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Energies 2015, 8(9), 10354-10369; doi:10.3390/en80910354

Article
Design of an Extractive Distillation Column for the Environmentally Benign Separation of Zirconium and Hafnium Tetrachloride for Nuclear Power Reactor Applications
1
School of Chemical Engineering, Yeungnam University, Gyeongsan 712-749, Korea
2
School of Environment, Science and Engineering, Southern Cross University, Lismore 2480, New South Wales, Australia
*
Author to whom correspondence should be addressed.
Academic Editor: Hiroshi Sekimoto
Received: 24 July 2015 / Accepted: 12 September 2015 / Published: 21 September 2015

Abstract

: Nuclear power with strengthened safety regulations continues to be used as an important resource in the world for managing atmospheric greenhouse gases and associated climate change. This study examined the environmentally benign separation of zirconium tetrachloride (ZrCl4) and hafnium tetrachloride (HfCl4) for nuclear power reactor applications through extractive distillation using a NaCl-KCl molten salt mixture. The vapor–liquid equilibrium behavior of ZrCl4 and HfCl4 over the molten salt system was correlated with Raoult’s law. The molten salt-based extractive distillation column was designed optimally using a rigorous commercial simulator for the feasible separation of ZrCl4 and HfCl4. The molten salt-based extractive distillation approach has many potential advantages for the commercial separation of ZrCl4 and HfCl4 compared to the conventional distillation because of its milder temperatures and pressure conditions, smaller number of required separation trays in the column, and lower energy requirement for separation, while still taking the advantage of environmentally benign feature by distillation. A heat-pump-assisted configuration was also explored to improve the energy efficiency of the extractive distillation process. The proposed enhanced configuration reduced the energy requirement drastically. Extractive distillation can be a promising option competing with the existing extraction-based separation process for zirconium purification for nuclear power reactor applications.
Keywords:
zirconium tetrachloride; hafnium tetrachloride; nuclear power reactor; extractive distillation; molten salt; heat pump; environmentally benign separation

1. Introduction

Nuclear power has emerged as a reliable baseload source of electricity providing approximately 13% of the world’s electrical power [1]. Nuclear energy is an important resource in managing atmospheric greenhouse gases and associated climate change with its overwhelmingly low carbon emission considering that energy generation accounts for 66% of worldwide greenhouse gas emissions [1,2,3].

Zirconium (Zr) alloy (or Zircaloy2) has many useful properties for applications in nuclear facilities, such as low absorption cross-section of thermal electrons, high ductility, good fabricability, hardness, and corrosion resistance [4,5]. Therefore, these alloys are used widely as cladding and guide tubes in pressurized water-cooled reactors. For nuclear reactor applications, the existence of hafnium (Hf), which can be found in zirconium ore at 1–3 wt%, should be avoided because of its high thermal neutron cross section. Owing to their similar physical and chemical properties with almost identical ionic radii (0.074 mm for Zr4+, 0.075 mm for Hf4+), the separation of these elements is a challenge, leading to many intricate processing steps for producing Hf-free Zr in commercial nuclear reactor applications. In particular, a purification step is one of the core and harshest steps to determine the required Zr purity.

Because the tetrachlorides are the preferred compounds used in the reduction reactions for the production of Zr and Hf in a metallic form, extensive efforts have focused on the separation of HfCl4 and ZrCl4 [6,7,8,9]. Extraction is still the most popular and economic way for commercial Zr-Hf purification [10,11,12,13,14,15,16]. On the other hand, regardless of its main virtue in mass production, the extraction-based Zr-Hf separation requires considerable amounts of relatively expensive, corrosive and environmentally harmful solvent chemicals. A large portion of the entire processing facility for the production of Zr and Hf metals is dedicated to handling a multiple-step solvent extraction process in the presence of a solvent. Furthermore, it also generates a huge volume of liquid waste, which is difficult to dispose of due to stringent environmental protection laws [17,18,19,20]. For example, isobutyl methylketone (MIBK), which is the most popular solvents used for Zr-Hf extraction, requires environmentally harmful cyanogen (CN) chemicals as an additive. These drawbacks of extraction-based separation have prompted research into the development of an environmentally benign technology to separate HfCl4 and ZrCl4.

Distillation has attracted considerable attention for Zr purification because of its potential for clean separation and many other advantages for a large scale production, such as fewer unit operations and chemical consumption, higher overall yield, and less effluent [17,18]. On the other hand, because distillation utilizes the volatility difference of the components associated with the vapor-liquid equilibrium (VLE), the close boiling points of ZrCl4 and HfCl4 with narrow and harsh conditions for the vapor-liquid phase existence limits the distillation applications: a large number of separation stages are required in the column to bring HfCl4 to an acceptably low level; stringent temperature control and a confining pressure are needed to manage the VLE; and the column material must withstand high temperatures and pressures. Note that ZrCl4 and HfCl4 are solids at normal temperatures and sublime when heated under normal pressure. The physical properties of these components are described elsewhere [21].

The extractive distillation technique can be an attractive alternative to overcome these limitations of conventional distillation, while still having advantages in distillation applications. A eutectic mixture of HfCl4 and ZrCl4 in certain fused salts is potentially useful for this purpose. Fused salts for extractive distillation should have some important properties, such as high solubility for ZrCl4 and HfCl4 at elevated temperatures, low vapor pressure, low viscosity, and high dissolution for many different materials [22]. In addition, the lowest operating temperature of the column must be higher than the sublimation temperature of HfCl4 at atmospheric pressure [22]. Several candidate solutions have been described [23,24,25,26].

In this study, the feasibility of extractive distillation using molten salts was examined to separate ZrCl4 and HfCl4 for nuclear power reactor applications. The experimental data was chosen from the literature, and correlated with the Raoult’s law-type behavior model. The optimal design of extractive distillation column and its enhanced configuration was studied with its main design condition using a rigorous commercial process simulator, Aspen HYSYS, and their performance was compared with conventional distillation.

2. Vapor–Liquid Equilibrium Model for ZrCl4 and HfCl4 Mixture over Molten Salts

An alteration in the volatility of ZrCl4 and HfCl4 by adding a solvent is desired in view of their close vapor pressures. The essential parameters that should be considered for the design of extractive distillation are (i) the selection of a suitable solvent to dissolve the tetrachlorides; (ii) the operating temperature and pressure; and (iii) a reliable material of construction. Regarding these parameters, several molten salts have been recommended for extractive distillation [27].

The volatility of HfCl4 over a HfCl4-KCl-NaCl solution is approximately 1.7 times larger than that of ZrCl4 over the ZrCl4-KCl-NaCl solution in the range, 63.0~67.5 mol% tetrachlorides (HfCl4-ZrCl4) [22], which indicates the economic separation of HfCl4 and ZrCl4 by extractive distillation in a molten salt solution. In addition, the molten salt mixture of NaCl-KCl has preferential properties in that a homogeneous solution can be formulated at a relatively low temperature and the liquid phase exists over a reasonably wide range of compositions at atmospheric pressure [22]. Note that a system with tetrachlorides only requires an exceedingly high pressure and higher temperature as well as a very narrow range of vapor-liquid phase.

This study targeted the molten salt mixture, 66.0 mol% tetrachlorides (ZrCl4-HfCl4) and 34.0 mol% salts (NaCl-KCl, 8:29 molar). The experiment results for this molten salt mixture showed that the molten salt system selected can be melted completely and consists of a liquid and vapor phase in the temperature range, 304 °C to 410 °C [28].

For the design of an extractive distillation column, the vapor-liquid phase equilibrium behavior of the tetrachloride mixtures in the selected molten salt homogeneous solution needs to be known. To build up a proper vapor-liquid phase equilibrium model of the tetrachlorides in the selected molten salt mixture, the experimental data was taken from [28], and correlated with Raoult’s law-type behavior with the Antoine vapor pressure model. For simplicity, the system was assumed to be a binary mixture composed of two hypothetical components: ZrCl4 with the molten salts (i.e., ZrCl4-KCl-NaCl component) and HfCl4 with the molten salts (i.e., HfCl4-KCl-NaCl component). Raoult’s law was chosen by considering the expected ideal solution behavior of the liquid phase due to the structural similarity and the ideal gas behavior under the low-pressure conditions. The extended Antoine equation [29] was chosen for a rigorous prediction of the hypothetical component vapor pressure. The Antoine equation coefficients of each hypothetical component were then obtained by non-linear regression by minimizing the absolute average deviations between the predicted and experimental results for the total vapor pressure. The experimental data for the total vapor pressure was taken at the bubble point temperature, which consists only of the vapor or liquid phase. Note that in the experiment [28], the amounts of ZrCl4 and HfCl4 varied for the different runs, whereas the total composition of ZrCl4 and HfCl4 was maintained at 66.0 mol% in the salt system.

The resulting Antoine equations for the hypothetical ZrCl4 and HfCl4 components are as follows:

ln P Z r C l 4 ( hypothetical ) = 16.1133 7636.14 11.8568 + T + 0.0260 × ln T + 0.4131 × T 4.8211    for 577 K <  T  < 683 K, 23 kPa <  P  < 223 kPa
ln P H f C l 4 ( hypothetical ) = 13.4190 7950.47 7.3530 + T + 0.6022 × ln T 0.9490 × T 3.0828     for 577 K <  T  < 683 K, 23 kPa <  P  < 223 kPa
where P and T denote the vapor pressure in kPa and temperature in K, respectively.

Figure 1 compares the predicted and experimental results of the total pressure for various compositions and temperatures. The total pressure predicted by Raoult’s law with the extended Antoine equation showed good agreement with the experimental values.

Figure 1. Comparison of the predicted and experimental results of the total pressure for different ZrCl4 compositions in the molten salt system (34.0 mol% NaCl and KCl (8:29 M); 66.0 mol% ZrCl4 and HfCl4).
Figure 1. Comparison of the predicted and experimental results of the total pressure for different ZrCl4 compositions in the molten salt system (34.0 mol% NaCl and KCl (8:29 M); 66.0 mol% ZrCl4 and HfCl4).
Energies 08 10354 g001 1024

Table 1 lists the experimental data of the total pressure used for regression and the values predicted from the regression model. The resulting absolute average deviation (AAD) defined by Equation (3) was a small enough value of 4.15%, which indicates satisfactory prediction ability of the regression model for design purposes.

% A A D = 1 N i = 1 N | p i , pre p i , exp p i , exp | × 100
where N is the number of experimental data.

Table 1. Experimental and predicted total pressure for the different ZrCl4 composition in the molten salt system (34.0 mol% NaCl and KCl (8:29 M); 66.0 mol% ZrCl4 and HfCl4).
Table 1. Experimental and predicted total pressure for the different ZrCl4 composition in the molten salt system (34.0 mol% NaCl and KCl (8:29 M); 66.0 mol% ZrCl4 and HfCl4).
Composition of ZrCl4, mol% (Salt-Free Basis)Temperature (°C)Pressure (mmHg)
Experiment [28]Predicted
28.92383.714081410
38915681555
375.912201218
346.2730675
354.6830802
362.5935939
360.51070903
378.212401272
37010801088
362.4968937
354.3832797
346.4680678
338.1602569
354.6792802
369.810351083
352.3690765
329.6478473
320.4405386
320.3395385
304.9275270
54.74353.1693705
385.813051296
385.812751299
401.216531692
393.614541485
405.617971821
394.314421503
386.912741325
377.311121112
361.3832821
40617641851
361.8841829
353.9723710
354659711
337.9500513
321.8359363
305246249
305.5219252
354.3716716
304.8230248
72.91388.912951247
375.91040989
388.912751247
395.514351399
3761040991
329.5405399
318.9323318
328.5400391
351.3615621
376970991
3779501009
389.312501256
38912321250
395.813801406
376950991
351.3590621
328.6402391
316.8295304
80.83382.811491072
390.513051226
398.514551406
403.215501521
398.314331401
390.413001224
390.812721232
383.811171091
367810805
358.8713690
359.1700694
351617594
342.9515507
334.8425430
325.5360355
317285296
308.9240248
93.19402.514051390
397.812501286
404.714551440
409.816721564
398.913451310
378.8964929
370.8795806
363.3687703
354.9565601
345.8452505
331363376
315.2217270
361.8640684
369.6750789
377.4860907
385.810101050
394.311251223
402.413151387
370715795
344.8440495
345.5435502
328.9300361
303.9170211

Figure 2 shows a P-x diagram of the molten salt system. The linear dependency of the total pressure to the liquid composition validates Raoult’s law for a molten salt system. Figure 3 shows the T-x-y diagram of the molten salt system for different pressures. The predicted bubble point curves by Raoult’s law showed good agreement with the experimental data. The relatively wide region between the bubble and dew point curves also indicates the favorable properties of extractive distillation for the separation of HfCl4 and ZrCl4 in a molten salt solution.

Figure 2. P-x diagram of the molten salt system (34.0% NaCl and KCl (8:29 M); 66.0 mol% ZrCl4 and HfCl4).
Figure 2. P-x diagram of the molten salt system (34.0% NaCl and KCl (8:29 M); 66.0 mol% ZrCl4 and HfCl4).
Energies 08 10354 g002 1024
Figure 3. T-x-y diagram of the molten salt system (34.0% NaCl and KCl (8:29 M); 66.0 mol% ZrCl4 and HfCl4).
Figure 3. T-x-y diagram of the molten salt system (34.0% NaCl and KCl (8:29 M); 66.0 mol% ZrCl4 and HfCl4).
Energies 08 10354 g003 1024

3. Optimal Design of Extractive Distillation Column

To examine the feasible separation of ZrCl4 and HfCl4 for nuclear power reactor applications, a design study of the extractive distillation column was carried out for the molten salt system, 66.0 mol% tetrachlorides (ZrCl4-HfCl4) and 34.0 mol% salts (NaCl-KCl). A rigorous commercial simulator, ASPEN HYSYS 8.4, was used to simulate and design the extractive distillation column. Based on the vapor-liquid equilibrium behavior of the ZrCl4 and HfCl4 mixture over the molten salts, as discussed in the previous section, a modified ANTOINE fluid package model [30] was selected from the Aspen HYSYS property library to simulate the vapor–liquid equilibrium and thermodynamic properties of the molten salt system. The modified ANTOINE fluid package model employs Raoult’s law for the vapor-liquid equilibrium behavior and Lee-Kesler model for the enthalpy calculation. The Antoine equation coefficients obtained from the regression were embedded into the modified ANTOINE fluid package model. Table 2 lists the main properties of the two hypothetical components evaluated from the simulator.

Table 2. Physical properties of the hypothetical ZrCl4 and HfCl4 components over the molten salt system (34.0 mol% NaCl and KCl (8:29 M); 66.0 mol% ZrCl4 and HfCl4) estimated from Aspen HYSYS.
Table 2. Physical properties of the hypothetical ZrCl4 and HfCl4 components over the molten salt system (34.0 mol% NaCl and KCl (8:29 M); 66.0 mol% ZrCl4 and HfCl4) estimated from Aspen HYSYS.
PropertiesZrCl4HfCl4
Eutectic point (°C)218234
Acentricity factor1.1261.383
Critical Point
Temperature (°C)406.4421.9
Pressure (bar)21.1520.15
Volume (mL/mol)658.1699.8

Based on the Hf impurity in the natural state, a crude zirconium feed mixture of 23401.5 kg/h consisting of 98.4 wt% ZrCl4 and 1.6 wt% HfCl4 (salt-free basis), was assumed for the column design [9,31]. The column was designed to obtain an ultra-purified ZrCl4 with less than 40 ppm HfCl4 impurity and more than 85% ZrCl4 recovery (salt-free basis). The column was also assumed to be operated at atmospheric pressure. In the extractive distillation column, a ZrCl4 rich molten salt product was obtained from the bottom and the HfCl4 impurities were removed from the top of the column. For optimal design of the column, the column was initially set up using a short-cut column design facility to obtain an initial estimate for the required number of trays and the reflux ratio. The column was then simulated rigorously to determine the optimal design conditions.

For optimization of the column structure, the number of stages was varied while keeping the product specifications. Figure 4 presents the reboiler duty as the number of stages in the column.

Based on the sensitivity analysis, the optimal number of trays in the column was selected to be 75. In addition, the column was designed with a maximum flooding of 80% to prevent flooding in the column. To determine the maximum flooding of a particular column, the rating mode was simulated using the column internal specifications. A high reflux ratio was required to achieve the design specifications, which resulted in a somewhat high reboiler duty as 62.4 W per 1 kg/h Zr production. Figure 5 presents a flow sheet of the resulting extractive distillation column along with its main design condition. All the composition and flow rates shown in Figure 5 were based on a salt free basis. Note that HfCl4 and ZrCl4 dissolve in the molten salt as being the overhead and bottom products, respectively.

Figure 4. Sensitivity analysis between the number of stages and the reboiler duty for the molten salt extractive distillation column.
Figure 4. Sensitivity analysis between the number of stages and the reboiler duty for the molten salt extractive distillation column.
Energies 08 10354 g004 1024
Figure 5. Optimal design of extractive distillation column the molten salt system (34.0% NaCl and KCl (8:29 M); 66.0 mol% ZrCl4 and HfCl4).
Figure 5. Optimal design of extractive distillation column the molten salt system (34.0% NaCl and KCl (8:29 M); 66.0 mol% ZrCl4 and HfCl4).
Energies 08 10354 g005 1024

The bottom stream with high purity ZrCl4 molten salt was then run through a stripper column to collect ZrCl4 as a solid product and the solvent salt was returned to the feed storage [32,33,34]. The HfCl4-rich liquid comes off the overhead stream and is then collected in a HfCl4 stripper unit to obtain the salt-free HfCl4. The main drawback of the extractive distillation approach is that it requires these post treatment units for the removal of the solvent salt from the tetrachlorides, which might give a rise to significant cost. Several approaches for the removal of the solvent salt from the tetrachlorides are described elsewhere [24].

The highly corrosive solvent nature might also have an impact on the selection of the material. Therefore, the corrosion effect is another important consideration in all such molten salt systems; thus, reducing the operation temperature and avoiding the use of excess molten salt is important. This also provides lower operating costs and allows the use of less expensive construction materials. Generally, the construction material should be chosen considering the high temperature and corrosion phenomenon. In the present study, Zr cladding was recommended for enduring the high temperature and corrosion condition in an economic manner [35,36]. Furthermore, a fuel furnace should be used as the high temperature generation source to boil up the bottom section of the column. Simultaneously, in view of economic advantage, the latent heat from the top vapor condensation can be utilized to generate high-pressure steam.

4. Enhanced Configuration by Heat-Pump Assisted Self-Heat Integration Technique

Heat pump technology, which allows use of the heat of condensation released at the condenser for evaporation in the reboiler, is an economic way to conserve energy when the temperature difference between the overhead and bottom of the column is small enough and the heat load is high [35]. A heat pump on the top of the column does not change the vapor and liquid traffic inside the column. The methods used widely are the top vapor recompression, closed cycle heat pump and bottom flashing heat pump. Many studies have been developed to improve the heat pump technology for different applications [37,38,39]. The heat pump can be used both in grassroots or retrofitting designs because they are easy to introduce and plant operation is normally simpler than other heat integration cases [40]. In this study, the focus was mainly on the feasibility of the enhanced heat pump-assisted configuration by partial bottom flashing [9,41,42]. Figure 6b presents the resulting flow sheet of the extractive distillation applying the heat pump technique, comparing with the conventional distillation [9] (Figure 6a).

Figure 6. Schematic diagram of (a) conventional distillation [9] and (b) enhanced extractive distillation configuration using a partial bottom flashing heat pump.
Figure 6. Schematic diagram of (a) conventional distillation [9] and (b) enhanced extractive distillation configuration using a partial bottom flashing heat pump.
Energies 08 10354 g006 1024

The bottom column outlet stream can be divided into two streams, where one stream is the bottom product of high purity ZrCl4 and another stream is expanded in a valve to decrease its temperature, which allows heat exchange with the top stream in a heat exchanger. This heat exchanger enables boiling the bottom column outlet stream and condensing the top column outlet stream. After the heat exchanger, the bottom stream must be recompressed to the column pressure using a compressor. This stream is finally recycled to the bottom section of the column. In the present study, the pressure ratio of the compressor was selected at 1.37 to obtain a minimum approach in the heat exchanger of 10 °C. Simultaneously, a reboiler needs to produce the remaining boil-up. As a result, the use of a partial bottom flashing heat pump reduced the energy requirement in the condenser and reboiler duty significantly by 60.0% and 69.2%, respectively, compared to the case without a heat pump. The required energy consumption was reduced to 30.6 W per 1 kg/h Zr production, which is equivalent to a 51.0% reduction. Table 3 provides a comparative summary of the key results.

Table 3. Comparison of different distillation approaches for ultra-purification of Zr-Hf tetrachlorides.
Table 3. Comparison of different distillation approaches for ultra-purification of Zr-Hf tetrachlorides.
Column specification and performanceConventional distillation [9]Extractive distillationHeat pump assisted extractive distillation
Number of stages1557575
Column diameter (m)0.852.02.0
Column temperature * (°C)463.3375.1375.1
Column pressure * (bar)32.01.121.12
Compressor duty (kW)-0.0222.8
Condenser duty (kW)17371117447.2
Reboiler duty (kW)17641222376.1
Condenser duty saving (%)-35.774.2 (60.0)
Reboiler duty saving (%)-30.778.7 (69.2)
Total energy saving (%)-33.270.1 (55.3)

* Based on the column bottom; numbers in brackets are the savings compared to extractive distillation.

The performance of the proposed extractive distillation columns was compared with the conventional distillation column [9], as shown in Table 3. The proposed extractive distillation columns with and without a heat pump reduced the energy requirements by 70.1% and 33.2%, respectively, compared to the conventional distillation column approach. This result also showed that the proposed extractive distillation approach has many advantages over the conventional distillation for ultra-high purity Zr-Hf separation: milder design and operating conditions, such as a smaller number of theoretical stages, lower operating temperature and atmospheric operating pressure.

5. Conclusions

The feasibility of extractive distillation using molten salt was examined for the environmentally benign separation of ZrCl4 and HfCl4 for nuclear power reactor applications. Raoult’s law with the extended ANTOINE vapor pressure model predicted the total vapor pressure of ZrCl4 and HfCl4 over the molten mixture of NaCl-KCl. Adding a proper molten salt mixture leads to the increase in the relative volatility of ZrCl4 and HfCl4. This also allowed milder pressure and temperature conditions as well as a wider range for vapor–liquid phase existence for distillation applications.

The optimal design of the extractive distillation column was carried out on the molten salt system (34.0% NaCl and KCl (8:29 M); 66.0 mol% ZrCl4 and HfCl4) through a rigorous simulation to obtain an ultra-purified ZrCl4 of less than 40 ppm HfCl4 and more than 85% ZrCl4 recovery. The resulting extractive distillation column showed many preferential properties for commercial separation, such as relatively mild operating temperatures, atmospheric operation pressures and smaller number of required stages. This also required lower energy requirement for separation: 33.2% energy saving was achieved compared to the conventional distillation case. An enhanced configuration by a heat-pump-assisted self-heat integration was also proposed to enhance the energy efficiency. The proposed heat-pump-assisted configuration achieved a significant decrease in the net energy requirement: a 70.1% energy saving was achieved compared to the conventional distillation case.

Extractive distillation using a proper molten salt system can be a promising option as an environmentally benign and economically effective way of obtaining ultra-purified Zr separation for nuclear power reactor applications, with a high potential of competing with an existing commercial separation process using extraction technology.

Acknowledgments

This research was supported by the 2014 Yeungnam University Research Grant. This study was also supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2015R1D1A3A01015621), and by Priority Research Centers Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2014R1A6A1031189).

Author Contributions

Le Quang Minh carried out the main job of modeling and design of the column and equilibrium model. Nguyen Van Duc Long aided the enhanced configuration design. Pham Luu Trung Duong and Youngmi Jung aided the equilibrium model and column simulation. Alireza Bahadori advised column design. Moonyong Lee conceived the core concepts for the research and advised academically. All authors collaborated in the preparation, revisions, and general editing of this manuscript.

Conflicts of Interest

The authors declare no conflict of interest.

Symbols

PPressure
TTemperature
xLiquid mole fraction of component i
yVapor mole fraction of component i

Abbreviation

MIBKIsobutyl methylketone
VLEVapor-liquid equilibrium
AADVapor-liquid equilibrium

References

  1. Chu, S.; Majumdar, A. Opportunities and challenges for a sustainable energy future. Nature 2012, 488, 294–303. [Google Scholar] [CrossRef] [PubMed]
  2. Arunachalam, V.S.; Fleischer, E.L. The global energy landscape and materials innovation. MRS Bull. 2008, 33, 264–276. [Google Scholar] [CrossRef]
  3. Tanaka, N. World Energy Outlook 2008; International Energy Agency: Paris, France, 2008; p. 211. [Google Scholar]
  4. Zinkle, S.J.; Was, G.S. Materials challenges in nuclear energy. Acta Mater. 2013, 61, 735–758. [Google Scholar] [CrossRef]
  5. Kratochvílová, I.; Škoda, R.; Škarohlíd, J.; Ashcheulov, P.; Jäger, A.; Racek, J.; Taylor, A.; Shao, L. Nanosized polycrystalline diamond cladding for surface protection of zirconium nuclear fuel tubes. J. Mater. Process. Technol. 2014, 214, 2600–2605. [Google Scholar] [CrossRef]
  6. Brun, P.; Guerin, J. Process for Introducing Zirconium Tetrachloride, Hafnium Tetrachloride and Mixtures Thereof into a Column for the Continuous Extractive Distillation under Pressure of Said Chlorides. U.S. Patent 4917773, 17 April 1990. [Google Scholar]
  7. Lee, E.D.; McLaughlin, D.F. Molten Salt Scrubbing of Zirconium or Hafnium Tetrachloride. U.S. Patent 4913778, 3 April 1990. [Google Scholar]
  8. Taghizadeh, M.; Ghanadi, M.; Zolfonoun, E. Separation of zirconium and hafnium by solvent extraction using mixture of TBP and Cyanex 923. J. Nucl. Mater. 2011, 412, 334–337. [Google Scholar] [CrossRef]
  9. Minh, L.Q.; Kim, G.M.; Park, J.K.; Lee, M.Y. Bubble point measurement and high pressure distillation column design for the environmentally benign separation of zirconium from hafnium for nuclear power reactor. Korean J. Chem. Eng. 2015, 32, 30–36. [Google Scholar] [CrossRef]
  10. Fischer, W.; Chalybaeus, W. Die trennung des hafnium vom zirconium durch verteilung. Z. Anorg. Allg. Chem. 1947, 255, 79–100. [Google Scholar] [CrossRef]
  11. Sato, T.; Watanabe, H. The extraction of zirconium(IV) from sulfuric acid solutions by long-chain aliphatic amines. J. Inorg. Nucl. Chem. 1974, 36, 2585–2589. [Google Scholar] [CrossRef]
  12. Benedict, M.; Pigford, T.H.; Levi, H.W. Nuclear Chemical Engineering; McGraw-Hill: New York, NY, USA, 1981. [Google Scholar]
  13. Schrotterova, D.; Nekovar, P.; Mrnka, M. Extraction of zirconium(IV) from sulfuric acid solutions with amines and mathematical simulation of extraction processes. J. Radioanal. Nucl. Chem. 1991, 150, 325–333. [Google Scholar] [CrossRef]
  14. Da-silva, A.; El-ammouri, E.; Distion, P.A. Hafnium/zirconium separation using Cyanex 925. Can. Metall. Q. 2000, 39, 37–42. [Google Scholar] [CrossRef]
  15. Taghizadeh, M.; Ghasemzadeh, R.; Ashrafizadeh, S.N.; Saberyan, K.; Ghanadi, M. Determination of optimum process conditions for the extraction and separation of zirconium and hafnium by solvent extraction. Hydrometallurgy 2008, 90, 115–120. [Google Scholar] [CrossRef]
  16. Banda, R.; Lee, M.S. Solvent extraction for the separation of Zr and Hf from aqueous solutions. Sep. Purif. Rev. 2014, 44, 199–215. [Google Scholar] [CrossRef]
  17. Palko, A.A.; Ryan, A.D.; Kuhn, D.W. The vapor pressures of zirconium tetrachloride and hafnium tetrachloride. J. Phys. Chem. 1958, 62, 319–322. [Google Scholar] [CrossRef]
  18. Vinarov, I.V. Modern methods of separating zirconium and hafnium. Russ. Chem. Rev. 1967, 36, 522. [Google Scholar] [CrossRef]
  19. Ishikuza, H. Process for Separation of Zirconium-Hafnium Tetrachlorides from A Mixture Comprising Such Chlorides and Apparatus Therefor. European Patent 45270, 3 February 1982. [Google Scholar]
  20. Tricot, R. The metallurgy and functional properties of hafnium. J. Nucl. Mater. 1992, 189, 277. [Google Scholar] [CrossRef]
  21. Denisova, N.D.; Safronov, E.K.; Pustil’nik, A.I.; Bystrova, O.N. Boundary liquid-vapor curve and saturated vapor pressure of ZrCl4 and HfCl4. Russ. J. Phys. Chem. 1967, 41, 30. [Google Scholar]
  22. Kim, J.D.; Spink, D.R. Vapor pressure in systems NaCl-KCl(8:29 M)-ZrCl4 and NaCl-KCl(8:29 M)-HfCl4. J. Chem. Eng. Data 1974, 19, 36. [Google Scholar] [CrossRef]
  23. Megy, J.A.; Freund, H. The separation of Zirconium and Hafnium in a molten salt-molten zinc system. Metallurg. Mater.Trans. B 1979, 10, 413–421. [Google Scholar] [CrossRef]
  24. Mallikarjunan, R.; Sehra, J.C. Pyrometallurgical processes for the separation of hafnium from zirconium. Bull. Mater. Sci. 1989, 12, 407. [Google Scholar] [CrossRef]
  25. Delons, L.; Picard, G.; Tigreat, D. Method for Separating Zirconium and Hafnium Tetrachlorides with the Aid of a Melted Solvent. U.S. Patent 6929786 B2, 16 August 2005. [Google Scholar]
  26. Niselson, L.A.; Egor, A.E.; Chuvilina, E.L.; Arzhatkina, O.A.; Fedorov, V.D. Solid-liquid and liquid-vapor equilibria in the Zr(Hf)Cl4-KAlCl4 systems: A basis for the extractive distillation separation of zirconium and hafnium tetrachlorides. J. Chem. Eng. Data 2009, 54, 726–729. [Google Scholar] [CrossRef]
  27. Sathiyamoorthy, D.; Shetty, S.M.; Bose, D.K.; Gupta, C.K. Pyrochemical separation of zirconium and hafnium tetrachlorides using fused salt extractive distillation process. High Temp. Mater. Proc. 1999, 18, 213. [Google Scholar] [CrossRef]
  28. Kim, J.D.; Spink, D.R. Total pressure of ZrCl4 and HfCl4 over Melts of NaCl-KCl(8:29 M)-ZrCl4-HfCl4 systems. J. Chem. Eng. Data 1975, 20, 173–178. [Google Scholar] [CrossRef]
  29. Antoine, C. Tensions des vapeurs: Nouvelle relation entre les tensions et les températures. Comptes Rend. 1888, 107, 681–684. [Google Scholar]
  30. Aspen Technology, Inc. Aspen Physical Property System, Version Number: V8.4; Aspen Technology, Inc.: Bedford, MA, USA, 2013. [Google Scholar]
  31. Bromberg, M.L. Purification of Zirconium Tetrachlorides by Fractional Distillation. U.S. Patent 2852446, 16 September 1958. [Google Scholar]
  32. Spink, D.R. Separation of Zirconium and Hafnium. U.S. Patent 3966458, 29 June 1976. [Google Scholar]
  33. Besson, P.; Guerin, J.; Brun, P.; Bakes, M. Process for the Separation of Zirconium and Hafnium Tetrachlorides from Mixtures Thereof. U.S. Patent 4021531, 3 May 1977. [Google Scholar]
  34. Spink, D.R.; Jonasson, K.A. Separation of HfCl4 and ZrCl4 by fractional distillation. In Extractive Metallurgy of Refractory Metals; Sohn, H.Y., Carlson, O.N., Smith, J.T., Eds.; The Metallurgical Society of AIME: Warrendale, PA, USA, 1981; pp. 297–314. [Google Scholar]
  35. Chawla, S.L.; Gupta, R.K. Material Selection for Corrosion Control; ASM International: Materials Park, OH, USA, 1993; pp. 271–272. [Google Scholar]
  36. Richardson, T. Shreir’s Corrosion: Volume 3: Corrosion and Degradation of Engineering Materials; Elsevier: Manchester, UK, 2010; pp. 2127–2134. [Google Scholar]
  37. Kiss, A.A.; Landaeta, S.J.F.; Ferreira, C.A.I. Towards energy efficient distillation technologies—Making the right choice. Energy 2012, 47, 531–542. [Google Scholar] [CrossRef]
  38. Jana, A.K. Advances in heat pump assisted distillation column: A review. Energy Convers. Manag. 2014, 77, 287–297. [Google Scholar] [CrossRef]
  39. Tsai, H.L. Design and evaluation of a photovoltaic/thermal-assisted heat pump water heating system. Energies 2014, 7, 3319–3338. [Google Scholar] [CrossRef]
  40. Long, N.V.D.; Lee, M.Y. A novel NGL (natural gas liquid) recovery process based on self-heat recuperation. Energy 2013, 57, 663–670. [Google Scholar] [CrossRef]
  41. Chew, J.M.; Reddy, C.C.S.; Rangaiah, G.P. Improving energy efficiency of dividing-wall columns using heat pumps, organic Rankie cycle and Kalina cycle. Chem.Eng.Process. 2014, 76, 45–59. [Google Scholar] [CrossRef]
  42. Waheed, M.A.; Oni, A.O.; Adejuyigbe, S.B.; Adewumi, B.A.; Fadare, D.A. Perfomance enhancement of vapor recompression heat pump. Appl. Energy 2014, 114, 69–79. [Google Scholar] [CrossRef]
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