NS-FERTILIZERS BASED ON AMMONIUM NITRATE MELT AND PHOSPHOGYPSUM

АННОТАЦИЯ

Для получения образцов азотносерных удобрений массовое соотношение АС : ФГ варьировалось от 100 : 0,5 до 100 : 20. Показано, что температура кристаллизации плава селитры понижается с 165 до 152^оС. В продуктах увеличение водорастворимой формы кальция с 0,06 до 2,86% свидетельствует о прохождении реакции взаимодействия нитрата аммония с дигидратом сульфата кальция с образованием нитрата кальция и сульфата аммония. При изучаемых соотношениях АС : ФГ = 100 : (0,5÷20) прочность гранул продукта повышается от 4,09 до 7,67 МПа. При этом слёживаемость продукта снижается с исходного 5,62 кг/см² до 1,83 кг/см² в продукте, почти в 3,1 раза. Гранулы гипсосодержащей АС растворяются в воде значительно медленнее, чем чистая АС. Фосфогипс в составе селитры способствует её конверсии, причем с увеличением количества добавки она возрастает.

ABSTRACT

To obtain samples of nitrogen-sulphuric fertilizers weight ratio of AN:PG was varied from 100 : 0.5 to 100 : 20. It was shown that crystallization temperature is reduced from 165 to 152 ^оС. In fact, the water soluble forms of calcium are increased from 0.06 до 2.86% due to interaction of ammonium nitrate and dehydrate of calcium sulphate resulting calcium nitrate and ammonium nitrate. When studying ratios of AN:PG = 100 : (0.5÷20) strength of granule is increased from 4.09 to 7.67 МPа while the packing of the product is rose from initial 5.62 kg/сm² to 1.83 kg/сm² that is 3.1 fold. Furthermore, the granules of the gypsum containing AN are dissolved considerably slowly in water than pure AN. There has been established the phosphogypsum in the AN facilitates conversion process while increase of its amount leads to grow latter.

Ключевые слова: Нитрат аммония, фосфогипс, температура кристаллизации, азотносерное удобрение, состав и свойства.

Keywords: Ammonium nitrate, phosphogypsum, crystallization temperature, nitrogen-sulphuric fertilizer, composition and properties.

Introduction. In 2015 the industry of Uzbekistan produced 942.72 thousand tonnes of nitrogen, 148.42 thousand tonnes of phosphoric and 143.24 thousand tonnes of potassium fertilizers recalculation by 100 %- of nutritious substances. Whereas, on a basis of 942.72 thousand tonnes of nitrogen fertilizers in form of 100% of nitrogen it was yielded that 1646.66 thousand tonnes of ammonium nitrate, 1646.66 thousand tonnes of urea and 192.65 thousand tonnes of ammonium sulphate.

Ammonium nitrate (AN) is multipurpose and agrichemical valuable nitrogen fertilizer. Moreover, it is used widely as an additional fertilizing for all agricultural crop and for all type of soils. Expenditure of AN (based on reactant) for increase of 1 ton of crop on average under grain is 80 kg, cotton is 141 kg, flax is 142 kg, sugar beet is 10.3 kg, sunflower is 157, potatoes is 13.8 and vegetables is 8.1 kg [1].

However, this fertilizer has grave lacks namely packing during the storage and high explosion hazard. Therefore, the present study is devoted for remedial action.

In order to remove saltpetre’s packing there are added such as sulphate, sulphate-phosphate, phosphate-sulfate-borate additives, caustic magnesite and so on in AN. In that case, the best effect is reached with using of magnesite [2]. Magnesite is used for two plant of Uzbekistan such as JSC “Maxam-Chirchik” and “Ferganaazot”. At JSC “Navoiazot” magnesite is used, but in form of natural mineral, brusite Mg(OH)₂. In [1] said about industrial production of AN with bentonite addition. In the USA and Canada granular AN is produced by “Herdler” company (the USA) providing usage of special forming of crystallization center of melt by addition called “Nuklo”. This type of addition is fine powder of bentonite clay with size no less than 0.04 mm (97%). Addition in amount of 2% (by weight) is fed in 99.85% solution of the AN melt before the granulation process. In addition, for unpackaged shipping approximately 0.3-0.8% of waste from wet-processing phosphoric acid production – phosphogypsum containing 1-6% of humidity and size of 10-100 micron is introduced in the saltpetre’s melt to reduce packing AN. The melt is mixed strongly and neutralization finally before feed into ball mill subsequent processing granule by naphthaline-sulfonate [3]. The worldwide as an additives reducing potential explosion hazard of AN used the following:

1) carbonate containing compounds natural and anthropogenic origin (chalk, calcium carbonate, dolomite);

2) potassium containing substances (potassium chloride and potassium sulphate);

3) substances, which content the same name cation-ammonium namely ammonium sulphate and ammonium orthos-polyphosphate;

4) other ballast substances that do not carry out payload while they determine mechanical dilution of AN as an impurity (gypsum, phosphogypsum and etc.) [4].

The additives from the 1^th group called calcium-ammonium-nitrate are used in the manufacture (CAN) [5, 6]. However, application of CAN is affective only for acid soils. Therefore, this type of the fertilizer is ineffective for alkaline and carbonate soils of Uzbekistan. Furthermore, powder CAN is explosive, as well.

The substance of the 2^nd group potassium chloride is used widely for production of potassium-ammonium nitrate. The latter in the foreign countries is produced rather considerable amount of 16-16.5% of N and 25-28% of K₂O. At the first time in 1999 in Russia the production of nitrogen-potassium fertilizer based on AN and potassium nitrate was implemented at JSC “Nevinnomisskiy Vneshtradeinvest”. The method of production and composition of the fertilizer was defended by patent [7].

Substances which of 3^rd group were used at JSC “Cherepovetskiy azot” (Russia), where in 2002 production of complex NP-fertilizer containing 32.3% of N and 5.2%  of Р₂О₅ was adjusted by introduction of liquid complex fertilizer composition of 11% of N and 37% of Р₂О₅ based on superphosphoric acid in AN solution [8, 9]. As this fertilizer can inhibit the thermo-decomposition process of AN and reduces its detonating properties. But superphosphoric acid in Uzbekistan is not produced. Besides, it is too expensive.

As regards, the additive of the 4^st group for AN where ballast substance is not carrying out payload, but it is as a mechanical impurity for AN. Nevertheless, in literature, there are some information about usage of phosphate, bentonite, gypsum and phosphogypsum that is waste from wet-processing phosphoric acid [10, 11]. The preparation of nonpacking and thermostable AN with usage of phosphogypsum as an addition is actual with point of view for processing the latter. At JSC “Ammofos-Maxam” amount of phosphogypsum constitutes 80 billion tonnes.

At the present research we have studied composition and property of AN with additive of the phosphogypsum waste from JSC “Ammofos-Maxam” and product of ammonium nitrate conversion.

Methods and materials. The phosphogypsum (PG) in the waste pile is in form of hydrate of calcium sulphate (СаSO₄ ∙ 2Н₂О) containing 18-20% of humidity. As a result, before we fed PG into AN, the latter had dried at 80-90°С then it was grained. The composition of dried phosphogypsum contented (weight, %): Р₂О_5total. 1.59; Р₂О_5acceptable 1.48; Р₂О_5water 1.12; СаО_total 37.47; СаО_acceptable 19.08; СаО_water 11.26; SO_3total 54.49; SO_3acceptable 27.4; SO_3water 16.88. In order to obtain modified AN ammonium nitrate (NA) brand “pure” containing 34.96% of N was used as the main component.

The experiments were carried out as follows:

NA was melted in metallic reactor placed on the electric stove.  Next during the mixing powdered PG was introduced in the melt in such amount that weight ratio of the AN melt was equal to 100 : (0.5÷20).

Gypsum-nitrate melt was held in 2-3 min at 170^оС then it was poured in the granulator which is metallic vessel with perforate bottom, where diameter of holes was 1.22 mm.

By pump from top of vessel pressure was created and melt sprayed from height 35 m on the polyethylene film lying on the ground. Hence, obtained granules were sieved on graininess. According to State standard 21560.2-82. particles with size of 2-3 mm are conducted measuring on granule strength. Then the products were grained and analysed by according to the procedure in [12].

Dimension of 10% water suspension solution of explored samples was carried out in lab ionomer I-130М with electrode system from electrical fishing ESL 63-07, EVL-1М3.1 and ТКА-7 with accurate within  0.05 unit of рН. Packing of fertilizer was determined according to express-method [13]. The condition of briquetting the following: the pressure of sample at cargo is 2.8 kg, the temperature is 50°С; duration of residence of cylindrical cassette in mould is 8 hours. The briquettes were tested on destruction by MIP-10-1. The packing of the samples of X (in to MPa) calculated by a formile below:

X = P / S

where, P – breaking force, Н (kgf); S – cross-sectional area of sample (сm²).

Determination of speed of the granule dissolution in water was carried out as follows. The fertilizer granule was sank down in glass with 100 ml of distilled water where its dissolution was observed and fixed by visually. The temperature was room and test was fivefold. In that case, granular ammonium nitrate brand “pure” was chosen as a sample in comparison with investigated samples.

In addition, it was exanimated that in what rate conversion of ammonium nitrate was conducted. The fact of the matter is that during the mixing melt of NA with PG depending on weight ratio of AN:PG in a varying degree the exchange decomposition reaction is taken place below:

2NH₄NO₃ + CaSO₄ · 2H₂O ↔ Ca(NO₃)₂ + (NH₄)₂SO₄ + 2H₂O

Definition of conversion level of NH₄NO₃ was carried out by the procedure [14]. Radiographical method was used for identification of NS-fertilizer’s phase composition. X-ray pattern of the samples was taken off at diffract meter DRON-3 at filtered out by cobalt emission. Voltage on the indicator was 30kV, anode current was through tube was 20 mA; rate of indicator rotation was 2 degree/min. X-ray pattern of the samples with representative value of interplanar space and intensity of a spectral line was identified by American file ASTM, as well as by radiographic determinant of Mikheev [15]. The results summarized in table and at figure 1 and 2.

Results and discussion. As the results present that addition of PG in NA melt reduces considerably crystallization temperature of the melt (fig.a). When studying ratios of АN : PG = 100 : (0.5÷20) the crystallization temperature of the saltpetre’s melt dropped from 165 ^оС (initial NH₄NO₃) to 152 ^оС, that is introduction of phosphogypsum into the melt of NH₄NO₃ leads to reduce its melt temperature at 13°С. Decrease of crystallization heat of AN in presence of PG can be explained that insoluble ingredients are crystallization center, which ease solidification process of the melt.

Table.

Composition and property of nitrogen-sulphuric fertilizers

As seen from the table that with increase in amount of phosphogypsum from 0.5 to 20 g in towards to 100 g of NH₄NO₃ leads to reduce nitrogen in the product from 34.81 to 29.04%, while the content of sulphur grows from 0.10 to 3.62%, аswell as СаО_total from 0.17 to 6.23%. it is necessary note that sulphur is in the composition of proteins and amino acids during the formation of the crop. According to physiological role in plant’s nutrition sulphur should be put at the third position after nitrogen and phosphorus [16]. By the way, calcium on significance for plant’s nutrition holds at the fifth position after nitrogen, phosphorus, potassium and sulphur. Even if, it is introduced in the soil as an acceptable form for plants it will give significantly crop addition [17]. Thus, it can be said that the composition of AN is enriched additionally by two macroelements such as sulphur and calcium. The growth of water soluble form of calcium in the samples of nitrogen-sulphuric fertilizers from 0.06 to 2.86% gives evidence on transmission mentioned above to the reaction between the NH₄NO₃ and CaSO₄ · 2H₂O with generation of Ca(NO₃)₂ and (NH₄)₂SO₄.

With increasing mass fraction of phosphogypsum in the melt of NH₄NO₃ from 100 : 0.5 to 100 : 20 the strength of granule grows from 4.09 to 7.67 МPа (fig. b).

In fact, that such strength of the granules can reduce porosity and inner specific surface of AN. So, reducing permeation of diesel fuel into the inside of granule it is said about decrease of detonating ability of AN.

The packing is one of the main figures of fertilizers ‘commodity. At fig. c there are presented the rate of packing of granular fertilizers depending upon weight ratio of AN:PG. in order to obtain the granule of nonpacking AN (no less than 34% of N) which possesse sufficient strength (4.09-4.56 МPа) while weight ratio of AN:PG should be met 100 : (0.5÷2.5). In that case, the packing of AN is 2.62-2.68 kg/сm² that exceeds 1.74-1.78 times in comparison with packing of standard AN with additive of 0.28% of MgO (4.67 kg/сm²). However, for samples made from when АN : PG = 100 : (5÷20) this value is in a range 1.83-2.26 kg/сm². To compare packing of the pure granular of NA without additives constitutes 5.62 kg/сm².

As shown from table data that the presence of phosphogypsum in the AN impacts on dissolution speed of latter’s granule. Due to increasing amount of PG in

Figure 1. Effect of weight ratio of AN:PG on crystallization temperature of ammonium nitrate (а), granule strength (b), granule packing (c), and conversion rate of NH₄NO₃ (d)

melt of NH₄NO₃ it is grown that the time of granule complete dissolution in water. Complete dissolution of the granule of pure NH₄NO₃ in water makes up on average 44.6 sec. while introduction of its composition of phosphogypsum in amount of 0.5 to 20 g slows down granule dissolution speed from 65.08 to 78.6 sec., that is the granules from gypsum AN is dissolved considerably slowly in the soil’s solution. Therefore, presence of phosphogypsum in the saltpetre promotes gradually release of nitrogen from granule. Addition of phosphogypsum in the melt of NH₄NO₃ reduces pH of 10% solution of the latter from 5.50 to 4.62 and these figures say on some losses of ammonia during the mixing initial substances. It requirements additional stage of gypsum-nitrate melt neutralization by ammonia before granulation. Yet, pH of condition AN samples with 0.5-2.5 g of PG meets requirements according to Standard state 2-85, presenting to nonpacking AN.

As seen from the fig. d that phosphogypsum leads to converse NH₄NO₃ while with increasing amount of additives this indicator grows monotonous. If the conversion rate of AN constitutes 0.21% when AN:PG = 100 : 0.5, that 100 : 3 will be 1.34%, 100 : 5 – 2.46%, 100 : 10 – 4.95%, and 100 : 20 – 13.19%.

In order to identity the process between ammonium nitrate and calcium sulphate in the composition of NS-fertilizer line-pattern of the samples were compared to x-ray pattern of the starting components.

Figure 2. Radiograph of nitrogen-sulphuric fertilizers obtained on a basis of the ammonium nitrate melt and phosphogypsum. АN : PG = 1-100 : 1.0; 2-100 : 5.0; 3-100 : 10; 4-100 : 15

Obtained results show that radiograph of pure NA using as an initial component has diffraction peaks such as 2.26; 2.73; 3.08; 3.96; 4.95 Å with corresponding intensity reflection 100; 76; 67; 45 and 44% respectively.

Radiograph of phosphogypsum (waste of wet-processing phosphoric acid from JSC “Ammofos-Maxam”) has diffraction maximum 4.30, 3.07, 7.69, 2.48; 3.81 respectively by intensity reflection such as 100; 63; 50; 20; 15%, which are specific for CaSO₄ · 2H₂O.

Line-patterns of NS-fertilizers based on mentioned above when ratios of AN : PG = 100 : (1.0; 5.0; 10; and 20) present that during the mixing AN with phosphogypsum with generation of well soluble calcium nitrate and ammonium sulphate testifying diffraction peaks 3.39; 3.40; 5.20; 5.21 Å and 4.33; 3.89; 4.39; 5.22; 5.31 Å respectively. On the radiograph it is observed that diffraction peaks of ammonium nitrate (2.26; 2.73; 3.08; 3.09; 3.95; 3.96 Å) and calcium sulphate (4.30; 3.07; 3.81; 3.0; 2.88; 2.48; 2.41; 2.08; 1.88; 1.44 Å), which is not reacted in the conversion process.

Hereby, these data have been converge well with results of chemical analyses on determination of the conversion rate of the initial components.

Conclusion. To sum up, that mixing melt of ammonium nitrate with powdered phosphogypsum subsequent prilling of gypsum-nitrate melt in the tower allows obtaining qualitative nitrogen-sulfuric fertilizers with improved physicochemical and low detonating properties. In that case, the composition of saltpetre has been enriched by such macroelements as phosphorus, sulphur and calcium promoting to raising the level of crop yield. The modified ammonium nitrate by phosphogypsum containing 34% of N on physicochemical properties exceeds considerably the industrial ammonium nitrate (State standard 2-85).

References:

1. Dobrovolskiy О.А., Lapidus А.S., Polyakov N.N. Quality of nitrogen fertilizers // Industry on mineral fertilizer production. Series. Nitrogen industry. – NIITEHIM. 1989. 56 p.
2. Оlevskiy V.М. Ammonium nitrate technology. Мoscow. Chemistry. 1978. 312 p.
3. Patent. USSR No 1502550. Cl. С05С 1/02. Method of reducing of ammonium nitrate packing / N.I.Orlov, V.M.Olevskiy, N.Е.Javaronkova, N.N.Polyakov, L.V.Кuznetsovа, E.Е.Аgafonova, А.F.Ilchenko, М.I.Кucha, V.К.Lyuskin. - B.I. 1989. No 31.
4. Levin B.V., Sokolov А.N. Issue and technical solution in complex fertilixer production based on ammonium nitrate // World of sulphur, N, P and К. – 2004. No 2. PP. 13-21.
5. Jmay L., Khristianova Е. Ammonium nitrate in Russia and the wide world. Modern condition and prospect // World of sulphur, N, P and К. – 2004. No 2. PP. 8-12.
6. Postnikov А.V. Production and application of calcium ammonium nitrate // Chemicalization of agriculture. – 1990. No 9. PP. 68-73.
7. Patent. No 2154620 Russia. Cl. С 05 С 1/02, С 05 D 1/00, С 05 G 1/06, С 05 D 5/00. Method of nitrogen-potassium fertilizer / V.F.Duhanin, А.I.Serebryakov – 20.08.2000. – B.I. – No 23.
8. Ilin V.А. Development of complex nitrogen-phosphoric fertilizer technology based on ammonium nitrate melt: PhD thesis in technique sciences, Ivanov State chemical engineering university, Ivanova. – 2006. – 17 p.
9. Ilin V.А., Rustambekov М.К., Акаеv О.P., Nenaydenko G.N. Investigation of complex nitrogen-phosphate fertilizer thermal stability // Issues on stabilization of fertility and yield in Vernevoje. – Мoscow. VNIIA. 2006. PP. 128-136.
10. Patent No 04527 РУз. Cl. 8С05G 1/00, С05В 7/00.С05С 1/00. Method of nitrogen-phosphate fertilizer / Sh.S.Namazov, B.B.Botirov, V.V.Pak, Sh.I.Salihov, А.М.Reymov, R.Yakubov, B.М.Beglov, R.К.Кurbaniyazov, N.N.Pirmanov, B.S.Zakirov. – 31.07.2012. –No 7.
11. Namazov Sh.S., Turdialiev U.М., Ortikova S.S., Reymov А.М., Beglov B.М. Preparation of thermostable ammonium nitrate based on its melt and bentonite from Uzbekistan // Chemical industry. - Saint-Petersburg. – 2016.  No 1. – С.1-14.
12. Methods of phosphate raw materials, phosphoric and complex fertilizers, feed phosphate analysis / М.М.Vinnik, L.N.Erbanova, P.М.Zaytsev and others. – Мoscow. Chemistry. 1975. 218 p.
13. Olevskiy V.М., Polyakov N.N. Results of industrial tests of ammonium nitrate on packing and friability // Abstract collection “Nitrogen industry”. // Мoscow. NIITEHIM. 1974. PP. 6-8.
14. Fridman S.D., Skum L.S. Solubility of potassium chloride in nitroammophos // Chemical industry. 1971. No 1. PP. 44-47.
15. Mikheev V.N. Radiographical determinant of minerals. II Volumetric. – Мoscow. Chemistry. 1957. V. 1. 868 p.
16. Milashenko N.Z. Ammonium sulfate – perspective form of nitrogen fertilizer // Agrichemical bulletin. 2004. No 2. PP. 3.
17. Kopeykina А.N. Importance of nutrition secondary elements for agriculture crop // Chemical industry the abroad. Мoscow. NIITEHIM. 1984. No 1. PP. 26-44.