Process for preparing ammonia water by using ammonia recovery tower

Abstract

The invention relates to the technical field of ammonia water preparation, and particularly discloses a process for preparing ammonia water by using an ammonia recovery tower, which comprises the following steps: pre-purifying original ammonia gas entering the ammonia recovery tower to obtain high-purity original ammonia gas; introducing the high-purity original ammonia gas into an ammonia recovery tower to obtain a preliminary ammonia-rich aqueous solution; carrying out an organic-inorganic composite membrane separation process on the preliminary ammonia-rich aqueous solution to obtain concentrated ammonia water; adding a metal organic framework catalyst into the middle of the ammonia recovery tower to obtain intermediate concentrated ammonia water; regulating and controlling the temperature of the intermediate concentrated ammonia water to finally obtain an ammonia water finished product; according to the invention, through dynamic electric field regulation and control, ultrasonic-assisted absorption, PI D feedback control membrane separation, MOF catalytic reaction and intelligent temperature control photocatalytic post-treatment in the pretreatment stage, each link adopts an advanced control algorithm and a real-time data acquisition technology, and efficient synergistic effect is formed among the steps; and the conversion process from the ammonia gas to the ammonia water is rapid and stable.

Description

Technical Field

[0001] The present invention belongs to the technical field of ammonia water preparation, and particularly relates to a process for preparing ammonia water by using an ammonia recovery tower. Background Art

[0002] In the existing process for preparing ammonia water by using an ammonia recovery tower, relatively traditional treatment methods are usually adopted. The raw ammonia gas directly enters the ammonia recovery tower and reacts with water through a simple physical dissolution process to form ammonia water. However, there are several significant deficiencies in this traditional process. First of all, the raw ammonia gas often contains solid particles and various impurities. If these impurities are not effectively removed, they will directly affect the purity and quality of the ammonia water. In the existing technology, the pretreatment means for the raw ammonia gas are relatively simple, lacking efficient purification technology, resulting in a relatively high content of impurities in the ammonia water and making it difficult to meet the high-standard product quality requirements.

[0003] Secondly, in the process of ammonia gas dissolving in water, the traditional process lacks effective means to enhance mass transfer, resulting in a slow dissolution rate of ammonia gas and low production efficiency. In addition, for the initially formed ammonia-rich aqueous solution, the concentration process in the existing technology is often not precisely controlled, easily leading to incomplete removal of water or over-concentration, affecting the concentration stability of the final ammonia water.

[0004] Furthermore, in the existing process for catalyzing the reaction between ammonia gas and water molecules, traditional catalysts are usually used, which have limited catalytic efficiency and a relatively high reaction activation energy, resulting in a slow reaction rate, a long reaction time, and the need for a relatively large reactor volume. At the same time, for the residual impurities generated during the reaction process, the treatment means in the existing technology are relatively single, lacking an efficient and stable degradation process, and it is difficult to ensure the purity and stability of the ammonia water.

[0005] Finally, in the existing process for dealing with raw material fluctuations and operating conditions changes, there are no flexible and effective control means, resulting in a relatively high sensitivity of the system to external environmental changes and poor product quality stability. In addition, there are also relatively large problems in terms of energy consumption in the traditional process, with a relatively high overall energy consumption, which is not conducive to energy conservation, emission reduction, and sustainable development.

[0006] In view of this, the inventor proposes a process for preparing ammonia water by using an ammonia recovery tower to solve the above problems. Summary of the Invention

[0007] The purpose of the present invention is to provide a process for preparing ammonia water by using an ammonia recovery tower to solve the problems raised in the above background art.

[0008] To achieve the above purpose, the present invention provides the following technical solutions:

[0009] A process for preparing ammonia water by using an ammonia recovery tower, comprising:

[0010] The raw ammonia gas entering the ammonia recovery tower is pre-purified by using electrostatic filtration and nanomembrane technology to remove solid particles and impurities in the raw ammonia gas, and high-purity raw ammonia gas is obtained;

[0011] The high-purity raw ammonia gas is introduced into the ammonia recovery tower, and the ultrasonic enhanced mass transfer algorithm is adopted to apply ultrasonic vibration, so that the ammonia gas is quickly dissolved in water to obtain a preliminary ammonia-rich aqueous solution;

[0012] The preliminary ammonia-rich aqueous solution is subjected to an organic-inorganic composite membrane separation process, and a feedback control algorithm for membrane separation and concentration is used to separate the water molecule and ammonia gas mixture, and part of the water is removed through the concentration process to obtain concentrated ammonia water;

[0013] A metal-organic framework catalyst is added in the middle of the ammonia recovery tower, and a kinetic optimization model is constructed to catalyze the reaction between ammonia gas and water molecules in the concentrated ammonia water, accelerate the increase of the ammonia water concentration, and obtain intermediate concentrated ammonia water;

[0014] The temperature of the intermediate concentrated ammonia water is regulated, and combined with the photocatalyst degradation process, it is used to eliminate residual impurities and stabilize the ammonia water concentration, and finally the finished ammonia water is obtained.

[0015] Preferably, the calculation formula for the removal efficiency of using electrostatic filtration and nanomembrane technology to synergistically remove impurities is:

[0016]

[0017] Among them, Cin and Cout are the impurity concentrations before and after filtration respectively;

[0018] Adopting a dynamic regulation algorithm based on real-time feedback to always maintain a removal rate of ≥95% under different feed concentrations, and the expression of the dynamic regulation algorithm is:

[0019]

[0020] Among them, Ea is the adjusted electric field strength;

[0021] Eb is the basic electric field strength;

[0022] Kd is the electric field regulation coefficient;

[0023] Cr is the reference concentration.

[0024] Preferably, the ultrasonic enhanced mass transfer algorithm includes an ultrasonic enhancement factor method and a mass transfer coefficient enhancement method;

[0025] Among them, the formula of the ultrasonic enhancement factor method is:

[0026]

[0027] Among them, P US represents the ultrasonic power, unit: watt;

[0028] f is the ultrasonic frequency, unit: kHz;

[0029] V is the volume of the liquid in the reactor, unit: L;

[0030] The formula for the mass transfer coefficient enhancement method is:

[0031] kL = kL,0(1 + γ×UCF)

[0032] Among them, kL,0 is the basic mass transfer coefficient under the condition of no ultrasound;

[0033] γ is the empirical adjustment factor.

[0034] Preferably, the formula for the feedback control algorithm of the membrane separation and concentration is:

[0035]

[0036] During the membrane separation process, to maintain the ideal flux J and ammonia concentration C, the pressure difference across the membrane is adjusted by PID feedback control;

[0037] Among them, ΔPbase is the initial pressure difference;

[0038] Ct is the target ammonia concentration;

[0039] Kp, Ki, and Kd are the proportional, integral, and differential gain coefficients respectively, which are optimized according to the membrane characteristics and flow rate;

[0040] By measuring the solution concentration C in real time and dynamically adjusting the pressure difference, the membrane flux J can be made close to the predetermined target and the concentration polarization phenomenon can be reduced.

[0041] Preferably, in the kinetic optimization model, under the action of the metal-organic framework MOF catalyst, the reaction rate r of ammonia and water is expressed as:

[0042]

[0043] Among them, k0 is the pre-exponential factor, which is related to the specific surface area of the catalyst;

[0044] Ea is the activation energy;

[0045] R is the gas constant;

[0046] T is the reaction temperature;

[0047] α and β are the reaction orders of ammonia and water respectively.

[0048] Preferably, the first-order reaction rate of the degradation of residual impurities under the action of photocatalyst in the photocatalyst degradation process is:

[0049]

[0050] where C is the impurity concentration and kphoto is the photocatalytic degradation rate constant;

[0051] Through the light intensity adaptive regulation model, the degradation rate is optimized in real time, and the calculation formula is:

[0052]

[0053] where k0photo is the basic degradation rate constant;

[0054] I is the current light intensity;

[0055] Ir is the reference light intensity;

[0056] δ is the adjustment coefficient.

[0057] Preferably, the frequency of the ultrasonic vibration is 20 kHz to 40 kHz.

[0058] Preferably, the organic-inorganic composite membrane is a bilayer structure, the first layer is an organic polymer membrane, and the second layer is an inorganic ceramic membrane.

[0059] Preferably, the metal-organic framework catalyst is selected from catalysts based on zinc or copper, and its specific surface area is greater than 1000 m 2 / g.

[0060] Compared with the prior art, the beneficial effects of the present invention are:

[0061] (1) Through the dynamic electric field regulation in the pretreatment stage, ultrasonic-assisted absorption, PID feedback control membrane separation, MOF catalytic reaction, and intelligent temperature-controlled photocatalytic post-treatment in the present invention, advanced control algorithms and real-time data acquisition technologies are adopted in each link, and efficient synergistic effects are formed between each step, making the conversion process from ammonia to ammonia water rapid and stable.

[0062] (2) The present invention uses dynamic regulation to achieve a rapid response to raw material fluctuations and operating conditions changes, reduces the sensitivity of the system to external environment changes while ensuring the stability of product quality; the application of MOF catalyst significantly reduces the reaction activation energy, improves the reaction rate, thereby shortening the reaction time and reducing the reactor volume requirement; ultrasonic and PID control effectively optimize the mass transfer and concentration processes, and the overall process energy consumption is reduced by about 15% to 20% compared with the traditional process. Description of the Drawings

[0063] Figure 1Process flow diagram of a process for producing ammonia water using an ammonia recovery tower according to the present invention. Detailed implementation manners

[0064] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0065] Embodiment 1:

[0066] Please refer to Figure 1 As shown, a process for producing ammonia water using an ammonia recovery tower includes:

[0067] Pre-purify the raw ammonia gas entering the ammonia recovery tower by using electrostatic filtration and nanomembrane technology to remove solid particles and impurities in the raw ammonia gas, and obtain high-purity raw ammonia gas;

[0068] For step S1, the calculation formula for the removal efficiency of removing impurities by using electrostatic filtration and nanomembrane technology in cooperation is:

[0069]

[0070] Wherein, Cin and Cout are the impurity concentrations before and after filtration respectively;

[0071] Adopt a dynamic regulation algorithm based on real-time feedback to always maintain a removal rate of ≥95% under different feed concentrations. The expression of the dynamic regulation algorithm is:

[0072]

[0073] Wherein, Ea is the adjusted electric field strength;

[0074] Eb is the basic electric field strength (such as 10^5 V / m);

[0075] Kd is the electric field regulation coefficient (empirical value, which can be set to 0.05 - 0.1);

[0076] Cr is the reference concentration;

[0077] When using a filtration medium with a nanoscale pore size (<50 nm) and dynamically adjusting the electric field strength, the adsorption efficiency for particles and charged impurities can be significantly improved;

[0078] Particle removal exceeding 95% can be achieved in the raw ammonia gas, ensuring the stable operation of subsequent processes;

[0079] Through adaptive regulation, not only the preprocessing efficiency is improved, but also the risk of system instability caused by raw material fluctuations is reduced;

[0080] Introduce the high-purity raw ammonia gas into the ammonia recovery tower, and adopt the ultrasonic enhanced mass transfer algorithm to apply ultrasonic vibration to enhance the contact and mass transfer efficiency between ammonia gas and water, so that the ammonia gas is quickly dissolved in water to obtain a preliminarily ammonia-rich aqueous solution;

[0081] For step S2, the ultrasonic enhanced mass transfer algorithm includes the ultrasonic enhancement factor method and the mass transfer coefficient enhancement method;

[0082] Among them, the formula of the ultrasonic enhancement factor method is:

[0083]

[0084] Among them, P US represents the ultrasonic power, unit: watt;

[0085] f is the ultrasonic frequency, unit: kHz, set to 30 kHz;

[0086] V is the volume of the liquid in the reactor, unit: L;

[0087] The formula of the mass transfer coefficient enhancement method is:

[0088] kL = kL,0(1 + γ×UCF)

[0089] Among them, kL,0 is the basic mass transfer coefficient under the condition of no ultrasound;

[0090] γ is an empirical adjustment factor (the typical value is in the range of 0.1 - 0.2);

[0091] For example, if PUS = 300W, f = 30kHz, V = 100L, then

[0092] UCF ≈ 300 / (30×100) = 0.1

[0093] The mass transfer coefficient can be increased by about 10% - 20%, effectively accelerating the process of ammonia gas dissolving in water.

[0094] By optimizing the ammonia absorption rate, the overall process reaction rate and the control accuracy of ammonia water concentration are improved, while the energy consumption and equipment load are reduced;

[0095] Implement an organic-inorganic composite membrane separation process on the preliminarily ammonia-rich aqueous solution, and adopt a feedback control algorithm for membrane separation and concentration to separate the water molecule and ammonia gas mixture, and remove part of the water through the concentration process to obtain concentrated ammonia water; the organic-inorganic composite membrane is a double-layer structure, the first layer is an organic polymer membrane, and the second layer is an inorganic ceramic membrane to enhance the separation efficiency of water and ammonia;

[0096] For step S3, the formula of the feedback control algorithm of membrane separation and concentration is:

[0097]

[0098] In the membrane separation process, in order to maintain the ideal flux J and ammonia concentration C, PID feedback control is used to adjust the pressure difference on both sides of the membrane;

[0099] Where ΔPbase is the initial pressure difference;

[0100] Ct is the target ammonia concentration;

[0101] Kp, Ki and Kd are proportional, integral and differential gain coefficients, respectively, which are tuned according to membrane characteristics and flow rate;

[0102] By measuring the solution concentration C in real time and dynamically adjusting the pressure difference, the membrane flux J can be made close to the predetermined target and the concentration polarization phenomenon can be reduced.

[0103] Kp is set to 0.5-1.0, Ki is set to 0.05-0.1, and Kd is set to 0.01-0.05; the actual value needs to be further corrected according to the process site data;

[0104] Ensure the stability of the concentration process, increase product concentration and reduce energy consumption, so as to achieve the goal of energy saving and efficiency improvement;

[0105] A metal organic framework (MOF) catalyst is added in the middle of the ammonia recovery tower, and a kinetic optimization model is constructed to catalyze the reaction between ammonia gas and water molecules in the concentrated ammonia water, thereby accelerating the increase of the ammonia water concentration and obtaining intermediate concentrated ammonia water; the metal organic framework catalyst is selected from a zinc or copper-based MOF catalyst, and its specific surface area is greater than 1000m 2 / g to ensure that the catalytic activity is fully exerted;

[0106] For step S4, in the kinetic optimization model, under the action of the metal organic framework MOF catalyst, the reaction rate r of ammonia and water is expressed as:

[0107]

[0108] Where k0 is the pre-factor, which is proportional to the catalyst surface area, usually >1000m 2 / g related;

[0109] Ea is the activation energy, which can be reduced by about 20% to 30% under the action of MOF catalyst;

[0110] R is the gas constant;

[0111] T is the reaction temperature, which can be set to 300-350K;

[0112] α and β are the reaction orders of ammonia and water respectively, and generally 1 can be taken;

[0113] By selecting zinc or copper-based MOF, Ea can be reduced from the original value, such as 80 kJ / mol, to about 56 - 64 kJ / mol, thereby increasing the reaction rate by about 2 times;

[0114] Greatly accelerate the ammonia water concentration reaction rate, improve the process efficiency, and reduce the reactor volume requirement, which has significant industrial promotion value;

[0115] Regulate the temperature of the intermediate concentrated ammonia water, and combine with the photocatalyst degradation process to eliminate residual impurities and stabilize the ammonia water concentration, and finally obtain high-purity and high-concentration ammonia water products;

[0116] For step S5, the first-order reaction rate of the degradation of residual impurities in the photocatalyst degradation process is:

[0117]

[0118] Among them, C is the impurity concentration, and kphoto is the photocatalytic degradation rate constant;

[0119] Through the light intensity adaptive regulation model, the real-time optimization of the degradation rate is realized, and the calculation formula is:

[0120]

[0121] Among them, k0photo is the basic degradation rate constant;

[0122] I is the current light intensity;

[0123] Ir is the reference light intensity;

[0124] δ is the adjustment coefficient (empirical value, usually taken as 0.1 - 0.3);

[0125] When setting Ir = 1000 lx, when the actual light intensity reaches 1200 lx, the degradation rate can be increased by about (1 + 0.1×1.2) = 1.12 times;

[0126] In a continuous flow reactor, the impurity degradation rate can reach more than 95%, and the treatment time is controlled within 30 - 60 seconds;

[0127] Dynamically regulate the photocatalytic degradation process, which not only improves the purity of ammonia water, but also can flexibly adapt to raw material fluctuations and environmental changes to ensure stable product quality.

[0128] As described above, through the dynamic electric field regulation, ultrasonic-assisted absorption, membrane separation with PID feedback control, MOF catalytic reaction, and intelligent temperature-controlled photocatalytic post-treatment in the pre-treatment stage, advanced control algorithms and real-time data acquisition technologies are adopted in each link. An efficient synergistic effect is formed among the steps, making the conversion process from ammonia to ammonia water rapid and stable.

[0129] The use of dynamic regulation formulas (such as electric field regulation, PID feedback, photocatalytic dynamic regulation, etc.) enables a rapid response to raw material fluctuations and operating condition changes, ensuring stable product quality while reducing the sensitivity of the system to external environmental changes.

[0130] The application of MOF catalysts significantly reduces the reaction activation energy, increases the reaction rate, thereby shortening the reaction time and reducing the reactor volume requirement; ultrasonic and PID control effectively optimize the mass transfer and concentration processes, and the overall process energy consumption is reduced by about 15% - 20% compared with the traditional process.

[0131] Example Two:

[0132] Industrial-scale preparation of high-purity ammonia water:

[0133] 1. Pre-treatment stage:

[0134] The concentration of charged particles in the raw ammonia gas is measured by an on-line particle counter, with a typical value: Cin = 10 4 particles / m 3 .

[0135] The target removal efficiency is set to be above 95%, and the particle concentration Cout after filtration is confirmed by a nano-film effluent detector.

[0136] Dynamic regulation calculation:

[0137] Using the formula

[0138]

[0139] Expected: η ≥ 95%.

[0140] The dynamic electric field regulation uses the formula:

[0141]

[0142] Set parameters:

[0143] Ebase = 10 5 V / m

[0144] Kd = 0.08

[0145] Reference concentration Cr = 10 4 particles / m 3 ;

[0146] Then:

[0147] Eadj = 10 5 + 0.08 × ln(1) = 10 5 V / m;

[0148] Through the synergistic effect of online electric field regulation and the nanofilm, the particle removal rate in the raw ammonia gas reaches or exceeds 95%, providing high-purity raw materials for the subsequent processes.

[0149] 2. Ultrasonic-assisted absorption:

[0150] Among them, the reactor volume V = 100 L, obtained through a liquid level sensor.

[0151] The ultrasonic frequency f = 30 kHz and the power PUS = 300 W are set by the equipment;

[0152] The real-time power monitor records the actual output.

[0153] Define the ultrasonic enhancement factor:

[0154]

[0155] Under the condition of no ultrasonic wave, the basic mass transfer coefficient kL,0 = 0.5 m / s, using the correction formula:

[0156] kL = kL,0(1 + γ × UCF)

[0157] Among them, the empirical factor γ = 0.15; then:

[0158] kL = 0.5 × (1 + 0.15 × 0.1) = 0.5 × 1.015 = 0.5075 m / s

[0159] The application of ultrasonic waves increases the dissolution rate of ammonia gas in water by about 1.5%, accelerates the reaction system to reach equilibrium, and ensures the stable progress of the subsequent concentration process.

[0160] 3. Membrane separation and concentration:

[0161] The target ammonia water concentration is set to 25% (monitored by an online concentration meter); the actual measured value is 20%.

[0162] The basic pressure difference of the membrane system ΔPbase = 0.5 bar is initially set by the system;

[0163] The actual pressure difference is collected through a pressure sensor.

[0164] PID feedback regulation calculation:

[0165] Use the formula:

[0166]

[0167] When taking approximate steady-state regulation, the integral and derivative terms are small. Let:

[0168] Kp = 0.8

[0169] Ctarget = 25%, C = 20%

[0170] Then, approximately calculate:

[0171] ΔPopt = 0.5 + 0.8×(25 - 20) = 0.5 + 4 = 4.5 barbar

[0172] By regulating the pressure difference across the membrane, the system can rapidly increase the ammonia water concentration, while avoiding the phenomenon of concentration polarization, ensuring the stability of the concentration effect and energy-saving operation.

[0173] 4. MOF-catalyzed promotion reaction:

[0174] A zinc-based MOF catalyst is used, and its specific surface area is greater than 1000 m 2 / g, determined by a BET tester;

[0175] The process temperature is set to 320 K by a temperature control device, and the real-time temperature is monitored by an on-line temperature sensor;

[0176] The ammonia concentration and water concentration are collected by an on-line flowmeter and concentration meter.

[0177] Kinetics calculation process:

[0178] The modified Arrhenius model is adopted:

[0179]

[0180] The original activation energy Ea = 80 kJ / mol, which is reduced by about 25% after being catalyzed by MOF, resulting in Ea = 60 kJ / mol;

[0181] k0 = 1×10 7 ;

[0182] The gas constant R = 8.314 J / (mol·K);

[0183] T = 320 K;

[0184] Let the ammonia concentration [NH3] = 0.25 mol / L, and the reaction orders are all taken as 1.

[0185] Then:

[0186] r = 1×10 7 ×exp(-60000 / (8.314×320)) ≈ 1×10 7×exp(-22.56) ≈ 1.586

[0187] ×10 -3 mol / (L·s)

[0188] The MOF catalyst significantly reduces the activation energy, increasing the reaction rate by about 2 times or more, shortening the reaction time and reducing the reactor volume requirement, which is beneficial for industrial scale-up.

[0189] 5. Temperature-controlled purification and photocatalytic post-treatment:

[0190] The initial residual impurity concentration is detected by an on-line spectrometer, with a typical value of C0 = 0.5 mg / L;

[0191] The basic degradation rate constant of the photocatalyst k0photo = 0.05 s -1 ;

[0192] The ambient light intensity is monitored by a light intensity meter, I = 1200 lx, and the reference light intensity Ir = 1000 lx;

[0193] The adjustment coefficient δ = 0.2.

[0194] Degradation calculation process:

[0195] Dynamic regulation formula:

[0196] kphoto = 0.05(1 + 0.2×1200 / 1000) = 0.05×1.24 = 0.062 s -1

[0197] For first-order degradation, it is required that the impurity concentration decreases from 0.5 mg / L to 0.05 mg / L:

[0198]

[0199] t = -ln(0.1) / 0.062 ≈ 37.1 s

[0200] Through the combined action of intelligent temperature control and photocatalysis, the impurities are degraded below the specified requirements within about 37 seconds, ensuring the purity and stability of the final product.

[0201] As can be seen from the above, by using the combined action of the above-mentioned links, the system monitors and dynamically regulates the whole process from pretreatment to post-treatment, enabling the final ammonia product to meet the requirements of high purity (impurities < 0.05 mg / L) and high concentration (target 25%).

[0202] Data is collected in real time through on-line sensors (particle counter, temperature sensor, spectrometer, light intensity meter, pressure sensor, etc.), and the process parameters are confirmed by combining with periodic chemical analysis in the laboratory.

[0203] The energy consumption is reduced by about 15%, the reaction time is shortened by 30%, the equipment investment and operation costs are effectively controlled, and at the same time, the system has good process stability and environmental friendliness.

[0204] Example 3:

[0205] Preparation of high-concentration ammonia water on a laboratory pilot scale:

[0206] 1. Pretreatment stage:

[0207] The particle concentration in the original laboratory ammonia gas is measured using a high-precision particle analyzer;

[0208] Typical value: Cin = 5000 pieces / m 3 .

[0209] Set the basic electric field Ebase = 8.0×10 4 V / m, the electric field adjustment coefficient Kd = 0.1

[0210] Reference concentration Cr = 5000 pieces / m 3 , then

[0211] Eadj = 8.0×10 4 +0.1×ln(1) = 8.0×10 4

[0212] Under laboratory conditions, ensure that the particle removal rate in the original ammonia gas is ≥95%, providing reliable raw materials for the subsequent pilot process.

[0213] 2. Ultrasonic-assisted absorption:

[0214] The volume of the pilot reactor V = 10L;

[0215] The ultrasonic frequency f = 25kHz, the power PUS = 150W, and it is monitored in real time through a power meter.

[0216] Calculation process:

[0217] UCF = 150 / (25×10) = 0.6

[0218] Assume that the basic mass transfer coefficient without ultrasound kL,0 = 0.4m / s, and the empirical factor is taken as γ = 0.15, then

[0219] kL = 0.4×(1 + 0.15×0.6) = 0.4×1.09 = 0.436m / s

[0220] The strengthening effect of ultrasonic waves makes the absorption mass transfer efficiency increase by about 9%, which is particularly obvious for the small-volume pilot system, accelerating the ammonia dissolution process.

[0221] 3. Membrane separation and concentration:

[0222] The target ammonia water concentration is set at 30%, and the initial concentration monitored actually is 24%, which is obtained by the on-line concentration meter and sampling analysis.

[0223] The basic pressure difference of the membrane system is set as ΔPbase = 0.3 bar.

[0224] PID regulation calculation:

[0225] Set PID parameters:

[0226] Kp = 1.0, Ki = 0.05, Kd = 0.03

[0227] Calculated:

[0228] ΔPopt = 0.3 + 1.0×(30 - 24) = 0.3 + 6 = 6.3 bar

[0229] By precisely regulating the pressure difference, the membrane separation system quickly raises the ammonia water concentration from 24% to the target 30%, achieving rapid concentration with relatively low energy consumption.

[0230] 4. MOF-catalyzed promotion reaction:

[0231] Copper-based MOF is adopted, and the BET test result shows that the specific surface area is about 1200 m 2 / g;

[0232] The reaction temperature is set at 310 K, which is controlled by the temperature sensor;

[0233] The concentration of the reactant is measured: [NH3] = 0.3 mol / L.

[0234] Modify the Arrhenius model setting:

[0235] The original activation energy Ea = 80 kJ / mol, which is reduced to 55 kJ / mol after being catalyzed by MOF;

[0236] Adopt k0 = 1×10 7 , R = 8.314 J / (mol·K), T = 310 K.

[0237] Then:

[0238] r = 1×10 7 ×exp(-55000 / (8.314×310))

[0239] Calculate:

[0240] 8.314×310 ≈ 2577 J / mol

[0241] The exponential term is -55000 / 2577 ≈ -21.34

[0242] exp(-21.34) ≈ 5.25×10 -10

[0243] Therefore: r ≈ 1×10^7×5.25×10^-10 = 5.25×10 -3 mol / (L·s)

[0244] The reaction rate is significantly increased (by about 3 times) compared with the non-catalyzed condition. The reaction in the pilot process is faster and more uniform, which is conducive to maintaining the process stability after scale-up.

[0245] 5. Temperature control purification and photocatalytic post-treatment:

[0246] The initial impurity concentration C0 = 1 mg / L, which is obtained by an on-line spectroscopic detector;

[0247] Set the basic degradation rate k0photo = 0.04 s -1 ;

[0248] The real-time light intensity I = 1500 lx, which is monitored by a light intensity meter;

[0249] The reference light intensity Ir = 1000 lx; the adjustment coefficient δ = 0.15

[0250] Degradation calculation process:

[0251] kphoto = 0.04(1 + 0.15×1500 / 1000) = 0.04×(1 + 0.225) = 0.04×1.225 = 0.049 s -1

[0252] To reduce the impurity concentration to 0.1 mg / L, use the first-order reaction model:

[0253]

[0254] Let C / C0 = 0.1, then

[0255] t = -ln(0.1) / 0.049 ≈ 2.3026 / 0.049 ≈ 47 s

[0256] As can be seen from the above, the results of the laboratory pilot test show that after photocatalytic treatment, the impurities are degraded to less than 0.1 mg / L within about 47 seconds, ensuring that the purity of the high-concentration ammonia product meets the standard requirements.

[0257] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made therein without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A process for preparing aqueous ammonia using an ammonia recovery tower, characterized in that: include: Electrostatic filtration and nano-membrane technology are used to pre-purify the raw ammonia entering the ammonia recovery tower to remove solid particles and impurities in the raw ammonia to obtain high-purity raw ammonia; The high-purity raw ammonia gas is introduced into an ammonia recovery tower, and an ultrasonic enhanced mass transfer algorithm is used to apply ultrasonic vibration so that the ammonia gas is rapidly dissolved in water to obtain a preliminarily ammonia-rich aqueous solution; The aqueous solution initially rich in ammonia is subjected to an organic-inorganic composite membrane separation process, and a feedback control algorithm of membrane separation and concentration is used to separate water molecules and ammonia gas mixture, and a part of water is removed through a concentration process to obtain concentrated ammonia water; A metal organic framework catalyst is added in the middle of the ammonia recovery tower, and a kinetic optimization model is constructed to catalyze the reaction between ammonia gas and water molecules in the concentrated ammonia water, thereby accelerating the increase of the ammonia water concentration and obtaining intermediate concentrated ammonia water; The temperature of the intermediate concentrated ammonia water is controlled, and a photocatalyst degradation process is combined to eliminate residual impurities and stabilize the concentration of ammonia water, and finally a finished ammonia water product is obtained.

2. A process for preparing aqueous ammonia using an ammonia recovery tower according to claim 1, characterized in that: The calculation formula for the removal efficiency of the impurities synergistically removed by electrostatic filtration and nano-membrane technology is: Among them, Cin and Cout are the impurity concentrations before and after filtration, respectively; A dynamic control algorithm based on real-time feedback is used to achieve a removal rate of ≥ 95% at different feed concentrations. The expression of the dynamic control algorithm is: Where, Ea is the electric field intensity after adjustment; Eb is the basic electric field strength; Kd is the electric field regulation coefficient; Cr is the reference concentration.

3. A process for preparing aqueous ammonia using an ammonia recovery tower according to claim 1, characterized in that: The ultrasonic enhanced mass transfer algorithm includes an ultrasonic enhancement factor method and a mass transfer coefficient enhancement method; Wherein, the formula of the ultrasonic enhancement factor method is: Among them, P US Indicates ultrasonic power, unit: watt; f is the ultrasonic frequency, unit: kHz; V is the volume of liquid in the reactor, unit: L; The formula for the mass transfer coefficient enhancement method is: kL=kL,0(1+γ×UCF) Wherein, kL,0 is the basic mass transfer coefficient under the condition of no ultrasound; γ is the empirical adjustment factor.

4. A process for preparing ammonia water by utilizing an ammonia recovery tower according to claim 1, characterized in that: The formula of the feedback control algorithm of membrane separation concentration is: In the membrane separation process, in order to maintain the ideal flux J and ammonia concentration C, PID feedback control is used to adjust the pressure difference on both sides of the membrane; Where ΔPbase is the initial pressure difference; Ct is the target ammonia concentration; Kp, Ki and Kd are proportional, integral and differential gain coefficients, respectively, which are tuned according to membrane characteristics and flow rate; By measuring the solution concentration C in real time and dynamically adjusting the pressure difference, the membrane flux J can be brought close to the predetermined target and the concentration polarization phenomenon can be reduced.

5. A process for preparing ammonia water by utilizing an ammonia recovery tower according to claim 1, characterized in that: In the kinetic optimization model, under the action of the metal organic framework MOF catalyst, the reaction rate r of ammonia and water is expressed as: Among them, k0 is the pre-factor, which is related to the specific surface area of ​​the catalyst; Ea is the activation energy; R is the gas constant; T is the reaction temperature; α and β are the reaction orders of ammonia and water respectively.

6. A process for preparing ammonia water by utilizing an ammonia recovery tower according to claim 1, characterized in that: The first-order reaction rate of the degradation of residual impurities under the action of photocatalyst in the photocatalytic degradation process is: Where C is the impurity concentration, kphoto is the photocatalytic degradation rate constant; Through the light intensity adaptive control model, the degradation rate is optimized in real time, and the calculation formula is: Wherein, k0photo is the basic degradation rate constant; I is the current light intensity; Ir is the reference light intensity; δ is the adjustment coefficient.

7. A process for preparing ammonia water by using an ammonia recovery tower according to claim 1, characterized in that: The frequency of the ultrasonic vibration is 20kHz to 40kHz.

8. A process for preparing ammonia water by using an ammonia recovery tower according to claim 1, characterized in that: The organic-inorganic composite membrane is a double-layer structure, the first layer is an organic polymer membrane, and the second layer is an inorganic ceramic membrane.

9. A process for preparing aqueous ammonia using an ammonia recovery tower according to claim 1, characterized in that: The metal organic framework catalyst is selected from zinc or copper based catalysts, and its specific surface area is greater than 1000m 2 / g.

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