Thermodynamic and Kinetic Study of CO2 Capture with Calcium

Article pubs.acs.org/IECR

Thermodynamic and Kinetic Study of CO2 Capture with Calcium Based Sorbents: Experiments and Modeling Ehsan Mostafavi, Mohammad Hashem Sedghkerdar, and Nader Mahinpey* Department of Chemical and Petroleum Engineering, Schulich School of Engineering, University of Calgary, Calgary, AB, Canada ABSTRACT: The steam gasification of biomass in the presence of calcium oxide offers a viable route for the dual purpose of hydrogen production and carbon dioxide (CO2) capture. Although previous studies have dealt with experimental and intrinsic rate constants of carbonation and calcination of calcium looping cycles, the data has not been compared with thermodynamic or kinetic simulation. In this study, the thermodynamic and kinetic simulation of the CO2 capture process using two calcium-based sorbents (i.e., Imasco dolomite and Cadomin limestone) have been studied using Aspen Plus software. The thermodynamic simulation was able to predict the overall trend of the CO2 adsorption on dolomite and limestone. However, a kinetic model was also applied to achieve a more accurate analysis. The results show good agreement between the modeling and the experimental data obtained using a thermogravimetric analyzer (TGA). A shift in the reaction mechanism was observed with respect to temperature. The experimental data and kinetic model illustrated that the maximum conversion occurred at 650 °C.

1. INTRODUCTION Many studies have been conducted on practical methods for capturing carbon dioxide (CO2) from flue gases of power and chemical plants that produce energy from carbon neutral biomass; and, these techniques can result in the prevention of CO2 entering the atmosphere, leading to a cleaner atmosphere.1 Hydrogen is a clean fuel that can be produced from solid fuels using gasification processes. CO2 removal techniques enhance the gasification and reforming reactions for increased hydrogen production. Much work has been done on the capture of CO2 from synthesis gas (syngas) in order to produce higher amounts of hydrogen using solid sorbents rather than solvents (e.g., amines).2 These sorbents range from zeolites to calcium oxide (CaO) based materials, with different sorbents used for different process conditions. Among the sorbents used to capture CO2, CaO-based substances have attracted a great deal of attention, due to their abundance and resistivity to high temperatures.3,4 These types of sorbents are effective for high CO2 capture capacity and can withstand temperatures from 550 to 750 °C,2 which is the optimal temperature range, especially for the steam gasification of coal and biomass. Since the temperature is mainly dictated by the gasification process, the choice of sorbent is restricted to materials that can withstand high temperatures (up to 900 °C) and remain active after many cycles of capture and release. Therefore, resistivity to abrasion, attrition and sintering are key features in an appropriate sorbent for utilization in calcinationcarbonation cycles.5 It is well-known that the carbonation reaction is comprised of two different steps, namely the kinetic and diffusion control regimes. However, the reaction does not reach complete conversion of CaO, mainly due to diffusion through the product layer.6 There are three elements to the kinetic rate equation of gas−solid reactions: (i) the model for the shrinkage or growth of the solid particles, (ii) the pre-exponential factor and activation energy, and (iii) the reaction order. The fast initial stage has only been studied by a few researchers. © 2013 American Chemical Society

Kunii and Levenspiel developed the unreacted core model, which is also known as the shrinking core model.7 Contrary to a very simple continuous model that assumes a rapid diffusion compared to the chemical reaction, the shrinking core model is based on the concept that the reaction zone progresses from the surface into the particle. This model was improved one step further by Szekely et al.8 The resulting model (i.e., the grain model) incorporates the assumption of many grains inside the particle and applies the shrinking core model to each grain around its core.8 This method better illustrates the modeling side of lime carbonation. Key work in this research area was started by Bhatia and Perlmutter.9 They conducted their experiments in a thermogravimetric analyzer (TGA). They observed 70−80% conversion of CaO and reported a value of about zero for the activation energy in the narrow temperature range of 800 to 850 °C and with CO2 fractions of 0−10%. They proposed a random pore model and related the reaction to the internal pore structure parameter, which is a function of surface area, porosity, and total pore size per unit volume.9 A more recent work by Lee mainly focused on modeling with the activation energy ranging from 72 kJ/mol for pure kinetics to 189 kJ/mol for pure diffusion regimes.6 Lee also suggested an apparent reaction rate for the carbonation of lime.6 The main drawback of this work is the lack of a solid physical structural model behind the derivation of the rate equations. The reaction order of the rate equation should also be determined. Bhatia and Perlmutter found a first-order reaction with respect to CO2 partial pressures from 0 to 10 kPa,9 whereas Kyaw et al. fitted a zero-order reaction to the kinetic data for high CO2 partial pressures.10 Sun et al. were the first researchers to find a shift from 1 to zero in the reaction rate order at the CO2 partial pressure of 10 kPa.11 Received: August 15, 2012 Accepted: March 4, 2013 Published: March 4, 2013 4725

dx.doi.org/10.1021/ie400297s | Ind. Eng. Chem. Res. 2013, 52, 4725−4733

Industrial & Engineering Chemistry Research

Article

CO2 was used in all experiments to eliminate external films around the particles and remove the associated mass transfer resistance (maximum allowable flow rate through the TGA is 200 mL/min). The TGA experimental program consisted of the following steps: (1) Heating: Pure CO2 was initially fed to the TGA, preventing calcium carbonate (CaCO3) decomposition during heating to 850 °C at 50 °C/min in the atmospheric TGA system to mitigate the influence of calcination heating rates, as mentioned by Sun et al.11 This method also resulted in having complete calcination in the next stage. (2) Isothermal at 850 °C: The moment the calcination temperature was reached, the reaction gas was switched to N2. The temperature was maintained at 850 °C for 20 min to ensure completion of the calcination. (3) Cooling down: The sample was cooled down at a rate of 30 °C/min to the desired carbonation temperature (between 450 and 750 °C). (4) Extra isothermal: To ensure that the temperature was exactly controlled at the desired value (450−750 °C), the sample was kept at this temperature for an additional 10 min. This also helped to reduce the changes in temperature from the heat released by carbonation in the next stage. (5) Isothermal carbonation: The inert gas was replaced by CO2 or CO2/N2 mixtures with the specified concentrations to initiate the CaO−CO2 reaction. The temperature remained at the required isotherm for 20 min by controlling the heater power and with the aid of the purge gas stream. To minimize the adverse effect of the drag force caused by switching the gases, both the inert gas and reaction gas (CO2) were set at 200 mL/min. The apparent change in the sample’s mass was in the order of 0.1 mg.

Sun et al. also tested the effects of wide ranges of total pressure, CO2 partial pressure, and temperature on the intrinsic reaction rate.11 By definition, this kind of rate refers to the maximum slope of the conversion curve versus time right after the reaction starts. Therefore, this reaction rate is only associated with the pure kinetic stage, where diffusion has no tangible effect. Their consideration of the first stage was reasonable, because when diffusion plays a significant role, equilibrium can rarely be reached, due to three major resistances to equilibrium: pore diffusion, intraparticle diffusion, and surface resistance. For design purposes, the intrinsic rate reaction was sufficient. However, Sun et al. did not perform simulations or validations to match their experimental data and did not report any optimal conditions.11 This study investigated the influences of early calcination of magnesium carbonate (MgCO3) on surface area and pore size distribution, which have not been addressed in the literature. The objectives of this work were the study of the kinetics of the dolomite−CO2 reaction, determination of the optimal temperature, investigation of the effect of magnesium oxide (MgO), and evaluation of the thermodynamic equilibrium approach versus the kinetic model. Two calcium-based sorbents (i.e., Imasco dolomite and Cadomin limestone) were used in the experiments. This study also looks at the gap in the literature on the comparison of experimental data and thermodynamic and kinetic simulation.

2. EXPERIMENTAL AND SIMULATION DETAILS 2.1. TGA Measurements. All of the experiments were conducted with an atmospheric Perkin-Elmer STA6000 TGA system, as a TGA is one of the recommended apparatuses for the determination of the kinetic parameters of gas−solid reactions. This instrument was used to measure reaction rate parameters, with CO2 partial pressures and temperatures varying from 0 to 1 bar and 450 to 750 °C, respectively. Gases flowed from the bottom to the top. This unit included a balance with a sensitivity of 1 μg, a reactor chamber, and a sample pan. A schematic is provided in Figure 1.

Carbonation/calcination CaO + CO2 ↔ CaCO3

X(CaO conversion) =

(1)

(mCaO(t ) − mCaO(0))/44 mCaO(0) × purity/56

(2)

where 44 and 56 are the molecular weights of CO2 and CaO in grams per mole. Experiments were conducted on samples of 25−27 mg with an average particle size of 1.5 mm. The particle size was not reduced, in order to get a better understanding of what would occur with the same size of sorbent particle in pilot conditions. The elemental analyses of the dolomite and Cadomin limestone were performed using an energy-dispersive X-ray spectroscopy (EDX) analyzer. Table 1 shows the sorbents’ compositions. 2.2. BET Tests. The Micromeritics ASAP 2020 BET machine was used for the surface analysis. Samples of 200− 300 mg were taken from dolomite and Cadomin limestone, and the calcined dolomite and Cadomin were tested to ensure

Figure 1. Schematic of the thermogravimetric analyzers used: the Perkin-Elmer atmospheric thermogravimetric analyzer system.

Pure grade CO2 and nitrogen gas (N2) and CO2 mixtures, with CO2 concentrations of 50%, 35.3%, and 20%, were used to determine the influence of CO2 partial pressure on the kinetics of the reaction. A flow rate of 200 mL/min for the inert gas and Table 1. Chemical Analyses of the Sorbents sorbent

SiO2

Al2O3

Fe2O3

MgO

CaO

Na2O

K2O

LOI

Imasco dolomite Cadomin limestone

1.23 1.58

0.49 0.82

1.5 1.03

22.52 1.34

36.97 54.30

0.28 0.40

0.34 0.31

36.67 40.22

4726



Article

Figure 2. Schematic of the Aspen flow sheet. The key unit is the carbonator shown in the form of a horizontal rectangle (plug flow reactor). The whole flowsheet simulates a CO2 capture looping cycle (which is not the case here), and a Gibbs reactor simulates the calcination part.

Figure 3. Conversion of CaO for calcined dolomite and Cadomin reaction with pure CO2 against time at 550 °C.


acceptable precision in the measurements of the surface area and other surface properties. Initially, the samples tubes were completely dried in an oven at 130 °C for 15 min. They were weighed before and after the drying step. The sample tubes were then placed in the BET machine. The samples were degassed at 150 °C under vacuum for 2 h. Each specimen was again weighed after the degassing stage. Finally, Brunauer−Emmett−Teller (BET) and Barrett−

Joyner−Halenda (BJH) tests were conducted for 8 h using liquid nitrogen. 2.3. Simulation Assumptions. The ideal equation of state was chosen based on the low-pressure and high-temperature conditions in the simulations. Due to a high gas flow rate and rather small solid sample, the reaction proceeded with no volume change; therefore, a plug flow reactor (PFR), which 4727



Article


Figure 6. (a) Pore size distribution for calcined dolomite and Cadomin at 850 °C. (b) Effect of calcination temperature on pore size distribution for raw dolomite and calcined dolomite at two different temperatures.

the Aspen Plus flow sheet is shown in Figure 2. The main focus of the simulation was the PFR, which is labeled as the carbonator in this figure. While keeping all the parameters constant, the PFR was replaced with a Gibbs reactor, which was used to model the carbonation process as a thermodynamic equilibrium. The Gibbs reactor minimizes the Gibbs free energy of all the reactants and products and assumes that the reaction time or

considers only the axial variation, acted as a differential packedbed reactor. Stoichiometric ratios of CO2 gas and dolomite as a solid were introduced to the reactor. The carbonation−calcination reaction was defined as a reversible reaction with the kinetic parameter extracted from the TGA experiments. Sensitivity analyses were performed at different temperatures. The effect of reaction time (residence time) was also studied. A schematic of 4728



Article

Figure 7. Reaction order plot for calcined dolomite at two different temperatures. Partial pressure varies from 0.2 to 1 atm. 5% error bars are shown on the data points.

calcined sorbents. The results indicated that dolomite and Cadomin had surface areas of 33.64 and 13.84 m2/g, respectively, and average pore sizes of 28.1766 and 34.2830 nm, respectively. It was assumed that the surface area ratio of the CaO portion to the MgO portion was equal to their molar volumetric ratio.11 Hence, the active surface area could be calculated considering the cube edge lengths12 for CaO and MgO, which are 0.48 and 0.42 nm, respectively. Therefore, the volumetric ratio was 0.48/ 0.42.3 The other factor that is also needed to be taken into account was the CaO fraction in the sorbents, which is measured as a CaO to MgO molar ratio, i.e., 1.17. The active surface areas were 21.41 and 13.56 m2/g for the calcined dolomite and Cadomin, respectively. The following expression illustrates the calculation method used to obtain the active surface area:

temperature is large enough that equilibrium can be reached. The comparison of the two approaches is explained in detail in the Results and Discussion section.

3. RESULTS AND DISCUSSION 3.1. Measurements Using Thermogravimetric and Surface Properties Analyses. As observed in Figures 3−5, the capacity of Cadomin in capturing CO2 at higher temperatures was greater than that of dolomite. With increasing temperature, the differences between the intrinsic reaction rates (initial slopes of the curves) were more noticeable. The ultimate conversion was higher for dolomite at 550 °C, while this value was higher for Cadomin at 600 and 675 °C. The carbonation reaction rate and conversion of CaO-based sorbents involves complex interactions between various phenomena, such as external diffusion, concentration of active sites, diffusion through the product layer, surface area, and the interrelationships of each factor with temperature. Among these parameters, external diffusion was the same for Cadomin and dolomite, as the conditions were identical in the gas phase. With respect to the initial reaction rate, the carbonation reaction rate for calcined Cadomin at all temperatures was higher than that of dolomite, due to excessive CaO active sites, which facilitated the access of CO2 molecules to the CaO molecules. Therefore, the intrinsic reaction rate for Cadomin was higher than that of dolomite. As the reaction progressed, a product layer formed around the sorbent particles. The CO2 diffusion through this layer played a significant role in the carbonation reaction. The growth of the product layer for Cadomin was faster than that of dolomite at the beginning of the reaction, due to the higher rate of reaction (Figures 3−5). Since Knudsen diffusion is proportional to the square root of absolute temperature, the diffusion through the product layer increased as the temperature elevated above 550 °C. Due to higher diffusion rate into the pores, Cadomin captured more CO2 than dolomite resulting in a higher ultimate conversion for Cadomin at 600 and 675 °C. A major difference was observed in the surface structures of dolomite and Cadomin, which may have been due to greater MgCO3 degradation at 660 °C, resulting in more pores on the surface of dolomite. This phenomenon was tested using the BET method, in order to measure the surface areas of both

active surface area = molar ratio of active material × volumetric ratio × total surface area

(3)

Figure 6 presents the pore size distribution of the two sorbents that were extracted from the BJH tests. The pore size distribution suggests that dolomite had more mesopores (pores with diameters of less than 50 nm) and fewer macropores. Although Cadomin had a higher CaO content, dolomite had the advantage of smaller pores and a higher active surface area. The sums of CaO and MgO in the composition of the two samples were approximately the same. A BET test (as shown in Figure 6) was carried out on dolomite that had already been calcined at 700 °C (slightly beyond the decomposition point of MgCO3). The surface area was 3.55 m2/g, which shows an increase of 1 order of magnitude. Figure 6 depicts the ratio of pore volume to pore diameter versus the pore diameter for different calcination temperatures. This figure shows the early formation of 10 nm pores at 700 °C, due to the decomposition of MgCO3 to MgO. This comparison also supports the fact that, after calcination, due to an earlier release of CO2 by MgCO3 molecules, there was more surface area available for calcium carbonate (CaCO3) to be calcined. Therefore, at temperatures below 600 °C, dolomite exhibited better performance, particularly with respect to the ultimate conversion (CO2 capture capacity). Cadomin was, nonetheless, 4729



Article

Figure 8. (a) Arrhenius plot for CaO−CO2 reaction for dolomite at 1 atm partial pressure of CO2 (550−625 °C). 1% error bars are shown on the data points. (b) Arrhenius plot for CaO−CO2 reaction for dolomite at 1 atm partial pressure of CO2 (650−725 °C). 1% error bars are shown on the data points.

more capable of adsorbing CO2 at higher temperatures, due to better gas diffusion into the pores and a higher amount of CaO at the surface. To get a better understanding of the effect of calcinations on the surface properties, the surface area of the raw sample were also measured using the BET method. The specific areas of dolomite and Cadomin were 0.16 and 0.48 m2/g, respectively. According to eq 4, knowing that the reaction is of first-order, there should be a trade-off between the forward and backward reactions, resulting in an optimal temperature for the overall reaction rate: R=

dX = 56ks(PCO2 − PCO2,equil)n S dt(1 − X )

Taking the natural logarithm from the both sides at the initial time, eq 4 becomes11 ⎛ 56ks ⎞ ⎟ + n ln(PCO2 − PCO2,equil) + ln S0 ln r0 = ln⎜ ⎝ 3 ⎠

where R0 = 3r0 and is defined as the initial reaction rate based on the grain model under kinetic control.11 Equation 6 is a line with the slope of n with respect to the partial pressure driving force (the difference between the CO2 partial pressure and the equilibrium pressure on the surface of the sorbent). As shown in Figure 7, the order of the reaction is estimated to be approximately 1. The slope is 0.783 at 650 °C and 1.542 at 700 °C. In contrast with the work done by Sun et al.,11 no shift in the reaction order was observed up to 1 atm CO2 partial pressure.

(4)

where 56 is the molar weight of CaO in grams per mole and PCO2,equil (atm) is obtained from13 (−8308/ T + 7.079)

PCO2,equil = 10

(6)

⎛ 56k 0S0 ⎞ E ⎟− ln r0 = ln⎜ + n ln(PCO2 − PCO2,equil) ⎝ 3 ⎠ R gT

(5) 4730

(7)



Article

Figure 8a and b indicate the temperature dependence of the CaO−CO2 reaction according to eq 6. The linear regression was done with 95% confidence limit. The temperature interval was divided, because it was impossible to have the whole temperature range fitted to a line with an acceptable regression factor. Figures 8a and b suggest an abrupt change in the sign of the activation energy at 650 °C. This turning point implies a change in the reaction mechanism. From the first temperature interval (Figure 8a), the activation energy was 51.70 kJ/mol; whereas, a value of −26.70 kJ/mol was estimated in the second interval (Figure 8b). The equilibrium and reaction constants have been lumped into this apparent activation energy. For temperatures higher than 650 °C, the reaction could be considered as a barrierless reaction, for which any increase in the temperature resulted in lowering the reaction rate. Kinetic measurements were also done for low temperatures (i.e., 450 and 500 °C). These two points deviated from the linear trend; therefore, they were eliminated from activation energy calculations in one case. The exclusion of these points as the lower limit resulted in an activation energy of 4.47 kJ/mol. This difference may be due to the fitting method or to measurement errors at low temperatures. Sun et al.11 pointed out the same issue with low temperatures. Table 2 summarizes the reaction parameters for the two separate temperature ranges. Table 2. Kinetic Parameters for Dolomite Carbonation Reaction ⎛ E ⎞ ⎟⎟ ks = k 0 exp⎜⎜− ⎝ R gT ⎠

550−625 °C

650−725 °C

k0 (mol/m2 s) E (kJ/mol)

7.51 × 10−3 51.77

2.45 × 10−7 −25.71

Figure 10. (a) Reaction rate of dolomite versus temperature in the presence of pure CO2. Comparison of the predicted values by the kinetic model and the experimental data. 5% error bars are shown on the data points. (b) Residual plot of reaction rate of dolomite versus temperature.

analysis for the reaction rate, with the residuals calculated from Figure 10a. This plot shows a wide scattering of points, which are evenly spread above and below zero. There was no apparent pattern between the residuals and temperature. Therefore, the proposed kinetic model is appropriate for the carbonation of calcined dolomite. Figure 11, which was drawn based on eq 4 using the reaction parameters shown in Table 2, confirms this trend. Indeed, the reaction rate expression implies that a maximum should

For dolomite, the maximum conversion of CO2 occurred at 675 °C, whereas the maximum reaction rate took place at 650 °C, as shown in Figures 9 and 10. As expected, the reversible nature of the carbonation reaction required an optimal temperature at which the overall reaction rate reaches its maximum value (Figure 10a). Figure 10b presents the residual

Figure 9. Final conversion of CaO for the carbonation calcined dolomite versus temperature in the presence of pure CO2. 4731



Article

Figure 11. Final conversion of CaO for dolomite versus temperature in the presence of pure CO2, predictions by the kinetic and thermodynamic approaches.

650 °C. The reaction rate parameters were determined based on the grain model and were in a good agreement with the previous works. Maximum ultimate conversion was achieved at 675 °C, whereas the maximum reaction rate occurred at 650 °C. The kinetic and equilibrium approaches were employed to simulate the capture of CO2 on dolomite as a sorbent at different temperatures. Although the kinetic model was more useful for design purposes, the thermodynamic equilibrium model predicted the upper bound of the carbonation reaction relatively well. Future work is required to eliminate the effect of diffusion from the activation energy calculation using very fine particles, so that kinetics parameters can be calculated solely in the kinetic regime.

reasonably exist. This is logical, because the exothermic carbonation reaction is limited by the thermodynamic equilibrium. To ensure that the experiment results were accurate, similar experiments were also conducted on a Cadomin sample. The variations of the ultimate conversion and the reaction rate versus temperature peaked at 675 °C for Cadomin, which confirms the fact that there should be an optimal temperature for a typical CaO−CO2 reaction. 3.2. Thermodynamic Predictions of Carbon Capture Capacity Using Aspen Plus. A sensitivity analysis (as illustrated in Figure 11) was carried out with Aspen Plus simulation software: the results predicted an abrupt decrease of CO2 adsorption at 790 °C. In other words, high temperatures favored the calcination reaction. Figure 11 shows that both models were similar in their predictions of the overall behavior of the carbonation reaction. The kinetic model approached equilibrium in the limit at sufficiently high reaction times (i.e., 1000 s). One main difference between the thermodynamic predictions by Aspen Plus and the conversion calculated from the experimental data was the point at which the conversion drastically decreased to zero. This phenomenon was likely due to the assumptions made in the grain model for the calculation of the reaction parameters. Contrary to Figure 11, conversion in practice never reaches one, because there are internal points that are never touched by the gas. In other words, some sorbent particles remain intact and unreacted. Inaccessible points may be minimized using very fine particle sizes with diameters in micrometers, which will be studied as a future work.

■

AUTHOR INFORMATION

Corresponding Author

*Mailing address: Department of Chemical and Petroleum Engineering, Schulich School of Engineering, University of Calgary, 2500 University Drive NW, Calgary, AB, Canada T2N 1N4. Phone: 403-210-6503. Fax: 403-284-4852. E-mail: [email protected]. Notes

The authors declare no competing financial interest.

■ ■

ACKNOWLEDGMENTS Financial assistance from Carbon Management Canada Inc. (CMC-NCE) is gratefully acknowledged. REFERENCES

(1) Florin, N. H.; Harris, A. T. Enhanced hydrogen production from biomass with in situ carbon dioxide. Chem. Eng. Sci. 2008, 63, 287− 316. (2) Florin, N. H.; Harris, A. T. Hydrogen production from biomass coupled with carbon dioxide capture: The implications of thermodynamic equilibrium. Int. J. Hydrogen Energy 2007, 32, 4119−4134. (3) Silaban, A.; Harrison, P. High temperature capture of carbon dioxide: characteristics of the reversible reaction between CaO (s) and CO2 (g). Chem. Eng. Commun. 1995, 137, 177−190. (4) Abanades, J. C.; Anthony, E. J.; Alvarez, D.; Lu, D.; Salvador, C. Capture of CO2 from combustion gases in a fluidized bed of CaO. A.I.Ch.E. J. 2004, 50, 1614−1622.

4. CONCLUSIONS The effect of magnesium oxide on the surface properties and kinetics of dolomite were studied in this research. The role of magnesium carbonate in the early calcination was studied using BET and BJH tests. For dolomite, magnesium carbonate provided a higher surface area than Cadomin. The order of reaction was estimated to be one with respect to CO2 partial pressure. No shift in the reaction order was observed for CO2 partial pressures up to 1 atm. A significant change in the reaction mechanism appeared with respect to temperature at 4732



Article

(5) Sun, P.; Grace, J. R.; Lim, C. J.; Anthony, E. J. The Effect of CaO Sintering on Cyclic CO2 Capture in Energy Systems. A.I.Ch.E. J. 2007, 53, 2432−2442. (6) Lee, D. K. An apparent kinetic model for the carbonation of calcium oxide by carbon dioxide. Chem. Eng. J. 2004, 100, 71−77. (7) Kunii, D.; Levenspiel, O. Fluidization Engineering; Wiley: New York, 1969; pp 480−489. (8) Szekely, J.; Evans, J. W.; Sohn, H. Y. Gas Solid Reactions; Academic Press: London, 1976. (9) Bhatia, S. K.; Perlmutter, D. D. Effect of the product layer on kinetics of the CO2lime reaction. A.I.Ch.E. J. 1983, 29 (1), 79−86. (10) Kyaw, K.; Kanamori, M.; Matsuda, H.; Hansatani, M. Study of carbonation reactions of Ca−Mg oxides for high temperature energy storage and heat transformation. J. Chem. Eng. Jpn. 1996, 29 (1), 112− 118. (11) Sun, P.; Grace, J. R.; Lim, C. J.; Anthony, E. J. Determination of intrinsic rate constants of the CaO−CO2 reaction. Chem. Eng. Sci. 2008, 63, 47−56. (12) Boynton, R. S. Chemistry and Technology of Lime and Limestone; Wiley: New York, 1979. (13) Baker, E. H. The calcium oxide-carbon dioxide system in the pressure range 1−300 atm. J. Chem. Soc. 1962, 464−470.

4733


Thermodynamic and Kinetic Study of CO2 Capture with Calcium

Recommend Documents