[191
`United States Patent
`[11] Patent Number:
`4,702,798
`Bonanno
`[45] Date of Patent:
`Oct. 27, 1987
`
`5/1953 Germain ... . . .
`. . .... 34/9
`2,637,119
`2/1955 Kearfott et al.
`.
`.. 34/9
`2,702,771
`
`.. 34/9
`3/1960 Johnston .... ..
`2,929,150
`. 34/9
`3,003,247 10/1961 Sherliker
`3,005,266 10/1961
`van der Sanden et al.
`3,034,968
`5/1962 Johnston ..........
`3,251,398
`5/1966 Greenfield
`3,540,513 11/1970 Sumiya etal.
`3,734,160 5/1973 Osdor ...........
`. 3,855,079 12/1974 Greenfield et al
`3,903,012
`9/1975 Brandreth ........
`3,917,508 ll/1975 Greenfield et al
`3,950,230 4/1976 Greenfield et a1
`3,962,798
`6/1976 Jackson ........
`3,988,414 10/1976 Klicka et a1.
`.
`4,011,661
`3/1977 Sezaki et al.
`4,090,307
`5/1978 Gollmick et :11.
`4,161,450 7/1979 Vitat et a1.
`4,270,974
`6/1981 Greenfield et a1
`4,276,115 6/1981 Greenfield et a1
`4,518,458
`5/1985 Greenfield et al.
`
`'
`
`..159/47.1
`159/47.1
`34/9
`159/47.1
`. 159/]
`
`
`
`I 159/17
`159/47.1
`..
`
`Primary Examiner—Wilbur Bascomb
`Attorney, Agent, or Firm—Richard L. Cannaday; John
`F. Smith; William J. Ungvarsky
`[57]
`ABSTRACT
`A continuous process and apparatus for drying aqueous
`solids by evaporation using a fluidizing oil and a surfac-
`tant wherein the fluidizing oil and surfactant are recov-
`ered and recycled separately or together. The aqueous
`solids may, or may not, have a heavy, natural oil associ-
`ated with them.
`
`12 Claims, 6 Drawing Figures
`
`[54] PROCESS FOR RECOVERING DRY SOLIDS
`FROM AQUEOUS SOLIDS MIXTURES
`
`Inventor:
`[75]
`[73] Assignee:
`
`Anthony J. Bonanno, Parsippany
`Hanover Research Corporation, East
`Hanover, N..I.
`
`[21] Appl. No.: 17,720
`[22] Filed:
`Feb. 24, 1987
`
`Related U.S. Application Data
`Continuation of Ser. No. 683,719, Dec. 19, 1984, aban-
`doned.
`
`[63]
`
`[56]
`
`Int. Cl.‘ ............................................. .. B01D 1/26
`[51]
`[52] US. Cl.
`...... 159/474; 159/111;
`159/47.3; 159/DIG. 25; 159/DIG. 13; 34/9;
`34/57 R; 203/14; 203/47; 203/48; 203/51;
`203/7
`[58] Field of Search ........... .. 159/47.1, DIG. 13, 47.3,
`159/48.1, 17.1, DIG. 3, DIG. 10, DIG. 25,
`DIG. 33, , 901, 905; 203/12-19, 47, 48, 51, 98,
`7; 34/9, 57 R; 202/176, 202; 165/104.11
`References Cited
`U.S. PATENT DOCUMENTS
`Re. 26,317 12/1967 Greenfield
`1,960,917
`5/1934 Nagelvoort
`2,137,404 11/1938 Hollerer
`2,472,794 6/1949 Cothran
`2,503,913 4/1950 Kimberlin, Jr. et a]
`2,552,706
`5/1951 Bertram
`2,611,751
`9/1952 Scott ..............
`
`159/47.1
`34/9
`34/9
`34/9
`34/9
`.. 34/9
`
`
`
`HERIYIIL
`
`(cid:0)H(cid:0)Y(cid:0)D(cid:0)R(cid:0)I(cid:0)T(cid:0)E(cid:0) (cid:0)E(cid:0)X(cid:0)H(cid:0)I(cid:0)B(cid:0)I(cid:0)T(cid:0) (cid:0)1(cid:0)0(cid:0)0(cid:0)6
`

`
`U. S. Patent Oct. 27, 1987
`
`Sheet1of6
`
`4,702,798
`
`§z,_a-§_g...awzgzs
`
`3~_
`
`552_.~a__E
`
`3w555.25
`
`
`
`$23.2:mS$_E¢>m.3EN.2
`
`eazsa52,
`
`
`
`.\Gxk5.2.5zzsga
`
`_._§.§22
`
`22§.2_§E,
`
`255$
`
`gaé_
`
`2:3
`
`2.H.S:5:.
`
`~__§“__.EEaa>o§_
`2.852.,
`5.In2:3355,55
`
`
`...\:E32523E<_:m§3‘l
`
`zééaL5ease.
`
`2:5
`
`E<_E§
`
`5553
`
`$5.3
`
`._5:5:maea
`
`(cid:0)H(cid:0)Y(cid:0)D(cid:0)R(cid:0)I(cid:0)T(cid:0)E(cid:0) (cid:0)E(cid:0)X(cid:0)H(cid:0)I(cid:0)B(cid:0)I(cid:0)T(cid:0) (cid:0)1(cid:0)0(cid:0)0(cid:0)6
`
`
`
`

`
`U. S. Patent Oct. 27,1987
`
`sheétz of6
`
`4,702,798
`
`‘I10 O3ZlH0dVI\-HV3l3 5)Nlh\O'l8 1NEln'\:H3
`
`W313 ONIMOWH
`
`LIVE BOTTOMBIN
`
`3|6
`
`SOUDS
`
`U?x<\.l
`
`
`
`GRINOER
`
`$- (U0-!N’)
`8no
`0'83cumto
`
`3|8 9....
`3
`
`<\Ito
`no
`3InCU
`
`N
`
`<9‘cman
`
`DRYSOLIDSPRODUCT
`
`290
`
`2l4
`
`
`
` ‘
`
`LNVLOVOJOS sma WIO LHOH
`
`XIW 3803-1|O'SOl'1OS SOOHOAHNV
`
`:2
`NaC\J
`
`OENTRIFUGE
`
`214
`
`
`
`LIGHTFLUlO|Z|NGOlL+SURFACTANT
`
`xCV61
`
`.
`
`<0<1-
`txl
`
`9-
`155
`45%
`_'_.E:.
`5°’
`
`<9no
`N
`
`er
`3
`
`:1:LuL3(/2Lu
`_I
`-1cu
`
`0
`
`
`
`
`220
`
` SLVSNEIONOO‘IIO-H1l.VM
`
`:1-co
`CH
`
`3Hfl.LXlH ZIHOS-'\lO-SO|'1OS SOOJOOV
`
`SLVSNHONOO '|lO-H3lVM
`
`2|l SURFACTANTcnmczAND MAKEUP
`
`(0V‘
`CU
`
`cf).9...aoco 2' ZR
`
`o
`Al
`“'
`
`—
`==
`1
`cu
`‘,‘‘92
`
`5
`3::
`E5
`-1 2zo<2:
`cm L440-
`5
`co*”
`Ncu
`
`
`2”runo-
`
`
`
`EILVSNEONOO ‘HO-!ElVM
`
` l. E
`
`;,
`a
`8
`- '1l0-SOHOS TN O3J.\1HOkH3O A'|'NLLHVd <\l
`
` o
`
`(cid:0)H(cid:0)Y(cid:0)D(cid:0)R(cid:0)I(cid:0)T(cid:0)E(cid:0) (cid:0)E(cid:0)X(cid:0)H(cid:0)I(cid:0)B(cid:0)I(cid:0)T(cid:0) (cid:0)1(cid:0)0(cid:0)0(cid:0)6
`

`
`U. S. Patent Oct. 27, 1937
`
`Sheet3 of6
`
`4,702,798
`
`4an1%.=oaN_.s._§4:55
`
`3HnJ.X|N '.-IHHS
`
`.m:.:_o
`
`HHSNEGNOO
`
`
`:22lg
`
` W%.§_2_vE§3..'.E6....EF.N2...tas.$2.5.
`
`2..avW.WMWMMWmMMWmNE.W9:3mG.|0mmMMHOmmm’mmN;mMMWVIAMW»ImMEnmm3__.M.3WM._a._§
`umm2.35%;m.Mm.:Es_._amm32..
`
`6.
`
`,E.__ESNewAv
`
`vHH:1.;..00
`asme3:5:E4325:
`
`Ras£553..52.2..
`
`EE3a.=o
`
`8....3Egsmm
`E8m:<8
`
`ms.0:
`
`we
`
`Evan
`
`_E;$2.38‘V3.VN:
`
`E:<>2;.V
`
`(cid:0)H(cid:0)Y(cid:0)D(cid:0)R(cid:0)I(cid:0)T(cid:0)E(cid:0) (cid:0)E(cid:0)X(cid:0)H(cid:0)I(cid:0)B(cid:0)I(cid:0)T(cid:0) (cid:0)1(cid:0)0(cid:0)0(cid:0)6
`
`
`
`
`
`

`
`U. S. Patent Oct. 27, 1987
`
`Sheet4 of6
`
`4,702,798
`
`H6‘. 4.
`HEAVY OIL
`
`
`
`
`l5“SOLIDS
`90;HEAVY 01L
`(145
`SURFACTANT
`
`n
`'5 505-195
`5"HEA\(Y on
`
`- OIL
`
`FEED
`
`
`85" H20 I5” SOUDS
`
`
`90”HEAVY OIL
`'
`
`045"SURFACTANT
`
`S!
`
`l§Q4¥3_Wfl_L
`
`90, “EM OIL
`{ 0.45"SURFACTANT
`
`% 104
`
`
`
`0.025’*SURFACTANT? I08
`
`'
`
`60”
`HEAVY OIL
`
`I I0
`
`0.025“
`SURFACTANT
`
`
`
`5,50%
`.e“0{1L1zAv¥
`\‘[0
`GRINDER 60
`
`
`
`88.4‘ HEAVY OIL
`0.45” SURFACTANT
`
`
`
`(cid:0)H(cid:0)Y(cid:0)D(cid:0)R(cid:0)I(cid:0)T(cid:0)E(cid:0) (cid:0)E(cid:0)X(cid:0)H(cid:0)I(cid:0)B(cid:0)I(cid:0)T(cid:0) (cid:0)1(cid:0)0(cid:0)0(cid:0)6
`

`
`U. S. Patent Oct. 27, 1987
`
`sheéts of6
`
`4,702,798
`
`FIG. 5
`L|GHT OIL
`
`N0 NATURAL OIL IN FEED
`
`m5_45*‘ m1AL
`l95(;¥S0LlDT3 0
`UGH
`
`IL
`
`‘A
`
`I00” AQUEOUS SOLIDS
`
`
`
`
` 85* H20
`15* -souos
`
`I50‘ LIGHT OIL
`0.45” SURFACTANT
`
`EVAPO RATORS
`
`
`
`
`
`
`
`
`
`
`
`T
`15.0” souns
`
`250.45‘ TOTAL
`
`s5.o“’u<;HI
`OIL
`
`230
`
`150* um on
`045* SURFACTANT
`
`
`
`65‘ LIGHT 0lL
`OIL-WATER
`SEPARATOR
`
`
`
`
`
` 5.0‘ usm OIL
`
`
`
` l45.45" TOTAL 250
`I450 LIGHT 0lL
`045*’ sumcrnur
`
`‘—“" T4545” TOTAL
`145,0‘ ucm 0|L
`0.45 SURFACTANT
`
`
`
`(cid:0)H(cid:0)Y(cid:0)D(cid:0)R(cid:0)I(cid:0)T(cid:0)E(cid:0) (cid:0)E(cid:0)X(cid:0)H(cid:0)I(cid:0)B(cid:0)I(cid:0)T(cid:0) (cid:0)1(cid:0)0(cid:0)0(cid:0)6
`

`
`OIL
`
`UGHT
`W0“
`
`U.S. Patent Oct. 27, 1987
`
`She{=,t6of6
`
`4,702,798
`
`F/6‘. 6.
`LIGHT OIL
`
`NATURAL OIL IN FEED
`
`|5”ggUD3
`ygTLaRALT01LT
`9'Uo'LNLTTAc()1AN
`A
`
`TOO‘ AQUEOUS
`SOLIDS INCL.
`
`
`
`NATURAL OTL
`EVAPORATORS
`83.5“Hg0
`
`F559
`U0 45
`
`85.5’ H20
`:
`
`
`
`
`
`
`
`
`
`'_
`
`— +
`1.5” NATURAL OIL
`0.45'SURFACTANT
`90.0”LlGHT OIL
`"’ l615*LlGHTr
`
`IL
`190.45‘ TOTAL
`
`
`:— 5*‘
`145'“
`UGHT OIL
` so*L1cm OIL
`on
`
`
`so‘ ucm OIL
` <— 9o"LIcHI OIL
`0.025*SURFAc-
`TANT, ow
`
`NATURAL OIL
`
`
`
`CRYSTALLIZER
`
`145* LIGHT OIL
`0.45“ sumcmm
`LSTNATURAL OIL
`
`
`
`STORAGE
`
`
`
`-<—- 045* suarmnr
`
`
`
` 145*‘ LIGHT OIL
`1.5”‘ NATURAL OIL
`
`NATURAL OIL FOR EXTERNAL
`USE OR SALE
`
`
`
`TANK
`
`
`TL
`
`STNATURAL O|L
`
`544
`
`0A5”
`sumcmn
`
`(cid:0)H(cid:0)Y(cid:0)D(cid:0)R(cid:0)I(cid:0)T(cid:0)E(cid:0) (cid:0)E(cid:0)X(cid:0)H(cid:0)I(cid:0)B(cid:0)I(cid:0)T(cid:0) (cid:0)1(cid:0)0(cid:0)0(cid:0)6
`

`
`1
`
`4,702,798
`
`PROCESS FOR RECOVERING DRY SOLIDS
`FROM AQUEOUS SOLIDS MIXTURES
`
`BACKGROUND OF THE INVENTION
`This is a continuation of application Ser. No. 683,719
`filed Dec. 19, 1984, now abandoned.
`1. Field of the Invention
`This invention relates to a process for dehydrating
`solids in»aqueous solids mixtures and recovering said
`solids for further use. Specifically, it deals with a contin-
`uous process for drying aqueous solids using a fluidizing
`oil and a surfactant in an evaporation process wherein
`the fluidizing oil and surfactant are recovered and recy-
`cled.
`2. Discussion of the Prior Art
`The recovery of dry solids from aqueous solids mix-
`tures is the object of a large industry. Those solids,
`whether they be waste solids or valuable solids such as
`chemical solids for consumption by industries or feed
`for consumption by humans or animals, present many
`processing problems, both ecologically and relative to
`efficiency of production. There have been known many
`processes for economically producing dry solids and, at
`the same time, extracting the aqueous phase in a form
`acceptable for disposal or reuse. In order to facilitate
`those processes, some methods have used various fluid-
`izing oils so that the slurries formed can be dried at high
`temperatures and still
`remain pumpable. Although
`those processes efficiently produce dry solids and solve
`the ecological problem, there are still some difficulties
`associated therewith.
`In processes for drying solids by evaporation using
`fluidizing oils, the solids sometimes tend to form large
`masses that adhere to the inner walls of the pipeline,
`vapor chamber and heat exchanger tubes while the oil
`phase may be circulating with little or no wet solids.
`There are also instances where circulation is prevented
`due to the solids settling out and plugging the pipeline
`or circulating pump. Those wet solids, when not prop-
`erly dispersed and suspended, may coat the heat ex-
`changer surfaces and then dry as a scale reducing the
`heat transfer rate in the heat exchanger so that the evap-
`oration rate is reduced markedly and the efficiency of
`the evaporation is very low. Further, when those wet
`solids adhere to the walls of the evaporators, pipelines,
`or holding tanks, they can cause corrosion of those
`apparatus elements if the solids be of an acidic nature.
`There are also cases where a mixture of wet solids
`and oil
`in the fluidizing tank or feed tank are not
`pumped uniformly to the evaporator due to the settling
`of the solids and the imrniscibility of the two phases.
`That action tends to result in a disproportional amount
`of either wet solids or oil in the mixture sent to the
`evaporator and tends to upset the system.
`It is apparent, therefore, that there exists a need for a
`more efficient system for continuously dehydrating
`solids from aqueous mixtures without the aforemen-
`tioned problems.
`SUMMARY AND OBJECTS OF THE PRESENT
`INVENTION
`
`5
`
`l0
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`The process and apparatus of this invention comprise
`a series of steps and a systematic arrangement of equip-
`ment for continuously recovering dry solids from aque-
`ous solids. The process comprehends the use of surface
`active agents as an aid to causing a suspension or condi-
`tion of miscibility, in a multiple phase system of oil,
`
`65
`
`2
`water and solids for the efficient concentration and
`drying of products such as food, food wastes, chemi-
`cals, pharmaceutical wastes and sewage in a fluidizing
`oil.
`It has been found that the addition of a surfactant to
`the fluidizing oil
`in a dehydration process for drying
`solids in aqueous solid suspensions will eliminate many
`of the disadvantages of past processes allowing the
`suspensions to move continuously through the process
`in a more efficient manner using less heat and causing
`less detriment to the equipment used. The process com-
`prises the following steps:
`(1) Mixing aqueous solids with a fluidizing oil and a
`surfactant to obtain a mixture which is and remains fluid
`and pumpable before, during, and after removal of the
`water content therefrom;
`(2) Subjecting the resulting oil, surfactant containing,
`mixture of solids and water to dehydration by heat
`evaporation whereby substantially all of the water is
`removed by vaporization from the mixture or slurry;
`(3) Condensing and removing the water vapor;
`(4) Separating the bulk of the fluidizing oil and at
`least some of the surfactant from the solids;
`(5) Recycling the surfactant and the fluidizing oil
`back to the system, i.e., to the entry point of the aqueous
`solids feed;
`(6) Recovering the solids for use; and
`(7) Recovering any natural oil,
`i.e., oil associated
`originally with the solids, for use or sale.
`In the above process the surfactant may be separated
`from the fluidizing oil prior to recycle depending on
`which oil is used.
`By the use of a surfactant in the above dehydration
`process the following advantages may be achieved: an
`increased evaporation rate, a product of more uniform
`particle size, a reduction of viscosity with increase in
`pumping rate, a reduction of corrosion of metal parts in
`the equipment, depression of foam in the suspension,
`and reduction of boiling point rise. Those advantages
`result from the surfactant providing a more homoge-
`nous slurry of the particles in the fluidizing oil allowing
`for the continuous process to operate without interrup-
`tion because of clogging or deposits throughout the
`equipment.
`It is, therefore, an object of the invention to provide
`a continuous process for the dehydration of aqueous
`solids in a fluidizing oil medium containing a surfactant.
`It is another object of the present invention to pro-
`vide a continuous process for dehydrating aqueous
`solids in a fluidizing oil medium containing a surfactant
`wherein both the fluidizing oil and the surfactant are
`recovered and recycled.
`It is still another object of this invention to provide a
`continuous process for dehydrating aqueous solids in a
`fluidizing oil containing a surfactant wherein the fluidiz-
`ing oil is a light volatile oil.
`Yet another object of this invention is to provide a
`continuous process for dehydrating aqueous solids in a
`fluidizing oil containing a surfactant wherein the fluidiz-
`ing oil is a relatively heavy, non-volatile-type oil, some-
`times referred to herein as heavy oil.
`These and other objects and advantages of the pres-
`ent invention, including those represented by and deriv-
`ing from its apparatus aspects, will be apparent from the
`following detailed description and the accompanying
`drawings.
`
`(cid:0)H(cid:0)Y(cid:0)D(cid:0)R(cid:0)I(cid:0)T(cid:0)E(cid:0) (cid:0)E(cid:0)X(cid:0)H(cid:0)I(cid:0)B(cid:0)I(cid:0)T(cid:0) (cid:0)1(cid:0)0(cid:0)0(cid:0)6
`

`
`3
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`4,702,798
`
`FIG. 1 is a flow diagram representing an apparatus of
`one embodiment of the invention wherein a heavy oil is‘
`used as a fluidizing oil, showing the separation, crystal-
`lization, and recycling of the surfactant;
`FIG. 2 is a flow diagram which illustrates an appara-
`tus of another embodiment of the invention wherein
`light oil is used as a fluidizing oil and the feed does not
`contain a natural oil;
`FIG. 3 is a flow diagram which illustrates an appara-
`tus of a further embodiment of the invention wherein
`light oil is used as a fluidizing oil and the feed contains
`a natural oil, showing the separation, crystallization,
`and recycling of the surfactant, and
`FIGS. 4, 5, and 6 are schematics derived from FIGS.
`1, 2, and 3, respectively, of specific examples showing
`amounts of material being treated and components of
`treatment, consistent with a steady flow condition oil-
`solids-surfactant material balance in each instance.
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`
`The dehydration process of this invention involves
`three concepts which have not been combined previ-
`ously for aqueous solids evaporation-dehydration. They
`are (1) use of a surfactant along with the fluidizing oil;
`(2) maintenance of the process as a continuous process,
`and (3) recovery of the surfactant and the fluidizing oil
`either separately or together and their recycling either
`separately or together back into the process for reuse.
`The process comprises mixing aqueous solids feed
`material, a fluidizing oil and a surfactant in a vessel
`designated a fluidizing tank to obtain a mixture which
`will remain fluid and pumpable after removal of essen-
`tially its entire water content, and thereafter subjecting
`the resultant mixture of solids, water, surfactant and oil
`to a dehydration step or steps by heat evaporation
`whereby substantially all of the water is evaporated and
`subsequently recovered. Following dehydration,
`the
`fluidizing oil is separated from the solids.
`In the case where the fluidizing oil is a light oil, that
`is, a low viscosity, relatively volatile oil, and the solids
`to be treated contain or are accompanied by a natural
`oil themselves, that oil being for the most part a rela-
`tively heavy, non-volatile oil, the solids are washed in a
`centrifuge with recycled light oil. All of the oil carrying
`at least some surfactant is removed to a separating de-
`vice, e.g., a crystallizer, where the surfactant may be
`crystallized out and separated by centrifugation, filtra-
`tion or other suitable technique. The crystallized surfac-
`tant may be recycled to the fluidizing tank while the
`light oil containing natural oil is charged to a stripper
`for the recovery of the natural oil which is then dis-
`charged for external use or sale or blended with the
`solids from a deoiler.
`Where the material to be dried contains no natural
`oil, the solids are washed with light oil condensate from
`the evaporator and the light oil from that step is recy-
`cled along with the surfactant therein to the fluidizing
`tank.
`When the drying oil is a heavy oil, that is, a triglycer-
`ide or non-volatile-type oil, the solids after evaporation
`are centrifuged to separate the oil therefrom. The oil is
`divided into two segments, one of which is directly
`recycled to the fluidizing tank while the other is di-
`rected to a crystallizer for crystallizing out the surfac-
`tant which is subsequently separated from the oil by
`
`5
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`45
`
`50
`
`55
`
`65
`
`
`
`,15-.-3‘
`
`4
`centrifugation or filtration. The surfactant is then recy-
`cled to the fluidizing tank through a centrifuge oil hold-
`ing tank and the oil is charged to the centrifuge for
`washing the surfactant free from the centrifuged solids.
`As set forth above, the fluidizing oil can be either a
`light oil or a heavy oil. By light oil is meant oil having
`a boiling point in the range of about 250°—-600° F. which
`was fractionated, distilled, or compounded from petro-
`leum oil.
`The heavy oils can be triglyceride oils or petroleum
`oils. The triglyceride oils can be oils which are ex-
`tracted from animal origins such as beef fat, pork fat,
`chicken fat, fish oil, etc. They can also be oils which are
`extracted from vegetable origins such as soybean oil,
`cottonseed oil, peanut oil, coconut oil, etc. By petro-
`leum oil is meant oil having essentially no fraction vola-
`tile under the conditions of temperature and pressure of
`the dehydration process of this invention.
`The materials to be treated by the process of this
`invention should contain solid particles generally no
`larger than about 2 inch. However, larger particles are
`acceptable provided that the clearance past the heat
`transfer surfaces be increased. Large particles may be
`ground to size or comminuted by existing techniques.
`The evaporative drying of a wetted material is most
`efficient when the particles are small, unifonn in size
`and evenly dispersed in the circulating fluidizing oil
`medium. In the ideal mixture, the particles are reformed
`and become suspendible again after the mixture is al-
`lowed to stand for a period of time without agitation by
`merely agitating again.
`When used with granular material such as corn or
`grain, the surfactant will prevent coagulation of the
`granules. When used with a mass of material such as
`sludge, the surfactant tends to produce a uniform parti-
`cle size while in the wet state oil. This uniformity of size
`is maintained throughout the entire operation to ulti-
`mately produce a finished product of uniform size.
`Varying the amount of the surfactant will result in
`smaller or larger particle sizes and, therefore, may be
`utilized as a tool in predetermining the particle size and
`consequently the oil content of the finished dry particle.
`Many of these surfactants are of food grade quality
`and may be used when the finished product is intended
`for human consumption or animal feed. The small
`amount of surfactant that is left on the dry product
`solids will tend to improve their reconstitutability when
`added to water, with other ingredients, to make a food
`ration. The surfactant may act also as an emulsifier for
`the water-oil-solids mixture to produce a more homoge-
`nous preparation. Further,
`it may increase the water
`binding properties of food products such as bread,
`cakes, purees, etc.
`Specific characteristics of surfactants used for the
`dispersion of water wet solids in an oil are:
`(1) Solubility in the oil phase;
`(2) Hydrophilic-Lipophilic Balance number of 3-17,
`preferably 9-11;
`(3) Resistance to decomposition at the process operat-
`ing conditions of temperature and pressure;
`(4) Federal Food and Drug Administration accep-
`tance when the solids dried in a process such as the
`Carver-Greenfield Process (see U.S. Pat. Nos. Re.
`26,317, 3,950,230, and 4,270,974, for examples) are in-
`tended for human or animal ingestion; and
`(S) Negligible volatility at the process operating con-
`ditions of temperature and pressure.
`
`(cid:0)H(cid:0)Y(cid:0)D(cid:0)R(cid:0)I(cid:0)T(cid:0)E(cid:0) (cid:0)E(cid:0)X(cid:0)H(cid:0)I(cid:0)B(cid:0)I(cid:0)T(cid:0) (cid:0)1(cid:0)0(cid:0)0(cid:0)6
`

`
`5
`Preferably the surfactants are used in amounts of
`from about 0.05 to 10.0% by weight of the fluidizing oil
`and are usually non-ionic. They may be part of the class
`of compounds such as monoglycerides and diglycerides
`sold under the tradenames ARLACEL by ICI of the
`United States, Inc., DUR-EM by Durkee Industrial
`Foods of Ohio, and EMEREST by Emery Industries,
`Inc. of South Carolina; polyoxyethylene sorbitan fatty
`acid esters sold under the tradename TWEEN by ICI of
`the United States, Inc., DURFAX by Durkee Industrial
`Foods of Ohio, and EMSORB by Emery Industries,
`Inc. of South Carolina; polyoxyethylene sorbitol esters
`sold under the tradename ATLOX by ICI of the United
`States, Inc.; polyglycerol esters of fatty acids sold under
`the tradename SANTONE by Durkee Industrial Foods
`of Ohio; polyoxyethylene triglycerides of the 400 series
`sold by ICI of the United States, Inc.; sorbitan fatty acid
`esters sold under the tradename SPANS by ICI of the
`United States, Inc. and EMSORB by Emery Industries,
`Inc.; sulfonated oils by Sulpho Corporation of New
`Jersey; and lecithin by Central Soya Inc. of Illinois.
`The HLB (Hydrophilic-Lipophilic Balance) number
`may be chosen for any one of the compounds listed
`above, or may be obtained by the mixing of two or more
`of those compounds to give the desired HLB number.
`A dispersion of water wet particles in hydrocarbon-
`type oil is more difficult to obtain than a dispersion of
`the same particles in a triglyceride-type oil. That is due
`to a number of reasons. One is that certain hydrocar-
`bon-type oils are somewhat hydrophobic, i.e., lacking in
`water soluble components, due to their chemical make-
`up and, therefore, lack the hydrophilicity necessary to
`disperse wetted particles effectively. In contrast, the
`chemical make-up of triglycerides includes hydrophilic
`components which assist in forming water-oil disper-
`sions. Another reason is the difference in specific grav-
`ity between the oil and the wetted solids phase. Hydro-
`‘ carbon oils usually have a specific gravity of about 0.75,
`while that of triglyceride oils is about 0.93. The water
`wet particles have a specific gravity of 1.0 or slightly
`greater and, while not buoyant in eitherkind of oil, will
`stay suspended longer in a triglyceride oil than in a
`hydrocarbon oil.
`The word “dispersion” or “suspension” has been used
`throughout this description instead of the word “emul-
`sion”. Surface active agents are also used to make emul-
`sions where the mixture in many’ cases becomes very
`thick and viscous. That condition is not desired in the
`present process. A condition in which the surface active
`agent causes particles to be easily suspendible without
`causing an increase in viscosity of the mixture is desired.
`The increase in pumping rate associated with the
`disclosed use of surfactants is evident from the follow-
`ing example:
`
`..
`
`EXAMPLE I
`
`Corn stillage was mixed with corn oil to be dried.
`When charged to the evaporator and placed under
`vacuum and heat, the pumping rate was 3.0 gpm. After
`the addition of a surfactant, the pumping rate rose to
`24.3 gpm. In this example, polyglycerols of oleic acid in
`an amount of 0.45% by weight of the fluidizing oil were
`used as the surfactant.
`A suspension of oil and water wet solids when prop-
`erly made with the use of surface active agents, as men-
`tioned above, pennits the oil phase to make contact
`with the metal surfaces of the heat exchanger, vapor
`chamber and piping. In that manner, there is no corro-
`
`4,702,798
`
`6
`sion of those metal parts when dehydrating an acidic
`material in an oil medium.
`Foam depression has been seen to occur when surface
`active agents are used in the drying of water wet solids
`in an oil medium. Due to the surfactant, the vapor is
`released more rapidly in larger bubbles and does not
`tend to accumulate to form a foam layer which can
`upset an evaporator system. Persistept foams are usually
`composed of a multitude of small bubbles that do not
`collapse easily so that the vapor contained within can be '
`released.
`The small bubble size is usually caused by the slow
`release of small quantities of water vapor. Those small
`bubbles have a high surface tension and do not collapse
`easily and, therefore, tend to accumulate to form a per-
`sistent foam layer. The use of a surfactant reduces the
`surface tension of each bubble causing it to collapse,
`thereby retarding the formation of any further foam.
`Referring now to the drawings in detail, aqueous feed
`enters the apparatus of FIG. 1 through input line 2 at
`the left, and is fed to fluidizing tank 4 for mixing with
`relatively heavy, non-volatile fluidizing oil and recy-
`cled surfactant supplied through line 6. Make up surfac-
`tant is added through line 1 as needed to replace that
`small quantity lost from the system largely on the dry
`solids product. Pump 10 moves the resulting mixture of
`oil, surfactant and aqueous feed from tank 4 through
`connecting line or conduit 12 and throttle valve 14 to
`the tube bundle or evaporating region of first stage 16 of
`a three-stage or triple effect evaporator. Each stage of
`the evaporator removes about one-third of the water
`from the aqueous feed mixture supplied at 16. At start-
`up, sufficient fluidizing oil containing recycled surfac-
`tant is added through line 6 to insure that, after evapora-
`tion of its water content, the system or mixture of feed
`and oil and/or fluid fats remains pumpable
`In first evaporator stage 16 about 5 of the water is
`boiled off at a reduced pressure of approximately 2
`inches Hg absolute, and the temperature of the partially
`dehydrated product in the sump or bottom of that stage
`is maintained at approximately 110° F. Heating vapor
`enters first evaporator stage 16 from second stage vapor
`chamber 19 through connecting line 20 at a temperature
`in the neighborhood of 145° F. Vapor is removed from
`first evaporator stage vapor chamber 17 via connecting
`line 22 which passes it into a condenser 24. There, cool-
`ing water condenses the vapor and the recovered water
`or condensate is discharged through line 26 to hot well
`28. A slurry of partially dehydrated feed in fluidizing oil
`and surfactant is removed continuously from the bot-
`tom of first evaporator stage 16 through line 30 and fed
`to the evaporating region of second evaporator stage
`18.
`In second evaporator stage 18 a procedure is fol-
`lowed similar to that in the first stage, except that the
`sump or product temperature is maintained in the neigh-
`borhood of 150° F. by vapor coming at approximately
`190” F. from vapor chamber 21 of the following stage
`through connecting line or conduit 32. About one-half
`of the water remaining in the fluidized feed is removed
`in the second stage. A further partially dehydrated feed,
`surfactant and oil slurry is withdrawn from the bottom
`of second evaporator stage 18 via connecting line 36,
`and charged to the evaporating region of the third evap-
`orator stage 34 in the manner used for slurry transfer
`between the first and second stages.
`In the third stage the product temperature is about
`250° F., maintained by steam supplied at about 300° F.
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`45
`
`50
`
`55
`
`60
`
`65
`
`(cid:0)H(cid:0)Y(cid:0)D(cid:0)R(cid:0)I(cid:0)T(cid:0)E(cid:0) (cid:0)E(cid:0)X(cid:0)H(cid:0)I(cid:0)B(cid:0)I(cid:0)T(cid:0) (cid:0)1(cid:0)0(cid:0)0(cid:0)6
`

`
`
`
`7
`by boiler-furnace 38 and transmitted through line 40.
`The substantially dehydrated slurry withdrawn from
`the bottom of third evaporator stage 34 through line 42
`contains approximately 0.075 to 0.45% water based on
`the entire slurry, the remainder being oil containing
`surfactant. That slurry is in a substantially anhydrous or
`dry condition.
`Level control in the several stages of the evaporator
`equipment is maintained by a level sensing element in
`the slurry sump or bottom of each stage which transmits
`signals to a throttle valve following the pump which
`supplies that stage. As shown, level sensing elements in
`the slurry sumps of first, second and third evaporator
`stages 16, 18, and 34 control pump discharge throttle
`valves in slurry feedlines 12, 30, and 36, respectively.
`The evaporator level‘ control system illustrated and
`described is of a conventional nature.
`The substantially dehydrated surfactant, oil and
`solids mixture maintained at an appropriate level in the
`sump of third evaporator stage 34 is withdrawn contin-
`uously therefrom through line 42 to centrifuge 44 hav-
`ing a screen bowl section, but prior to entering the
`centrifuge it is joined by a stream of heavy oil from filter
`press or expeller 56 recirculated through line 68. Within
`centrifuge 44 the initial effect of simple centrifugation
`throws off the bulk of the surfactant and heavy oil from
`the solids. The thrown off material flows from the cen-
`trifuge through line 50 to centrifuge oil tank 52 for
`recycling through oil and surfactant supply line 6 to
`fluidizing tank 4. Continuing through the centrifuge, the
`solids input
`thereto enters the screen bowl section
`thereof and is there washed by heavy oil returned from
`centrifuge 107 through line 114. That washing removes
`the residual surfactant from the solids, and a heavy oil
`flows from centrifuge 44 through line 101 to holding
`tank 102.
`Pump 103 withdraws mixed heavy oil and surfactant
`from tank 102, and delivers that material to an array of
`a crystallizers generally designated 104 comprising indi-
`vidually valved tanks 104A, —104B and 104C arranged in
`parallel and provided individually with indirect cooling
`means. Within the overall crystallizer arrangement the
`surfactant content of the incoming mixture of heavy oil
`and surfactant is crystallized out substantially continu-
`ously in what is a coordinated set of batch operations in
`the three tanks of the crystallizer apparatus.
`Exemplifying the crystallization operation suppose
`that the outlet valve of tank 104A is closed but the inlet
`valve of that tank is open and a heavy oil and surfactant
`mixture is flowing into the tank from tank 102. That step
`or operation is called the fill or charge step. Tank 104B
`has been filled previously and its inlet and outlet valves
`are each closed and its cooling means activated. Thus,
`while tank 104A is filling, tank 104B is quiescent and
`cooling to crystallize the surfactant component of its
`content fluid. That step or operation is called thehold
`step. Meanwhile tank 104C having been charged prior
`to tank 104B and held at the proper cooling temperature
`for the time required to effect crystallization has had its
`outlet valve opened and its heavy oil and crystallized
`surfactant content is flowing out therethrough. This is
`called the discharge step. Tank 104B would be the next
`to discharge while tank 104A holds and tank 104C fills;
`then tank 104A would discharge while tank 104C holds
`and tank 104B fills; then tank 104C would discharge
`while tank 104B holds and tank 104A fills, and so on
`repetitively.
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`4,702,798
`
`8
`As a result of the operation just described a steady
`stream of heavy oil with a crystalline surfactant content
`flows away from crystallizer 104 through line 105 in-
`cluding pump 106, and is delivered to centrifuge 107
`within and by which the crystallized surfactant is sepa-
`rated from the heavy oil. The heavy oil, essentially free
`of surfactant, leaves centrifuge 107 through line 114 and
`flows to holding tank 108 from which it is withdrawn
`by pump 109 in line 114 and recycled to centrifuge 44
`for a washing purpose described already. If there be an
`excess of process oil so far as fluidizing needs are con-
`cerned, possibly because the aqueous feed material en-
`tering the system through line 2 has heavy oil associated
`with it, oil may become available as a net product of the
`process and be tapped off from line 114 as shown.
`The crystallized surfactant output from centrifuge
`107 leaves through line 112 and flows to remelt tank 110
`equipped with heating means and an agitator 113 to
`accelerate the melting process. From tank 110 the essen-
`tially oil-free surfactant continues to flow through line
`112, and by pump 111 therein is delivered to centrifuge
`oil tank 52 for mixing with heavy oil therein. From tank
`52 the surfactant is recycled along with the oil thr