Green, safe and environment-friendly granulation auxiliary agent for granular urea as well as preparation method and application of granulation auxiliary agent

Abstract

The invention relates to a green, safe and environment-friendly granulation auxiliary agent for granular urea and a preparation method and application thereof.The granulation auxiliary agent is prepared from 10%-20% of crystalline fructose, 5%-15% of carboxymethyl cellulose, 5%-15% of polyaspartic acid, 0.1%-0.5% of isothiazolinone and 50%-79.9% of purified water. Adding carboxymethyl cellulose in a spreading manner at normal temperature, standing on the water surface, and starting to stir uniformly after absorbing water and swelling for 24 hours, so as to obtain a carboxymethyl cellulose aqueous solution; stirring and completely dissolving the residual purified water, crystalline fructose and polyaspartic acid in another reaction kettle, adding the solution into the carboxymethyl cellulose aqueous solution within 1.5-2.5 hours, and continuously stirring; and finally, adding isothiazolinone, and uniformly stirring to obtain the granulation auxiliary agent. When the granulation aid is used, 0.5-2.0 kg of the granulation aid is pumped into a urea production system by a pressure pump per ton of urea to ensure that the granulation aid is effectively, sufficiently and uniformly mixed with urea melt to play a role in granulation, so that the traditional urea granulation aid formaldehyde is replaced.

Description

Technical Field

[0001] This invention relates to the field of granulation technology for granulated urea, and particularly to a green, safe and environmentally friendly granulation aid for granulated urea, its preparation method and application. Background Technology

[0002] 1. Overview of Urea Urea, also known as carboxamide, with the chemical formula CO(NH2)2, is a simple organic compound composed of carbon, nitrogen, oxygen, and hydrogen. It is a white crystalline solid. It is the main nitrogen-containing end product of protein metabolism in mammals and certain fish.

[0003] Urea is suitable as a fertilizer for various soils and plants. It is easy to store and use, has little negative impact on the environment, and is currently the most widely used chemical nitrogen fertilizer. It also has the highest nitrogen content among nitrogen fertilizers, containing 46% nitrogen (N).

[0004] Urea is readily soluble in water and slightly alkaline. Urea products are available in crystalline and granular forms. Crystalline urea is white, needle-like or prismatic crystals, highly hygroscopic, and clumps after absorbing moisture; its moisture absorption rate is 12 times faster than granular urea. Granular urea consists of white, somewhat transparent, regular particles with significantly improved hygroscopicity.

[0005] Urea can undergo condensation reactions at high temperatures. Heating to 150–160°C will deaminate it to biuret, and at 190°C and above, it will produce triuret and cyanuric acid. Urea can hydrolyze to produce ammonia and carbon dioxide under the action of acids, alkalis, and enzymes. Under the action of alkaline catalysts such as ammonia water, it can undergo a condensation reaction with formaldehyde to produce urea-formaldehyde resin.

[0006] Urea is synthesized by synthesizing ammonium carbamate from carbon dioxide and ammonia under high temperature and pressure, followed by decomposition, absorption and conversion, separation, evaporation and granulation.

[0007] 2NH3+CO2→NH2COONH4→CO(NH2)2+H2O Currently, typical urea synthesis processes include the carbon dioxide stripping method of Stamicarbon in the Netherlands, the ACES method of Toyo Corporation in Japan, the ammonia stripping method of Snamprogetti in Italy, the isobaric double stripping (IDR) method of Monte Edison, and the thermal cycling method of UTI in the United States.

[0008] Its granulation technologies mainly include fluidized bed granulation technology from Hydro of Norway, drum granulation method from Snamprogetti of Italy, rotary drum fluidized bed granulation technology from KT of France, sulfur spraying bed granulation process from Toyo Engineering (TEC), and Beijing Dalike's dual-drum granulation technology, which has developed rapidly in recent years in my country.

[0009] 2. Overview of Urea Granulation Auxiliaries Urea production involves three stages: synthesis, evaporation, and granulation. Urea granulation aids are added to the production system during the evaporation stage, typically after the first stage of evaporation or between the first and second stages.

[0010] The commonly used urea granulation aid is a 37% formaldehyde aqueous solution. According to the requirements of the national standard for urea, GB / T 2440-2017, the formaldehyde content should not exceed 0.6%. Therefore, many manufacturers add formaldehyde at a ratio not exceeding 1.5% when using it as an additive.

[0011] As is well known, formaldehyde is a toxic substance, and its specific characteristics are as follows: Acute toxicity: Acute formaldehyde poisoning manifests as irritation to the skin and mucous membranes. Inhalation of high concentrations of formaldehyde can cause respiratory irritation symptoms, such as sneezing, coughing, and a burning sensation in the nose and throat; it can also induce bronchial asthma, pneumonia, and pulmonary edema. Oral ingestion of 10–20 mL of formaldehyde solution can be fatal. In animal experiments, the LD50 of oral formaldehyde in rats was... 50 The LD50 of formaldehyde absorbed by rabbits via dermal absorption is 800 mg / kg. 50 The LD50 of formaldehyde in rats via inhalation is 2700 mg / kg. 50 590 mg / m 3 .

[0012] Chronic toxicity: Long-term exposure to formaldehyde can reduce respiratory function, the information integration function of the nervous system, and affect the body's immune response. It also has toxic effects on the cardiovascular, endocrine, digestive, reproductive, and renal systems. Systemic symptoms include headache, fatigue, loss of appetite, palpitations, insomnia, weight loss, and autonomic nervous system disorders.

[0013] Mutagenicity: Formaldehyde can induce mutations in Salmonella Typhimurium and Escherichia coli, regardless of the presence of metabolic activation systems. At 0.5 mg / m³ 3 1.0 mg / m 3 and 3.0 mg / m 3 Mice continuously and dynamically exposed to formaldehyde at a certain concentration for 72 hours showed a significant increase in the micronucleus rate of polychromatic erythrocytes in the bone marrow.

[0014] Carcinogenicity: Animal studies have shown that rats exposed to 15 μg / m³ of formaldehyde for 11 months developed nasal cancer. A recent study published by the National Cancer Institute on May 12, 2009, revealed that chemical plant workers frequently exposed to formaldehyde have a significantly higher chance of dying from leukemia, lymphoma, and other cancers than workers with less exposure.

[0015] On October 27, 2017, the International Agency for Research on Cancer (IARC) of the World Health Organization listed formaldehyde as a Group 1 carcinogen. On July 23, 2019, formaldehyde was included in the list of toxic and hazardous water pollutants (first batch). Simultaneously, it was included in the "List of Hazardous Chemicals (2015 Edition)" by my country's Ministry of Emergency Management, classifying it as a hazardous chemical.

[0016] However, the global urea production capacity exceeds 200 million tons annually, with China's capacity reaching nearly 80 million tons per year. Of this, large-particle urea accounts for nearly 20%. This indicates that China alone uses a staggering 192,000 tons of formaldehyde annually in urea production. Even considering reduced or eliminated formaldehyde use during winter production and the development of new urea products that do not use formaldehyde additives, this figure remains alarming. This will lead to increasingly numerous and significant health problems.

[0017] With the public's growing awareness of health and environmental protection, it is believed that my country will soon introduce strict laws and regulations to prohibit the use of formaldehyde as an additive in urea production.

[0018] As mentioned above, the use of formaldehyde as an additive in urea production will bring increasingly serious and prominent health and environmental problems that urgently need to be addressed. Green and environmentally friendly urea granulation aids will be formaldehyde-free, 100% natural and sustainable products. With a low overall addition ratio, they can efficiently improve the overall level of urea production, reduce overall energy consumption, and pose no health problems or environmental risks. Only green practices are sustainable; health is priceless. Summary of the Invention

[0019] The purpose of this invention is to address the granulation aids required in the granulation process of granular urea. Given the current situation where formaldehyde is the primary granulation aid, this invention provides a green, safe, and environmentally friendly granulation aid for granular urea, along with its preparation method and application. This invention primarily utilizes the different functional groups in organic molecules with varying carbon chain structures that readily form hydrogen bonds. These functional groups can form an effective hydrogen bond network with urea (H2NCONH2), thereby promoting particle formation during the granulation process and simultaneously increasing the particle strength of the urea particles.

[0020] The technical solution of this invention is as follows: This is a green, safe, and environmentally friendly granulation aid for granulated urea. The components, by mass percentage, are characterized as follows: the granulation aid consists of 10%-20% crystalline fructose, 5%-15% carboxymethyl cellulose, 5%-15% polyaspartic acid, 0.1%-0.5% isothiazolinone, and 50%-79.9% purified water, with the total of all components being 100%.

[0021] The crystalline fructose is a white crystal or powder at room temperature, and its fructose content is 98.0%–102.0% as determined by polarimetry. The pH value at 25°C is 4.0–7.0.

[0022] The carboxymethyl cellulose (CMC) is a white granular powder at room temperature, with a content of over 99% and a bulk density of 1.45–1.65 g / cm³. 3 The viscosity of a 2% aqueous solution at 25℃ is 100-140 mPa·s, and the degree of substitution DS≥0.9.

[0023] The polyaspartic acid (PASP) is a light brown to brown powder at room temperature, with a content of ≥95%, and a pH value of <10.5 for a 1% aqueous solution at 25°C.

[0024] The isothiazolinone is a light brown to brown transparent liquid at room temperature, with a content of 14.0%-15.0%, a pH value of 2.0-4.0 at 25℃, and a density of 1.26g / ml-1.32g / ml at 20℃.

[0025] The purified water is a colorless, odorless, and transparent liquid at room temperature, free of visible impurities, with a pH value of 6.0-8.0 at 25℃ and a conductivity of ≤10μs / cm at 25℃.

[0026] A method for preparing a green, safe, and environmentally friendly granulation aid for granular urea, characterized by comprising the following main steps: (1) First, add some of the pure water in the formula to the reactor, and add the measured carboxymethyl cellulose at room temperature. During the addition process, spread the carboxymethyl cellulose evenly on the water surface. After it absorbs water and swells for 24 hours, start stirring until a uniform carboxymethyl cellulose aqueous solution is obtained. (2) In another clean reactor, stir the remaining 50% of the purified water in the formula with the measured crystalline fructose and polyaspartic acid until completely dissolved; (3) Add the prepared crystalline fructose and polyaspartic acid aqueous solution to the carboxymethyl cellulose aqueous solution that has been stirred evenly. Ensure continuous stirring during the addition process and control the addition process between 1.5 and 2.5 hours. Finally, add the measured amount of isothiazolinone to the reactor and stir evenly to obtain the green, safe and environmentally friendly granulation aid for granular urea.

[0027] The application of this green, safe, and environmentally friendly granulation aid for granulated urea is characterized by injecting the granulation aid into the urea production system at a dosage of 0.5–2.0 kg / ton of urea using a pressure pump. The injection point is located at the end of the urea evaporation process, thereby ensuring that the granulation aid added to the urea production system can be effectively and fully mixed with the molten urea before granulation.

[0028] If there is a two-stage evaporation process in the urea production system, the granulation aid is added after the first-stage evaporation process.

[0029] The green, safe, and environmentally friendly granulation aid of this invention utilizes the different functional groups in organic molecules with different carbon chain structures that are prone to forming hydrogen bonds. These functional groups can form an effective hydrogen bond network with urea (H2NCONH2), thereby promoting particle formation during the granulation process and improving the particle strength of urea particles.

[0030] The green, safe, and environmentally friendly granulation aid of this invention uses formaldehyde-free green products as raw materials, which are 100% natural and sustainable. Its overall addition ratio is low, which can effectively improve the overall level of urea production, reduce overall energy consumption, and pose no health problems or environmental hazards. Only green practices can ensure sustainability; health is priceless.

[0031] The green, safe, and environmentally friendly granulation aid of this invention has a comprehensive dosage of 0.5–2.0 kg / ton of urea, resulting in an average increase in cost of approximately RMB 15.8 per ton of urea. Currently used traditional urea granulation aids are formaldehyde, with a dosage not exceeding 15 kg / ton of urea, resulting in an increase in cost of approximately RMB 20 per ton of urea. This is used to calculate the economic value brought by using the green, safe, and environmentally friendly granulation aid.

[0032] China: With a production capacity of nearly 80 million tons / year and a capacity utilization rate of 80%, the annual output value of urea granulation aids is approximately RMB 1.28 billion (formaldehyde granulation aids) and RMB 1.011 billion (green, safe and environmentally friendly granulation aids).

[0033] Globally, with a production capacity of 235 million tons per year and a capacity utilization rate of nearly 80%, the annual output value of urea granulation aids is approximately 3.76 billion yuan (formaldehyde granulation aids) and 2.97 billion yuan (green, safe, and environmentally friendly granulation aids). This makes the cost of using green, safe, and environmentally friendly granulation aids more advantageous than the currently used traditional formaldehyde granulation aids, which will be more conducive to market promotion. Detailed Implementation

[0034] The present invention will be further described with reference to the embodiments. Except for purified water, all raw materials used in the present invention were purchased directly. Specifically, the crystalline fructose used in the embodiments of the present invention was purchased from Shandong Xiwang Sugar Industry, the carboxymethyl cellulose (CMC) from Weifang Lite, the polyaspartic acid (PASP) from Shandong Yuanlian, the isothiazolinone from Nanjing Gutian, and the purified water was produced by our company using reverse osmosis (RO) technology. The self-produced purified water is a colorless, odorless, and transparent liquid at room temperature, free of visible impurities, with a pH value of 6.0-8.0 at 25℃ and a conductivity ≤10μs / cm at 25℃.

[0035] The heating is done electrically; the reactor is an enamel-lined reactor.

[0036] In the following examples, each component is expressed as a percentage by mass. Isothiazolinone is a preservative, added in small amounts and only serves a preservative function, and no gradient comparison is made.

[0037] Example 1 Add 25% pure water with a pH of 6.0 (25℃) and a conductivity of 10 μs / cm (25℃) to the reactor. Carboxymethyl cellulose (CMC) powder with a content of 99%, a mass concentration of 2%, a viscosity (25℃) of 100 mPa·s, and a degree of substitution (DS) of 0.9 was evenly spread on the surface of still water. After absorbing water and swelling for 24 hours, the mixture was stirred until a uniform carboxymethyl cellulose aqueous solution was obtained. Add 25% pure water with a pH of 6.0 (25℃) and a conductivity of 10 μs / cm (25℃) to another reactor. Add 20% of crystalline fructose (98.0% by optical rotation method) with a pH of 4.0 (25℃) to the reaction vessel in step C, and start stirring until completely dissolved; Add 15% of 95% polyaspartic acid (PASP) with a pH value (1% aqueous solution, 25℃) of 10.3 to the reaction vessel in C and stir until completely dissolved. Add the mixed solution obtained in step E to the well-stirred carboxymethyl cellulose aqueous solution. During the addition process, ensure continuous stirring and add slowly over a period of 2 hours. Finally, add the measured amount of 0.1% isothiazolinone to the reactor and stir until homogeneous to obtain a green, safe and environmentally friendly granulation aid for granular urea.

[0038] The green, safe, and environmentally friendly granulation aid product (granulation aid 1) from Example 1, and the existing granulation aid 0 (37% formaldehyde solution), were used separately in blank urea without granulation aids, with different dosages added, to conduct granulation experiments. The particle strength of the granulated particles was measured, and the particle strength improvement rate was calculated by comparing it with that of the blank urea. The experimental data are shown in Table 1.

[0039] Table 1: Note: The higher the particle strength value, the better the effect of the granulation aid; conversely, the lower the particle strength value, the worse the effect of the granulation aid.

[0040] The formula for calculating the strength improvement rate of urea particles is: Strength improvement rate of urea particles % = (strength of experimental group urea particles - strength of blank urea particles) / strength of blank urea particles * 100%.

[0041] Example 2 A. Add 35% pure water with a pH value (25℃) of 6.0 and a conductivity (25℃) of 10μs / cm to the reaction vessel; B. Spread 15% of carboxymethyl cellulose (CMC) powder with a content of 99%, a mass concentration of 2%, a viscosity (25℃) of 100 mPa·s, and a degree of substitution DS of 0.9 evenly on the surface of still water. After absorbing water and swelling for 24 hours, start stirring until a uniform carboxymethyl cellulose aqueous solution is obtained. C. Add 30% pure water with a pH of 6.0 (25℃) and a conductivity of 10 μs / cm (25℃) to another reactor. D. Add 14.5% (98.0% by optical rotation method) of crystalline fructose with a pH of 4.0 (25℃) to the reaction vessel in step C, and start stirring until completely dissolved; E. Add 5% of 95% polyaspartic acid (PASP) with a pH value (1% aqueous solution, 25℃) of 10.3 to the reaction vessel in C and stir until completely dissolved. F. Add the mixed solution obtained in E to the well-stirred carboxymethyl cellulose aqueous solution. During the addition process, ensure continuous stirring and add slowly. Control the addition process over 2 hours. Finally, add the metered 0.5% isothiazolinone to the reaction vessel and stir evenly to obtain a green, safe and environmentally friendly granulation aid for granular urea.

[0042] The green, safe, and environmentally friendly granulation aid product (granulation aid 2) from Example 2, and the existing granulation aid 0 (37% formaldehyde solution), were used separately with blank urea containing no granulation aid. Different amounts were added, and granulation experiments were conducted. The particle strength of the granulated particles was measured, and the particle strength improvement rate was calculated by comparing it with that of the blank urea. The experimental data are shown in Table 2.

[0043] Table 2: Note: The higher the particle strength value, the better the effect of the granulation aid; conversely, the lower the particle strength value, the worse the effect of the granulation aid.

[0044] The formula for calculating the strength improvement rate of urea particles is: Strength improvement rate of urea particles % = (strength of experimental group urea particles - strength of blank urea particles) / strength of blank urea particles * 100%.

[0045] Example 3 A. Add 35% pure water with a pH value (25℃) of 6.0 and a conductivity (25℃) of 10μs / cm to the reaction vessel; B. Spread 15% of carboxymethyl cellulose (CMC) powder with a content of 99%, a mass concentration of 2%, a viscosity (25℃) of 100 mPa·s, and a degree of substitution DS of 0.9 evenly on the surface of still water. After absorbing water and swelling for 24 hours, start stirring until a uniform carboxymethyl cellulose aqueous solution is obtained. C. Add 30% pure water with a pH of 6.0 (25℃) and a conductivity of 10 μs / cm (25℃) to another reactor. D. Add 10% of crystalline fructose with a content of 98.0% (optical rotation method) and a pH value of 4.0 (25℃) to the reaction vessel in step C, and start stirring until completely dissolved; E. Add 9.6% of 95% polyaspartic acid (PASP) with a pH value (1% aqueous solution, 25°C) of 10.3 to the reaction vessel in step C and stir until completely dissolved. F. Add the mixed solution obtained in step E to the well-stirred carboxymethyl cellulose aqueous solution. During the addition process, ensure continuous stirring and add slowly. Control the addition process over 2 hours. Finally, add the metered 0.4% isothiazolinone to the reaction vessel and stir evenly to obtain a green, safe and environmentally friendly granulation aid for granular urea.

[0046] The green, safe, and environmentally friendly granulation aid product (granulation aid 3) from Example 3, and the existing granulation aid 0 (37% formaldehyde solution), were used separately in blank urea without granulation aids, with different dosages added, to conduct granulation experiments. The particle strength of the granulated particles was measured, and the particle strength improvement rate was calculated by comparing it with that of the blank urea. The experimental data are shown in Table 3.

[0047] Table 3: Note: The higher the particle strength value, the better the effect of the granulation aid; conversely, the lower the particle strength value, the worse the effect of the granulation aid.

[0048] The formula for calculating the strength improvement rate of urea particles is: Strength improvement rate of urea particles % = (strength of experimental group urea particles - strength of blank urea particles) / strength of blank urea particles * 100%.

[0049] Example 4 A. Add 34.5% pure water with a pH of 6.0 (25℃) and a conductivity of 10 μs / cm (25℃) to the reaction vessel; B. Spread 10% of carboxymethyl cellulose (CMC) powder with a content of 99%, a mass concentration of 2%, a viscosity (25℃) of 100 mPa·s, and a degree of substitution DS of 0.9 evenly on the surface of still water. After absorbing water and swelling for 24 hours, start stirring until a uniform carboxymethyl cellulose aqueous solution is obtained. C. Add 30% pure water with a pH of 6.0 (25℃) and a conductivity of 10 μs / cm (25℃) to another reactor. D. Add 20% of crystalline fructose with a content of 98.0% (optical rotation method) and a pH value of 4.0 (25℃) to the reaction vessel in step C, and start stirring until completely dissolved; E. Add 5% of 95% polyaspartic acid (PASP) with a pH value (1% aqueous solution, 25°C) of 10.3 to the reaction vessel in step C and stir until completely dissolved. F. Add the mixed solution obtained in step E to the carboxymethyl cellulose aqueous solution that has been stirred evenly. During the addition process, ensure continuous stirring and add slowly. Control the addition process over 2 hours. Finally, add the measured 0.5% isothiazolinone to the reactor and stir evenly to obtain a green, safe and environmentally friendly granulation aid for granular urea.

[0050] The green, safe, and environmentally friendly granulation aid product (granulation aid 4) from Example 4, and the existing granulation aid 0 (37% formaldehyde solution), were used separately in blank urea without granulation aids, with different dosages added, to conduct granulation experiments. The particle strength of the granulated particles was measured, and the particle strength improvement rate was calculated by comparing it with that of the blank urea. The experimental data are shown in Table 4.

[0051] Table 4: Note: The higher the particle strength value, the better the effect of the granulation aid; conversely, the lower the particle strength value, the worse the effect of the granulation aid.

[0052] The formula for calculating the strength improvement rate of urea particles is: Strength improvement rate of urea particles % = (strength of experimental group urea particles - strength of blank urea particles) / strength of blank urea particles * 100%.

[0053] Example 5 A. Add 35% pure water with a pH value (25℃) of 6.0 and a conductivity (25℃) of 10μs / cm to the reaction vessel; B. Spread 9.7% of carboxymethyl cellulose (CMC) powder with a content of 99%, a mass concentration of 2%, a viscosity (25℃) of 100 mPa·s, and a degree of substitution DS of 0.9 evenly on the surface of still water. After absorbing water and swelling for 24 hours, start stirring until a uniform carboxymethyl cellulose aqueous solution is obtained. C. Add 30% pure water with a pH of 6.0 (25℃) and a conductivity of 10 μs / cm (25℃) to another reactor. D. Add 15% of crystalline fructose with a content of 98.0% (optical polarization method) and a pH value of 4.0 (25℃) to the reaction vessel in step C, and start stirring until completely dissolved; E. Add 10% of polyaspartic acid (PASP) with a content of 95% and a pH value (1% aqueous solution, 25°C) of 10.3 to the reaction vessel in step C, and stir until completely dissolved; F. Add the mixed solution obtained in step E to the carboxymethyl cellulose aqueous solution that has been stirred evenly. During the addition process, ensure continuous stirring and add slowly. Control the addition process over 2 hours. Finally, add the measured amount of 0.3% isothiazolinone to the reaction vessel and stir evenly to obtain a green, safe and environmentally friendly granulation aid for granular urea.

[0054] The green, safe, and environmentally friendly granulation aid product (granulation aid 5) from Example 5, and the existing granulation aid 0 (37% formaldehyde solution), were used separately with blank urea containing no granulation aid. Different amounts were added, and granulation experiments were conducted. The particle strength of the granulated particles was measured, and the particle strength improvement rate was calculated by comparing it with that of the blank urea. The experimental data are shown in Table 5.

[0055] Table 5: Note: The higher the particle strength value, the better the effect of the granulation aid; conversely, the lower the particle strength value, the worse the effect of the granulation aid.

[0056] The formula for calculating the strength improvement rate of urea particles is: Strength improvement rate of urea particles % = (strength of experimental group urea particles - strength of blank urea particles) / strength of blank urea particles * 100%.

[0057] Example 6 A. Add 35% pure water with a pH value (25℃) of 6.0 and a conductivity (25℃) of 10μs / cm to the reaction vessel; B. Spread 9.8% of carboxymethyl cellulose (CMC) powder with a content of 99%, a mass concentration of 2%, a viscosity (25℃) of 100 mPa·s, and a degree of substitution DS of 0.9 evenly on the surface of still water. After absorbing water and swelling for 24 hours, start stirring until a uniform carboxymethyl cellulose aqueous solution is obtained. C. Add 30% pure water with a pH of 6.0 (25℃) and a conductivity of 10 μs / cm (25℃) to another reactor. D. Add 10% of crystalline fructose with a content of 98.0% (optical rotation method) and a pH value of 4.0 (25℃) to the reaction vessel in step C, and start stirring until completely dissolved; E. Add 15% of 95% polyaspartic acid (PASP) with a pH value (1% aqueous solution, 25°C) of 10.3 to the reaction vessel in step C and stir until completely dissolved. F. Add the mixed solution obtained in step E to the carboxymethyl cellulose aqueous solution that has been stirred evenly. During the addition process, ensure continuous stirring and add slowly. Control the addition process over 2 hours. Finally, add the measured amount of 0.2% isothiazolinone to the reaction vessel and stir evenly to obtain a green, safe and environmentally friendly granulation aid for granular urea.

[0058] The green, safe, and environmentally friendly granulation aid product (granulation aid 6) from Example 6, and the existing granulation aid 0 (37% formaldehyde solution), were used separately in blank urea without granulation aids, with different dosages added, to conduct granulation experiments. The particle strength of the granulated particles was measured, and the particle strength improvement rate was calculated by comparing it with that of the blank urea. The experimental data are shown in Table 6.

[0059] Table 6: Note: The higher the particle strength value, the better the effect of the granulation aid; conversely, the lower the particle strength value, the worse the effect of the granulation aid.

[0060] The formula for calculating the strength improvement rate of urea particles is: Strength improvement rate of urea particles % = (strength of experimental group urea particles - strength of blank urea particles) / strength of blank urea particles * 100%.

[0061] Example 7 A. Add 35% pure water with a pH value (25℃) of 6.0 and a conductivity (25℃) of 10μs / cm to the reaction vessel; B. Spread 5% of carboxymethyl cellulose (CMC) powder with a content of 99%, a mass concentration of 2%, a viscosity (25℃) of 100 mPa·s, and a degree of substitution DS of 0.9 evenly on the surface of still water. After absorbing water and swelling for 24 hours, start stirring until a uniform carboxymethyl cellulose aqueous solution is obtained. C. Add 30% pure water with a pH of 6.0 (25℃) and a conductivity of 10 μs / cm (25℃) to another reactor. D. Add 20% of crystalline fructose with a content of 98.0% (optical rotation method) and a pH value of 4.0 (25℃) to the reaction vessel in step C, and start stirring until completely dissolved; E. Add 9.7% of polyaspartic acid (PASP) with a content of 95% and a pH value (1% aqueous solution, 25°C) of 10.3 to the reaction vessel in step C, and stir until completely dissolved; F. Add the mixed solution obtained in step E to the carboxymethyl cellulose aqueous solution that has been stirred evenly. During the addition process, ensure continuous stirring and add slowly. Control the addition process over 2 hours. Finally, add the measured amount of 0.3% isothiazolinone to the reaction vessel and stir evenly to obtain a green, safe and environmentally friendly granulation aid for granular urea.

[0062] The green, safe, and environmentally friendly granulation aid product (granulation aid 7) from Example 7, and the existing granulation aid 0 (37% formaldehyde solution), were used separately with blank urea containing no granulation aid. Different amounts were added, and granulation experiments were conducted. The particle strength of the granulated particles was measured, and the particle strength improvement rate was calculated by comparing it with that of the blank urea. The experimental data are shown in Table 7.

[0063] Table 7: Note: The higher the particle strength value, the better the effect of the granulation aid; conversely, the lower the particle strength value, the worse the effect of the granulation aid.

[0064] The formula for calculating the strength improvement rate of urea particles is: Strength improvement rate of urea particles % = (strength of experimental group urea particles - strength of blank urea particles) / strength of blank urea particles * 100%.

[0065] Example 8 A. Add 35% pure water with a pH value (25℃) of 6.0 and a conductivity (25℃) of 10μs / cm to the reaction vessel; B. Spread 5% of carboxymethyl cellulose (CMC) powder with a content of 99%, a mass concentration of 2%, a viscosity (25℃) of 100 mPa·s, and a degree of substitution DS of 0.9 evenly on the surface of still water. After absorbing water and swelling for 24 hours, start stirring until a uniform carboxymethyl cellulose aqueous solution is obtained. C. Add 30% pure water with a pH of 6.0 (25℃) and a conductivity of 10 μs / cm (25℃) to another reactor. D. Add 14.5% (98.0% by optical rotation method) of crystalline fructose with a pH of 4.0 (25℃) to the reaction vessel in step C, and start stirring until completely dissolved; E. Add 15% of 95% polyaspartic acid (PASP) with a pH value (1% aqueous solution, 25°C) of 10.3 to the reaction vessel in step C and stir until completely dissolved. F. Add the mixed solution obtained in step E to the carboxymethyl cellulose aqueous solution that has been stirred evenly. During the addition process, ensure continuous stirring and add slowly. Control the addition process over 2 hours. Finally, add the measured 0.5% isothiazolinone to the reactor and stir evenly to obtain a green, safe and environmentally friendly granulation aid for granular urea.

[0066] The green, safe, and environmentally friendly granulation aid product (granulation aid 8) from Example 8, and the existing granulation aid 0 (37% formaldehyde solution), were used separately in blank urea without granulation aids, with different dosages added, to conduct granulation experiments. The particle strength of the granulated particles was measured, and the particle strength improvement rate was calculated by comparing it with that of the blank urea. The experimental data are shown in Table 8.

[0067] Table 8: Note: The higher the particle strength value, the better the effect of the granulation aid; conversely, the lower the particle strength value, the worse the effect of the granulation aid.

[0068] The formula for calculating the strength improvement rate of urea particles is: Strength improvement rate of urea particles % = (strength of experimental group urea particles - strength of blank urea particles) / strength of blank urea particles * 100%.

[0069] Example 9 A. Add 40% pure water with a pH value (25℃) of 6.0 and a conductivity (25℃) of 10μs / cm to the reaction vessel; B. Spread 5% of carboxymethyl cellulose (CMC) powder with a content of 99%, a mass concentration of 2%, a viscosity (25℃) of 100 mPa·s, and a degree of substitution DS of 0.9 evenly on the surface of still water. After absorbing water and swelling for 24 hours, start stirring until a uniform carboxymethyl cellulose aqueous solution is obtained. C. Add 39.1% pure water with a pH of 6.0 (25℃) and a conductivity of 10 μs / cm (25℃) to another reactor. D. Add 10% of crystalline fructose with a content of 98.0% (optical rotation method) and a pH value of 4.0 (25℃) to the reaction vessel in step C, and start stirring until completely dissolved; E. Add 5% of 95% polyaspartic acid (PASP) with a pH value (1% aqueous solution, 25°C) of 10.3 to the reaction vessel in step C and stir until completely dissolved. F. Add the mixed solution obtained in step E to the carboxymethyl cellulose aqueous solution that has been stirred evenly. During the addition process, ensure continuous stirring and add slowly. Control the addition process over 2 hours. Finally, add the measured 0.1% isothiazolinone to the reaction vessel and stir evenly to obtain a green, safe and environmentally friendly granulation aid for granular urea.

[0070] The green, safe, and environmentally friendly granulation aid product (granulation aid 9) from Example 9, and the existing granulation aid 0 (37% formaldehyde solution), were used separately in blank urea without granulation aids, with different dosages added, to conduct granulation experiments. The particle strength of the granulated particles was measured, and the particle strength improvement rate was calculated by comparing it with that of the blank urea. The experimental data are shown in Table 9.

[0071] Table 9: Note: The higher the particle strength value, the better the effect of the granulation aid; conversely, the lower the particle strength value, the worse the effect of the granulation aid.

[0072] The formula for calculating the strength improvement rate of urea particles is: Strength improvement rate of urea particles % = (strength of experimental group urea particles - strength of blank urea particles) / strength of blank urea particles * 100%.

Claims

1. A green, safe, and environmentally friendly granulation aid for granular urea, wherein the components, by mass percentage, are characterized as follows: The granulation aid consists of 10%-20% crystalline fructose, 5%-15% carboxymethyl cellulose, 5%-15% polyaspartic acid, 0.1%-0.5% isothiazolinone and 50%-79.9% purified water, with the total of all components being 100%.

2. The green, safe, and environmentally friendly granulation aid for granular urea as described in claim 1, characterized in that... The crystalline fructose is a white crystal or powder at room temperature, and its fructose content is 98.0%–102.0% as determined by polarimetry. The pH value at 25°C is 4.0–7.

0.

3. The green, safe, and environmentally friendly granulation aid for granular urea as described in claim 1, characterized in that... The carboxymethyl cellulose (CMC) is a white granular powder at room temperature, with a content of over 99% and a bulk density of 1.45–1.65 g / cm³. 3 The viscosity of a 2% aqueous solution at 25℃ is 100-140 mPa·s, and the degree of substitution DS≥0.

9.

4. The green, safe, and environmentally friendly granulation aid for granular urea as described in claim 1, characterized in that... The polyaspartic acid (PASP) is a light brown to brown powder at room temperature, with a content of ≥95%, and a pH value of <10.5 for a 1% aqueous solution at 25℃.

5. The green, safe, and environmentally friendly granulation aid for granular urea as described in claim 1, characterized in that... The isothiazolinone is a light brown to brown transparent liquid at room temperature, with a content of 14.0%-15.0%, a pH value of 2.0-4.0 at 25℃, and a density of 1.26g / ml-1.32g / ml at 20℃.

6. The green, safe, and environmentally friendly granulation aid for granular urea as described in claim 1, characterized in that... The purified water is a colorless, odorless, and transparent liquid at room temperature, free of visible impurities, with a pH value of 6.0-8.0 at 25℃ and a conductivity of ≤10μs / cm at 25℃.

7. The preparation method of the green, safe, and environmentally friendly granulation aid for granular urea as described in any one of claims 1-6, characterized in that, The main steps include: (1) First, add some of the pure water in the formula to the reactor, and add the measured carboxymethyl cellulose at room temperature. During the addition process, spread the carboxymethyl cellulose evenly on the water surface. After it absorbs water and swells for 24 hours, start stirring until a uniform carboxymethyl cellulose aqueous solution is obtained. (2) In another clean reactor, stir the remaining 50% of the purified water in the formula with the measured crystalline fructose and polyaspartic acid until completely dissolved; (3) Add the prepared crystalline fructose and polyaspartic acid aqueous solution to the carboxymethyl cellulose aqueous solution that has been stirred evenly. Ensure continuous stirring during the addition process and control the addition process between 1.5 and 2.5 hours. Finally, add the measured amount of isothiazolinone to the reactor and stir evenly to obtain the green, safe and environmentally friendly granulation aid for granular urea.

8. The application of the green, safe, and environmentally friendly granulation aid for granular urea as described in any one of claims 1-6, characterized in that... The granulation aid is injected into the urea production system at a dosage of 0.5–2.0 kg / ton of urea using a pressure pump. The injection point is located at the end of the urea evaporation process to ensure that the granulation aid added to the urea production system can be effectively and thoroughly mixed with the molten urea before granulation.

9. The application of the green, safe, and environmentally friendly granulation aid for granular urea as described in claim 8, characterized in that: If there is a two-stage evaporation process in the urea production system, the granulation aid is added after the first-stage evaporation process.

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