US2657797A

US2657797A - Process of cooling spray dried detergents

Info

Publication number: US2657797A
Application number: US22808A
Authority: US
Inventors: Lowell A Ledgett; Charles W Deane; John J Mahoney
Original assignee: Colgate Palmolive Co
Current assignee: Colgate Palmolive Co
Priority date: 1948-04-23
Filing date: 1948-04-23
Publication date: 1953-11-03
Anticipated expiration: 1970-11-03
Also published as: GB661599A

Description

3, 1953 L. A. LEDGETT ET AL 2,657,797

PROCESS OF COOLING SPRAY DRIED DETERGENTS Filed April 23, 1948 2 Sheets-Sheet 1 J LOWELL n. LEDGETT CHARLES \MDEHNE JOHN \J- MAHONEY v@#mw w 3 L. AJLEDGETT ET AL I 2,657,797

PROCESS OF COOLING SPRAY DRIED DETERGENTS Filed April 25, 1948 I 2 Sheets-Sheet 2 amend om 4 LOWELL ALEDGETT q i- CHARLES w. DEANE JOHN J.MAHONEY Patented Nov. 3; 1953 PROCESS OF cooL N SPRAY DRIED.

nu'raacuu'rs Lowell A. Ledgett, Ridgewood, and Charles W. De n S mmit, N. J., and J hn J- Mulr ney, New York, N, Y,, assignors to Colgate,-Palm- JerseyCity, N. L, acorolive-Pe'et Company,

poration of Delaware ApplicationApril 23, 194 8, Serial No. 22,808

(01. aliens-i1) .5 Claims. 1

The present invention relates to an ap a for and a method of cooling spray dried organic detergents.

Spray dried organic detergents are prepar d by introducing an aqueous solution of the detersent into the upper end or a spray tower through an atomizing device which breaks the liquid up intodroplets. During their fall through the tower these droplets are exposed to heated air or other gas, which dries them into solid particles. The evaporation of the moisture prevents the particles from becoming heated to the temperature of the drying gas, but in normal operation soap particles leave the tower at a temperature within the range of about 170 to 195 F. while synthetic detergent particles leave .at about :200 to 220 F.

Detergent particles would cake into large lumps if they were packaged at such an elevated temperature, The present invention has for an object the cooling of these hot detergent particles to a lower temperature at which the tendency to cake is minimized or overcome. The in vention also contemplates transporting and/or classifying the particles simultaneously with the cooling thereof. Other objects and advantages of the invention will become apparent from the followin detailed description taken in conjunction with the drawings in which:

Fig. 1 is a schematic elevational view of apparatus embodying the present invention;

Fig. 2 is a plan view with parts broken away to reveal structural details of the classifying device shown in Fig. 1;

Fig. 3 is a sectional view along the line 3--3 of Fig. 2 looking in the direction of the arrows and; v

Fig. 4 is a fragmentary elevational view of the classifying device.

Referring now more particularly to Fig. 1, the apparatus comprises a tower l of the counter current type, having a plurality of spray nozzles 2 in the upper portion thereof to which theliquid detergent material is pumped through line 3 by pump 4. The bottom of the tower is in the'form of a cone 5 leading to an outlet pipe 6. The outlet pipe 6 communicates with a pneumatic conveyor duct 1 having an air inlet 8 andleading to a cyclone separator 9, where the product is separated from the air stream. A concurrent type tower may also be used, in which case tower air rather than atmospheric air is used in duct 1. The product leaves the separator through a product outlet pipe In. The air stream is withdrawn through exhaust line H and bag house l2 by means of a .fan 13 which places the entiresystem from the ,air inlet -8 through the has house .12 under a negative pressure.

The product leaving the cycl e separator 9 through product outlet p pe l0 flows through star valve lea into asurs hopp r l4 ha ins ii feedlec I5 c mmunicati g with a pres ure ai duct 56 which loads to the bo tomof a co lin column H. The column IT has a substantially lar er iameter than the air duct J out duct 18 l ads from t e top of the c ling c lumn to a cy lone separator .19 which has a product outlet line 20 provided with a star valve 29 and an air exhaust line =21, which .commlln With the exhaust line H,

The invention also contemplates the introdu tion of the spray dried product from the spray tower directly into the pr ssure air duct 16. which eliminates the air conveyor 1 and associated parts 9. Ill, l4 and I5. In such a system the tower cone to discharges the product throush an outlet pipe to having an air lock, e. 3., a star valve 612., for transferring the product from the lower pressure zone of the tower into the higher pressure zone of theair duct 46.

Air under positive pressure is supplied to the duct 15,-for example, by means of a positive displacement blower, or compressor or turbo-com.- pressor '22. This air may be conditioned .so as to facilitate the coolin of the product. The conditioning system illustrated in the drawing oom-v prises a water .23 which is adapted to remove the heat of compression, an evaporator 24 and a mist separator 25. Liquid refrigerant is supplied to the evaporator 24 through a liquid refrigerant line 26 and the refrigerant after evaporation in the evaporator 24 is withdrawn through a vapor line 2?! to aoompressor 28 drivon by a motor 23. The compressed vapor flows through a condenser-34 which is provided with a water inlet pipe 32 and a water outlet pipe 13.

The cooled or partially cooled product from the separator "is introduced into a classifier 34. The invention also contemplates introduction of partially cooled product from the separattn- 8 directly into classifier 3!. Referring now more particularly to figs. 2, 3 and 4, it will be seen h h slassifl m s s a bed 35 o w ch a framework is mounted i bear n s .31 at one nd and in a eccentric -3 e Psa mo i at the other end which is at a higher level. o n ed e th irem we t 36 .5 a snowmen 4.0 .ea about? m sh ne bot m screen a st about 450 mes B low he bottemse e n s a .gi-ust vchut 4,2 and above the top screen u op m ll 53. thus enclosing the within a The chamber within the classifier communicates withthe exhaust .svsiqa 1i throne-ha plu- 3 rality of suction ducts 44 in the top wall 43, a manifold 45 and a suction line 46.

Air may be introduced into the space between the screens through a conditioning air system comprising an air intake 41 in which are mounted evaporators 48. Liquid refrigerant flows into evaporators 48 through line 49 and the evaporated refrigerant returns through vapor line 50. The air stream, after passing over the evaporators 48, is divided and flows through two branch lines which lead to manifolds 52 on each side of the classifier. A plurality ofair ducts 53 run from each manifold through the respec tive side walls of the classifier into the space between the screens 4| and 4i as shown in Fig. 3. The classifier is provided with a tailings outlet 54 for the oversized particles, a product outlet 55 for the particles within the desired size range and a fines outlet 56 for the particles which are of smaller size than desired. All of the ducts which connect to the classifier are provided with flexible connectors 51 to prevent the vibration of the framework 36 from traveling into the fixed lines.

The fines collected in the bag house l2 are returned for reprocessing by means of a conveyor belt 58. A similar belt (not shown) may be provided at the fines outlet 55 and the tailings outlet 54. The product discharged from line 55 may go directly to packaging apparatus.

In the operation of the apparatus, the hot spray dried product which is discharged from the tower I may be partially cooled by contact with ambient air in the air conveyor system using an induced draft fan to produce a rapidly moving stream of air which will entrain and convey the particles by reason of the velocity alone. A satisfactory velocity for this purpose lies within the range of about to 70 feet per second. The period of contact between the air and the hot particles is limited to a few seconds by the useful length of the duct employed, but within that time the particles may be cooled to 125 F., or somewhat lower depending upon the temperature and humidity of the ambient air. A major disadvantage of an air conveying system such as that illustrated in I, 8, 9, l0 and ll, 12 and I3 of Fig. 1 is that if the product is cooled therein to a safe packaging temperature it becomes sufficiently brittle to break up and produce excessive amounts of fines under the relatively high impact to which it is necessarily subjected in going around bends in the system and in the separator 9. This disadvantage is avoided in the practice of the present invention by only partially cooling with conveying air, or preferably avoiding its use entirely, and cooling to final packaging temperature or thereabouts in a positive air delivery low velocity system, e. g., a system embodying the principles of that shown at I6, l1, l8, I9, 20, 22, 23, 24 and 25 of Fig. 1

The system utilizing the column or tower 11 has great merit even where cooling is merely an incident to conveying of frangible particles. In this system the air stream has sufficient area in cross section that the rate of air flow, as computed on the empty tower or duct section, is very materially less than is operable for an airconveying system. Instead of carrying the detergent particles along by entrainment in an air stream moving at a substantially higher speed than the highest terminal velocity (i. e., the maximum velocity attained by a freely falling particles in still air) of the particles, the air fluidizes the mass and apparently either operates like an air lift pump or operates by virtue of pressure differentials sufficient to cause low velocity flow of the fluidized mass or perhaps functions partially in both ways. The lower velocity of the air stream has the advantage not only of reducing the breakage of the particles but also of prolonging the time of contact so that the cooling effect of the air is utilized more efficiently. Satisfactory results have been obtained with a system such as that illustrated in Fig. l, where the air velocity in the cooling column I! falls within the range of about 3 to 16 feet per second. Lower and higher velocities may be used if desired, a practical minimum being about 0.25 feet per second, and the maximum being less than that at which a substantial proportion of the particles become air conveyed. A safe practical maximum is about 25 feet per second.

It is essential to the satisfactory operation of the lower velocity cooling system that means be provided which will build up a steep pressure gradient behind the mass of particles being treated. As the velocity is lower than that used in air conveying, particles may deposit in various portions of the system in such quantities that air pressure far in excess of that obtainable by suction alone may be required to start the particles moving again. In the positive air delivery system utilizing a positive displacement blower, for example, the necessary pressure develops automatically as the blower continues to operate.

The compression of the air by a positive displacement blower results in a temperature rise due to the heat of compression. This heat is readily removed by a water cooled heat exchanger. When this compressed air expands again to atmospheric or subatmospheric pressure, it exerts a cooling effect upon the particles with which it is in contact in the tower [1. Under certain atmospheric conditions this may be sufficient conditioning for the treating air, but under conditions of high temperature and high humidity it is often necessary to supply additional artificial cooling which also dehumidifies that air. The evaporator 24 is provided for this purpose and it is preferred to operate with the temperature of the heat exchange surface just above freezing so that the coils do not have to be defrosted. As the air becomes saturated with moisture upon cooling to lower temperatures, the excess precipitates as droplets on the cooling coils from which it can be readily drawn on. Any droplets which are entrained in the air stream can be removed by any convenient means such as the mist separator 25.

Additional cooling may be accomplished in the classifier 34 using either ambient or conditioned air, depending upon atmospheric conditions. In the process of the present invention in which the particles being classified are passed generally downward through the classifier screens, the cooling air is introduced transversely into the stream of falling particles above the bottom screen and turns upward through the upper screen into the exhaust system. The rate of flow of the cooling air is preferably such that most of the fines do not become air borne but pass through the lower screens into the dust chute 42.

The following examples will illustrate the flexibility and mode of operation of the present invention.

Example I Spray dried soap is produced in tower l at a rate of about 12,200 pounds per hour from which it is discharged at a temperature of about 208 F.

It is picked up in a stream of ambient air at about 69 F. (wet bulb 66 F.) flowing through the air conveyor at about 73 feet per second. The soap which is separated from the air stream in cyclone separator 9 flows through parts I0, lila, 14 and I5 into the duct I6 and cooling tower I! at a temperature of about 116 F. Here it comes in contact with refrigerated air at a temperature of about 54 and a relative humidity of 94%. This air has a velocity in the column of about 5 feet per second (computed on the basis of an empty tower). The soap leaves tower IT at a temperature of about 91 F. and with a loss of about 0.6% moisture. It passes through the classifier where tailings and fines are removed without blowing additional air into contact with the soap. The packaged product has no tendency to cake during storage.

Example II Spray dried soap is passed at a rate of about 13,000 pOunds per hour and at a temperature of about 122 F. into the cooling column. The ambient air, which has a temperature of 95 F. and a relative humidity of 60%, is cooled to about 74 F. for introduction into the cooling column and the classifier. The soap is cooled to about 105 F. in the cooling column by blowing the cooled air through it at a velocity of about 15 feet per second. Further cooling to about 90 F. is effected in the classifier by blowing the cooled air into the space between the screens at a rate of about 70 cubic feet per second. The packaged product remains free flowing on storage.

Although the invention has been described and illustrated in connection with specific illustrations of apparatus and process conditions, modifications and variations within the scope of the appended claims are contemplated.

What is claimed is:

1. The process which comprises introducing hot spray-dried organic detergent particles through an air look into a cooling system and feeding them to the bottom of a mass of such particles, passing cooling air under positive delivery upwardly through said mass of particles in said system at a velocity less than feet per second, removing cooled detergent particles from the upper portion of said mass, conveying said removed particles to an air separating device, and separating said particles from said air in said separating device.

2. The process of cooling spray-dried organic detergent particles which comprises discharging the particles from a spray tower into a current of ambient air moving at avelocity of about feet to 70 feet per second in an upward direction, separating the particles from the air after a few seconds contact, introducing the particles through an air lock into a cooling system and feeding them to the bottom of a mass of such particles, passing cooling air under positive delivery upwardly through said mass of particles in said system at a velocity less than 25 feet per second, removing cooled detergent particles from the upper portion of said mass, conveying said removed particles to an air separating device, and separating said particles from said air in said separating device.

3. The process which comprises introducing spray dried organic detergent particles from a spray tower through an air lock into a cooling system and feeding them to the bottom of a mass of such particles, passing air under positive delivery upwardly through said mass of particles in said system at a velocity less than 25 feet per second, removing detergent particles from the upper portion of said mass, conveying said removed particles to an air separating device, and separating said particles from said air in said separating device.

4. The process which comprises introducing spray dried detergent particles at a temperature too high for packaging through an air look into a cooling system, partially cooling said spray dried detergent particles by blowing cooling air under positive delivery upwardly through a mass of said particles in said system at a velocity less than 25 feet per second, continuously adding hot particles at the bottom of said mass, continuously removing partially cooled particles from the top of said mass, and classifying the removed particles into product, tailings and fines while blowing additional cooling air transversely into and upwardly through a stream of falling particles to complete cooling them to the desired temperature.

5. The process of cooling spray dried organic detergent particles which comprises introducing particles discharged from a spray tower and while still at a temperature too high for packaging into a current of ambient air moving at a velocity of about 30 feet to 70 feet per second in an upward direction, separating the particles from the air after a few seconds contact, passing the particles downwardly through a plurality of sloping classifying screens, passing streams of cooling air from opposite sides transversely into the stream of particles above the bottom screen and withdrawing the air upwardly through the upper screen.

LOWELL A. LEDGETT. CHARLES W. DEANE. JOHN J. MAHONEY.

References Cited in the file of this patent UNITED STATES PATENTS Name Date Frisby Sept. 5, 1871 Herr Aug. 5, 1873 Girvan June 25, 1889 Parkinson Dec. 16, 1889 Pfofi Nov. 7, 1899 Stanley Feb. 18, 1902 Trump Jan. 5, 1904 Busch Aug. 11, 1914 Wegner Oct. 1, 1918 Fowler Aug. 15, 1922 Schwantes Apr. 20, 1926 Peterson Apr. 28, 1931 Hutton Aug. 28, 1934 Smith June 1, 1937 Pehrson et a1. May 17, 1938 Ahlmann Nov. 5, 1940 Arnold Dec. 16, 1941 Reinders-Folmer Apr. 21, 1942 Smith June 1, 1943 Arnold Nov. 21, 1944 Mojonnier Oct. 23, 1945 Folmer Oct. 22, 1946 McGee July 27, 1948 Whitman Mar. 21, 1950 Sartorius Mar. 6, 1951 FOREIGN PATENTS Country Date Great Britain Mar. 9, 1929 Number Number