Method for producing urea-sulphur fertilizers

Abstract

Field of use: agriculture. Problem of interest: to broaden the range of available granular compositions. Essence: a method for producing granular fertilizers containing urea and elemental sulphur, which includes spraying urea and sulphur in a liquid state onto a curtain of loose material inside a rotating drum having blades mounted on the inside surface thereof along the axis of rotation of the drum in one direction, wherein, prior to spraying, the molten sulphur and urea are emulsified in an ultrasonic field at a sound power of 500 W and a temperature of 150°С in the presence of a surfactant in the form of a lignosulphonate in an amount of 0.4-0.5% of the mass of sulphur, and the resulting emulsified melt is sprayed onto a moving curtain of material at an oncoming air flow velocity of 0.5-5 m / sec.

Description

[0001] METHOD OF PRODUCING UREA-SULFUR FERTILIZERS

[0002] Field of technology

[0003] This utility model relates to agriculture, namely to a method for producing granulated fertilizer containing urea and sulfur.

[0004] In the agricultural industry, urea is commonly used as a fertilizer to supply plants with nitrogen.

[0005] Many soils also require sulfur as a plant nutrient. However, elemental sulfur is not directly available to plants and cannot be used as a sufficient source of sulfur to produce sulfur-containing plant nutrients.

[0006] Among fertilizers containing urea and elemental sulfur, fertilizers containing sulfur in the form of a coating on the surface of urea granules are of special interest, since such a structure of fertilizer particles ensures reduced adhesion of granules, slow dissolution of urea in the soil and, accordingly, a reduction in its losses due to leaching from the soil.

[0007] State of the art

[0008] A method is known for producing granulated fertilizer containing urea and elemental sulfur, in which molten urea is mixed with molten sulfur in the presence of special additives (C6-C30 temperature-resistant fatty acids and their esters). Solid granules are then obtained from the resulting homogeneous phases. The resulting fertilizer granules contain sulfur distributed throughout the granule in a finely dispersed state. The size of sulfur particles is approximately 10-150 μm and depends on the concentration of additives [RU 2 296 730, C05C 9 / 00].

[0009] To obtain a homogenized melt of urea and sulfur, in which sulfur is dispersed in urea, the urea melt and the sulfur melt are passed through one or more devices for high-intensity mixing at a temperature above the melting temperatures. The pressure drop across said mixing device is at least 200 kPa.

[0010] Also known is a method for producing granulated fertilizer containing urea and elemental sulfur, which includes obtaining a homogenized melt of urea and sulfur and spraying it onto particles of a retort consisting of urea and sulfur in the volume of a rotating inclined drum. As a result, fertilizer granules are obtained in which sulfur is distributed throughout the volume of the granule in a finely dispersed state. The size of the sulfur particles is less than approximately 100 μm [US 4 330 319, C05C 9 / 00].

[0011] A method is known for producing a granulated fertilizer that contains urea and elemental sulfur by spraying urea and sulfur in a liquid state onto a curtain of bulk material in the volume of a rotating drum, wherein the spraying is carried out in a drum with blades mounted on its inner surface, the sulfur melt and the urea melt or solution are sprayed simultaneously by two separate non-intersecting torches of circular cross-section with diameters approximately equal to half the diameter of the circle formed by the free ends of the drum blades, wherein the spraying of the sulfur melt and the urea melt or solution is carried out along the axis of rotation of the drum in one direction. The invention makes it possible to ensure the distribution of sulfur in the volume of the fertilizer granule in a finely dispersed state without preliminary mixing of the components [RU 2 484 072 Cl, C05C 9 / 00].

[0012] The closest technical solution is a method for producing granulated urea coated with sulfur, which involves introducing urea granules into a rotating drum and simultaneously splashing molten sulfur onto the surface of the urea granules in the rotating drum. The temperature of the urea granules introduced into the drum is 20-60°C. The rotating drum is a drum with blades mounted on its inner surface. The rotation speed of the drum is 81-99% of the critical rotation speed. Splashing of molten sulfur is carried out in the direction of the axis of rotation of the drum [RU 2 436 754, C05C 9 / 00, B05D 1 / 02, B05D 7 / 00].

[0013] The main disadvantage of the prototype is the superficial nature of the coating of the resulting granules, which excludes the possibility of creating composite granules with a structure of embedded fragments in the volume of the granule.

[0014] Homogenized melt of urea and sulfur is a very unstable system. A stable emulsion of sulfur in urea cannot be obtained by conventional mixing of melts, since these two melts differ significantly in surface tension and density and thus tend to immediately separate into two separate phases. In this regard, the claimed method uses an emulsification stage with the introduction of a special additive, such as a surfactant (SAS), which affects the surface tension between the phases of urea and sulfur, which promotes the formation of a homogeneous mixed phase and prevents the resulting emulsion from separating during mixing of the two liquids.

[0015] According to the declared utility model, high-intensity ultrasound is used, which supplies a power of 500 W, necessary for liquid dispersion. In the dispersion zone, exploding cavitation bubbles cause the formation of intensely colliding waves in the surrounding liquid and lead to the formation of liquid jets with high speed. In order to strengthen the newly formed drops of the dispersed phase against merging, a surface-active substance (SAS) - lignosulfonate - is added to the emulsion for stabilization.

[0016] Lignosulfonate actually improves droplet destruction at constant energy density. In small concentrations, lignosulfonate has a noticeable biostimulating effect, so research is constantly ongoing to develop organic-mineral fertilizers based on it. Like any concentrated humic preparation, lignosulfonate in high concentrations is a powerful inhibitor. The molecular structure of lignosulfonate contains a mixture of humic compounds and an admixture of basic binders for their transformation into humic-like molecules.

[0017] The essence of the utility model

[0018] The problem solved by the declared utility model is to improve the technology and expand the range of manufactured granulated compositions for obtaining fertilizer containing sulfur and urea.

[0019] The set task is achieved by the fact that in the method for producing carbamide-sulfur compositions in a rotating drum, the carbamide and sulfur melts are preliminarily subjected to emulsification in the ultrasonic treatment mode with subsequent splashing of the emulsified melt onto a movable curtain formed by a packing system of the inner generatrix of the drum at a counter air flow speed within 0.5-5 m / sec. The packing system is made in the form of blades along the inner generatrix of the drum and has a reverse angle of inclination relative to the drum axis. Emulsification is carried out in the presence of surfactants, namely lignosulfonate, at a consumption of 0.4-0.5 mass parts relative to sulfur at the emulsification stage in an ultrasonic disperser.

[0020] The essence of the claimed technical solution is that preliminary emulsification of melts ensures a stable granulation mode and high strength of granules. A mode of layer-by-layer growth of fragmented granules is achieved, ensuring the evaporation of residual moisture from the surface upon contact with air, thus eliminating the encapsulation of moisture inside the granules.

[0021] The method can be implemented on any device similar to a drum granulator. More details about the granulator device and the implementation of the technical solution, with a technological scheme for obtaining granules are shown in Fig. 1 and 2.

[0022] List of figures:

[0023] Fig. 1 - drum granulator and longitudinal sectional view of the granulator.

[0024] Fig. 2 - flow chart for producing granulated fertilizer.

[0025] The proposed method is implemented in the granulator shown in Fig. 1 as follows. Prilled urea, fed through pipe 5, secured in fixed loading chamber 3, enters drum 1, equipped with transport nozzle 2. When the drum rotates, the blades of nozzle 2 lift and throw out product particles along a parabolic trajectory in the cross-section of the drum with the formation of a dense and uniform curtain of falling product particles. At the same time, molten sulfur and molten or urea solution are sprayed into the front part of drum 1 onto the formed curtain of falling particles by means of nozzles 7 and 8 along the drum axis in the direction of the unloading chamber with two non-intersecting torches of circular cross-section with diameters approximately equal to half the diameter of the circle formed by the free ends of the blades.During the movement of particles in the cross-section of the drum and along its axis, drops of molten sulfur and molten or urea solution enter and solidify on the granules. The granules gradually move to the opposite end of the drum 1, from where they enter the unloading chamber 4 and are removed from the apparatus as a finished product through the nozzle 10. Cooling air is supplied through the nozzle 9, which passes through the drum 1 countercurrent to the direction of movement of the hot granules and then through the loading chamber 3 and nozzle 6 goes for cleaning. After moving to the opposite end of the drum 1, the granules enter the classifier 13. Granules of the required size, having reached the end of the classifier, enter the unloading chamber 4 and are removed from the apparatus as a finished product through the nozzle 10.The fine fraction of the product passes in classifier 13 into the space between the inner 1 and outer 11 drums and is transported by means of screw 12 to the front part of outer drum 11 to receiving windows 14, through which the product enters inner drum 1 for further build-up in the falling curtain. Due to rolling in the lower part of drum 1, granules acquire an even smooth (without pimples) surface. To remove heat, cooling water with a temperature of 22^-28°C is provided (if necessary) in nozzle 17 of casing 15.

[0026] The concepts used to describe the implementation of the claimed method are:

[0027] Prilled (granulated) urea is one of the most effective nitrogen fertilizers, contains 46.2% nitrogen in amide form, which makes its use most profitable in agriculture as a fertilizer. Prilled urea granules have a size of 1-4 mm, which distinguishes it from other granulated types of urea with a free ammonia content of 0.03% (GOST 2081-2010. Urea. Technical conditions).

[0028] Lump sulfur is an allotropic crystalline substance of a light yellow hue. Density is 2.07 g / cm3, melting point is 113°C. It is practically insoluble in water, and when heated, it easily interacts with many substances, with the exception of nitrogen, iodine, gold, platinum, and inert gases. In a finely dispersed state, sulfur is oxidized by atmospheric oxygen to sulfurous and sulfuric acids (GOST 127-1-93. Technical sulfur. Specifications).

[0029] Bulk material used in the technology of obtaining fertilizer with sulfur and urea may be any known and widely used in agriculture solid bulk fertilizers that require additional saturation with sulfur and urea. At the same time, the applicant does not claim protection of objects included in the scope of the specified feature "bulk material".

[0030] Information confirming the possibility of implementing the utility model.

[0031] Emulsification was performed using melts of urea and sulfur in a weight ratio of 15:1. Lump sulfur is fed into sulfur melter 1 (description in Fig. 2 - process flow chart for obtaining granulated fertilizer). In the sulfur melter, due to the coils installed inside the apparatus and the supply of heating steam, the heating and melting of the lump sulfur occurs at a temperature of 120°C. A similar process occurs in melter 2 with prilled urea at a temperature of 140°C. The sulfur and urea melts obtained in melters 1 and 2 are fed by appropriate pumps 3 into the ultrasonic disperser UZD1-1.6 / 22 4 with an operating sound frequency of 22 kHz, a power of 500 W at a temperature of 150°C. Subsequently, intensive mixing of the media occurs in the disperser, producing an emulsion of sulfur in urea. The resulting emulsion is fed into a buffer tank, from where it is fed by a pump for spraying into the nozzle of the drum granulator 5.The emulsion of sulfur in urea is sprayed by a hydraulic nozzle onto a curtain of bulk material, which is formed by lifting and pouring blades installed inside the drum. The resulting emulsified melt is sprayed onto a moving curtain of material at a counter-air flow speed of 0.5 m / sec. When the emulsion hits the material particles, sulfur and urea crystallize on the surface of the material particle, which results in the strengthening of the particles and the formation of granules in the curtain. As the granules move along the length of the drum, the granules are cooled by sucking atmospheric air through the granulator. The granules from the granulator are unloaded onto an elevator and fed for classification into a two-sieve screen, where the flow is separated into three fractions. Granules smaller than 2 mm are unloaded onto a conveyor and returned to the head of the granulator as recycle for enlargement.The fraction of more than 5 mm is sent to the crusher and then also returned to granulation by means of a conveyor. The fraction of granules of 2-5 mm is the finished product (mixed fertilizer), which is sent for cooling to the fluidized bed cooler. In the fluidized bed cooler, the cooling of granules occurs due to direct contact of materials and atmospheric air supplied to the refrigerator by means of a fan.

[0032] The simulation resulted in hardened granules of high strength. The sulfur content in the finished product is 7.6%.

[0033] Example 2

[0034] The process is carried out similarly to example 1, with the difference that the emulsification was carried out using melts of urea and sulfur in a mass ratio of 10:1, and the resulting emulsified melt was sprayed onto a moving curtain of material at a counter-air flow speed of 0.5 m / sec.

[0035] As a result of the modeling, hardened granules of high strength were obtained. The sulfur content in the finished product is 8.5%.

[0036] Example 3

[0037] The process is carried out similarly to example 1, with the difference that the emulsification was carried out using melts of urea and sulfur in a mass ratio of 6:1, and the resulting emulsified melt was sprayed onto a moving curtain of material at a counter-air flow speed of 0.5 m / sec.

[0038] Granules with uniform distribution of urea in the granule volume were obtained. The sulfur content in the finished product is 10.2%.

[0039] Example 4 The process is carried out similarly to example 1, with the difference that lignosulfonate is additionally added to the disperser and melts of urea, sulfur and lignosulfonate are emulsified in mass ratios of 5:1:0.4, and the resulting emulsified melt is sprayed onto a moving curtain of material at a counter-air flow speed of 0.5 m / sec.

[0040] Further, the method produced granules with a uniform distribution of components in a narrower range of granulometric composition. The sulfur content in the finished product is 20.7%.

[0041] Example 5

[0042] The process is carried out similarly to examples 1 and 4, with the difference that the resulting emulsified melt is sprayed onto a moving curtain of material at a counter-air flow speed of 5 m / sec.

[0043] The method produced granules with a uniform distribution of components in a narrower range of granulometric composition. The sulfur content in the finished product is 23.1%.

[0044] Example 6

[0045] The process is carried out similarly to example 1, with the difference that the emulsification was carried out using melts of urea and sulfur and lignosulfonate in mass ratios of 5:1:0.5, and the resulting emulsified melt was sprayed onto a moving curtain of material at a counter-air flow speed of 0.5 m / sec.

[0046] The method produced granules with a uniform distribution of components in a narrower range of granulometric composition. The sulfur content in the finished product is 24.8%.

[0047] Example 7

[0048] The process is carried out similarly to examples 1 and 6, with the difference that the resulting emulsified melt is sprayed onto a moving curtain of material at a counter-air flow speed of 5 m / sec.

[0049] The method yielded granules with uniform distribution of components in a narrower range of granulometric composition. The sulfur content in the finished product was 25.7%. Microphotographic analysis of the fertilizer granules obtained in Examples 4-7, containing urea, sulfur and lignosulfonate, showed that the sulfur particles were less than 100 μm in size and distributed throughout the entire volume of the fertilizer granule.

[0050] Thus, when implementing the claimed technical solution, indicated in examples 4-7, it is possible to produce granulated composites with a wide range of variation in component ratios, which is in demand at the current level of agricultural development for the production of fertilizers.

Claims

FORMULA A method for producing a granulated fertilizer containing urea and elemental sulfur, which includes spraying urea and sulfur in a liquid state onto a curtain of bulk material in the volume of a rotating drum with blades mounted on its inner surface along the axis of rotation of the drum in one direction, characterized in that, before spraying, the molten sulfur and urea are emulsified in an ultrasonic field at a sound power of 500 W at a temperature of 150°C in the presence of a surfactant - lignosulfonate in an amount of 0.4-0.5% of the weight of sulfur, and the resulting emulsified melt is sprayed onto a moving curtain of bulk material at a counter-air flow speed within the range of 0.5-5 m / sec. 9

Images