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1 he Univerity of Bradford Intitutional Repoitory hi work i made available online in accordance with publiher policie. Pleae refer to the repoitory record for thi item and our Policy Document available from the repoitory home page for further information. o ee the final verion of thi work pleae viit the publiher webite. Acce to the publihed online verion may require a ubcription. Link to original publihed verion: Citation: Cao W, Begg C and Mujtaba IM (2015) heoretical approach of freeze eawater dealination on flake ice maker utilizing LNG cold energy. Dealination. 355: Copyright tatement: 2015 Elevier B.V. Full-text reproduced in accordance with the publiher elf-archiving policy. hi manucript verion i made available under the CC-BY-NC-ND 4.0 licene

2 heoretical approach of freeze eawater dealination on flake ice maker utilizing LNG cold energy Wenheng Cao a,c,d, Clive Begg b, Iqbal M. Mujtaba b, * a College of Mechanical and Energy Engineering, Jimei Univerity, Xiamen , China b School of Engineering and Informatic, Univerity of Bradford, Wet Yorkhire, Bradford BD7 1DP, UK c Fujian Province Key Lab of Energy Cleaning Utilization and Development, Jimei Univerity, China d Cleaning Combution and Energy Utilization Reearch Center of Fujian Province, Jimei Univerity, China * Correponding author. addre: I.M.Mujtaba@bradford.ac.uk (Prof. I.M. Mujtaba). Abtract In thi work, a novel concept in freeze dealination (FD) wa introduced. Nowaday the total liquefied natural ga (LNG) production capacity ha reached 290 Megaton per year. It enormou cold energy releaed from re-gaification can be ued in the freeze dealination proce to minimize the overall energy conumption. A proce of FD on flake ice maker utilizing LNG cold energy wa deigned and imulated by HYSYS oftware. An ice bucket on flake ice maker wa choen a eawater crytallizer mainly due to it continuou ice making and removing ice without heat ource. A dynamic model of the freezing ection ha been developed and imulated through gproms oftware. he reult how that the conumption of 1 kg equivalent LNG cold energy can obtain about 2 kg of ice melt water. In addition, it i hown that the power conumption of thi LNG/FD hybrid proce i negligible. Keyword: Freeze dealination; Flake ice maker; LNG cold energy; Dynamic modeling; Ice growth Nomenclature Symbol Heat tranfer coefficient, W/m 2 K emperature, o C or K Heat conductivity coefficient, W/m K K Overall heat tranfer coefficient, W/m 2 K δ hickne of wall, m x hickne of ice layer, m Denity, kg/m 3 1

3 L Latent heat of ice, J/kg C Ma fraction of alt D Diameter, m u Velocity, m/ Kinematic vicoity, m 2 / Pr Prandtl number Q Heat load of flake ice maker, kw q Flow rate, m 3 / or kg/ c Specific heat, J/kg K h Specific enthalpy, J/kg Specific entropy, J/kg K Subcript c coolant or refrigerant eawater w wall i ice layer p particle NG natural ga LNG liquefied natural ga 1. Introduction Dealination i an important and effective way to mitigate water-hortage in many arid area around the world. According to the 24 th IDA (International Dealination Aociation) Worldwide Dealting Plant Inventory [1], the total capacity of completed dealination plant ha been reached m 3 /d by the end of It would be more ignificant to improve the capacity of a plant with higher productivity. Dealination i an energy-intenive indutry that not only deplete foil fuel, but alo reult in the emiion of greenhoue and other undeirable gae. Driving the proce by renewable energie i thu an important development goal, provided that the cot of the water produced can be maintained at an acceptably low level. hermal dealination procee can be driven by olar or geothermal heat ource, and electrically powered dealination procee have been coupled to wind turbine. However, thee renewable energy ource can be problematic, either becaue the energy denity produced i too low for dealination purpoe, or becaue it i 2

4 unteady, not to mention the additional maintenance and infratructure cot aociated with the ue of renewable energy ource [2]. Freeze dealination (FD) refer to the proce in which freh water i extracted by harveting and melting the ice crytal from the chilled feed (eawater or brackih water) [3]. In thi proce, the aline water i cooled and frozen under controlled condition. Almot all the alt i rejected by the ice crytal generated and a a reult, freh water can be obtained from the melted ice. heoretically, only about 1/7 of the energy required to boil a aline olution i needed for the freeze-melt proce [4]. In general, the FD proce (ee Fig. 1) conit of four tep: (a) pre-cooling of the feed brine, (b) crytallization of the ice crytal, (c) eparation of the ice crytal from the brine olution and (d) wahing and melting ice crytal to obtain high purity water. Feed Precooler Coolant in Crytallizer Brine/Ice Separator Ice Ice Waher & Melter Clean Water Coolant out Brine Fig. 1 Diagram of indirect contact freeze dealination (ICFD). While FD ha potential, it adoption a a dealination technology ha o far been very limited [3]. One reaon for thi i the ready availability of convenient foil fuel, uch a natural ga (NG), in countrie that rely heavily on dealination, with the reult that thermal dealination technologie tend to be favored. However, rather urpriingly, NG production alo ha the potential to facilitate the ue of FD. hi i becaue coniderable amount of wate cold energy are releaed during the re-gaification proce by which LNG i turned into NG. he cold energy refer to the heat aborption effect from the ambient environment that occur when LNG i re-gaified at the LNG terminal. LNG occupie only a fraction (1/600) of the volume of NG, making it much eaier to handle and tranport, with the NG tored in a liquid form at atmopheric preure at about 110 K. Hence, LNG mut be re-gaified before being utilized in it gaeou form, a proce that aborb about 837 KJ/Kg LNG from the urrounding [5]. Owing to the low temperature, high energy denity and blooming global LNG market, LNG cold energy i now recognized a a high quality energy ource with which to cool media [4]. At preent, there are 58 et of large-cale bae load LNG project built in the world, with the total LNG production capacity etimated to be 290 Megaton per year [6, 23]. he growth in LNG production capacity between 1964 and 2012 i illutrated in Fig. 2. 3

5 Fig. 2 LNG production capacity of built LNG project ( ) [6, 23] Fig. 3 how a propect of LNG production capacity of new-built and propoed LNG project between 2013 and By 2019, America will become the larget producer and exporter of LNG, overtaking Qatar currently ranked no. 1. Fig. 3 LNG production capacity of new-built and propoed LNG project ( onhore) [6, 23] Conidering the characteritic and mechanim of FD proce, thi ytem require large quantitie of high quality cold energy. For the FD proce, cold energy i needed to cool and crytallize the pre-cooled aline feed olution. he large amount of cold energy from re-gaification of LNG jut happen to meet the energy requirement of FD proce thereby minimizing the overall energy conumption. Although much reearched, the optimum technique for freezing and harveting ice during FD i not known. Over the year reearcher have invetigated a variety of technique. Chen et al. [7] developed two model of ice growth velocity in aqueou olution derived from an irreverible thermodynamic analyi and the conventional 4

6 heat and ma tranfer theory, debating with Ratkje and Fleland [8] on modelling the freeze concentration proce by irreverible thermodynamic. Shirai et al. [9] invetigated the effect of eed ice on formation of tube ice with high purity for a freeze watewater treatment ytem with a bubble-flow circulator. Chen et al. [10] experimentally tudied the patial uniformity of olute incluion in ice formed from falling film flow on a ub-cooled urface. Wakiaka et al. [11] experimentally explored the ice crytallization in a pilot-cale freeze watewater treatment ytem. Qin et al. [12] tudied the growth kinetic of ice in film preading along a ub-cooled olid urface. Zhao et al. [13] optimized the ice making period for ice torage ytem with flake ice maker. Rice and Chau [14] dicued freeze dealination uing hydraulic refrigerant compreor. William et al. [15] aeed an ice maker machine for dealting brine. Attia [16] propoed a new ytem for freeze water dealination uing auto revered R-22 vapor compreion heat pump. Rane and Padiya [17] tudied heat pump operated freeze concentration ytem with tubular heat exchanger for eawater dealination. Fujioka et al. [18] modeled and applied a progreive freeze-concentration for dealination. In thi tudy, a new concept wa introduced and the ue of LNG cold energy coupled with a freeze-melt proce to dealinate eawater wa invetigated, and a dynamic model to evaluate it potential a a dealination technology wa alo preented. 2. Flake ice maker In the preent tudy a ytem wa conidered, which utilized a flake ice maker, in which a rotary ice blade i ued to crape an ice layer off the ub-cooled urface of a cylindrical heat exchanger. Such machine tend to exhibit higher heat tranfer efficiencie compared with other methodologie, uch a the tube ice maker. hey are alo relatively imple and eay to operate. In particular, becaue the flake ice maker utilize a mechanical method to remove ice intead of hot ga defroting, there i no requirement for an additional heat ource. Flake ice maker (Figure 4) produce irregular flake ice with approximate ize 40mm 40mm and thickne range from 1.0mm to 2.5mm. hey are widely ued in indutry for controlling chemical reaction and concrete temperature cooling due to the large contact area employed. hey are alo widely employed to produce ice from eawater to cool and preerve fih. With repect to thi, eawater machine differ from the common flake ice maker, inomuch that all the part employed are 5

7 anti-corroive, with the compreor powerful enough to cool eawater to about -25 o C. 01-Motor, 02-Spiral evaporation pipeline, 03-Seawater upply inlet, 04-Reducer 05-Ice blade, 06-Water ditribution pan, 07-Main haft, 08-Water ditribution tube 09-Exit of water collection dih, 10-Inner wall of evaporator, 11-Inulation material 12-Ice torage bin, 13-Ice drop opening, 14-Outer hell Fig. 4 Schematic diagram of ice bucket on flake ice maker he ice flake machine comprie a cylindrical evaporator, on which the ice form. Seawater i trickled over the inner urface of thi evaporator, where it i rapidly cooled to form ice and at the ame time the alt ion i excluded from the ice crytal interface. he eawater i fed into a header tank above the evaporator, from which it i evenly prinkled onto the inner wall of the evaporator through a erie of ditribution tube. Any alty water not frozen i allowed to fall into a collection dih, from which it i thrown away. A hown in Figure 4, the ice i harveted by a rotating blade which cut through the ice layer on the inner wall of the evaporator, dilodging evenly-haped ice flake, which fall from the wall and pa out of the ice 6

8 drop opening at the bottom of the machine. 3. Utilization of LNG cold energy he FD proce utilizing LNG cold energy i illutrated in Figure 5, which how the relative arrangement of the refrigerant pump, the ice making evaporator, and the LNG exchanger. In the ytem the refrigerant i condened in the LNG heat exchanger, which perform a imilar role to the expanion valve in a conventional refrigerant ytem. Saturated LNG liquid enter the LNG exchanger, where it evaporate to form gaeou NG, a proce which involve aborbing heat from the gaeou refrigerant tream (2), which condene to form liquid refrigerant (3). he liquid refrigerant i then pumped to evaporator where it once again become gaeou, aborbing latent heat from the eawater, which freeze to form ice. Fig. 5 Proce of FD on flake ice maker utilizing LNG cold energy With the rapid rate at which heat i tranferred in the LNG heat exchanger, there i danger that olidification of the refrigerant might occur. Conequently, it would be neceary to employ a refrigerant, with a low operating temperature, uch a R410A, which i an environment-friendly, azeotropic mixture (50%/50%) of the refrigerant HFC-32 and HFC-125, and which ha a freezing point of -155 o C. 3.1 Simulation methodology he imulating calculation and ytem optimization wa carried out uing PR-wu equation of tate through HYSYS oftware [5]. PR-wu equation i one of the mot important Fluid Package utilized by HYSYS. he imulation aumed that the frehwater flow wa 150 L/h (daily output 3600 kg ice), and that the nominal evaporation temperature wa -25 o C (ee able 1 bold italic). Conidering the wah water (account for 10% of produced ice) and the concentration of eawater (uually taken a 2 time), the ice maker hould produce 167 kg/h ice [167 kg / h(100% 10%) 150 kg / h, equivalent to 150 L/h frehwater] o the eawater input rate wa L/ h, and the heat load Q of flake ice maker wa deduced by Q qc qil (1) 7

9 where q and q i are the flow rate of eawater and produced ice repectively (viz. 334L/h, 167kg/h), c i the pecific heat capacity of eawater (4017J/kg K), i the temperature drop of eawater cooling, and L i the latent heat of ice ( J/kg). After the precooling of the ice melting tank, the eawater temperature of the upply inlet (Figure 4-03) wa et to 2 o C, o 4 o C due to the eawater freezing point wa -2 o C. By uing the above data, Q can be calculated and equal 17 kw. 3.2 Reult by HYSYS he proce parameter including mole fraction of component are preented in table 1 and 2. he pump power wa only kw, which i the main energy conumption aociated with the LNG/FD proce. he following equation how about 2 kg ice melt water can be obtained at the cot of 1 kg equivalent of LNG cold energy. 150 kg / h kg / h ~ 167 kg / h kg / h where 150kg/h i the frehwater ma flow, 167kg/h i produced ice production, and 78.99kg/h i the LNG ma flow (ee able 1 bold italic). he key imulation reult were ummarized in table 3. able 1 Proce parameter Node No. emperature ( o C) Preure (kpa) Molar Enthalpy (J/mol) Molar Entropy (J/mol o C) Ma Flow (kg/h) Vapour Fraction e e e LNG e NG e able 3 Simulation reult Frehwater Ice LNG: Ice melt water Pump power 150 kg/h 167 kg/h 1 kg:2 kg kw 8

10 he matching of the curve between cold compoite (LNG tream) and hot compoite (refrigerant tream) can be een from the reult hown in Figure 6. he temperature difference between them i very large while LNG i in the two-phae flow tate. However, it narrow greatly with the rie in temperature of NG, once the phae-change i complete. hi change in temperature difference, accompanied by the reduction in heat tranfer, contribute to the energy lo in the heat exchanger. Fig. 6 Heat flow variation a a function of temperature in the pipeline of the LNG exchanger he heat tranfer rate at the evaporator i hown in Fig. 7. Fig. 7 Heat flow v. temperature in the piral evaporation pipeline of the flake ice maker According to the exergy loe equation (2) and the exergy efficiency equation (3) of the LNG heat exchanger E [ q ( ) q ( )] (2) lo 0 LNG NG LNG

11 q2( h2 h3 ) q20 ( 2 3) 100% q ( h h ) q ( ) LNG NG LNG LNG 0 NG LNG (3) where 0 i the ambient temperature, h i pecific enthalpy and i pecific entropy, the exergy analyi reult of the LNG Exchanger were: 17.65kW of exergy loe and 8.9% of exergy efficiency. 4. Dynamic model of freezing ection A chematic diagram of the freezing ection i hown in Fig. 8. Fig. 8 Schematic diagram of heat tranfer on a ub-cooled urface of the ice bucket [19] he freezing proce i characterized by a phae-change heat tranfer proce during a period of ice making. It can be conidered a a one-dimenion freezing proce. In thi heat tranfer model, there i a migrating interface between olid phae and liquid phae during the whole proce, and the latent heat of phae-change i releaed at thi interface (red line). he phae-change proce begin from x = 0, then the interface migrate along x axi and it poition i a function of time x (t). he dynamic mathematical model wa developed by applying conervation law of ma and heat to the variou phae and component of the freezing ection. However, in order to implify the olution of the equation it i neceary to make the following aumption concerning the nature of the proce: (a) he compoition and temperature of the liquid tream at the ame height were conidered to be the ame a the compoition C and temperature of the bulk liquid in the freezing ection. (b) Variation in denity, pecific heat, latent heat, heat conductivity coefficient 10

12 and heat tranfer coefficient, were conidered to be negligible over the temperature range of interet. (c) Crytal ize may be defined by a ingle dimenion and, for the purpoe of determining crytal ma, crytal are aumed to be pherical. he heat tranfer coefficient of the refrigerant ide wa given under the condition of forced flow [20] in the pipeline 0.8 c ud c c Pr d c 0.4 c (4) where d i the feature ize of the refrigerant channel and c, u c, c and Pr c are the heat conductivity coefficient, velocity, kinematic vicoity and Prandtl number of the refrigerant, repectively. Falling film flow on a ub-cooled urface can be regarded a the mode of the fluid of contant phyical propertie over the contant wall temperature plate [20]. So the overall heat tranfer coefficient on the eawater ide wa determined by: 0.5 uh Pr h 1 3 (5) where h i the feature ize of the ice bucket and, u, and Pr are the heat conductivity coefficient, velocity, kinematic vicoity and Prandtl number of the eawater, repectively. he overall heat tranfer coefficient of the whole proce i determined by four part, coniting of the refrigerant ide, the wall, the ice layer and the eawater ide. K 1 1 x 1 c w i (6) where δ and x are the thickne of wall and ice layer repectively, w and i are the heat conductivity coefficient of wall and ice layer repectively. In order to imulate the change in ice thickne with time, according to the law of conervation of energy, the relationhip between the four part of thermal reitance can be changed to i o i c x 1 x i c w i (7) 11

13 where i i the temperature of the migrating phae-change interface, o i the wall temperature, and c i the refrigerant temperature. During the time of dt, the ice layer grow the thickne of dx. he analyi of heat tranfer rate in thi dx ice layer i expreed i o i c dt dt Ldx i dt x 1 x i c w i (8) where i the denity of eawater, L i the latent heat of phae change (ice), and i the bulk temperature of eawater. he ice growth rate wa calculated a v i dx dt L 1 i c i x c w i (9) Crytal growth wa calculated from a thermal driving force relationhip [21] obtained from a dynamic heat balance on the olid phae. hi determined the rate of change of diameter D p of a ingle crytal with repect to the difference between the temperature i of the ice/liquid interface and temperature of the bulk liquid, according to ddp G i dt Dp (10) where G i a rate contant defined in term of a driving force ratio E a G E (11) and E i dependent on alt concentration C of the bulk liquid according to 1 E (12) 77C 1 1 C he ice/liquid interface temperature i i defined in term of the freezing temperature of eawater ued (271.7K). he nucleation rate i given a follow 12

14 2 R g B i Nu exp 2 P i (13) where R g i the ideal ga contant, P i Planck contant and B i an empirical contant which may be calculated by auming that Nu = 1 at nucleation. 5. Dicuion and reult by gproms Equation (4) to (13) define a et of differential and algebraic relationhip which may be employed for imulating the freezing ection of the flake ice maker. gproms model builder oftware [22] wa ued for model development and imulation. Data for the mathematical model have been obtained from the contructional dimenion of the pilot plant flake ice maker [19] and phyical propertie of brine and ice. hee data are preented in able 4, including the feed boundary input and the initial condition for the tart of a imulation experiment. he freezing ection i conidered to contain an initial falling film on a ub-cooled urface at feed temperature, void of ice, and urrounded by the piral evaporation pipeline where the refrigerant i fed through in order to tart the freezing proce and ubequent ice crytal formation. able 4 Data ued in dynamic modeling c Heat tranfer coefficient of refrigerant ide at c 1151 W/m 2 K c Feature temperature of refrigerant o C Heat tranfer coefficient of eawater ide at 612 W/m 2 K w Feature temperature of eawater Heat conductivity coefficient of wall Q235 0 o C 45 W/m K δ hickne of wall m i Heat conductivity coefficient of ice layer 2.33 W/m K Denity of eawater 1025 kg/m 3 L Latent heat of ice J/kg R g Ideal ga contant J/K mol P Planck contant J/ 13

15 B Nucleation rate equation empirical contant Boundary input. in Inlet temperature of brine 2 o C C Ma fraction of alt in brine feed Initial condition x hickne of ice layer 0.00 m D p Crytal mean diameter 0.00 m Figure 9 how the calculated variation of the thickne of the ice layer a the falling film flow and i cooled to freezing point. It can be een that although the thickne of the ice increae with time, it growth rate reduce exponentially (Figure 10). hi i due to the fact that the thermal reitance to heat tranfer increae with ice thickne, cauing the heat exchange efficiency to be reduced and the crytallization peed to low. How the ice growth rate and the overall heat tranfer coefficient change with time are hown in figure 10 and 11. hee how a rapid fall in the firt 180 econd followed by a gradual fall. hi ugget that in order to optimize the performance of the ice maker, it i important to harvet the ice before it become too thick, omething that perhap explain why in the actual proce, the ice bucket craper crape ice once every 48 econd, limiting the ice thickne to a maximum of 3mm. he reporting time interval of data point i 30 econd, imilarly hereinafter. Fig. 9 Variation of the ice layer thickne with time 14

16 Fig. 10 Variation of the ice growth rate with time Fig. 11 Variation of the overall heat tranfer coefficient of the whole proce with time he relationhip between ice growth rate and ice layer thickne i hown in Figure 12, a well a that of the overall heat tranfer coefficient v. ice layer thickne (Figure 13). Careful comparion between thee two graph reveal that the ice growth rate decreae more rapidly with increaed ice thickne, compared with the overall heat tranfer coefficient. 15

17 Fig. 12 Ice Growth Rate (m/) v. Ice Layer hickne (m) Fig. 13 Overall Heat ranfer Coefficient (W/m2K) v. Ice Layer hickne (m) Our analyi alo revealed that the variation of the ice layer thickne with time wa dependent on refrigerant temperature (Figure 14), with the rate of ice depoition decreaing a the temperature of the refrigerant increae. When c = o C, the growth rate of the ice layer wa the greatet, wherea when c = o C wa coniderably lower. 16

18 Fig. 14 Variation of the ice layer thickne veru time at different refrigerant temperature From the experimental data of eawater dealination on a flake ice maker in [19] hown in Figure 15, it i clear that the higher the refrigerant temperature i, the lower the pecific gravity of ice-melt water will be. hi ugget that the greater heat tranfer rate aociated with a lower refrigerant evaporating temperature, might not be beneficial when it come to the dealination of eawater. If the evaporator temperature i too low, then fater crytallization will occur, reulting in more alt becoming trapped in the ice. By comparion, when crytallization occur at a lower rate, the exudate become more aline and the ice purer. Fig. 15 Effect of refrigerant temperature on pecific gravity of ice-melt water [19] In Fig. 16, the variation of the ice layer thickne with time at different eawater temperature i preented. From thi it can be een that the growth peed of ice layer 17

19 increae with the fall of the temperature of the eawater. When = -1 o C, the growth peed of ice layer i the fatet, and when = 4 o C, the lowet. In the operating practice of flake ice maker, when the temperature of the eawater i higher than 2 o C, the ice layer can grow hardly. Fig. 16 Variation of the ice layer thickne veru time at different eawater temperature A oon a nucleation occur, crytal tart to form a hown in Fig. 17, which illutrate the variation of crytal particle diameter veru time for different ma fraction of alt in eawater feed. From thi it i clear that crytal particle grow fater when the eawater contain low concentration of alt. Fig. 17 Variation of crytal particle diameter veru time at different ma fraction of alt in brine feed In theory, the growth rate of ice crytal i not alway a traight-line, but a 18

20 parabolic curve, namely the growth rate of ice crytal low down with the increae of alt concentration. Becaue of the alt ion being excluded from the crytal interface, the alt concentration of the interface i higher than that of the olution, thu the temperature of freezing point of the interface i below the freezing temperature of correponding concentration of olution. Diffuion of ma tranfer in the proce of crytal growth i affected by the alt concentration of interface, and the freezing temperature difference of interface effect on the latent heat tranfer releaed by ice crytal. herefore, the higher the alt concentration i, the lower the heat tranfer and ma tranfer. he ice crytal growth rate decreae with the riing of alt concentration. 6. Concluion Here, a new idea of utilizing cold energy in LNG in freeze dealination i introduced, explained and modeled. A the LNG temperature i a low a -162 o C, the temperature difference would be too large for practical dealination if the cold energy were tranmitted directly to the water. herefore, an intermediate refrigerant i uggeted to tranfer the cold energy, while providing the mot uitable eawater crytallization temperature. he ice-making bucket of flake ice maker i elected a eawater crytallizer which ha advantage of high heat tranfer efficiency, continuou crytallization and removing ice without heat ource. he heat tranfer around ice bucket of the freeze dealination proce (Figure 5) i modeled uing gproms. he behavior of the freeze dealination of the ice bucket on flake ice maker utilizing LNG cold energy may be predicted from the reult obtained for the freezing ection o far a nucleation and growth of olid preent are concerned. Similarly, liquid behavior - their proce parameter with repect to the refrigerant circulated around the freezing ection and LNG flow through the heat exchanger - i predicted. he calculation how that the conumption of 1 kg equivalent of LNG cold energy can obtain about 2 kg of ice melt water. From the energy conumption calculation preented, the LNG/FD hybrid proce i found to cot power almot equal to zero. Acknowledgement he author i extremely grateful to the Univerity of Bradford, a well a the 2013 Viiting Scholar Program of Fujian Province in China, which upported the 19

21 author (conferred the title of Honorary Viiting Academic) to reearch at the Univerity of Bradford. hi paper wa financially upported by the Huang Huizhen Dicipline Contruction Foundation of Jimei Univerity (ZC ) and echnology Project of Fujian Provincial Department of Education (JA12191). hi work wa alo upported by the echnology Project of State Adminitration of Work Safety ( ). Reference [1] (acceed 9 th May 2014) [2] Rizzuti, L, Ettouney HM, Cipollina, A olar dealination for the 21 t century, NAO Security through Science Secrie C: Environmental Security, Springer, [3] Rahman MS, Ahmed M, Chen XD, Freezing melting proce and dealination: review of preent tatu and future propect, Int. J. Nuclear Dealination 2 (2007) [4] Peng Wang, ai-shung Chung, A conceptual demontration of freeze dealination-membrane ditillation (FD-MD) hybrid dealination proce utilizing liquefied natural ga (LNG) cold energy, Water Reearch 46 (2012) [5] Wen-heng Cao, Xue-heng Lu, Wen-heng Lin, An-zhong Gu, Parameter comparion of two mall-cale natural ga liquefaction procee in kid-mounted package, Applied hermal Engineering 26 (2006) [6] LNG Journal November/December [7] Xiao Dong Chen, Ping Chen, Kevin W. Free, A note on the two model of ice growth velocity in aqueou olution derived from an irreverible thermodynamic analyi and the conventional heat and ma tranfer theory, J. Food Eng. 31 (1997) [8] Signe Kjeltrup Ratkje, Ola Flelandb, Modelling the freeze concentration proce by irreverible thermodynamic, J. Food Eng. 25 (1995) [9] Y. Shirai, M. Wakiaka, O. Miyawaki, S. Sakahita, Effect on eed ice on formation of tube ice with high purity for a freeze watewater treatment ytem with a bubble-flow circulator, echnical Note 33 (1999) [10] Ping Chen, Xiao Dong Chen, Kevin W. Free, An experimental tudy on the patial uniformity of olute incluion in ice formed from falling film flow on a ub-cooled urface, J. Food Eng. 39 (1999) [11] Minato Wakiaka, Yohihito Shirai, Shigeru Sakahita, Ice crytallization in a pilot-cale freeze watewater treatment ytem, Chemical Engineering and Proceing 40 (2001) [12] Frank G.F. Qin, Xiao Dong Chen, Mohammed M. Farid, Growth kinetic of ice film preading on a ubcooled olid urface, Separation and Purification echnology 39 (2004) 20

22 [13] J.D. Zhao, N. Liu, Y.M. Kang, Optimization of ice making period for ice torage ytem with flake ice maker, Energy and Building 40 (2008) [14] Warren Rice, David S.C. Chau, Freeze dealination uing hydraulic refrigerant compreor, Dealination 109 (1997) [15] P.M. William, M. Ahmad, B.S. Connolly, Freeze dealination: An aement of an ice maker machine for dealting brine, Dealination 308 (2013) [16] Ahmed A.A. Attia, New propoed ytem for freeze water dealination uing auto revered R-22 vapor compreion heat pump, Dealination 254 (2010) [17] M.V. Rane, Y.S. Padiya, Heat pump operated freeze concentration ytem with tubular heat exchanger for eawater dealination, Energy for Sutainable Development 15 (2011) [18] Ryouke Fujioka, Li Pang Wang, Gjergj Dodbiba, oyohia Fujita, Application of progreive freeze-concentration for dealination, Dealination 319 (2013) [19] Meibin Huang, Reearch of eawater dealination technology with LNG cold energy utilization, Mater Diertation of Shanghai Jiao ong Univerity, [20] Wenquan ao, Heat tranmiion cience, Pre of Northwetern Polytechnical Univerity [21] N. Akhtar, L. McGrath, P.D. Robert, Dynamic modelling and partial imulation of a pilot cale column crytallizer, Dealination 28 (1979) [22] gproms. [23] Gailing Bai, Preent ituation and development trend of natural ga liquefaction technology, Conference of natural ga purification, liquefaction, torage and utilization technology and equipment, 2011 China. 21

23 able 2 Mole fraction of compoition Node Phae HFC-32 HFC-125 N 2 CH 4 C 2 H 6 C 3 H 8 ic 4 H 10 nc 4 H 10 ic 5 H 12 nc 5 H 12 C 6 H 14 C 7 H 16 1 Liquid Vapour Liquid LNG Liquid NG Vapour