Process for preparing high-concentration nitric acid by double-pressurization dilute nitric acid method

Abstract

The invention discloses a process for preparing high-concentration nitric acid by a double-pressurization dilute nitric acid method, and relates to the technical field of chemical engineering, and the process comprises the following preparation steps: S1, inputting mixed gas into a gasification furnace according to a proportional algorithm model, S2, inputting first dilute nitric acid into a nitric oxide separator which is provided with a filtering module with decomposition capability, s3, the tail gas is detected through a detector, after heat exchange through a tail gas preheater, nitric oxide mixed gas enters a high-pressure reaction water condenser, and second dilute nitric acid is generated; and S4, the tail gas obtained after absorption reaction is discharged from the top of the absorption tower and enters a tail gas separator. The method greatly improves the yield of high-concentration nitric acid.

Description

Technical Field

[0001] The invention relates to the technical field of high-concentration nitric acid preparation, and more specifically to a process for preparing high-concentration nitric acid by a double-pressurized dilute nitric acid method. Background Art

[0002] The double-pressurized dilute nitric acid method is a method for preparing high-concentration acid, which mainly increases the concentration of the product by applying additional pressure during the reaction and using a lower concentration of acid. This method is widely used in chemical production. For example, in the production process of nitric acid, the double-pressurized dilute acid method is used to increase the concentration of nitric acid, which has important industrial application value.

[0003] Nitric acid has a wide range of uses and is often used to produce a series of nitrate nitrogen fertilizers. Since nitric acid is both oxidizing and acidic, it is also used to refine metals, etc. The nitric acid production process is generally divided into five types according to pressure, namely normal pressure method, full medium pressure method, comprehensive method, full high pressure method and double pressure method. The normal pressure method and comprehensive method are early nitric acid production processes with small production capacity, high consumption, heavy pollution and low acid concentration, and have been eliminated. The full medium pressure method and the full high pressure method are methods in which both oxidation and absorption are carried out under pressure, which improves the production intensity, and the process is simple and the investment is small, but the production intensity is still low, the loss is large, and NO in the tail gas is high. x The content is still above 2000ppmW, and treatment is required to meet the emission standards. The double pressure method is the most commonly used nitric acid production process. Its ammonia loss and catalyst consumption are low, the absorption rate is high, the nitric acid produced is high in concentration and strength, and the NO in the tail gas is x The content is low and meets international emission standards. In the existing technology, the double-pressurized dilute acid method requires the use of special chemical reactions to maintain a high-pressure environment. These chemical reactions are costly and have extremely strict material requirements to ensure normal operation and corrosion-free operation under high pressure. In addition, maintaining a high-pressure environment requires more energy, such as power consumption of compressors, which may increase production costs. Operating under high-pressure environments requires higher safety standards and more professional techniques, which makes the production process more complicated and places higher technical requirements on operators. Under high pressure, the rate and path of chemical reactions may change, which requires precise control of reaction conditions, including temperature, pressure, and the molar ratio of reactants, and existing technologies have weak monitoring capabilities.

[0004] In the prior art, for example, application No. 201110323653.X discloses a high-concentration dilute nitric acid production process, which is to produce dilute nitric acid and concentrated nitric acid together, using a double-pressurized dilute nitric acid device, improving the production of super-azeotropic nitric acid with a mass concentration greater than 68.4%, and then using super-azeotropic nitric acid distillation and rectification technology to produce concentrated nitric acid with a mass concentration greater than 98%. Although this method can also improve the production capacity of concentrated nitric acid to a certain extent, the production cost of this process is high, the output is low, and it is difficult to evaluate or calculate different parameters or chemical component parameters during the preparation process, and it does not reduce NO in the tail gas very well. x The content. Summary of the invention

[0005] In view of the shortcomings of the above-mentioned technology, the present invention discloses a process for preparing high-concentration nitric acid by double-pressurized dilute nitric acid method, which improves NO in tail gas by artificial intelligence calculation method. x The content and calculation of different parameters can be effectively evaluated and calculated during the preparation process, greatly improving the production efficiency of high-concentration nitric acid.

[0006] The present invention adopts the following technical solutions: A process for preparing high-concentration nitric acid by a double-pressurized dilute nitric acid method, comprising the following preparation steps: S1. A mixed gas is input into the gasifier according to a proportional algorithm model, wherein the mixed gas contains at least ammonia, oxygen and nitrogen. After applying a pressure of 0.5 MPa, the generated nitrogen oxide mixed gas is extremely rapidly cooled under a pressure of 0.1 MPa to condense the compressed nitrogen oxide mixed gas at a dew point temperature. A cooling temperature difference detection module is provided in the gasifier, and when a maximum temperature difference is detected, a first dilute nitric acid and a cooled nitrogen oxide mixed gas are output; the concentration of the first dilute nitric acid is between 28% and 34%, and the temperature is between 38°C. S2, inputting the first dilute nitric acid into a nitrogen oxide separator, wherein the nitrogen oxide separator is provided with a filtering module with decomposition capability, wherein the first dilute nitric acid contacts with the cooled nitrogen oxide mixed gas in an absorption tower, and after a chemical reaction, the nitrogen oxide is converted into a compound soluble in acid, and then enters a tail gas preheater; S3, the tail gas is detected by a detector, and after heat exchange in a tail gas preheater, the nitrogen oxide mixed gas enters a high-pressure reaction water condenser to generate a second dilute nitric acid, and the second dilute nitric acid and the nitrogen oxide mixed gas are separated by a gas-liquid separator with a detection function, and the separated second dilute nitric acid passes through a nitrogen oxide separator with a decomposition function, and then is pumped into an absorption tower through a dilute acid pump. The absorption tower has a total of 64 plates, and the separated nitrogen oxide mixed gas enters the absorption tower from the bottom, and countercurrently contacts with the process water added to the top of the absorption tower to generate a third dilute nitric acid. The third dilute nitric acid is bleached by hot air from a bleaching tower to remove the nitrogen oxide gas dissolved in the acid, and then cooled by an acid cooler and sent to a finished acid storage tank; S4. The tail gas after the absorption reaction goes out from the top of the absorption tower and goes to the tail gas separator.

[0007] As a further technical solution of the present invention, in step S1, the proportional algorithm model includes a PLC controller and a proportional parameter setting module, a ratio calculation module and a gas output module connected to the PLC controller, wherein: The PLC controller is responsible for executing the control program, monitoring the process variables, and controlling the actuators according to the preset algorithms and logic; The proportional parameter setting module is responsible for setting and adjusting the parameters of the proportional algorithm, optimizing the control effect by adjusting the proportional coefficient, integral time and differential time, so that the model response is more stable and accurate; The ratio calculation module calculates the required ratio of ammonia, oxygen and nitrogen according to the preset ratio requirements and real-time monitoring data; The gas output module controls the output amount of the gas according to the instruction of the PLC controller.

[0008] As a further technical solution of the present invention, in step S1, the cooling temperature difference detection module includes a temperature control module and a temperature sensing module, a temperature calculation module, a temperature early warning module and a temperature adaptive adjustment module connected to the temperature control module.

[0009] As a further technical solution of the present invention, in step S1, The generated nitrogen oxide mixed gas is rapidly oxidized under a pressure of 0.5MPa to form unstable nitrate ions. The nitrogen content in the nitric acid increases through 2.5 hours of uninterrupted continuous output. The gas is then pressurized to 2MPa to further promote the formation of nitrate ions. The gas is rapidly cooled within 3 seconds and the cooled mixed gas is output.

[0010] As a further technical solution of the present invention, in step S2, the filter module with decomposition ability realizes the treatment of tail gas through vanadium pentoxide.

[0011] As a further technical solution of the present invention, in step S2, the nitrogen oxide separator at least includes activated carbon, molecular sieve, and metal organic framework membrane.

[0012] As a further technical solution of the present invention, in step S2, the detector is provided with a wireless data communication interface and a chemical sensor, an optical sensor, an electrochemical sensor or a thermochemical sensor connected to the wireless data communication interface.

[0013] As a further technical solution of the present invention, in step S3, the gas-liquid separator with a detection function utilizes the difference in density between gas and liquid to make the liquid sink and the gas rise under the action of gravity at 1 MPa and 200° C., thereby achieving separation. When the tail gas is output, a detection model is used to improve the separation ability, wherein the working method of the detection model is: According to the output waveform of the gas-liquid separator, the mixed gas function is analyzed, and the detection model output is: (1) In formula (1), Indicates the time of inputting mixed gas. Indicates the preset mixed gas concentration value. Indicates the concentration of mixed gas inside the separation environment. , It represents the gas expression function model after separation at different pressures. Indicates the internal gas reserve. represents the gas variation coefficient after separation, It represents the variable function after the mixed gas is separated; Indicates the type of internal gas reserve. Indicates the type, Indicates the amount of remaining data; Indicates the influence value of mixed gas at a certain pressure. Indicates the influence value of the mixed gas at another pressure. Indicates the amount of gas in the compressed environment. Indicates the amount of mixed gas in the total gas input; The differential calculation formula for the separation environment in the detection model is: (2) In formula (2), represents the quality detection function in the detection model, Indicates the number of gas types required for detection, Represents the mass function of the mixed gas influence quantity; The differential function and the separated environment mixed gas detection model function are processed together, and the detection separation mixed gas model function is simplified as follows: (3) In formula (3), Indicates the standard differential mass value of the gas.

[0014] According to the mixed gas separation failure that occurs during the separation environment operation, the gas operation time is estimated through the detection model, and the actual efficiency is estimated according to the filling gas volume. The estimated value output is: (4) In formula (4), represents the quality estimation function in the detection model, It indicates the budget after gas separation in the separation environment operation. Indicates the preset mixed gas concentration value. Indicates the concentration of mixed gas inside the separation environment detection separation environment. Indicates the standard differential mass value of the gas.

[0015] According to the estimated value of the separation environment operating efficiency after the mixed gas separation in formula (4), the probability formula is used to determine the probability of gas separation in the presence of differential mass: (5) In formula (5), It represents the probability of separation of the mixed gas in the separation environment. represents the gas differential mass set, represents a non-fully controllable variable, Indicates the amount of separated ambient gas; Through probability and estimation, we understand the situation after gas separation in the separation environment. The separation and filling rules of mixed gas in actual operation are as follows: (6) In formula (6), Indicates the value of the mixed gas in the separation environment during actual operation. Indicates the mixed gas metering method during the operation of the separation environment. Indicates the total gas filling volume, It means that the mixed gas affects the efficiency of the separation environment operation.

[0016] As a further technical solution of the present invention, when generating the third dilute nitric acid, the first dilute nitric acid and the second dilute nitric acid are fed into the 17th to 32nd layers of the absorption tower.

[0017] The present invention has the following positive and beneficial effects compared with the prior art: The process of preparing high-concentration nitric acid by the double-pressurized dilute nitric acid method of the present invention is to input a mixed gas according to a proportional algorithm model in the gasifier, and a cooling temperature difference detection module is set in the gasifier. When the maximum temperature difference is detected, the first dilute nitric acid and the cooled nitrogen oxide mixed gas are output; by setting a filtering module with decomposition ability of the nitrogen oxide separator, the output of high-concentration nitric acid is greatly improved. The second dilute nitric acid and the nitrogen oxide mixed gas are separated by a gas-liquid separator with a detection function, and data calculation is performed by a proportional algorithm model, wherein the proportional algorithm model includes a PLC controller and a proportional parameter setting module connected to the PLC controller, a ratio calculation module and a gas output module, which can calculate different parameters of the input mixture in real time, and optimize the control effect by adjusting the proportional coefficient, integral time and differential time, so that the model response is more stable and accurate; so that the required ratio of ammonia, oxygen and nitrogen can be optimized, which greatly improves the ability of preparing high-concentration nitric acid by the double-pressurized dilute nitric acid method. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work, among which: Figure 1 It is a schematic diagram of the process flow of the present invention; Figure 2 It is a schematic diagram of the principle of the proportional algorithm model in the present invention; Figure 3 It is a schematic diagram of the principle of the cooling temperature difference detection module in the present invention; Figure 4 The figure is a schematic diagram showing the working process of a gas-liquid separator with a detection function according to an embodiment of the present invention. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of this article to clearly and completely describe the technical solutions in the embodiments of this article. Obviously, the described embodiments are only part of the embodiments of this article, not all of the embodiments. It should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0020] Example 1 like Figure 1 As shown, a process for preparing high-concentration nitric acid by a double-pressurized dilute nitric acid method comprises the following preparation steps: S1. A mixed gas is input into the gasifier according to a proportional algorithm model, wherein the mixed gas contains at least ammonia, oxygen and nitrogen. After applying a pressure of 0.5 MPa, the generated nitrogen oxide mixed gas is extremely rapidly cooled under a pressure of 0.1 MPa to condense the compressed nitrogen oxide mixed gas at a dew point temperature. A cooling temperature difference detection module is provided in the gasifier, and when a maximum temperature difference is detected, a first dilute nitric acid and a cooled nitrogen oxide mixed gas are output; the concentration of the first dilute nitric acid is between 28% and 34%, and the temperature is between 38°C. S2, inputting the first dilute nitric acid into a nitrogen oxide separator, wherein the nitrogen oxide separator is provided with a filtering module with decomposition capability, wherein the first dilute nitric acid contacts with the cooled nitrogen oxide mixed gas in an absorption tower, and after a chemical reaction, the nitrogen oxide is converted into a compound soluble in acid, and then enters a tail gas preheater; S3, the tail gas is detected by a detector, and after heat exchange in a tail gas preheater, the nitrogen oxide mixed gas enters a high-pressure reaction water condenser to generate a second dilute nitric acid, and the second dilute nitric acid and the nitrogen oxide mixed gas are separated by a gas-liquid separator with a detection function, and the separated second dilute nitric acid passes through a nitrogen oxide separator with a decomposition function, and then is pumped into an absorption tower through a dilute acid pump. The absorption tower has a total of 64 plates, and the separated nitrogen oxide mixed gas enters the absorption tower from the bottom, and countercurrently contacts with the process water added to the top of the absorption tower to generate a third dilute nitric acid. The third dilute nitric acid is bleached by hot air from a bleaching tower to remove the nitrogen oxide gas dissolved in the acid, and then cooled by an acid cooler and sent to a finished acid storage tank; S4. The tail gas after the absorption reaction goes out from the top of the absorption tower and goes to the tail gas separator.

[0021] Example 2 like Figure 2 As shown, in step S1, the proportional algorithm model includes a PLC controller and a proportional parameter setting module, a ratio calculation module and a gas output module connected to the PLC controller, wherein: The PLC controller is responsible for executing the control program, monitoring the process variables, and controlling the actuators according to the preset algorithms and logic; The proportional parameter setting module is responsible for setting and adjusting the parameters of the proportional algorithm, optimizing the control effect by adjusting the proportional coefficient, integral time and differential time, so that the model response is more stable and accurate; The ratio calculation module calculates the required ratio of ammonia, oxygen and nitrogen according to the preset ratio requirements and real-time monitoring data; The gas output module controls the output amount of the gas according to the instruction of the PLC controller.

[0022] In a further specific embodiment, a programmable logic controller receives input signals from the ammonia, oxygen and nitrogen supply, processes these signals, and outputs control signals to actuators, such as valves, pumps, motors, etc., to improve the ratio control of ammonia, oxygen and nitrogen. The required ratio is calculated through the preset ratio requirements and real-time monitoring data, for example: ‌The reaction equation of ammonia, oxygen and nitrogen under double pressure is 4NH3 + 5O2 = 4NO + 6H2O. ‌ This reaction is carried out under specific conditions, including high temperature and high pressure, and usually requires the presence of a catalyst. Under dual pressurization conditions, ammonia and oxygen react to produce nitric oxide and water. How to improve the reaction efficiency? It is necessary to set it through the proportional parameter setting module. For example, when the ratio of NH3 to O2 is 1:1 and 4:5, the output is different. The various parameters of the proportional parameter setting module can be linked to the ratio of NH3 to O2. In specific applications, the proportional parameter setting module is usually implemented by software algorithms, which can run on PLC (programmable logic controller), DCS (distributed control system) or a special controller, and the parameters can be automatically adjusted according to the system dynamics through adaptive algorithms. By accurately setting the proportional parameters, the deviation of the controlled object can be reduced and the control accuracy can be improved. Reasonable setting of the proportional parameters helps to ensure the stable operation of the system and avoid oscillation and overshoot. After 10 hours of testing, the test data of the present invention are shown in Table 1: Table 1 Test data table of the ratio calculation module

[0023] Through experiments, it can be seen that the ammonia products produced by using the ratio calculation module of the present invention and those produced by not using the ratio calculation module of the present invention are compared and found that the method of the present invention has outstanding technical effects and outstanding yield.

[0024] Example 3 like Figure 3 As shown, in the step S1, the cooling temperature difference detection module includes a temperature control module and a temperature sensing module, a temperature calculation module, a temperature early warning module and a temperature adaptive adjustment module connected to the temperature control module.

[0025] In a further specific embodiment, the cooling temperature difference detection module is a comprehensive system consisting of multiple functional modules to ensure accurate and efficient temperature control during the cooling process.

[0026] The temperature control module is the core of the entire system, responsible for coordinating and managing the entire cooling process, including a central processing unit (CPU) or microcontroller for receiving and processing data from other modules. The temperature control module is responsible for setting the target temperature and adjusting the operation of the cooling system according to the deviation between the actual temperature and the target temperature.

[0027] The temperature sensing module is responsible for detecting the actual temperature in the environment or system. It consists of temperature sensors such as thermocouples, thermal resistors (RTDs), or infrared temperature sensors. The temperature sensing module converts the temperature signal into an electrical signal for subsequent processing.

[0028] The temperature calculation module receives the temperature signal from the temperature sensing module and calculates the actual temperature. It includes algorithms to process temperature data, such as average temperature, maximum / minimum temperature, temperature difference calculation, etc. The results of the temperature calculation module are used to feed back to the temperature control module for further adjustment.

[0029] The temperature warning module is used to monitor whether the temperature exceeds the preset safety range. When a temperature anomaly is detected, the warning module triggers an alarm to notify the operator or automatically take corrective measures. The warning module can set different temperature thresholds to deal with different safety risks.

[0030] The adaptive adjustment module automatically adjusts the parameters of the cooling system, such as the flow, pressure or temperature of the cooling water, according to the instructions of the temperature control module. It includes actuators such as valves, pumps or heating / cooling elements to directly control the operation of the cooling system. The temperature adaptive adjustment module adjusts the cooling system based on a preset curve or algorithm to achieve the best temperature control effect.

[0031] In a further specific embodiment, temperature sensing is first performed, and the temperature sensor detects the temperature of the cooling medium and transmits the signal to the temperature sensing module. Then, temperature calculation is performed, and the temperature calculation module receives the temperature signal and calculates the actual temperature and the temperature difference. Then, temperature control is performed, and the temperature control module issues a control instruction according to the deviation between the target temperature and the actual temperature. The temperature is adjusted, and the temperature adaptive adjustment module adjusts the parameters of the cooling system according to the control instruction. Finally, a temperature warning is performed, and if the temperature exceeds the safety range, the temperature warning module triggers an alarm.

[0032] Through such modular design, the cooling temperature difference detection module can achieve precise temperature control and improve the stability and safety of the system.

[0033] If necessary, a medium carrier can be set during the application process to ensure that the gas flows evenly through the surface of the platinum mesh, resulting in a large temperature difference, thereby improving the conversion of ammonia oxides and nitrogen oxides. After 5 hours of testing, the test data shown in Table 2 were obtained: Table 2 Test data table

[0034] Through experiments, it was found that the cooling temperature difference detection module of the present invention can improve the temperature detection capability, with a detection accuracy of more than 99%, and has a particularly outstanding technical effect, and can improve the calculation capability of high-concentration nitric acid.

[0035] Example 4 In the step S1, the generated nitrogen oxide mixed gas is rapidly oxidized under a pressure of 0.5 MPa to form unstable nitrate ions, which are continuously output for 2.5 hours, and the nitrogen content in the nitric acid increases. The nitric acid is then pressurized to 2 MPa to further promote the generation of nitrate ions, and the gas is rapidly cooled within 3 seconds, and the cooled mixed gas is output. After 3 hours of experiments, the data information of the present invention is shown in Table 3: Table 3 Test data record table

[0036] During the test process of the present invention, the nitrogen oxide mixed gas generated by ammonia oxidation is gradually output, and after being cooled by the method introduced in the previous step, the nitrogen oxide mixed gas enters through the nitrogen oxide separator, and the data information after entering is compressed, for example, to 2 MPa, 200°C. In this way, after heat exchange through the tail gas preheater, it passes through the high-pressure reaction water condenser, and the condensed second nitric acid is output under high pressure reaction. The gas-liquid separator separates the dilute nitric acid and the nitrogen oxide mixed gas, and the separated second nitric acid is separated through the nitrogen oxide separator, and then sent to the absorption tower through the dilute acid pump, and the nitrogen oxide mixed gas cooled to 40°C by the high-pressure reaction water condenser enters the absorption tower from the bottom.

[0037] Through experiments, the present invention effectively reduces the emission of toxic tail gas. Nitrogen oxides in the production process of nitric acid are the main substances that cause air pollution (NO x ), and its absorption and reaction depth are closely related to pressure. The greater the pressure, the stronger the absorption. It is beneficial to improve the purity of nitric acid (greater than 65%).

[0038] The process of double-pressure dilute nitric acid method mainly includes oxidation of ammonia and NO x There are two main steps in the absorption of NO. In the ammonia oxidation process, liquid ammonia is evaporated and heated, mixed with air, and oxidized in the ammonia oxidation furnace to generate NO x This process is carried out at medium pressure, and the NO x After being cooled and compressed, the gas enters the nitric acid absorption tower and reacts with water under high pressure to produce nitric acid. In this process, high-concentration nitric acid production can be achieved by controlling the reaction conditions and optimizing the process flow.

[0039] Example 5 In the step S2, the filter module with decomposition capability treats the tail gas through vanadium pentoxide‌.

[0040] In a specific embodiment, vanadium pentoxide (V2O5) has decomposition ability and is used in the filtration module in the process of preparing nitric acid. Vanadium pentoxide (V2O5) is a highly oxidizing compound that can catalytically decompose nitrogen oxides under high temperature conditions and convert them into harmless nitrogen and oxygen. This property makes vanadium pentoxide play an important role in the process of preparing nitric acid, especially in the filtration module, through its catalytic decomposition ability, the production efficiency and purity of nitric acid are improved. In addition, this characteristic of vanadium pentoxide also makes it have important application value in environmental protection and air pollution control, and reduces pollution to the environment by promoting the decomposition of nitrogen oxides.

[0041] Example 6 In the step S2, the nitrogen oxide separator includes at least activated carbon, molecular sieve, and metal organic framework membrane.

[0042] In further embodiments, a nitrogen oxide separator is a chemical reaction specifically designed to separate nitrogen oxide (NO) and its oxidation products (such as NO2) from a gas mixture. These separators are often used for industrial emission control, environmental monitoring or laboratory analysis. The following are some common technical essences: 1. Selective adsorption: Materials with high adsorption capacity (adsorbents) are used to adsorb nitrogen oxides. Common adsorbents include activated carbon, molecular sieves, metal organic frameworks (MOFs), and specific types of zeolites. The selective adsorption capacity of the adsorbent allows nitrogen oxides to be preferentially adsorbed in the mixed gas, while other gases pass through the separator.

[0043] 2. Chemical absorption: Chemical solutions (absorbents) are used to react with nitrogen oxides to convert them into compounds soluble in liquids. Commonly used absorbents include water, alkaline solutions (such as sodium hydroxide NaOH, potassium hydroxide KOH), ammonia water (NH3·H2O), etc.

[0044] Example reaction equation: [ 2NO + H2O → HNO2 + NO2 ] [2NO2+ 2NaOH → NaNO3 + NaNO2 + H2O].

[0045] 3. Membrane separation: Selective permeable membranes are used to separate nitrogen oxides. Such membranes have a high permeability to nitrogen oxides and are almost impermeable to other gases. The membrane material can be polymer, metal or ceramic, and its selectivity depends on the molecular size and interaction of nitrogen oxides with other gases.

[0046] 4. Low temperature condensation: Separation is achieved by lowering the temperature of the gas mixture, causing the nitrogen oxides to condense into a liquid or solid. This method is suitable for situations where the concentration of nitrogen oxides is high, because nitrogen oxides condense at a relatively low temperature.

[0047] 5. Plasma technology: Plasma technology uses active particles (such as electrons, ions and free radicals) generated by plasma to decompose nitrogen oxides. Plasma technology can effectively convert nitrogen oxides into harmless nitrogen (N2) and oxygen (O2).

[0048] 6. Selective Catalytic Reduction (SCR): In the presence of a catalyst, a reducing agent (such as urea or ammonia) is used to reduce nitrogen oxides to nitrogen gas. This process is commonly used for industrial emission control, such as automobile exhaust treatment.

[0049] 7. Absorption tower: Using a multi-stage absorption tower, the absorption efficiency of nitrogen oxides is improved by continuously circulating the absorbent. The design of the absorption tower can optimize the utilization of the absorbent and the removal efficiency of nitrogen oxides.

[0050] The technical essence of the NOx separator depends on the specific application requirements, the composition of the gas mixture, the separation efficiency requirements and cost considerations. In practical applications, it may be necessary to combine multiple technologies to achieve the best separation effect.

[0051] Example 7 In step S2, the method for converting nitrogen oxides into compounds soluble in acid is: 3NO2+H2O=2HNO3+NO.

[0052] Example 8 In the step S2, the detector is provided with a wireless data communication interface and a chemical sensor, an optical sensor, an electrochemical sensor or a thermochemical sensor connected to the wireless data communication interface.

[0053] This description involves a tail gas treatment system, which includes a detector, tail gas preheater, high pressure reactive water condenser and second dilute acid generation. The following is the technical essence of each component: The detector is used to monitor the concentration of nitrogen oxides (NO and NO2) in exhaust gas. Chemical sensors detect NO by using chemical substances (such as selective absorbents or catalysts).x Optical sensors use optical principles such as UV-visible spectroscopy, infrared spectroscopy or laser induced fluorescence (LIF) to detect NO x Electrochemical sensors measure NO through electrochemical reactions. x Thermochemical sensors use NO x Its concentration is detected by the change in heat produced by its reaction with a hot surface.

[0054] The tail gas preheater is used to preheat the tail gas to improve the efficiency of the subsequent treatment steps. The tail gas preheater includes a heat exchanger in the specific application, which transfers the heat in the tail gas to a cooling medium (such as water or air) through the heat exchanger to preheat the tail gas. The burner uses a burner to directly heat the tail gas to increase its temperature. The high-pressure reaction water condenser is used to convert NO in the nitrogen oxide mixture into x It is converted into a compound soluble in acid and produces a second dilute acid. In the chemical reaction under high pressure and cooling conditions, NO x It reacts chemically with water or acidic solution to generate nitric acid (HNO3) or nitrous acid (HNO2). NOx is condensed by lowering the temperature and dissolved in the condensed water to form dilute acid. x After reacting with water or acidic solution, the second dilute acid is generated. In this work, NO x Reacts with alkaline solutions (such as sodium hydroxide NaOH) to form nitrates or nitrites, which dissolve in water to form dilute acids. x Under acidic conditions, it is oxidized or reduced to generate the corresponding acid. In general, the technical essence of this system involves the monitoring, preheating, chemical reaction and condensation process of exhaust gas to achieve NO x The conversion of water and the production of dilute acid. Each component uses a specific physical or chemical principle to achieve its function. Wireless connection can realize data information interaction in various occasions.

[0055] Example 9 like Figure 4 As shown, in the step S3, the gas-liquid separator with detection function utilizes the difference in density between gas and liquid to make the liquid sink and the gas rise under 1Mpa and 200°C by gravity, thereby achieving separation. When the tail gas is output, the detection model is used to improve the separation ability, wherein the working method of the detection model is: In this step, temperature changes will affect the physical properties of the gas and liquid, such as density and viscosity, thereby affecting the separation efficiency. Pressure changes will affect the density of the gas and the boiling point of the liquid, affecting the separation process.

[0056] The detection model makes full use of modern waveform control systems and photoacoustic sensing technology, and realizes ion analysis and waveform conversion of mixed gases through multiple technical functions. Finally, it is incorporated into the algorithm program in the form of ions to achieve detection after separation in the separation environment, laying the foundation for the stability of gas separation.

[0057] According to the output waveform of the gas-liquid separator, the mixed gas function is analyzed, and the detection model output is: (1) In formula (1), Indicates the time of inputting mixed gas. Indicates the preset mixed gas concentration value. Indicates the concentration of mixed gas inside the separation environment. 、 It represents the gas expression function model after separation at different pressures. Indicates the internal gas reserve. represents the gas variation coefficient after separation, It represents the variable function after the mixed gas is separated; Indicates the type of internal gas reserve. Indicates the type, Indicates the amount of remaining data; Indicates the influence value of mixed gas at a certain pressure. Indicates the influence value of the mixed gas at another pressure. Indicates the amount of gas in the compressed environment. Indicates the amount of mixed gas in the total gas input; In a specific embodiment, in a detection model of a gas-liquid separator output waveform analysis mixed gas function, the output generally refers to the mixed gas composition, concentration or other related parameters calculated by the model based on the input waveform data. Detection model output: { "Timestamp": "2023-04-01T12:00:00Z", "Mixed gas composition": { "ingredient 1": { "Concentration": 0.15, / / The concentration of component 1, the unit can be ppm (parts per million by volume) "Confidence": 0.95 / / Confidence of the estimated concentration of component 1 }, "ingredient 2": { "Concentration": 0.05, "Confidence": 0.90 }, / / ... other components }, "Total amount of mixed gas": 0.20, / / Total volume or mass of mixed gas "Separation efficiency": 0.85, / / The separation efficiency of the separator for mixed gases, ranging from 0 to 1 "Waveform Features": { "Peak": 0.30, / / Peak intensity in the waveform "Periodicity": 0.70, / / The periodicity of the waveform / / ... other waveform features }, "Anomaly Detection": { "Exception": "None", / / Detects whether there are any abnormal conditions, such as leakage, blockage, etc. "description": "Normal working" / / Description of abnormal situation } } In the listed embodiment, the timestamp records the time when the detection model runs, which is very important for tracking and analyzing data. Mixed gas composition is an object that contains the concentration and confidence of each component in the mixed gas. Concentration is the proportion of each component in the mixed gas, and confidence indicates the reliability of the model's concentration estimate. The total amount of mixed gas represents the total amount of the entire mixed gas, which can be volume or mass. Separation efficiency indicates the separation effect of the gas-liquid separator on the mixed gas, which is a value between 0 and 1. Waveform features contain features extracted from waveform data, such as peak intensity and periodicity, which help the model better understand the waveform data. Anomaly detection indicates whether the model detects any abnormal conditions, such as chemical reaction failures or operational errors.

[0058] The differential calculation formula for the separation environment in the detection model is: (2) In formula (2), represents the quality detection function in the detection model, Indicates the number of gas types required for detection, Represents the mass function of the mixed gas influence quantity; In a further specific embodiment, Indicates at time When the quality detection function in the detection model is This difference may be caused by changes in the composition of the mixed gas, changes in separation efficiency, or other factors. Represents the mass detection function, which is a function used by the model to estimate or calculate the mass or concentration of a component in a mixed gas. Indicates the number of gas types required for detection, indicating the number of gas components that the model needs to detect. The mixed gas influence quantity mass function, which indicates the time At that time, The amount by which a gas component affects the total mass of the mixed gas. This function may be calculated based on factors such as the concentration, molar mass, and volume fraction of the gas component. This differential calculation formula is used in the detection model to evaluate the mass change in the separation environment, which helps monitor the performance of the separator and the changes in gas composition.

[0059] The differential function and the separated environment mixed gas detection model function are processed together, and the detection separation mixed gas model function is simplified as follows: (3) In formula (3), Indicates the standard differential mass value of the gas.

[0060] In a specific embodiment, the difference function is used to calculate the rate of change of the mixed gas composition over time. This can be achieved by first-order differences or higher-order differences. In a specific embodiment, some additional parameters or functions are used to describe the separation efficiency, gas flow characteristics, etc. For example, the separation efficiency : Indicates the degree to which the separator separates the different components in the mixed gas. For example, the gas flow rate : Indicates the flow rate of the gas in the separator. The residence time of the mixed gas in the separator : represents the average time that the gas stays in the separator. The differential function is combined with the separation environment characteristics to form a model function set. The differential function is combined with the separation environment characteristics to form a model function set. The differential function is combined with the separation environment characteristics to form a model function set.

[0061] The mixed gas composition change rate function describes the change of gas composition over time. The separation efficiency function describes the separation effect of the separator on gas components. The gas flow function describes the flow of gas in the separator. If the separation efficiency and gas flow characteristics do not change much, the linearization method can be used to simplify the model.

[0062] According to the mixed gas separation failure that occurs during the separation environment operation, the gas operation time is estimated through the detection model, and the actual efficiency is estimated according to the filling gas volume. The estimated value output is: (4) In formula (4), represents the quality estimation function in the detection model, It indicates the budget after gas separation in the separation environment operation. Indicates the preset mixed gas concentration value. Indicates the concentration of mixed gas inside the separation environment detection separation environment. Indicates the standard differential mass value of the gas.

[0063] Where Y represents the output value of the mass estimation function in the detection model, which usually represents the estimated gas running time or the estimated value of the separation efficiency. The internal mixed gas concentration detected in the separation environment is measured by the detection model, which reflects the actual concentration of the gas components inside the separator. The preset mixed gas concentration value, this value is the concentration that the mixed gas should have under ideal or preset conditions. The gas standard differential mass value, which is a constant, represents the uncertainty or standard error of the gas concentration measurement. The gas running time, that is, the total time the gas runs in the separation environment. The standard deviation of the gas concentration, which describes the volatility of the gas concentration measurement or the natural variation of the gas concentration.

[0064] According to the estimated value of the separation environment operating efficiency after the mixed gas separation in formula (4), the probability formula is used to determine the probability of gas separation in the presence of differential mass: (5) In formula (5), It represents the probability of separation of the mixed gas in the separation environment. represents the gas differential mass set, represents a non-fully controllable variable, Indicates the amount of separated ambient gas; Through probability and estimation, we understand the situation after gas separation in the separation environment. The separation and filling rules of mixed gas in actual operation are as follows: (6) In formula (6), Indicates the value of the mixed gas in the separation environment during actual operation. Indicates the mixed gas metering method during the operation of the separation environment. Indicates the total gas filling volume, It means that the mixed gas affects the efficiency of the separation environment operation.

[0065] Through the detection model, the probability of estimating the concentration of mixed gases in the separation environment after separation and the impact of gas separation in actual operation can be estimated, so that the detection system can more accurately understand the actual operating conditions of the separation environment, provide reference value for comparing the outdoor and indoor concentrations of mixed gases, and improve the feasibility of the detection system in this study for mixed gas operation.

[0066] After 5 hours of testing, it was found that the separation effect of the present invention is shown in Table 4.

[0067] The above experiments show that the detection model of the present invention has outstanding technical effects.

[0068] Example 10 When the third dilute nitric acid is generated, the first dilute nitric acid and the second dilute nitric acid are fed into the 17th to 32nd trays in the absorption tower.

[0069] In the prior art, the second nitric acid from the high-pressure reaction water condenser is sent to the absorption tower, but is instead sent to the nitrogen oxide separator after being separated by the gas-liquid separator, and then pumped into the absorption tower on the plate with a similar acid concentration through the dilute acid pump, thereby reducing the dilution heat to lower the absorption reaction temperature, thereby increasing the dilute acid concentration. In a specific embodiment, the dilute acid produced by the high-pressure reaction water condenser is changed from being directly sent to the absorption tower to first being separated by the gas-liquid separator and then sent to the nitrogen oxide separator. Afterwards, the treated dilute acid is pumped to the absorption tower by the dilute acid pump to connect with the plate with a similar acid concentration, thereby reducing the dilution heat, lowering the absorption reaction temperature, and then increasing the dilute acid concentration.

[0070] In order to reduce the corrosion of chloride ions on the stainless steel absorption tower, the chlorine removal operation was adjusted from the 4th to 5th layers of the absorption tower to the 17th to 32nd layers of the tower. At the same time, the number of cooling coils at the bottom of the absorption tower was increased from the original 18 layers to 32 layers, thereby expanding the heat exchange area, more effectively removing the reaction heat, and reducing the reaction temperature. These improvements are aimed at accelerating the process of converting nitric oxide into nitrogen dioxide and promoting the reaction of nitrogen dioxide in the direction of absorbing dilute acid, ultimately increasing the production concentration of dilute acid.

[0071] 14 groups of cold water coils are arranged on the 12th to 19th floors of the absorption tower, and these coils are connected by cold water pipes, in which the water temperature is maintained at 17°C. 8 groups of chilled water coils are equipped on the 18th to 32nd floors of the absorption tower, and the water source of these coils comes from the water production station, and the water temperature is 5°C. In addition, the upper part (1-10th floors) and the lower part (11-24th floors) of the 18-layer cooling coils are respectively connected to cooling water pipes, and the temperature of the cooling water pipes is 40°C.

[0072] The process water introduced from the top of the absorption tower is in countercurrent contact with the gas in the tower. The process water is transported to the absorption tower by the process water cooler, and its temperature entering the tower is 16°C. About 60% (mass percentage) of dilute acid three is prepared, and its temperature is about 50°C. The concentration of dilute acid three fluctuates between 59.0% and 61.0% (mass percentage). In order to promote the absorption reaction to develop in the direction of generating dilute acid and increase the concentration of dilute acid, the temperature of the process water is reduced from the original 30°C to 15°C.

[0073] About 65% (mass percentage) of the third nitric acid is prepared at a temperature of about 40°C. The concentration of the third nitric acid fluctuates between 60.0% and 62.0% (mass percentage). In order to promote the absorption reaction to produce dilute acid and increase the concentration of dilute acid, the temperature of the process water is reduced from the original 40°C to 10°C. Then the concentration of the purified nitric acid is obtained.

[0074] The purification method is: 1. Bleaching tower treatment: The diluted acid is treated with hot air at 120°C in the bleaching tower. The purpose is to remove the nitrogen oxide gas dissolved in the acid. After treatment, the temperature of the acid rises to 65°C.

[0075] 2. Changes in acid concentration: After treatment in the bleaching tower, the acid concentration reaches 70% (mass fraction).

[0076] 3. Acid cooling: The acid is then cooled in an acid cooler, and the temperature of the cooled acid drops to 40°C.

[0077] 4. Storage: The acid cooled to 40°C is sent to the finished acid storage tank for storage.

[0078] 5. Exhaust gas treatment: The tail gas after the absorption reaction is discharged from the top of the absorption tower. The temperature of the tail gas is 20℃ and the pressure is 0.895MPa.

[0079] 6. Exhaust gas separation: The tail gas is sent to the tail gas separator for treatment. The purpose of the tail gas separator is to separate and recover any valuable components that may be present, or to further process them to reduce emissions.

[0080] In this process, changes in temperature and pressure are key factors for both acid treatment and tail gas treatment. Lowering the temperature helps cool the acid, while changes in pressure may affect the solubility and separation efficiency of the gas in the tail gas. The nitrogen oxide mixed gas produced by ammonia oxidation is first rapidly cooled by a low-pressure reaction water cooler and then enters a nitrogen oxide separator. The separated gas is pumped to the absorption tower by dilute nitric acid. The cooled nitrogen oxide gas then enters the compressor, heats the tail gas preheater, and then enters the high-pressure reaction water condenser. Through this series of treatments, the final concentration of dilute nitric acid produced reaches 68% (mass fraction), realizing the production of high-concentration dilute nitric acid. The advantages of the double-pressurized dilute nitric acid method include high efficiency, high yield, and environmental protection. By optimizing process conditions and chemical reactions, not only can the production efficiency of nitric acid be improved, but also energy consumption and environmental pollution can be reduced. In addition, the process also has good economic benefits and can bring good returns to enterprises. In summary, the double-pressurized dilute nitric acid method achieves the production of high-concentration nitric acid by optimizing the oxidation of ammonia and the absorption process of NOx. It is an efficient, environmentally friendly and economical method for preparing nitric acid.

[0081] Although the specific embodiments of the present invention are described above, it should be understood by those skilled in the art that these specific embodiments are only illustrative, and those skilled in the art may make various omissions, substitutions and changes to the details of the above methods and systems without departing from the principles and essence of the present invention. For example, merging the above method steps so as to perform substantially the same functions in substantially the same manner to achieve substantially the same results is within the scope of the present invention. Therefore, the scope of the present invention is limited only by the appended claims.

Claims

1. A process for preparing high-concentration nitric acid by a double-pressurized dilute nitric acid method, characterized in that: The method comprises the following preparation steps: S1. A mixed gas is input into the gasifier according to a proportional algorithm model, wherein the mixed gas contains at least ammonia, oxygen and nitrogen. After applying a pressure of 0.5 MPa, the generated nitrogen oxide mixed gas is extremely rapidly cooled under a pressure of 0.1 MPa to condense the compressed nitrogen oxide mixed gas at a dew point temperature. A cooling temperature difference detection module is provided in the gasifier, and when a maximum temperature difference is detected, a first dilute nitric acid and a cooled nitrogen oxide mixed gas are output; the concentration of the first dilute nitric acid is between 28% and 34%, and the temperature is between 38°C. S2, inputting the first dilute nitric acid into a nitrogen oxide separator, wherein the nitrogen oxide separator is provided with a filtering module with decomposition capability, wherein the first dilute nitric acid contacts with the cooled nitrogen oxide mixed gas in an absorption tower, and after a chemical reaction, the nitrogen oxide is converted into a compound soluble in acid, and then enters a tail gas preheater; S3, the tail gas is detected by a detector, and after heat exchange in a tail gas preheater, the nitrogen oxide mixed gas enters a high-pressure reaction water condenser to generate a second dilute nitric acid, and the second dilute nitric acid and the nitrogen oxide mixed gas are separated by a gas-liquid separator with a detection function, and the separated second dilute nitric acid passes through a nitrogen oxide separator with a decomposition function, and then is pumped into an absorption tower through a dilute acid pump. The absorption tower has a total of 64 plates, and the separated nitrogen oxide mixed gas enters the absorption tower from the bottom, and countercurrently contacts with the process water added to the top of the absorption tower to generate a third dilute nitric acid. The third dilute nitric acid is bleached by hot air from a bleaching tower to remove the nitrogen oxide gas dissolved in the acid, and then cooled by an acid cooler and sent to a finished acid storage tank; S4. The tail gas after the absorption reaction goes out from the top of the absorption tower and goes to the tail gas separator.

2. The process for preparing high-concentration nitric acid by a double-pressurized dilute nitric acid method according to claim 1, characterized in that: In step S1, the proportional algorithm model includes a PLC controller and a proportional parameter setting module, a ratio calculation module and a gas output module connected to the PLC controller, wherein: The PLC controller is responsible for executing the control program, monitoring the process variables, and controlling the actuators according to the preset algorithms and logic; The proportional parameter setting module is responsible for setting and adjusting the parameters of the proportional algorithm, optimizing the control effect by adjusting the proportional coefficient, integral time and differential time, so that the model response is more stable and accurate; The ratio calculation module calculates the required ratio of ammonia, oxygen and nitrogen according to the preset ratio requirements and real-time monitoring data; The gas output module controls the output amount of the gas according to the instruction of the PLC controller.

3. The process for preparing high-concentration nitric acid by a double-pressurized dilute nitric acid method according to claim 1, characterized in that: In the step S1, the cooling temperature difference detection module includes a temperature control module and a temperature sensing module, a temperature calculation module, a temperature early warning module and a temperature adaptive adjustment module connected to the temperature control module.

4. The process for preparing high-concentration nitric acid by a double-pressurized dilute nitric acid method according to claim 1, characterized in that: In step S1, the generated nitrogen oxide mixed gas is rapidly oxidized under a pressure of 0.5 MPa to form unstable nitrate ions. The gas is continuously output for 2.5 hours to increase the nitrogen content in the nitric acid. The gas is then pressurized to 2 MPa to further promote the formation of nitrate ions. The gas is rapidly cooled within 3 seconds and the cooled mixed gas is output.

5. The process for preparing high-concentration nitric acid by a double-pressurized dilute nitric acid method according to claim 1, characterized in that: In the step S2, the filter module with decomposition capability treats the tail gas through vanadium pentoxide‌.

6. The process for preparing high-concentration nitric acid by a double-pressurized dilute nitric acid method according to claim 1, characterized in that: In the step S2, the nitrogen oxide separator includes at least activated carbon, molecular sieve, and metal organic framework membrane.

7. The process for preparing high-concentration nitric acid by a double-pressurized dilute nitric acid method according to claim 1, characterized in that: In the step S2, the detector is provided with a wireless data communication interface and a chemical sensor, an optical sensor, an electrochemical sensor or a thermochemical sensor connected to the wireless data communication interface.

8. The process for preparing high-concentration nitric acid by a double-pressurized dilute nitric acid method according to claim 1, characterized in that: In step S3, the gas-liquid separator with detection function utilizes the difference in density between gas and liquid to make the liquid sink and the gas rise under the action of gravity at 1 MPa and 200° C., thereby achieving separation. When the tail gas is output, the detection model is used to improve the separation ability, wherein the working method of the detection model is: According to the output waveform of the gas-liquid separator, the mixed gas function is analyzed, and the detection model output is: (1) In formula (1), Indicates the time of inputting mixed gas. Indicates the preset mixed gas concentration value. Indicates the concentration of mixed gas inside the separation environment, 、 It represents the gas expression function model after separation at different pressures. Indicates the internal gas reserve. represents the gas variation coefficient after separation, It represents the variable function after the mixed gas is separated; Indicates the type of internal gas reserve. Indicates the type, Indicates the amount of remaining data; Indicates the influence value of mixed gas at a certain pressure. Indicates the influence value of the mixed gas at another pressure. Indicates the amount of gas in the compressed environment. Indicates the mixed gas volume of the total gas input; The differential calculation formula for the separation environment in the detection model is: (2) In formula (2), represents the quality detection function in the detection model, Indicates the number of gas types required for detection, Represents the mass function of the mixed gas influence quantity; The differential function and the separated environment mixed gas detection model function are processed together, and the detection separation mixed gas model function is simplified as follows: (3) In formula (3), Indicates the standard differential mass value of gas; According to the mixed gas separation failure that occurs during the separation environment operation, the gas operation time is estimated through the detection model, and the actual efficiency is estimated according to the filling gas volume. The estimated value output is: (4) In formula (4), represents the quality estimation function in the detection model, It indicates the budget after gas separation in the separation environment operation. Indicates the preset mixed gas concentration value. Indicates the concentration of mixed gas inside the separation environment detection separation environment. Indicates the standard differential mass value of gas; According to the estimated value of the separation environment operating efficiency after the mixed gas separation in formula (4), the probability formula is used to determine the probability of gas separation in the presence of differential mass: (5) In formula (5), It represents the probability of separation of the mixed gas in the separation environment. represents the gas differential mass set, represents a non-fully controllable variable, Indicates the amount of separated ambient gas; Through probability and estimation, we understand the situation after gas separation in the separation environment. The separation and filling rules of mixed gas in actual operation are as follows: (6) In formula (6), Indicates the value of the mixed gas in the separation environment during actual operation. Indicates the mixed gas metering method during the operation of the separation environment. Indicates the total gas filling volume, It means that the mixed gas affects the efficiency of the separation environment operation.

9. The process for preparing high-concentration nitric acid by a double-pressurized dilute nitric acid method according to claim 1, characterized in that: When the third dilute nitric acid is generated, the first dilute nitric acid and the second dilute nitric acid are fed into the 17th to 32nd trays in the absorption tower.

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