G R A N U L A T I O N STUDIES
I
Potassium Nitrate as an Aid to Fertilizer Granulation
D. R. BOYLAN and R. T. JOHNSON Chemical Engineering Department,
Iowa S t a t e University, Ames, Iowa
Because of the availability of potassium nitrate as a new raw material, its effect as an aid to granulation was studied. Small batches of an 8-6.98-1 3.28 (8-16-1 6)grade mixed ... taining potassium nitrate were granulated at different moisture and temperaa laboratory Roto-Louvre dryer. The optimum moisture in the feed and inlet ture were 9.6% and 450" F., respectively, for a maximum yic?Idof - 6+20fs. The distribution of the three primary nutrients, nitrogen, Iphosphorus, and ~ W U > N , ~ I ,was determined in the various product size fractions. Similar e:Kperiments were made on an 8-6.98-1 3.28 (8-16-1 6) grade mixed fertilizer containii'9 I only potassium chloride. The optimum Imoisture in the feed, inlet gas temperature levels, yield, and nutrient distribution were also . determined. . . . .At. ~least . .~.12.2% moisture W'as required for maximum yield, and the variation in nutrient dlstributlon was greater.
-
..
DoTASSIUM nitrate has a hiah ~~
1 nomic
value as a source of both nitrogen and potassium, but high cost has been a major limitation to its use in fertilizer formulations. The new production facilities of the Southwest Potash Corp. in Vicksburg, Miss., for a fertilizer grade potassium nitrate may make this material economically attractive, This has stimulated considerable interest in the granulation characteristics of mixed fertilizer formulations containing potassium nitrate and also in the physical properties of the resulting products. Studies (7-5) have shown that potassium nitrate is an aid to granulation. This paper presents results of laboratory studies using potassium nitrate in a vegetable grade fertilizer. Granulation experiments in a laboratory Roto-Louvre dryer were made on an 8-6.98-13.28 (8-1E-16) grade vegetable fertilizer to study the effects of moisture in the feed and of inlet gas temperature on the yield and distribution of plant nutrients in the various sized fractions. Two formulations were prepared (Table
I): Formulation I contained potassium nitrate which contributed 277, of the total potassium and 16% of the total nitrogen, and Formulation I1 contained potassium chloride as the only source of potassium. The solid raw materials (sieved through a 20-mesh Tyler screen) were mixed in a batch reactor and made to react with phosphoric acid and anhydrous ammonia. The moisture content was varied by adding predetermined amounts of water to fertilizer mixture. T h e experimental equipment is shown in Figures 1 and 2. Details of the reactor-mixer have been reported ( I ) . The batch reactor, in the center of Figure 1, was constructed from a section of 5-
34
J. A G R . F O O D C H E M .
I
~
Maieriol
Triple superphosphate Normal superphosphate Phosphoric acid Anhydrous ammonia Ammonium sulfate Potassium nitrate Potassium chloride Mannesium limestone (Evaporation loss 50 pounds)
Mixer-reactor assembly
.. .
Formulations for 8-16-16 G r a d e Fertilizer
BO&
Figure 1 .
.
~
Table 1.
.
inch O.D. Type 304 stainless steel tube ^, . witn a &//,,-mcn wall mickness. x stainless steel stirrer, consisting of a hollow shaft and four paddles, was used to mix the ingredients and to distribute the ammonia. The bench scale Roto-Louvre dryer on the right in Figure 2 was 13 inches in diameter and 311, inches long, and operated a t 7.4 P. p. m. T h e product was dried, screened, and analyzed for nitrogen,, phosphorus, and potassium. The time in the Roto-Louvre dryer was 30 and 45 minutes, respectively, for Formulations I and 11. Final product temperature ranged from 196' to 280° F. T o keep the number of variables a t a minimum, inlet gas temperature was varied while residence time in the dryer
Figure 2.
0 4 1 .0-0
0-20.6-0 0-62.9-0 82.2-0-o 20.5-0-0 13.4-0-44.6 0-0-58.4
___
__-
248 492 200 90 31 3 200 397 100
-
10 Total 2050
Granulator-dryer assembly
330 339 200 90 438
-
543 100 10 2050
Table 11. Relationship between Temperature and Moisture on Yield of -6 +20-Mesh Granules Yield o f
-6
Temp. of Inlet Gas, OF.
Run No.
4-20.
Moisture in Feed,
Mesh Granules,
%
%
Formulation I Cor taining Potassium Nitrate R-4 R-5 R-6 R-10 R-11 R-12 R-13 R-14 R-15 R-17 R-18 R-19 R-20 R-21
425 425 425 425 425 425 425 425 500 350 475 375 475 375
9.43 9.08 10.24 9.02 9.48 10.53 8.53 9.37 9.58 9.80 9.47 9.26 9.11 9.50
79.70 47.56 64.13 64.13 56.79 69.80 51.40 39.04 58.85 69.33 62.56 43.65 72.40 63.24
was held constant. If product temperature had been the variable, it would have been necessary also to vary residence time.
Discussion The experimental work followed the central composite rotatable design used by Boylan and Kamat (7). The central point was established by averaging four of six runs. The results of granulation experiments using each formulation are shown in Table 11. The data in Table I1 were analyzed by the composite design and plotted in Figures 3 and 4. Runs 5, 14, 103, and 104 were rejected statistically.
Figure 3 shows the relationship between temperature and yield for both formulations. Formulation I, containing potassium nitrate, shows a maximum yield of approximately 7001, at an inlet gas temperature of 455' F. Formulation 11, without potassium nitrate, shows no maximum within the inlet gas temperature range investigated, although a maximum might be obtained at a higher temperature level. Figure 4 shows the relationship between moisture and yield for both formulations. Formulation I shows a maximum yield of approximately 68% a t 9.6% moisture. Forumulation I1 shows
Temperature OF: (Inlet Gas) 475
25
Formulation I1 Conta ning Only Potassium Chloride R-100 R-101 R-103 R-104 R-105 R-106 R-107 R-108 R-109 R-110 R-111 R-112 R-113 R-114
475 475 475 475 475 475 550 400 475 475 525 525 425 425
12.85 11.78 12.35 12.32 10.94 12.28 12.26 12.69 13.26 11.43 11.39
i2.90 12.92 10.94
60.17 67.51 55.47 48.96 58.41 58.88 72.51 52.86 66.36 56.36 69 25 54.15 67.14
Table 111. No.
a
N,
%
PzO~,~
%
KzO,
%
1
I
ii .4i
+tl-Merh Granules Run
F o h u l a t i o n IContainir Potassium Nitrate h Formulation II Without Potassium Nitrate 0
Figure 3.
425 475 Temperature OF; (Inlet Gas) Effect of temperature on product yield
Nutrient Distribution in Various Sized Fractions -6 N,
%
+ 7 4-Mesh Granules Pz06,"
%
K20,
%
-74 N,
P ~ 0 6 , ~
%
%
-20-Mesh
$20-Mesh Granules
Formulation I Containing Potassium Nitrate 8.83 17.62 16.13 7.69 18.63
Granules
PzOj,"
KzO,
N.
%
%
%
KzO,
%
R-4 R-5 R-6 R-10 R-11 R-12 R-13 R-14 R-15 R-17 R-18 R-19 R-20 R-21
9.04 8.52 7.73 8.24 8.56 8.42 8.61 8.02 7.78 8.22 8.28 8.04 8.60 7.94
17.72 18.05 17.88 18.16 17.77 17.30 18.13 18.23 18.24 17.95 18.09 18.75 17.84 18.37
16.18 16.11 16.48 15.76 16.53 16.62 16.11 16.91 16.94 16.60 16.31 16.65 16.64 16.67
18.80 18.39 17.68 19.15 19.20 19.00 18.51 19.02 19.24 19.66 19.27 19.62 18.87
16.26 15.78 17.71 18.08 16.09 16.52 15.80 17.36 17.56 16.31 16.88 16.13 16.02 17,12
7.24 7.70 7.23 7.82 7.49 7.46 7.56 7.56 7.36 7.66 7.36 8.04 7.09 7.38
17.76 17.41 18.29 17.77 18.13 18.36 17.50 18.18 18.81 18.47 18.66 18.66 17.72 18.80
17.32 17.30 17.21 16.54 17.51 17.50 17.96 17.24 17.05 17.32 16.98 17.58 16.86 17.09
R-100 R-101 R-103 R-104 R-105 R-106 R-107 R-108 R-109 R-110 R-111 R-112 R-113 R-114
7.78 8.01 8.04 7.70 8.13 8.38 8.18 8.80 8.33 8.55 8.18 8.18 7.96 8.27
17.16 18.01 18.63 18.62 18.53 18.37 18.52 18.25 17.85 19.41 18.28 18.23 18.13 18.40
Fcn-mulation I1 Contai ning Only Potassium Chloride 16.74 7.98 17.43 16.42 7.28 18.20 16.74 7.96 18.81 16.53 7.08 19.28 16.24 8.36 17.91 16.49 7.96 19.42 16.53 7.55 19.41 16.21 7.06 19.85 16.45 8.35 18.48 16.09 7.44 18.46 16.35 7.98 18.66 16.50 7.20 18.62 16.52 8.12 18.20 16.78 7.36 19.16 16.00 8.90 16.95 16.27 8.16 18.52 16.06 8.04 18.16 16.30 7.00 18.74 15.20 15.27 8.60 18.10 7.52 17.25 16.60 8.52 16.90 16.21 7.44 18.75 16.83 8.18 18.41 7.44 19.50 16.27 16.60 7.92 18.52 16.86 7.14 19.24 16.10 8.66 18.60 15.78 7.40 17.58
17.68 17.42 16.02 16.50 17.82 18.36 17.77 16.10 18.07 18,91 17.45 17.14 17.50 19.08
7.44 7.18 7.36 6.91 7.31 7.36 6.98 7.56 6.83 7.38 7.02 6.96 6.82 7.48
18.24 19.30 19.26 19.00 18.71 18.80 20.01 18.91 19.66 18.26 19.16 19.17 19.59 18.50
16.98 17.15 16.53 17.44 17.00 17.24 16.25 17.13 16.41 18.08 17.51 17.76 17.16 17.79
8.64 7.55 8.18 8.56 8.64 8.64 8.28 7.72 8.30 7.89 7.68 8.20 7.87
18.32 18.45 18.29 18.06 17.93 18.12 17.96 18.52 18.52 18.73 18.85 18.38 18.79
15.80 16.70 16.03 16.03 1~. 6 . 0~. 6 15.59 15.80 16.77 16.09 16.41 16.80 16.00 16.19
8.23 6.94 7.46 7.80 7.64 8.00 7.34 7.26 7.78 7.21 7.79 7.38 7.48
~
Total.
VOL.
1 4 , NO. 1, JAN.-FEB.
1966
35
% Moisture I n Feed (Dry Basis) 10.0 2 80r
11.0
0
5 #
12.0
Conclusions
13.0
Legend 0 F&mu la tion I Containing Potassium Nitrate A Formulation II Without Potassium Nitrate
2ot
I
I
10.00 11.00 % Moisture I n Feed( Dry Basis) Figure 4. Effect of moisture on product yield
9.0
Table IV. Averaged Maximum Variation in Product Nutrient Content Formulation
N
pzos
Kz0
I I1
0.962 1,144
1.112 1,396
1,360 1,642
a maximum yield of approximately 62% at 12.2% moisture. The more pronounced dependence of yield on moisture in Formulation I is probably due to a higher solubility of the salt phase. Table I11 shows the nutrient distribution of both formulations in the various sized fractions of the granules. The averaged
maximum variation of nutrient content in the product was lower for Formulation I than for Formulation I1 for all nutrients (Table IV). The extent of agglomeration could be controlled by the mixing time after the addition of the \vater. Formulation 11 formed large agglomerates in the batch reactor, while Formulation I formed more uniformly sized granules. This was primarily due to the lower moisture requirement of the salt solution phase of Formulation I. This lo\\ er moisture resulted in a drying time of only 30 minutes at 425' F. for an average product moisture content of less than 1%; Formulation I1 required 45 minutes drying at 475' F.
Because of the high solubility of potassium nitrate at the elevated temperatures of granulation, Formulation I, containing potassium nitrate, required only 9.6yc moisture for a maximum yield of 67.6% in the -6 +20-mesh size fraction. Formulation 11, ivithout potassium nitrate, required 12.27, moisture for a maximum yield of 62.3%. This yield was considered good, since no recycle \+as employed. For a product with an average moisture content of less than 1%. Formulation I required a drying time of 30 minutes at an inlet gas temperature of 425OF; Formulation I1 required 45 minutes at 475' F. Literature Cited
(1) Boylan, D. R., Kamat, D. V., J. AGR.FOODCHEM.12, 423 (1964). (2) Hardesty: J. O.?unpublished data. (3) Hardesty, J. O., Dickey, G. F., Olive, B. iM., Farm Chem. 124, No. 2, 32 (1961). (4) Jacob, K. D., Comm. Fertilizer 107, No. 5, 23 (1963). (5) Smith, R. C., Agr. Chem. 19, No. 7 , 30 (1964). Receiwd f o r reciew .4pril 7, 7965. Accepted October 4, 7965. Diuision of Fertilizer and Soil Chemistry, 148th Meeting, ACS, Chicago, Ill., September 7964. Work supported by the Iowa Engineering Experiment Station, Iowa State University, through funds made auailable by the Southalest Potash Corp.
I N S E C T I C I D E M O D E OF A C T I O N
Absorption and Binding of DDT by the Central Nervous System of the American Cockroach
FUMIO MATSUMURA' and R. D. O'BRIEN Department of Entomology, Cornell University, Ithaca, N. Y.
It is hypothesized that DDT interferes with nervous function by forming a charge-transfer complex with a component of nerve. Studies on the kinetics and equilibria of DDT penetration into and out of nerve cords indicated the formation of complexes of DDT with two components of the cord and having dissociation constants of approximately 6 X 10-6M and 1.5 x lO-'M. At 10-5M DDT, about 834/, of the DDT in the cord is complexed. Two complexes have been partially purified on Sephadex and DEAE-cellulose columns. One contains protein and is extractable by butanol.
T
are presumed to owe their toxicity against insects to effects upon the nervous system because tremors and later HE CHLORINATED HYDROCARBONS
Present address, Department of Entomology, University of \.l'isconsm, Madison, TVis.
36
J. A G R . F O O D C H E M .
paralysis are the most prominent symptoms of poisoning, and because profound disturbances can be sho\vn electrophysiologically in nerve preparations from poisoned insects. The basis of these effects has never been experidemonstrated. Ho\\ ever, Mullins (7) has suggested that DDT and
related compounds owe their properties to precise fit in a hypothetical intermolecular lattice, and Gunther et al. (3) have proposed that Van der \\'sals binding to a protein in nerve is involved. From the effects of D D T upon negative afterpotentials in single axons and the modification of these effects by applied
