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Патент USA US3039117

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June 12, 1962
3,039,107
P. BRADFORD
AGGLOMERATION OF‘ ' SPRAY-DRIED MATERIALS
Filed March 10, 1961
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'
IN VEN TOR.
United States Patent 0
1
,.
1C6
3,039,107
Patented June 12, 1962
2
materials are held at a high temperature for an extendec‘
3,039,107
AGGLOMERATION 0F SPRAY-DRIED
MATERIALS
-
Purdy Bradford, Palos Park, 111., assignor to Swift &
Company, Chicago, Ill., a corporation of Illinois
Filed Mar. 10, 1961, Ser. No. 94,943
10 Claims. (Cl. 159-48)
period of time. The substantially moisture-free particles
are then conducted in the gaseous suspending stream intc
a zone having a tapering conical section to a constrictec
area where the stream of particles contacts c'o-currentlj
sprayed droplets of additional liquid. The additions
liquid may be asubstance other than the ?rst mentionec
solution. For instance, such additional liquid may b:
water. However, a quantity of the heat-sensitive materia?
This invention relates generally to a method for prepar
ing heat sensitive materials in a dry form, and more par 10 in the form of a solution or suspension may be advan
tageously used for this purpose.
.
ticularly, to a method whereby heat-sensitive materials in
Because of the high velocity of the gaseous stream con
a dry particulate form, well adapted to reconstitution with
taining dried particles and the relatively low velocity 01
a liquid, may be prepared.
the droplets, the dry particles tend to impinge upon and
This application is a continuation-in-part of my prior
co-pending application Serial No. 696,281, now aban 15 collect on the surface of the droplets of additional liquid.
forming large clusters or agglomerates of the product
doned, ?led November 13, 1957.
_
The agglomerated particles are conveyed in the gaseous
Spray-drying procedures,‘such as are disclosed in co
stream into an area of expanding cross section, where ad.
pending application Serial No. 572,575, ?led March 19,
ditional evaporation takes place. The dried agglomerated
1956, by E. W. Comings et al., are particularly well
adapted to the drying of heat-sensitive materials because 20 product is then conveyed to a liquid-gas ‘separator for
collection of the‘ product.
.
the danger of heat damage to the product in spray drying
It is fundamental to my invention that each of the
is small. In accordance with such spray-drying processes,
various streams of 'gas and liquid are directed in sub
stantially the same rectilinear direction. Thus, the term
and brought into contact with a drying gas in-a highly
turbulent action. Atomization produces an extremely 25 “co-current” used herein is intended to mean only rec
tilinear concurrency wherein there is no substantial addi
small particle size of the material being dried, thus in
tional component of motion in a different direction, such
suring that a large area of the materialbeing dried is ex
as would be experienced in vortical flow. However, it is
posed to the drying gases. This small particle size, cou
intended that the term does embrace the movement of an
pled with the high temperature and high velocity of the
expanding spray as it leaves a nozzle which is aimed con
gas stream in the dryer, provides almost instantaneous dry
the material to be dried is converted to an atomized form v
ing of the particles. A particular advantage in this type
currently with the other ?ow, and ?ow which is being
of drying lies in the very short residence time of the
medium in the area of high temperature necessary to pro
duce a dried product. Also, recirculation of dried product
tures is avoided.
compressed or expanded due to variations in the cross
sectional area, of the ilow passageway, in a plane perpen
dicular to the direction of ?ow.
A further understanding of the invention can be had by
reference to the detailed description taken in conjunction
Although extremely small particle size is necessary in
spray-drying procedures, this small particle size represents
with the accompanying drawing.
The‘ single FIGURE is a schematic drawing showing
and repeated exposure of the particles to high tempera
one embodiment of equipment well suited to the practice
a disadvantage in the subsequent collection of the dried ‘
_
product, and also presents a solubility problem where the 40 of this invention.
In the drawing a feed tank 10, equipped with a mechani
dried materials are intended for later reconstitution with
cal stirrer if desired, comprises a reservoir of the solu
water or some other liquid. Because of the small particle
tion or suspension from which the dried material is to be
size, spray-dried materials are not readily soluble in
liquids because of the entrapped air surrounding individual
particles.
vIt is therefore an object of this invention to provide. a
method for drying heat-sensitive materials in a form hav
produced. The liquid is conductedjto the drying area
from the feed tank by means of a liquid pump 11 through
a conduit 12 to an injector 13. A primary air blower l4
capable of delivering air at the rate vof about 11,000
c.f.m. moves air through a heater such as a gas burner or
ing physical characteristics well adapted to easy collection
electric heater generally 16 through conduit 17 to a nozzle
of the material.
A further object ‘of the invention is the provision of a 50 inlet 18 in a nozzle 19 which surrounds the injector. The
temperature of the gas leaving the primary air heater may
method whereby heat-sensitive materials may be dried and
' be regulated in the range 4-()()—800° F.
agglomerated to produce dried particles having an im
Secondary air is provided by means of a secondary air
proved adaptability to reconstitution with liquids.
blower 21, and the air is passed through conduit 22 into a
Additional objects, it not speci?cally set forth herein,
secondary air heater 23. The secondary air heater may be
will be readily apparent from the detailed description
heated by means of steam from a source, not shown,
which follows.
7
passing through steam inlet 24 and outlet 25. From the
In accordance with the method of this invention, a solu
secondary air heater the air is conducted through conduit
tion or suspension of the heat-sensitive material is atom
26 to a secondary air inlet 27 on a tubular dryer gen
ized to produce a minimum particle size of the liquid and
entrained solids. Atomization is achieved by discharging 60 erally 30. The output end of the tubular dryer housing is
the solution or suspension into a co-current heated stream
of drying gas in a zone of substantial turbulence, where
connected to a tapering conical section 43, forming an
dispersion and volatilization of the liquid medium take
at 32. Connected to said tapering conical section is an
injection zone the cross section of which is at a minimum
additional conical section 33, the walls of which gradually
place. Additional co-current air at an elevated tempera
ture and high velocity from a secondary air source en— 65 diverge to form a cross-sectional area of increasing size.
Conical section 33 is connected to the input end of a gas
velops the atomized particles and serves to dilute the
solid separator such as a cyclone collector 34, equipped
with appropriate vents as at 35 and a take-off valve 36.
The dried particulate material is collected in a container
the primary air stream, thus avoiding the deleterious ef 70 37.
A second source of the solution or suspension is con
fects which the higher temperature of the primary air
veyed through conduit 40 to a secondary liquid pump
stream would have on heat-sensitive materials if these
volatilized material, and aid in the removal of this
volatilized material from the system. This secondary air
source also prevents recycling of the dried product through
3,039,107
3
4
which conveys the liquid through a conduct 42 to
Air containing moisture is discharged through vents, and
throat 32 of the Venturi structure. A nozzle 31 is
the dried particles are removed at the base of the col~
lector.
'ided for distribution of the liquid particles. The
ndary liquidstream may be introduced into the drier
flow rate in the range of 10-100 gallons per hour.
or installations not utilizing the solution of heat sensi
material as the additional liquid for agglomer‘ating
roses, it will be obvious that the conduit 40 will not
onnected to the feed tank 10. Instead the secondary
Id pump 41 is connected by an appropriate conduit
. source (not shown) of such additional liquid as
be required; for example the pump 41 may be con
ed to a tank of water.
Under the latter circum
:e the feed rate of the secondary liquid does not di?er
tantially from that set forth for a second quantity
‘1e spray-dried solution.
i. operation, the liquid solution or suspension is pumped
l the feed tank to the injector under a pressure rang
The following example, which is included herewith for
purposes of illustration, demonstrates the drying and ag
glomeration of milk particles in a system such as is dis
closed herein, and also shows the effect of the air ve
locity at the throat of the Venturi agglomerator on the
size of the drops produced by the agglomeration spray.
Example I
Whole milk was atomized by breaking the liquid up
into a ?ne spray or fog into a primary air stream having
an initial velocity of 1000 feet per second. and a total
volume, when mixed with the secondary air stream, of
12,000 cubic feet per gallon of milk atomized at the en
trance of the dryer. An agglomerating spray of whole
milk was introduced at varying velocities at the throat
from about 0 to 60 p.s.i. Atomizing air from the
the Venturi structure, and the resulting drop size of the
my air source envelops the liquid particles as they 20 of
agglomerating
spray was noted. The percent agglomerat
nate from the injector. The primary air has a ve
ing spray based on the weight of the whole milk intro
y of 600 to 1300 feet per second and a temperature
duced into the dryer was determined. The following
bout 750° F. at the nozzle exit. As the primary air
table is a correlation between velocity of the agglomerat
the liquid meet, the latter is dispersed very ?nely to
ing spray and the amount of agglomerating spray ncccs<
1 droplets of below about 40 microns mean diameter
ng dissolved or entrained solids. The heated, high ve~
y air suspension of the droplets is conducted into the
I of the tubular dryer. The secondary air stream,
1h moves at a lower velocity than the primary air
rm and is at a lower temperature, surrounds the pri 30
sary to produce a given drop size:
Agglomcratlng
Drop Size of
Venturi 'l‘hrout Agglomerating
Velocity, it.
per second
Spray (Alter
impingement),
Pei-cont .-\ g
glomeration
Spray [to
quired
microns
,/ air jet, preventing recycling of the dried product
picking up the vapor evaporated from the feed. The
ndary air stream is forced into the dryer at the rate
300
400
52.3
38.4
2.33
2.08
bout 60,000 c.f.m. and is maintained at a tempera
500
30.2
1.85
600
25.0
2. 65
of about 70-160" F. The turbulence and high tem 35
ture of the primary air stream rapidly dries the small
.eles while the secondary air stream serves to dilute
Further work indicates that as much as 5% agglomerat
moisture evaporated from the feed and to carry the
ing spray could be employed to produce dried particles
arsed particles. The high initial temperature of the
of a satisfactory size and constitution. As the stream
iary air stream is rapidly reduced by evaporation of 40 carrying dried particles enters the throat of the Venturi
r from the feed. The rate of evaporation and then
structure, the velocity of the stream increases, and at
‘ate of temperature decrease is a function of the pri
this time the stream intersects and impinges upon the
,/ air velocity at the nozzle.
liquid curtain emanating from the secondary liquid source.
to pressure of the commingled primary and secondary
It can be readily appreciated that a method is pro
treams provides the impetus for the discharge of this
m into the gradually decreasing cross-sectional area
1c discharge end of the dryer and into the throat of
Venturi structure. At this point, the dried particles,
ng a mean diameter in the range of about 5 microns,
dc with and impinge upon droplets of the ?uid medium
hating from a nozzle or spray located in the throat.
velocity of the stream of dried particles passing into
Venturi throat ranges from about 200-800 feet per
nd, and preferably 300-600 feet per second, while
temperature is about 120-180” F. Because of the
differential velocity between the liquid droplets and
'apidly moving gaseous stream of dried particles, the
d is broken down into droplets having a mean diame
>f from 20-100 microns. The dried particles im
vided herein whereby highly heat-sensitive materials may
be treated in a complete drying and agglomeration pro
cedure with no deterioration of the material.v Typical
materials which may be dried and agglomerated in ac
cordance with the method of this invention are such prod~
ucts as milk, egg whites, egg yolks,,whole eggs, orange
juice, coffee, enzyme extracts and heat-sensitive biological
materials.
1
Obviously, many variations and modi?cations of the
invention as hereinbefore set forth may be made without
departing from the spirit and scope thereof, and therefore
only such limitations should be imposed as are indicated
in the appended claims.
'
I claim:
1. A method for producing a dried product in particu
e the ?uid droplets, and an agglomeration or building 60 late form of a size and density adapted to improved rc
if the particle size of the droplets to from about
constitution with a liquid which comprises: dispersing a
1000 microns average mean diameter is effected.
product contained in a liquid carrier co-currently into a
irther evaporation of liquid is realized as the ag
heated high velocity primary air stream, said primary air
lerated particles are conveyed by means of the gas
stream being of sutlicicnt mass and velocity to formdrop
vm through the gradually expanding portion of the
lets of said product and carrier having a mean diameter
.uri structure. The temperature of the air stream
of below about 40 microns, said primary air stream also
1g this ?nal drying is reduced to about 100-160“ F.,
containing su?icient heat to .form dry particles from all
exact temperature depending, of course, on the size
of said droplets; co-currently delivering a secondary air
re dryer, the velocity of the drying air, and the resi
stream of relatively cooler air surrounding said primary
e time of the agglomerated particles in the dryer. 70 air stream to absorb moisture evaporated from the drop
adjustment of these conditions is within the ability
lets and to dilute said primary air after said particles are
ne skilled in the art. The dried agglomerated parti
formed, said sccondary air stream being of su?icient mass
are collected in a cyclone collector, a bag house or
and velocity to prevent said particles from being recycled
r suitable gas-solids separator. In the embodiment
to the hot primary air stream; converging the total flow
rated in the drawing, a cyclone collector is shown. 75 of said primary and secondary air streams and said par
3,039,107
5
6
" tieles carried thereby; and injecting into said converging
panding said total flow so as to promote further drying
total ?ow a spray of an additional liquid directed sub
of said larger particles.
stantially co-currently with said ?ow whereby said dry
particles will agglomerate with droplets of said liquid
8. The method of claim 6, wherein the injected spray
comprises up to about 5 percent of the quantity of said
spray to form larger relatively dry particles.
food product in said liquid carrier dispersed in said pri
2. The method of claim 1 wherein the larger, agglom
erated particles are subjected to further drying by ex
panding said total ?ow so as to promote further drying
mary air stream.
9. A method for producing a dried mill; product in
particulate form of a size and density adapted to im
of said larger particles.
proved reconstitution with water which comprises: dis
3. The method of claim 1 wherein the injected spray 10 persing liquid milk co—currently into a heated ‘high veloc
comprises up to about 5 percent of the quantity of said
ity primary air stream, said primary air stream being of
sufficient mass and velocity to form droplets of said milk
product in said liquid carrier dispersed in said primary air
stream.
.
having a mean diameter of about below 40 microns. said
primary air stream also containing su?icient heat to form
4. The method of claim 1 wherein the spray of an
additional liquid consists of water.
15 dry milk particles from all of said droplets; co-currently
delivering a secondary air stream to absorb moisture
5. The method of claim 4 wherein the product dried is
evaporated from the droplets and to dilute said primary
a food material.
f
6. A. method for producing a dried food product in
air after said particles are formed, said secondary air
particulate form of a size and density adapted to im~
stream being of sut‘?cient mass and velocity to prevent
proved reconstitution with a liquid which comprises: dis 20 said particles from being recycled to the hot primary air
persing a food product contained in a liquid carrier co
stream; converging the total ?ow of said primary and
secondary air streams and said dried'milk particles car
currently into a heated high velocity primary air stream,
ried thereby; and injecting into said converging total flow
said primary air stream being of su?‘icient mass and
velocity to form droplets of said food product and car
a substantially co-current spray of relatively coarse drop
lets of said liquid milk, said injected spray constituting
rier having a mean diameter of below about 40 microns,
up to about 5 percent by weight of the total liquid milk
said primary air stream also containing su?icient heat to
form dry particles from all of said'droplets; co-currently
processed, whereby said dried particles will agglomerate
delivering a secondary air stream of relatively cooler air
with said relatively coarse droplets to form larger rela—
tively dry milk particles.
surrounding said primary air stream to absorb moisture‘
evaporated from the droplets and to dilute said primary 30 10. The method of claim ,9, wherein the. larger agglom
erated particles are subjected to further drying by expand
air after said particles are formed, said secondary air
ing the total ?ow of said air streams beyond the point at
stream being of su?icient mass and velocity to prevent
said particles from being recycled to the hot primary air
which said coarse spray is injected.
stream; converging the total ?ow of said primary and
secondary air streams and said particles carried thereby; 35
and injecting into said converging total ?ow a spray of
an additional quantity of said food product in said liquid
carrier directed substantially co-currently with said ?ow
whereby said dry particles will agglomerate with droplets
of said liquid spray to form larger relatively dry par 40
ticles.
t
7. The method of claim 6, wherein the larger agglom
erated particles are subjected to further drying by ex
References Cited in the ?le of this patent
UNITED STATES PATENTS
1,405,756
1,964,858
2,460,546
2,561,394
2,576,264
Carr ________________ __ Feb. 7,
Peebles ______________ ___ July 3,
Stephanoff ___________ __ Feb. 1,
Marshall ____________ __ July 24,
Coulter '_ _________ __.__ Nov. 27,
.1922
1934
1949
1951
1951
2,835,597
Barzelay __-_ _________ __ May 20, 1958
UNITED STATES PATENT OFFICE
CERTIFICATE OF CORRECTION
Patent. No. 3,039,107
June 125 1962
Purdy Bradiord
It is hereby certified that error appears in the above numbered pat
ent requiring correction and that the said Letters Paterit should read as
corrected below.
Column 6, line 13, for "about below’! read —- below about,
Signed and sealed this 9th day of October 1962.
(SEAL)
Attest:
ERNEST w. SWIDER
Attesting Officer
DAVID L. LADD
Commissioner of Patents
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