Use of polysuccinimide, synergistic urea composition for improving urea processing and method for preparing the same

Abstract

The application discloses a new use of poly-succinimide in a production process of synergic urea, namely, the poly-succinimide is used as a dust suppression raw material and a dyeing raw material of a synergic urea composition, and simultaneously provides a synergic urea composition for improving urea processing and a preparation method thereof, which is prepared from a basic urea raw material, a synergic raw material, a dust suppression raw material and a dyeing raw material.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of urea production, in particular to the use of polysuccinimide as dust suppression and dyeing in the production process of synergistic urea composition, and the synergistic urea composition for improving urea processing prepared from polysuccinimide and preparation thereof. BACKGROUND

[0002] As an important component of agricultural fertilizer, urea can be used as growth period topdressing, slow-release nitrogen fertilizer, compound fertilizer, etc., and can also be used as water-soluble nitrogen fertilizer in water-fertilizer integration, which can supplement the urgently needed nitrogen nutrition in the critical period of crop growth. As a conventional agricultural product, urea application has the characteristics of concentration and rapidness, so the urea manufacturers will produce at high load in a certain period. The by-product biuret produced in the urea production process will cause dust, and damaged urea particles will inevitably be produced in the production, so there is a dust pollution problem in the process of high-load concentrated production.

[0003] In addition, due to the comprehensive influence of soil microorganisms, enzymes and chemicals in the environment on urea, the nitrogen utilization rate of urea is not high, and there is also a mismatch between the nitrogen supply of urea and the nutrient demand of plants, which further affects the nitrogen utilization rate of urea. Since 2000, various urea production enterprises have developed a variety of synergistic urea to improve the utilization rate of urea nitrogen. Among them, the main optimization scheme is to add inorganic salts containing trace elements, but the addition of inorganic salts will significantly increase the dust rate, bringing safety and environmental protection hazards to production. Although non-trace element-containing synergistic urea such as polypeptide urea and zinc fulvic acid urea has appeared with the development, the dust rate of synergistic urea is still high.

[0004] In addition to the problem of dust pollution, in order to distinguish synergistic urea from ordinary urea, it has become a trend to add pigments to synergistic urea, but some of the added pigments are harmful to the human body and the environment, affecting the usability and safety of urea products.

[0005] Therefore, the addition of synergistic substances and dyeing substances in urea production not only increases the production cost, but also brings some production drawbacks, so how to green, environmentally friendly and efficient solve these production problems has a positive promoting significance for the development of synergistic urea. SUMMARY

[0006] In view of the problems of dust pollution and dyeing drawbacks in the production process of synergistic urea, the present application creatively uses polysuccinimide as a functional raw material in the production process of synergistic urea, and provides a new use of polysuccinimide, i.e. using polysuccinimide as dust suppression raw material and dyeing raw material for synergistic urea composition.

[0007] Poly succinimide is a polymer of aspartic acid or ammonium maleate or ammonium fumarate, which has a cyclic amide bond structure in the molecular structure, can react with acid or base to obtain a new product, according to the structural characteristics of poly succinimide, and through experiments, it is found that poly succinimide can be directly used as a dust suppression raw material and a dyeing raw material of the urea composition. The addition of the material can not only solve the dust problem in the production process of the urea composition, but also realize the dyeing of the urea composition without adding artificial pigment, and improve the overall quality and performance of the urea composition.

[0008] As a limitation of the above technical solution, poly succinimide produced by aspartic acid through a phosphoric acid catalytic method (which needs to be purified and the catalyst is removed, the same below) is selected as a dust suppression raw material, and poly succinimide produced by ammonium maleate or ammonium fumarate through a thermal polymerization method is selected as a dyeing raw material.

[0009] Poly succinimide exists in three forms according to different processing raw materials and processing processes: ① poly succinimide produced by aspartic acid through a thermal polymerization method; ② poly succinimide produced by ammonium maleate or ammonium fumarate through a thermal polymerization method; and ③ poly succinimide produced by aspartic acid or ammonium maleate or ammonium fumarate as raw materials through a catalytic method. The three forms of poly succinimide are mainly different in the composition of the molecular weight and the spatial configuration, thereby playing different roles; in the production of urea, poly succinimide produced by ammonium maleate or ammonium fumarate through a thermal polymerization method can be used as a main coloring component of the urea composition, and poly succinimide produced by aspartic acid through a catalytic method with phosphoric acid as a catalyst can be used as a main dust suppression component in the production process of the urea composition, and a urea composition product which does not need to add artificial pigment, can significantly reduce dust and improve product performance is produced in a layer-by-layer wrapping manner.

[0010] Meanwhile, the present application develops a urea composition for improving efficiency in view of the problems of high dust rate in the production of the existing urea composition for improving efficiency and the drawbacks caused by the added pigment.

[0011] The urea composition for improving efficiency provided by the present application is mainly prepared by the reaction of a basic urea raw material (the basic urea raw material is liquid ammonia and carbon dioxide used in a conventional urea process, and CO(NH2)2 and a small amount of by-product biuret are generated by the reaction, wherein the biuret causes dust pollution in the production process of urea, and the production process promotes the generation of melamine with the increase of temperature, which also leads to the increase of dust), a efficiency-improving raw material, a dust suppression raw material and a dyeing raw material, the dust suppression raw material is poly succinimide produced by aspartic acid through a phosphoric acid catalytic method, the addition amount of the dust suppression raw material accounts for 0.1-0.3% of the total mass of the urea composition for improving efficiency, and the dyeing raw material is poly succinimide produced by ammonium maleate or ammonium fumarate through a thermal polymerization method, the addition amount of the dyeing raw material accounts for 0.05-0.2% of the total mass of the urea composition for improving efficiency.

[0012] The dust suppression raw material of the synergistic urea composition of the present application is poly-succinimide produced by phosphoric acid catalysis from aspartic acid. The molecular weight of the poly-succinimide is larger than that of common poly-succinimide product. After reacting with urea solution (the molten material before granulation in urea production process is collectively referred to as urea solution), a high molecular wrapping film can be formed. When the film is mixed with urea solution again, a non-uniform wrapping system is generated. When passing through the spray-drying nozzle, the wrapping system can enhance the strength of the granules, reduce the breakage of the granules, and reduce the interference of biuret in the granulation, thereby playing a dust suppression role. The poly-succinimide produced by thermal polymerization of ammonium maleate or ammonium fumarate is used as a dyeing raw material. After reacting with urea solution, a red to reddish brown substance can be formed. By adjusting the amount of addition, a urea granule core with bright color tone can be formed.

[0013] As a limitation of the above technical solution, the selection standard of the dust suppression raw material is that the molecular weight of poly-succinimide is not less than 5500, the monomer residue is less than 0.2%, the alkali insoluble substance is less than 0.1%, and the total phosphoric acid content is less than 1.0%, of which the polymerized phosphorus is not less than 80% of the total amount.

[0014] More preferably, the quality standard of the dust suppression raw material requires that the molecular weight of poly-succinimide is 6000-6500, the monomer residue is less than 0.1%, the alkali insoluble substance is 0.0%, the total phosphoric acid content is less than 0.5%, and the polymerized phosphorus is not less than 95% of the total amount.

[0015] The larger the molecular weight of the dust suppression raw material, the better the dust suppression effect. At the same time, the change of monomer residue and phosphoric acid content will affect the dust suppression effect. The phosphoric acid in the poly-succinimide produced by phosphoric acid catalysis will cause the increase of dust rate, so it needs to be removed by hot water washing before being used as a dust suppression raw material. Based on the limitation of the synthesis process of the dust suppression raw material, when the molecular weight is 5500-6500, the monomer residue and alkali insoluble substance in the obtained dust suppression material are the smallest, and the content and composition of phosphorus are the most conducive to the dust suppression effect in urea production.

[0016] As a limitation of the above technical solution, the selection standard of the dyeing raw material is that the molecular weight of poly-succinimide is 2500-3500, the conversion rate is not less than 95%, and the alkali insoluble substance is less than 0.2%.

[0017] More preferably, the quality standard of the dyeing raw material requires that the molecular weight of poly-succinimide is 2500-3000, the conversion rate is greater than 99.5%, and the alkali insoluble substance is 0%.

[0018] The molecular weight of the dyeing raw material is too high or too low, which will change the dyeing ability, in order to obtain stable color, the molecular weight of polysuccinimide needs to be limited in a relatively narrow range; and the polysuccinimide outside the required molecular weight range and other impurities such as unreacted raw materials existing in the production process of polysuccinimide will have a negative impact on the dyeing effect, so it is necessary to reduce as much as possible.

[0019] As a limitation of the above technical solution, the synergistic raw material includes at least one of polymeric amino acid, polymeric amino acid derivative, seaweed, humic acid, and trace element; the amount of the synergistic raw material accounts for 0.05-0.5% of the total mass of the urea composition; and the mass ratio of the synergistic raw material to the dyeing raw material is 2:1-3:1.

[0020] The conventional industrial urea can add more synergistic raw materials, which are generally divided into the following categories: one is polymeric amino acid and derivative, including polyaspartic acid, polyglutamic acid, polyaspartic acid salt, and polysuccinimide; two is seaweed, including alginic acid and seaweed polysaccharide; three is humic acid, including potassium humate, potassium fulvic acid, sodium humate, and sodium fulvic acid; four is trace element, generally including sulfate, nitrate, and EDTA salt; no matter which type of synergistic raw material is used, the dust suppression raw material and the dyeing raw material of the present application can play a good dust suppression and dyeing effect.

[0021] As a limitation of the above technical solution, the polymeric amino acid derivative is a mixture of polysuccinimide and sugar substances, wherein the polysuccinimide is polysuccinimide produced by thermal polymerization of aspartic acid, the sugar substances include at least one of monosaccharide, biological oligosaccharide, and sugar alcohol, and the mass ratio of polysuccinimide to sugar substances is 4-9:1.

[0022] As a limitation of the above technical solution, the selection standard of polysuccinimide used as a synergistic raw material is that the molecular weight of polysuccinimide is not less than 4000, the conversion rate is not less than 99%, the monomer residue is less than 0.5%, and the alkali insoluble substance is less than 0.1%; the monosaccharide includes at least one of glucose, mannose, and fructose; the biological oligosaccharide includes at least one of brown algal oligosaccharide, red algal oligosaccharide, and green algal oligosaccharide; and the sugar alcohol includes at least one of sorbitol, mannitol, and xylitol.

[0023] The synergistic raw material is polysuccinimide obtained by thermal polymerization of aspartic acid, although the molecular weight of the polysuccinimide is partially coincident with that of the polysuccinimide for dyeing and dust suppression, but because the chromogenic group is very small, it will have a slight effect on the color of urea, but it is easy to be affected by vision and cannot be distinguished from the color difference of white urea; at the same time, it has a small amount of dust suppression group, which needs to be added in a large amount to play a role, so it is not suitable for use as a dust suppression raw material and a dyeing raw material.

[0024] Furthermore, the present application also provides a preparation method of the synergistic urea composition for improving urea processing as described above, which is adding the dyeing raw material, the synergistic raw material and the dust suppression raw material respectively before the first evaporation, before the second evaporation and before the granulation stage after the reaction of the base urea raw material;

[0025] The dyeing raw material is added into the molten urea liquid conveying main pipeline after the reaction of the base urea raw material and before the first evaporator, and is conveyed to the granulation tower after being treated by two evaporators;

[0026] The synergistic raw material is added into the molten urea liquid conveying main pipeline between the first and second evaporators after the reaction of the base urea raw material, and is conveyed to the granulation tower after being treated by one evaporator;

[0027] The dust suppression raw material is added into the molten urea liquid conveying branch pipeline after the reaction of the base urea raw material, and is directly conveyed to the granulation tower before the granulation tower without being treated by two evaporators; the conveying branch pipeline is arranged in parallel with the conveying main pipeline before the first evaporator and after the second evaporator, and is used for conveying a small amount of molten urea liquid;

[0028] The dust suppression raw material is pre-mixed with the molten urea liquid in the conveying branch pipeline to generate a film-forming pre-polymer by addition reaction, and then returns to the conveying main pipeline to wrap the mixed urea liquid added with the dyeing raw material and the synergistic raw material before entering the granulation tower, so as to form a multi-layer soft granular material in a wrapped form with a pore structure, and the synergistic urea is obtained after drying.

[0029] In the present application, the dyeing raw material (as the inner core, before the first evaporator), the synergistic raw material (as the inner protective layer, between the first and second evaporators) and the dust suppression raw material (as the outer protective film, after pre-polymerization in the branch pipeline and mixed with the main pipeline without being treated by two evaporations and directly entering the granulation tower) are added through different feeding ports in the production process of the synergistic urea to form a structure wrapped layer by layer.

[0030] The dust suppression raw material is pre-mixed with the molten urea liquid in the conveying branch pipeline to generate a film-forming pre-polymer by addition reaction, and then returns to the conveying main pipeline to wrap the mixed urea liquid added with the dyeing raw material and the synergistic raw material before entering the granulation tower, so as to form a multi-layer soft granular material in a wrapped form with a pore structure, and the synergistic urea is obtained after drying.

[0031] Since the synergistic material and the dust suppression material do not have chemical reaction, the synergistic material and the dust suppression material are added, so that the core formed by the dyeing material and the urea solution is wrapped by two layers of transparent "clothes", the color of the whole particle is changed by light, and the synergistic urea with color is formed.

[0032] In addition, the dust suppression material, the synergistic material and the dyeing material jointly form a system with a wide molecular weight distribution range, so that the poly succinimides with different molecular weights can participate in the control of the release and conversion of nitrogen in urea, thereby making up for the defects of ordinary urea, such as fast release and easy loss of nitrogen, so as to make it become more effective urea.

[0033] As a limitation of the above technical solution, the film-forming prepolymer formed by the dust suppression material in the conveying branch pipeline enters the conveying main pipeline by means of high-speed shearing-jet grouting; the dyeing material and the synergistic material are added into the molten urea solution in the conveying main pipeline by means of powder spraying respectively; the temperature of the molten urea solution after adding the synergistic material is controlled at 130-150 DEG C between the primary and secondary evaporators.

[0034] When the film-forming prepolymer formed by the dust suppression material in the conveying branch pipeline enters the conveying main pipeline, high-speed shearing-jet grouting mode is adopted, which can be realized by flow meter-high-speed stirrer-high-pressure nozzle, and the addition and mixing are completed before entering the prilling tower. The synergistic material and the dyeing material are added into the production system by means of powder spraying respectively between the primary and secondary evaporators and before the primary evaporator.

[0035] The temperature between the primary and secondary evaporators where the synergistic material is added is generally controlled at 130-150 DEG C, so as to reduce the negative effects of Maillard reaction. Maillard reaction is a specific reaction between sugar substances and primary amine substances, and the primary and intermediate reactions will occur under the condition of 130-150 DEG C, which will not cause color change, but will produce a sweet smell close to chocolate flavor; when the reaction temperature is above 150 DEG C, the final reaction will occur, which will produce the color of chocolate and a bitter taste. The technical solution of the present application controls the production process to not produce unpleasant taste and color, otherwise the addition of the dyeing material is meaningless; in addition, above 150 DEG C will produce a large amount of biuret, thereby increasing the dust and weakening the effect of the dust suppression material. At the same time, the primary and intermediate stages of Maillard reaction are retained, so that the formed urea is endowed with special aroma while improving the effect.

[0036] The synergic urea composition obtained by the application improves the large amount of dust and the need of adding artificial colorant in the urea processing process while retaining the urea synergic effect. The poly succinimide produced by the hot polymerization of ammonium maleate or ammonium fumarate is used as the dyeing raw material, which wraps the urea core to form a product with obvious color difference from white urea. The poly succinimide produced by the phosphoric acid catalysis of aspartic acid is used as the outer protective film, which reduces the dust generation in the processing process by using the large molecular weight of the urea liquid pre-polymer. The large molecular weight has two effects, one is that the larger the molecular weight is, the smaller the dust generation is, and the other is that the water-soluble material is produced, the larger the molecular weight is, the smaller the dependence on water after application is, and the larger the nutrient fixation efficiency is. In addition, the poly succinimide produced by the hot polymerization of aspartic acid and other synergic substances are used as the main synergic substances, so that the obtained urea solves the problems of the need of adding artificial colorant and large amount of dust and has a good synergic effect on urea. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 , the preparation flow chart of the synergic urea composition of the application;

[0038] Figure 2 , the Fourier infrared spectrum of the dust suppression raw material used in the synergic urea composition of Example 1 of the application;

[0039] Figure 3 , the matching control of the Fourier infrared spectrum of the dust suppression raw material used in the synergic urea composition of Example 1 of the application and urea;

[0040] Figure 4 , the Fourier infrared spectrum of the synergic raw material used in the synergic urea composition of Example 1 of the application;

[0041] Figure 5 , the matching control of the Fourier infrared spectrum of the synergic raw material used in the synergic urea composition of Example 1 of the application and acetylpic acid;

[0042] Figure 6 , the Fourier infrared spectrum of the dyeing raw material used in the synergic urea composition of Example 1 of the application;

[0043] Figure 7 , the matching control of the infrared spectrum of the dyeing raw material used in the synergic urea composition of Example 1 of the application and acetylpic acid;

[0044] Figure 8 , the red granular urea dyed by amaranth;

[0045] Figure 9 , the dust photo collected in the conventional production process of urea;

[0046] Figure 10 Figure 2 is an electron microscope photo of the synergistic urea composition of Example 1. DETAILED DESCRIPTION

[0047] The technical solutions of the present application will be clearly and completely described below in combination with examples. Obviously, the described examples are only some of the embodiments of the present application, but not all the embodiments. Based on the examples in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0048] The raw materials involved in the following examples and comparative examples are typical products purchased in the market.

[0049] Example 1

[0050] The present example relates to a synergistic urea composition and its preparation.

[0051] The raw materials of the synergistic urea composition include:

[0052] The raw materials of the base urea include liquid ammonia and carbon dioxide, wherein the liquid ammonia is prepared by synthetic ammonia and the carbon dioxide is obtained by purification of a gas making system; the raw materials of the base urea are prepared according to the prior art process or directly purchased;

[0053] The synergistic raw material is a mixture of poly-succinimide produced by thermal polymerization of aspartic acid and seaweed oligosaccharide and mannitol; wherein the molecular weight of the poly-succinimide is 4500, the conversion rate is 99.8%, the monomer residue is 0.2%, and the alkali insoluble substance is 0;

[0054] The dust suppression raw material is poly-succinimide produced by phosphoric acid catalysis of aspartic acid; the poly-succinimide product removes most of the catalyst through purification, wherein the poly-succinimide contains polymeric phosphorus, the molecular weight is 5580, the monomer residue is 0.2%, the alkali insoluble substance is 0.1%, and the total phosphoric acid content is 0.9% (polymeric phosphorus accounts for 85.6%);

[0055] The dyeing raw material is poly-succinimide produced by thermal polymerization of ammonium maleate; the molecular weight of the poly-succinimide is 2600, the conversion rate is 96.2%, and the alkali insoluble substance is 0.15%;

[0056] In each ton of urea product (the final synergistic urea product, the same below), the addition amount of the synergistic raw material is 3.00 kg, wherein the poly-succinimide is 1.50 kg, the seaweed oligosaccharide is 0.96 kg, and the mannitol is 0.54 kg; the addition amount of the dust suppression raw material is 1.00 kg; and the addition amount of the dyeing raw material is 1.5 kg.

[0057] The specific preparation process is as follows Figure 1As shown, in the production process of urea, the basic urea raw material liquid ammonia and carbon dioxide are catalytically synthesized into molten urea liquid in a catalytic tower (the process is carried out according to the conventional urea catalytic synthesis process, including catalytic synthesis, primary evaporation, secondary evaporation, granulation and other processes, which belongs to the prior art, and will not be described in detail here). Then the dyeing raw material is added into the feeding port before the first evaporator (i.e. the primary evaporator) of the urea production system by spraying at an addition amount of 156.25 kg / h (calculated according to the single-line annual output of 800,000 tons and the annual effective production length of 320 days, the same below), and mixed and reacted with the molten urea liquid to form a red liquid by relying on the pushing pressure in the system; the premixed synergistic raw material is added into the above-mentioned red liquid by spraying at an addition amount of 312.50 kg / h in the feeding port between the first and second evaporators (i.e. the primary and secondary evaporators), and mixed and reacted by relying on the pressure in the system, with the temperature controlled at 135±2℃, to obtain a mixture of urea granules and liquid urea, wherein the inside of the granules is red and the outer layer is transparent film-shaped; the dust suppression raw material is added into the conveying branch pipeline connected in parallel with the molten urea liquid conveying main pipeline after the discharge of the catalytic tower at an addition amount of 104.17 kg / h, and reacts with the molten urea liquid in the branch pipeline to form a film-forming prepolymer. With the decrease of the temperature of the material in the pipeline, the molten urea liquid gradually condenses to form crystal beads, and the film-forming prepolymer forms an incompletely wrapped film-shaped structure outside the crystal beads. The branch pipeline passes through the first and second evaporators and is connected back to the conveying main pipeline before the prilling tower. The film-forming prepolymer in the branch pipeline enters the conveying main pipeline before the prilling tower by high-speed shearing-spraying at an addition amount of 104.17 kg / h (the addition amount of the dust suppression raw material is determined according to the reaction ratio of 1:20 of the molar ratio of the dust suppression raw material to the urea liquid in the branch pipeline, which is selected according to the kinematic viscosity and reaction rate after the reaction of the dust suppression raw material. The larger the ratio, the greater the kinematic viscosity of the dust suppression material formed, and the reaction rate will also decrease), and continues to be conveyed to wrap the mixed urea liquid added with the dyeing raw material and the synergistic raw material, with the temperature controlled at 132±2℃; finally, the above-mentioned mixture is conveyed to the prilling tower for prilling to obtain special urea I; the special urea I is a spherical body with a hollow surface, wrapped with a transparent film body, and its electron microscope photograph is shown in Figure 1. Figure 10 .

[0058] The dust suppression raw material, the synergistic raw material and the dyeing raw material used in the example were respectively subjected to Fourier infrared analysis. The dust suppression raw material was matched with the infrared spectrum of the urea (i.e. the basic urea product) in the library with the closest structure, and the matching degree was 68.9%; the synergistic raw material was matched with the infrared spectrum of the levulinic acid in the library with the closest structure, and the matching degree was 79.55%; the dyeing raw material was matched with the infrared spectrum of the levulinic acid in the library with the closest structure, and the matching degree was 80.83%; since the matching degrees are all lower than 90%, it is indicated that the detected dust suppression raw material, the synergistic raw material and the dyeing raw material are all new substances different from those in the library; the spectrum and the matching control diagram are shown in the attached drawings. Figures 2 to 7 .

[0059] Through the spectrum analysis, it is considered that the wavelength greater than 2500 cm -1 in the infrared spectrum has certain effect on the dyeing and dust suppression; taking the dyeing raw material spectrum structure as an example, the peak response values at 2950 cm -1 and 3273 cm -1 are both large, among which the peak at 3273 cm -1 is particularly obvious, and the comprehensive effect of the two influences the dyeing effect; in the spectrum structure of the synergistic raw material, it is found that the peak at 2950 cm -1 is retained, while the peak at 3273 cm -1 which mainly influences the color presentation disappears, and a new peak at 3595 cm -1 with the synergistic effect appears; therefore, it is known that the synergistic raw material retains a small part of the dyeing effect, but most of the dyeing effect is eliminated; in the spectrum of the dust suppression raw material, the peaks at 2950 cm -1 and 3273 cm -1 which influence the color effect both disappear, so the dust suppression material does not have the dyeing effect; at the same time, the peak at 3595 cm -1 with the synergistic effect also disappears, so the synergistic effect is greatly inhibited, and therefore it is inferred that the peak at 3453 cm -1 which is newly generated plays a decisive role in the dust suppression effect, and this peak is not possessed by the dyeing material and the synergistic material.

[0060] Example 2

[0061] This example relates to a synergistic urea composition and the preparation thereof.

[0062] In the synergistic urea composition:

[0063] The synergistic raw material is polyaspartic acid sodium salt with pH of 8.5 and effective content of 99.5%;

[0064] The dust suppression raw material is poly succinimide produced by aspartic acid through phosphoric acid catalysis, and the raw material indexes are the same as those in Example 1.

[0065] The dyeing raw material is poly succinimide produced by ammonium maleate through thermal polymerization, and the raw material indexes are the same as those in Example 1.

[0066] Specific preparation process: in the production process of urea, liquid ammonia and carbon dioxide in the catalytic tower are catalytically synthesized into molten urea liquid, and the dyeing raw material and the dust suppression raw material are added according to the process and the adding amount of Example 1; the efficiency raw material is also added at the feeding port between the first-stage evaporator and the second-stage evaporator at an adding amount of 3.0 kg per ton of urea product, and is mixed and reacted by using the pressure in the urea system, with the temperature being controlled at 135±2℃; all the materials are jointly fed into the prilling tower for prilling to obtain special urea II. The special urea II is a smooth red granular material.

[0067] Comparative Example 1

[0068] The efficiency raw material of the conventional efficiency urea composition is poly aspartic acid sodium salt, and the dyeing raw material is food-grade amaranth; the poly aspartic acid sodium salt has a pH of 8.5 and an effective content of 99.5%.

[0069] Specific preparation process: after liquid ammonia and carbon dioxide are catalytically synthesized into molten urea liquid in the catalytic tower, poly aspartic acid sodium salt is pre-mixed uniformly at an adding amount of 3.0 kg per ton of urea product, and amaranth is pre-mixed uniformly at an adding amount of 120 g per ton of urea product, and then is added to the above-mentioned liquid at the feeding port between the first-stage evaporator and the second-stage evaporator, and is mixed and reacted by using the pressure in the urea system, with the temperature being controlled at 135±2℃; after sufficient mixing, all the materials are transported to the prilling tower for prilling to obtain special urea III. The special urea III is a smooth red granular material.

[0070] Comparative Example 2

[0071] The difference between this comparative example and Example 1 is that no dust suppression raw material is added.

[0072] In the efficiency urea composition, the efficiency raw material and the dyeing raw material are completely the same as those in Example 1 (the raw materials and the adding amounts are the same), and no dust suppression raw material is added.

[0073] Specific preparation process: after liquid ammonia and carbon dioxide are catalytically synthesized into molten urea liquid in the catalytic tower, the efficiency material and the dyeing material are added to the reaction system according to the process and the adding amount of Example 1; finally, all the materials are transported to the prilling tower for prilling to obtain special urea IV. The special urea IV is a smooth granular material.

[0074] Comparative Example 3

[0075] The difference between the present comparative example and Example 1 is that the dyeing raw material is different, and no dust suppression raw material is added.

[0076] In the synergistic urea composition, the synergistic raw material is the same as that in Example 1, and the addition amount is 3 kg per ton of urea product; the dyeing raw material is food-grade amaranth, and the addition amount is 120 g per ton of urea product. The purity of the food-grade amaranth is 85%, which meets the relevant national standards.

[0077] The specific preparation process is as follows: after liquid ammonia and carbon dioxide are catalytically combined into molten urea liquid in the catalytic tower, the uniformly mixed synergistic raw material and amaranth are pre-mixed, and then added into the urea liquid from the feeding port between the first-stage and second-stage evaporators at an amount of 3.12 kg per ton of urea product, and mixed and reacted by using the pressure in the system; finally, all the materials are transported to the prilling tower for prilling to obtain special urea V. The special urea V is a red granular urea product with a smooth outer surface, Figure 8

[0078] Comparative Example 4

[0079] The difference between the present comparative example and Example 1 is that no dyeing raw material is added, and no dust suppression raw material is added.

[0080] In the synergistic urea composition, the synergistic raw material is the same as that in Example 1, and the addition amount is 3 kg per ton of urea product; no dyeing raw material and dust suppression raw material are added.

[0081] The specific preparation process is as follows: after liquid ammonia and carbon dioxide are catalytically combined into molten urea liquid in the catalytic tower, the uniformly mixed synergistic raw material is added into the molten urea liquid from the feeding port between the first-stage and second-stage evaporators, and mixed and reacted by using the pressure in the system; finally, all the materials are transported to the prilling tower for prilling to obtain special urea VI. The special urea VI is a granular urea product with a smooth outer surface.

[0082] The dust rate of the synergistic urea product obtained in the above examples and comparative examples and the production process is detected, and the results are shown in the following table. The determination of nitrogen content and biuret content refers to the relevant provisions in GB 2440-2017 Urea; the color value is determined according to the relevant provisions of Platinum-Cobalt Colorimetry (GB / T11903-1989 Determination of Color in Water); the dust rate is determined by weight method (the ratio of dust collection amount to total production amount), Figure 9

[0083]

[0084] ​​From the data in the above table, there is no difference between the nitrogen content of the samples involved, which shows that the urea products produced by the examples and comparative examples meet the relevant requirements of the national standard GB / T 2440-2017 Urea; biuret is a by-product of the urea production process, and is one of the main indicators for the control of urea production. The reduction of its content can reduce the toxic effect of urea directly used on seedlings, and also can reduce the amount of dust generated during the urea production process, saving costs.

[0085] From the data in the above table, the biuret content of examples 2 and comparative example 1 is the highest, and the biuret content of examples 1 and comparative examples 2-4 is reduced. It is found through analysis that the addition of the commonly used urea synergist polyaspartic acid will increase the measured content of urea biuret (this involves the problem of detection. Polyaspartic acid will react with urea solution to form polyaspartic acid amide, which has a structure similar to biuret. The existing national standard cannot rule out this, so it will increase). The synergistic material in the composition of the present application will not cause the increase of biuret, and has a positive effect on the improvement of crop health (the increase of biuret will cause the growth of seedlings to be hindered, which is known in the industry) and the reduction of dust rate.

[0086] Urea strength is a direct manifestation of the hardness of urea product, which determines the appearance and storage performance of urea. It is generally believed that the higher the strength, the less the crushing rate and dust amount will be. As can be seen from the above table, examples 1 and 2 can significantly improve the strength of urea. It is found through analysis that the strength of urea and the dust rate have a certain synchronous relationship, so the addition of poly succinimide produced by aspartic acid through phosphoric acid catalysis can significantly improve the strength of urea, and the addition of poly succinimide produced by aspartic acid through thermal polymerization also has a certain effect on improving the strength of urea. Therefore, the dust suppression material in the composition of the present application has outstanding effect, and at the same time, it can reduce the generation of dust and enhance the strength of urea.

[0087] In addition, the dust rate is related to the production cost of urea enterprises. At present, the selling price of granular urea is 2500 yuan / ton, while the selling price of powdery urea is 1900 yuan / ton due to the nitrogen content of about 40%, which does not meet the national standard. According to the dust rate in the above table, a single production line with an annual output of 800,000 tons can generate nearly 5 million yuan for the enterprise. (The enterprise will lose 600 yuan for every ton of powdery urea produced; according to the dust generation rate above, example 1 will produce 9040 tons of powdery urea less, with a total loss of 5.424 million yuan, considering the error, it is directly about 5 million yuan.)

[0088] The chroma is not an essential attribute of urea commodity, but a value-added attribute. The synergistic urea with color can be distinguished from ordinary urea, but long-term addition of pigment raw materials will cause environmental pollution. In the national standard GB38400-2019 Fertilizer, the limit of toxic and harmful substances has relevant prohibition of adding pigment. In the data of the above chroma, it is found that the poly succinimide produced by ammonium maleate through thermal polymerization does not belong to pigment raw materials, but after reaction in molten urea solution, the color can be increased without adding pigment.

[0089] In summary, the synergistic urea composition of the present application improves the disadvantages of large amount of dust and the need to add artificial pigment in the urea processing process while retaining the synergistic effect on urea, which can create better benefits for urea production enterprises.

Claims

1. A synergistic urea composition for improving urea processing, characterized by: The synergistic urea is prepared by reaction of base urea raw material, synergistic raw material, dust suppression raw material and dyeing raw material, wherein the dust suppression raw material is poly-succinimide with molecular weight not less than 5500 produced by aspartic acid through phosphoric acid catalysis method, and the dust suppression raw material accounts for 0.1-0.3% of the total mass of the synergistic urea composition; the dyeing raw material is poly-succinimide with molecular weight of 2500-3500 produced by ammonium maleate or ammonium fumarate through thermal polymerization method, and the dyeing raw material accounts for 0.05-0.2% of the total mass of the synergistic urea composition; The dyeing raw material, the synergistic raw material and the dust suppression raw material are added respectively before the first evaporation, before the second evaporation and before the granulation stage after the reaction of the base urea raw material; The dyeing raw material is added into the molten urea liquid conveying main pipeline after the reaction of the base urea raw material and before the first evaporator, and is conveyed to the granulation tower after being treated by two evaporators; The synergistic raw material is added into the molten urea liquid conveying main pipeline between the first and second evaporators after the reaction of the base urea raw material, and is conveyed to the granulation tower after being treated by one evaporator; The dust suppression raw material is added into the molten urea liquid conveying branch pipeline after the reaction of the base urea raw material, and is directly conveyed to the granulation tower before the granulation without being treated by two evaporators; the conveying branch pipeline is arranged in parallel with the conveying main pipeline before the first evaporator and after the second evaporator, and is used for conveying a small amount of molten urea liquid; The dust suppression raw material is premixed with the molten urea liquid in the conveying branch pipeline to generate a film-forming prepolymer through addition reaction, and then is returned to the conveying main pipeline to wrap the mixed urea liquid added with the dyeing raw material and the synergistic raw material before being conveyed into the granulation tower, thereby forming a multi-layer soft granular material in a wrapped form with a hole structure, and the synergistic urea is obtained after drying.

2. The synergistic urea composition to improve urea processing according to claim 1, characterized in that, The selection standard of the dust suppression raw material is that the poly-succinimide monomer residue is required to be less than 0.2%, the alkali insoluble substance is required to be less than 0.1%, and the total phosphoric acid content is required to be less than 1.0%, wherein the polymerized phosphorus is required to be not less than 80% of the total amount.

3. The synergistic urea composition to improve urea processing according to claim 1, characterized in that, The selection standard of the dyeing raw material is that the poly-succinimide conversion rate is required to be not less than 95%, and the alkali insoluble substance is required to be less than 0.2%.

4. The synergistic urea composition to improve urea processing according to claim 1, characterized in that: The synergistic raw material includes at least one of polymeric amino acid substance, polymeric amino acid derivative substance, seaweed substance, humic acid substance and trace element substance, and the synergistic raw material accounts for 0.05-0.5% of the total mass of the urea composition, and the mass ratio of the synergistic raw material to the dyeing raw material is 2:1-3:

1.

5. The synergistic urea composition to improve urea processing according to claim 4, characterized in that: The polymeric amino acid derivative substance is a mixture of poly-succinimide and sugar substance, wherein the poly-succinimide is poly-succinimide produced by aspartic acid through thermal polymerization method, the sugar substance includes at least one of monosaccharide, biological oligosaccharide and sugar alcohol, and the mass ratio of the poly-succinimide to the sugar substance is 4-9:

1.

6. The synergistic urea composition to improve urea processing according to claim 5, characterized in that, The selection criteria of the poly-succinimide used as the synergistic raw material are: the molecular weight of the poly-succinimide is not less than 4000, the conversion rate is not less than 99%, the monomer residue is less than 0.5%, and the alkali insoluble substance is less than 0.1%; the monosaccharide is at least one of glucose, mannose and fructose; the biological oligosaccharide is at least one of brown algal oligosaccharide, red algal oligosaccharide and green algal oligosaccharide; and the sugar alcohol is at least one of sorbitol, mannitol and xylitol.

7. The synergistic urea composition to improve urea processing according to claim 1, characterized by: The film-forming pre-polymer formed by the dust suppression raw material in the conveying branch pipeline enters the conveying main pipeline through high-speed shearing-spraying; the dyeing raw material and the synergistic raw material are respectively added into the molten urea liquid in the conveying main pipeline through powder spraying; and the temperature of the molten urea liquid after the addition of the synergistic raw material is controlled at 130-150 DEG C between the first and second evaporators.

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