High-efficiency denitration urea exhaust treatment liquid for vehicles and exhaust purification method thereof

Abstract

This invention relates to the field of exhaust gas purification technology, and discloses a high-efficiency denitrification urea exhaust gas treatment fluid for vehicles and its exhaust gas purification method. It is composed of high-purity urea, ultrapure water, a denitrification accelerator, a metal ion chelating agent, a low-temperature anti-crystallization stabilizer, a uniform dispersant, and a system corrosion inhibitor. The high-purity urea content is 31.8%-33.2%, the ultrapure water content is 66.0%-67.8%, and the remaining components total 0.38%-1.44%. The treatment fluid has a density of 1.087 g / cm³-1.093 g / cm³, a refractive index of 1.381-1.384, and a pH value of 9.2-10.8. This invention's treatment fluid exhibits high denitrification efficiency, does not crystallize at low temperatures to prevent pipeline blockage, protects the catalyst, is stable during storage without stratification or precipitation, provides uniform atomization, has strong corrosion resistance, is environmentally friendly with no secondary pollution, and is widely adaptable and easy to mass-produce.

Description

Technical Field

[0001] This invention belongs to the field of exhaust gas purification technology, and particularly relates to a high-efficiency denitrification urea exhaust gas treatment liquid for vehicles and its exhaust gas purification method. Background Technology

[0002] With the continuous growth of motor vehicle ownership, nitrogen oxides in diesel vehicle exhaust have become one of the core pollutants in air pollution. They not only cause environmental problems such as photochemical smog and acid rain, but also seriously damage the human respiratory tract and cardiopulmonary function. Selective catalytic reduction (SCR) technology is currently the mainstream technology for denitrification of diesel vehicle exhaust. This technology involves injecting a urea solution into the exhaust gas, causing it to pyrolyze and produce ammonia. The ammonia then reacts with nitrogen oxides on the catalyst surface, converting harmful pollutants into harmless nitrogen and water. This technology is the core technological support for meeting the National VI emission standards for motor vehicles.

[0003] As the core reducing agent in selective catalytic reduction (SCR) technology, the quality of automotive urea exhaust fluid directly determines the denitrification efficiency and the operational stability of the exhaust treatment system. Currently, most commercially available automotive urea solutions are simply prepared from high-purity urea and deionized water, which presents numerous technical shortcomings in practical applications. At low temperatures, urea components are prone to crystallization, which can clog urea injection pumps, pipelines, and nozzles, leading to injection system failure. Especially in cold northern regions, crystallization has become a major hidden danger affecting the normal operation of vehicles.

[0004] In conventional treatment solutions, the urea pyrolysis and hydrolysis reactions are incomplete, easily producing isocyanate byproducts. This not only reduces ammonia generation efficiency but also results in low denitrification conversion rates, making it impossible to consistently meet stringent emission limits. Furthermore, conventional treatment solutions suffer from insufficient control over raw material purity, leading to excessive levels of metal ions such as calcium, magnesium, sodium, and potassium. These metal ions adhere to the catalyst support surface, causing catalyst poisoning and deactivation, significantly shortening catalyst lifespan.

[0005] In addition, conventional treatment solutions have poor storage stability and are prone to stratification and precipitation when left to stand for a long time, which can clog the filter device. The solution has poor atomization effect and cannot be evenly mixed with the exhaust gas flow, resulting in insufficient local denitrification. Some treatment solutions can also corrode the metal pipes and pumps of the exhaust gas treatment system, reducing the service life of the equipment.

[0006] Existing automotive urea treatment fluids struggle to simultaneously achieve multiple performance characteristics, including low-temperature anti-crystallization, efficient denitrification, storage stability, catalyst protection, and system corrosion prevention. This makes them unsuitable for the all-weather, long-cycle, and high-standard denitrification requirements of diesel vehicles. The industry urgently needs a high-efficiency denitrification automotive urea exhaust treatment fluid with optimized formulation, comprehensive performance, and strong adaptability to overcome the technical limitations of existing products, ensure stable operation of exhaust gas treatment systems, and achieve efficient purification of nitrogen oxides. Summary of the Invention

[0007] To address the shortcomings of existing automotive urea treatment solutions, such as easy crystallization and pipeline blockage at low temperatures, insufficient denitrification conversion, easy catalyst poisoning, easy stratification during storage, system corrosion, and poor atomization effect, this invention provides a highly efficient denitrification automotive urea exhaust gas treatment solution and its exhaust gas purification method.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A high-efficiency denitrification urea exhaust gas treatment fluid for vehicles is composed of high-purity urea, ultrapure water, denitrification accelerator, metal ion chelating agent, low-temperature anti-crystallization stabilizer, uniform dispersant, and system corrosion inhibitor. The mass fraction of high-purity urea is 31.8%-33.2%, the mass fraction of ultrapure water is 66.0%-67.8%, the mass fraction of denitrification accelerator is 0.15%-0.45%, the mass fraction of metal ion chelating agent is 0.08%-0.18%, and the mass fraction of low-temperature anti-crystallization stabilizer is... The concentration of the system corrosion inhibitor is 0.08%-0.28%, the mass fraction of the uniform dispersant is 0.03%-0.09%, and the mass fraction of the system corrosion inhibitor is 0.02%-0.07%. The density of the treatment solution is 1.087 g / cm³-1.093 g / cm³, the refractive index is 1.381-1.384, the conductivity is not greater than 0.7 mS / cm, the pH value is 9.2-10.8, the surface tension is 35 mN / m-45 mN / m, and the median particle size of the atomized particles is 20 μm-50 μm.

[0009] Preferably, the treatment liquid undergoes a continuous pyrolysis and hydrolysis reaction of urea in the high-temperature environment of automobile exhaust; the reaction temperature range is 180℃-600℃, the pyrolysis and hydrolysis conversion rate is not less than 99%, and the generated ammonia gas is uniformly dispersed in the exhaust gas flow, providing a stable active medium for selective catalytic reduction.

[0010] Preferably, the reaction also includes a selective catalytic reduction reaction between ammonia and nitrogen oxides in the exhaust gas on the surface of the SCR catalyst; the reaction space velocity is 10000 h⁻¹. -1 Up to 50000h -1 Nitrogen oxides are converted into harmless nitrogen gas and water, and the denitrification process produces no secondary pollution.

[0011] Preferably, the high-purity urea has a purity of not less than 99.95%, a median particle size of urea particles of 100μm-300μm, and a melting point of 132℃-135℃; the high-purity urea contains not more than 0.25% biuret, not more than 0.08% formaldehyde, not more than 0.01% insoluble residue, and the total content of calcium, magnesium, sodium, and potassium ions is not more than 3mg / kg, and the total content of heavy metal ions is not more than 0.5mg / kg.

[0012] Preferably, the resistivity of the ultrapure water is not less than 18.25 MΩ·cm, the total organic carbon (TOC) content is not greater than 5 μg / L, and the pH value is 6.5-7.5; the number of suspended particles with a particle size greater than 0.1 μm in the ultrapure water is not greater than 8 particles / mL, the total bacterial count is not greater than 5 cfu / mL, the total metal ion content is not greater than 0.5 mg / kg, and the chloride ion and sulfate ion content are both not greater than 0.1 mg / kg.

[0013] Preferably, the denitrification accelerator is a compound of diethanolamine and triisopropanolamine, the metal ion chelating agent is a compound of disodium EDTA and aminotrimethylenephosphonic acid, the low-temperature anti-crystallization stabilizer is a compound of propylene glycol, glycerol and ethylene glycol monobutyl ether, the uniform dispersant is a compound of nonionic polyoxyethylene ether and fatty acid polyglycerol ester, and the system corrosion inhibitor is a compound of benzotriazole and imidazoline quaternary ammonium salt; all additives are food-grade environmentally friendly components, free of halogens, phosphorus, and toxic volatile components.

[0014] Preferably, the treatment solution exhibits no crystallization after standing for 72 hours at -25°C, and its low-temperature kinematic viscosity is no greater than 5 mm² / s; the static storage stability of the treatment solution at room temperature is no less than 96 hours, and it exhibits no stratification, precipitation, turbidity, or discoloration after storage; the compatibility rate between the treatment solution and the SCR catalyst carrier is no less than 99.5%, the nitrogen oxide denitrification efficiency is no less than 96%, and the corrosion rate on metal components of the automotive exhaust gas treatment system is no greater than 0.01 mm / a.

[0015] Preferably, it includes the following steps: S1 delivers ultrapure water to a closed stainless steel stirred reactor, introduces nitrogen to replace the air in the reactor, turns on the stirring device, sets the stirring speed to 300r / min-600r / min, adds high-purity urea to the reactor at a uniform rate, and stirs at a constant temperature until the urea is completely dissolved to obtain a transparent urea base solution. S2. Metal ion chelating agent and low-temperature anti-crystallization stabilizer are added sequentially to urea base solution, the temperature is raised to 35℃-55℃, and the mixture is stirred continuously for 25min-50min to obtain a homogeneous mixed base solution. S3 adds a denitrification accelerator, a uniform dispersant and a system corrosion inhibitor to the mixed base liquid, and stirs at a constant temperature for 20-40 minutes to obtain a crude treatment liquid; S4 sequentially passes the crude treatment liquid through a three-stage precision filtration device with filtration accuracies of 1μm, 0.2μm, and 0.1μm, respectively, to remove suspended impurities and agglomerated particles, thus producing a high-efficiency denitrification vehicle urea exhaust gas treatment liquid.

[0016] Preferably, the urea dissolution process in S1 is a closed, constant-temperature dissolution process, with the dissolution temperature controlled between 25℃ and 45℃. During the dissolution process, there is no urea volatilization, no water evaporation, and no introduction of external impurities. Urea molecules and water molecules undergo a directional hydration and dispersion reaction, and the hydration products are uniformly dispersed in the aqueous phase system, ensuring the homogeneity of the treated liquid.

[0017] Preferably, it includes the following steps: S1 injects the treatment liquid into the vehicle's exhaust pipe in a metered manner through an electronically controlled urea injection pump. The injection pressure is set to 0.6MPa-1.1MPa, the atomized particle size is controlled to 20μm-50μm, and the exhaust gas temperature in the injection area is controlled to 200℃-550℃. The S2 treatment fluid rapidly completes pyrolysis and hydrolysis reactions at high temperature in the exhaust gas, and the generated ammonia gas is fully mixed with the exhaust gas on the surface of the SCR catalyst support. S3 ammonia undergoes a selective catalytic reduction reaction with nitrogen oxides in the exhaust gas, converting the nitrogen oxides into nitrogen and water, thus completing the denitrification and purification of the exhaust gas.

[0018] The present invention has the following beneficial effects: This invention improves the efficiency of urea pyrolysis and hydrolysis conversion through the synergistic effect of multiple additives, making the denitrification reaction more complete and thorough, and quickly converting nitrogen oxides in exhaust gas into harmless substances, thereby continuously and stably achieving high-standard exhaust gas purification.

[0019] The anti-crystallization component in the treatment fluid can inhibit the low-temperature aggregation and precipitation of urea molecules, thereby preventing crystallization blockage in pipelines, nozzles and jet pumps from the source, improving the system's operational stability in low-temperature environments, and making it suitable for use in all regions and climates.

[0020] Metal ion chelating agents effectively complex with trace metal impurities in the solution, preventing impurities from depositing on the catalyst surface, preventing catalyst poisoning and deactivation, completely protecting the active structure of the catalyst support, and extending the overall service life of the catalyst.

[0021] The compound dispersant improves the uniformity of the system, ensuring that the components are stably dispersed over a long period of time. It does not separate, precipitate, or become turbid during static storage. At the same time, it optimizes the atomization performance, allowing the droplets to mix fully with the exhaust gas flow, ensuring that the denitrification reaction is carried out uniformly throughout the entire process.

[0022] Specialized corrosion inhibitors form a protective film on the surface of the system's metal components, reducing the corrosion of pipelines, pumps, and valves by the solution, reducing equipment wear, and improving the operational safety and durability of the exhaust gas treatment system.

[0023] The treatment solution uses environmentally friendly compound additives, which are free of halogens, phosphorus and toxic volatile components. There are no harmful byproducts or secondary pollution throughout the reaction process, which meets the requirements of green and environmentally friendly emissions and is suitable for high-standard purification scenarios.

[0024] The preparation process is closed and controllable, the components are fully dissolved and dispersed, impurity particles are removed by filtration, the finished product quality is uniform and stable, and continuous industrial mass production is achieved. It has good compatibility with various diesel vehicle exhaust treatment systems and has a wide range of applications. Attached Figure Description

[0025] Figure 1 This invention provides a flow chart for preparing a high-efficiency denitrification vehicle urea exhaust gas treatment fluid; Figure 2 This is a comparison chart of the denitrification efficiency of each group of samples proposed in this invention; Figure 3 This is a graph showing the relationship between stirring speed and denitrification efficiency as proposed in this invention; Figure 4 This is a comprehensive comparison chart of the core performance of Embodiment 3 and Comparative Example 1 proposed in this invention; Figure 5 This is a graph showing the relationship between filtration accuracy and residual impurities in the treated liquid, as proposed in this invention. Detailed Implementation

[0026] This specific embodiment involves a complete preparation process conducted in a Class 10,000 cleanroom, with the ambient temperature controlled between 22℃ and 26℃ and the relative humidity between 40% and 60%. The entire process utilizes closed-loop production equipment to prevent contamination from external impurities. This invention uses high-purity urea and ultrapure water as the base materials, compounded with a specialized denitrification accelerator, metal ion chelating agent, low-temperature anti-crystallization stabilizer, uniform dispersant, and system corrosion inhibitor. Through a standardized process of closed-loop constant-temperature dissolution, multi-stage stirring and compounding, and three-stage precision filtration, it overcomes the technical shortcomings of traditional automotive urea treatment solutions, such as low-temperature crystallization, low denitrification efficiency, catalyst poisoning, unstable storage, and system corrosion. This embodiment includes three preferred examples and one comparative example of a conventional process. All preparation steps are fully detailed, process parameters are comprehensively refined, and the reaction process is clearly defined.

[0027] Core chemical reaction formula: Urea molecule hydration and dispersion reaction: CO(NH2)2+nH2O CO(NH2)2∙nH2O Urea pyrolysis reaction: CO(NH2)2 NH3↑+HNCO Isocyanate hydrolysis reaction: HNCO + H2O NH3↑+CO2↑ Selective catalytic reduction of nitrogen oxides: 4NH3 + 4NO + O2 4N2 + 6H2O 8NH3+6NO2 7N2+12H2O Metal ion coordination complexation reaction: M n+ +L [ML] n+ (where M is the formula) n+ (These are metal ions such as calcium, magnesium, sodium, and potassium, with L being a chelating ligand.) Example 1 S1. Pour ultrapure water with a resistivity of not less than 18.25 MΩ·cm into a closed stainless steel stirred reactor. Turn on the nitrogen purging device and continuously purge nitrogen for five minutes to replace the air inside the reactor. Start the stirring device and set the stirring speed to 300 r / min. Add high-purity urea with a mass purity of not less than 99.95% into the reactor at a uniform rate. Control the dissolution temperature at 25℃ and continue stirring until the urea is completely dissolved, forming a transparent and homogeneous urea-based solution.

[0028] S2. Add the metal ion chelating agent, which is a mixture of disodium EDTA and aminotrimethylenephosphonic acid, and the low-temperature anti-crystallization stabilizer, which is a mixture of propylene glycol, glycerol and ethylene glycol monobutyl ether, to the urea base solution in sequence. Heat to 35°C and stir continuously for 25 minutes to fully integrate the additives with the urea base solution to obtain a homogeneous mixed base solution.

[0029] S3. Add a denitrification accelerator composed of diethanolamine and triisopropanolamine, a uniform dispersant composed of nonionic polyoxyethylene ether and fatty acid polyglycerol ester, and a system corrosion inhibitor composed of benzotriazole and imidazoline quaternary ammonium salt to the mixed base liquid. Keep the temperature at 35°C and stir for 20 minutes to fully disperse all components and obtain the crude treatment liquid.

[0030] S4. The crude treatment liquid is passed through a three-stage precision filtration device in sequence. The first stage has a filtration precision of 1μm, the second stage has a filtration precision of 0.2μm, and the third stage has a filtration precision of 0.1μm. Suspended impurities and agglomerated particles are removed step by step to obtain a high-efficiency denitrification vehicle urea exhaust gas treatment liquid.

[0031] S5. The prepared high-efficiency denitrification vehicle urea exhaust gas treatment fluid is quantitatively injected into the diesel vehicle exhaust pipe through an electronically controlled urea injection pump. The injection pressure is set to 0.6MPa, the median atomization particle size is controlled to be 20μm, and the exhaust gas temperature in the injection area is maintained at 200℃. The treatment fluid completes the pyrolysis and hydrolysis reaction under the high temperature environment of the exhaust gas, and the generated ammonia gas is fully mixed with the exhaust gas and enters the SCR catalyst. Selective catalytic reduction reaction occurs on the catalyst surface, converting nitrogen oxides in the exhaust gas into nitrogen gas and water, thus completing the exhaust gas denitrification and purification.

[0032] Example 2 S1. Pour ultrapure water with a resistivity of not less than 18.25 MΩ·cm into a closed stainless steel stirred reactor. Turn on the nitrogen purging device and continuously purge nitrogen for six minutes to replace the air inside the reactor. Start the stirring device and set the stirring speed to 450 r / min. Add high-purity urea with a mass purity of not less than 99.95% into the reactor at a uniform rate. Control the dissolution temperature at 35℃ and continue stirring until the urea is completely dissolved, forming a transparent and homogeneous urea-based solution.

[0033] S2. Add the metal ion chelating agent, which is a mixture of disodium EDTA and aminotrimethylenephosphonic acid, and the low-temperature anti-crystallization stabilizer, which is a mixture of propylene glycol, glycerol and ethylene glycol monobutyl ether, to the urea base solution in sequence. Heat the solution to 45°C and stir continuously for 38 minutes to fully integrate the additives with the urea base solution and obtain a homogeneous mixed base solution.

[0034] S3. Add a denitrification accelerator composed of diethanolamine and triisopropanolamine, a uniform dispersant composed of nonionic polyoxyethylene ether and fatty acid polyglycerol ester, and a system corrosion inhibitor composed of benzotriazole and imidazoline quaternary ammonium salt to the mixed base liquid. Maintain a constant temperature of 45°C and stir for 30 minutes to fully disperse all components and obtain a crude treatment liquid.

[0035] S4. The crude treatment liquid is passed through a three-stage precision filtration device in sequence. The first stage has a filtration precision of 1μm, the second stage has a filtration precision of 0.2μm, and the third stage has a filtration precision of 0.1μm. Suspended impurities and agglomerated particles are removed step by step to obtain a high-efficiency denitrification vehicle urea exhaust gas treatment liquid.

[0036] S5. The prepared high-efficiency denitrification vehicle urea exhaust gas treatment fluid is quantitatively injected into the diesel vehicle exhaust pipe through an electronically controlled urea injection pump. The injection pressure is set to 0.8 MPa, the median atomization particle size is controlled to be 35 μm, and the exhaust gas temperature in the injection area is maintained at 380℃. The treatment fluid completes the pyrolysis and hydrolysis reaction under the high temperature environment of the exhaust gas, and the generated ammonia gas is fully mixed with the exhaust gas and enters the SCR catalyst. Selective catalytic reduction reaction occurs on the catalyst surface, converting nitrogen oxides in the exhaust gas into nitrogen gas and water, thus completing the exhaust gas denitrification and purification.

[0037] Example 3 S1. Pour ultrapure water with a resistivity of not less than 18.25 MΩ·cm into a closed stainless steel stirred reactor. Turn on the nitrogen purging device and continuously purge nitrogen for seven minutes to replace the air inside the reactor. Start the stirring device and set the stirring speed to 600 r / min. Add high-purity urea with a mass purity of not less than 99.95% into the reactor at a uniform rate. Control the dissolution temperature at 45℃ and continue stirring until the urea is completely dissolved, forming a transparent and homogeneous urea-based solution.

[0038] S2. Add the metal ion chelating agent, which is a mixture of disodium EDTA and aminotrimethylenephosphonic acid, and the low-temperature anti-crystallization stabilizer, which is a mixture of propylene glycol, glycerol and ethylene glycol monobutyl ether, to the urea base solution in sequence. Heat to 55°C and stir continuously for 50 minutes to fully integrate the additives with the urea base solution to obtain a homogeneous mixed base solution.

[0039] S3. Add a denitrification accelerator composed of diethanolamine and triisopropanolamine, a uniform dispersant composed of nonionic polyoxyethylene ether and fatty acid polyglycerol ester, and a system corrosion inhibitor composed of benzotriazole and imidazoline quaternary ammonium salt to the mixed base liquid. Maintain a constant temperature of 55°C and stir for 40 minutes to fully disperse all components and obtain a crude treatment liquid.

[0040] S4. The crude treatment liquid is passed through a three-stage precision filtration device in sequence. The first stage has a filtration precision of 1μm, the second stage has a filtration precision of 0.2μm, and the third stage has a filtration precision of 0.1μm. Suspended impurities and agglomerated particles are removed step by step to obtain a high-efficiency denitrification vehicle urea exhaust gas treatment liquid.

[0041] S5. The prepared high-efficiency denitrification vehicle urea exhaust gas treatment fluid is quantitatively injected into the diesel vehicle exhaust pipe through an electronically controlled urea injection pump. The injection pressure is set to 1.1 MPa, the median atomization particle size is controlled to be 50 μm, and the exhaust gas temperature in the injection area is maintained at 550℃. The treatment fluid completes the pyrolysis and hydrolysis reaction under the high temperature environment of the exhaust gas, and the generated ammonia gas is fully mixed with the exhaust gas and enters the SCR catalyst. Selective catalytic reduction reaction occurs on the catalyst surface, converting nitrogen oxides in the exhaust gas into nitrogen gas and water, thus completing the exhaust gas denitrification and purification.

[0042] Comparative Example 1 S1. Ordinary deionized water is delivered to an open-type stirred reactor without nitrogen purging or control of environmental impurities. The stirring device is started, and the stirring speed is set to 150 r / min. Industrial-grade urea is added into the reactor and stirred at room temperature until the urea dissolves, forming a simple urea-based solution.

[0043] S2. Without adding metal ion chelating agents, low-temperature anti-crystallization stabilizers, uniform dispersants, and system corrosion inhibitors, the urea base solution is simply stirred for 15 minutes to obtain a crude liquid without compounded additives.

[0044] S3. It does not perform multi-stage precision filtration, but only performs simple filtration through a single-layer filter screen. The filtration accuracy is 5μm, which cannot remove tiny impurities and agglomerated particles.

[0045] S4. After filtration, it is directly filled to produce conventional automotive urea treatment solution. There are no additives, no precision purification process, and no low-temperature stability and corrosion protection design.

[0046] S5. The prepared conventional automotive urea treatment solution is injected into the exhaust pipe using a conventional injection method. Without precise control of injection pressure, atomization particle size and reaction temperature, the urea solution is not fully pyrolyzed and hydrolyzed. After being unevenly mixed with the exhaust gas, it enters the SCR catalytic converter for catalytic reduction reaction to complete the conventional exhaust gas purification.

[0047] Table 1 Comparison of components and process parameters between Examples 1-3 and Comparative Example 1 Explanation of the table: This table fully presents the differences in components, raw materials, and preparation process parameters between Examples 1-3 and Comparative Example 1. Examples 1-3 strictly adhere to the defined standards, using high-resistivity ultrapure water and ultra-high-purity urea, with nitrogen gas used throughout to isolate impurities, gradient-set stirring speed and dissolution temperature, complete addition of functional additives, and deep purification achieved through three-stage precision filtration. Comparative Example 1 uses ordinary deionized water and industrial-grade urea, without nitrogen protection, with coarse stirring parameters, no added functional additives, and only a simple single-layer filtration. The table visually verifies the refined raw material control and process design of this invention, confirming that high-purity raw materials, functional additives, and closed purification processes are the core of improving the quality of the treated solution, providing standardized parameter basis for industrial production, and highlighting the upgrade of this invention compared to traditional processes.

[0048] Table 2 Comparison of Product Performance between Examples 1-3 and Comparative Example 1 Table Explanation: This table compares the core application performance of the products prepared in Examples 1-3 with those in Comparative Example 1. Examples 1-3, through defined component formulation and standardized processes, exhibit excellent low-temperature anti-crystallization performance, consistently achieving the required denitrification efficiency. The metal ion chelating component effectively blocks catalyst poisoning, resulting in no stratification or precipitation during long-term storage. The corrosion inhibitor significantly reduces corrosion of system metal components, and uniform atomization improves reaction efficiency. Example 3 achieves optimal overall performance due to the optimal range of process parameters such as stirring, temperature, and filtration. Comparative Example 1, lacking functional additives and precise process assurance, is prone to crystallization and pipeline blockage in low-temperature environments, leading to incomplete denitrification conversion. Raw material impurities easily cause catalyst deactivation, resulting in stratification and deterioration during storage, strong corrosiveness to the system, and poor atomization effect. The table fully verifies that this invention can solve the technical defects of traditional automotive urea treatment fluid, taking into account multiple properties such as low-temperature stability, efficient denitrification, catalyst protection, storage stability, and system corrosion prevention, demonstrating significant technological advancement and industrial application value.

[0049] refer to Figure 2This bar chart visually presents the differences in denitrification efficiency between the three sets of examples, comparative examples, and the national standard benchmark. Examples 1-3 utilize the invented compound additives and standardized preparation processes. The denitrification accelerator significantly improves the pyrolysis conversion efficiency of urea. Combined with uniform atomization and thorough mixing, the denitrification efficiency is far higher than the industry standard and continues to improve with optimization of process parameters. Comparative Example 1 uses a traditional simple formula and extensive process without the support of denitrification additives. Urea decomposition is insufficient, and the denitrification efficiency is significantly lower than the standard value. The chart clearly verifies that this invention achieves efficient conversion of nitrogen oxides through the synergistic effect of multiple additives and closed-loop purification production, stably meeting the National VI emission standards. It represents an iterative upgrade of traditional products in terms of core performance, providing reliable product support for efficient purification of diesel vehicle exhaust, and also visually demonstrating the technological advancement of this invention.

[0050] refer to Figure 3 This line graph is drawn based on the actual stirring speed process parameters of the embodiments and comparative examples of the present invention, intuitively reflecting the influence of stirring speed on the denitrification efficiency of automotive urea exhaust gas treatment solution. Comparative Example 1 uses a low stirring speed of 150 r / min, resulting in uneven mixing of components and the inability of the additives to fully exert their synergistic effect, with a denitrification efficiency of only 82.3%. As the stirring speed is increased to 300 r / min in Example 1 and 450 r / min in Example 2, the urea and various functional additives are more evenly dispersed, and the denitrification efficiency gradually increases. At a stirring speed of 600 r / min in Example 3, the system homogeneity reaches its optimal level, and the peak denitrification efficiency is 98.5%. When the stirring speed is excessively increased to 750 r / min, the bubbles generated by stirring will disrupt the stability of the solution, leading to a slight decrease in atomization and reaction effects, and a slight decline in denitrification efficiency. The curve not only verifies the rationality of the gradient stirring process of the present invention, but also proves that process parameter optimization is the key to improving denitrification performance. It fully reflects the core innovation of the invention in achieving efficient denitrification through refined preparation process, provides intuitive data support for parameter setting in industrial production, and highlights the technical advantages of the present invention compared with traditional extensive processes.

[0051] refer to Figure 4 This radar chart illustrates the core performance gap between the optimal embodiment and traditional process products, intuitively demonstrating the comprehensive technical advantages of the present invention. Example 3, through the synergistic effect of the invented formula compound, low-temperature anti-crystallization components, chelating protectants, corrosion inhibitors, and dispersants, achieves high scores in all five core performance aspects, exhibiting a full and balanced performance profile suitable for diesel vehicle exhaust treatment scenarios. Comparative Example 1, lacking functional additives and precision processing, suffers from easy low-temperature crystallization, unstable storage, poor corrosion resistance and atomization performance, and only meets basic denitrification performance standards, exhibiting serious defects in its performance profile. The charts fully verify that the present invention simultaneously solves five major industry problems of traditional automotive urea treatment fluid: low-temperature crystallization, inefficient denitrification, catalyst poisoning, unstable storage, and system corrosion, achieving a unity of functionality, stability, and durability, possessing market application value and technological breakthrough significance.

[0052] refer to Figure 5 This scatter plot reveals the core correlation between filtration precision and residual impurities in the treated fluid, verifying the scientific validity of the three-stage precision filtration process of this invention. A filtration precision of 5.0 μm, corresponding to the simple filtration in Example 1, cannot remove tiny metal ions and suspended particles, resulting in high residual impurities and easily causing catalyst poisoning and pipeline blockage. As the filtration precision increases to 1.0 μm and 0.2 μm, the residual impurities decrease significantly, reaching extremely low levels after meeting the filtration standards of this embodiment. The three-stage progressive filtration process employed in this invention removes large particles, microparticles, and ultrafine impurities step by step, fundamentally preventing equipment malfunctions and catalyst deactivation caused by impurities. This chart visually demonstrates that precision filtration is the core step in improving the purity of the treated fluid, providing a standardized solution for the purification production of automotive urea treated fluid and effectively extending the service life of the exhaust gas treatment system.

[0053] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A high-efficiency denitrification urea exhaust gas treatment fluid for vehicles, characterized in that, It is composed of high-purity urea, ultrapure water, denitrification accelerator, metal ion chelating agent, low-temperature anti-crystallization stabilizer, uniform dispersant, and system corrosion inhibitor; the mass fraction of high-purity urea is 31.8%-33.2%, the mass fraction of ultrapure water is 66.0%-67.8%, the mass fraction of denitrification accelerator is 0.15%-0.45%, the mass fraction of metal ion chelating agent is 0.08%-0.18%, and the mass fraction of low-temperature anti-crystallization stabilizer is... The concentration of the solvent is 0.08%-0.28%, the mass fraction of the uniform dispersant is 0.03%-0.09%, and the mass fraction of the system corrosion inhibitor is 0.02%-0.07%. The density of the treatment solution is 1.087 g / cm³-1.093 g / cm³, the refractive index is 1.381-1.384, the conductivity is not greater than 0.7 mS / cm, the pH value is 9.2-10.8, and the surface tension is 35 mN / m-45 mN / m.

2. The high-efficiency denitrification urea exhaust gas treatment fluid for vehicles according to claim 1, characterized in that, It also includes the continuous pyrolysis and hydrolysis of urea in the high-temperature environment of automobile exhaust.

3. The high-efficiency denitrification urea exhaust gas treatment fluid for vehicles according to claim 1, characterized in that, It also includes the selective catalytic reduction reaction of ammonia and nitrogen oxides in the exhaust gas on the surface of the SCR catalyst, in which nitrogen oxides are converted into harmless nitrogen and water, and the denitrification process has no secondary pollution.

4. The high-efficiency denitrification urea exhaust gas treatment fluid for vehicles according to claim 1, characterized in that, The purity of high-purity urea shall not be less than 99.95%; the mass fraction of biuret in high-purity urea shall not be greater than 0.25%, the mass fraction of formaldehyde shall not be greater than 0.08%, the mass fraction of insoluble residue shall not be greater than 0.01%, the total content of the four metal ions of calcium, magnesium, sodium and potassium shall not be greater than 3 mg / kg, and the total content of heavy metal ions shall not be greater than 0.5 mg / kg.

5. The high-efficiency denitrification urea exhaust gas treatment fluid for vehicles according to claim 1, characterized in that, The resistivity of ultrapure water is not less than 18.25 MΩ·cm, the total organic carbon (TOC) content is not greater than 5 μg / L, and the pH value is 6.5-7.

5. The number of suspended particles with a diameter greater than 0.1 μm in ultrapure water is not greater than 8 per mL, the total bacterial count is not greater than 5 cfu / mL, the total metal ion content is not greater than 0.5 mg / kg, and the chloride and sulfate ion contents are both not greater than 0.1 mg / kg.

6. The high-efficiency denitrification urea exhaust gas treatment fluid for vehicles according to claim 1, characterized in that, The denitrification accelerator is a compound of diethanolamine and triisopropanolamine; the metal ion chelating agent is a compound of disodium EDTA and aminotrimethylenephosphonic acid; the low-temperature anti-crystallization stabilizer is a compound of propylene glycol, glycerol and ethylene glycol monobutyl ether; the uniform dispersant is a compound of nonionic polyoxyethylene ether and fatty acid polyglycerol ester; and the system corrosion inhibitor is a compound of benzotriazole and imidazoline quaternary ammonium salt.

7. The high-efficiency denitrification urea exhaust gas treatment fluid for vehicles according to claim 1, characterized in that, The treatment solution shows no crystallization after standing for 72 hours at -25℃, and its low-temperature kinematic viscosity is no greater than 5 mm² / s; the static storage stability of the treatment solution at room temperature is no less than 96 hours; the compatibility rate between the treatment solution and the SCR catalyst carrier is no less than 99.5%; the nitrogen oxide denitrification efficiency is no less than 96%; and the corrosion rate on metal parts of the automotive exhaust gas treatment system is no greater than 0.01 mm / a.

8. The high-efficiency denitrification urea exhaust gas treatment fluid for vehicles according to claim 1, characterized in that, The preparation method of the exhaust gas treatment fluid includes the following steps: S1. Ultrapure water is transported to a closed stainless steel stirred reactor, nitrogen is introduced to replace the air in the reactor, the stirring device is turned on, and high-purity urea is added to the reactor at a uniform rate. The reactor is stirred at a constant temperature until the urea is completely dissolved to obtain a transparent urea base solution. S2. Add metal ion chelating agent and low temperature anti-crystallization stabilizer to urea base solution in sequence, heat to 35℃-55℃, and stir continuously for 25min-50min to obtain a homogeneous mixed base solution. S3. Add denitrification accelerator, uniform dispersant and system corrosion inhibitor to the mixed base liquid, stir at constant temperature for 20min-40min to obtain crude treatment liquid; S4. Pass the crude treatment liquid through a three-stage precision filtration device to obtain a high-efficiency denitrification vehicle urea exhaust gas treatment liquid.

9. The preparation method of a high-efficiency denitrification vehicle urea exhaust gas treatment fluid according to claim 8, characterized in that, The urea dissolution process in S1 is a closed, constant-temperature dissolution process, with the dissolution temperature controlled between 25℃ and 45℃. During the dissolution process, there is no urea volatilization, no water evaporation, and no introduction of external impurities. Urea molecules undergo a directional hydration and dispersion reaction with water molecules, and the hydration products are uniformly dispersed in the aqueous phase system.

10. A method for purifying exhaust gas based on high-efficiency denitrification automotive urea exhaust gas treatment fluid, used to purify the exhaust gas generated by the high-efficiency denitrification automotive urea exhaust gas treatment fluid according to any one of claims 1-9, characterized in that, Includes the following steps: S1. The treatment liquid is quantitatively injected into the exhaust pipe of the automobile through an electronically controlled urea injection pump. The injection pressure is set to 0.6MPa-1.1MPa, the atomized particle size is controlled to 20μm-50μm, and the exhaust gas temperature in the injection area is controlled to 200℃-550℃. S2. The treatment liquid rapidly completes the pyrolysis and hydrolysis reaction at high temperature in the exhaust gas, and the generated ammonia gas is fully mixed with the exhaust gas on the surface of the SCR catalyst support. S3. Ammonia reacts with nitrogen oxides in the exhaust gas via a selective catalytic reduction reaction, converting the nitrogen oxides into nitrogen and water, thus completing the denitrification and purification of the exhaust gas.

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