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Yulbarsova Mashkhurakhon, Junior scientific researcher, Institute of General and Inorganic Chemistry of Academy of Sciences Republic of Uzbekistan E-mail: [email protected] Tadjiyev Sayfitdin, doctor, of Technical Sciences, Senior Research Scientist, Institute of General and Inorganic Chemistry of Academy of Sciences Republic of Uzbekistan,
Uzbekistan, Tashkent, E-mail: [email protected]
A NEW KIND OF FERTILIZER CARBONITROPHOS OF CENTRAL KYZYLKUM PHOSPHATES AND UREA
Abstract: This article presents the results of a study on the production of carbonitrophos slurry based on the decomposition products of phosphorites from Central Kyzylkum with incomplete norm of nitric acid and urea. The chemical composition and rheological properties of the pulp depending on the amount ofwater, the mass ratio of calcium nitrate: urea and temperature. It is shown that with the increase in the amount of urea and temperature, the density and viscosity of the urea pulp is significantly reduced. Rheological characteristics meet the requirements for the current technology of nitrocalciumphosphate production fertilizer at the JSC "Samarkandkimyo".
Keywords: phosphorite powder, nitric acid, decomposition, urea, carbonitrophos, nitrophos, density, viscosity.
Over the past 10-20 years, the global fertilizer market has seen a high demand for various types of complex NP, PK and NPK fertilizers. This situation is caused, first of all, by their high agrochemi-cal value, as fertilizers can be used under the soil at the same time two or three of the most valuable nutrients - nitrogen, phosphorus and potassium. In addition, the continuous growth of the population on the Earth leads to high demand for agricultural products. In this case, triple fertilizers make it possible to solve the problem of food security of each country on the planet.
In the literature it is known that products having two nutrient components - nitrogen and phosphorus is adopted, called nitroammophos, carboammo-phos and nitrophos, and when the three nitroam-
mophospotassium, carboammophospotassium and nitrophospotassium. All of them are products of sulfuric acid and nitric acid processing of natural phosphates. The latter method has become widespread, nitric acid has a two - way advantage - is the activity of the hydrogen ion of the acid, revealing the phosphate mineral and nitrogen remains in the composition of the product as a nutrient component. It should be noted that acid decomposition requires high-quality phosphate raw materials.
Currently, phosphorites of Central Kyzylkum are the main raw material for Uzbekistan plants producing phosphoric fertilizers. Phosphorites of the Central Kyzylkum are characterized by low content of phosphorus (16.2% P2O5), high content of carbonates (17.7% CO2) and high value
of calcium module (CaO: P2O5 = 2.85). This raw material is practically unsuitable for sulfuric acid extraction or for nitric acid decomposition. But the phosphorites of the Central Kyzylkum quite reactive even at low amounts of acidic reagent, which show the work [1]. The decomposition products of low-grade phosphorites of the Central Kyzylkum at low rates of acid reagent are also detailed in [2-4]. The authors showed the principal possibility of obtaining nitrocalciumphosphate fertilizer by decomposition of Kyzylkum phosphorite in incomplete norm of nitric acid. This fertilizer is produced at JSC "Samarkandkimyo". The main disadvantages of the technology are the energy intensity of the process and the hygroscopicity of the resulting product due to the content of a sufficient amount of calcium nitrate (more than 2%). In case, it is necessary to find solutions to reduce energy consumption and improve the properties of the target product. One of such solution to the problem can be dealt with urea additives. The reason for this was the work [5], where the effect of urea on calcium nitrate is studied in detail. The author studies the resulting compound Ca(NO3)2 • CO(NH2)2 • 3H2O, Ca(NO3)2 • • 4CO(NH2). Methods of thermal, IR - spectroscopic and X - ray phase analysis carried out identification of the obtained compounds.
The results of the research have led to the carrying out of this work to improve the quality nitrocalciumphosphate pulp, the intermediate product produced at JSC "Samarkandkimyo".
To do this, the objective of the study was to study the rheological properties of nitrocalciumphosphate pulp with addition of urea.
As object of research was used phosphorite flour of the Central Kyzylkum (wt.%): P2O5-16.38, CaO - 45.93, CO2 - 18, 15, 57% nitric acid and urea with a content of 46% N. the Stoichiometric rate of nitric acid was calculated on the decomposition of phosphate and carbonate minerals in the phosphorite with the formation of monocalcium phosphate and calcium nitrate. Normal nitric acid was taking
40% from stoichiometry considerations the industrial condition ofJSC "Samarkandkimyo".
Decomposition ofphosphate rock with nitric acid was carried out at a temperature of30-40 °C and continuous stirring in a glass reactor for 25-30 min. Calculated amount of nitric acid was applied to phosphate rock for 5-10 min. in the reactor, there was intense interaction of the acid with the components of the highly-phosphate. After decomposition, the calculated amount of urea (calcium nitrate: urea= 1: 1.0 - 4.5) and water (15-25% of the total pulp mass) were added to the resulting nitrogen - phosphoric pulp to obtain the flowing carbonitrophos mass.
The content of all forms of P2O5 - total, digestible (in 2% citric acid), water soluble) in the feedstock and the resulting products was determined by the photocolorimetric method in the form of a yellow phosphoramidite molybdenum complex on the photocolorimeter KFK-3 (1 = 440 nm) [5]. The determination of the content of all forms of calcium was carried out by the volumetric complexonomet-ric method of trilon B titration in the presence of fluorexone indicator [6]. The total CO2 content was determined by dissolution of samples in hydrochloric acid (HCl = 10%). The amount of CO2 is calculated from the volume difference between the total carbon dioxide mixture and the air volume remaining after adsorption of carbon dioxide by 40% potassium hydroxide solution [7]. The pulp density was determined by a universal pycnometer with capillary tube in the socket. The values were taken as the arithmetic mean of three measurements. The relative error was 0,02%. Viscosity was determined on a capillary viscometer VTL - 2 (error not higher than 2% relative) [8]. Measure the pH of solutions and suspensions was performed on pH meter METTLER TOLEDO. The density and viscosity of the pulp with the addition of urea are determined in the temperature range 30-80 °C.
The results of the research (table. 1) indicate that nitrocalciumphosphate pulp without the addition of urea has a low value of the digestible form
P2O5 in the range from 45.36 to 44.36%; total form P2O5 9.01 - 7.84% varies depending on the amount of water 15 - 25%. While urea additives at the ratio of calcium nitrate: urea = 1:1-1: 4.5 leads to a significant increase in the digestible forms of P2O5 and CaO 2% citric acid on average from 1.05 to 1.32 times, but a decrease in the overall shape of P2O5 from 1.05 to 1.30 times. Under the same conditions, there is an increase in total nitrogen on average from 1.20 to 2.18 times. Although the addition of water has little effect on the composition of intermediates, but significantly reduces the content of all components of the nutrient components in the composition of carbonitrophos pulp. For example, with the
CaO ,,,. However, when water is added 20 and
watersoluble '
25% by weight of pulp and at the same ratio of calcium nitrate: urea pulp contains (mass.%): 7.44 - 6.99
^total^ 7.72 7.25 P2O5tota^ 3.63 3.37 P2O5assimilable;
21.64 - 20.33 CaO ,, 10.37 - 9.64 CaO , w . It
total' assimilable
should also be mentioned water forms P2O5 and Cao, which are contained in small quantities in the range from 0.18 - 0.16 and 8.14 - 7.03%, depending on the amount of added water from 15 to 25%, respectively. In addition, the content of both water-soluble nitrate and slow-acting forms of nitrogen in the pulp contribute to the uniform growth and development of plants during the growing season. In any case, the composition of the pulp is char-addition ofwater 15% by weight and a weight ratio of acterized by the presence of 8.24-11.98% P2O5, calcium nitrate: urea = 1: 1 carbonitrophos pulp has 16.31-20.48% CaO, 7.04-15.42%, as well as the
content of total nitrogen 3.52-2.80% in nitrate and 3.52-12.62% in amide form.
a composition (wt.%): 7.95 N^; 8.24 pOal, 3.92
PO ; 23.12 CaOtt, 11.20 CaO bl. 8.14
2 5assimilable/ tor assimilable
Table 1.- Changes in the chemical composition carbonitrophos pulp depending on the amount of water and the ratio of Ca(NO3)2: CO(NH2)2, (%)
Ca(NO3^: CO(NH2)2 in pulp N PO, CaO H2O CO2 рн
total nitrate amide total assimilable water-soluble total assimilable water-soluble
1 2 3 4 5 6 7 8 9 10 11 12 13
25% HO
1: 0 3.78 3.78 — 7.84 3.48 0.16 21.98 9.95 7.56 40.05 5.21 4.66
1: 1 6.99 3.49 3.49 7.25 3.37 0.16 20.33 9.64 7.03 37.05 4.82 4.77
1: 1.5 8.42 3.37 5.05 6.99 3.40 0.16 19.60 9.71 6.99 35.71 4.65 4.82
1: 2 9.75 3.25 6.50 6.75 3.43 0.17 18.92 9.78 6.96 34.47 4.48 4.88
1: 2.5 11.00 3.14 7.86 6.52 3.45 0.17 18.28 9.85 6.93 33.31 4.33 4.93
1: 3 12.16 3.04 9.12 6.31 3.48 0.18 17.68 9.91 6.90 32.22 4.19 4.98
1: 3.5 13.25 2.94 10.30 6.11 3.50 0.18 17.13 9.97 6.87 31.20 4.06 5.03
1: 4 14.27 2.85 11.42 5.92 3.52 0.19 16.60 10.02 6.85 30.25 3.94 5.09
1: 4.5 15.23 2.77 12.46 5.75 3.54 0.19 16.11 10.07 6.83 29.35 3.82 5.14
20% HO
1: 0 4.04 4.04 — 8.38 3.76 0.17 23.51 10.76 8.08 35.87 5.57 4.36
1: 1 7.44 3.72 3.72 7.72 3.63 0.17 21.64 10.37 7.55 33.01 5.13 4.47
1: 1.5 8.94 3.58 5.36 7.42 3.65 0.18 20.81 10.42 7.49 31.74 4.93 4.52
1: 2 10.33 3.44 6.89 7.15 3.67 0.18 20.04 10.47 7.44 30.57 4.75 4.58
1: 2.5 11.63 3.32 8.31 6.89 3.69 0.19 19.33 10.52 7.39 29.48 4.58 4.63
1: 3 12.83 3.21 9.62 6.66 3.71 0.19 18.66 10.56 7.35 28.47 4.42 4.67
1: 3.5 13.96 3.10 10.85 6.43 3.72 0.20 18.04 10.60 7.31 27.53 4.28 4.72
1 2 3 4 5 6 7 8 9 10 11 12 13
1: 4 15.01 3.00 12.01 6.23 3.74 0.20 17.46 10.64 7.27 26.64 4.14 4.78
1: 4.5 15.99 2.91 13.09 6.03 3.75 0.21 16.92 10.67 7.23 25.81 4.01 4.83
15% HO
1: 0 4.34 4.34 - 9.01 4.09 0.18 25.27 11.69 8.68 31.06 5.99 4.06
1: 1 7.95 3.97 3.97 8.24 3.92 0.18 23.12 11.20 8.14 28.42 5.48 4.17
1: 1.5 9.53 3.81 5.72 7.91 3.93 0.19 22.17 11.22 8.06 27.26 5.26 4.21
1: 2 10.99 3.66 7.32 7.60 3.94 0.20 21.30 11.25 7.98 26.19 5.05 4.27
1: 2.5 12.33 3.52 8.81 7.31 3.95 0.20 20.50 11.27 7.92 25.20 4.86 4.32
1: 3 13.58 3.40 10.19 7.04 3.96 0.21 19.75 11.29 7.85 24.28 4.68 4.37
1: 3.5 14.74 3.28 11.47 6.80 3.97 0.21 19.06 11.31 7.79 23.43 4.52 4.42
1: 4 15.83 3.17 12.66 6.57 3.98 0.22 18.41 11.33 7.74 22.64 4.37 4.47
1: 4.5 16.84 3.06 13.78 6.35 3.99 0.22 17.81 11.34 7.69 21.89 4.22 4.52
Also, the obtained results show that the addition of water in the amount of 25%, 20% and 15% does not significantly affect the pH of the pulp, but with an increase in the additive of urea, this value increases in the range of4.66 - 5.14, 4.36 - 4.83 and 4.06 - 4.52 respectively.
Further, to assess the process ability of pulp rheological properties - density and viscosity were determined (table. 2). Indicators of rheo-logical properties show that with a decrease in the water additive from 25 to 15% leads to an increase in both the density and viscosity of the carbonitrophos pulp at the same mass ratio Ca(NO3)2 : CO(NH2)2 and temperature. For example, at a ratio of Ca(NO3)2: CO(NH2)2 = 1: 1 and a temperature of 40 °C, the density and viscosity increase from 1.5117 to 1.6203 g/cm2 and from 13.77 to 27.48 mm2/s. Whereas, with the addition of water in an amount of 25%, but with an increase in Ca(NO3)2: CO(NH2)2
from 1 : 1 to 1 : 4.5 these figures are significantly reduced from 1.5117 to 1.4116 g/cm2 and from 13.77 to 10.55 mm2/s at 40 °C.
This phenomenon is explained by the chemical substitution of calcium nitrate tetrahydrate water for urea according to the equation:
Ca(NO3)2 • 4H2O + nCO(NH2)2 = Ca(NO3)2 • • 4 - n CO(NH2)2 + n H2O
The increase of temperature from 30 to 80 °C to give the density reduction in the range from
I.5938-1.4937 g/cm2 to 0.8527 - 0.7218 g/cm2, and viscosity of 15.26 - 11.85 mm2/s to
II.96 - 4 22 mm2/s, respectively. Whereas, with the addition of20% water and an increase in the mass fraction ofurea in the mass ratio Ca(NO3)2 : CO(NH2)2 and temperatures from 30 to 80 °C, the density and viscosity decreases from 1.6611 to 0.7780 g/cm2 and the viscosity from 22.80 to 8.83 mm2/s, i.e. decreases 2.14 times, and the viscosity of 2.58 times.
Table 2.- The rheological properties carbonitrophos pulp depending on the requirement of water, the ratio of Ca(NO3)2: CO(NH2)2 and temperature
Ca(NO3)2: CO(NH2)2 in pulp 25% HO 20% HO 15% HO
H, mm2/s p, g/cm2 H, mm2/s p, g/cm2 H, mm2/s ^ g/cm2
1 2 3 4 5 6 7
Temperature, 30 °C
1: 0 15.26 1.5938 22.80 1.6611 30.34 1.7284
1: 1 14.44 1.5628 22.01 1.6173 29.58 1.6718
1: 1.5 14.07 1.5454 21.64 1.5980 29.20 1.6506
1 2 3 4 5 6 7
1: 2 13.70 1.5333 21.26 1.5880 28.82 1.6427
1: 2.5 13.33 1.5304 20.89 1.5760 28.44 1.6216
1: 3 12.96 1.5293 20.51 1.5712 28.06 1.6130
1: 3.5 12.59 1.5143 20.14 1.5529 27.68 1.5914
1: 4 12.22 1.5019 19.76 1.5418 27.30 1.5816
1: 4.5 11.85 1.4937 19.39 1.5282 26.92 1.5627
Temperature. 40 °C
1: 0 14.69 1.5443 21.55 1.5974 28.40 1.6504
1: 1 13.77 1.5117 20.63 1.5660 27.48 1.6203
1: 1.5 13.31 1.4930 20.17 1.5626 27.02 1.6321
1: 2 12.85 1.4846 19.71 1.5381 26.56 1.5916
1: 2.5 12.39 1.4653 19.25 1.5179 26.10 1.5704
1: 3 11.93 1.4523 18.79 1.5081 25.64 1.5639
1: 3.5 11.47 1.4329 18.33 1.4879 25.18 1.5428
1: 4 11.01 1.4240 17.87 1.4780 24.72 1.5320
1: 4.5 10.55 1.4116 17.41 1.4612 24.26 1.5107
Temperature. 50 °C
1: 0 14.20 1.4147 20.43 1.4677 26.66 1.5206
1: 1 13.06 1.3821 19.29 1.4374 25.52 1.4927
1: 1.5 12.49 1.3632 18.72 1.4185 24.95 1.4738
1: 2 11.92 1.3502 18.15 1.4060 24.38 1.4617
1: 2.5 11.27 1.3343 17.54 1.3874 23.81 1.4405
1: 3 10.75 1.3212 17.00 1.3760 23.24 1.4307
1: 3.5 10.23 1.3106 16.45 1.3628 22.67 1.4150
1: 4 9.71 1.2943 15.91 1.3495 22.10 1.4047
1: 4.5 9.19 1.2822 15.36 1.3325 21.53 1.3828
Temperature. 60 °C
1: 0 13.76 1.2826 19.31 1.3366 24.86 1.3905
1: 1 12.42 1.2518 17.97 1.3073 23.52 1.3628
1: 1.5 11.75 1.2327 17.30 1.2878 22.85 1.3428
1: 2 11.08 1.2245 16.63 1.2775 22.18 1.3305
1: 2.5 10.40 1.2134 15.96 1.2636 21.51 1.3138
1: 3 9.74 1.1943 15.29 1.2574 20.84 1.3204
1: 3.5 9.07 1.1728 14.62 1.2267 20.17 1.2805
1: 4 8.40 1.1616 13.95 1.2172 19.50 1.2728
1: 4.5 7.73 1.1442 13.28 1.1985 18.83 1.2527
Temperature. 70 °C
1: 0 12.98 1.0754 18.02 1.1291 23.06 1.1828
1: 1 11.44 1.0415 16.48 1.0970 21.52 1.1525
1: 1.5 10.67 1.0237 15.71 1.0771 20.75 1.1304
1: 2 9.90 1.0123 14.94 1.0662 19.98 1.1201
1: 2.5 8.98 0.9921 14.10 1.0463 19.21 1.1004
1 2 3 4 5 6 7
1: 3 8.26 0.9831 13.35 1.0369 18.44 1.0907
1: 3.5 7.54 0.9616 12.61 1.0159 17.67 1.0702
1: 4 6.82 0.9536 11.86 1.0074 16.90 1.0611
1: 4.5 6.10 0.9345 11.12 0.9889 16.13 1.0432
Temperature. 80 °C
1: 0 11.96 0.8527 16.57 0.9066 21.18 0.9605
1: 1 10.24 0.8318 14.85 0.8878 19.46 0.9437
1: 1.5 9.38 0.8125 13.99 0.8670 18.60 0.9214
1: 2 8.52 0.8009 13.13 0.8569 17.74 0.9128
1: 2.5 7.66 0.7805 12.27 0.8369 16.88 0.8932
1: 3 6.80 0.7707 11.41 0.8262 16.02 0.8817
1: 3.5 5.94 0.7528 10.55 0.8067 15.16 0.8605
1: 4 5.08 0.7447 9.69 0.7978 14.30 0.8508
1: 4,5 4,22 0,7218 8,83 0,7780 13,44 0,8342
In the production of nitrophos at JSC "Samar-kandkimyo" pulp has a density of 1.4 - 1.5 g/cm3 and viscosity of15 - 16 mm2/s. In this regard, these indicators were the basis for selection of the rheo-logical properties of the slurries carbonitrophos. From these tables it follows that the optimal ratio is calcium nitrate: urea is 1 : 4 and the amount ofwater 15% of the total pulp mass.
At the same time, the urea-containing pulp at low amounts of water (15%) is movable in comparison with the nirocalciumphosphate pulp. If you keep in mind the fact that in the production of nitrocalci-umphosphate to the slurry is added 25% water of the total weight, in this case, the optimal can be considered the addition of water 15%.
Based on this mass ratio Ca(NO3)2: CO(NH2)2 is equal to 1 : 4 water additive 15% of pulp weight can be considered a rational choice. In this case, the
density of the pulp with an increase in temperature from 30 to 80 °C varies in the range 1,5816-0,8508 g/cm3 and 27.30 - 14.30 mm2/s. While carbonni-trogen pulp has a composition (wt.%): 12,66 N ;
6.57 P2O5total; 3.98 Р2O5assimilable, 0.22 P2O5watersoluble;
18.41 CaO _,, 11.33 CaO ,,; 7.74 CaO ,,,
totar assimilable' watersoluble
and 22.64 H2O.
Thus, with the addition of the urea the system is diluted, and the slurry becomes fluid, which contributes readily available for transfer from one model to another, that is, provide transportability carbonitrophos slurries. Reduction of water additive and enrichment of the product with even more amide nitrogen leads to improvement of technical and economic indicators of the product per unit of specific consumption of both raw and heat- and -power resources.
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