CA1069427A - Process and apparatus for the freeze concentration of solutions - Google Patents
Process and apparatus for the freeze concentration of solutionsInfo
- Publication number
- CA1069427A CA1069427A CA256,896A CA256896A CA1069427A CA 1069427 A CA1069427 A CA 1069427A CA 256896 A CA256896 A CA 256896A CA 1069427 A CA1069427 A CA 1069427A
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- crystals
- mother liquor
- refrigerant
- solution
- crystallizable
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Abstract
ABSTRACT
The invention is directed to freeze concentra-tion of liquid mixtures including solutions by the direct contacting in at least two stages, of the mix-ture with a miscible refrigerant. After the con-tacting of the refrigerant with the liquid mixture, there is provided a first stage crop of substantially pure crystals of a mixture component which is separa-ted from the mother liquor. The mother liquor is then further cooled and crystallized in further stages.
Any crystals from said further stages are returned to the first or proceeding stage. This concentrates the second stage and further stage mother liquors.
This process is applicable to the freeze concen-tration of juices, coffee or tea extracts and beers.
It also may be utilized for the purification or bra-ckish water. The purity Or the first stage crystals is assured by controlled crystal growth. The successive stages provide for a complete concentration of the residual matter in the mother liquor. When the residual matter in the mother liquor is the desired product, it is recovered in very concentrated form. Should the crystals from the first stage be the desired product, their high degree of purity is advantageous.
The invention is directed to freeze concentra-tion of liquid mixtures including solutions by the direct contacting in at least two stages, of the mix-ture with a miscible refrigerant. After the con-tacting of the refrigerant with the liquid mixture, there is provided a first stage crop of substantially pure crystals of a mixture component which is separa-ted from the mother liquor. The mother liquor is then further cooled and crystallized in further stages.
Any crystals from said further stages are returned to the first or proceeding stage. This concentrates the second stage and further stage mother liquors.
This process is applicable to the freeze concen-tration of juices, coffee or tea extracts and beers.
It also may be utilized for the purification or bra-ckish water. The purity Or the first stage crystals is assured by controlled crystal growth. The successive stages provide for a complete concentration of the residual matter in the mother liquor. When the residual matter in the mother liquor is the desired product, it is recovered in very concentrated form. Should the crystals from the first stage be the desired product, their high degree of purity is advantageous.
Description
~;9~7 ~LD-O~ TH~ ~NV~NTION
This inventlon relates to the P~eeze concen~ratlon and separation of materials in and from their solutions and ~olven~s in a minimum of two s~eps or stages. More particularly this invention relates to such proces~es and apparatus whereby the solvent is frozen from the solution by the cooling action resulting fro~ ~he evaporation o~ B high-vapor pressure, low-boiling liqu~d coolant or refrigerant.
~ :`"
BACKGROUND 0~ THE IN~ENTION
In prior processes for obtalning concentrates by freeze concentration~ up to 50% o~ the contained water could be easily elim~na~ed.
It has been commercially di~ficult to ellminate the additional water.
; .
~ ' ' ' ~ . .
. : , ~ ~ ~
', ',,' .
3, :: : :
' ' ' ' " ~ ~. , , ' ., ~ .... .. .
'7 The exceed~ngly h~gh concentratlon o~ sugar and other sub-stances always produced increasingly smaller crystals (mlcroc~ystals) which are difficult to separate in a 8atisfactory manner. Where it was economic to separate such micro-crystals, they carried down9 by adsorption, much of the raw lnitial feedstock. The resultant losseg made it uneconom~cal to con-centrate the product beyond the 50% concentration.
The Yiscoslty of the concentrate also contlnuously ~ncreased until the mother liquor~ could no longer be economically and/or convenlently pumped.
To avoid eithe~ o~ both of these problems~ most installat~ons operate in t~o sèparate unit operat~ons i.e. they concentrate ~he initial material by a freeze-crystallization process and ~hen they sub~ect this concentrate to other concentration means i.e. hlgh vacuum evaporation by the thin wall method, spray drying, cryo~drying and even high-surface area di-ffusion processes. These subsequent unlt operat~ons utilize much energy, require highly sophisticated equ~pment and~ unless the final products are e~tr~mely ~aluable (drugs~g are generally uneconomical.
In most of these secondaryGconcentration procedures, the feed~tock3 are heated to some e~tent in order to evaporate the resldual water.
Thls heating step results in ~ome 108~ 0~ aro2a and the vitamins are often dest20yed by oxidation. In practice the oxid~tion of other labile components, ~n in fruit iuice~, c~nn~t be a~olded.
.
i ,.' ''~ . ,.
` ~ 3 ~ -.' ' . '~ ' ' ,' " : ' . . ,' ~'` . ' ' ' ,' ' ' ., , ', ' ' .
., , ~ . . . .
As a result, several ~a~ed systems have been employed for the final concentration operation which aim at the recovery of the lost aroma.
In general these have not been completely effective.
It has been an ob~ect of thi6 lnvention to find a procesR
which is not subJect to the abo~e mentioned disadvantages.
Many crystalllzation methods are directed at re~oving the more readily crystallizable ~ractions by cooling and thus concentrating the other components and/or even purify~ng them through the elimination of ~he crystallizable diluents or impurlties. ~any of the known methods are based upon sn indirect cooling o~ the llquid ~n sultable container8. ~fter the desired low temperature has been obtaln~ and the crystalli~ation of the more readily crystalli~able components is achie~ed~ the nex~ step consists in the separation of the cry~tals ~rom the mother liquor by standsrd means such as filter presses, centrifuges, or screw-expellers and other suitable liquid-solid separating apparatus. ~ .
In these known methods$ the crystals are separated f~o~
the llquid in scraper-coolers, w~th indirect contact between the liquld `
and the refrigeran~ or coolant via the cooled surfaces. The crystals form on the wall tha~ i8 at a low temperature and hence the crystal adheres thereto ar~d mnst be scraped o~f. The~e method~ have three prlmary dlsadvantages:
,. ~ .' ~ . -; ~
., , .
.
- . ~ , . , .-il 06942'7 a) the crystals are comminuted du~ing removal;
b) impurities arise as a result of the mechanical wear of the scraper and the scraped sur~aces; ~
c) interruptions in the psocess often occur due ~Q clogging of the separation apparatus by ~he comminuted crystals.
~ ew processes based upon direct coollng~ where the refrlgerant is contacted with the ~eedstock in a co-current or counter-current manner, have not as yet been economically practical. These newer processes generally require that the specific gra~lties o~ ~he refrlgerant, the ~eedstock and ;
the crystals must dif~er in order to be able to achieve a sui~able separation in the subsequent separstions steps. Furthermore, they requlre that the refrigeratlng fluid be imiscible ~ith the crystalllzable substances. To achieve good separation o the crystals~ substantial equipment investment is required and such operations must be carried out ~ith great care in order to produce crystals of proper size to avoid difficulties in separatlon.
In following the teaching herein particularly high con-centrations may be achieYed with low energy consumptlon and a hlgh degree of purity and crystal selectivity.
,, :, ...
~ 5 ;-., '' ~(~4'~7 High concent~at~on~ o~ such ~eedstock materials as ~ru~t~uice can be obtained by the use of freeze concentration ~lone, thereby preventing 10~9 of aroma~ loss of taste or destruction of vitamins.
The psocess descr~bed fos concentrating feedstock mixtures includes the steps of introducing such mi~tures of components including ~
crystall~zable sol~ents snd/or crystalll~able or amorphous solutes into a ;
first contact column or vessel. The feedstock mixtures are then cooled to a first ~tage temperature below the free~ing po~nt of a first crystallizable ~raction or c~mponent. The cool~ng 18 accompllshed by in~ecting and expanding into the feedstock a low-boiling~ high vapor pre3~ure, liquid refrigerant that i~ mlscible with said mixture. The cooling to the ~rst s~age tempera-ture is ad~uæted by regulat~ng the pressure i~ the vessel9 the amount and xate of rerigerant being ln~eeted ~nto the veæsel and the feed rate of the feedstock mixture thereto. 5uch adJustment and regulation provldes a first c~ystallizable fraction or component which cryæ~allize~ in a subætantially pure crystalline form, principally due to the lo~ solute concentration existing ~n the f~rst stage. `
Thls f~rst crystalli~a~le fraction or co~po~ent in the orm ;
of c~ystal~ iæ Qeparated ~rom the mother liquor. ¦
- 6 _ - ~
: . : , . .
-;., ~ . - . . ~, : -.: .
~69~
This mother liquor comp~ises the 8t~11 ll~u~d components of the mixture and any un~aporized quantities o~ llquld refrlgerant. The a~ount of un-vaporized refrigerant is controlled by the regulated temperature and pressure in the first contact ~essel.
The separated crystals are removed from the mother liquor and washed. The separated mother liquor ls then transferred into at least one further contac~ vessel. In the one or ~urther con~act ~essels, the mothe~ liquor i8 cooled to temperatu~e~, each respectively ~uccessively below the first temperature in the first contact ~essel. These further cooling s~ages of the mother liquor a~e acco~pl~shed by in~ectlng and expanding additional llquid refrigerant lnto said further contact vessels.
As a rasult of the said further cooling of the trans~erred motller llquor ~n said further successive stages9 succesfiive slursie6 Q~ crystals of the remaining crystallizable fractlons or components occur and successively greater amounts of other crystalli~able componen~s o~ the ~eedstock ~orm in mixture with further concentrated mother liquors wh~ch may contain s~ccessively additlonal unvaporized llquid amounts o~ refrigeran~. The additional liqui refriger~nt assists 1n maintalning the ~l~idl~y of the mother llquo~.
These successlve slurrie3 of crystals and other crys~alli~able components are each separated from ~he successively more conce~trated mother , liquors.
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,' ~ 7 ~ ~
. . .. ' - ' ': ` . , ' '' ~ . '. :' . ,. . ,~ ": ' ' , -~ - ~-,, , s~æ~
Any adhered mother liquo~ ~y be ~ashed ~om these succe6sl~ely ~ormed crystals. The successi~ely separated crys~als are melted and are recycled either to the preceding contact vessel or to ~he flrst contact vessel.
The concentrated mother liquor in the la~t of said ~uccessive contact vessels ls stripped of all un~aporl~ed rerigerant in order to recover and recycle it. The stripped final mother llquor is recovered as the final concentrate or product. The crystals separated from the first contact stsge which are ln substantially pure form, are also recoverable.
It i8 possible to recycle a ~raction of the successive mother llquor obtained after the separation the cry~als to the same s~age contact vessel in order to ad~ust the crystal concentration of the slurry within qaid vessel to permit proper crystal growth with ~inimal adsorbed impurities.
It is also possible ~o melt the separated crystals from each successive s~age in heat exchange relationship between the crystals and the recycled recompressed refrigerant so as to condense the compressed refrigerant to the liquid state.
While it is prefer~ed generally to u~e a liquld refrigerant whlch is completely miscible wlth the Peedstock mixtures and the mother liquors, the refrigerant may also be partlally or completely iDsoluble in said dissol~ed ~ixtures.
..
'-: ~ ~. . - - ' .
. ~ . .
101~42'7 An advantage o~ such mlsc~bil~y and solubil~t~ is that ~uccessively increasing amounts o~ liquid re~rigerant may be included ln the successive mother liquors in order to malntain these successive mother liquor6 and their components in a deslred ~tage of solubillty, fluldity, viscosity and to control the crystalli~atlon of many o~ the crystalllzable component~ at the tempera~ures within said contact ~essels.
When the liquid refrlgerant is soluble in the ~eedstock mixtures, the solute6 remain dissol~ed in the re~r~gerant and it is thus pos~ible to aehleve a replacqmen~ o~ the crystallized solvent component by the llquid refrigerant. The liq~d refrigerant 18 subseq~ently stripped to yield the concentrated solutes.
Generally, the concent~ated feedstoc~s to which the proce~s i~ directed are the li~uid solutions including fruit Juices, fermented fruit ~uices, beers, milk and brackish wa~ers havlng a major crys~allizable solvent component. These generally are concentrated to yield concentrates 9 came~tible or potable materlals. However, the proces~ is not llmlted thereto a~ it ~an also serve to recover and concentrate other valuable materials ~r~m thair solu~ions or mixtures by freeze concentratlon by removal of cry~tallizable ccmponents of said ~olutions.
This inventlon relates to the P~eeze concen~ratlon and separation of materials in and from their solutions and ~olven~s in a minimum of two s~eps or stages. More particularly this invention relates to such proces~es and apparatus whereby the solvent is frozen from the solution by the cooling action resulting fro~ ~he evaporation o~ B high-vapor pressure, low-boiling liqu~d coolant or refrigerant.
~ :`"
BACKGROUND 0~ THE IN~ENTION
In prior processes for obtalning concentrates by freeze concentration~ up to 50% o~ the contained water could be easily elim~na~ed.
It has been commercially di~ficult to ellminate the additional water.
; .
~ ' ' ' ~ . .
. : , ~ ~ ~
', ',,' .
3, :: : :
' ' ' ' " ~ ~. , , ' ., ~ .... .. .
'7 The exceed~ngly h~gh concentratlon o~ sugar and other sub-stances always produced increasingly smaller crystals (mlcroc~ystals) which are difficult to separate in a 8atisfactory manner. Where it was economic to separate such micro-crystals, they carried down9 by adsorption, much of the raw lnitial feedstock. The resultant losseg made it uneconom~cal to con-centrate the product beyond the 50% concentration.
The Yiscoslty of the concentrate also contlnuously ~ncreased until the mother liquor~ could no longer be economically and/or convenlently pumped.
To avoid eithe~ o~ both of these problems~ most installat~ons operate in t~o sèparate unit operat~ons i.e. they concentrate ~he initial material by a freeze-crystallization process and ~hen they sub~ect this concentrate to other concentration means i.e. hlgh vacuum evaporation by the thin wall method, spray drying, cryo~drying and even high-surface area di-ffusion processes. These subsequent unlt operat~ons utilize much energy, require highly sophisticated equ~pment and~ unless the final products are e~tr~mely ~aluable (drugs~g are generally uneconomical.
In most of these secondaryGconcentration procedures, the feed~tock3 are heated to some e~tent in order to evaporate the resldual water.
Thls heating step results in ~ome 108~ 0~ aro2a and the vitamins are often dest20yed by oxidation. In practice the oxid~tion of other labile components, ~n in fruit iuice~, c~nn~t be a~olded.
.
i ,.' ''~ . ,.
` ~ 3 ~ -.' ' . '~ ' ' ,' " : ' . . ,' ~'` . ' ' ' ,' ' ' ., , ', ' ' .
., , ~ . . . .
As a result, several ~a~ed systems have been employed for the final concentration operation which aim at the recovery of the lost aroma.
In general these have not been completely effective.
It has been an ob~ect of thi6 lnvention to find a procesR
which is not subJect to the abo~e mentioned disadvantages.
Many crystalllzation methods are directed at re~oving the more readily crystallizable ~ractions by cooling and thus concentrating the other components and/or even purify~ng them through the elimination of ~he crystallizable diluents or impurlties. ~any of the known methods are based upon sn indirect cooling o~ the llquid ~n sultable container8. ~fter the desired low temperature has been obtaln~ and the crystalli~ation of the more readily crystalli~able components is achie~ed~ the nex~ step consists in the separation of the cry~tals ~rom the mother liquor by standsrd means such as filter presses, centrifuges, or screw-expellers and other suitable liquid-solid separating apparatus. ~ .
In these known methods$ the crystals are separated f~o~
the llquid in scraper-coolers, w~th indirect contact between the liquld `
and the refrigeran~ or coolant via the cooled surfaces. The crystals form on the wall tha~ i8 at a low temperature and hence the crystal adheres thereto ar~d mnst be scraped o~f. The~e method~ have three prlmary dlsadvantages:
,. ~ .' ~ . -; ~
., , .
.
- . ~ , . , .-il 06942'7 a) the crystals are comminuted du~ing removal;
b) impurities arise as a result of the mechanical wear of the scraper and the scraped sur~aces; ~
c) interruptions in the psocess often occur due ~Q clogging of the separation apparatus by ~he comminuted crystals.
~ ew processes based upon direct coollng~ where the refrlgerant is contacted with the ~eedstock in a co-current or counter-current manner, have not as yet been economically practical. These newer processes generally require that the specific gra~lties o~ ~he refrlgerant, the ~eedstock and ;
the crystals must dif~er in order to be able to achieve a sui~able separation in the subsequent separstions steps. Furthermore, they requlre that the refrigeratlng fluid be imiscible ~ith the crystalllzable substances. To achieve good separation o the crystals~ substantial equipment investment is required and such operations must be carried out ~ith great care in order to produce crystals of proper size to avoid difficulties in separatlon.
In following the teaching herein particularly high con-centrations may be achieYed with low energy consumptlon and a hlgh degree of purity and crystal selectivity.
,, :, ...
~ 5 ;-., '' ~(~4'~7 High concent~at~on~ o~ such ~eedstock materials as ~ru~t~uice can be obtained by the use of freeze concentration ~lone, thereby preventing 10~9 of aroma~ loss of taste or destruction of vitamins.
The psocess descr~bed fos concentrating feedstock mixtures includes the steps of introducing such mi~tures of components including ~
crystall~zable sol~ents snd/or crystalll~able or amorphous solutes into a ;
first contact column or vessel. The feedstock mixtures are then cooled to a first ~tage temperature below the free~ing po~nt of a first crystallizable ~raction or c~mponent. The cool~ng 18 accompllshed by in~ecting and expanding into the feedstock a low-boiling~ high vapor pre3~ure, liquid refrigerant that i~ mlscible with said mixture. The cooling to the ~rst s~age tempera-ture is ad~uæted by regulat~ng the pressure i~ the vessel9 the amount and xate of rerigerant being ln~eeted ~nto the veæsel and the feed rate of the feedstock mixture thereto. 5uch adJustment and regulation provldes a first c~ystallizable fraction or component which cryæ~allize~ in a subætantially pure crystalline form, principally due to the lo~ solute concentration existing ~n the f~rst stage. `
Thls f~rst crystalli~a~le fraction or co~po~ent in the orm ;
of c~ystal~ iæ Qeparated ~rom the mother liquor. ¦
- 6 _ - ~
: . : , . .
-;., ~ . - . . ~, : -.: .
~69~
This mother liquor comp~ises the 8t~11 ll~u~d components of the mixture and any un~aporized quantities o~ llquld refrlgerant. The a~ount of un-vaporized refrigerant is controlled by the regulated temperature and pressure in the first contact ~essel.
The separated crystals are removed from the mother liquor and washed. The separated mother liquor ls then transferred into at least one further contac~ vessel. In the one or ~urther con~act ~essels, the mothe~ liquor i8 cooled to temperatu~e~, each respectively ~uccessively below the first temperature in the first contact ~essel. These further cooling s~ages of the mother liquor a~e acco~pl~shed by in~ectlng and expanding additional llquid refrigerant lnto said further contact vessels.
As a rasult of the said further cooling of the trans~erred motller llquor ~n said further successive stages9 succesfiive slursie6 Q~ crystals of the remaining crystallizable fractlons or components occur and successively greater amounts of other crystalli~able componen~s o~ the ~eedstock ~orm in mixture with further concentrated mother liquors wh~ch may contain s~ccessively additlonal unvaporized llquid amounts o~ refrigeran~. The additional liqui refriger~nt assists 1n maintalning the ~l~idl~y of the mother llquo~.
These successlve slurrie3 of crystals and other crys~alli~able components are each separated from ~he successively more conce~trated mother , liquors.
`; ~' , '.
,' ~ 7 ~ ~
. . .. ' - ' ': ` . , ' '' ~ . '. :' . ,. . ,~ ": ' ' , -~ - ~-,, , s~æ~
Any adhered mother liquo~ ~y be ~ashed ~om these succe6sl~ely ~ormed crystals. The successi~ely separated crys~als are melted and are recycled either to the preceding contact vessel or to ~he flrst contact vessel.
The concentrated mother liquor in the la~t of said ~uccessive contact vessels ls stripped of all un~aporl~ed rerigerant in order to recover and recycle it. The stripped final mother llquor is recovered as the final concentrate or product. The crystals separated from the first contact stsge which are ln substantially pure form, are also recoverable.
It i8 possible to recycle a ~raction of the successive mother llquor obtained after the separation the cry~als to the same s~age contact vessel in order to ad~ust the crystal concentration of the slurry within qaid vessel to permit proper crystal growth with ~inimal adsorbed impurities.
It is also possible ~o melt the separated crystals from each successive s~age in heat exchange relationship between the crystals and the recycled recompressed refrigerant so as to condense the compressed refrigerant to the liquid state.
While it is prefer~ed generally to u~e a liquld refrigerant whlch is completely miscible wlth the Peedstock mixtures and the mother liquors, the refrigerant may also be partlally or completely iDsoluble in said dissol~ed ~ixtures.
..
'-: ~ ~. . - - ' .
. ~ . .
101~42'7 An advantage o~ such mlsc~bil~y and solubil~t~ is that ~uccessively increasing amounts o~ liquid re~rigerant may be included ln the successive mother liquors in order to malntain these successive mother liquor6 and their components in a deslred ~tage of solubillty, fluldity, viscosity and to control the crystalli~atlon of many o~ the crystalllzable component~ at the tempera~ures within said contact ~essels.
When the liquid refrlgerant is soluble in the ~eedstock mixtures, the solute6 remain dissol~ed in the re~r~gerant and it is thus pos~ible to aehleve a replacqmen~ o~ the crystallized solvent component by the llquid refrigerant. The liq~d refrigerant 18 subseq~ently stripped to yield the concentrated solutes.
Generally, the concent~ated feedstoc~s to which the proce~s i~ directed are the li~uid solutions including fruit Juices, fermented fruit ~uices, beers, milk and brackish wa~ers havlng a major crys~allizable solvent component. These generally are concentrated to yield concentrates 9 came~tible or potable materlals. However, the proces~ is not llmlted thereto a~ it ~an also serve to recover and concentrate other valuable materials ~r~m thair solu~ions or mixtures by freeze concentratlon by removal of cry~tallizable ccmponents of said ~olutions.
2~
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" , - .. .. . - : ... .,. . ~ . ... .
;9~
Generall~, the ~e~r~ge~nt~cooling agent is selected from .
~he group of low boiling hlgh-~P~or pressure refrlgerants havlng a hlgh caloric equivalent of heat o~ Yaporlzation selected ~ro~ the gxoup consisting of 6aturated and unsaturated alipha~ic hydrocarbon~ having 4 or less carbon :
ato~s and halogenated derivative6 thereo~ carbon dioxide, ammoni~ and mixtures thereof which are non-degrad~ng w~th respect to sa~d mlxtures being concentrated.
The process may al90 be utilized for selec~velg ~eparating .
crystal~ o~ different meltin~ point components. In s~ch selective separation, the components are not conveyed fro~ a later contacting stage or vessel to an earlier contactlng stage but are kept in separate clrcuits, including lndividual .
later contactlng stages and t~us the desired components are completely .
crystallizable a~ a result of a contlnuous re-crystallization, thereby obtaining the products o~ high purity.
An apparatus for carxying out the process is also described comprlsing a ~lural~ty of cooling contact-column or vessel-contacting zonP
means including a ~irst contact column ~eans and succes~i~e con~act colum~
means3 eac~ having loc~ted at the bottom thereof coolant introduction ~alve meana designed ~o contact the feeds~ock mi~ture or mother liquor with a vaporizing and adiabatlcally expandi~g refrigerant and pro~ding a pres~ure drop between ~aid column means on the ln~ide of said valve means and the ~ource of refrigeran~ on the out6ide of said valYe meang whereby said refrigerant, by vaporizatio~ and ~d~abatic expa~slon, c0018 ~aid l~quid mlxt~re;
'. .
-' 10 -` , . '., . : . . . : . ~ , - -::. - :-,. , , ` , , :~ , : : - . .:: : :
andSaid contact column mean~ beln~ connected to separato~ means ~or c~n~
tinuously removing crystals formed ~n said contact column ~rom the still liquid mixture.
The process of~ers certain useful advantages. When the refrigerant is miscible ~ith the solution belng concentrated, and the solutes are soluble in the ~frigerant, the materlal may be concentrated untll ~ll of the solutes are completely Pxtracted from the solvents or diluent. During the latter stages o~ concentration, the ~e~rigerant itselE acts a~ a 601~ent and may then, at the final stage, be stxipped rom the solute. ~urther, i~
the coolant is immlsclble w~th the material being concentrated, lt serves as a vehicle and diluent ~or the slurry to maintaln it ln pumpable state until the very la6t stage3 to prevent the slurry and mother llquors ~rom becoming -too viscous.
The process ~ur~her o~er~ the ad~antage o~ permitting a high degree o~ concentration but with concurrent maintenance of the vitsml~7 aro~a ~nd taste components. The procesB~ aS ~t is devoid o~ any stages at w~lch the mater~31 i8 ~ub~ected to elevated temperatures and/or external oxidant~ such a~ oxygen in the alr~ thus avolds ~hese cGmmon drawbacks of t~e prior art. Fur~her~ even i~ some of the components ~f the ar~na of ~he feedstock should have high vapor pre~sure3, as the gase~ within the system s~e continuou~ly recycled3 the aroma xemain8 wi~hi~ ~uch gaseous components and i~ con~tantly reln~ected lnto the concentrate until the components c~mpletely ss~urate the gase~ snd reach a concentration and form ~herei~
they redis~olve ~n the concentrate. ;
. ' ., ' ' .
,. .
`~ .'.
~' ' ' ` ' "' . ' - : : , :
10694z7 Because of the slmpllclt~ of the varlous p~ocPssing stage~, control o~ both the rate o~ crystallization and the size o~ the ~inal crystals is provided. The tempera~ure and the concentration may be completely regulated by the rate of feed of raw material, rate of removal oP the ~inal product, .
rate of introduction oP the refrlgerant, pressure drop durlng the adiabatic ;
expansion of the refrigerant, addltion or cha~ges in both the nature of the refrigerant and/or other solvents intro~uced ~nto the system. Purthermore~ 9 the refrigerant coolant is completely ~ecovered as the pxocess operates under a closed cycle except or the ln~roductlon of the raw material and remoYal of the concentrate and its by-product.
As each stage o~ the proce~s ~s subiected to careful isolation and control, the energy requirements o the process are lo~. The meltlng o~
the YariOUS crystals~ may be carried out ~o that the latent heat required for such melting operations, ls utllized to cool and condense the re~rigerant, precool feedstocks or warm the semoved products.
~urther as the process operate~ in a closed sy~tem~
suitable for the treatme~t of any nature o~ pro & ct regardle of how heat or oxidation labile it may be. The product i~ never exposed to advers2 el0vated temperatures or extraneous oxidat~on by alr.
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: . .: :. .; . : ,, . : :~ : . .
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9~'7 The crystals obtained and removed from the first stage are very pure and are of a convenient size for separation steps including a washin~ step. Thus the purity of these crystals is greater than would normally be available byl the prior art processes because they are formed in a solution of low concentration.
Further, as in the case of treatment of brackish water, and fruit juice concentrates, lce crystals are removed at the first stage leaving behind a concentrated mother liquor. The salts recovered from certain brackish waters are commercially valuable. -~o The juice concentrates of course are a prime product.
The crystals formed from the mother liquor in the second and successive steps are all recycled to the preceeding including the first step and thus large crystal growth in the first step or stage is enhanced. It is well known that the larger the crystal, the purer is the nature of its components.
Further, the process also permits selected separation of crystals at two or more temperatu~es. Thus crystals can be removed from the first stage and also from the second stage or succeeding stages. This procedure can be utiliæed ~or the ~o separation of close-melting components such as for the separation of ortho-and para-xylene.
.
' ' ; .
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~0~94~7 In accordance with one aspect of the invention, there is provided, a process for concentrating a solution and for separating crystallizable components from a solution thereof which comprises introducing said solution into a first crystallization zone, spraying a highly volatile, pressurized and liquified cool mg agent directly into said first crystallization zone int~ contact with said solution, wherein said ooDling agent expands and cools said soluti~n to a temperature sufficient to fonm a slurry of crystals of a first crystalliæable component therein, maintam m g said temperature constant, separating said crystals of first crystallizable compon~lt fram said slurry to form a prelImlnary ooncentrated solution, transferring substantially only said preliminary concentrated solution to at least one further crystall.ization zone separate from said first crystalli~
zation zone spraying said oooling agent directly into said further crystallization zone into oontact with said preliminary concentrated solution in an amount sufficient (a~ to expand and cool said preliminary solution in said further crystalli-zation zone sufficiently below the temperature of said solution in said first crystallization zone bD form a further slurry of crystals therein and at the same time (b) to act as a liquefacient for said further slurry and thus reduce the visoosity thereof, the temperature of said preliminary concentrated solution .
in said further crystallization zone being such that the total of the crystals formed in said first and said further crystallization z3nes is about 65 to 100% of the crystallizable oomponents of said solution, separating said crystals from said further slurry to foxm a ooncentrabed ,, ,. . - , .. . . .. . . : . ..
~(~6S~Z7 ' solution oontaining liquified oooling agent and separating said oooling agent from said concentrated solution.
In acoordance with the seoond aspect of the invention, there is provided apparatus for concentrating miXtNreS from a feed stock of a dissolved mixture of ccn~onents mcluding crystallizable solYents and crystallizable or am~rphous solutes which comprises, .., ~, ~ - 13B -:. .. . .- :. . .
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~(~6~342'7 at least a first and a further contact vessel, refrigerant compressor means, means connec-ting the refrigerant compressor for introducing liquid refrigerant into said first and further contact vessels, means for introducin~ feed stock into the first con-tact vessel;
means for evacuating refrigerant from said first and further contact vessels for permitting vaporization and cooling of said refrigerant and substances in said vessels, means for returning vaporized refrigerant from said vessels to said compressor, said feed stock being cooled in said first contact vessel to a first stage temperature below the freezing point of a first crystallizable fraction, means for extracting said first crystallizable fraction with entrained mother liquor from said first contact vessel and unvaporized quantities of refrigerant, means for recovering said first crystallizable fraction as first crop crystals and separated mother liquor, means for recycling a portion of said separated mother liquor :
to said first vessel, means for transferring the remainder of said separated mother liquor to said ~urther contact vessel, said mother liguor being there further cooled to a second temperature below said first temperature and forming a second crystallizable fraction and entrained further concentrated mother liquor with unvaporized liquid refrigerant mixed there~ith, ':
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means for recovering said second crystallizable fraction as a second crystal crop with adhered further mother liquor and further separated concentrated mother liquor and liquid refrigerant, means for mel-ting and recycling said second crystal crop with adhered further mother liquor to said first contact vessel, means for recycling part of said separated further concen-trated mother liquor to said further contact vessel, means for stripping refrigerant from the remainder of said fur-ther concentra-ted mother liquor and for returning said s-tripped refrigerant to said compressor, and means for recovering the stripped mother liquor as a concentrate.
Specific embodiments will now be described with reference :
to the accompanying drawings in which;
- Fig~ 1 is a schematic flow diagram of a process for ~ :
concentrating materials utilizing only two stages ~or the concentration of fruit juice and, Fig. 2 is a schematic flow diagram of a second process utilizing four stages for the concentration.
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.~ ' '7 In princ~ple, cons~de~ng only the prDce6s as described 1~
Figure 1, ~he two stage separatlon, the process operates as follows: .
The fresh feed o~ ~ulce, ~J is pumped ~nto the first contact vessel Rl. The contact vessel Rl is connected to crystal separati~g centri-fuge Cl. The temperature w~thln contact ~essel Rl i8 continuously reduced by the direct inJection of the refrigerant therein via val~es CVl. A~ a result of the lowering of the temperature ln vessel Rl, a slurry of crystals o the first crystallizable component in a mo~her llquor are obtained. This :
slurry S, is continuously ~ed lnto centrifuge Cl where the crystals are :
separated fFom the mother liquor and ~rom where the mother liquor i~ recycled to vessel Rl. `
The temperature in vessel Rl is maintained within the con-trolled limits set to provide c~mple~e crystallization of all crystallizable :
components, crystalli able do~n to sald controlled temperature. The mother ~. .
liquor i8 continuously and constantly retur~ed into vessel Rl-. As the ~ :
~emperature in vessel Rl i5 mainta~ned constant at the p~opez temperature, ~i .
the crystalli2able components are contlnuously formed and grow into large crystal~. These large ice crystals a~e remo~ed from the slurry by centrifuge Cl where they are ~ashed. They may be melted in heat exchsnge ~elationship ~0 with ~efrlgerant vapour heat exchanger, fusion tank FTl to cool and partially condense the compressed refrigerant ~apor~. Some melt~ng hea~ ~or the crystals ~ ~ :
may also be provided in HEl by cooling fresh Juice being ~ed into ~ulce holding -.
tank 3 which provides the feeds~ock F3 to vessel Rl. . ;
The melt o the crystals, ~ypically water, is then removed `
r~m the sy~tem via vacuum column 5 ~here adhered refrigerant vaposF ~e :
~tripped. The water i~.dlscarded or if the water iB 8 desired end product, as in pur~fication of brackish water, the water is utillzed in lt~ pure form.
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~L069427 First stage vessel Rl which may be a cont~ct column, is preferably maintained at about -5C durlng juice concentration, in order to obtain a æubstantially pure ice c~ystal.
The mothe~ llquo~ is continuously ~ecycled into vessel Rl from centrifuge Cl together with any water. ~ port~on of the flrst stage con-centrated mother liquor frum centrl~uge Cl i8 pumped into the second stage contact vessel R2. This contact vessel ~ operates in a manner 6imilar to that of the fir~t stage contact vessel Rl. It is al80 cooled by ~he in~ection o~ refrigerant, but it ls cooled to a lower temperature at whic~ another slurry 10 of a portlon of crystals ~orms in a ~urther concentrated mothe~ liquor. The `
type and proportion of the cry~tals depend upon the lower temperature to ~hich vessel R2 has been ad~usted. Thu6 if desired, t~o different crystallizable components can be selec~ively removed, o~e crystalllzing at the temperature of vessel Rl Yia centrifuge CI and the other crys~alllzing at temperatures dow~ to the lower temperature o~ second ~tage vessel ~2 via centrifuge C2.
The cry6tal~ from the ~irs~ stage centri~uge-Cl are washed, ~emoved from the ~ystem and the~ melted in heat exchanger PT2 by refrigerant gases in a si~ilar manner as descrlbed aboYe. These crystals ~re o~ high purity from the first c~ystallizàbile ccmponent.
The crystals ~rom the second stage cooling removed from the ~econd centrifuge C2 except where specifically desired for selecti~e ~eparatlon a~ set`forth above~ are melted and the melt is reintroduced and recycled into first stsge contact ~essel Rl thus recovering any i~corporated and ad-herent mother liquor on these crystals. ;
In the case of fruit ~u~ce~, this effect is utilized i~ order to obtain very high conce~trates of the ~ruit ~uice solids. ~ow~ver, in each ., . . .
ca~e, the ~urthe~ cooling i6 ~lways perfor~ed ~ ~he sa~e manner and the ~
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~L11)6~9L~L~7 c~yst~llizing portlon o~ the ~lu~y o~ c~ystals ~rom the second and successlve stage vessels R~ which is separated a~ centri~uge C2 ls returned to the first vessel Rl in order thereby to preserve the low level of crystallizable com-ponents of the already co~centrated ~other liquor. It also provides control for the separation in an active manner of the second crystalllzable components ~hich are crystallized down to the temperature o the second contact vessel opera~ing temperature.
In the case o~ fxuit ~uices, crystals separated by the second centrifuge C2 are melted and passed into the ~irst reactor. These second crop crysta~s are utilized in FT2 a~ a coolant ~or the compressed re~rigerant ;
during their melting in order t~ condense i~ partially to liquid ~orm. At the , same time, any incorporated and adherent ruit ~uice concentrate mother liquors are not lost. ~
When the desired sep~ration of cryst~llizable componentR has ;
been obtained, a portion o~ the ~inal liquid co~centrate, from centrifuge C2 i8 degased, stripped of any re~rigera~t there~ and is removed aB the fi~ished final concentrate.
The CryBtalS sepaxated by the firs~ stage ce~trifuge Cl are melted in heat exchange relationship ~or the cooli~g and partial condensing 20 o~ the campre33ed refriger~nt and a portlon o~ this is then used as the wash in centrifuge Cl. This wash liquor is ~hen returned to the ~irst contact ~essèl Rl ~n order to pxevent losses o~ ~other liquor.
The entire cooling system is designed or direct liquid `
ln~ectlon o~ t~e re~rlgerant into the contact ves6els Rl~ R2. After e~pansiDn, t~e xe~rigerant ~apors are continuously ~lthdraw~ at the top of the ves~els, cooled and recondensed as is usual in c108 d~cycle treatmen~ o~ refr~ge~ant ,~
gase~. These gase~ may be compressea by con~entional c~mpre~sors and the c~pressed gase~ are then cooled and liquidl~led for re~Re~ :~
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1(3694Z7 The ~oces~ o~ th~ ~nyent~on m~ be c~r~ed out ~th varied refrlgerants dependlng upon ~inal ef~ect and the mother liquor to be co~-- centratèd and treated. Tests ha~e been successfully conducted in pilot plants with propane, ammonia> carbon dloxide, methylene ehloride~ methyl chloride diflurodichloromethane~ tsifluoromonochloromethane and their derivatives (Freons T.M. and Frigens T.M.).
The adlabatic coollng wlth each of these re~rigerants proceeds ;
without a~y difficulty. It should be noted tha~ the usual precautions s~ould be taken with carbon dioxlde a6 the refrige~ant in order to a~oid freezing problems in the lnJection valve3. It i8 o~ten adYantageous if the re~rlgerant is solu~le in the mother llquor being treate`d. Soluble ~ePrigerants in the ~other liquor e~ert a favorable in~luence on the lo~ering of the viscosity of the h~ghly conce~tra~ed mother liquors. It has also been noted ~hat the dissolved refrigeran~s in the ~other liquor exert favorable influences upon the rate and type of cryætal formation.
Soluble re~rigerants have been noted to be especlally use~ul in the concentration of ~ruit j~ices as they permlt ~he highest degree of concentration of th~ solutes ~hile a~oiding pumpi~g problemæ with the highly ~iscous concentrate~ oontaining ~igh proportions o~ sugars.
. Tha proce~s described ~ay be carried out under various conditicns of pressure within the contact ves6els. I~ iB advantageous ~or the proce~s to be carried out a~ atmo pher~c pressure. However, pres6ure6 below ambient and 6uper ~tmospheric pres~ures may al60 be utilized in the contact ve~els Rl 2nd R2. For eKample, it has been ~ound that when the process is .
carried out under pressures above a~mospheric, large amounts of liquid re~rigera~t remain in the resulting slurry. These amount~ are reduced whe~ the prooea6 :
is operated ~t lawer pre~sures.
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. - . . -, . . , - ~ ' ~(~6~Z7 These di~e~ential amounts o 1uid refrigeran~ ~e~aining in the concentrate may be advantageously ut~lized~ ~or e%ample, ln ~he case where water is to be remo~ed from delicate pharmaceutlcal oil emul~ions a~d the pxocess is carried out with propane as a coolant. ~hen vessel Rl is at atmospheric pressure and, at a temperature o~ about -3C, approximately 6 to ~j 10% of the propane remains in the emulsion. If however, the process is carried out, approximately 3 atmospheres, then up to 30% of the prop~e remains dl~-solved ln the oil5 thereby keeping the resul~lng emMlslon in a fluid form.
Fhrther9 if the process iB carrled ont ut~llzing Freon 12 T.N. as the refrigerant, the refrigerant content ln the vessel at a pre~sure o~ 2 atmospheses 18 i~
sressed to o~er 60%. The resultan~ concen~rate i8 a completely mobile liquid which permits ease of pumping o~ the slurry before f~ltration of the resultant concentrate.
Con~ersely, when the op~ration i8 conducted in lower than atmospheric pxessures, the re~rigerant may be kept in the cooling vessel R
or in an ad~acent sec~ndary tan~. When operating under the~e conditions~
special crystallizati~n effects are obtained. For exæmple in the dewaxing of .., , edible o~l~, in which the presence of excess refrigerant ca~ have an adverse efect upon the type of cr~stals a~d on crystal gr~wth, it is pos~ible to ;l -achieve ~atis~actory cryst 1 growth by operating at lower than atmo~pheric pressure6.
Whe~ lt ls desired to obtain patticularly low temperature6, it i~ possible to achleve temperatures of -90C (using liquid air) without d~$ficu1ty depending upon the re~rigerant and the pressure wlthin the contact 1` ~ ` ~1. .
~ a preferred e~ample? f~e6h orange Juice was ~ub~ected c~nt~nuo~ concentrat~o~ trcatm~t utill~in~ dlc~lorodlfluoro methane (Refrigera~t 12) as refrlgerant, and a~ described bel~ws ;
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1~S94~'7 ~ esh o~ange ~u~ce ~3 Rt ~ te~pe~ature o~ 20S, previously clarlfied by centri~uging to be ~ree o~ sollds such as plts, pulp particles etc. is pumped by means o~ pump 1 through heat exchangers HEl 2nd HE2 into storage tank 3, maintained under a protecti~e atmosphere ln order to preserYe the vitamins and prevent oxidat~on. The temperature of the ~uice in tan~ 3 i~ about 7C. From ~ank 3 the ~uice i~ pumped into the upper part of the flrst stage cooling ~essel Rl which 1~ provlded in its upper part with a droplet separator ~not shown). The ~uice 10ws countercurrent to the rislng refrigerant vapors down over the plates into the lower widened part of the cooling vessel Rl which is equipped at lts bottom w~th several refrigerant in~ection valves 2. Val~es 2 serve to introduce the refrigerant directly into cooling vessel Rl.
The refrigerant ~rom pressuriæed storage ~essel 7 ls in~ected in the liquid phase into cooling vessel ~l at a pressure of about 5 atmospheres.
As a re~ult of the adiabatic expansion of the refrigerant ln cooling vessel Rl, the temperature o~ the ~ulce at the bottom of said cooling vessel Rl decreases to about -5C. ~s a result of the cooling to about -5C, the water compone~ of the ~uice freezes to ~orm a slurry o~ ice crystals in a mother liquor oP ~uice concentrate. The turbulance caused by the phase change of the sefrigerant provides ~or a homogenous slurry of the water crystalQ in the mother liquor. It also equal~æes the ~emperature within the slurry and prevents lump formation. ~ ;
The ln~ection of the refrigerant through ~alve 2 is controlled and regulated to insure that the ~lurry of ~ce crystal6 ln the ~other liquor r~mains fluid. Portions of this slurry are continuously discharged in~o ce~trifuge Cl- Crystal formation is l~i~iated at temperature~ in the sa~ge -l.5 to -2C. The ~ry6tal8 gro~ under the ~nfluence of ~he unifoxm temperature - 19 - :
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~106~t4Z7 within contact vessel ~ ~hlch ~s ma~nt~ned ~t ~5C. The c~ystals; in the case o~ ~r~zen fruit ~uice~ axe ~u~e ice.
Centri~uge Cl where t~e crystals are separated from the mother liquor is equipped with a ~ontinuously operating lce washing system. The ice crystals are washed with water to prevent losses of any Juice componentB
resulting from any ~ulce which adheres to the sur~ace o~ the ice crystals. .
At the initiatlon of the process belng desc~bed all o~ the Juice P~ that hag been centrifuged i~ recycled to ~egsel R~ by closing valve Vl and opening valve VlR. When the temperature in vessel Rl has stsbilized at about -5C, the second stage concentration step is initiated by ope~ing ~al~e vl and partially closing ~al~e v~ t about 5C approximately 50% of the water has been crystallized ~rom the ~u~ce. It 1~ ell~i~ated as ice via centrifuge Cl.
- When second stage concent~atlon iB initiated i.e. when the .
temperature of vessel Rl has stabilized a~ -5, val~e 1 is opened 80 that between 20 to 50% of the preconcentrated juice l.e. the mother liquor is cont~nuously pas~ed ~rom centrifuge ~1 lnto cooling ves~el ~2. The propor~ons .
a~d conditio~s i~ first stage vessel Rl are ad~usted in such a manner that the temperature of Rl remains substan~ally constant and the feed amounts thereto are ~imilarly const2nt RO ~hat t~e amounts of fresh ~uice and re-cycled concentrated ~uice PlR thst is.already preconcentrated are continuously pasaed into ve~sel Rl and a part of thls first stage concentrate is pa~sed ~nto vessel R2 through val~e Vl.
The recycling ~ preconcentrated ~ulce to vessel Rl 3eFves to maintain a lo~ proportion o~ crystals to concentra~ed ~uice componentR in ~ .
order to pe~mit good lce~cryst31 grow~h thereiD. The growth of large lce c~ystsl8 provides proper and complete separation.
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The concent~ated ~u~ce ~l ~h~ch h~s been pumped into second stage vessel ~2 is further cooled by the ~njection o~ additi~nal refrigerant through multiple valves 2 into the lower section o~ vesæel ~2 thus further cooling this mother liquor. ~ ~ortion of the refrlgeran~ dissol~es in the 81urry which includes the addltional crystals ~hich form i~ ve~sel ~2. This dissolved refrigerant reduces the ~i~co~ity o~ the concentrated slurry S2 in vessel R2. Even when the coolant is insoluble ln the slurry, the homo-geniety of the slurry is preserved as a result of ~he turbulance caused by - the boiling refrigerant and in addltlon, the added liquid provided by the immisctble rafrigerant contributes to the mobillty of the cGncentrated ~lurry S~.
~ s a result o~ the d~rect in~ection o~ the refrigerant, the temperature in vessel R2 is reduced~ addltional ice forms to create slurry S2. Tha slurry S2 i8 led continuously f~om vessel R2 into centrifuge C~.
I~ this second stage, the entire amount of mother llquor P~ leaving centri-~uge C2 1~ recycled to vessel R2 where an equilibrium ~empera~ure of -9 to -11 is maintained. This temperature range ls prefexred as at -8C about 65 to 70% of the initial water content of the Juice ~ill be crystallized as ice. Thls ice proportion increaseo to 72% at -9C; to 78% at -10C, and to 85% at -llGC.
The ~uice concentrate from centrifuge C2 is recycled to ~esæel ~ through valve V2R until ~n equilibrium temperature ~ithin ves3el R2 has been reached. This equilibrium t~mperature deter~ine~ ~he concentra-tion of ~he final concentrate.
:; ; .. , ~ hen the temperature in the ve~sel ~2 has become stabili~ed, a part o~ ~he centrifuged mother liquor P2 i5 pumped through fu6i~n tank -.~ .
heat eYchanger FT~ and th~n d~rec~ly to reduced pres~ure colum~ 4~ in ~hich ~ - - 21 --: ' ' ' -: ~ . , . ., . ~ . - : -106g4Z7 the temperature o~ the concent~ate ~ ~6C, ~t th~s tempe~ature9 there i3 a complete removal and stripping o~ an~ re~rlgerant which may be dlssolved in this ~inal concentrate which i9 the desired product. ~s a resul~ of the high degree of sugar concentration of the co~ponents o~ the ~uice in vessel R2 the water csystals I2 separated by centri~uge C2 and ha~lng the t~mperature of -10C are microcrystalline in ~oxm. Thls for~ of ice crystals is very difficult to separate ~rom the liqui~ ~uice~c~mponents, portions o~ which adhere to the microcry6tals. These sèparated crystals I2 are melted in fusion tank FT2 and a~ter melting are ~ed directly to ~irst ~essel Rl. The low temperature o~ the micr~crystal~ i~ used in heat exchange~s such as ~T2 to partially condense the compre6sad refrigerant on lts way to refrigerant pres6ure vessel 7. In additlon, any ~uice co~ponents adsorbed on or contalned ~ithin the microcrystals are secycled by reintroduction into ~irst stage cooling vessel Rl. ~ :
In addition, the first stage mother liquor Pl is continuously sub~ected to a reconcentration process a~er centrifuge Cl in the ~ollowing manner: The slurry of crystal~ ~ ~rom Rl, at a ~emperature o~ ~4 to 59 : ~.
and i~ separated at Gl, to yield ice ~rystals in substantially pure form-20 to 90% of the ~other liquor Pl is recycled to vessel Rl through valve V1R~
~0 and the res~ ls transferred to vPssel ~2. .
At the 8ame time, the fresh ~uice continuously enters ~rom .
storage tank 3 into vessel Rl. Simultaneously, the crystals separated by ~
centrifuge Cl are washed with a part of the water Wl obtained in ~usion tank .
FTl. This ~ater Wl which representg about l/4 of the melted ice stream ~ i~
utilized ~ the cen~ri~uge Cl ~or washing. A~ter washing, all o~ the wash water i8 recycled to flrst ~tage veQsel Rl. The remainder of the water, ~ot ~ .
U8ed for w~shing~ pa~ses th~o~gh he=t excbange~ ~El and the~ to colum~ S where .
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it is stripped fro~ anyentrained refrige~ant gases. This water from column 5 i9 removed from the system and the re~rigerant gas ls recycled.
A portion of the second stage concentrate P2 which is the liquid separated from the ice in centrifuge C2 is transferred to column 4 where any dissolved refrigerant is stripped and the concentrate thè final product, is removed from the system.
All of the refrigerant introduced into the system into the cooling vessels Rl and R2 and vapori~ed through ~alves 2 and 2A is pumped from the top of the vessels Rl and R2, through a droplet separator (not shown) and led to compressor 6. These gases are generally rem~ved at about atmospheric pressure. However, ~Jhen special effects are desired i~e. when some refrigerant liquid is to remain in the juice concentrate in order to lower its viscosity, it is advantageous to operate at higher pressures in different stages at ~essel Rl and R2.
The refrigerant gases from cooling vessels Rl and R2 are Ped to compressor 6 where they are compressed and then cooled and condensed to liquid state via heat exchangers which are fusion tanks FTl and FT2, and if necessary, with the help of an e~ternal refrigera~ion circuit HE4. The liquid condensed refrigerant is then led to and stored in tank 7 from where it is injected into vessels Rl or R2 as needed for refrigeration.
The above operation is substantially the same for all types of fruit juices. The specific temperature maintained in reactor R2 depends upon the desired final concentration of the ~uice concentrate. Consequently any crystallizable product can be processed by this method. The products can be further processed by additional stages until total removal of~the initial solvent, diluents and other undesirable crystallizable materials is achieved.
To this end, a four-stage process is ~ho~n in ~igure 2. The only differences .
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~f;9~'7 between ~i~u~e 1 and F~gu~e 2 ~e t~e ~dd~t~onal ~stageS and the ~eplace~ent .
o~ stripping column 4 b~ equipment which per~its wlthdrawal o~ the final product as a solid ~ a screw expellor i~ such ~s its nature.
The ~eedstock llquids contalnlng the crystall~zable substance may be treated with o~her dil~ents which may be soluble or lnsoluble in the product. Furthermore, various o~ the illustrated process and a~paratus components may be interchanged by art-recogn~zed equivalent~.
For instance, the cent~i~uges ~ay be re~laced by ~llter~ and/or filter presses. Sim~larly, screw expeller~, Blrd filters and other ~uitable equipment ~or the r~oYal o~ the crystals ~rom the mother liquor may be utillzed.
The actual configuration o~ the cooling ~e~sels Rl and R2 wherein the ice i~
formed may vary with the slze of the equipment being used, heat exchange conditions~ nature o~ the re~rigerant and the a~bient surroundlngs which include the am nt and degree of insulation nece~sary.
Because of the utilization of the re~rigera~t as a secondary ~olvent, ~he present invention make6 it posgible for the process to be carried out withou~ any difficulty to a de~ree whereby a total re~oral o~ all the water or other crystallizable sol~ent without any after treat~ent at elevated temperatures. By the continuous recycllng techn~que at the f~rst stage, crystals of large size, are formed and continuously removed. In addition, by careful control and design, expedient~, permitted by the proces~, it is :
po~sible to achieve great economy of energy exchange through the ~udiciou~
use of heat exchanger~ between the cooled materlals and the warmer materials.
Nany varied coolants may be ~sed depending upon the naturé o~ ~ -the proauct to be concentrated. For an exa~ple, good result` ha~e been ¢btained with the followi~g products a~d by the li6ted refrigerants used there~ith.
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:10694Z'7 TABL~ .
~EEDSTOCK . ~ . __ Rr~ R~C - .
~ruit Juices ~ropane ~reon 12 Freon 22 ~T.~
... . . . .. . .. Carbon . l~iox~de .. .
. ~ ~
Beer . ..... . . . .. Carbon ~io~ide .
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Wine Freon 13 (T.M.) . .. . . . . . Carbon.Dioxide ' - ' - ~ _ . ~ .. ._ _. . ~
Edible Oilg' ~ethylene Chloride ;
Methyl Chloride .
Carbon Dioxide ~ -... ............. Propane . ~ ~
~ylene . . . .... .. ....... Liquid.Ammonia. .
___ . . . . j~ . .
~ilk . . . . . . . Freon 13. . . .
~ . . . . _ _ . . ._ Pharmaceutlcal.Emulsions . . ..... . ... . . . Propa~e. . . . . . ~
_~ ......... . . . , .. , . . . _ . . .
Antibiotic Fe~me~tation Beer~ Propane . . . . Carbo~.Di~xide . . .
. _ . . . . . :
Botanical E~tracts Propane ~
Carbon Dioxide ~ .
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. . .. . . :. . .... Freon.22.... ... .... . .
__ .. . .. ... ., The temper~tures ~ithin the cooling ~essels ~ snd ~2 ~ay be ~
ad~u ted ~ccording to the desired e~fec~6~ It ~ pos6ible ~o utiliz ~hs :
standard cooli~g to~ers withsut any di~f~culty provlded that in~ulatio~ is .
adequate, at temperature~ ranglng ~rom ~90C to up to ~20C. Fu~t~er, the ..
~ate o~ cooling can be accurately:co~t~olled by the amount o~ ~efriger~nt ~ .
~ntroduced l~to vessels ~ and ~2. : ~ . :
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lU~9~'7 The p~esent inrent~on~ ddition~ ~ovldes p~ecise control oX the crystal slze o~ the matertal~ whlch are crystalllzed during the first stage. By control o~ the cooling, the cry~tal slze can be controlled to provide large crystals and consequently purer crystals. In addition, to achieving control by a slower re4~igerant in~ection, change~ in the diameter of cooling veqsel Rl and R2 and ~rying the rate of feed o~ the liquids and the amount of recycling o~ mother liquor can also control the ~rowth of ~he crystal~.
~n interesting aspect o~ the present prnce~ the contrnl of differlng crystal sizes depending npon the concentration of the ~uices to be treated. Thus in the flrst stage cen~rifuge, Cl, the centrlfuge screens may be relatively coarse i.e. 60 ~o lO0 mesh per inch (0.4 t~ 0.25 mm opening) sizas are sufficient. However, ln the second ~tage, centrifuge C2, it is preferred to haye smaller screen openings. I~ it is desi~ed to insure that -the Plnal ~ice concentration have between 80 and 85% of the water remoYed, the screen opening diameter should not be oVe~ 0,1 mm. The substantial amounts of the fresh Juice which adhere to snch microcrystals ar~ recovered because they are recycled to ~essel Rl a~ter leaving hea~ exchanger usion tank ~T2 form~g ~ream ~ .
While the above de6crip~io~ ha~ been confined to describing the operation for concentrating fruit ~uices to the degree where approximately 80X of the water has been removed, the process i~ similarly u~eful in con-centrating beer6 to remove exces~ water prior to shipment, for the concentrationof cry3tallizable from non-crys~allisable com~onents o fatq, for the separa~lo~ of the xylene i80mer8~ for the freeze concentration of milk.
concentration of botanical extract~, teas, and the ~reabme~t of ~ariou~ labile ant~blotic fen~entation bee~s ln order to concentrate ~he sntibio~ic con~ent6 `
thereo~
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": ' . ' ' :' , '' ' ' .': ' .,, ~" ',.' ', . '', ., ~. '~ :'.' The p~ocess desc~bed ~o~ the ~uice~ are ~e ely ~xemplary and the above art rec~gnlzed e~u~valentg can be subgtitu~ed for the ~ulces ~n the operations o~ the process described aboYe. ~urthermore3 any apparatus units can be substituted-by thelr art-recognlzed ~unc~ional equi~alents, All such art-recognized equivalents are intended within the scope of this lnven~lon3 no~ claimed. .
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Generall~, the ~e~r~ge~nt~cooling agent is selected from .
~he group of low boiling hlgh-~P~or pressure refrlgerants havlng a hlgh caloric equivalent of heat o~ Yaporlzation selected ~ro~ the gxoup consisting of 6aturated and unsaturated alipha~ic hydrocarbon~ having 4 or less carbon :
ato~s and halogenated derivative6 thereo~ carbon dioxide, ammoni~ and mixtures thereof which are non-degrad~ng w~th respect to sa~d mlxtures being concentrated.
The process may al90 be utilized for selec~velg ~eparating .
crystal~ o~ different meltin~ point components. In s~ch selective separation, the components are not conveyed fro~ a later contacting stage or vessel to an earlier contactlng stage but are kept in separate clrcuits, including lndividual .
later contactlng stages and t~us the desired components are completely .
crystallizable a~ a result of a contlnuous re-crystallization, thereby obtaining the products o~ high purity.
An apparatus for carxying out the process is also described comprlsing a ~lural~ty of cooling contact-column or vessel-contacting zonP
means including a ~irst contact column ~eans and succes~i~e con~act colum~
means3 eac~ having loc~ted at the bottom thereof coolant introduction ~alve meana designed ~o contact the feeds~ock mi~ture or mother liquor with a vaporizing and adiabatlcally expandi~g refrigerant and pro~ding a pres~ure drop between ~aid column means on the ln~ide of said valve means and the ~ource of refrigeran~ on the out6ide of said valYe meang whereby said refrigerant, by vaporizatio~ and ~d~abatic expa~slon, c0018 ~aid l~quid mlxt~re;
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andSaid contact column mean~ beln~ connected to separato~ means ~or c~n~
tinuously removing crystals formed ~n said contact column ~rom the still liquid mixture.
The process of~ers certain useful advantages. When the refrigerant is miscible ~ith the solution belng concentrated, and the solutes are soluble in the ~frigerant, the materlal may be concentrated untll ~ll of the solutes are completely Pxtracted from the solvents or diluent. During the latter stages o~ concentration, the ~e~rigerant itselE acts a~ a 601~ent and may then, at the final stage, be stxipped rom the solute. ~urther, i~
the coolant is immlsclble w~th the material being concentrated, lt serves as a vehicle and diluent ~or the slurry to maintaln it ln pumpable state until the very la6t stage3 to prevent the slurry and mother llquors ~rom becoming -too viscous.
The process ~ur~her o~er~ the ad~antage o~ permitting a high degree o~ concentration but with concurrent maintenance of the vitsml~7 aro~a ~nd taste components. The procesB~ aS ~t is devoid o~ any stages at w~lch the mater~31 i8 ~ub~ected to elevated temperatures and/or external oxidant~ such a~ oxygen in the alr~ thus avolds ~hese cGmmon drawbacks of t~e prior art. Fur~her~ even i~ some of the components ~f the ar~na of ~he feedstock should have high vapor pre~sure3, as the gase~ within the system s~e continuou~ly recycled3 the aroma xemain8 wi~hi~ ~uch gaseous components and i~ con~tantly reln~ected lnto the concentrate until the components c~mpletely ss~urate the gase~ snd reach a concentration and form ~herei~
they redis~olve ~n the concentrate. ;
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10694z7 Because of the slmpllclt~ of the varlous p~ocPssing stage~, control o~ both the rate o~ crystallization and the size o~ the ~inal crystals is provided. The tempera~ure and the concentration may be completely regulated by the rate of feed of raw material, rate of removal oP the ~inal product, .
rate of introduction oP the refrlgerant, pressure drop durlng the adiabatic ;
expansion of the refrigerant, addltion or cha~ges in both the nature of the refrigerant and/or other solvents intro~uced ~nto the system. Purthermore~ 9 the refrigerant coolant is completely ~ecovered as the pxocess operates under a closed cycle except or the ln~roductlon of the raw material and remoYal of the concentrate and its by-product.
As each stage o~ the proce~s ~s subiected to careful isolation and control, the energy requirements o the process are lo~. The meltlng o~
the YariOUS crystals~ may be carried out ~o that the latent heat required for such melting operations, ls utllized to cool and condense the re~rigerant, precool feedstocks or warm the semoved products.
~urther as the process operate~ in a closed sy~tem~
suitable for the treatme~t of any nature o~ pro & ct regardle of how heat or oxidation labile it may be. The product i~ never exposed to advers2 el0vated temperatures or extraneous oxidat~on by alr.
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9~'7 The crystals obtained and removed from the first stage are very pure and are of a convenient size for separation steps including a washin~ step. Thus the purity of these crystals is greater than would normally be available byl the prior art processes because they are formed in a solution of low concentration.
Further, as in the case of treatment of brackish water, and fruit juice concentrates, lce crystals are removed at the first stage leaving behind a concentrated mother liquor. The salts recovered from certain brackish waters are commercially valuable. -~o The juice concentrates of course are a prime product.
The crystals formed from the mother liquor in the second and successive steps are all recycled to the preceeding including the first step and thus large crystal growth in the first step or stage is enhanced. It is well known that the larger the crystal, the purer is the nature of its components.
Further, the process also permits selected separation of crystals at two or more temperatu~es. Thus crystals can be removed from the first stage and also from the second stage or succeeding stages. This procedure can be utiliæed ~or the ~o separation of close-melting components such as for the separation of ortho-and para-xylene.
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~0~94~7 In accordance with one aspect of the invention, there is provided, a process for concentrating a solution and for separating crystallizable components from a solution thereof which comprises introducing said solution into a first crystallization zone, spraying a highly volatile, pressurized and liquified cool mg agent directly into said first crystallization zone int~ contact with said solution, wherein said ooDling agent expands and cools said soluti~n to a temperature sufficient to fonm a slurry of crystals of a first crystalliæable component therein, maintam m g said temperature constant, separating said crystals of first crystallizable compon~lt fram said slurry to form a prelImlnary ooncentrated solution, transferring substantially only said preliminary concentrated solution to at least one further crystall.ization zone separate from said first crystalli~
zation zone spraying said oooling agent directly into said further crystallization zone into oontact with said preliminary concentrated solution in an amount sufficient (a~ to expand and cool said preliminary solution in said further crystalli-zation zone sufficiently below the temperature of said solution in said first crystallization zone bD form a further slurry of crystals therein and at the same time (b) to act as a liquefacient for said further slurry and thus reduce the visoosity thereof, the temperature of said preliminary concentrated solution .
in said further crystallization zone being such that the total of the crystals formed in said first and said further crystallization z3nes is about 65 to 100% of the crystallizable oomponents of said solution, separating said crystals from said further slurry to foxm a ooncentrabed ,, ,. . - , .. . . .. . . : . ..
~(~6S~Z7 ' solution oontaining liquified oooling agent and separating said oooling agent from said concentrated solution.
In acoordance with the seoond aspect of the invention, there is provided apparatus for concentrating miXtNreS from a feed stock of a dissolved mixture of ccn~onents mcluding crystallizable solYents and crystallizable or am~rphous solutes which comprises, .., ~, ~ - 13B -:. .. . .- :. . .
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~(~6~342'7 at least a first and a further contact vessel, refrigerant compressor means, means connec-ting the refrigerant compressor for introducing liquid refrigerant into said first and further contact vessels, means for introducin~ feed stock into the first con-tact vessel;
means for evacuating refrigerant from said first and further contact vessels for permitting vaporization and cooling of said refrigerant and substances in said vessels, means for returning vaporized refrigerant from said vessels to said compressor, said feed stock being cooled in said first contact vessel to a first stage temperature below the freezing point of a first crystallizable fraction, means for extracting said first crystallizable fraction with entrained mother liquor from said first contact vessel and unvaporized quantities of refrigerant, means for recovering said first crystallizable fraction as first crop crystals and separated mother liquor, means for recycling a portion of said separated mother liquor :
to said first vessel, means for transferring the remainder of said separated mother liquor to said ~urther contact vessel, said mother liguor being there further cooled to a second temperature below said first temperature and forming a second crystallizable fraction and entrained further concentrated mother liquor with unvaporized liquid refrigerant mixed there~ith, ':
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means for recovering said second crystallizable fraction as a second crystal crop with adhered further mother liquor and further separated concentrated mother liquor and liquid refrigerant, means for mel-ting and recycling said second crystal crop with adhered further mother liquor to said first contact vessel, means for recycling part of said separated further concen-trated mother liquor to said further contact vessel, means for stripping refrigerant from the remainder of said fur-ther concentra-ted mother liquor and for returning said s-tripped refrigerant to said compressor, and means for recovering the stripped mother liquor as a concentrate.
Specific embodiments will now be described with reference :
to the accompanying drawings in which;
- Fig~ 1 is a schematic flow diagram of a process for ~ :
concentrating materials utilizing only two stages ~or the concentration of fruit juice and, Fig. 2 is a schematic flow diagram of a second process utilizing four stages for the concentration.
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.~ ' '7 In princ~ple, cons~de~ng only the prDce6s as described 1~
Figure 1, ~he two stage separatlon, the process operates as follows: .
The fresh feed o~ ~ulce, ~J is pumped ~nto the first contact vessel Rl. The contact vessel Rl is connected to crystal separati~g centri-fuge Cl. The temperature w~thln contact ~essel Rl i8 continuously reduced by the direct inJection of the refrigerant therein via val~es CVl. A~ a result of the lowering of the temperature ln vessel Rl, a slurry of crystals o the first crystallizable component in a mo~her llquor are obtained. This :
slurry S, is continuously ~ed lnto centrifuge Cl where the crystals are :
separated fFom the mother liquor and ~rom where the mother liquor i~ recycled to vessel Rl. `
The temperature in vessel Rl is maintained within the con-trolled limits set to provide c~mple~e crystallization of all crystallizable :
components, crystalli able do~n to sald controlled temperature. The mother ~. .
liquor i8 continuously and constantly retur~ed into vessel Rl-. As the ~ :
~emperature in vessel Rl i5 mainta~ned constant at the p~opez temperature, ~i .
the crystalli2able components are contlnuously formed and grow into large crystal~. These large ice crystals a~e remo~ed from the slurry by centrifuge Cl where they are ~ashed. They may be melted in heat exchsnge ~elationship ~0 with ~efrlgerant vapour heat exchanger, fusion tank FTl to cool and partially condense the compressed refrigerant ~apor~. Some melt~ng hea~ ~or the crystals ~ ~ :
may also be provided in HEl by cooling fresh Juice being ~ed into ~ulce holding -.
tank 3 which provides the feeds~ock F3 to vessel Rl. . ;
The melt o the crystals, ~ypically water, is then removed `
r~m the sy~tem via vacuum column 5 ~here adhered refrigerant vaposF ~e :
~tripped. The water i~.dlscarded or if the water iB 8 desired end product, as in pur~fication of brackish water, the water is utillzed in lt~ pure form.
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~L069427 First stage vessel Rl which may be a cont~ct column, is preferably maintained at about -5C durlng juice concentration, in order to obtain a æubstantially pure ice c~ystal.
The mothe~ llquo~ is continuously ~ecycled into vessel Rl from centrifuge Cl together with any water. ~ port~on of the flrst stage con-centrated mother liquor frum centrl~uge Cl i8 pumped into the second stage contact vessel R2. This contact vessel ~ operates in a manner 6imilar to that of the fir~t stage contact vessel Rl. It is al80 cooled by ~he in~ection o~ refrigerant, but it ls cooled to a lower temperature at whic~ another slurry 10 of a portlon of crystals ~orms in a ~urther concentrated mothe~ liquor. The `
type and proportion of the cry~tals depend upon the lower temperature to ~hich vessel R2 has been ad~usted. Thu6 if desired, t~o different crystallizable components can be selec~ively removed, o~e crystalllzing at the temperature of vessel Rl Yia centrifuge CI and the other crys~alllzing at temperatures dow~ to the lower temperature o~ second ~tage vessel ~2 via centrifuge C2.
The cry6tal~ from the ~irs~ stage centri~uge-Cl are washed, ~emoved from the ~ystem and the~ melted in heat exchanger PT2 by refrigerant gases in a si~ilar manner as descrlbed aboYe. These crystals ~re o~ high purity from the first c~ystallizàbile ccmponent.
The crystals ~rom the second stage cooling removed from the ~econd centrifuge C2 except where specifically desired for selecti~e ~eparatlon a~ set`forth above~ are melted and the melt is reintroduced and recycled into first stsge contact ~essel Rl thus recovering any i~corporated and ad-herent mother liquor on these crystals. ;
In the case of fruit ~u~ce~, this effect is utilized i~ order to obtain very high conce~trates of the ~ruit ~uice solids. ~ow~ver, in each ., . . .
ca~e, the ~urthe~ cooling i6 ~lways perfor~ed ~ ~he sa~e manner and the ~
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~L11)6~9L~L~7 c~yst~llizing portlon o~ the ~lu~y o~ c~ystals ~rom the second and successlve stage vessels R~ which is separated a~ centri~uge C2 ls returned to the first vessel Rl in order thereby to preserve the low level of crystallizable com-ponents of the already co~centrated ~other liquor. It also provides control for the separation in an active manner of the second crystalllzable components ~hich are crystallized down to the temperature o the second contact vessel opera~ing temperature.
In the case o~ fxuit ~uices, crystals separated by the second centrifuge C2 are melted and passed into the ~irst reactor. These second crop crysta~s are utilized in FT2 a~ a coolant ~or the compressed re~rigerant ;
during their melting in order t~ condense i~ partially to liquid ~orm. At the , same time, any incorporated and adherent ruit ~uice concentrate mother liquors are not lost. ~
When the desired sep~ration of cryst~llizable componentR has ;
been obtained, a portion o~ the ~inal liquid co~centrate, from centrifuge C2 i8 degased, stripped of any re~rigera~t there~ and is removed aB the fi~ished final concentrate.
The CryBtalS sepaxated by the firs~ stage ce~trifuge Cl are melted in heat exchange relationship ~or the cooli~g and partial condensing 20 o~ the campre33ed refriger~nt and a portlon o~ this is then used as the wash in centrifuge Cl. This wash liquor is ~hen returned to the ~irst contact ~essèl Rl ~n order to pxevent losses o~ ~other liquor.
The entire cooling system is designed or direct liquid `
ln~ectlon o~ t~e re~rlgerant into the contact ves6els Rl~ R2. After e~pansiDn, t~e xe~rigerant ~apors are continuously ~lthdraw~ at the top of the ves~els, cooled and recondensed as is usual in c108 d~cycle treatmen~ o~ refr~ge~ant ,~
gase~. These gase~ may be compressea by con~entional c~mpre~sors and the c~pressed gase~ are then cooled and liquidl~led for re~Re~ :~
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1(3694Z7 The ~oces~ o~ th~ ~nyent~on m~ be c~r~ed out ~th varied refrlgerants dependlng upon ~inal ef~ect and the mother liquor to be co~-- centratèd and treated. Tests ha~e been successfully conducted in pilot plants with propane, ammonia> carbon dloxide, methylene ehloride~ methyl chloride diflurodichloromethane~ tsifluoromonochloromethane and their derivatives (Freons T.M. and Frigens T.M.).
The adlabatic coollng wlth each of these re~rigerants proceeds ;
without a~y difficulty. It should be noted tha~ the usual precautions s~ould be taken with carbon dioxlde a6 the refrige~ant in order to a~oid freezing problems in the lnJection valve3. It i8 o~ten adYantageous if the re~rlgerant is solu~le in the mother llquor being treate`d. Soluble ~ePrigerants in the ~other liquor e~ert a favorable in~luence on the lo~ering of the viscosity of the h~ghly conce~tra~ed mother liquors. It has also been noted ~hat the dissolved refrigeran~s in the ~other liquor exert favorable influences upon the rate and type of cryætal formation.
Soluble re~rigerants have been noted to be especlally use~ul in the concentration of ~ruit j~ices as they permlt ~he highest degree of concentration of th~ solutes ~hile a~oiding pumpi~g problemæ with the highly ~iscous concentrate~ oontaining ~igh proportions o~ sugars.
. Tha proce~s described ~ay be carried out under various conditicns of pressure within the contact ves6els. I~ iB advantageous ~or the proce~s to be carried out a~ atmo pher~c pressure. However, pres6ure6 below ambient and 6uper ~tmospheric pres~ures may al60 be utilized in the contact ve~els Rl 2nd R2. For eKample, it has been ~ound that when the process is .
carried out under pressures above a~mospheric, large amounts of liquid re~rigera~t remain in the resulting slurry. These amount~ are reduced whe~ the prooea6 :
is operated ~t lawer pre~sures.
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. - . . -, . . , - ~ ' ~(~6~Z7 These di~e~ential amounts o 1uid refrigeran~ ~e~aining in the concentrate may be advantageously ut~lized~ ~or e%ample, ln ~he case where water is to be remo~ed from delicate pharmaceutlcal oil emul~ions a~d the pxocess is carried out with propane as a coolant. ~hen vessel Rl is at atmospheric pressure and, at a temperature o~ about -3C, approximately 6 to ~j 10% of the propane remains in the emulsion. If however, the process is carried out, approximately 3 atmospheres, then up to 30% of the prop~e remains dl~-solved ln the oil5 thereby keeping the resul~lng emMlslon in a fluid form.
Fhrther9 if the process iB carrled ont ut~llzing Freon 12 T.N. as the refrigerant, the refrigerant content ln the vessel at a pre~sure o~ 2 atmospheses 18 i~
sressed to o~er 60%. The resultan~ concen~rate i8 a completely mobile liquid which permits ease of pumping o~ the slurry before f~ltration of the resultant concentrate.
Con~ersely, when the op~ration i8 conducted in lower than atmospheric pxessures, the re~rigerant may be kept in the cooling vessel R
or in an ad~acent sec~ndary tan~. When operating under the~e conditions~
special crystallizati~n effects are obtained. For exæmple in the dewaxing of .., , edible o~l~, in which the presence of excess refrigerant ca~ have an adverse efect upon the type of cr~stals a~d on crystal gr~wth, it is pos~ible to ;l -achieve ~atis~actory cryst 1 growth by operating at lower than atmo~pheric pressure6.
Whe~ lt ls desired to obtain patticularly low temperature6, it i~ possible to achleve temperatures of -90C (using liquid air) without d~$ficu1ty depending upon the re~rigerant and the pressure wlthin the contact 1` ~ ` ~1. .
~ a preferred e~ample? f~e6h orange Juice was ~ub~ected c~nt~nuo~ concentrat~o~ trcatm~t utill~in~ dlc~lorodlfluoro methane (Refrigera~t 12) as refrlgerant, and a~ described bel~ws ;
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1~S94~'7 ~ esh o~ange ~u~ce ~3 Rt ~ te~pe~ature o~ 20S, previously clarlfied by centri~uging to be ~ree o~ sollds such as plts, pulp particles etc. is pumped by means o~ pump 1 through heat exchangers HEl 2nd HE2 into storage tank 3, maintained under a protecti~e atmosphere ln order to preserYe the vitamins and prevent oxidat~on. The temperature of the ~uice in tan~ 3 i~ about 7C. From ~ank 3 the ~uice i~ pumped into the upper part of the flrst stage cooling ~essel Rl which 1~ provlded in its upper part with a droplet separator ~not shown). The ~uice 10ws countercurrent to the rislng refrigerant vapors down over the plates into the lower widened part of the cooling vessel Rl which is equipped at lts bottom w~th several refrigerant in~ection valves 2. Val~es 2 serve to introduce the refrigerant directly into cooling vessel Rl.
The refrigerant ~rom pressuriæed storage ~essel 7 ls in~ected in the liquid phase into cooling vessel ~l at a pressure of about 5 atmospheres.
As a re~ult of the adiabatic expansion of the refrigerant ln cooling vessel Rl, the temperature o~ the ~ulce at the bottom of said cooling vessel Rl decreases to about -5C. ~s a result of the cooling to about -5C, the water compone~ of the ~uice freezes to ~orm a slurry o~ ice crystals in a mother liquor oP ~uice concentrate. The turbulance caused by the phase change of the sefrigerant provides ~or a homogenous slurry of the water crystalQ in the mother liquor. It also equal~æes the ~emperature within the slurry and prevents lump formation. ~ ;
The ln~ection of the refrigerant through ~alve 2 is controlled and regulated to insure that the ~lurry of ~ce crystal6 ln the ~other liquor r~mains fluid. Portions of this slurry are continuously discharged in~o ce~trifuge Cl- Crystal formation is l~i~iated at temperature~ in the sa~ge -l.5 to -2C. The ~ry6tal8 gro~ under the ~nfluence of ~he unifoxm temperature - 19 - :
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~106~t4Z7 within contact vessel ~ ~hlch ~s ma~nt~ned ~t ~5C. The c~ystals; in the case o~ ~r~zen fruit ~uice~ axe ~u~e ice.
Centri~uge Cl where t~e crystals are separated from the mother liquor is equipped with a ~ontinuously operating lce washing system. The ice crystals are washed with water to prevent losses of any Juice componentB
resulting from any ~ulce which adheres to the sur~ace o~ the ice crystals. .
At the initiatlon of the process belng desc~bed all o~ the Juice P~ that hag been centrifuged i~ recycled to ~egsel R~ by closing valve Vl and opening valve VlR. When the temperature in vessel Rl has stsbilized at about -5C, the second stage concentration step is initiated by ope~ing ~al~e vl and partially closing ~al~e v~ t about 5C approximately 50% of the water has been crystallized ~rom the ~u~ce. It 1~ ell~i~ated as ice via centrifuge Cl.
- When second stage concent~atlon iB initiated i.e. when the .
temperature of vessel Rl has stabilized a~ -5, val~e 1 is opened 80 that between 20 to 50% of the preconcentrated juice l.e. the mother liquor is cont~nuously pas~ed ~rom centrifuge ~1 lnto cooling ves~el ~2. The propor~ons .
a~d conditio~s i~ first stage vessel Rl are ad~usted in such a manner that the temperature of Rl remains substan~ally constant and the feed amounts thereto are ~imilarly const2nt RO ~hat t~e amounts of fresh ~uice and re-cycled concentrated ~uice PlR thst is.already preconcentrated are continuously pasaed into ve~sel Rl and a part of thls first stage concentrate is pa~sed ~nto vessel R2 through val~e Vl.
The recycling ~ preconcentrated ~ulce to vessel Rl 3eFves to maintain a lo~ proportion o~ crystals to concentra~ed ~uice componentR in ~ .
order to pe~mit good lce~cryst31 grow~h thereiD. The growth of large lce c~ystsl8 provides proper and complete separation.
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The concent~ated ~u~ce ~l ~h~ch h~s been pumped into second stage vessel ~2 is further cooled by the ~njection o~ additi~nal refrigerant through multiple valves 2 into the lower section o~ vesæel ~2 thus further cooling this mother liquor. ~ ~ortion of the refrlgeran~ dissol~es in the 81urry which includes the addltional crystals ~hich form i~ ve~sel ~2. This dissolved refrigerant reduces the ~i~co~ity o~ the concentrated slurry S2 in vessel R2. Even when the coolant is insoluble ln the slurry, the homo-geniety of the slurry is preserved as a result of ~he turbulance caused by - the boiling refrigerant and in addltlon, the added liquid provided by the immisctble rafrigerant contributes to the mobillty of the cGncentrated ~lurry S~.
~ s a result o~ the d~rect in~ection o~ the refrigerant, the temperature in vessel R2 is reduced~ addltional ice forms to create slurry S2. Tha slurry S2 i8 led continuously f~om vessel R2 into centrifuge C~.
I~ this second stage, the entire amount of mother llquor P~ leaving centri-~uge C2 1~ recycled to vessel R2 where an equilibrium ~empera~ure of -9 to -11 is maintained. This temperature range ls prefexred as at -8C about 65 to 70% of the initial water content of the Juice ~ill be crystallized as ice. Thls ice proportion increaseo to 72% at -9C; to 78% at -10C, and to 85% at -llGC.
The ~uice concentrate from centrifuge C2 is recycled to ~esæel ~ through valve V2R until ~n equilibrium temperature ~ithin ves3el R2 has been reached. This equilibrium t~mperature deter~ine~ ~he concentra-tion of ~he final concentrate.
:; ; .. , ~ hen the temperature in the ve~sel ~2 has become stabili~ed, a part o~ ~he centrifuged mother liquor P2 i5 pumped through fu6i~n tank -.~ .
heat eYchanger FT~ and th~n d~rec~ly to reduced pres~ure colum~ 4~ in ~hich ~ - - 21 --: ' ' ' -: ~ . , . ., . ~ . - : -106g4Z7 the temperature o~ the concent~ate ~ ~6C, ~t th~s tempe~ature9 there i3 a complete removal and stripping o~ an~ re~rlgerant which may be dlssolved in this ~inal concentrate which i9 the desired product. ~s a resul~ of the high degree of sugar concentration of the co~ponents o~ the ~uice in vessel R2 the water csystals I2 separated by centri~uge C2 and ha~lng the t~mperature of -10C are microcrystalline in ~oxm. Thls for~ of ice crystals is very difficult to separate ~rom the liqui~ ~uice~c~mponents, portions o~ which adhere to the microcry6tals. These sèparated crystals I2 are melted in fusion tank FT2 and a~ter melting are ~ed directly to ~irst ~essel Rl. The low temperature o~ the micr~crystal~ i~ used in heat exchange~s such as ~T2 to partially condense the compre6sad refrigerant on lts way to refrigerant pres6ure vessel 7. In additlon, any ~uice co~ponents adsorbed on or contalned ~ithin the microcrystals are secycled by reintroduction into ~irst stage cooling vessel Rl. ~ :
In addition, the first stage mother liquor Pl is continuously sub~ected to a reconcentration process a~er centrifuge Cl in the ~ollowing manner: The slurry of crystal~ ~ ~rom Rl, at a ~emperature o~ ~4 to 59 : ~.
and i~ separated at Gl, to yield ice ~rystals in substantially pure form-20 to 90% of the ~other liquor Pl is recycled to vessel Rl through valve V1R~
~0 and the res~ ls transferred to vPssel ~2. .
At the 8ame time, the fresh ~uice continuously enters ~rom .
storage tank 3 into vessel Rl. Simultaneously, the crystals separated by ~
centrifuge Cl are washed with a part of the water Wl obtained in ~usion tank .
FTl. This ~ater Wl which representg about l/4 of the melted ice stream ~ i~
utilized ~ the cen~ri~uge Cl ~or washing. A~ter washing, all o~ the wash water i8 recycled to flrst ~tage veQsel Rl. The remainder of the water, ~ot ~ .
U8ed for w~shing~ pa~ses th~o~gh he=t excbange~ ~El and the~ to colum~ S where .
- 22 - ~ . . :
..
' ' ; ,' '-: ' ' '~.':
- , . ., . .. . ~ ,~ , .. .. ~ . :
it is stripped fro~ anyentrained refrige~ant gases. This water from column 5 i9 removed from the system and the re~rigerant gas ls recycled.
A portion of the second stage concentrate P2 which is the liquid separated from the ice in centrifuge C2 is transferred to column 4 where any dissolved refrigerant is stripped and the concentrate thè final product, is removed from the system.
All of the refrigerant introduced into the system into the cooling vessels Rl and R2 and vapori~ed through ~alves 2 and 2A is pumped from the top of the vessels Rl and R2, through a droplet separator (not shown) and led to compressor 6. These gases are generally rem~ved at about atmospheric pressure. However, ~Jhen special effects are desired i~e. when some refrigerant liquid is to remain in the juice concentrate in order to lower its viscosity, it is advantageous to operate at higher pressures in different stages at ~essel Rl and R2.
The refrigerant gases from cooling vessels Rl and R2 are Ped to compressor 6 where they are compressed and then cooled and condensed to liquid state via heat exchangers which are fusion tanks FTl and FT2, and if necessary, with the help of an e~ternal refrigera~ion circuit HE4. The liquid condensed refrigerant is then led to and stored in tank 7 from where it is injected into vessels Rl or R2 as needed for refrigeration.
The above operation is substantially the same for all types of fruit juices. The specific temperature maintained in reactor R2 depends upon the desired final concentration of the ~uice concentrate. Consequently any crystallizable product can be processed by this method. The products can be further processed by additional stages until total removal of~the initial solvent, diluents and other undesirable crystallizable materials is achieved.
To this end, a four-stage process is ~ho~n in ~igure 2. The only differences .
; - 23 - -;: .
, - , : ~ . : , . .
- . .:
.
~f;9~'7 between ~i~u~e 1 and F~gu~e 2 ~e t~e ~dd~t~onal ~stageS and the ~eplace~ent .
o~ stripping column 4 b~ equipment which per~its wlthdrawal o~ the final product as a solid ~ a screw expellor i~ such ~s its nature.
The ~eedstock llquids contalnlng the crystall~zable substance may be treated with o~her dil~ents which may be soluble or lnsoluble in the product. Furthermore, various o~ the illustrated process and a~paratus components may be interchanged by art-recogn~zed equivalent~.
For instance, the cent~i~uges ~ay be re~laced by ~llter~ and/or filter presses. Sim~larly, screw expeller~, Blrd filters and other ~uitable equipment ~or the r~oYal o~ the crystals ~rom the mother liquor may be utillzed.
The actual configuration o~ the cooling ~e~sels Rl and R2 wherein the ice i~
formed may vary with the slze of the equipment being used, heat exchange conditions~ nature o~ the re~rigerant and the a~bient surroundlngs which include the am nt and degree of insulation nece~sary.
Because of the utilization of the re~rigera~t as a secondary ~olvent, ~he present invention make6 it posgible for the process to be carried out withou~ any difficulty to a de~ree whereby a total re~oral o~ all the water or other crystallizable sol~ent without any after treat~ent at elevated temperatures. By the continuous recycllng techn~que at the f~rst stage, crystals of large size, are formed and continuously removed. In addition, by careful control and design, expedient~, permitted by the proces~, it is :
po~sible to achieve great economy of energy exchange through the ~udiciou~
use of heat exchanger~ between the cooled materlals and the warmer materials.
Nany varied coolants may be ~sed depending upon the naturé o~ ~ -the proauct to be concentrated. For an exa~ple, good result` ha~e been ¢btained with the followi~g products a~d by the li6ted refrigerants used there~ith.
' .' - 24 ~ ~
.
, . . . . . . . , - . , . - . . . .
:10694Z'7 TABL~ .
~EEDSTOCK . ~ . __ Rr~ R~C - .
~ruit Juices ~ropane ~reon 12 Freon 22 ~T.~
... . . . .. . .. Carbon . l~iox~de .. .
. ~ ~
Beer . ..... . . . .. Carbon ~io~ide .
. _ . , ~
Wine Freon 13 (T.M.) . .. . . . . . Carbon.Dioxide ' - ' - ~ _ . ~ .. ._ _. . ~
Edible Oilg' ~ethylene Chloride ;
Methyl Chloride .
Carbon Dioxide ~ -... ............. Propane . ~ ~
~ylene . . . .... .. ....... Liquid.Ammonia. .
___ . . . . j~ . .
~ilk . . . . . . . Freon 13. . . .
~ . . . . _ _ . . ._ Pharmaceutlcal.Emulsions . . ..... . ... . . . Propa~e. . . . . . ~
_~ ......... . . . , .. , . . . _ . . .
Antibiotic Fe~me~tation Beer~ Propane . . . . Carbo~.Di~xide . . .
. _ . . . . . :
Botanical E~tracts Propane ~
Carbon Dioxide ~ .
.
. . .. . . :. . .... Freon.22.... ... .... . .
__ .. . .. ... ., The temper~tures ~ithin the cooling ~essels ~ snd ~2 ~ay be ~
ad~u ted ~ccording to the desired e~fec~6~ It ~ pos6ible ~o utiliz ~hs :
standard cooli~g to~ers withsut any di~f~culty provlded that in~ulatio~ is .
adequate, at temperature~ ranglng ~rom ~90C to up to ~20C. Fu~t~er, the ..
~ate o~ cooling can be accurately:co~t~olled by the amount o~ ~efriger~nt ~ .
~ntroduced l~to vessels ~ and ~2. : ~ . :
: ~ 25 - .
~
lU~9~'7 The p~esent inrent~on~ ddition~ ~ovldes p~ecise control oX the crystal slze o~ the matertal~ whlch are crystalllzed during the first stage. By control o~ the cooling, the cry~tal slze can be controlled to provide large crystals and consequently purer crystals. In addition, to achieving control by a slower re4~igerant in~ection, change~ in the diameter of cooling veqsel Rl and R2 and ~rying the rate of feed o~ the liquids and the amount of recycling o~ mother liquor can also control the ~rowth of ~he crystal~.
~n interesting aspect o~ the present prnce~ the contrnl of differlng crystal sizes depending npon the concentration of the ~uices to be treated. Thus in the flrst stage cen~rifuge, Cl, the centrlfuge screens may be relatively coarse i.e. 60 ~o lO0 mesh per inch (0.4 t~ 0.25 mm opening) sizas are sufficient. However, ln the second ~tage, centrifuge C2, it is preferred to haye smaller screen openings. I~ it is desi~ed to insure that -the Plnal ~ice concentration have between 80 and 85% of the water remoYed, the screen opening diameter should not be oVe~ 0,1 mm. The substantial amounts of the fresh Juice which adhere to snch microcrystals ar~ recovered because they are recycled to ~essel Rl a~ter leaving hea~ exchanger usion tank ~T2 form~g ~ream ~ .
While the above de6crip~io~ ha~ been confined to describing the operation for concentrating fruit ~uices to the degree where approximately 80X of the water has been removed, the process i~ similarly u~eful in con-centrating beer6 to remove exces~ water prior to shipment, for the concentrationof cry3tallizable from non-crys~allisable com~onents o fatq, for the separa~lo~ of the xylene i80mer8~ for the freeze concentration of milk.
concentration of botanical extract~, teas, and the ~reabme~t of ~ariou~ labile ant~blotic fen~entation bee~s ln order to concentrate ~he sntibio~ic con~ent6 `
thereo~
- - 26 ~
": ' . ' ' :' , '' ' ' .': ' .,, ~" ',.' ', . '', ., ~. '~ :'.' The p~ocess desc~bed ~o~ the ~uice~ are ~e ely ~xemplary and the above art rec~gnlzed e~u~valentg can be subgtitu~ed for the ~ulces ~n the operations o~ the process described aboYe. ~urthermore3 any apparatus units can be substituted-by thelr art-recognlzed ~unc~ional equi~alents, All such art-recognized equivalents are intended within the scope of this lnven~lon3 no~ claimed. .
1~ ' ' .
.
~ 27.' `1:
!:
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. . .. . - . ~ . - ~ . . . . . . . . . ~ . ..
. .. . . . . . ..... i : .~ . ~ ..
Claims (15)
PROPERTY OF PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for concentrating a solution and for separating crystallizable components from a solution thereof which comprises introducing said solution into a first crystallization zone, spraying a highly volatile, pressurized and liquified cooling agent directly into said first crystallization zone into contact with said solution, wherein said cooling agent expands and cools said solution to a temperature sufficient to form a slurry of crystals of a first crystallizable component therein, maintaining said temperature constant, separating said crystals of first crystallizable component from said slurry to form a preliminary concentrated solution, transferring substantially only said preliminary concentrated solution to at least one further crystallization zone separate from said first crystalli-zation zone, spraying said cooling agent directly into said further crystallization zone into contact with said preliminary concentrated solution in an amount sufficient (a) to expand and cool said preliminary solution in said further crystalli-zation zone sufficiently below the temperature of said solution in said first crystallization zone to form a further slurry of crystals therein and at the same time (b) to act as a liquefacient for said further slurry and thus reduce the viscosity thereof, the temperature of said preliminary concentrated solution in said further crystallization zone being such that the total of the crystals formed in said first and said further crystallization zones is about 65 to 100% of the crystallizable components of said solution, separating said crystals from said further slurry to form a concentrated solution containing liquefied cooling agent and separating said cooling agent from said concentrated solution.
2. The process according to claim 1, including the steps of collecting, compressing, condensing and recycling expanded said cooling agent.
3. The process according to claim 1, in which said cooling agent is soluble in said solution.
4. The process according to claim 1, wherein said solution is selected from the group of liquids containing dissolved crystallizable substances consisting of fruit juices, ferments, extracts, beers, milk and brackish water to yield concentrates of comestible or potable materials.
5. The process according to claim l, wherein said cooling agent is selected from the group of refrigerants consisting of low-boiling high-vapor pressure, saturated and unsaturated aliphatic hydrocarbons having four or less carbon atoms and halogenated derivatives thereof, carbon dioxide liquified air, ammonia and mixtures thereof which are nondegrading with respect to said feedstock mixtures.
6. The process according to claim 1, in which a fraction of the preliminary concentrated solution is recycled to the first crystallization zone, and a fraction of the concentrated solution is recycled to said further crystalli-zation zone.
7. The process according to claim 6 wherein said process is utilized for selectively separating crystals of different melting point components, in such a way that the components are kept in separate circuits including individual successive crystallization zones and thus are completely crystal-lized as a result of the continuous recycling, thereby obtaining products of high purity.
8. A process according to claim 1 in which only part of said preliminary concentrate is transferred to said further crystallization zone, the remaining preliminary concentrate being recycled to the first crystallization zone.
9, A process according to claim l in which said cooling agent is sprayed into and expanded in said first and further crystallization zones counter-current to the flow of said solutions and at such a rate as to create turbu-lence within the respective solution and to produce a substantially homo-geneous and fluid slurry of crystals and to prevent lump formation and sedi-mentation.
10. A process according to claim 1 in which said crystals separated from said further slurry are recycled to said first crystallization zone and said separated crystals of first crystallizable component are washed and recovered as substantially pure products.
11. A process according to claim l, in which said solution is a fruit juice to be concentrated in which the liquid part of the major portion of said further slurry of crystals is recycled into said first crystallization zone and said crystals separated from said further slurry are also recycled to said first crystallization zone and in which the concentrated solution obtained after the separation of said crystals from said further slurry and the sep-aration of said cooling agent is removed as finished product.
12. The process according to claim 2, wherein heat exchange between said crystals separated from said first and further crystallization zones and said cooling agent is effected for at least part of the condensing step.
13. Apparatus for concentrating mixtures from a feed stock of a dissolved mixture of components including crystalliz-able solvents and crystallizable or amorphous solutes which comprises, at least a first and a further contact vessel, refrigerant compressor means, means connecting the refrigerant compressor for introducing liquid refrigerant into said first and further contact vessels, means for introducing feed stock into the first contact vessel;
means for evacuating refrigerant from said first and further contact vessels for permitting vaporization and cooling of said refrigerant and substances in said vessels, means for returning vaporized refrigerant from said vessels to said compressor, said feed stock being cooled in said first contact vessel to a first stage temperature below the freezing point of a first crystallizable fraction, means for extracting said first crystallizable fraction with entrained mother liquor from said first contact vessel and unvaporized quantities of refrigerant, means for recovering said first crystallizable fraction as first crop crystals and separated mother liquor, means for recycling a portion of said separated mother liquor to said first vessel, means for transferring the remainder of said separated mother liquor to said further contact vessel, said mother liquor being there further cooled to a second temperature below said first temperature and forming a second crystallizable fraction and entrained further concentrated mother liquor with unvaporized liquid refrigerant mixed therewith, means for recovering said second crystallizable fraction as a second crystal crop with adhered further mother liquor and further separated concentrated mother liquor and liquid refrigerant, means for melting and recycling said second crystal crop with adhered further mother liquor to said first contact vessel, means for recycling part of said separated further concentrated mother liquor to said further contact vessel, means for stripping refrigerant from the remainder of said further concentrated mother liquor and for returning said stripped refrigerant to said compressor, and means for recovering the stripped mother liquor as a concentrate.
means for evacuating refrigerant from said first and further contact vessels for permitting vaporization and cooling of said refrigerant and substances in said vessels, means for returning vaporized refrigerant from said vessels to said compressor, said feed stock being cooled in said first contact vessel to a first stage temperature below the freezing point of a first crystallizable fraction, means for extracting said first crystallizable fraction with entrained mother liquor from said first contact vessel and unvaporized quantities of refrigerant, means for recovering said first crystallizable fraction as first crop crystals and separated mother liquor, means for recycling a portion of said separated mother liquor to said first vessel, means for transferring the remainder of said separated mother liquor to said further contact vessel, said mother liquor being there further cooled to a second temperature below said first temperature and forming a second crystallizable fraction and entrained further concentrated mother liquor with unvaporized liquid refrigerant mixed therewith, means for recovering said second crystallizable fraction as a second crystal crop with adhered further mother liquor and further separated concentrated mother liquor and liquid refrigerant, means for melting and recycling said second crystal crop with adhered further mother liquor to said first contact vessel, means for recycling part of said separated further concentrated mother liquor to said further contact vessel, means for stripping refrigerant from the remainder of said further concentrated mother liquor and for returning said stripped refrigerant to said compressor, and means for recovering the stripped mother liquor as a concentrate.
14. Apparatus as defined in Claim 13 comprising heat exchange means for cooling said feed stock before introduction to said first contact vessel, said heat exchange means comprising means for exchanging heat between said first crop crystals and said feed stock and means for exchanging heat between said remainder of said further mother liquor and said feed stock.
15. Apparatus as defined in Claim 14 including means for condensing refrigerant leaving said compressor and before introduction to said first and further vessels, comprising heat exchange means between said first crop crystals and compressed refrigerant subsequent to said heat exchange between said first crop crystals and said feed stock.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA256,896A CA1069427A (en) | 1976-07-13 | 1976-07-13 | Process and apparatus for the freeze concentration of solutions |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA256,896A CA1069427A (en) | 1976-07-13 | 1976-07-13 | Process and apparatus for the freeze concentration of solutions |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1069427A true CA1069427A (en) | 1980-01-08 |
Family
ID=4106421
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA256,896A Expired CA1069427A (en) | 1976-07-13 | 1976-07-13 | Process and apparatus for the freeze concentration of solutions |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1069427A (en) |
-
1976
- 1976-07-13 CA CA256,896A patent/CA1069427A/en not_active Expired
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