution was injected in every experiment. A tetrafluoroethylene blade was installed on the liquid surface right above transducer (the radius of blade was smaller than that of liquid surface), to prevent the fogging of solution. After desorption, mixed gas was sent into CO2 gas analyzer (GS1003, Shenzhen Bester analytical instrument Co., Ltd., China) after condensation (maintained by another super thermostatic water bath to keep condenser temperature at 20 ◦ C), pickling and drying to determine the outlet CO2 concentration as well as recording. The recording time for NH4 HCO3 was 25 min, and for (NH4 )2 CO3 the time was 30 min. When it turned to detect NH3 volume concentration, the gas path was converted. The temperature of condenser was set the same as jacket beaker. After CO2 was removed by NaOH solid particle, gas was sent to NH3 gas analyzer (SR-2000A series, Shandong Huafen-Sunrise analytical instrument Co., Ltd., China), in range of 0–2.5%.
NH2 COONH4 (aq) + H2 O(l) → NH4 HCO3 (aq) + NH3 (aq)
H = 30.70 kJ/mol
(1)
2NH4 HCO3 (aq) → (NH4 )2 CO3 (aq) + CO2 (g) + H2 O(l)
H = 27.51 kJ/mol
(2)
2NH4 HCO3 (aq) → NH3 (aq) + CO2 (g) + H2 O(l)
H = 64.87 kJ/mol
(3)
(NH4 )2 CO3 (aq) → 2NH3 (aq) + CO2 (g) + H2 O(l)
H = 102.23 kJ/mol
(4)
Formula (1) is endothermic hydrolysis process of carbaminate. As the solution temperature rises, the reaction moves toward right. Formula (2)–(4) is the thermal decomposition process of carbonate and bicarbonate in the solution. Meanwhile part of NH3 and H2 O in solution will leave solution with regeneration gas stream. Coupling sound wave does not change the original chemical reaction process in principle. On one hand, sound wave accelerates molecular vibrations in solution, promoting diffusion. On the other hand, especially in ultrasonic condition, ultrasonic cavitation phenomenon also affects desorption. CO2 dissolved in the liquid after decomposition can form cavitation bubbles in the sound wave field, then grow and gather into larger bubbles, finally rise to liquid surface and release CO2 . Sound wave degassing can be divided into three stages: (1) cavitation bubble nucleation stage; (2) bubbles growing stage; (3) escape stage when large bubbles float to the liquid surface and collapse (Henglein, 1987; Mason, 1991, 1992, 2003; Xu et al., 2007; Yanagida, 2008). 3. Experiment 3.1. Reagents The reagents used in the experiment: ammonium bicarbonate (AR), ammonium carbonate (AR), ammonium sulfate (AR), anhydrous calcium chloride (AR), sodium hydroxide (AR), were purchased from Tianjin Kermel Chemical reagent Co., Ltd.; concentrated sulfuric acid (AR) was purchased from Tianjin (Hong Kong) Xintong fine Chemical Co., Ltd.; N2 (99.996%) was purchased from Baoding North Special gas Co., Ltd.
3.3. Parameters CO2 desorption rate reflects the degree of CO2 desorption in decarbonization solution, defined as follows: CO2 =
1000 × MCO2 [C] × V
(5)
where [C] is the carbon concentration in the initial solution, mol/L; V is the initial volume of the solution, mL; MCO2 is total amount of CO2 desorption, mol, calculated as follows: MCO2 =
CCO2 MN2 t 100 − CCO2
(6)
where CCO2 is volume concentration of CO2 gas at the outlet, vol%; MN2 is flow rate of blow gas, mol/min, which can be calculated through the data obtained by the mass flow controller; t is time interval in the process of recording, min. Similar to Formula (6), the amount of ammonia escape is calculated by Formula (7): MNH3 =
CNH3 MN2 t 100 − CNH3
(7)
where CNH3 is volume concentration of CO2 , vol%. The increments of CO2 desorption and ammonia escape can be obtained by calculating the difference between inlet and outlet.
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Fig. 1. Schematic view of the experimental apparatus.
4. Results and discussion 4.1. Desorption performance of sound wave under different temperature Gas solubility in the liquid phase decreases as the temperature rises, so elevating temperature may promote desorption of gas in the solution. In this study, desorption performance of sound wave to NH4 HCO3 and (NH4 )2 CO3 at different temperatures were studied. The concentration of NH4 HCO3 and (NH4 )2 CO3 is 1 mol/L; blow flow of N2 is at 100 sccm. Fig. 2 is the volume concentration curve of CO2 at the outlet with and without sound wave under different temperature. The symbol ‘−’ represents curves without sound waves while ‘+’ represents those with sound waves. According to the trends in Fig. 2, as desorption time went by, CO2 volume concentration at the outlet increases dramatically at the first and then levels off; the reaction is intense in the first 15 min and CO2 volume concentration reaches the maximum at about the fifth min, up to more than 50 vol%. This mainly depends on reactant
Fig. 2. Desorption performance of NH4 HCO3 at different temperature.
concentration, furthermore, initial solution has the highest concentration. On the basis of online recording data in Fig. 2, differences between the results of ‘+’ and ‘−’ at the same temperature conclude that CO2 was desorbed by NH4 HCO3 with sound waves faster than that without sound waves. Moreover, in order to compare easily, data was processed according to Equations (5) and (6), and results are shown in Fig. 3. All the following figures were obtained in the same way. The CO2 desorption rate of NH4 HCO3 and (NH4 )2 CO3 at different temperatures are as shown in Figs. 3 and 4. Whether there is sound wave or not, desorption rate increases rapidly as the temperature rises; without sound wave, desorption rate of NH4 HCO3 increases from 4.83% at 30 ◦ C to 35.81% at 80 ◦ C, indicating that temperature was the dominating factor. It can be seen from Figs. 3 and 4 that desorption rate of NH4 HCO3 solution can be 35.8% if heated to 80 ◦ C, while (NH4 )2 CO3 solution can only be 12.7%. Besides, the enthalpy data in Formula (2)–(4) also demonstrate the fact that desorption rate of NH4 HCO3 is higher than that of (NH4 )2 CO3 . Comparison between curves with and without sound wave proves the promotion in desorption rate at various temperatures, and
Fig. 3. NH4 HCO3 desorption rate at different temperatures.
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Fig. 4. (NH4 )2 CO3 desorption rate at different temperatures.
Fig. 6. (NH4 )2 CO3 desorption rate under at different (NH4 )2 CO3 concentrations.
Fig. 7. Desorption rate under at different (NH4 )2 SO4 concentrations. Fig. 5. NH4 HCO3 desorption rate under at different NH4 HCO3 concentrations.
elevating temperature also enhances the degassing ability. From comparison in desorption amount increments, it shows clear evidence that sound wave promoted desorption in both NH4 HCO3 solution and (NH4 )2 CO3 solution. Desorption increments of both solution are almost the same beyond 50 ◦ C. This is mainly related to constant energy of sound wave. Sound wave promoted desorption of NH4 HCO3 solution more effectually than that of (NH4 )2 CO3 solution below 50 ◦ C. This is because that (NH4 )2 CO3 hardly decomposes below 50 ◦ C while NH4 HCO3 decomposes easily at the same temperature. Therefore it can be concluded that the effect of sound wave (17 kHz, 16 W) mainly enhances diffusion of CO2 instead of decomposition reaction. 4.2. Desorption performance under different carbon concentration NH4 HCO3 and (NH4 )2 CO3 solution at 0.2–1 mol/L were prepared; experiment was conducted at 50 ◦ C, 100 sccm blow flow. After data processing, results of different substances at different concentration are shown in Figs. 5 and 6. In NH4 HCO3 and (NH4 )2 CO3 solutions, CO2 desorption rate gradually increases with solution concentration elevating, indicating that the higher rich liquid concentration was beneficial for desorption in carbon capture process. By comparison, sound wave enhances desorption both in NH4 HCO3 and (NH4 )2 CO3 at different concentrations. Desorption rates of NH4 HCO3 and (NH4 )2 CO3 solution at 0.8 mol/L increases from 7.53% and 1.36% to 11.27% and 2.84% respectively. Desorption increment is relatively small at low con-
centrations. This is due to the directionality of piezoelectric ceramic transducer energy. Not all solution can be effectively affected. The effect is limited when the concentration is too low, and gradually stabilizes when concentration increases. Therefore increasing concentration had positive effect. Moreover Xu Hui’s research pointed out that sound wave promotes SO2 removal mainly because it accelerated the decomposition of H2 SO3 . In the process, sound wave could enhance the decomposition reaction as a kind of energy when sound wave provided enough energy (Hui et al., 2009). But this phenomenon has not appeared obviously in Figs. 5 and 6. This is possibly caused by insufficient energy using 16 W transducer. 4.3. Desorption performance with existence of (NH4 )2 SO4 According to the characteristics of carbon capture systems and environmental protection equipment in power plants, SO2 remained after desulfurization can be gathered in the carbon capture system. It may generate into (NH4 )2 SO4 and stay in the solution. In the experiment to study the effect of (NH4 )2 SO4 on desorption, (NH4 )2 SO4 was added into NH4 HCO3 solution and the total concentration of both substance were kept at 1 mol/L. The recording time was 25 min; N2 blow flow was 100sccml; temperature was 50 ◦ C. After data processing, the results are shown in Fig. 7. The initial pH of the solution was measured, and the results are in Fig. 7. According to desorption rate with (NH4 )2 SO4 in Fig. 7, it can be deduced that the existence of (NH4 )2 SO4 will not significantly affect sound wave energy conduction. Compared with curve without (NH4 )2 SO4 , however, CO2 desorption rate showed an opposite trend when (NH4 )2 SO4 existed. (NH4 )2 SO4 is strong acid
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amount were fitted, and regression curve was shown in Fig. 9. According to Line A, only 54 ◦ C is required theoretically with sound wave to reach the CO2 desorption rate in 60 ◦ C, and the amount of NH3 escape is as low as that at 57 ◦ C. In Line B, desorption amount at 75 ◦ C with sound wave is theoretically equivalent to 80 ◦ C, while NH3 escape is as low as that in 77 ◦ C. In conclusion, the enhancement in CO2 desorption is much higher than the increase in NH3 escape under sound wave. NH3 escape caused by coupling sound wave was limited in the process of enhancing CO2 desorption. 5. More discussions
Fig. 8. NH3 escape under sound wave at different temperatures.
Fig. 9. Increment of NH3 escape and CO2 desorption rate.
weak base salt, showing weak acid after hydrolysis. Increasing (NH4 )2 SO4 leads to decline in pH which is conducive to decomposition of NH4 HCO3 and CO2 desorption. Therefore, desorption rate increased with the presence of (NH4 )2 SO4 . But excessively enriched (NH4 )2 SO4 may improve ionic strength, affecting absorption capacity after desorption, or even causing crystallization blockage. Consequently, (NH4 )2 SO4 can be allowed in desorption solution, as long as the content is limited. 4.4. NH3 escape under sound wave condition Sound wave can promote molecular motion and diffusion, not only enhancing CO2 desorption, but also affecting the NH3 escape in desorption process. In order to explore the effect of sound wave on NH3 escape, the original CO2 monitoring was turned into monitoring on NH3 volume concentration after desorption. The blow flow was 100 sccm and NH4 HCO3 concentration was controlled at 1 mol/L. The amounts of NH3 escape after data processing are shown in Fig. 8. CO2 desorption and NH3 escape under sound wave are compared in Fig. 9. In Fig. 8, NH3 escape increases rapidly as the temperature rises whether with sound wave or not. Within 25 min, NH3 escape rises from 0.000933 mol at 40 ◦ C to 0.01079 mol at 70 ◦ C, without sound wave. From 30 to 50 ◦ C, the curves of NH3 escape are close and well within the usual margins of error. NH3 escape increases with the temperature elevating beyond 50 ◦ C, meanwhile the existence of sound wave enhances NH3 escape to some extent. Therefore, NH3 escape has to be considered when desorption rate is enhanced by high temperature (>50 ◦ C). CO2 desorption amount and NH3 escape
The experimental results show that sound wave was theoretically available in enhancing CO2 desorption and reducing requirement of temperature for desorption. However, the application of sound generator in industrial process is not so easy as that in the laboratory. In the application, the installment of sound generator can be divided into two ways: external connection to desorption vessels or inner installment. If the vessels are connected outside, the energy distribution is better, but the overall vibration problem cannot be ignored. If they are placed inside, the overall vibration will not be affected, but high sealing and anti-corrosion properties of generator are required in the ammonia environment. Ammonia easily corrodes active metals, such as copper. Stainless steel and other corrosion-resistant materials are required. What’s more, laboratory conditions is different from actual ammonia decarbonization project, accordingly, the actual situation cannot be simulated thoroughly. In this research, the promotion of sound wave in NH4 HCO3 desorption was proved. Enhancement of sound wave in desorption under various condition was demonstrated, but the microscopic mechanism has not been researched due to limited equipment conditions. Further exploration remains to be conducted in terms of frequency, amplitude and so on, which are meaningful for microscopic mechanism clarification and energy consumption assessment. Further mechanism research should be the focus in future research. 6. Conclusions (1) Whether there is sound wave or not, desorption rates increased rapidly as the temperature raised. Without sound wave, desorption rate of NH4 HCO3 increased from 4.83% at 30 ◦ C to 35.81% at 80 ◦ C. The temperature remained the dominating factor. Comparison of curves with and without sound wave has proved the promotion of sound wave on desorption rates at any temperature. Sound wave had a promoting effect on NH4 HCO3 and (NH4 )2 CO3 at different concentrations. Desorption rates of 0.8 mol/L NH4 HCO3 and (NH4 )2 CO3 were increased from 7.53% and 1.36% to 11.27% and 2.84% respectively. (2) From comparison in desorption amount increments, it can be found that sound wave promoted desorption in both NH4 HCO3 solution and (NH4 )2 CO3 solution. Desorption increments of both solution were almost the same beyond 50 ◦ C. This is mainly related to constant energy of sound wave. Sound wave promoted desorption of NH4 HCO3 solution more than that of (NH4 )2 CO3 solution below 50 ◦ C. This is because that (NH4 )2 CO3 hardly decomposes below 50 ◦ C while NH4 HCO3 decomposes easily at the same temperature. Therefore it can be concluded that the effect of sound wave (17 kHz, 16 W) mainly enhanced diffusion of CO2 instead of decomposition reaction. (3) Increasing (NH4 )2 SO4 lead to decline in pH which is conducive to NH4 HCO3 decomposition and CO2 desorption. Therefore, desorption rate increased with the presence of (NH4 )2 SO4 . But excessively enriched (NH4 )2 SO4 may improve ionic strength, affecting the absorption capacity after desorption, or even caus-
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ing crystallization blockage. Consequently, (NH4 )2 SO4 can be allowed in desorption solution, as long as the content is limited. (4) Whether there was sound wave or not, ammonia escape increased rapidly. Without sound wave, ammonia escape increased from 0.000933 mol at 40 ◦ C to 0.01079 mol at 70 ◦ C in 25 min. Therefore, ammonia escape should be considered while improving desorption efficiency of CO2 through temperature. However, the enhancement in CO2 desorption was much higher than the increase in NH3 escape under sound wave. NH3 escape caused by coupling sound wave in the process of enhancing CO2 desorption is limited. Acknowledgements The authors are highly thankful for the financial supports of the Fundamental Research Funds for the Central Universities of North China Electric Power University (2014ZD39, 2016 XS113). References An, C.Y., Bai, H., 1999. Comparison of ammonia and monoethanolamine solvents to reduce CO2 greenhouse gas emissions. Sci. Total Environ. 228, 121–133. And, H.B., An, C.Y., 1997. Removal of CO2 greenhouse gas by ammonia scrubbing. Ind. Eng. Chem. Res. 36, 2490–2493. Chen, H., Dou, B., Song, Y., Xu, Y., Wang, X., Zhang, Y., Du, X., Wang, C., Zhang, X., Tan, C., 2012. Studies on absorption and regeneration for CO2 capture by aqueous ammonia. Int. J. Greenh. Gas Control 6, 171–178. Ciferno, J., Dipietro, P., Tarka, T., 2005. An Economic Scoping Study for CO2 Capture Using Aqueous Ammonia. Final Report. Corti, A., Lombardi, L., 2004. Reduction of carbon dioxide emissions from a SCGT/CC by ammonia solution absorption—preliminary results. Int. J. Thermodyn. 7. Davison, J., 2007. Performance and costs of power plants with capture and storage of CO2 . Energy 32, 1163–1176. Fang, L., Wang, S., Xi, Z., Sun, X., Chen, C., 2009. Study on ammonium bicarbonate decomposition after CO2 sequestration by ammonia method. Huanjing Kexue Xuebao 29, 1886–1890. Han, K., Chi, K.A., Man, S.L., Chang, H.R., Kim, J.Y., Chun, H.D., 2013. Current status and challenges of the ammonia-based CO2 capture technologies toward commercialization. Int. J. Greenh. Gas Control 14, 270–281. Henglein, A., 1987. Sonochemistry: historical developments and modern aspects. Ultrasonics 25, 6–16. Hui, X.U., Zhang, S.T., Wang, W.Z., Tong, S.U., 2009. Desorption of SO2 from sodium alkali solution by ultrasonic. Meitan Xuebao/J. China Coal Soc. 34, 542–545. Laugier, F., Andriantsiferana, C., Wilhelm, A.M., Delmas, H., 2008. Ultrasound in gas–liquid systems: effects on solubility and mass transfer. Ultrason. Sonochem. 15, 965–972. Lei, L., Ning, Z., Wei, W., Sun, Y., 2013. A review of research progress on CO2 capture, storage, and utilization in Chinese Academy of Sciences. Fuel 108, 112–130. Lekhal, A., Chaudhari, R.V., Wilhelm, A.M., Delmas, H., 1997. Gas–liquid mass transfer in gas–liquid–liquid dispersions. Chem. Eng. Sci. 52, 4069–4077. Liang, Z.W., Rongwong, W., Liu, H.L., Fu, K.Y., Gao, H.X., Cao, F., Zhang, R., Sema, T., Henni, A., Sumon, K., Nath, D., Gelowitz, D., Srisang, W., Saiwan, C., Benamor, A., Al-Marri, M., Shi, H.C., Supap, T., Chan, C., Zhou, Q., Abu-Zahra, M., Wilson, M., Olson, W., Idem, R., Tontiwachwuthikul, P., 2015. Recent progress and new developments in post-combustion carbon-capture technology with amine based solvents. Int. J. Greenh. Gas Control 40, 26–54. Liang, Z., Idem, R., Tontiwachwuthikul, P., Yu, F., Liu, H., Rongwong, W., 2016a. Experimental study on the solvent regeneration of a CO2 -loaded MEA solution using single and hybrid solid acid catalysts. AIChE J. 62, 753–765. Liang, Z.W., Idem, R., Tontiwachwuthikul, P., Yu, F.H., Liu, H.L., Rongwong, W., 2016b. Experimental study on the solvent regeneration of a CO2 -loaded MEA solution using single and hybrid solid acid catalysts. AIChE J. 62, 753–765.
Liu, F., Wang, S., Chen, C., Xuchang, X.U., 2009. Research progress of CO2 capture by using ammonia from flue gas of power plant. J. Chem. Ind. Eng. Soc. China 60, 269–278. Luo, X., Fu, K.Y., Yang, Z., Gao, H.X., Rongvvong, W., Liang, Z.W., Tontiwach-Wuthikult, P., 2015. Experimental studies of reboiler heat duty for CO2 desorption from triethylenetetramine (TETA) and triethylenetetramine (TETA) plus N-methyldiethanolamine (MDEA). Ind. Eng. Chem. Res. 54, 8554–8560. Ma, Sun, Zhao, S., Fang, Y., Han, Y., Liang, W., Pizhao, J., 2011. Experimental and mechanism research on CO2 capture from simulating flue gas using ammonia solution. Acta Chim. Sin. 69, 1469–1474. Ma, ShuangChen, Wang, MengXuan, Han, TingTing, Chen, WeiZhong, Lu, DongLi, 2012. Research on desorption and regeneration of simulated decarbonization solution in the process of CO2 capture using ammonia method. Sci. China Technol. Sci. 55, 3411–3418. Ma, S., Wang, M., Han, T., Song, H., Zang, B., Lu, D., Chen, W., 2013. Kinetic experimental study on desorption of decarbonization solution using ammonia method. Chem. Eng. J. 217, 22–27. Ma, S., Chen, G., Guo, M., Zhao, L., Han, T., Zhu, S., 2014. Path analysis on CO2 resource utilization based on carbon capture using ammonia method in coal-fired power plants. Renew. Sustain. Energy Rev. 37, 687–697. Ma, S., Chen, G., Han, T., Zhu, S., Yang, J., 2015. Experimental study on the effect of Ni(II) additive on ammonia escape in CO2 capture using ammonia solution. Int. J. Greenh. Gas Control 37, 249–255. Macfarlane, J.W., Scott, T.B., 2012. Reduction of carbon dioxide on jet spray formed titanium dioxide surfaces. J. Hazard. Mater. 211–212, 247–254. Mason, T.J., 1991. Industrial sonochemistry: potential and practicality. Meeting of European Society of Sonochemistry, 192–196. Mason, T.J., 1992. Current Trends in Sonochemistry, Sonochemistry Workshop for French Industrialists. Mason, T.J., 2003. Sonochemistry and sonoprocessing: the link, the trends and (probably) the future. Ultrason. Sonochem. 10, 175–179. Mondal, M.K., Balsora, H.K., Varshney, P., 2012. Progress and trends in CO2 capture/separation technologies: a review. Energy 46, 431–441. Monnier, H., Wilhelm, A.M., Delmas, H., 1999. The influence of ultrasound on micromixing in a semi-batch reactor. Chem. Eng. Sci. 54, 2953–2961. Pandit, A.B., Kumar, A., Gogate, P.R., 2004. Gas–liquid mass transfer studies in sonochemical reactors. Ind. Eng. Chem. Res. 43, 1812–1819. Qin, F., Wang, S., Hartono, A., Svendsen, H.F., Chen, C., 2010. Kinetics of CO2 absorption in aqueous ammonia solution. Int. J. Greenh. Gas Control 4, 729–738. Ratoarinoro, N., Wilhelm, A.M., Berlan, J., Delmas, H., 1992. Effects of ultrasound emitter type and power on a heterogeneous reaction. Chem. Eng. J. 50, 27–31. Resnik, K.P., Yeh, J.T., Pennline, H.W., 2004. Aqua ammonia process for simultaneous removal of CO2 , SO2 and NOx . Int. J. Environ. Technol. Manag. 4, 89–104. Resnik, K.P., Garber, W., Hreda, D.C., Yeh, J.T., Pennline, H.W., Resnik, K.P., Garber, W., Hreda, D.C., Yeh, J.T., Pennline, H.W., 2006. A Parametric Study for Regenerative Ammonia-Based Scrubbing for the Capture of CO2 . Sochard, S., Wilhelm, A.M., Delmas, H., 1998. Gas–vapour bubble dynamics and homogeneous sonochemistry. Chem. Eng. Sci. 53, 239–254. Wang, Y., 2001. Treatment of ammonia nitrogen wastewater by ultrasonic stripping. Technigues & Equipment for Enviro.poll.cont. Xiao-Ming, X.U., Wang, Y.L., Yan, L.I., 2006. Experimental investigation of processing conditions for treatment wastewater containing ammonia nitrogen with ultrasonic stripping. J. Lanzhou Univ. Technol. 32, 67–69. Xu, H., Meek, T.T., Han, Q., 2007. Effects of ultrasonic field and vacuum on degassing of molten aluminum alloy. Mater. Lett. 61, 1246–1250. Yanagida, H., 2008. The effect of dissolve gas concentration in the initial growth stage of multi cavitation bubbles: differences between vacuum degassing and ultrasound degassing. Ultrason. Sonochem. 15, 492–496. Yeh, J.T., Resnik, K.P., Rygle, K., Pennline, H.W., 2005. Semi-batch absorption and regeneration studies for CO2 capture by aqueous ammonia. Fuel Process. Technol. 86, 1533–1546. Zeng, Q., Guo, Y., Niu, Z., Lin, W., 2011. Mass transfer performance of CO2 absorption into aqueous ammonia in a packed column. CIESC J. 62, 146–150.