BACKGROUND OF THE INVENTION Pan granulating has been used extensively for granulating ores and raw meal for cement kilns. In- this process, a pan granulator is used to mix a solid particle with a liquid, usually water, to form granules of a desired size. The apparatus used will be referred to herein as a pan granulator; it is also known in the art as an inclined dish granulator, a disc granulator, a granulating table, an inclined pan, or a coating pan.

One of the drawbacks of pan granulating is that the liquid applied during the granulation step must be removed in a drying step. In many operations the drying step is the slowest step in the process and is often the capacity-limiting feature.

German Patent Application DE 3,246,493 (published June 20, 1984) discloses a process for the production of water-dispersible or water-soluble granules by subjecting a powdered material, such as an agrochemical, to a rolling or rotating motion and spraying with water vapor having a temperature between 25°C and 100°C. However, this process uses very fine (less than 100 microns) droplets of steam, no water is added, and the temperature refers only to the steam itself and not the ingredients on the pan bed.

It is an object of the present invention to provide an improved process for pan granulating utilizing a minimal amount of water. It is a further object of the present invention to provide a pan granulating process using high temperature steam.

These and other objects, features and advantages of the present invention will become readily understood upon having reference to the following description of the invention.

SUMMARY OF THE INVENTION

It has been discovered that the process for pan granulating can be improved if sufficient saturated or superheated steam is applied to the ingredients on the surface of the rotating pan to raise their temperature to 30-120°C, preferably 35-70-C. The addition of this steam reduces the amount of liquid necessary for granulation, thereby requiring less drying time for the product granules. The process is particularly _^ useful in granulating ingredients that normally require large amounts of moisture during gcanulation.

The improved process of the invention can be used to granulate many materials. It is particularly useful to granulate crop protection chemicals. When these materials are granulated with steam, the resultant granules display optimum properties such as rapid dispersion in various fluids (e.g., water) and attrition resistance.

DESCRIPTION OF THE FIGURE The Figure is a view of a conventional pan granulator having means for applying steam to the ingredients on the surface of the pan. DESCRIPTION OF THE INVENTION

The invention relates to an improved process for pan granulation by the simultaneous application of heat and moisture, in the form of saturated or superheated steam, to the tumbling ingredients on the surface of the rotating pan.

An apparatus useful in the process of the invention will be described with reference to the Figure.

Any conventional pan granulator can be modified for use in the process of the invention. The Figure is a simplified drawing of a conventional model.

A shallow cylindrical pan 1 is attached to a base support 2 and rotated about an inclined axis. The rotation is accomplished by a drive means (not illustrated) which is operably connected to the pan 1 through the axle 3. The angle of inclination and the speed of rotation of the pan are usually variable and are adjusted as is conventional to produce the desired size granule. The ingredients that are granulated on the pan are a mixture of solids and liquid, usually water. The solids are supplied to the surface of the pan through a discharge means 4 and liquid is supplied by spray means 5. The solids can be either one material or a mixture, and often it is desirable to premill to a particle size between 2 and 30 microns. The solids can also be supplied partly by a recycle of over- or undersized granular product.

In operation it is desirable that the liquid be sprayed on a moving bed of the solid materials and absorbed and not sprayed on the surface of the pan. The spray droplet size is determined in the conventional manner, i.e. it is a function of the feed size and the desired granule size. The finer the spray, the smaller the granules.

The granulator can also contain a side wall scraper 6 and a bottom scraper 7 to prevent build up of the ingredients on the pan surfaces. The bottom scraper can be of the reciprocating type and also can

serve to maintain a uniform deposit of material on the surface of the pan. In the apparatus of the invention steam is saturated or superheated and applied to the ingredients on the pan. Thus steam is supplied through a conduit 8, through a metering valve 9, to a series of nozzles 10. The nozzles can be located anywhere on the pan surface that permits efficient contact with the tumbling ingredients. The location of the nozzle is chosen to make granules of the desired size.

In operation, solids, often premilled, are continuously fed through opening 4 into the pan and water is added by sprayer 5 in the conventional manner. Steam is also introduced into the rotating pan 1 by the nozzles 10. The rate of addition of saturated or superheated steam is adjusted by valve 9 to obtain a pan bed temperature of 30° to 120°C, preferably 35° to 70°C. The temperature of the steam it≤elf which is applied to the pan is greater than or equal to 100°C, preferably between 100°C and 400°C. The maximum temperature of the mixture of ingredients is limited only by the stability or melting point of the solid particles. In operation the beneficial effect of the addition of steam is usually not observed at temperatures below 30°C. As the ingredients are mixed and treated with the steam, granules grow in size and the largest granules overflow from the bottom edge of the pan in the usual fashion.

The pan angle and rotation rate are selected using known relationships to provide the desired granule formation.

The amount of water added is determined based on the desired granule size. When steam is introduced and the pan temperature rises, the moisture requirement for the desired granule size is reduced by as much as 30 to 40%, and preferably at ^' least 20%.

It should be understood that the apparatus of the Figure is hereby illustrative. In another useful embodiment (not illustrated) the pan is rotated clockwise with the steam nozzles located near where the granules overflow. As this pan rotates, after the steam addition, the water is added and then the premix of solid ingredients.

The advantages of the invention arise from the fact that less moisture is required in the granulation process; this results in substantially reduced drying time to remove water from the product granules. Thus the granulation process requires less drying capacity. There is also decreased decomposition during the granulation of materials that have limited stability in water, since the material is contacted with substantially less water than in the art process. Also useful is the large size and high quality of the product granules in comparison to those formed without raising the temperature of the mixture, since the product is less subject to attrition during handling, and the product appears more attractive due to large, uniform granules.

The term "crop protection chemical" is intended to refer to biologically active compositions containing chemicals which are effective in killing pests or preventing or controlling their growth. These chemicals are commonly known as herbicides,

fungicides, insecticides, nematocides, acaricides, miticides, virucides, algicides, bactericides, plant growth regulants and their agriculturally suitable salts. These chemicals may be water-soluble or water-insoluble and may be solLd or liquid at room temperature, providing the liquids are first adsorbed onto solid carriers before granulation. Examples of

10 suitable crop protection chemicals are shown in, but not limited to. Table I.

^{^} 15

20

5

0

5

I__SI_£ 1

HERglCIPgS

Cmp . No . ^~ o ^~~ non Name fflτP , ( °C? Chemical Name

acifluorfen 142-160 5-[2-c__loro-4-(trifluoro methyl)phenoxy]-2-nitro- benzoic acid

alachlor 39-42 2-chloro-2' , 6 '-diethyl-N-

(methoxymethyl)-acetanilide

asula 142-144 methyl [(4-aminophenyl)- sulfonyl]carbamate

atrazine 175-177 6-chlo ^~ o-N-ethyl-N'-(l- methylethyl)-1,3 ,5- triazine-2,4-diamine

bensulfuron 185-188 2-[[[[(4,6-dimethoxy-2- methyl pyrimidinyl)amino]- carbonylJamino]sulfonyl]- methyl]benzoic acid, methyl ester

bentazon 137-139 3-(l-methylethyl) -(lH) -2, 1, 3- benzothiadiazin- ( 3H) -one , 2, 2 -dioxide

bromacil 158-159 5-bromo-6-methyl-3-( l-methyl- propyl ) -2 , 4 ( 1H, 3H) pyrimi- dinedione

3

Cmpd.

No . Common Name m,P . ( °C? Chemical Name

8 bromoxynil 194-195 3 , 5-dibromo-4-hydro ^~ :ybenzo- nitrile

chloramben 200-201 3-amino-2,5-dichlorobenzoic acid

10 chlorimuron >100 2-1[tC(4-chloro-6-π.etho ^~ y-2- ethyl pyrimidinyl)amino]carbonyl]- amino]sulfonyljbenzoic acid, ethyl ester

11 chloroxuron 151-152 N'-[4-(4-chlorophenoxy)- phenyljN,N-dimethylurea

12 chlorsulfuron 174-178 2-chloro-N-[[(4-methoxy-6- methyl-1,3,5-triazin-2-yl)• amino]carbonyl]benzene- sulfonamide

13 chlortol ron 147-148 N*-(3-chloro-4-methylphenyl)■ N,N-dimethylurea

14 clomazone 2-[(2-chlorophenyl)methyl]- 4,4-dimethyl-3-isoxazoli- dinone

15 cyanazine 166-167 2-[[4-chloro-6-(ethylamino)- 1,3,5-triazin-2-yl]amino]- 2-methylproρanenitrile

Cmpd.

No . Common Name ^~ >- g- ( °C? Chemical Name

16 dazomet 104-105 tetrahydro-3,5-dimethyl-2H- 1,3,5-thiadiazine-2-thione

17 des ediphan 120 ethyl [3-[[(phenylamino)- carbonyl]oxy]phenyl]- carbamate

18 dicamJa 114-116 3,6-dichloro-2-methoxybenzoic acid

19 dichlobenil 139-145 2,6-dichlorobenzonitrile

20 dichlorprop 117-118 (±)-2-(2,4-dichlorophenoxy)- propanoic acid

21 diphenamid 134-135 N,N-dimethyl-α-phenylbenzene- acetamide

22 dipropetryn 104-106 6-(ethylthio) -N,N ' -bis( l- methylethyl)-l, 3 , 5- triazine-2,4-di amine

23 diurσn 158-159 N'-(3,4-dichlorophenyl)-N,N- dimethylurea

24 thiameturσn >100 3-[[[[(4-methoxy-6-methyl-

1,3,5-triazin-2-yl)aminoJ- carbonyl]amino]sulfonyl]- 2-thiσphenecarboxylic acid, methyl ester

43

10

Qnpd. yp Common Name p. r Pr ( °C? Che icaJ, g? ^~ e

25 >100 2-[[[[N-(4-methoxy-6-methyl- 1,3,5-triazine-2-yl)-N- methylaminσ]carbonyl]- amino]sulfonylJbenzoic acid, methyl ester

26 fesac 156 2,3, -trichlorobenzeneacetic acid

27 fenuron 133-134 N,N-dimethyl-N*-phenylurea

28 fluometuron 163-164 N,N-dime hyl-N'-[3-(trifluoro¬ methy1)phenyl]urea

29 fluridone 151-154 l-methyl-3-phenyl-5-[3-(tri- fluoromethy1)phenyl]- 4(1H)-pyridinone

30 fomesafen 220-221 5-[2-chloro-4-(trifluoro¬ methyl)phenoxy]-N-(methyl- sulfonyl)-2-nitrobenzamide

31 glyphosate 200 N-(phosphonomethy1)gl cine

32 hezazinone 115-117 3-cyclohexyl-6-(dimethyl- aminσ)-l-methyl-l,3,5- triazine-2,4(lH,3H)-diσne

11

Cmpd.

No . Common Name l ^~ t P - ( °C) Chemical Natng

33 imazamethabesz >100 6-(4-isopropyl-4-methyl- 5-oxo-2-imidazolin-2-yl)- m-toluic acid, methyl ester and 6-(4-isopropyl-4-methyl- 5-oxo-2-imidazolin-2-yl)- 2-toluic acid, methyl ester

34 imazaquαn 219-222 2-[4,5-dihydro-4-methyl-4- (1-methylethyl)-5-oxo-lH- imidazol-2-yl]-3- ^~ uinoline- carboxylic acid

35 imazethapyr 172-175 (i) -2- [4 , 5-dihydro-4-methyl-4-

( 1-methylethyl ) -5-oxo-lH- imidazol-2-yl]-5-ethyl- 3-pyridinecarboxylic acid

36 ioxynil 209 4-hydroxy-3,5-diiodobenzo- nitrile

37 isoproturon 155-156 N-(4-isoprop Iphenyl)-N' , ' dimethylurea

38 isouron 119-120 N'-[5-(1,1-dime hylethy1)-3- isoxazoly1]-N,N-dimethylure

39 isoxaben 176-179 N-[3-(l-ethyl-l-methylpropyl) 5-isoxazolyl]-2,6-dimethoxy benzamide

3

12

Cmpd.

_£2 • Common Name ^~ N P - ( °C) Chemical Name

40 J arbutilate 176-178 3- [ [ (dimethylamino) carbonyl] - amino ] phenyl- ( 1, 1-dimethyl- ethyl ) carbamate

41 lenacil 316-317 3-cyclohexyl-6,7-dihydro-lH- cyclopentapyrimidine-2,4- (3H,5H)dione

42 linuron 93-94 3-(3,4-dichlorophenyl)-1- methoxy-1-methylurea

43 MCPA 100-115 (4-chloro-2-methylpheπoxy)- acetic acid

44 MCPB 100 4-(4-chloro-2-meth lphenoxy)• butanoic acid

45 efluidide 183-185 N-[2,4-dimethyl-5-[[(tri- fluoromethyl)sulfonyl]- amino.phenyl]acetamide

45 methabenz- 119-120 1,3-dimethy1-3-(2-benzothia- thiazuron zolyDurea

47 methazole 123-124 2-(3,4-dichlσrophenyl)-4- methyl-1,2,4-oxadiazol- idine-3,5-dione

48 metolachlor liquid 2-chloro-6'-ethyl-N-(2- methoxy-1-methylethyl)- acet-o-toluidine

13

Cmpd. _!_____ Common Name m.O . ⁽ °o Chemical N ^~~ I ^~

49 metribuzin 125-126 4-amino-6-(l,l-dimethylethyl)> 3-(methylthio)-1,2,4- triazin-5( H)-one

50 metsulfuron 163-166 2-[[[[(4-methσxy-6-methyl- methyl 1,3,5-triazin-2-yl)amino]- carbonyl]aminoJsulfonyl]- benzole acid, methyl ester

51 onuron 174-175 N'-(4-chlorophenyl)-N,N- dimethylurea

52 naptalam 185 2-[(l-naphthalenylaι ^~ ino)- carbonyl]benzoic acid

53 neburσn 102-103 l-butyl-3-(3,4-dichloro- phenyl)-1-methylurea

54 nitralin 151-152 4-(methylsulfonyl)-2,6- dinitro-N,N-dipropy1- aniline

55 norflurazon 174-180 4-chloro-5-(methylamino)-2-

[3-(trifluoromethyl)phenyl 3(2H)-pyridazinone

56 oryzalin 141-142 4-(dipropylamino)-3,5-dinitr benzenesulfona ide

57 perfluidone 142-144 1,1,1-trifluoro-N-[2-methyl- 4-(phenylsulfonyl)phen l]- me hanesulfonamide

3

14

Cmpd. ________ Common Name m.p..°C) Chemical Name

58 phenmedipham 143-144 3-[(methoxycarbonyl)amino]- phen l (3-methyIphenyl)- carbamate

59 picloram >215 4-amino-3,5,6-trichloro-2- (DEC) pyridinecarboxylic acid

60 prometryn 118-120 N,N'-bis(1-methylethyl)-6-

( ethylthio)-1,3,5-triazine- 2,4-diamine

61 pronamide 155-156 3,5-dichloro-N-(1,1-dimethyl- 2-propynyl)benzamide

62 propazine 212-214 6-chloro-N,N ^• -bis(1-methyl¬ ethyl)-1,3,5-triazine- 2,4-diamine

63 pyrazon 205-206 5-amino-4-chloro-2-phenyl- 3(2H)pyridazinone

64 siduron 133-138 N-(2-methylcyclohexyl)-N'- phenylurea

65 iimazine 225-227 6-chloro-N,N ^* -diethyl-l,3,5- triazine-2 ,4-diamine

66 sulfometuron 182-189 2-[[[[(4,6-dimeth l-2- methyl pyri idinyl)amino]carbonylJ■ amino]sul onylJbenzoic acid, methyl ester

15

Cmpd.

No . Common Name ι ^~ . p. ( °C) Chemical Name

67 tebuthiuron 161-164 N- [5-(l, l-dimethylethyl ) - l, 3 , 4-thiadiazol-2-yl ]- N, ' -dimethylurea

68 terbacil 175-177 5-chloro-3- (l, 1-dimethyl - ethyl) -6-methyl-2 , 4 ( 1H, 3H) ■ pyrimidinedione

69 terbuthyl- 177-179 2-(i≤χ_;-butylamino) -4-chloro- azine 6-(ethyl-amino)- ^~ .-triazine

70 terbutryn 104-105 N-(l,l-dimethylethyl)-N'- ethyl-6-(methylthio)-1,3,5- triazine-2,4-diamine

71 triclopyr 148-150 [ ( 3 , 5, 6-trichloro-2-pyri- dinyDoxy] acetic acid

72 trifluralin 48-49 α,c_,α-trifluoro-2, 6-dinitro-

N,N-dipropyl-p-toluidine

73 2,4-D 140 (2,4-dichlorophenox )acetic acid

74 2,4-DB 119-120 4-(2,4-dichlorophenσxy) butanoic acid

75 triasulfuron >100 (3-(6-methoxy-4-methyl-l,3,5- triazin-2-yl)-l-[2-(2- chloroethoxy)phenylsulfonyl urea

43

16

Cmpd.

No . g ^~ ro ^{~ ~~} _ Name m.p. . °c) Ch ^~~ ιAcaA N ^~~ ιe

76 primisulfuron >100 [2-/3-(4,6-bis(difluoro- methoxypyrimidin-2-yl- ureidosulfonyl)benzoic acid methylester]

77 >100 t2-/3-(4,6-bis(difluoro¬ methoxy)-pyrimidin-2-yl)- ureidosulfonyl)-benzoic acid methylester]

78 NC-311 170-172 [5-pyrazolesulfonamide, N-[(4- methoxy-6-methyl- pyrimidine-2-yl)-amino- carbonyl]-4-methoxy- carbonyl-1-methyl-]

79 160-162 N-[[(4,6-dimethoxy-2- pyrimidinyl)amino]carbonyl]•

3-(ethylsulfonyl)-2- pyridinesulfonamide

80 152-159 2-[[[[(4,6-dimethoxy-2- pyrimidinyl)amino]carbonylJ• amino]sulfonyl]-N,N- dimethyl-3-pyridine- carboxamide

81 204-206 Methyl 2-[[[[[4-ethoxy-6-

(methyla ino)-1,3,5-triazin- -yl]amino]carbonyl]amino]- sulfonyl]benzoate

17

Cmpd. No . Ccm ^~ ι ^~ n am-g p . p . ( °c? Ch ^~~ ιaca.. Fame

■WSICIPSS

82 carbendazim 302-307 methyl 2-benzimidazole- carbamate

83 thiura 146 tetramethylthiuram disulfide

84 dodine 136 n-dodecylguanidine acetate

85 chloroneb 133-135 l,4-dichloro-2,5-dimethoxy- benzene

86 cymoxanil 160-161 2-cyano-N-ethylcarbamoyl- 2-methoxyiminoacetamide

87 captan 178 N-trichloromethylthiotetra- hydrophthalamide

88 folpet 177 N-trichloromethylthio- phthalimide

89 thiophanate- 195 dimethyl 4,4 * -(o-phenylene) - e hyl bis ( 3- hioallophanate )

90 thiabendazole 304-305 2-(thiazol-4-yl)benzimida- zole

91 chlorothalonil 240-241 tetrachloroisophthalo- nitrile

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18

Cmpd.

No . Common Name . p - ( °C? Chemical Name

92 dichloran 195 2,6-dichloro-4-nitroaniline

93 captafol 160-161 cis-N-[1,1,2,2-tetrachloro- ethyl)thio]cyclohex-4- ene-1,2- dicarbioximide

94 iprodione 133-136 3-(3,5-dichlorophenyl)-N- (1-methylethyl)-2,4- dioxo-1-imidazolidine carboxamide

95 vinclozolin 108 3-(3,5-dichlorophenyl)-5- ethenyl-5-methyl-2,4- oxazolidinedione

96 kasugamycin 202-204 Jcasugamycin (DEC)

97 triadimenol 121-127 beta-(4-chlorophenoxy)-α-

( 1 , 1-dimethylethyl ) -1-H- 1, 2, -triazol-l-ethanol

98 flutriafol 130 +-α-( -fluorophenyl-α-(4- fluorophenyl)-1H-1,2,4- triazole-1-ethanol

99 flusilazol 52-53 1-[[bis(4-fluorophenyl)- HC1 201-203 methylsilyl)methyl]-lH- 1,2,4-triazole

19

Cmpd.

No . Common Name "irp- . °C . Chemical N m _' .

100 hexaconazole 111 (+/_)_α_butyl-α-(2,4-di chlorophenyl)-1H-1,2,4- triazole-1-ethanol

10101 fenarimol 117-119 α-(2-chlorophenyl)-α(4- chlorophenyl)-5-pyri- dinemethanol

15 BACTERICIDES

102 oxytetracycline 181-182 oxytetracycline dihydrate dihydrate (DEC)

20

ACARICIDES

103 hexathiazox 108-109 trans-5-(4-chlorophenyl)-N- cyclohexyl-4-methyl-2-oxo-3-

25 thiazolidinecarboxamide

104 oxythioquinox 169-170 6-methyl-l,3-dithiolo-

[2,3-B]quinonolin-2-one

30105 dienochlor 122-123 bis(pentachloro-2,4-cyclo- ρentadien-1-yl)

106 cyhexatin 245 tricyclohexyltin hydroxide

35

3

20

Cmpd.

No . Common Name m.p . ( °C) Chemical Name

Σ-TSSCTICIPES

107 carbofuran 150-152 ethylcarbamic acid, ester with 2,3-dihydro-2,2-di- methyl-7-benzofuranol

108 carbaryl 142 methylcarbamic acid, ester with a-naphthol

109 thiodicarb 173-174 dimethyl N,N ^, -(thiobis- (N-methylimmo)carbonyl- oxy]]-bis[ethanimido- thioate]

110 deltamethrin 98-101 α-cyano-3-phenoxybenzyl-cis- 3-(2,2-dibromovinyl)-2, - dimethylcyclopropane carboxylate

111 methorny1 78-79 S-methyl N-(methylcarbamoyl- ox )thioacetimidate

The following Examples are offered to further illustrate various embodiments of the invention and are not intended to be limiting in any way.

EXAMPLE 1 A conventional pan granulator (Mars Mineral DP14), after being modified for steam addition, was employed to produce herbicide granules. Diameter of pan 35.6 cm

Angle of pan 55°

Speed of rotation of pan 39 rpm

Height of pan wall 6.4 cm

To the apparatus was added a premilled premix of solid ingredients of the following weight composition:

84% 5-bromo-6-_nethyl-3-(l-methylproρyl)- 2,4(1H, 3H)pyrimidinedione 5% dispersant 2% wetting agent

6% binder

3% diluent, at the rate of 140 g/min. Water was first added to the pan at a rate such that the moisture content was 15% by weight. Thereafter the water feed was reduced to produce a moisture content of 11% by weight and sufficient steam added to raise the temperature of the ingredients in the pan to 32°C. The addition of the steam reduced the drying time from about 10 minutes to 7 minutes and the observed quality of the granular product was good. The granule size ranged from about 500 to 3000 microns.

EXAMPLE 2 A conventional pan granulator (Teledyne Corp.), after being modified for steam addition to the pan, was employed to produce herbicide granules.

Diameter of pan 91.4 cm

Angle of pan 55° Height of pan wall 16.5 cm

Speed of pan rotation 22-28 rpm

To the granulator was added a premilled premix of solid ingredient of the following composition (by weight percent): 92.8% 2-[[4-chloro-6-(ethylamino)-l,3,5- triazin-2-yl]amino]-2-methylproρane- nitrile 5.7% dispersant 1% wetting agent 0.5% antifoam, at the rate of 136 Kg/hour.

In operation, the moisture requirement for pan granulation was reduced from 18-20% with water to 11-13% when steam was added at a rate to produce a material temperature in the pan of 65-75°C. The drying time was reduced from about 8 minutes to 6 minutes by the use of steam. The granule size ranged from about 300 to 3000 microns and the granules were uniformly spherical in shape.

EXAMPLE 3 The granulator of Example 2 was used to granulate the following premix at the rate of 136 Kg/hour:

69.6% 2-[[4-chloro-6-(ethylamino)-l,3,5- triazin-2-yl]amino]-2-methylproρane- nitrile

23.2% 6-chloro-N-ethyl-N'-(1-methylethyl)- l,3,5-triazine-2,4 diamine 5.7% dispersant 1% wetting agent 0.5% antifoam

The moisture requirement for pan granulation was reduced from 18-20% with water to 11-14% when steam was used to increase the material temperature in the pan to 65-70°C. The drying time was reduced from about 8 minutes to 6 minutes. The granules ranged in size from about 300 to 3000 microns and the granules were uniformly spherical in shape.