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Mamataliev Adurasul, Ph D., in technique, senior scientist "Phosphate fertilizer" laboratory, Institute of General and Inorganic Chemistry of the Academy of Sciences of the Republic of Uzbekistan
Tashkent, Uzbekistan E-mail: [email protected] Namazov Shafoat, Doctor of science, professor, academic, chief of "Phosphate fertilizer" laboratory, Institute of General and Inorganic Chemistry of the Academy of Sciences of the Republic of Uzbekistan
Tashkent, Uzbekistan E-mail: [email protected] Kurbanov Jakhongir, Junior scientific researcher "Ph osphate fertilizer" laboratory, Institute of General and Inorganic Chemistry of the Academy of Sciences of the Republic of Uzbekistan
Tashkent, Uzbekistan E-mail: [email protected]
NITROGEN POTASSIUM CONTAINING DIFFICULT FERTILIZERS ON THE BASE OF MELT AMMONIUM NITRATE AND POTASSIUM CHLORIDE
Abstract: With the aim of modifying ammonium nitrate, reducing its explosive properties, the process of obtaining nitrogen and potassium fertilizers based on it has been studied by introducing into its melt the potassium chloride produced by the Dehkanabad potash fertilizer plant. The composition of the fertilizers obtained is determined. The main indicator of the modification is the strength of the granules. if for pure ammonium nitrate it is equal to 1.6 MPa, then for fertilizer with the ratio N: K2O = 1: 0.5 it is 7.53 MPa and at a ratio of N: K2O = 1: 1 it is 8.36 MPa.
Keywords: ammonium nitrate, melt, potassium chloride, nitrogenpotassium fertilizer, density, viscosity and strength of granules.
Introduction total capacity of the three plants producing of am-
Ammonium nitrate is the most popular and monium nitrate (JSC "Chirchik-Maxam", "Navoi-
effective nitrogen fertilizer in the world. In 2007, azot" and "Ferganaazot"), exceeded 1 million 750
the world capacity of its production amounted to thousand tonnes per year. It used in agriculture
43 million tons per year [1]. In Uzbekistan, the for all types of cultures and on any type of soil.
But it has very serious drawback - the risk of explosive [2].
Thereby have been tightened requirements for quality of ammonium nitrate and the conditions of its storage. Before manufacturers assigned the problem - to provide transferring to production of fertilizers based on ammonium nitrate, preserving agrochemical efficiency with significantly greater resistance to external influences and, accordingly, less explosive.
As substances - additives, reducing the level of potential danger of ammonia slit, are used:
1) carbonate-containing compounds of natural and technogenic origin (chalk, calcium carbonate, dolomite);
2) potassium-containing substances (potassium chloride and potassium sulfate);
3) substances containing the same name cation - ammonium (ammonium sulfate, ortho-and polyphosphate of ammonium);
4) other ballast substances that do not carry a payload, but which determine only the mechanical dilution of ammonium nitrate (plasterboard, phos-phogypsum and others) [3].
The first group of additives used in the production of so-called calcium ammonium nitrate [4-6]. Nowadays 31 company in Europe and 5 enterprises in Russia produced it. But its application is effective only in European's acidic soils. It is uneffective in Uzbekistan's alkaline carbonate soils. Besides, calcium ammonium nitrate in flour state is also explosive.
From the second group of additives is more used potassium chloride for the production of potassium-ammonium nitrate. Potassium-ammonium nitrate is produced a lot of in some foreign countries, with containing 16-16.5% N and 25-28% K2O [7]. It produced by following methods: 1) by mechanically mixing the dry components or wetted ammonium nitrate and potassium chloride; 2) evaporation of solutions of ammonium nitrate and potassium chloride; 3) addition to concentrated solution or melt of ammonium nitrate micronized potassium chloride
followed by melt granulation in granulation towers. In Russia, production of nitrogen-potassium fertilizer on the base of ammonium nitrate and potassium chloride first time was produced at JSC "Nevinno-missk Vneshtreydinvest" in 1999. The method of obtaining the composition of fertilizer are protected by patent of the Russian Federation [8]. For production used the ammonium nitrate melt with concentration of 85-92% NH4NO3 and granulation mixture conducted in granulating drum. Besides produces more homogeneous fertilizer composition.
Startup in Uzbekistan Dehkanabad potassium plant, the capacity of which will soon come up to 360 thousand tonnes of K2O per year by form of potassium chloride, it opens perspective plans for production of nitrogen-potassium fertilizer on the basis of ammonium nitrate. Potassium sulfate is not produced in Uzbekistan. At same time we have observed large deficit of chlorine-free fertilizers.
Substances of third group used at JSC "Cherepovets Azot", where in 2002 was organized production of stabilized ammonium nitrate with composition of 32% N, 5% P2O5 capacity of 400 thousand tonnes of fertilizers per year by additive liquid complex fertilizer containing 11% N and 33% P2O5 to nitrate melt obtaining from superphosphoric acid that is used in the additive mixture of ammonium ortho- and polyphosphates.
This addition increased the temperature of nitrate decomposition on 22-24 °C, slowed the speed of its thermal decomposition, increased granule strength, reduced porosity of product, made nitrate more resistant to repeatedly repeated phase transformations, and most importantly-reduced ability to detonation of ammonium nitrate [9-12]. But superphosphoric acid is not produced in Uzbekistan. In addition, it is very expensive.
Having good prospects of fourth group is of additives to ammonium nitrate: gypsum and phos-phogypsum [13-19]. In these works, developed technology of obtaining thermostable fertilizers based on ammonium nitrate by addition to its melt
dihydrate, hemihydrate phosphogypsum and natural gypsum. The product with 5 percent additive phos-phohemihydrate and containing 33.6% N has twice the strength of granules than pure nitrate, retained 100% friability for 4 months, 7 withstanding thermal cycles at temperatures without 20-60.
The product has a significantly higher thermal stability compared with pure ammonium nitrate (the activation energy of pure ammonium nitrate 160 kJ/mol, with maximum amount of additive phosphogypsum was 240 kJ/mol).
So we decided to test the process of obtaining nitrogen potassium containing fertilizers by additive to melt of ammonium nitrate perspective additives-potassium chloride production plant Dehkanabad potash fertilizers.
Materials and Methods
For conduct of laboratorial experiments for investigation of obtaining nitrogenpotassium containing fertilizers was used granulation ammonium nitrate (34.5% N) production of JSC "Maxam-Chirchik", crystalline potassium chloride (60% K2O), production of plant Dehkanabad potassium fertilizers.
Model laboratory apparatus consisted of two-liter cylindrical reactor made from stainless steel 12X18H10T equipped with stirrer and motion by motor. At first, the reactor was charged with amount of granulated ammonium nitrate and exposed it to melt. The temperature in reactor was 175-180°C. Then to ammonium nitrate melt added calculated amount of potassium chloride and the mixture was thoroughly stirred for 15 minutes.
The weight ratio of ammonium nitrate to potassium chloride by N: K2O was in the range from 1: 0.1 to 1: 1 [20-23]. After 15 minutes of reaction the components in melt is poured into porcelain dish and intensively stirred with glass rod. As cooling formed solid particles of round shape. The mass was cooled and then seeded in particle size.
Particles with size 2-3 mm were analyzed on strength of granule accordingly by State Standard (SSt) 21560.2-82. Then products are grained and analyzed for nitrogen, potassium and sulfur by known methods [24]. Studied dissolution rate of granules with size 2 mm. These granules was put into glass with 100 ml of distilled water and observing visually, fixed time of its complete dissolution. Temperature was 25°C and tested five-times. It was also tested the extent to which the conversion takes place in the melt of ammonium nitrate mixture of ammonium nitrate and potassium chloride. The degree of conversion of NH4NO3 was determined by the method described in [25].
We determined the rheological properties of melts obtained nitrogenpotassium containing complex fertilizers. Density was measured by bottle method and viscosity was measured by using a glass capillary viscometer (GCV-2) with a diameter of 0.77 mm. Experiments spent in the following way. Samples of ammonium nitrate with additive potassium chloride melted, mixed thoroughly, cooled to room temperature and milled. The obtaining powders were injected into the pycnometer, and the vis-cometer, which are then placed in the thermostat filled with glycerin.
Table 1.- The composition and properties of nitrogenpotassium and nitrogenpotassiumsulfur containing complex fertilizers
Ratio of mass N: R20 Content of components, mas.% Degree of conversion NH4NO3,% Strength of granules, MPa Time of full dissolution, sec
N R2°
1 2 3 4 5 6
100: 0.0 34.5 - - 1.6 46.8
1: 0.1 32.41 3.24 5.96 4.37 63.9
1 2 3 4 5 6
1: 0.2 30.53 6.04 11.43 5.13 69.8
1: 0.3 29.40 8.82 16.84 6.99 92.4
1: 0.5 26.80 13.40 22.96 7.53 110.4
1: 0.7 24.60 17.22 27.37 7.91 120.2
1: 0.8 23.60 18.90 29.84 8.14 134.2
1: 1.0 21.90 21.90 32.55 8.36 137.0
The temperature in thermostat was raised to the predetermined value. The powder in the pycnometer and viscometer was melted. If melting level in the pycnometer not reached the level, added the new portion of powder. If melting level exceeds the mark, the surplus of melt was removed with cotton at the end of the wire. The temperature in the thermostat was controlled with the contact thermometer. The melt was kept at predetermined temperature for 5-7 minutes and then made measurements.
The laboratory tests results are shown in (Table 1).
Results and its discussion
It is seen, that confirm the content of nutrients proximity fertilizer samples prepared in the laboratory and on model set. Nitrogen and potassium contents according to ratio of N: K2O is from 21.90 to 32.41 and from 3.24 to 21.90%, respectively.
When mixing the fusion of ammonium nitrate with potassium chloride, the process of conversion of ammonium nitrate to potassium nitrate occurs. The degree of conversion of ammonium nitrate essentially depends on the amount ofpotassium chloride in the mixture. With a decrease in the N: K2O mass ratio from 1: 0.1 to 1: 1, the degree of NH4NO3 conversion increases from 5.96 to 32.55%.
Strength granules of potassium-ammonium nitrate also depends from amount of potassium chloride. When amount of potassium chloride rise from 1: 0.1 to 1: 1, strength granules of NK-complex fertilizers increased from 4.37 to 8.36 MPa. This confirms that interaction of the ammonium nitrate and potassium chloride formed product with reduced ability to detonation.
Table 1 show, that time of full dissolution of pure ammonium nitrate is 46.8 seconds. With the
increase in the proportion of potassium chloride
in mixture of nitrate granules time full dissolution of nitrogen-potassium fertilizer steady rising and reaching 137.0 seconds for sample in ratio of N: K2O = 1: 1. It means that, obtaining fertilizer will be considerably (3 times) more slowly wash out from soil than pure ammonium nitrate.
Hygroscopic point, kinetics ofwater vapor sorption and sorption moisture capacity, and granules of nitrogenpotassium containing complex fertilizers on the base of ammonium nitrate melt and potassium chloride were defined in.
Ammonium nitrate when the moisture 3.5% strongly caking and loses friability, and samples of nitrogenpotassium fertilizer retain the appearance and friability with moisture content of 5-6%. When humidity 7%, they will be lose ability to sieving. Therefore, we still recommend packed potassium and ammonium nitrate in paper or plastic bags [23].
In further researches determined rheological properties of melts obtained fertilizers. The results are shown in (Table 2). The data of (Table 2) are shown, the density and viscosity of the melt of ammonium nitrate considerably increased with increasing amount of additives. Pure ammonium nitrate at 165°C does not melt and, of course, does not fluid. Potassium chloride additive reduces its melting point. Mixture of ammonium nitrate and potassium chloride in ratio N: K2O of from 1: 0.1 to 1: 0.4 starts melting at 165°C and while the melt has high viscosity but flowing easily. Increasing the proportion
of potassium chloride from 0.1 to 0.5 at tempera- nitrate-chloride melt from 1.487 to 1.532 g/cm3 and ture 175 oC, that increases density and viscosity of a from 5.98 to 12.73 cps, respectively.
Table 2.- The rheological property of melt nitrogenpotassium and nitrogen-potassiumsulfur content fertilizers
The weight ratio N: K2O Density (g/sm3) at temperature, °C Viscosity (cps) at temperature, °C
165 170 175 180 185 165 170 175 180 185
100: 0.0 1.450 1.448 1.446 1.437 5.71 5.34 5.02 4.83
1: 0.1 1.508 1.496 1.487 1.479 1.468 6.52 6.27 5.98 5.76 5.44
1: 0.2 1.515 1.502 1.496 1.488 1.477 8.16 7.95 7.65 7.35 6.91
1: 0.3 1.527 1.514 1.505 1.492 1.483 9.78 9.63 9.37 8.92 8.36
1: 0.4 1.543 1.530 1.511 1.503 1.490 11.34 11.28 11.06 10.51 9.82
1: 0.5 1.551 1.532 1.513 1.497 12.91 12.73 12.16 11.26
-* temperature of melt 170 °C
It should be noted that in all investigated ratios of N: K2O based on interaction of ammonium nitrate and potassium chloride exchange reaction occurs, in resulting are formed large crystals of potassium nitrate. Potassium nitrate crystals strongly clog hole injectors granulation tower. Therefore, in production granulation melt of potassium and ammonium nitrate we are recommended to carry out in drum granulator.
Conclusion
With the aim of eliminating the explosive properties of ammonium nitrate, new nitrogen and potassium-containing fertilizers have been obtained from
References:
it by introducing potassium chloride into its melt, produced by the Dehkanabad potash fertilizer plant. The compositions and properties of new fertilizers obtained in a wide range of changes in the mass ratio N: K2O (from 1: 0.1 to 1: 1) have been studied.
The most popular agricultural fertilizers are nitrogen-potassium fertilizers, in which the ratio N: K2O is 1: 0.5. Thus, at a ratio of N: K2O = 1: 0.5, using a 99.8% nylon smelting, we obtain a product with a content of 26.8% N and 13.4% K2O, the strength of its pellets is 7.53 MPa, which is much exceeds the strength of granules of pure ammonium nitrate (1.6 MPa).
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