Purification of substances by a process of freezing and fractional melting under equilibrium conditions

Glasgow, Augustus R.; Ross, Gaylon S.

doi:10.6028/jres.057.017

Cited by 14 publications

(8 citation statements)

References 4 publications

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“…Freezing desalination process mainly depends on a seawater phase change process from the liquid phase to the solid phase "ice". In theory, most ice crystals contain pure water [9] and [10]. Hence, fresh water can be extracted from the formed ice after the complete freezing process while the salt is disposed as a high concentration brine.…”

Section: Introductionmentioning

confidence: 99%

Exergy and parametric analysis of freeze desalination with reversed vapor compression cycle

Elrahman

Abdo

Hussein

et al. 2020

Thermal Science and Engineering Progress

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Freezing desalination is one of the recent technologies that tries to contribute in water shortage problems. The idea of desalination by freezing is quite new and still needs more deep investigation for better understanding and proposing new enhancements in the system's technology. This paper aims to present exergy and parametric analysis for different operational parameters of a small-scale desalination by freezing unit working on a reversed vapor compression cycle. Operating parameters including freezing ratio, temperature and salt concentration are investigated. These parameters variations are critical to determine the working design parameters effects on the overall cycle performance. Salinity range from 5000 to 45000 ppm was tested using a heat pump of a C.O.P range from 3.8 to 8.2. Results showed that the energy consumption for this system range was 14.5 and 68.7, kWh per meter cube water production at 5000 and 45000 ppm, respectively. Exergy analysis showed that recovering larger quantities of the expelled brine is more efficient and useful due to more contributions in increasing the energy efficiency of the operating cycle. The proposed system proved to give higher thermal efficiency compared to alternative desalination systems such as reverse osmosis with membranes or flash systems. The system recorded a high thermal efficiency of 44% at 25 ̊ C and 50% icing ratio. The output results from the system analysis given in this paper could significantly help to implement an actual optimized desalination system working on a reversed vapor compression cycle.

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Section: Introductionmentioning

confidence: 99%

Exergy and parametric analysis of freeze desalination with reversed vapor compression cycle

Elrahman

Abdo

Hussein

et al. 2020

Thermal Science and Engineering Progress

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“…Finally nitrobenzene has been investigated as a typical substance with a large dipole moment. All compounds were distilled, dried with silica gel, and finally purified under vacuum conditions by the fractional melting technique [12]. The two samples analyzed for each compound (except 2-methylnaphthalene) represent the pure fraction and the reject fraction obtained by this technique.…”

Section: Results Of Purity Analysesmentioning

confidence: 99%

Chemical purity by dielectric cryometry

Ross¹,

Frolen²

1963

J. RES. NATL. BUR. STAN. SECT. A.

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A co ns ider at io n of th e defi ciencies in standa rd methods used for t he cr yometr ic clrt(' rmination of puri ty has led to a new a pproac h in w hi ch t he m eas uremen t of an in t('n siv(' r ath er t ha n a n extensive proper ty is t he contr ollin g fa ctor. This m ethod , m easu re men t of t h e di electri c con stan t as a fun ction of t he fractio n melted a nd correlation w ith t h e acco mpan y ing change in te mperature, allows calculat ion of puri ty w it h hi gh precision. Th e a pparat us used a nd ex perim en tal work p erform ed t o ascer ta in t he sco pe of t he m eth od a re desc ribed. Dete rmin at ion of puri ty fo r o rgani c co mpo nnds wit h differin g polari zabilities a nd dipol e moments indicate a rat her w id e a ppli ca bili ty o f t he m ethod . The la rge eha nge in t h e d ielectric co nstant of a hi gh p uri ty co mpoun d as it p asses fr o m solid t o liquid sta te, with a n acco mpa ny in g small chan ge in te mperature, may allow a u to matic con t rol of t emper at ure wit hin extre mely n a rrow limi ts . Cryometric MethodThe well-known m ethod or freezing poin L depression, (T Jo-TJ) -wh ere TJO is the freezing point of t he pure ma teri al and T J t hat or the ac tual sftmplepro vides a sensi ti\T e nond estructive m easure of impuri ties. In t his method a pb ysical proper ty, ~, is determined as a IuncLion of Lempera ture, Tx, in. the region or tbe liquid-solid transition . Th e liquid frac tion, F, is presumed to be a linear function or ~, tha t is:For nearly pure substances the gener alized van 't Hoff equation applies:1:,N t designates th e sum of the mole fractions of impuri ties soluble in th e liquid and insoluble in t he solid. Conventionally it is written N 2*' .6. H f is the molar h ea t of fusion of the pure m aterial. R is the gas constant. The factor .6.HJ/RTJo 2 is generally r eferred to as the cryoscopic constant, A, and (TfO -Tx) is equated to .6. T so tha t eq (2) can be written :Where N l* is the mole fraction of tb e major component. On r ewri ting (3) w e have the straight line r elationship : (4) Wh en F = l , Tx= Tf> the m el ting poin t of the sample by defini tion. When the line is extrapolated to F=O , Tx= TJo , so tha t by th ermodynamic t h eory applicable to dilute solu tions the m elting point of t he pure subs tance can be deri \'ed exp erimentally from a plot or ~ vcrsus T x. In practice cxp erimen ters of ten derive T fo by extn1.polation of Lh e hypcrboli::: r elation (3) to p=o.Presen. L ly t here exist Lhr ee widely used cryomeLric tcchniqu cs. In d ilatometry [1 , 2] 1 the sample volume is t he physical prop er ty~. Th e t wo other techniqucs eff ec Li vely depend Oll h eat con ten t . They ar e adiab atic calorimetry [3,4] and timetemperature (thermometric) fr eezin g cur vcs [5,6]. A car efully conducted comparison [7] h as shown tha L Lhc Lhree tec hniqu es, cach at i Ls b esL, can gi\Te r eliable r csul L. Th e chief acl\ran tage in t be caIOl'im etric approac h is Lbat 011 C direcLly ob tain s accurate values for hea ts of ...

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“…Previous investigations on purification by the fractional crystallization and melting process reported from the NBS [1] indicated that with some substances a major portion (about ¾) of the impurities is removed along with the first 20-percent fraction melted. The following successive 20-percent fraction melted removed about of the remaining impurities.…”

Section: Preparation Of the Samplesmentioning

confidence: 99%

“…A preliminary determination of the purity of the difluoro sample before purification gave 99.7 mole percent. With a starting material of this purity, the last 40-percent fraction melted was expected to be 99.95 mole percent pure if the efficiency reported in reference [1] were achieved.…”

Section: Preparation Of the Samplesmentioning

confidence: 99%

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Thermodynamic properties of some methylphosphonyl dihalides from 15 to 335 ÃƒÆ’Ã¢â‚¬Å¡Ãƒâ€šÃ‚Â°K

Furukawa¹,

Reilly²,

Piccirelli³

et al. 1964

J. RES. NATL. BUR. STAN. SECT. A.

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M eas ur em ents of t h e heat capac it y of mC't h y lph osp ho ny l di flu o ri de (CH , P OF2) , methylphospho nyl di chl o rid e (CI-I 3PO Cl,), and m ethylphospho ny l chlo ro flu o ri de (CH aPOC lF) " 'ere m a de fro m a bo ut 15 to 335 oK by m eans of an adi abat ic calorim C'ter. These hi g hl y react ive and toxic su bstances were pu rifi ed in a com pletely closed glass appa rat us b.v co mbini ng s low crysta ll izat ion a nd fractional m eltin g proced lll·C'S. TI1l' puri t ies dC't('l" min ed b~' t hr fr eezin g-e ur vc mf't hod a re s hown to be generall y in agrC'emc nt with t hosE' valu es ohtain C' c\ h. v t he calo r.imetri c m et hod. From t he r('s ults of t he Iwat, m eaSll re m (' nt~, t he t ri p le-point k mperatu rc, heat o f fu sio n, and t heir co rrespo nclin g est im ated un certai nties \\"('I'e foun d to bp, res pectively, 236.34 ± 0.05 oJ\: and 1I ,878 ± 12 J / mo le fo r CH 3POF 2, 306. Triple-point tC'mpe rat ures obtain ed b.v thp fr cez ing-cu rve me t hod a rc in ag rec m ent \\" ith t he above val lies. A tab le of smoothed values of heat capac ity, enthalpy, entha lp y fun ct io n, ent ropy, G ib bs fr ee ene rgy, and G ibbs frp e e nergy fun ct ion fl'om 0 to 335 OK was obtained from t he d ata. T he ent ropy a nd its co rrespondin g pst im ated unce rt.ainty fo r C H3P OF2, CH 3POC I2, and CH3P OC IF in t heir respcc tive condenspd phase at 298. 1.5 o J( a nd sat urat ion press ure \Vas fo und to be 208.3 ± 0.3, 164.8 ± 0.3 , a nd 216.4 ± 0.4 J /d pg mole, rcs pecti ve ly. The entropies in the gaseo us state fLt 298. 15 OK a nd 1 atm press ure "-ere found to be 312.7 ± 3, 339.7 ± 3, a nd 335.0 ± 3 J /deg mol e, respecti ve ly.

show abstract

Purification of substances by a process of freezing and fractional melting under equilibrium conditions

Cited by 14 publications

References 4 publications

Exergy and parametric analysis of freeze desalination with reversed vapor compression cycle

Exergy and parametric analysis of freeze desalination with reversed vapor compression cycle

Chemical purity by dielectric cryometry

Thermodynamic properties of some methylphosphonyl dihalides from 15 to 335 ÃƒÆ’Ã¢â‚¬Å¡Ãƒâ€šÃ‚Â°K

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