- Email: [email protected]
Some examples of the contribution of applied thermodynamics to Post-Combustion CO2-Capture technology
Accepted Manuscript Title: Some Examples of the Contribution of Applied Thermodynamics to Post-Combustion CO2 -Capture Technology Author: Paul M. Mathias PII: DOI: Reference:
S0378-3812(13)00511-6 http://dx.doi.org/doi:10.1016/j.fluid.2013.09.016 FLUID 9764
To appear in:
Fluid Phase Equilibria
Received date: Revised date: Accepted date:
16-7-2013 2-9-2013 5-9-2013
Please cite this article as: P.M. Mathias, Some Examples of the Contribution of Applied Thermodynamics to Post-Combustion CO2 -Capture Technology, Fluid Phase Equilibria (2013), http://dx.doi.org/10.1016/j.fluid.2013.09.016 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
cr
Paul M. Mathias Fluor Corporation 3 Polaris Way Aliso Viejo, CA 92698 [email protected]
ip t
Some Examples of the Contribution of Applied Thermodynamics to PostCombustion CO2-Capture Technology
Abstract
an
us
There is intense ongoing worldwide research to develop improved solvents and processes for CO2 capture from flue gas. The number of publications was almost 1,000 in 2011, and may be expected to exceed 10,000 by 2020 if exponential extrapolation of the number of past publications is applicable. Applied thermodynamics is a valuable tool to make sense of this vast body of research, and we present three examples of its contribution to CO2-capture process technology.
Ac ce p
te
d
M
Aqueous-ammonia processes have been proposed as energy-efficient alternatives to traditional alkanolamine process, and early proponents claimed that a significant advantage of the technology is that the CO2 heat of solution is exceptionally low, about 27 kJ/mol. A rigorous thermodynamic model with correct speciation estimated that the CO2 heat of solution is closer to about 65 kJ/mol, a number that was later confirmed by calorimetric measurements. The thermodynamic model enabled realistic analysis of the chilled-ammonia process, and these results have been supported by subsequent studies by other researchers. Further work on this subject established the rigorous and complete form of the Gibbs-Helmholtz equation, and demonstrated its value in evaluating the consistency between vapor-liquid equilibrium and calorimetric data. Theoretical and experimental studies have been used to find the best solvent for CO2 capture. Some researchers have assumed that the goal is seek solvents with high CO2 capacity and a low heat of solution. This notion was tested by inventing solvents with various properties, the only restriction being that the properties must be thermodynamically consistent. The results have provided insight into the interplay between CO2 absorption and the heat of regeneration (through the Gibbs-Helmholtz equation), and reveal subtle characteristics that may guide the development of future solvents. A promising step-out technology for CO2 capture is “CO2-binding liquids with polarityswing-assisted regeneration.” Reliable analysis and design of this complex technology requires a thermodynamic model that describes the chemical absorption (i.e., speciation) as well as vapor-liquid-liquid equilibrium. The initial thermodynamic model has enabled useful projections of process performance. The model limitations and the need for future improvements are also discussed. Keywords: CO2 capture, applied thermodynamics, process simulation, Gibbs-Helmholtz equation, heat of solution, vapor-liquid-liquid equilibrium
Mathias – Applied Thermodynamics in CO2 Capture Process Technology - Fluid Phase Equilibria - 2013
1 Page 1 of 19
1. Introduction
us
cr
ip t
Applied thermodynamics has a rich history as a foundational tool for chemical process technology. To quote from the dedication of the 1923 Lewis and Randall [1] textbook: “The fascination of a growing science lies in the work of the pioneers at the very borderland of the unknown, but to reach this frontier one must pass over well traveled roads; of these one of the safest and surest is the broad highway of thermodynamics.” Over the last 90 years, many papers have highlighted the essential role thermodynamics and physical properties have played in the engineering of chemical products and in the processes that produce them. [2,3,4,5] This paper studies the broad role applied thermodynamics is playing in the technology of CO2-capture from flue gas through three representative examples.
te
d
M
an
Applied thermodynamics plays an especially strong role in Post-Combustion CO2Capture (PCCC) process technology because energy reduction is by far the most important goal of the process design. As Adams and Davison [6] and Cousins, Wardhaugh and Feron have [7] pointed out, today’s PCCC technology is expected to reduce the thermal efficiency of a power station by about 20%, while the loss of product for the separation of CO2 from natural gas is typically 2% - a difference of one order of magnitude. Today’s process analysis is based upon computer modeling that in turn depends on property models,Error! Bookmark not defined. and hence accurate estimation of the thermodynamic properties for CO2 capture from flue gas is of the utmost importance to invent new processes and to evaluate existing ones.
Ac ce p
The CO2-capture literature is very difficult to follow because the number of papers and patents has exploded, and the claims of the authors are difficult to substantiate. According to the study by Mathias et al.,8] from a beginning in the early 90s with just a handful of papers each year, the number of yearly papers has grown exponentially, reaching almost 1,000 publications in 2011. If this exponential rate of increase continues, the number of yearly publications will exceed 10,000 before 2020! Hence it is important - and even necessary - to apply the “safe and sure” hand of applied thermodynamics to PCCC technology. The role of applied thermodynamics in chemical process technology is depicted in Figure 1. For the purposes of computer modeling, the property data are captured in a property model (center of Figure 1). The property model is typically phenomenological or semiempirical,9,10,11] but may also be totally empirical. [12] However, as we strongly emphasize in this work, it is important that the property model is thermodynamically consistent. The property model is designed to provide an accurate representation of the property data, and these data may come from experimental measurements, molecular modeling and/or estimation methods.Error! Bookmark not defined.,Error! Bookmark not defined.,Error! Bookmark not defined. The property model is used either in the forward model (process design) or in the reverse mode (product design). [13,14] The forward mode is the most common use of applied thermodynamics, but, as we highlight in this work, the reverse mode can be quite useful. Mathias – Applied Thermodynamics in CO2 Capture Process Technology - Fluid Phase Equilibria - 2013
2 Page 2 of 19
In this work, we use three selected examples to illustrate the wide role applied thermodynamics is playing in PCCC process technology.
2. Examples of Applied Thermodynamics in Post-Combustion CO2-Capture
ip t
Process Technology
us
cr
Three examples have been selected to illustrate the role of applied thermodynamics in PCCC technology. No new information is provided in the present paper. Rather, the purpose of the present work is to use existing publications to demonstrate at a high level the patterns of analyses that make applied thermodynamic a most useful tool.
an
Example 1. “What is the enthalpy of Solution?” The Gibbs-Helmholtz equation together with treatment of the chemical equilibria of the complexes and ions that form in the liquid phase enable validated thermodynamic models that are reliable and accurate for phase equilibrium as well as thermodynamic properties such as enthalpy..
M
Example 2. “What is the ‘best thermodynamic solvent’ for post-combustion CO2 capture?” Creating a series of artificial solvents whose only restriction is thermodynamic consistency enables insight into desired solvent characteristics, and may provide a rational method to invent improved solvents.
Ac ce p
te
d
Example 3. “How does thermodynamic modeling and analysis support and enable a novel CO2-capture technology?” The novel technologies being proposed for postcombustion CO2 capture involve complex chemicals and new process concepts. Applied thermodynamics provides a reliable framework to analyze, validate and improve these novel technologies, i.e., the safe and sure broad highway of thermodynamics.
2.1. Example 1: Enthalpy of Solution It is generally accepted that traditional alkanolamines absorption-stripping processes will be the first to be applied on a large scale for PCCC technology. [15] Starting about the beginning of the past decade, aqueous-ammonia processes for PCCC were proposed as energy-efficient alternatives to traditional alkanolamines absorption-stripping processes, and the main reason given by researchers was that the heat CO2 enthalpy of solution is -260 Btu/lb CO2 (-27 kJ/mol CO2). [16,17,18] Mathias, Reddy and O’Connell [19] applied a rigorous thermodynamic analysis, which included application of the GibbsHelmholtz equation and the correct chemistry model, and concluded that a more accurate enthalpy of solution is in the range of -600 to -700 Btu/lb CO2 (-61 to -72 kJ/mol CO2). Mathias et al.Error! Bookmark not defined. identified the root cause for the incorrect estimation of the enthalpy of solution. Previous researchers assumed that the only chemical reaction occurring in the regenerator is the chemical conversion of ammonium bicarbonate to ammonium carbonate:
Mathias – Applied Thermodynamics in CO2 Capture Process Technology - Fluid Phase Equilibria - 2013
3 Page 3 of 19
2NH4+ + 2HCO3- → 2NH4+ + CO32- + H2O(l) + CO2(g)
ΔHrxn ≈ 266 Btu/lb CO2
us
cr
ip t
However, several other reactions (including carbamate formation) occur simultaneously, and a model that properly treats chemical equilibrium is required. Figure 2 compares two estimation methods for the enthalpy of solution of CO2 in 8 wt% aqueous ammonia at about 38 ˚C with the calorimetric data of Qin et al. [20] The first method (labeled Thermodynamic Model) is from the rigorous thermodynamic model developed by Mathias et al.,Error! Bookmark not defined. while the second method (labeled From VLE Data of Kurz (1995)) applied the Gibbs-Helmholtz equation to the experimental vapor-liquid data Kurz et al. [21] Figure 2 is similar to Figure 7 from Reference [Error! Bookmark not defined.]. It is noted here that Reference [Error! Bookmark not defined.] was published before the data of Qin et al.Error! Bookmark not defined. were available, and thus may be considered to be a prediction of the enthalpy of solution of CO2 in aqueous ammonia in the absence of experimental data..
M
an
Mathias et al.Error! Bookmark not defined. used their thermodynamic model to analyze the chilled ammonia processError! Bookmark not defined. and concluded that, “The chilled-ammonia process is judged to be equivalent to alkanolamine-based absorption processes for LP steam consumption, but may be rendered noncompetitive because of the large refrigeration loads that are not needed in alkanolamine-based processes.” Our goal in this publication is not to make a conclusive judgment on the viability of the aqueous ammonia processes for PCCC, but rather to highlight role of applied thermodynamics in improving the objective analysis of this process technology.
te
d
Today, it appears that reliable and accurate thermodynamic models are being used to design and evaluate aqueous-ammonia processes for PCCC. For example, Zhang and Guo [22] have used a thermodynamic model to simulate the pilot-plant data of Yu, et al.,23] and report good agreement between simulation predictions and plant results. Applied thermodynamics has proved to be a sound enabling tool to model, evaluate and improve this complex process.
Ac ce p
Mathias and O’Connell [24] performed a deeper analysis of the useful Gibbs-Helmholtz (G-H) equation and presented the rigorous form:
⎛ ∂H ΔH 0 i ≡ ⎜⎜ ⎝ ∂n 0 i
⎞ ⎟⎟ − hi* ⎠ T , P , n0 j
⎛ ∂ ln f i ⎞ ⎟⎟ = R ⎜⎜ − ⎝ ∂ (1 / T ) ⎠ σ , {x 0}
V0 i T
= f − Term
P − Term
−
⎛ ∂P ⎞ ⎜⎜ ⎟⎟ ⎝ ∂ (1 / T ) ⎠ σ , {x 0}
where, ΔH 0 i is the differential enthalpy of solution, which is equal to the sum of two terms, the f-Term and the P-Term. The P-Term was unknown prior to The MathiasO’Connell publication, and hence was neglected in previous applications of the G-H equation, but it turns out that the usual approximation is fortunately valid, i.e., the P-term is insignificant for absorption in the liquid phase far from critical conditions. Mathias and O’ConnellError! Bookmark not defined. used the simplified G-H equation (with the PTerm ignored) to evaluate the consistency between vapor-liquid equilibrium (VLE) and calorimetric data for the CO2 absorption in aqueous monoethanolamine (MEA). They performed an integration using calculations from the model of Zhang, Que and Chen [25]
Mathias – Applied Thermodynamics in CO2 Capture Process Technology - Fluid Phase Equilibria - 2013
4 Page 4 of 19
ip t
at a base temperature of 40 ˚C to predict the VLE data of Jou, Mather and Otto [26] at other temperatures by using two possibilities for the CO2 enthalpy of solution, and these are shown in Figure 3. The fixed value of -85 kJ/mol CO2 is based upon the VLE data of Jou et al.Error! Bookmark not defined. and the calorimetric data of Carson, Marsh and Mather [27] and Arsis et al.,28] while the linear variation with temperature is based upon the calorimetric data of Mathonat et al. [29] and Kim and Svendsen. [30] Figure 4 indicates that a fixed value of the CO2 enthalpy of solution enables an excellent prediction of the Jou et al.Error! Bookmark not defined. at all temperatures, which implies that the Jou et al. VLE data estimate a constant value of ΔH 0 i equal to about -85 kJ/mol CO2.
an
us
cr
However, Figure 5 shows that using values of ΔH 0 i from the calorimetric measurements of Mathonat et al. [31] and Kim and Svendsen [32] do not give an accurate estimate of the Jou et al.Error! Bookmark not defined. data at high temperatures. According to the G-H thermodynamic-consistency criterion, either the high-temperature calorimetric data from Mathonat et al. [33] and Kim and Svendsen [34] or the high temperature VLE data of Jou et al.Error! Bookmark not defined. – or both sets of data – are inaccurate. Xu [35] and Xu and Rochelle [36] also concluded that enthalpy of solution of CO2 in aqueous MEA does not vary significantly with temperature. Additional high-temperature data are needed to resolve the issue.
M
This section has demonstrated the use of exact thermodynamic relationships to challenge and validate experimental data. The long-term benefit is that the thermodynamic models used for process analysis will continuously improve to become increasingly accurate and reliable.
te
d
2.2. Example 2: “Best Thermodynamic Solvent” for PCCC
Ac ce p
Optimizing PCCC processes is highly complicated because performance depends on solvent and process characteristics, and even just the solvent characteristics depend on a variety of features, such as thermodynamics, kinetics, toxicity and cost. Mathias, et al. [37] attempted to understand and rate solvent characteristics by focusing on thermodynamic properties alone, i.e., the applied-thermodynamics approach. The study began by understanding the absorption characteristics of existing solvents in terms of two criteria at the chosen standard condition of CO2 loading (mols CO2/mol solvent) of 0.15 and temperature of 40 ˚C: the absorption strength, identified by the CO2 partial pressure, and the enthalpy of solution. Figure 6 presents the properties of the seven common solvents. There appears to be a simple exponential relationship between the enthalpy of solution and the solvent strength. This relationship has been used to invent four artificial families of solvents, all based upon the MDEA (methyldiethanolamine) model published by Zhang and Chen. [38] Figure 6 shows the characteristics of the four families of solvents. The A Series are a standardized family of solvents intended to represent the seven common solvents. The three other families of solvents (H55, H65 and H75) are families of solvents where the standard enthalpy of solution has been held constant and the solvent strength varied; the naming convention is that the number following ‘H’ is the standard enthalpy of solution in kJ/mol CO2. The purpose of the four artificial families of solvents is to systematically study the variation of absorption capacity and enthalpy of solution while maintaining thermodynamic consistency, i.e., the G-H equation is strictly followed.
Mathias – Applied Thermodynamics in CO2 Capture Process Technology - Fluid Phase Equilibria - 2013
5 Page 5 of 19
ip t
Mathias et al.Error! Bookmark not defined. performed the study by using a fixed flowsheet so that the performance of the different solvents essentially resulted from the variation in thermodynamic properties alone. All performance properties were calculated as a function of a single variable, the solvent circulation rate. The work of Mathias et al.Error! Bookmark not defined. presents a detailed report of the study. Here we only present key findings that demonstrate the role of applied thermodynamics in providing insight into the “best thermodynamic solvent.”
us
cr
Perhaps the most important indicator of solvent performance is the steam consumption, here represented as the reboiler duty divided by the amount of CO2 captured. Figure 7 indicates that, for the Series A solvents, the reboiler duty increases as the magnitude of the enthalpy of solution increases. But the solvent needs to be sufficiently strong as solvent A-1 is not sufficiently strong to meet the flowsheet criterion, and thus does not appear on Figure 7. In addition, the weakest solvents (A-2 and A-3) require a relatively high solvent circulation rate.
M
an
The “intuitive conclusion” of PCCC technology is that solvents below the line of the Series A solvents are in the “target zone.” In other words, research efforts to develop advanced solvents should target those with high capacity and low (magnitude) of the enthalpy of solution. Figure 8 compares the performance of the strongest solvents (lowest CO2 partial pressure at the standard conditions). It is clear that when the absorbent is very strong, a low enthalpy of solution causes significant deterioration in solvent performance. As a comparison, Figure 8 also presents the performance of the best solvents in the study (A-4 and A-5).
te
d
Mathias et al.Error! Bookmark not defined. concluded that on a thermodynamic basis alone, the “best solvent” is one that lies along the line of the common solvents in Figure 6. If keeping the solvent circulation rate low is important, solvents A-4 and A-5 are probably optimum.
Ac ce p
More analysis is needed on this complex issue. Is some ways, the study of Mathias et al.Error! Bookmark not defined. agrees with the approach of proponents of aqueous-ammonia technology who determined that a low enthalpy of solution is preferred.Error! Bookmark not defined.,Error! Bookmark not defined.,Error! Bookmark not defined. Further, the results of Mathias et al.Error! Bookmark not defined. seem to disagree with the works of Oexmann and Kather,39] Tobiesen and Svendsen,40] and Oyenekan,41] who concluded that a higher heat of solution is often preferable. It is critically important that these studies be done for carefully defined solvent variations. Further, the study of Mathias et al.Error! Bookmark not defined. was performed for a fixed flowsheet, and it is possible that additional subtleties will be revealed by process variations, such as a higher stripper pressure. Of course, thermodynamic analysis is only one aspect of the comprehensive analysis needed for PCCC processes. Even if a solvent is judged to be excellent on the basis of thermodynamic analysis, its reaction kinetics and mass transfer may be slow, and this will result in large absorber towers high capital cost and large pressure drops that result in high blower energy costs. Or, the optimum thermodynamic solvent may be susceptible to degradation and produce toxic by-products. However, it is also clear that applied thermodynamics offers unique insight into the complex PCCC process technology, and is an important aspect of the comprehensive technology evaluation.
Mathias – Applied Thermodynamics in CO2 Capture Process Technology - Fluid Phase Equilibria - 2013
6 Page 6 of 19
2.3. Example 3: Novel PSAR Technology
ip t
Process modeling has been an important tool to evaluating PCCC processesError! Bookmark not defined. and studying and validating proposed process improvements.Error! Bookmark not defined. Here we briefly highlight the role of applied thermodynamics in evaluating and developing a novel technology: CO2-binding organic liquids with a polarity change. [42]
M
an
us
cr
Mathias et al.Error! Bookmark not defined. recently described a novel solvent regeneration method unique to CO2-binding organic liquids (CO2BOLs) and other switchable ionic liquids, which is known as PSAR (Polarity Swing Assisted regeneration) technology. The first potential advantage of the proposed technology is that the water levels are very low. One of the main reasons why the solvents with low enthalpy of solution perform poorly in Figure 8 is that low enthalpy of solution makes the stripping step more difficult, and hence larger flows of stripping steam are needed, which must be vaporized in the reboiler, and this increases the reboiler duty. [43] PSAR technology uses a solvent with minimum water levels to reduce the reboiler duty associated with water evaporation. The second advance of PSAR technology is to use a chemically inert nonpolar “antisolvent” such as hexadecane to aid in releasing CO2 from the CO2-rich CO2BOL. The advantage of PSAR technology is that the stripping step now occurs at a significantly lower temperature, which offers three primary benefits: reduced thermal degradation of the CO2BOL solvent, lower fugitive emissions, and potential for higher net power produced by the utility plant. As an example, the lower stripping temperature could enable the use of a simple let-down turbine to extract work from the steam as it is expanded to lower temperatures.
te
d
New process technologies require a wide range of analyses and evaluations. The discussion here is limited to the development of the thermodynamic model needed for quantitative process analysis through process simulation.
Ac ce p
The chemistry model developed was based upon an understanding of the fundamental chemistry as well as practical experience with electrolyte process simulation. Two complexes were proposed that result in the following two chemical equilibrium equations: 2 CO2 + 2 BOL ↔ BOLCO2+ + BOLCO2-
(1)
H2O + BOL + CO2 ↔ BOLH+ + HCO3-
(2)
Breaking out separate charges for the complex formed in Eq. 1 is actually an approximation as this complex is expected to be a single zwitterionic CO2BOL-CO2 species. The approximation was made as it is convenient to use the Born term,44] which is available in the Aspen Plus electrolyte model. Research is underway to evaluate the use of the Kirkwoog-Onsager [45] approach to model this effect, but the Born term has been retained in the present model. The thermodynamic model has enabled a quantitative description of the complex phase behavior of the CO2-H2O-BOL-AS system. Figure 9 shows the calculated CO2 partial pressures at 100 ˚C for four representative solvent compositions. The composition on the x-axis is the CO2 loading with respect to the BOL. Figure 9 shows that adding 1 mole of H2O to 1 mole of BOL significantly reduces the CO2 partial pressure, while adding 1 mole of AS (C16) to 1 mole of BOL sharply increases the CO2 partial pressure. The 1:1:1 Mathias – Applied Thermodynamics in CO2 Capture Process Technology - Fluid Phase Equilibria - 2013
7 Page 7 of 19
BOL-H2O-AS solvent has an absorption strength between those of neat BOL and 1:1 H2O:BOL. Figure 10, which presents the fraction of CO2 that is complexed, provides an explanation of the results in Figure 9. The reduction of the CO2 partial pressure is caused by increased complexation of the CO2, and conversely, the increase of the partial pressure is due to decomplexation of CO2 from the BOL.
cr
ip t
The enthalpy of solution is very important as the main goal of PCCC processes is to reduce the energy cost of CO2 capture, and this energy cost is directly related to the enthalpy of solution. Figure 11 shows the enthalpy of solution of CO2 in BOL as a function of temperature and CO2 loading. At 40°C (typical absorber temperature), the enthalpy of solution is about −82 kJ/mol at low CO2 loadings and then decreases in magnitude with CO2 loading. The model accounts for expected behavior; as the temperature increases, the magnitude of the enthalpy of solution decreases, as does the CO2 loading at which the enthalpy of solution drops.
an
us
Further details of the model and the process simulations have been given by Mathias et al.,Error! Bookmark not defined. but we note here that the key enabling tool is the thermodynamic model. The purpose of the brief discussion presented here is to identify and highlight the role of applied thermodynamics in this novel and complex PCCC technology.
3. Summary and Conclusions
d
M
90 years ago Lewis and Randall identified thermodynamics as an essential tool to evaluate and improve chemical technology. This work has used three examples from current PCCC process technology to demonstrate that applied thermodynamics is still important and even necessary for effective chemical technology.
Example 1 has shown that the rigorous relationships offered by thermodynamics challenge and validate experimental data, which improves the reliability and accuracy of thermodynamic models. The end result is stronger chemical process technology.
Ac ce p
•
te
Referring back to Figure 1, this paper has highlighted three ways in which applied thermodynamics provides a valuable contribution:
•
Example 2 offered one way in which thermodynamic analysis can provide insight into solvent performance, and hence guide research into improved solvents for PCCC.
•
Example 3 is an on-going effort. It demonstrates that applied thermodynamics can provide the same useful input to novel technology as it has provided to the mature alkanolamine process technology.
Acknowledgement The author is pleased to recognize his collaborators from PNNL (Mark Bearden, Charles Freeman, David Heldebrant, Philip Koech, Igor Kutnyakov, Feng Zheng, and Andy Zwooster), Queens University (Tamer Andrea, Philip Jessop, and Omid Nik), the University of Virginia (John P. O’Connell), and Fluor Corporation (Kash Afshar, Satish Reddy, and Arnold Smith) who were co-authors on the examples used in this work. Mathias – Applied Thermodynamics in CO2 Capture Process Technology - Fluid Phase Equilibria - 2013
8 Page 8 of 19
List of Figures Figure 1 Applied thermodynamics in chemical process technology............................... 10
ip t
Figure 2 Comparison of the estimated enthalpy of solution of CO2 in 8 wt% aqueous NH3 by two methods with the calorimetric data of Qin et al.20 The two estimation methods are described in the text. ............................................... 11
cr
Figure 3 Two possibilities for the enthalpy of solution of CO2 in aqueous MEA. Hsoln-1 is a constant value of -85 kJ/mol CO2, and Hsoln-2 is a linear fit to the data of Mathonat et al.28 and Kim and Svendsen.29 .................................................. 12
us
Figure 4 Prediction of the CO2 partial pressure in aqueous MEA using integration and a constant (-85 kJ/mol CO2) heat of solution.................................................... 13 Figure 5 Prediction of the CO2 partial pressure in aqueous MEA using integration and a linear heat of solution. See Figure 3 for details. ........................................... 13
M
an
Figure 6 Relationship between the CO2 partial pressure and the heat of solution for seven common solvents. The calculations were done at 40˚C, CO2 loading of 0.15, and a solvent strength of 7m. The solid line is an exponential correlation of the data. The open squares represent the eight artificial A Series solvents. The three vertical lines represent the artificial H55, H65 and H75 Series of solvents. ................................................................................. 14
d
Figure 7 Reboiler duty versus normalized solvent flow rate (solvent flow rate divided by rate of CO2 capture) for A Series solvents. ................................................... 15
te
Figure 8 Reboiler duty of the high capacity solvents; The solvents A8, H75-6, H65-7 and H55-7 all have low CO2 partial pressure (≈ 0.003 kPa) at the standard conditions (Figure 6). For comparison, the reboiler duties of solvents A-4 and A-5 are also presented. ................................................................................. 15
Ac ce p
Figure 9 Estimated CO2 partial pressures in BOL-H2O-AS at 100 ˚C. The relative solvent concentrations are equimolar............................................................ 16 Figure 10 Fraction of CO2 in BOL-H2O-C16 at 100 ˚C that is complexed. The relative solvent concentrations are equimolar............................................................ 16 Figure 11 Calculated enthalpy of solution of CO2 in BOL. ............................................. 17
Mathias – Applied Thermodynamics in CO2 Capture Process Technology - Fluid Phase Equilibria - 2013
9 Page 9 of 19
ip t cr us
Ac ce p
te
d
M
an
Figure 1 Applied thermodynamics in chemical process technology.
Mathias – Applied Thermodynamics in CO2 Capture Process Technology - Fluid Phase Equilibria - 2013
10 Page 10 of 19
ip t
75
cr
70
60
⎧ ∂ ln(PCO2 )⎫ Solution H CO = − R⎨ ⎬ 2 ⎩ ∂(1 / T ) ⎭ Loading
0
Thermodynamic Model From VLE Data of Kurtz (1995) Data of Qin (2011)
M
55
us
65
an
- Enthalpy of Solution (kJ/mol CO2)
80
0.2
0.4
0.6
0.8
CO2 Loading (mols CO2/mol NH3)
Ac ce p
te
d
Figure 2 Comparison of the estimated enthalpy of solution of CO2 in 8 wt% aqueous NH3 by two methods with the calorimetric data of Qin et al.Error! Bookmark not defined. The two estimation methods are described in the text.
Mathias – Applied Thermodynamics in CO2 Capture Process Technology - Fluid Phase Equilibria - 2013
11 Page 11 of 19
110 105
Mathonat (1998) Carson (2000) Kim (2007) Arcis (2011) Hsoln-1
ip t
100
Hsoln-2
cr
95
us
90
80
300
320
340
360
M
75 280
an
85
380
400
420
Temperature/ K
Ac ce p
te
d
Figure 3 Two possibilities for the enthalpy of solution of CO2 in aqueous MEA. Hsoln-1 is a constant value of -85 kJ/mol CO2, and Hsoln-2 is a linear fit to the data of Mathonat et al.Error! Bookmark not defined. and Kim and Svendsen.Error! Bookmark not defined.
Mathias – Applied Thermodynamics in CO2 Capture Process Technology - Fluid Phase Equilibria - 2013
12 Page 12 of 19
1
CO2 Loading
ip t
0.1 298.15 K
cr
313.15 K 323.15 K
0.01
353.15 K
us
373.15 K 393.15 K
0.001 0.001
0.01
0.1
an
Base Temp: 313.15K
1
423.15 K
10
100
M
CO2 Partial Pressure/ kPa
d
Figure 4 Prediction of the CO2 partial pressure in aqueous MEA using integration and a constant (85 kJ/mol CO2) heat of solution.
Ac ce p
te
1
CO2 Loading
0.1
298.15 K 313.15 K 333.15 K
0.01
353.15 K 373.15 K 393.15 K
Base Temp: 313.15 K 0.001 0.001
0.01
0.1
1
423.15 K 10
100
CO2 Partial Pressure/ kPa
Figure 5 Prediction of the CO2 partial pressure in aqueous MEA using integration and a linear heat of solution. See Figure 3 for details.
Mathias – Applied Thermodynamics in CO2 Capture Process Technology - Fluid Phase Equilibria - 2013
13 Page 13 of 19
100 10
MDEA
Open Squares are A Series
ip t
TEA
0.1
cr
1
AMP NH3
H55
H65
0.01
H75 50
60
70
PZ
MEA
an
0.001
us
CO2 PP (kPa) at α = 0.15
-2.10E-01x
y = 5.20E+05e 2 R = 9.29E-01
80
DGA
90
M
-Enthalpy of Solution (kJ/mol)
Ac ce p
te
d
Figure 6 Relationship between the CO2 partial pressure and the heat of solution for seven common solvents. The calculations were done at 40˚C, CO2 loading of 0.15, and a solvent strength of 7m. The solid line is an exponential correlation of the data. The open squares represent the eight artificial A Series solvents. The three vertical lines represent the artificial H55, H65 and H75 Series of solvents.
Mathias – Applied Thermodynamics in CO2 Capture Process Technology - Fluid Phase Equilibria - 2013
14 Page 14 of 19
125 A-2
A-8
A-3
A-7
ip t
120
A-4 A-5
A-6
cr
115
A-4
A-7
105 1
A-2
us
A-8
110
A-3
A-5
A-6
2
3
an
Reboiler Duty (kJ/mol CO2)
130
4
5
6
Norm. Solv. Flow Rate (mols Solvent/mol CO2 Captured)
M
Figure 7 Reboiler duty versus normalized solvent flow rate (solvent flow rate divided by rate of CO2 capture) for A Series solvents.
d
160
te
170
A-4
Ac ce p
Reboiler Duty (kJ/mol CO2 )
180
A-5
150
55-7
A-8
75-6
140
75-6
65-7
65-7
130
55-7
A-8
120
A-5
A-4
110
1
2
3
4
5
For A-4 and A-5 is -71 and -76 kJ/mol 6
Norm. Solv. Flow Rate (mols Solvent/mol CO2 Captured) Figure 8 Reboiler duty of the high capacity solvents; The solvents A8, H75-6, H65-7 and H55-7 all have low CO2 partial pressure (≈ 0.003 kPa) at the standard conditions (Figure 6). For comparison, the reboiler duties of solvents A-4 and A-5 are also presented.
Mathias – Applied Thermodynamics in CO2 Capture Process Technology - Fluid Phase Equilibria - 2013
15 Page 15 of 19
800 700
500 BOL
ip t
CO2 PP (kPa)
600
400
BOL‐H2O
300
BOL‐C16
cr
200
BOL‐H2O‐C16
us
100 0 0
0.2
0.4
0.6
an
CO2 Loading (Moles CO2/Mol BOL)
M
Figure 9 Estimated CO2 partial pressures in BOL-H2O-AS at 100 ˚C. The relative solvent concentrations are equimolar.
100
d
90
te
70 60
Ac ce p
% CO2 Complexed
80
BOL
50
BOL‐C16
40
BOL‐H2O
30
BOL‐H2O‐C16
20 10 0
0
0.2
0.4
0.6
CO2 Loading (Moles CO2/Mole BOL)
Figure 10 Fraction of CO2 in BOL-H2O-C16 at 100 ˚C that is complexed. The relative solvent concentrations are equimolar.
Mathias – Applied Thermodynamics in CO2 Capture Process Technology - Fluid Phase Equilibria - 2013
16 Page 16 of 19
90 80
ip t
60
40
40°C
30
60°C
cr
50
80°C
20
100°C
10 0 0
0.1
0.2
0.3
0.4
0.5
an
CO2 Loading (Moles CO2/Mole BOL)
us
‐Hsoln (kJ/mol)
70
Ac ce p
te
d
M
Figure 11 Calculated enthalpy of solution of CO2 in BOL.
Mathias – Applied Thermodynamics in CO2 Capture Process Technology - Fluid Phase Equilibria - 2013
17 Page 17 of 19
References[1] G. Lewis, M. Randall, Thermodynamics and the Free Energy of Chemical Substances, McGraw-Hill Book Company, New York and London, 1923. [2] C.-C. Chen, P. M. Mathias, AIChE J., 48 (2004) 194-200. [3] P. M. Mathias, Fluid Phase Equilibria, 228-229 (2005) 49-57.
Zilnik, V. Vesovic, Ind. Eng., Chem. Res., 49 (2010) 11131-11141.
ip t
[4] E. Hendriks, G. M. Kontogeorgis, R. Dohrn, J. de Hemptinne, I. G. Economou, L. F. [5] J. P. O’Connell, R. Gani, P. M. Mathias, G. Maurer, J. D. Olson, P. A. Crafts, Ind. Eng. Chem. Res., 48 (2009) 4619-4637.
cr
[6] D. Adams, J. Davison, “Capturing CO2,” IEA Greenhouse Gas R&D Programme Report, 2007.
us
[7] A. Cousins, L. T. Wardhaugh, P. H. M. Feron, Int. J. Greenhouse Gas. Contr., 5 (2011) 605-619. [8] P. M. Mathias, S. Reddy, A. R. Smith, K. Afshar, “A Guide to Evaluate Solvents and Processes for Post-Combustion CO2 Capture,” to appear in Energy Procedia, 2013.
an
[9] R. D. Deshmukh, A. E. Mather, A. E. Chem. Eng. Sci. 36 (1981) 355-362. [10] J. J. Kosinski, P. Wang, R. D. Springer, A. Anderko, A. Fluid Phase Equilibria 1-2 (2007) 34-41.
M
[11] Y. Zhang, C.-C. Chen, Ind. Eng. Chem. Res. 50 (2011) 6436-6446 [12] P. Brúder, A. Grimstvedt, T. Mejdell, H. F. Svendsen, Chem. Eng. Sci. 66 (2011) 6193-6198.
d
[13] J. P. O’Connell, M. Neurock, AIChE Symp. Ser., 25 (2000) 5-23.
te
[14] R. Gani, J. P. O’Connell, Comput. Chem. Eng., 25 (2001), 3-14. [15] G. Rochelle, G, Science, 325 (2009) 652-1654
Ac ce p
[16] K. P. Resnik, J. T. Yeh, H. W. Pennline, Int. J. Environ. Technol. Manage., 4 (2004) 89-104. [17] E. Gal, S. Olson, “Chilled ammonium process (CAP) for post combustion CO2
capture,” Presented at the 2nd Annual Carbon Capture and Transportation Working Group Workshop, Palo Alto, March 23, 2006.
[18] DOE/NETL Report, “Chilled ammonia-based wet scrubbing for post-combustion
CO2 capture.,” DOE/NETL-401/02107, February, 2007. [19] P. M. Mathias, S. Reddy, J. P. O’Connell, Int. J. Greenhouse Gas. Contr., 4 (2010) 174-179. [20] F. Qin, S. Wang, I. Kim, H. F. Svendsen, C. Chen, Int. J. Greenhouse Gas. Contr., 5 (2011) 405-412. [21] F Kurz, B. Rumpf, G. Maurer, Fluid Phase Equil., 104 (1995) 261-275.xx [22] M. Zhang, Y. Guo, Appl. Energy, 11 (213) 142-152. [23] H. Yu, S. Morgan, A. Allport, A. Cottrell, T Do, J. Mcgregor J, L. Wardhaugh, P. Feron, Chem. Eng. Res. Des., 89 (2011) 1204–1215. [24] P. Mathias, J. P. O’Connell, Ind. Eng. Chem. Res., 51 (2012) 5090-5097.
Mathias – Applied Thermodynamics in CO2 Capture Process Technology - Fluid Phase Equilibria - 2013
18 Page 18 of 19
[25] Y. Zhang, H. Que, C.-C. Chen, Fluid Phase Equil., 311 (2011)68-76. [26] F.-Y. Jou, A. E. Mather, F. D. Otto, Can. J. Chem. Eng., 73 (1995) 140-147. [27] J. K. Carson, K. N. Marsh, A. E. Mather, J. Chem. Thermo, 32 (2000) 1285-1296. [28] H. Arsis, K. Ballerat-Busserolles, L. Rodier, J.-Y. Coxam, J. Chem. Eng. Data, 56 (2011) 3351-3362.
ip t
[29] C. Mathonat, V. Majer, A. E. Mather, J. P. E. Grolier, Ind. Eng. Chem. Res., 37 (1998) 4136-4141. [30] I. Kim, H. F. Svendsen, Ind. Eng. Chem. Res., 46 (2007) 5803-5809.
cr
[31] C. Mathonat, V. Majer, A. E. Mather, J. P. E. Grolier, Ind. Eng. Chem. Res., 37
(1998) 4136-4141.
us
[32] I. Kim, H. F. Svendsen, Ind. Eng. Chem. Res., 46 (2007) 5803-5809.
[33] C. Mathonat, V. Majer, A. E. Mather, J. P. E. Grolier, Ind. Eng. Chem. Res., 37 (1998) 4136-4141.
an
[34] I. Kim, H. F. Svendsen, Ind. Eng. Chem. Res., 46 (2007) 5803-5809. [35] Q. Xu, Ph. D. Dissertation, University of Texas, Austin, 2011. [36] Q. Xu, G. Rochelle, Energy Procedia, 4, (2011) 117-124.
M
[37] P. M. Mathias, S. Reddy, A. R. Smith, K. Afshar, “Thermodynamic Analysis of CO2
Capture Solvents” accepted for publication in Int. J. Greenhouse Gas. Contr., 2013
[38] Y. Zhang, C.-C. Chen, Ind. Eng. Chem. Res., 50 (2011) 163-175.
d
[39] J. Oexmann, J. Kather, Int. J. Greenhouse Gas Contr., 4 (1020) 36-43.
te
[40] F. A. Tobiesen, H. Svendsen, Ind. Eng. Chem. Res., 45 (2006), 2489-2496. [41] B. Oyenekan, Ph. D. Dissertation, University of Texas, Austin, 2011
Ac ce p
[42] P. M. Mathias K. Afshar , F. Zheng, M. D. Bearden, C. J. Freeman, T. Andrea, P. K. Koech, I. Kutnyakov, A. Zwoster, A. R. Smith, P. G. Jessop, O. Ghaffari Nik, D. J. Heldebrant, Energy & Environ. Sci., 6 (2013) 2233-2242. [43] J. Oexman, A. Kather, S. Linnenberg, U. Liebenthal, Greenhouse Gas Sci. Technol., 2 (2012), 80-98. [44] M. Born, Zietschrift für Physik, 1 (1920) 45. [45] J. G. Kirkwood, J. Chem. Phys., 2 (1934), 351-361.
Mathias – Applied Thermodynamics in CO2 Capture Process Technology - Fluid Phase Equilibria - 2013
19 Page 19 of 19
S0378-3812(13)00511-6 http://dx.doi.org/doi:10.1016/j.fluid.2013.09.016 FLUID 9764
To appear in:
Fluid Phase Equilibria
Received date: Revised date: Accepted date:
16-7-2013 2-9-2013 5-9-2013
Please cite this article as: P.M. Mathias, Some Examples of the Contribution of Applied Thermodynamics to Post-Combustion CO2 -Capture Technology, Fluid Phase Equilibria (2013), http://dx.doi.org/10.1016/j.fluid.2013.09.016 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
cr
Paul M. Mathias Fluor Corporation 3 Polaris Way Aliso Viejo, CA 92698 [email protected]
ip t
Some Examples of the Contribution of Applied Thermodynamics to PostCombustion CO2-Capture Technology
Abstract
an
us
There is intense ongoing worldwide research to develop improved solvents and processes for CO2 capture from flue gas. The number of publications was almost 1,000 in 2011, and may be expected to exceed 10,000 by 2020 if exponential extrapolation of the number of past publications is applicable. Applied thermodynamics is a valuable tool to make sense of this vast body of research, and we present three examples of its contribution to CO2-capture process technology.
Ac ce p
te
d
M
Aqueous-ammonia processes have been proposed as energy-efficient alternatives to traditional alkanolamine process, and early proponents claimed that a significant advantage of the technology is that the CO2 heat of solution is exceptionally low, about 27 kJ/mol. A rigorous thermodynamic model with correct speciation estimated that the CO2 heat of solution is closer to about 65 kJ/mol, a number that was later confirmed by calorimetric measurements. The thermodynamic model enabled realistic analysis of the chilled-ammonia process, and these results have been supported by subsequent studies by other researchers. Further work on this subject established the rigorous and complete form of the Gibbs-Helmholtz equation, and demonstrated its value in evaluating the consistency between vapor-liquid equilibrium and calorimetric data. Theoretical and experimental studies have been used to find the best solvent for CO2 capture. Some researchers have assumed that the goal is seek solvents with high CO2 capacity and a low heat of solution. This notion was tested by inventing solvents with various properties, the only restriction being that the properties must be thermodynamically consistent. The results have provided insight into the interplay between CO2 absorption and the heat of regeneration (through the Gibbs-Helmholtz equation), and reveal subtle characteristics that may guide the development of future solvents. A promising step-out technology for CO2 capture is “CO2-binding liquids with polarityswing-assisted regeneration.” Reliable analysis and design of this complex technology requires a thermodynamic model that describes the chemical absorption (i.e., speciation) as well as vapor-liquid-liquid equilibrium. The initial thermodynamic model has enabled useful projections of process performance. The model limitations and the need for future improvements are also discussed. Keywords: CO2 capture, applied thermodynamics, process simulation, Gibbs-Helmholtz equation, heat of solution, vapor-liquid-liquid equilibrium
Mathias – Applied Thermodynamics in CO2 Capture Process Technology - Fluid Phase Equilibria - 2013
1 Page 1 of 19
1. Introduction
us
cr
ip t
Applied thermodynamics has a rich history as a foundational tool for chemical process technology. To quote from the dedication of the 1923 Lewis and Randall [1] textbook: “The fascination of a growing science lies in the work of the pioneers at the very borderland of the unknown, but to reach this frontier one must pass over well traveled roads; of these one of the safest and surest is the broad highway of thermodynamics.” Over the last 90 years, many papers have highlighted the essential role thermodynamics and physical properties have played in the engineering of chemical products and in the processes that produce them. [2,3,4,5] This paper studies the broad role applied thermodynamics is playing in the technology of CO2-capture from flue gas through three representative examples.
te
d
M
an
Applied thermodynamics plays an especially strong role in Post-Combustion CO2Capture (PCCC) process technology because energy reduction is by far the most important goal of the process design. As Adams and Davison [6] and Cousins, Wardhaugh and Feron have [7] pointed out, today’s PCCC technology is expected to reduce the thermal efficiency of a power station by about 20%, while the loss of product for the separation of CO2 from natural gas is typically 2% - a difference of one order of magnitude. Today’s process analysis is based upon computer modeling that in turn depends on property models,Error! Bookmark not defined. and hence accurate estimation of the thermodynamic properties for CO2 capture from flue gas is of the utmost importance to invent new processes and to evaluate existing ones.
Ac ce p
The CO2-capture literature is very difficult to follow because the number of papers and patents has exploded, and the claims of the authors are difficult to substantiate. According to the study by Mathias et al.,8] from a beginning in the early 90s with just a handful of papers each year, the number of yearly papers has grown exponentially, reaching almost 1,000 publications in 2011. If this exponential rate of increase continues, the number of yearly publications will exceed 10,000 before 2020! Hence it is important - and even necessary - to apply the “safe and sure” hand of applied thermodynamics to PCCC technology. The role of applied thermodynamics in chemical process technology is depicted in Figure 1. For the purposes of computer modeling, the property data are captured in a property model (center of Figure 1). The property model is typically phenomenological or semiempirical,9,10,11] but may also be totally empirical. [12] However, as we strongly emphasize in this work, it is important that the property model is thermodynamically consistent. The property model is designed to provide an accurate representation of the property data, and these data may come from experimental measurements, molecular modeling and/or estimation methods.Error! Bookmark not defined.,Error! Bookmark not defined.,Error! Bookmark not defined. The property model is used either in the forward model (process design) or in the reverse mode (product design). [13,14] The forward mode is the most common use of applied thermodynamics, but, as we highlight in this work, the reverse mode can be quite useful. Mathias – Applied Thermodynamics in CO2 Capture Process Technology - Fluid Phase Equilibria - 2013
2 Page 2 of 19
In this work, we use three selected examples to illustrate the wide role applied thermodynamics is playing in PCCC process technology.
2. Examples of Applied Thermodynamics in Post-Combustion CO2-Capture
ip t
Process Technology
us
cr
Three examples have been selected to illustrate the role of applied thermodynamics in PCCC technology. No new information is provided in the present paper. Rather, the purpose of the present work is to use existing publications to demonstrate at a high level the patterns of analyses that make applied thermodynamic a most useful tool.
an
Example 1. “What is the enthalpy of Solution?” The Gibbs-Helmholtz equation together with treatment of the chemical equilibria of the complexes and ions that form in the liquid phase enable validated thermodynamic models that are reliable and accurate for phase equilibrium as well as thermodynamic properties such as enthalpy..
M
Example 2. “What is the ‘best thermodynamic solvent’ for post-combustion CO2 capture?” Creating a series of artificial solvents whose only restriction is thermodynamic consistency enables insight into desired solvent characteristics, and may provide a rational method to invent improved solvents.
Ac ce p
te
d
Example 3. “How does thermodynamic modeling and analysis support and enable a novel CO2-capture technology?” The novel technologies being proposed for postcombustion CO2 capture involve complex chemicals and new process concepts. Applied thermodynamics provides a reliable framework to analyze, validate and improve these novel technologies, i.e., the safe and sure broad highway of thermodynamics.
2.1. Example 1: Enthalpy of Solution It is generally accepted that traditional alkanolamines absorption-stripping processes will be the first to be applied on a large scale for PCCC technology. [15] Starting about the beginning of the past decade, aqueous-ammonia processes for PCCC were proposed as energy-efficient alternatives to traditional alkanolamines absorption-stripping processes, and the main reason given by researchers was that the heat CO2 enthalpy of solution is -260 Btu/lb CO2 (-27 kJ/mol CO2). [16,17,18] Mathias, Reddy and O’Connell [19] applied a rigorous thermodynamic analysis, which included application of the GibbsHelmholtz equation and the correct chemistry model, and concluded that a more accurate enthalpy of solution is in the range of -600 to -700 Btu/lb CO2 (-61 to -72 kJ/mol CO2). Mathias et al.Error! Bookmark not defined. identified the root cause for the incorrect estimation of the enthalpy of solution. Previous researchers assumed that the only chemical reaction occurring in the regenerator is the chemical conversion of ammonium bicarbonate to ammonium carbonate:
Mathias – Applied Thermodynamics in CO2 Capture Process Technology - Fluid Phase Equilibria - 2013
3 Page 3 of 19
2NH4+ + 2HCO3- → 2NH4+ + CO32- + H2O(l) + CO2(g)
ΔHrxn ≈ 266 Btu/lb CO2
us
cr
ip t
However, several other reactions (including carbamate formation) occur simultaneously, and a model that properly treats chemical equilibrium is required. Figure 2 compares two estimation methods for the enthalpy of solution of CO2 in 8 wt% aqueous ammonia at about 38 ˚C with the calorimetric data of Qin et al. [20] The first method (labeled Thermodynamic Model) is from the rigorous thermodynamic model developed by Mathias et al.,Error! Bookmark not defined. while the second method (labeled From VLE Data of Kurz (1995)) applied the Gibbs-Helmholtz equation to the experimental vapor-liquid data Kurz et al. [21] Figure 2 is similar to Figure 7 from Reference [Error! Bookmark not defined.]. It is noted here that Reference [Error! Bookmark not defined.] was published before the data of Qin et al.Error! Bookmark not defined. were available, and thus may be considered to be a prediction of the enthalpy of solution of CO2 in aqueous ammonia in the absence of experimental data..
M
an
Mathias et al.Error! Bookmark not defined. used their thermodynamic model to analyze the chilled ammonia processError! Bookmark not defined. and concluded that, “The chilled-ammonia process is judged to be equivalent to alkanolamine-based absorption processes for LP steam consumption, but may be rendered noncompetitive because of the large refrigeration loads that are not needed in alkanolamine-based processes.” Our goal in this publication is not to make a conclusive judgment on the viability of the aqueous ammonia processes for PCCC, but rather to highlight role of applied thermodynamics in improving the objective analysis of this process technology.
te
d
Today, it appears that reliable and accurate thermodynamic models are being used to design and evaluate aqueous-ammonia processes for PCCC. For example, Zhang and Guo [22] have used a thermodynamic model to simulate the pilot-plant data of Yu, et al.,23] and report good agreement between simulation predictions and plant results. Applied thermodynamics has proved to be a sound enabling tool to model, evaluate and improve this complex process.
Ac ce p
Mathias and O’Connell [24] performed a deeper analysis of the useful Gibbs-Helmholtz (G-H) equation and presented the rigorous form:
⎛ ∂H ΔH 0 i ≡ ⎜⎜ ⎝ ∂n 0 i
⎞ ⎟⎟ − hi* ⎠ T , P , n0 j
⎛ ∂ ln f i ⎞ ⎟⎟ = R ⎜⎜ − ⎝ ∂ (1 / T ) ⎠ σ , {x 0}
V0 i T
= f − Term
P − Term
−
⎛ ∂P ⎞ ⎜⎜ ⎟⎟ ⎝ ∂ (1 / T ) ⎠ σ , {x 0}
where, ΔH 0 i is the differential enthalpy of solution, which is equal to the sum of two terms, the f-Term and the P-Term. The P-Term was unknown prior to The MathiasO’Connell publication, and hence was neglected in previous applications of the G-H equation, but it turns out that the usual approximation is fortunately valid, i.e., the P-term is insignificant for absorption in the liquid phase far from critical conditions. Mathias and O’ConnellError! Bookmark not defined. used the simplified G-H equation (with the PTerm ignored) to evaluate the consistency between vapor-liquid equilibrium (VLE) and calorimetric data for the CO2 absorption in aqueous monoethanolamine (MEA). They performed an integration using calculations from the model of Zhang, Que and Chen [25]
Mathias – Applied Thermodynamics in CO2 Capture Process Technology - Fluid Phase Equilibria - 2013
4 Page 4 of 19
ip t
at a base temperature of 40 ˚C to predict the VLE data of Jou, Mather and Otto [26] at other temperatures by using two possibilities for the CO2 enthalpy of solution, and these are shown in Figure 3. The fixed value of -85 kJ/mol CO2 is based upon the VLE data of Jou et al.Error! Bookmark not defined. and the calorimetric data of Carson, Marsh and Mather [27] and Arsis et al.,28] while the linear variation with temperature is based upon the calorimetric data of Mathonat et al. [29] and Kim and Svendsen. [30] Figure 4 indicates that a fixed value of the CO2 enthalpy of solution enables an excellent prediction of the Jou et al.Error! Bookmark not defined. at all temperatures, which implies that the Jou et al. VLE data estimate a constant value of ΔH 0 i equal to about -85 kJ/mol CO2.
an
us
cr
However, Figure 5 shows that using values of ΔH 0 i from the calorimetric measurements of Mathonat et al. [31] and Kim and Svendsen [32] do not give an accurate estimate of the Jou et al.Error! Bookmark not defined. data at high temperatures. According to the G-H thermodynamic-consistency criterion, either the high-temperature calorimetric data from Mathonat et al. [33] and Kim and Svendsen [34] or the high temperature VLE data of Jou et al.Error! Bookmark not defined. – or both sets of data – are inaccurate. Xu [35] and Xu and Rochelle [36] also concluded that enthalpy of solution of CO2 in aqueous MEA does not vary significantly with temperature. Additional high-temperature data are needed to resolve the issue.
M
This section has demonstrated the use of exact thermodynamic relationships to challenge and validate experimental data. The long-term benefit is that the thermodynamic models used for process analysis will continuously improve to become increasingly accurate and reliable.
te
d
2.2. Example 2: “Best Thermodynamic Solvent” for PCCC
Ac ce p
Optimizing PCCC processes is highly complicated because performance depends on solvent and process characteristics, and even just the solvent characteristics depend on a variety of features, such as thermodynamics, kinetics, toxicity and cost. Mathias, et al. [37] attempted to understand and rate solvent characteristics by focusing on thermodynamic properties alone, i.e., the applied-thermodynamics approach. The study began by understanding the absorption characteristics of existing solvents in terms of two criteria at the chosen standard condition of CO2 loading (mols CO2/mol solvent) of 0.15 and temperature of 40 ˚C: the absorption strength, identified by the CO2 partial pressure, and the enthalpy of solution. Figure 6 presents the properties of the seven common solvents. There appears to be a simple exponential relationship between the enthalpy of solution and the solvent strength. This relationship has been used to invent four artificial families of solvents, all based upon the MDEA (methyldiethanolamine) model published by Zhang and Chen. [38] Figure 6 shows the characteristics of the four families of solvents. The A Series are a standardized family of solvents intended to represent the seven common solvents. The three other families of solvents (H55, H65 and H75) are families of solvents where the standard enthalpy of solution has been held constant and the solvent strength varied; the naming convention is that the number following ‘H’ is the standard enthalpy of solution in kJ/mol CO2. The purpose of the four artificial families of solvents is to systematically study the variation of absorption capacity and enthalpy of solution while maintaining thermodynamic consistency, i.e., the G-H equation is strictly followed.
Mathias – Applied Thermodynamics in CO2 Capture Process Technology - Fluid Phase Equilibria - 2013
5 Page 5 of 19
ip t
Mathias et al.Error! Bookmark not defined. performed the study by using a fixed flowsheet so that the performance of the different solvents essentially resulted from the variation in thermodynamic properties alone. All performance properties were calculated as a function of a single variable, the solvent circulation rate. The work of Mathias et al.Error! Bookmark not defined. presents a detailed report of the study. Here we only present key findings that demonstrate the role of applied thermodynamics in providing insight into the “best thermodynamic solvent.”
us
cr
Perhaps the most important indicator of solvent performance is the steam consumption, here represented as the reboiler duty divided by the amount of CO2 captured. Figure 7 indicates that, for the Series A solvents, the reboiler duty increases as the magnitude of the enthalpy of solution increases. But the solvent needs to be sufficiently strong as solvent A-1 is not sufficiently strong to meet the flowsheet criterion, and thus does not appear on Figure 7. In addition, the weakest solvents (A-2 and A-3) require a relatively high solvent circulation rate.
M
an
The “intuitive conclusion” of PCCC technology is that solvents below the line of the Series A solvents are in the “target zone.” In other words, research efforts to develop advanced solvents should target those with high capacity and low (magnitude) of the enthalpy of solution. Figure 8 compares the performance of the strongest solvents (lowest CO2 partial pressure at the standard conditions). It is clear that when the absorbent is very strong, a low enthalpy of solution causes significant deterioration in solvent performance. As a comparison, Figure 8 also presents the performance of the best solvents in the study (A-4 and A-5).
te
d
Mathias et al.Error! Bookmark not defined. concluded that on a thermodynamic basis alone, the “best solvent” is one that lies along the line of the common solvents in Figure 6. If keeping the solvent circulation rate low is important, solvents A-4 and A-5 are probably optimum.
Ac ce p
More analysis is needed on this complex issue. Is some ways, the study of Mathias et al.Error! Bookmark not defined. agrees with the approach of proponents of aqueous-ammonia technology who determined that a low enthalpy of solution is preferred.Error! Bookmark not defined.,Error! Bookmark not defined.,Error! Bookmark not defined. Further, the results of Mathias et al.Error! Bookmark not defined. seem to disagree with the works of Oexmann and Kather,39] Tobiesen and Svendsen,40] and Oyenekan,41] who concluded that a higher heat of solution is often preferable. It is critically important that these studies be done for carefully defined solvent variations. Further, the study of Mathias et al.Error! Bookmark not defined. was performed for a fixed flowsheet, and it is possible that additional subtleties will be revealed by process variations, such as a higher stripper pressure. Of course, thermodynamic analysis is only one aspect of the comprehensive analysis needed for PCCC processes. Even if a solvent is judged to be excellent on the basis of thermodynamic analysis, its reaction kinetics and mass transfer may be slow, and this will result in large absorber towers high capital cost and large pressure drops that result in high blower energy costs. Or, the optimum thermodynamic solvent may be susceptible to degradation and produce toxic by-products. However, it is also clear that applied thermodynamics offers unique insight into the complex PCCC process technology, and is an important aspect of the comprehensive technology evaluation.
Mathias – Applied Thermodynamics in CO2 Capture Process Technology - Fluid Phase Equilibria - 2013
6 Page 6 of 19
2.3. Example 3: Novel PSAR Technology
ip t
Process modeling has been an important tool to evaluating PCCC processesError! Bookmark not defined. and studying and validating proposed process improvements.Error! Bookmark not defined. Here we briefly highlight the role of applied thermodynamics in evaluating and developing a novel technology: CO2-binding organic liquids with a polarity change. [42]
M
an
us
cr
Mathias et al.Error! Bookmark not defined. recently described a novel solvent regeneration method unique to CO2-binding organic liquids (CO2BOLs) and other switchable ionic liquids, which is known as PSAR (Polarity Swing Assisted regeneration) technology. The first potential advantage of the proposed technology is that the water levels are very low. One of the main reasons why the solvents with low enthalpy of solution perform poorly in Figure 8 is that low enthalpy of solution makes the stripping step more difficult, and hence larger flows of stripping steam are needed, which must be vaporized in the reboiler, and this increases the reboiler duty. [43] PSAR technology uses a solvent with minimum water levels to reduce the reboiler duty associated with water evaporation. The second advance of PSAR technology is to use a chemically inert nonpolar “antisolvent” such as hexadecane to aid in releasing CO2 from the CO2-rich CO2BOL. The advantage of PSAR technology is that the stripping step now occurs at a significantly lower temperature, which offers three primary benefits: reduced thermal degradation of the CO2BOL solvent, lower fugitive emissions, and potential for higher net power produced by the utility plant. As an example, the lower stripping temperature could enable the use of a simple let-down turbine to extract work from the steam as it is expanded to lower temperatures.
te
d
New process technologies require a wide range of analyses and evaluations. The discussion here is limited to the development of the thermodynamic model needed for quantitative process analysis through process simulation.
Ac ce p
The chemistry model developed was based upon an understanding of the fundamental chemistry as well as practical experience with electrolyte process simulation. Two complexes were proposed that result in the following two chemical equilibrium equations: 2 CO2 + 2 BOL ↔ BOLCO2+ + BOLCO2-
(1)
H2O + BOL + CO2 ↔ BOLH+ + HCO3-
(2)
Breaking out separate charges for the complex formed in Eq. 1 is actually an approximation as this complex is expected to be a single zwitterionic CO2BOL-CO2 species. The approximation was made as it is convenient to use the Born term,44] which is available in the Aspen Plus electrolyte model. Research is underway to evaluate the use of the Kirkwoog-Onsager [45] approach to model this effect, but the Born term has been retained in the present model. The thermodynamic model has enabled a quantitative description of the complex phase behavior of the CO2-H2O-BOL-AS system. Figure 9 shows the calculated CO2 partial pressures at 100 ˚C for four representative solvent compositions. The composition on the x-axis is the CO2 loading with respect to the BOL. Figure 9 shows that adding 1 mole of H2O to 1 mole of BOL significantly reduces the CO2 partial pressure, while adding 1 mole of AS (C16) to 1 mole of BOL sharply increases the CO2 partial pressure. The 1:1:1 Mathias – Applied Thermodynamics in CO2 Capture Process Technology - Fluid Phase Equilibria - 2013
7 Page 7 of 19
BOL-H2O-AS solvent has an absorption strength between those of neat BOL and 1:1 H2O:BOL. Figure 10, which presents the fraction of CO2 that is complexed, provides an explanation of the results in Figure 9. The reduction of the CO2 partial pressure is caused by increased complexation of the CO2, and conversely, the increase of the partial pressure is due to decomplexation of CO2 from the BOL.
cr
ip t
The enthalpy of solution is very important as the main goal of PCCC processes is to reduce the energy cost of CO2 capture, and this energy cost is directly related to the enthalpy of solution. Figure 11 shows the enthalpy of solution of CO2 in BOL as a function of temperature and CO2 loading. At 40°C (typical absorber temperature), the enthalpy of solution is about −82 kJ/mol at low CO2 loadings and then decreases in magnitude with CO2 loading. The model accounts for expected behavior; as the temperature increases, the magnitude of the enthalpy of solution decreases, as does the CO2 loading at which the enthalpy of solution drops.
an
us
Further details of the model and the process simulations have been given by Mathias et al.,Error! Bookmark not defined. but we note here that the key enabling tool is the thermodynamic model. The purpose of the brief discussion presented here is to identify and highlight the role of applied thermodynamics in this novel and complex PCCC technology.
3. Summary and Conclusions
d
M
90 years ago Lewis and Randall identified thermodynamics as an essential tool to evaluate and improve chemical technology. This work has used three examples from current PCCC process technology to demonstrate that applied thermodynamics is still important and even necessary for effective chemical technology.
Example 1 has shown that the rigorous relationships offered by thermodynamics challenge and validate experimental data, which improves the reliability and accuracy of thermodynamic models. The end result is stronger chemical process technology.
Ac ce p
•
te
Referring back to Figure 1, this paper has highlighted three ways in which applied thermodynamics provides a valuable contribution:
•
Example 2 offered one way in which thermodynamic analysis can provide insight into solvent performance, and hence guide research into improved solvents for PCCC.
•
Example 3 is an on-going effort. It demonstrates that applied thermodynamics can provide the same useful input to novel technology as it has provided to the mature alkanolamine process technology.
Acknowledgement The author is pleased to recognize his collaborators from PNNL (Mark Bearden, Charles Freeman, David Heldebrant, Philip Koech, Igor Kutnyakov, Feng Zheng, and Andy Zwooster), Queens University (Tamer Andrea, Philip Jessop, and Omid Nik), the University of Virginia (John P. O’Connell), and Fluor Corporation (Kash Afshar, Satish Reddy, and Arnold Smith) who were co-authors on the examples used in this work. Mathias – Applied Thermodynamics in CO2 Capture Process Technology - Fluid Phase Equilibria - 2013
8 Page 8 of 19
List of Figures Figure 1 Applied thermodynamics in chemical process technology............................... 10
ip t
Figure 2 Comparison of the estimated enthalpy of solution of CO2 in 8 wt% aqueous NH3 by two methods with the calorimetric data of Qin et al.20 The two estimation methods are described in the text. ............................................... 11
cr
Figure 3 Two possibilities for the enthalpy of solution of CO2 in aqueous MEA. Hsoln-1 is a constant value of -85 kJ/mol CO2, and Hsoln-2 is a linear fit to the data of Mathonat et al.28 and Kim and Svendsen.29 .................................................. 12
us
Figure 4 Prediction of the CO2 partial pressure in aqueous MEA using integration and a constant (-85 kJ/mol CO2) heat of solution.................................................... 13 Figure 5 Prediction of the CO2 partial pressure in aqueous MEA using integration and a linear heat of solution. See Figure 3 for details. ........................................... 13
M
an
Figure 6 Relationship between the CO2 partial pressure and the heat of solution for seven common solvents. The calculations were done at 40˚C, CO2 loading of 0.15, and a solvent strength of 7m. The solid line is an exponential correlation of the data. The open squares represent the eight artificial A Series solvents. The three vertical lines represent the artificial H55, H65 and H75 Series of solvents. ................................................................................. 14
d
Figure 7 Reboiler duty versus normalized solvent flow rate (solvent flow rate divided by rate of CO2 capture) for A Series solvents. ................................................... 15
te
Figure 8 Reboiler duty of the high capacity solvents; The solvents A8, H75-6, H65-7 and H55-7 all have low CO2 partial pressure (≈ 0.003 kPa) at the standard conditions (Figure 6). For comparison, the reboiler duties of solvents A-4 and A-5 are also presented. ................................................................................. 15
Ac ce p
Figure 9 Estimated CO2 partial pressures in BOL-H2O-AS at 100 ˚C. The relative solvent concentrations are equimolar............................................................ 16 Figure 10 Fraction of CO2 in BOL-H2O-C16 at 100 ˚C that is complexed. The relative solvent concentrations are equimolar............................................................ 16 Figure 11 Calculated enthalpy of solution of CO2 in BOL. ............................................. 17
Mathias – Applied Thermodynamics in CO2 Capture Process Technology - Fluid Phase Equilibria - 2013
9 Page 9 of 19
ip t cr us
Ac ce p
te
d
M
an
Figure 1 Applied thermodynamics in chemical process technology.
Mathias – Applied Thermodynamics in CO2 Capture Process Technology - Fluid Phase Equilibria - 2013
10 Page 10 of 19
ip t
75
cr
70
60
⎧ ∂ ln(PCO2 )⎫ Solution H CO = − R⎨ ⎬ 2 ⎩ ∂(1 / T ) ⎭ Loading
0
Thermodynamic Model From VLE Data of Kurtz (1995) Data of Qin (2011)
M
55
us
65
an
- Enthalpy of Solution (kJ/mol CO2)
80
0.2
0.4
0.6
0.8
CO2 Loading (mols CO2/mol NH3)
Ac ce p
te
d
Figure 2 Comparison of the estimated enthalpy of solution of CO2 in 8 wt% aqueous NH3 by two methods with the calorimetric data of Qin et al.Error! Bookmark not defined. The two estimation methods are described in the text.
Mathias – Applied Thermodynamics in CO2 Capture Process Technology - Fluid Phase Equilibria - 2013
11 Page 11 of 19
110 105
Mathonat (1998) Carson (2000) Kim (2007) Arcis (2011) Hsoln-1
ip t
100
Hsoln-2
cr
95
us
90
80
300
320
340
360
M
75 280
an
85
380
400
420
Temperature/ K
Ac ce p
te
d
Figure 3 Two possibilities for the enthalpy of solution of CO2 in aqueous MEA. Hsoln-1 is a constant value of -85 kJ/mol CO2, and Hsoln-2 is a linear fit to the data of Mathonat et al.Error! Bookmark not defined. and Kim and Svendsen.Error! Bookmark not defined.
Mathias – Applied Thermodynamics in CO2 Capture Process Technology - Fluid Phase Equilibria - 2013
12 Page 12 of 19
1
CO2 Loading
ip t
0.1 298.15 K
cr
313.15 K 323.15 K
0.01
353.15 K
us
373.15 K 393.15 K
0.001 0.001
0.01
0.1
an
Base Temp: 313.15K
1
423.15 K
10
100
M
CO2 Partial Pressure/ kPa
d
Figure 4 Prediction of the CO2 partial pressure in aqueous MEA using integration and a constant (85 kJ/mol CO2) heat of solution.
Ac ce p
te
1
CO2 Loading
0.1
298.15 K 313.15 K 333.15 K
0.01
353.15 K 373.15 K 393.15 K
Base Temp: 313.15 K 0.001 0.001
0.01
0.1
1
423.15 K 10
100
CO2 Partial Pressure/ kPa
Figure 5 Prediction of the CO2 partial pressure in aqueous MEA using integration and a linear heat of solution. See Figure 3 for details.
Mathias – Applied Thermodynamics in CO2 Capture Process Technology - Fluid Phase Equilibria - 2013
13 Page 13 of 19
100 10
MDEA
Open Squares are A Series
ip t
TEA
0.1
cr
1
AMP NH3
H55
H65
0.01
H75 50
60
70
PZ
MEA
an
0.001
us
CO2 PP (kPa) at α = 0.15
-2.10E-01x
y = 5.20E+05e 2 R = 9.29E-01
80
DGA
90
M
-Enthalpy of Solution (kJ/mol)
Ac ce p
te
d
Figure 6 Relationship between the CO2 partial pressure and the heat of solution for seven common solvents. The calculations were done at 40˚C, CO2 loading of 0.15, and a solvent strength of 7m. The solid line is an exponential correlation of the data. The open squares represent the eight artificial A Series solvents. The three vertical lines represent the artificial H55, H65 and H75 Series of solvents.
Mathias – Applied Thermodynamics in CO2 Capture Process Technology - Fluid Phase Equilibria - 2013
14 Page 14 of 19
125 A-2
A-8
A-3
A-7
ip t
120
A-4 A-5
A-6
cr
115
A-4
A-7
105 1
A-2
us
A-8
110
A-3
A-5
A-6
2
3
an
Reboiler Duty (kJ/mol CO2)
130
4
5
6
Norm. Solv. Flow Rate (mols Solvent/mol CO2 Captured)
M
Figure 7 Reboiler duty versus normalized solvent flow rate (solvent flow rate divided by rate of CO2 capture) for A Series solvents.
d
160
te
170
A-4
Ac ce p
Reboiler Duty (kJ/mol CO2 )
180
A-5
150
55-7
A-8
75-6
140
75-6
65-7
65-7
130
55-7
A-8
120
A-5
A-4
110
1
2
3
4
5
For A-4 and A-5 is -71 and -76 kJ/mol 6
Norm. Solv. Flow Rate (mols Solvent/mol CO2 Captured) Figure 8 Reboiler duty of the high capacity solvents; The solvents A8, H75-6, H65-7 and H55-7 all have low CO2 partial pressure (≈ 0.003 kPa) at the standard conditions (Figure 6). For comparison, the reboiler duties of solvents A-4 and A-5 are also presented.
Mathias – Applied Thermodynamics in CO2 Capture Process Technology - Fluid Phase Equilibria - 2013
15 Page 15 of 19
800 700
500 BOL
ip t
CO2 PP (kPa)
600
400
BOL‐H2O
300
BOL‐C16
cr
200
BOL‐H2O‐C16
us
100 0 0
0.2
0.4
0.6
an
CO2 Loading (Moles CO2/Mol BOL)
M
Figure 9 Estimated CO2 partial pressures in BOL-H2O-AS at 100 ˚C. The relative solvent concentrations are equimolar.
100
d
90
te
70 60
Ac ce p
% CO2 Complexed
80
BOL
50
BOL‐C16
40
BOL‐H2O
30
BOL‐H2O‐C16
20 10 0
0
0.2
0.4
0.6
CO2 Loading (Moles CO2/Mole BOL)
Figure 10 Fraction of CO2 in BOL-H2O-C16 at 100 ˚C that is complexed. The relative solvent concentrations are equimolar.
Mathias – Applied Thermodynamics in CO2 Capture Process Technology - Fluid Phase Equilibria - 2013
16 Page 16 of 19
90 80
ip t
60
40
40°C
30
60°C
cr
50
80°C
20
100°C
10 0 0
0.1
0.2
0.3
0.4
0.5
an
CO2 Loading (Moles CO2/Mole BOL)
us
‐Hsoln (kJ/mol)
70
Ac ce p
te
d
M
Figure 11 Calculated enthalpy of solution of CO2 in BOL.
Mathias – Applied Thermodynamics in CO2 Capture Process Technology - Fluid Phase Equilibria - 2013
17 Page 17 of 19
References[1] G. Lewis, M. Randall, Thermodynamics and the Free Energy of Chemical Substances, McGraw-Hill Book Company, New York and London, 1923. [2] C.-C. Chen, P. M. Mathias, AIChE J., 48 (2004) 194-200. [3] P. M. Mathias, Fluid Phase Equilibria, 228-229 (2005) 49-57.
Zilnik, V. Vesovic, Ind. Eng., Chem. Res., 49 (2010) 11131-11141.
ip t
[4] E. Hendriks, G. M. Kontogeorgis, R. Dohrn, J. de Hemptinne, I. G. Economou, L. F. [5] J. P. O’Connell, R. Gani, P. M. Mathias, G. Maurer, J. D. Olson, P. A. Crafts, Ind. Eng. Chem. Res., 48 (2009) 4619-4637.
cr
[6] D. Adams, J. Davison, “Capturing CO2,” IEA Greenhouse Gas R&D Programme Report, 2007.
us
[7] A. Cousins, L. T. Wardhaugh, P. H. M. Feron, Int. J. Greenhouse Gas. Contr., 5 (2011) 605-619. [8] P. M. Mathias, S. Reddy, A. R. Smith, K. Afshar, “A Guide to Evaluate Solvents and Processes for Post-Combustion CO2 Capture,” to appear in Energy Procedia, 2013.
an
[9] R. D. Deshmukh, A. E. Mather, A. E. Chem. Eng. Sci. 36 (1981) 355-362. [10] J. J. Kosinski, P. Wang, R. D. Springer, A. Anderko, A. Fluid Phase Equilibria 1-2 (2007) 34-41.
M
[11] Y. Zhang, C.-C. Chen, Ind. Eng. Chem. Res. 50 (2011) 6436-6446 [12] P. Brúder, A. Grimstvedt, T. Mejdell, H. F. Svendsen, Chem. Eng. Sci. 66 (2011) 6193-6198.
d
[13] J. P. O’Connell, M. Neurock, AIChE Symp. Ser., 25 (2000) 5-23.
te
[14] R. Gani, J. P. O’Connell, Comput. Chem. Eng., 25 (2001), 3-14. [15] G. Rochelle, G, Science, 325 (2009) 652-1654
Ac ce p
[16] K. P. Resnik, J. T. Yeh, H. W. Pennline, Int. J. Environ. Technol. Manage., 4 (2004) 89-104. [17] E. Gal, S. Olson, “Chilled ammonium process (CAP) for post combustion CO2
capture,” Presented at the 2nd Annual Carbon Capture and Transportation Working Group Workshop, Palo Alto, March 23, 2006.
[18] DOE/NETL Report, “Chilled ammonia-based wet scrubbing for post-combustion
CO2 capture.,” DOE/NETL-401/02107, February, 2007. [19] P. M. Mathias, S. Reddy, J. P. O’Connell, Int. J. Greenhouse Gas. Contr., 4 (2010) 174-179. [20] F. Qin, S. Wang, I. Kim, H. F. Svendsen, C. Chen, Int. J. Greenhouse Gas. Contr., 5 (2011) 405-412. [21] F Kurz, B. Rumpf, G. Maurer, Fluid Phase Equil., 104 (1995) 261-275.xx [22] M. Zhang, Y. Guo, Appl. Energy, 11 (213) 142-152. [23] H. Yu, S. Morgan, A. Allport, A. Cottrell, T Do, J. Mcgregor J, L. Wardhaugh, P. Feron, Chem. Eng. Res. Des., 89 (2011) 1204–1215. [24] P. Mathias, J. P. O’Connell, Ind. Eng. Chem. Res., 51 (2012) 5090-5097.
Mathias – Applied Thermodynamics in CO2 Capture Process Technology - Fluid Phase Equilibria - 2013
18 Page 18 of 19
[25] Y. Zhang, H. Que, C.-C. Chen, Fluid Phase Equil., 311 (2011)68-76. [26] F.-Y. Jou, A. E. Mather, F. D. Otto, Can. J. Chem. Eng., 73 (1995) 140-147. [27] J. K. Carson, K. N. Marsh, A. E. Mather, J. Chem. Thermo, 32 (2000) 1285-1296. [28] H. Arsis, K. Ballerat-Busserolles, L. Rodier, J.-Y. Coxam, J. Chem. Eng. Data, 56 (2011) 3351-3362.
ip t
[29] C. Mathonat, V. Majer, A. E. Mather, J. P. E. Grolier, Ind. Eng. Chem. Res., 37 (1998) 4136-4141. [30] I. Kim, H. F. Svendsen, Ind. Eng. Chem. Res., 46 (2007) 5803-5809.
cr
[31] C. Mathonat, V. Majer, A. E. Mather, J. P. E. Grolier, Ind. Eng. Chem. Res., 37
(1998) 4136-4141.
us
[32] I. Kim, H. F. Svendsen, Ind. Eng. Chem. Res., 46 (2007) 5803-5809.
[33] C. Mathonat, V. Majer, A. E. Mather, J. P. E. Grolier, Ind. Eng. Chem. Res., 37 (1998) 4136-4141.
an
[34] I. Kim, H. F. Svendsen, Ind. Eng. Chem. Res., 46 (2007) 5803-5809. [35] Q. Xu, Ph. D. Dissertation, University of Texas, Austin, 2011. [36] Q. Xu, G. Rochelle, Energy Procedia, 4, (2011) 117-124.
M
[37] P. M. Mathias, S. Reddy, A. R. Smith, K. Afshar, “Thermodynamic Analysis of CO2
Capture Solvents” accepted for publication in Int. J. Greenhouse Gas. Contr., 2013
[38] Y. Zhang, C.-C. Chen, Ind. Eng. Chem. Res., 50 (2011) 163-175.
d
[39] J. Oexmann, J. Kather, Int. J. Greenhouse Gas Contr., 4 (1020) 36-43.
te
[40] F. A. Tobiesen, H. Svendsen, Ind. Eng. Chem. Res., 45 (2006), 2489-2496. [41] B. Oyenekan, Ph. D. Dissertation, University of Texas, Austin, 2011
Ac ce p
[42] P. M. Mathias K. Afshar , F. Zheng, M. D. Bearden, C. J. Freeman, T. Andrea, P. K. Koech, I. Kutnyakov, A. Zwoster, A. R. Smith, P. G. Jessop, O. Ghaffari Nik, D. J. Heldebrant, Energy & Environ. Sci., 6 (2013) 2233-2242. [43] J. Oexman, A. Kather, S. Linnenberg, U. Liebenthal, Greenhouse Gas Sci. Technol., 2 (2012), 80-98. [44] M. Born, Zietschrift für Physik, 1 (1920) 45. [45] J. G. Kirkwood, J. Chem. Phys., 2 (1934), 351-361.
Mathias – Applied Thermodynamics in CO2 Capture Process Technology - Fluid Phase Equilibria - 2013
19 Page 19 of 19