Composite fertilizer containing lignite-carbohydrate-urea, process for its production and agricultural application thereof

Abstract

The present invention relates to a slow-release composite fertilizer containing lignite- carbohydrate-urea and a process for its production. The invention is based on the phenomenon that different sugar molecules are able to create deep eutectic with urea. According to the invention, they mix the liquid eutectic with lignite, whose porous structure enables the eutectic to flow into the pores, and to set by smart sorption. Thereby urea is gradually released in the soil, avoiding the ion shock of plants and preventing the leaching and decomposition due to rain.

Description

[0001] COMPOSITE FERTILIZER CONTAINING LIGNITE-CARBOHYDRATE-UREA, PROCESS FOR ITS PRODUCTION AND AGRICULTURAL APPLICATION THEREOF

[0002] The present invention relates to a slow-release composite fertilizer containing lignitecarb ohydrate-urea and a process for its production. The invention is based on the phenomenon that different sugar molecules are able to create deep eutectic with urea. According to the invention, they mix the liquid eutectic with lignite, whose porous structure enables the eutectic to flow into the pores, and to set by smart sorption. Thereby urea is gradually released in the soil, avoiding the ion shock of plants and preventing the leaching and decomposition due to rain.

[0003] DESCRIPTION OF THE PRIOR ART

[0004] Since the first decades of the last century, agriculture applies fertilizers in large quantities. In so doing, several tons of chemical products are placed in cultivated areas. The primary consideration of the usage of chemical compounds was to meet the nutrient-needs of the intense agricultural production. However, the applied large amounts of chemicals negatively influenced the wildlife, degraded the soil quality, significantly increased the greenhouse gas emissions and polluted the groundwater. At the same time, these negative effects are not occurred due to chemicals, rather because plants could not absorb the large quantities of applied nutrients. The reason of applying excessive amounts lies in that only ca. 40% of the applied fertilizer is available for the plant, the rest of cannot be sufficiently mobilized, does not reach roots. Consequently, approximately 60% of the chemical is wasted, while it has a harmful effect on the environment. For example, the nitrogen from the fertilizer in one hand migrates to the deeper layers of the soil and causes the nitrification of groundwaters, on the other hand, it goes to the atmosphere in the form of N2O, which has a 134 times stronger greenhouse effect than the carbon dioxide. In addition, during applying fertilizer in the plant’s point of view, ion shock takes place, which means for it a stress source. As a solution for the existing situation, they developed SRF (slow-release fertilizer) as well as CRF (controlled release fertilizer) fertilizers. The first one means a slowed-down release in the soil, and the second one means a controlled release, which happens if certain environmental conditions are met. In arable farming agriculture uses urea for decades. This nutrient - though it is an undoubtedly really important nitrogen source for the plants - it causes the acidification of the soil in the long term. In the case of urea, they attempted to treat the problem biologically, that is, they applied such an inhibitor to the soil which prevents working the enzymes of ureadegrading bacteria, so even though urea is in the soil, yet it does not degrade, because they inhibited the natural biological way (M. R. Banerjee, D. L. Burton, and C. A. Grant, Canadian Journal Of Soil Science, 97(2), p 256-263, 1999). The limitations of the existing solutions in the case of SRF and CRF technologies become evident in that urea is applied to the soil enclosed in capsules, which capsule forms a sealing layer around the active ingredient and opens up because of the soil moisture or rain and the nutrient gets outside, however, this is practically not slowing down, but rather a postponement of the problem. The urea is just as suddenly released, only with a time delay. It causes ion shock as well, the plant still cannot absorb the high quantities, and the fertilizer similarly washed into the lower layers of the soil, thus polluting the environment. The problem is not actually solved, only delayed (Weiyi Liu, Sally Price, Grant Bennett, Thomas.R. Maxwell, Cunyi Zhao, Greg Walker, Craig Bunt, Journal of Controlled Release, Volume 348, August 2022, p. 612-630). The description of U.S. Patent Publication No. US4517007A provides that it is a real slowdown during chemical inhibition of the enzyme activity. The disadvantage, however, is that the urea in the soil is freely accessible for waters, therefore this solution does not solve the problem of pollution. The urea is water-soluble, which is delivered to the lower layers of soil by the rain, where there are no roots anymore, thus appearing as a pollutant in the groundwaters. The current carries it to places where the inhibitors cannot reach, then the soil bacteria present there degrade the urea, while ammonia forms. Ultimately, greenhouse gases are released.

[0005] Imperato et al., in their publication, discuss the preparation of sugar-, urea- and inorganic salt-based low-melting mixtures, which serve as a green solvent for the Diels-Alder-reactions. They identified more stable eutectic mixtures, which melts between 65-77 °C temperatures. Based on the examples, the method can be generally applied for preparing sugar-and urea-based eutectic mixtures.

[0006] Zdanowicz discusses in his article the preparation and the characterization of deep eutectic solvents made from urea, polyols (e.g.: glycerol, sorbitol), and monosaccharides (e.g.: glucose, fructose), which he used to treat potato starch. Due to using urea as a fertilizer, modified with urea-based mixtures, biologically degradable starchy materials can be applied in the agriculture. Rashid et al. in their publication report the preparation of a lignite-based, slow-release fertilizer, during which process they impregnate urea to the surface of the calcined lignite. The sorption ability of the lignite was able to bind urea, then they pelleted the obtained material with polyvinyl alcohol and starch, which worked as a binding material to increase stability. The structure of the fertilizer thus created ensured to release nitrogen gradually, in more than 70 days, thereby preventing fast mineralization and significant nitrogen loss.

[0007] As disclosed in international publication WO2014091279A1, a process about preparing a granular, urea-based, controlled nitrogen-releasing fertilizer is described, in which biochar is used as a renewable carrier. The biochar produced by slow pyrolysis of biomass is impregnated with urea (or another nitrogen source) in the liquid phase - typically at 150 °C. During the impregnation, the solvent is usually a polar solvent, which is separated at the end of the process by filtration from the impregnated biochar particles. The particles are then covered with a biologically degradable polymer.

[0008] US Patent Publication No. US4013440A relates to the preparation of such nitrogencontaining composites, which can be applied as fertilizers as well as soil amendments. During the process coal dissolved in water is treated with urea, which then goes through oxidation, then alkaline treatment, removing water lastly to get nitrogen-rich composite, which ensures slow nitrogen release.

[0009] Li et al. in their paper reports a nitrogen-rich, coal-based fertilizer, which they made by using hydrogen peroxide and urea, and which is characterized by slow nitrogen release. During the preparation process, they sifted the coal, added hydrogen peroxide to it, then impregnated with aqueous urea solution in addition to ultrasonic mixing.

[0010] The summary of the Chinese patent publication CN1580005A is the preparation of a humic acid-urea-based fertilizer, which mixes inorganic urea and lignite, with bentonite as well as fluorite powder, and optionally with other microelements such as zinc, copper, calcium etc. Compared to traditional fertilizers this mixture improves the physicochemical properties of the soil, regulates the acid-base equilibrium, stimulates the activity of the microorganisms and enzymes, loosens the soil, improves the water and nutrient retention, and increases plant resistance and crop yield.

[0011] Chinese Patent CN102584498B provides a preparation process for humic acidcontaining urea. The humic acid is extracted from coal or lignite with dilutes alkaline solution, then this is combinated with the urea preparation process to make humic acid-containing urea, which is able to inhibit the activity of the urease enzyme in the soil, to decrease the loss of nitrogen fertilizers.

[0012] THE TECHNICAL PROBLEM TO BE SOLVED BY THE INVENTION

[0013] By eliminating the deficiencies of the previously disclosed and known processes, the objective of our invention was to prepare a deep-eutectic composite, which is capable of true slow active ingredient release, structurally contains the nutrient, and which is not influence the urease enzymes’ activity of the natural bacteria, i.e., does not interfere with biological processes on an elemental scale. Furthermore, our goals were to avoid ion shock experienced by plants and to release soil-conditioner composite into arable lands.

[0014] THE INSIGHT UNDERLYING THE INVENTION

[0015] Different sugar molecules are able to form deep eutectic with urea or other nitrogencontaining fertilizer, which makes a stable chemical structural entity and the composite preparation energy efficient. The novelty of the process according to the invention lies in the application of this deep eutectics, whenever the melting point of the mixture forming in the certain composition ranges is below than the melting temperatures of each component. This deep eutectic mixture strongly bonds to the lignite’s surface and thus inhibits the nutrient release, giving space for the slow release. Furthermore, because of the ingredients, soilconditioner composite releases into arable lands upon application of the composition according to the invention.

[0016] We proved the existence of the formed new bond with computational chemistry in addition to thermogravimetric measurements and also laboratory sorption and desorption experiments. This supports that deep-eutectic composite created with smart-sorption increases the nutrient utilization from 40% to 80-90%, see Figure 1.

[0017] Our inventive insight further relates to the production process according to which it is not necessary to melt the components, but rather by exploiting the thermal effect emerged from the applied mechanical pressing force on the mixture the components warm up, induced phase transition occurs, and new bonds form on the surface of the coal carrier. The lower melting point of the deep eutectic and the applied unheated melting makes the composite preparation energy efficient.

[0018] FIGURES

[0019] Figure 1: Ammonia concentration (ppm) in the function of elapsed time (day): comparison graph of the crystalline urea and deep-eutectic urea-containing composites’ ammonia emissions.

[0020] BRIEF DESCRIPTION OF THE INVENTION

[0021] 1. Slow-release fertilizer, comprising the following ingredients: a urea-based fertilizer and saccharide mixture in deep eutectic composition and carbon-based carrier.

[0022] 2. Slow-release, urea-based fertilizer according to Point 1, comprising the following ingredients: urea and saccharide in deep eutectic composition and lignite powder characterized in that the melting point of the urea-saccharide deep eutectic composition mixture is ~ 84 °C.

[0023] 3. Slow-release, urea-based fertilizer according to Point 1 or 2, wherein the saccharide component comprises a substance selected from the following group: mono-, di-, and oligosaccharides, their corresponding alcohols, or mixtures thereof, preferably a saccharide selected from the following group: glucose, fructose, mannitol, maltose, and sucrose.

[0024] 4. Slow-release, urea-based fertilizer of any one of to Points 1 to 3, in which

[0025] a) the urea used is crystalline and anhydrous; and / or

[0026] b) the saccharide used has a maximum particle size of 100 pm, preferably 65-90 pm, more preferably 70 pm, has a maximum moister content of 0.1%; and / or

[0027] c) the lignite used has a maximum particle size of 0.5 mm, preferably 0.4 mm, and a maximum moister content of 0.1%. 5. Slow-release, urea-based fertilizer of any one of Points 1 to 4, in which

[0028] a) contains 11-24 mass% of the urea raw material calculated on the mass of the final product; b) contains 33-45 mass% of the saccharide raw material calculated on the mass of the final product;

[0029] c) contains 31-46 mass% of the lignite raw material calculated on the mass of the final product; in such a way that any possible composition results 100 mass% final product.

[0030] 6. A process for producing slow-release, urea-based fertilizer according to any of Points 1 to 4, characterized in that

[0031] a) measuring 11-24 mass% of urea calculated on the mass of the final product on 33-45 mass% of saccharide calculated on the mass of the final product and melting the mixture;

[0032] b) homogenizing the resulted molten material;

[0033] c) pouring 31-46 mass% of lignite powder calculated on the mass of the final product over the homogenized molten material, and homogenizing the resulted material, thus getting honeyviscosity product;

[0034] d) optionally storing the received material in an airtight container until it solidifies;

[0035] e) optionally crushing the resulted material and we sieve it to a particle size of 0.5 mm or below.

[0036] 7. The process of Point 6, characterized in that

[0037] a) the saccharide used has a particle size of maximum 100 pm, preferably 65-90 pm, more preferably 70 pm, has a maximum moister content of 0.1%; and / or

[0038] b) the urea used is crystalline and anhydrous; and / or

[0039] c) the lignite used has a maximum particle size of 0.5 mm, preferably 0.4 mm, and a maximum moister content of 0.1%. 8. The process of Point 6 or 7, characterized in that

[0040] a) after reaching the melting point according to step a) of point 6, stirring the mixture for 5-15 minutes, preferably 8-11 minutes at 100-220 rpm rotational speed;

[0041] b) mixing according to step c) of point 6 for 5-20 minutes, preferably 9-15 minutes at 100-220 rpm;

[0042] c) storing according to step d) of point 6 for 20-24 hours.

[0043] DETAILED DESCRIPTION OF THE INVENTION

[0044] The eutectic is defined as a mixture of elements or compounds, which has a defined composition and a lower melting point than the melting points measured separately for each component. In contrast, the deep eutectic has an even lower melting point compared to the eutectic temperature and shows unique physicochemical properties. While eutectic mixtures also have low melting points, deep eutectics are typically liquids at room temperatures and consist of a combination of a salt and a hydrogen bond donor compound (e.g. a carboxylic acid or alcohol). The difference between the two types lies mainly in their composition and behaviour. Deep eutectic solvents are considered particularly advantageous in green chemistry and sustainable technologies, as they can be used as environmentally friendly, non-toxic solvents, providing a favourable alternative to conventional solvents in many industrial applications.

[0045] According to our process, slow-release lignite-carbohydrate-urea-based composite can be made by melting the mixture of the urea mixed with the amount of carbohydrates specified in this description in the first step. The melting point of the urea is 133 °C, the melting point of glucose is 150 °C. The uniqueness of deep eutectics lies in that within certain compositional ranges, the melting point of the resulting mixture is below the melting temperatures of the individual components, and the solidifying liquid forms special mixed crystallites in the form of a solid solution. These crystallites are urea and carbohydrate in our case. In the second step, we pour the still liquid molten material on the surface of the dried and grinded lignite, and mix it in. By doing this, we introduce crystallization nuclei into the system, creating the conditions for the formation of crystallites. Thanks to the porous structure of the lignite, the eutectic flows into these macro-, meso- and micropores it forms a surface bond based on strong chemosorption directed by smart-sorption, by immobilizing the urea on the lignite surface. This means that there is practically no free urea in the soil, the plant will not suffer chemical shock, the urea won’t migrate to the deeper layers, there is no degrading and rain-induced leaching. Urea liberation is also caused by soil bacteria, but in this case, we don’t control the urease enzyme production of the bacteria, we don’t interfere with the biological process at the chemical level, but rather slowly making the urea available for the bacteria. The nitrogen liberation is the function of steric inhibition. The bacteria have difficulty physically reaching the carbamide, which slows down the release. Meanwhile there is no free urea in the soil, there is no leaching and environmental pollution, thus the plant continuously gets nutrient from the near-surface layer, 85-90% of nutrients are utilized compared to the usual 40%. The composite fertilizer only needs to be applied once, providing a steady, stress-free nutrient release over several months, without harming the environment or interfering with bacterial activity, with the help of environmentally friendly materials.

[0046] The composite according to the invention can not be made by simply mixing the materials, since the presence of liquid phase is necessary for the sorption. We make this by induced phase transition, whose scientific basis is provided by the preparation of deep eutectic. The mixture is immobilized on the surface of the lignite carrier specifically, namely by smartsorption.

[0047] In one embodiment of the process according to the invention we put 33-45 m / m% saccharide with a particle size below 100 pm and moisture content below 0.1 m / m%. We measure 11-24 m / m% anhydrous urea on top of the saccharide and we melt the mixture. After reaching the melting point, it is mixed for 8-11 minutes with 100-220 rpm rotational speed till reaching complete homogenization. We pour 46-31 m / m% lignite powder grinded to less than 0.5 mm particle size and having a maximum of 0.1 m / m% moisture content over the liquid. We continue mixing at the same speed for 9-15 minutes. We pour the resulting viscous deep eutectic mixture into an airtight container. The composite solidifies within 48-96 hours and is easily crushable. We crush the resulting granular material in a mortar and pass it through a 5 mm sieve.

[0048] In one embodiment of the process according to the invention we prepare agrochemical composite by using lignite and solid carbohydrate according to the following proportions: we put 33-45% carbohydrate with a particle size below 100 pm and moisture content below 0.1 m / m% into an extruder, into which we previously added 11-24% anhydrous urea and we feed it through the screw. The mixture melts under the mechanical pressure, and after reaching its melting point, it is homogenized in the extruder head. We pour the liquid over the 46-31 m / m% lignite powder grinded to less than 0.5 mm particle size and having a maximum of 0.1 m / m% moisture content into the second hopper of a multi -head extruder. We continue mixing in the screw channel for 9-15 minutes, homogenizing the composite material. The resulting high-viscosity deep eutectic, bound to a lignite carrier via smart-sorption, is discharged from the extruder heads onto a conveyor belt and cut into uniform pieces with a vertically, periodically moving blade. The composite solidifies completely within 20-42 hours and can be easily packaged.

[0049] EXAMPLES

[0050] Example 1: Process for preparing slow release, urea-based, glucose-containing deepeutectic fertilizer

[0051] We measured 180 g glucose into a 500 mL beaker, which had 0.018 m / m% moisture content, and whose particle size was in the particle size range of 65-90 pm. We measured 60 g urea on top of the glucose. We melted the mixture and mixed it for 10 minutes at the melting temperature, which was 84 °C. Mixing was carried out with 150 rpm rotational speed. We added 200 g powdered lignite with particle size smaller than 0.4 mm and 0.085 m / m% moisture content to the obtained eutectic. After this, we mixed the mixture for another 10 minutes at 150 rpm rotational speed. We left the final composite to rest for 72 hours, then crushed it in a porcelain mortar and sifted through a 5000 pm sieve.

[0052] Example 2: Process for preparing slow release, urea-based, fructose-containing deepeutectic fertilizer

[0053] We added 185 kg fructose with a particle size below 70 pm and 0.05 m / m% moisture content into a two-arm kneading machine equipped with a jacketed heating system and a Freiburg-type Z-element. We measured 110 kg crystalline anhydrous urea into the fructose, and started to heat it. At the first indication that the mixture was starting to melt, we started the mixing arms. After 10 minutes of the complete melting, we stopped the mixing and the heating. We added 210 kg powdered lignite with a maximum particle size of 0.5 mm and 0.04 m / m% moisture content through the feeding opening, then started the mixing again for another 10 minutes. We set the mixer to the discharge position after the homogenization period and left the composite rest poured into a high-rimmed, foil-sealed trays for 70 hours. On the vibrating screen equipped with a cylindrical pre-crusher we set the particle size to below 5000 pm, and then we packed airtight the finished composite.

[0054] Example 3: Process for preparing slow release, urea-based, glucose-containing deepeutectic fertilizer

[0055] We measured 160 g glucose with a particle size between 65-90 micron and 0.018 m / m% moisture content into a 500 mL laboratory screw extruder. We measured 60 g urea on top of the glucose. The mixture melts during extrusion, at a rotational speed of 1500 rpm, by the heat generated by the pressure, at a temperature of 84 °C. We added 180 g powdered lignite with particle size smaller than 0.4 mm and 0.085 m / m% moisture content to the liquid formed, then we homogenized it in the second extruder for another 10 minutes. The composite leaving the extruder head was rested for 32 hours, then contained in a tightly closed container.

[0056] Example 4: Process for preparing slow release, urea-based, fructose-containing deepeutectic fertilizer

[0057] We added 375 g fructose with particle size smaller than 70 micron and 0.05 m / m% moisture content and 150 g crystalline anhydrous urea into the hopper of a 0.5 m3industrial screw extruder, then started the central shaft. After the pressure-induced phase transition of the two materials, we direct the mixture towards the feeder hopper of the multi-head extruder used for the second compounding. Through the feed opening by ratio control, we added 410 g powdered lignite with a maximum particle size of 0.5 mm and 0.04 m / m% moisture content simultaneously with the deep eutectic, then we started the mixing with a residence time of 10 minutes. After the homogenization period has elapsed, the composite left the extruder through the outlet openings and a Teflon conveyor belt placed under the extruder took over the continuously extruded malleable rods. A cutting knife in the first third of the belt by periodically descending sliced the composite, creating rods of adjustable length. At the end of the belt, the composite was placed on trays using a separating knife and left to rest for 24 hours. During this time, it reached its final strength and the product could be packaged.

Claims

CLAMIS1. Slow-release fertilizer, comprising the following ingredients: a urea-based fertilizer and saccharide mixture in deep eutectic composition and carbon-based carrier.

2. Slow-release, urea-based fertilizer according to Claim 1, comprising the following ingredients: urea and saccharide in deep eutectic composition and lignite powder characterized in that the melting point of the urea-saccharide deep eutectic composition mixture is ~ 84 °C.

3. Slow-release, urea-based fertilizer according to Claim 1 or 2, wherein the saccharide component comprises a substance selected from the following group: mono-, di-, and oligosaccharides, their corresponding alcohols, or mixtures thereof, preferably a saccharide selected from the following group: glucose, fructose, mannitol, maltose, and sucrose.

4. Slow-release, urea-based fertilizer of any one according to Claims 1 to 3, in which a) the urea used is crystalline and anhydrous; and / orb) the saccharide used has a maximum particle size of 100 pm, preferably 65-90 pm, more preferably 70 pm, has a maximum moister content of 0.1%; and / orc) the lignite used has a maximum particle size of 0.5 mm, preferably 0.4 mm, and a maximum moister content of 0.1%.

5. Slow-release, urea-based fertilizer of any one according to Claims 1 to 4, in which a) contains 11-24 mass% of the urea raw material calculated on the mass of the final product; b) contains 33-45 mass% of the saccharide raw material calculated on the mass of the final product;c) contains 31-46 mass% of the lignite raw material calculated on the mass of the final product; in such a way that any possible composition results 100 mass% final product.

6. A process for producing slow-release, urea-based fertilizer according to any of Claims 1 to 4, characterized in thata) measuring 11-24 mass% of urea calculated on the mass of the final product on 33-45 mass% of saccharide calculated on the mass of the final product and melting the mixture;b) homogenizing the resulted molten material;c) pouring 31-46 mass% of lignite powder calculated on the mass of the final product over the homogenized molten material, and homogenizing the resulted material, thus getting honeyviscosity product;d) optionally storing the received material in an airtight container until it solidifies;e) optionally crushing the resulted material and we sieve it to a particle size of 0.5 mm or below.

7. The process according to Claim 6, characterized in thata) the saccharide used has a particle size of maximum 100 pm, preferably 65-90 pm, more preferably 70 pm, has a maximum moister content of 0.1%; and / orb) the urea used is crystalline and anhydrous; and / orc) the lignite used has a maximum particle size of 0.5 mm, preferably 0.4 mm, and a maximum moister content of 0.1%.

8. The process according to Claim 6 or 7, characterized in thata) after reaching the melting point according to step a) of claim 6, stirring the mixture for 5-15 minutes, preferably 8-11 minutes at 100-220 rpm rotational speed;b) mixing according to step c) of claim 6 for 5-20 minutes, preferably 9-15 minutes at 100-220 rpm;c) storing according to step d) of claim 6 for 20-24 hours.

Images