Use of near infrared spectroscopy in urea processes, and related methods and apparatus

Abstract

The use of near infrared (NIR) spectroscopy, preferably Fourier transform NIR spectroscopy, for obtaining one or more NIR spectra for determining one or more chemical substances in one or more process streams of a urea process, said urea process comprising at least one of a synthesis process, an evaporation process, a crystallization process, a waste water treatment process and / or a finishing process. In particular, the urea process comprises a urea synthesis process by reaction of carbon dioxide and ammonia. Chemical substances involved in the synthesis, such as ammonia, carbon dioxide, urea and biuret, can be quantitatively determined by NIR spectroscopy and the synthesis process can be adjusted based on the determination. The invention also relates to a urea synthesis plant employing NIR spectroscopy.

Description

Technical Field

[0001] This invention relates to analytical methods in urea synthesis processes and equipment. Specifically, this invention relates to the qualitative and quantitative determination of chemical substances in one or more process flows of urea equipment using near-infrared (NIR) spectroscopy. Background Technology

[0002] Urea is synthesized through the reaction of ammonia (NH3) and carbon dioxide (CO2) under urea-forming conditions. The reaction between NH3 and CO2 produces ammonium carbamate, which then decomposes into urea and water. A detailed description of available urea synthesis processes can be found in Meessen, JH and Petersen, H. (2000), Urea, Ullmann's Encyclopedia of Industrial Chemistry.

[0003] Biuret is a known and undesirable byproduct of conventional urea production. Efforts have been made to avoid biuret formation, or at least to keep the biuret content in urea below a certain threshold (e.g., <1.0% by weight). However, biuret can be a valuable component, serving as a source of non-protein nitrogen (NPN) in cattle feed or as a pre-planting fertilizer for crops.

[0004] Typically, the process stream in urea synthesis is analyzed using offline procedures, particularly by sampling the process stream and then analyzing it in the laboratory. More specifically, sampling is performed by collecting the process stream from a pressurized environment in a known volume of water to absorb the gases released during depressurization.

[0005] This offline program has several drawbacks. These include:

[0006] - For safety reasons, sampling from pressurized environments must be performed by at least one experienced worker;

[0007] - Despite being very careful during sampling, most volatile compounds are often lost, affecting the accuracy of the analysis;

[0008] - The sample must be properly quenched to stop the reaction kinetics;

[0009] -Even if the reaction has been properly quenched, the time delay from sampling to analysis can still affect the amount of the analyte.

[0010] - The reaction conditions differ from the analytical conditions (in terms of different pressures and temperatures), which is an additional factor that reduces analytical accuracy because different conditions can alter the chemical equilibrium.

[0011] It is impossible to monitor transient conditions because the reactor must always be stopped under the conditions of interest for analysis. This necessitates multiple samplings to obtain a complete profile of the reaction state.

[0012] Due to the high corrosiveness of ammonium carbamate, online analysis is difficult to implement; the pressure and temperature conditions during urea synthesis, the supercritical behavior of components in the synthesis section, and the presence of water with a matrix effect lead to weakening or enhancement of the response signal.

[0013] The same applicant’s WO 2015 / 189075 A1 discloses the use of Raman spectroscopy for urea process flow.

[0014] The following documents also belong to known prior art: CN101393120A, CN107703096A, KEN-ICHIROSUEHARA Rapid and Simple Determination of Oil and Urea Concentrations and Solids Content to Monitor Biodegradation Conditions of Wastewater Discharged from a Biodiesel Fuel Production Plant ", JOURNAL OF NEAR INFRAREDSPECTROSCOPY, Vol. 15, No. 2, pp. 89-96 (XP093154430), PETER B. SKOU: " Monitoring Process Water Quality Using Near Infrared Spectroscopy and Partial Least Squares Regression with Prediction Uncertainty Estimation ", APPLIEDSPECTROSCOPY, Vol. 71, No. 3, pp. 410-421 (XP093155271) and JING LIU: " A diffuse reflectance portable near infrared spectroscopy system for the determination of biuret content in urea fertilizer ", JOURNAL OF NEAR INFRARED SPECTROSCOPY, Vol. 31, No. 1, pp. 33-40 (XP093155259).

[0015] In light of the above, there is an increasing need for more precise analysis to obtain a better picture of the urea plant flow. Summary of the Invention

[0016] The object of this invention is to overcome the aforementioned deficiencies. This invention relates to methods, apparatus, and uses according to the appended independent claims. Preferred embodiments are described in the dependent claims.

[0017] One object of the present invention is a method comprising the following steps:

[0018] (I) Ammonia and carbon dioxide are reacted in the urea synthesis section to obtain urea or biuret-containing urea, for example, high biuret urea.

[0019] (II) Near-infrared (NIR) spectroscopy analysis is performed on one or more process flows of the urea synthesis section to obtain one or more NIR spectra, thereby qualitatively determining one or more chemical substances in the one or more process flows;

[0020] (III) Process the one or more NIR spectra to obtain a quantitative determination of the one or more chemical substances.

[0021] Another object of the present invention is an apparatus comprising:

[0022] (A) Urea synthesis section, in which ammonia and carbon dioxide react to obtain urea or biuret-containing urea, such as high biuret urea;

[0023] (B) One or more near-infrared (NIR) spectral probes located at one or more process flows in the urea synthesis section;

[0024] (C) At least one NIR spectroscopy device, which is functionally connected to the NIR spectroscopy probe to obtain one or more NIR spectra;

[0025] (D) At least one processing unit of the one or more NIR spectra, configured to obtain a quantitative determination of the one or more chemical substances.

[0026] Another object of the present invention is the use of near-infrared (NIR) spectroscopy to obtain one or more NIR spectra and thereby determine one or more chemical substances in one or more process streams of a urea process, said urea process including at least one of a synthesis process, an evaporation process, a crystallization process, a wastewater treatment process, and / or a finishing process.

[0027] In practice, this invention allows for the determination of one or more chemical substances within the process flow of a urea process (preferably urea synthesis) using one or more NIR spectra. Such one or more NIR spectra provide direct qualitative information about the chemical substance, as well as quantitative information about the chemical substance after appropriate processing.

[0028] Description of preferred embodiments of the present invention

[0029] According to possible implementations, the urea obtained in step (I) can be an aqueous urea solution or a urea melt (i.e., high-concentration urea). The concentration of the urea melt is typically equal to or greater than 98% by weight, preferably equal to or greater than 99% by weight, more preferably equal to or greater than 99.5% by weight, and even more preferably equal to or greater than 99.7% by weight, wherein the balance is water and / or unavoidable impurities. Preferably, the urea melt is formaldehyde-free.

[0030] Preferably, the biuret-containing urea is high-biuret urea, which contains at least 45% by weight, more preferably 45% to 80% by weight, even more preferably 50% to 75% by weight, and still more preferably 55% to 70% by weight of biuret relative to the total weight of the biuret-containing urea.

[0031] Urea containing biuret can be obtained according to the method disclosed in WO 2022 / 106083 A1, which defines urea containing biuret as high-biuret urea. See page 11, line 11 to page 12, line 9 of WO 2022 / 106083 A1 for details.

[0032] According to one embodiment, the biuret-containing urea may contain 2% to 30% by weight, preferably 5% to 25% by weight, and more preferably 10% to 20% by weight of triuret relative to the total weight of the biuret-containing urea.

[0033] Preferably, the urea synthesis section or process is a high-pressure synthesis section or process.

[0034] According to a first preferred embodiment, the one or more process flows are liquid process flows. Preferably, the one or more liquid process flows are aqueous process flows.

[0035] According to the second preferred embodiment, the one or more process flows are gaseous process flows.

[0036] According to different implementation schemes, the process flow includes the high-pressure urea reactor, high-pressure stripping tower, high-pressure condenser, and / or high-pressure scrubber used in or within the high-pressure urea synthesis section or process; and / or the process flow is the feed flow and / or effluent flow of the high-pressure urea reactor, high-pressure stripping tower, high-pressure condenser, and / or high-pressure scrubber, and / or low-pressure section (e.g., low-pressure recovery section) used in or within the high-pressure urea synthesis section or process. Preferably, the process flow is one or more effluent flows.

[0037] Possible examples of process flows include flows contained within a high-pressure urea reactor, effluent from a high-pressure urea reactor, flows contained within a high-pressure carbamate condenser, effluent from a high-pressure carbamate condenser, flows contained within a high-pressure scrubber, effluent from a high-pressure scrubber, flows contained within a high-pressure stripper, concentrated effluent from a high-pressure stripper, flows contained within a low-pressure recovery section of a carbamate-containing solution, or effluent from a low-pressure recovery section of a carbamate-containing solution.

[0038] Other examples of process flows include effluents from synthesis sections or processes (e.g., urea-containing effluents, water-containing effluents, and / or ammonium carbamate-containing effluents), urea-containing and water-containing effluents from recovery sections, urea-containing melt effluents from evaporators, or biuret-containing effluents from urea reactors.

[0039] According to one embodiment, the NIR spectral analysis is Fourier transform-near infrared (FT-NIR) spectral analysis. Preferably, a single NIR spectrum is the result of multiple spectral acquisitions (e.g., at least five, at least ten, at least fifteen, or at least twenty different spectral acquisitions).

[0040] For example, Bruker's MATRIX-F II NIR Fourier transform spectrometer (according to ATEX) can be used. As another example, each spectrum can be acquired using Bruker's OPUS / QUANT2 software. This software (or a similar program) can be used to evaluate key parameters of each characteristic peak, such as area, height, and / or position / shift (wavenumber).

[0041] According to another embodiment, the NIR spectral analysis covers 12500 cm⁻¹ -1 Up to 4000 cm -1 The preferred region of the electromagnetic spectrum is 12000 cm⁻¹. For the purposes of this invention, the preferred region of the electromagnetic spectrum is 12000 cm⁻¹. -1 Up to 7500 cm -1 Or 11995 cm -1 Up to 7355 cm -1 Therefore, the one or more NIR spectral probes and the at least one NIR spectral device are preferably configured to cover the same region of the electromagnetic spectrum.

[0042] According to one possible implementation, the optical length of the NIR spectral analysis is 2 mm to 20 mm, preferably 4 mm to 15 mm, and more preferably 5 mm to 10 mm. Therefore, the one or more NIR spectral probes and the at least one NIR spectral device are preferably configured to cover the same optical length.

[0043] Preferably, the determination (step (II)) includes real-time determination and in-situ determination of the chemical substance in the process flow, or consists of real-time determination and in-situ determination of the chemical substance in the process flow.

[0044] According to a preferred embodiment, the acquisition of one or more NIR spectra is performed without sampling the one or more process streams. In other words, the one or more process streams are not sampled prior to the acquisition or execution of step (II).

[0045] In the specification, “sampling” means collecting or removing a portion of the process stream from its environment, said portion being selected as a sample for inspection or analysis, particularly for obtaining one or more NIR spectra.

[0046] The chemical substance is preferably selected from ammonia, carbon dioxide, ammonium carbamate, water, urea, biuret, triuret, cyanuric acid, and combinations thereof.

[0047] According to the first embodiment, the chemical substance may be ammonia and carbon dioxide, and / or water and carbon dioxide, and / or ammonia and urea, and / or urea and carbon dioxide, and / or ammonium carbamate.

[0048] According to the second embodiment, the chemical substance is urea, biuret, and water.

[0049] According to the third embodiment, the chemical substances are urea, biuret, triuret, cyanuric acid, and water.

[0050] According to the fourth embodiment, the chemical substance is at least ammonia, carbon dioxide, water, urea, and biuret, and optionally ammonium carbamate.

[0051] Preferably, the qualitative determination in step (II) includes identifying characteristic peaks of the one or more chemical substances in the NIR spectrum at a specific temperature (T) and a specific pressure (P).

[0052] Generally, these specific temperatures and pressures correspond to the temperature and pressure values ​​of the process flow at a specific location in the urea plant. For example, the specific temperature and pressure may correspond to the urea formation conditions.

[0053] According to one embodiment, the specific temperature is room temperature to 300°C, preferably 40°C to 280°C, and more preferably 50°C to 250°C.

[0054] According to another implementation, the specific pressure is 80 bar to 350 bar, preferably 90 bar to 325 bar, and more preferably 100 bar to 300 bar.

[0055] According to a preferred embodiment, the quantitative determination in step (III) includes applying chemometric methods to the NIR spectral data. Preferably, the NIR spectral data includes characteristic peak areas / intensities. For example, software (e.g., Bruker's OPUS software, such as OPUS / QUANT2 software) can be used to apply the chemometric methods. Preferably, the chemometric methods are partial least squares (PLS) regression, and / or principal component regression (PCR), and / or multiple linear regression (MLR), or include partial least squares (PLS) regression, and / or principal component regression (PCR), and / or multiple linear regression (MLR). PLS regression is preferred.

[0056] Preferably, the chemometric method includes multivariate calibration.

[0057] Chemometric methods utilize a large number of NIR spectra obtained from a series of calibration experiments with different known reference values ​​(e.g., specific temperature, specific pressure, amount of each chemical substance, amount and weight ratio of chemical substances combined with each other).

[0058] The method preferably includes:

[0059] (IV) Based on the quantitative determination in step (III), at least one of the following in the urea synthesis section is adjusted: the ammonia to carbon dioxide (N / C) equivalent ratio, the water to carbon dioxide (H / C) equivalent ratio, and the urea to carbon dioxide (U / C) equivalent ratio.

[0060] According to possible implementations, the N / C ratio and / or H / C ratio are adjusted based on the quantitative determination of the following process streams in step (III): urea reactor liquid effluent, and / or high-pressure carbamate condenser liquid effluent, and / or high-pressure stripping tower effluent.

[0061] Taking the liquid effluent from a urea reactor as an example, if the measured H / C ratio is too high, i.e. higher than the reference value, the water purging can be increased to reduce the H / C ratio to or below the reference value.

[0062] According to another implementation, the N / C ratio can be adjusted by changing the composition of the inlet reactor or the operating conditions upstream and / or downstream of the reactor.

[0063] Preferably, the device does not have one or more sampling means (e.g., sampling device or sampling apparatus) for the process flow.

[0064] More preferably, the device also includes:

[0065] (E) An adjustment device for at least one of the ammonia to carbon dioxide (N / C) equivalent ratio, the water to carbon dioxide (H / C) equivalent ratio, and the urea to carbon dioxide (U / C) equivalent ratio in the urea synthesis section, the adjustment device being functionally connected to the processing unit such that the adjustment of the adjustment device is based on the quantitative determination;

[0066] Even more preferably, the one or more NIR spectral probes are located in the high-pressure urea reactor, high-pressure stripping tower, high-pressure condenser, and / or high-pressure scrubber of the urea synthesis section; and / or at the feed stream and / or effluent stream of the high-pressure urea reactor, high-pressure stripping tower, high-pressure condenser, and / or high-pressure scrubber of the urea synthesis section, and / or at the effluent stream of the low-pressure recovery section (preferably at the effluent stream).

[0067] According to one embodiment, the NIR spectral probe is connected to the processing unit via an optical fiber.

[0068] According to another embodiment, the processing unit includes or is composed of a programmable logic controller (PLC).

[0069] Advantages of the present invention

[0070] Advantageously, due to the corrosion-resistant NIR spectral probe (e.g., made by VDM) ® The preferred implementation of the probe (made of Alloy 59 or another corrosion-resistant alloy) allows NIR spectroscopy to operate under high pressure and high temperature and to resist highly corrosive environments, such as in the presence of ammonium carbamate solution.

[0071] Advantageously, NIR spectroscopy allows for the rapid and non-destructive acquisition of the NIR spectrum of the bulk material. Due to its relatively long optical length, the NIR spectrum also covers chemical substances located at a certain depth from the surface. For illustrative purposes, the absorption coefficient in the NIR spectral range is relatively low, requiring a considerably long optical length (typically 2 mm to 20 mm, preferably 4 mm to 15 mm, more preferably 5 mm to 10 mm).

[0072] Advantageously, the method of the present invention allows for real-time and in-situ evaluation of chemical substances of interest, and thus obtains a practical picture of the reaction process and the formation of final byproducts.

[0073] Advantageously, the present invention avoids sampling the process flow, thus enabling the determination of chemical substances in its environment, making the reaction conditions and analytical conditions identical.

[0074] Advantageously, compared with the analytical methods currently available for urea synthesis, the method of the present invention provides better control, improvement or optimization of process parameters.

[0075] Advantageously, analyses performed using NIR spectroscopy do not actually require sample preparation.

[0076] Advantageously, this method allows NIR spectra to be acquired almost simultaneously at different locations using a single NIR spectrometer connected to multiple NIR spectral probes. This simultaneous monitoring of multiple different process flows enables the determination of how adjustments to one or more parameters at a particular location affect other downstream process flows.

[0077] Advantageously, this method is suitable for determining chemical substances in the gas and liquid phases.

[0078] Advantageously, the sampling rate of the method of the present invention is not particularly limited and can be in the range of detection per minute to detection per hour or a specific number of hours.

[0079] Advantageously, the present invention allows water to be avoided at 4000 cm. -1 Up to 7300 cm -1 This can cause signal saturation defects in certain areas.

[0080] Advantageously, the optical length was chosen to be short enough to avoid saturation of the water absorption band, while also being long enough to allow for the measurement of other species. The compromise between these two requirements was well achieved.

[0081] The invention will now be further described with reference to preferred embodiments and with the aid of the accompanying drawings. Attached Figure Description

[0082] Figure 1 : A graph showing the change in urea concentration (expressed as a weight percentage) over time for two reactions at a constant temperature. In the lower curve—related to the decomposition of urea to produce ammonia and carbon dioxide—the urea concentration decreases over time after 40 minutes. In the upper curve—related to the decomposition of ammonium carbamate to produce urea and water—the urea concentration gradually increases after 30 minutes, i.e., after the solid urea has completely melted and the reaction has reached equilibrium. Detailed Implementation

[0083] In step (I) of this method, ammonia and carbon dioxide react in the urea synthesis section to obtain urea or biuret-containing urea.

[0084] In step (II), near-infrared (NIR) spectroscopy is performed on one or more process streams of the urea synthesis section to obtain one or more NIR spectra. The one or more NIR spectra contain data (especially characteristic peaks) that allow for qualitative determination of one or more chemical substances in the one or more process streams.

[0085] In the subsequent step (III), the one or more NIR spectra are processed to obtain a quantitative determination of the one or more chemical substances.

[0086] Steps (II) and (III) are preferably performed in real-time mode, and it is preferable not to sample one or more process flows.

[0087] The qualitative determination in step (II) involves identifying characteristic peaks of the one or more chemical substances in the one or more NIR spectra at specific temperatures and pressures. The temperature and pressure are determined by the conditions of the specific process flow.

[0088] The quantitative determination in step (III) involves applying chemometric methods to the data from the NIR spectra. These data include characteristic peak areas / intensities, which can be correlated with the absolute amount of chemical substances in the process stream using the chemometric methods.

[0089] Chemometric methods include multivariate calibration. Single-variable calibration is unsuitable for multi-component systems due to interference between two or more different molecules.

[0090] In optional step (IV), based on the quantitative determination in step (III), at least one of the ammonia to carbon dioxide (N / C) equivalent ratio, the water to carbon dioxide (H / C) equivalent ratio, and the urea to carbon dioxide (U / C) equivalent ratio is adjusted in the urea synthesis section.

[0091] Therefore, process parameters can be controlled, improved, or optimized.

[0092] The present invention will be further disclosed based on the following non-limiting embodiments.

[0093] Example

[0094] For this test, a Bruker MATRIX-F II NIR Fourier transform spectrometer (according to ATEX) was used. Spectra were acquired using OPUS / QUANT2 software, and initial spectral processing was performed using OPUS software to evaluate parameters such as area, height, and position / shift (wavenumber) of each absorption peak. An automatic integration tool for each peak was used.

[0095] Spectra were acquired in two different ways: samples were acquired every 5°C, or the spectra were repeatedly acquired every 30 seconds until the desired conditions were met. In both cases, the spectral resolution was 8 cm⁻¹. -1 A single spectrum is obtained by averaging 16 different acquisitions.

[0096] Initially, individual elements were analyzed using NIR to identify characteristic peaks for each compound. Table 1 below lists exemplary characteristic peak wavenumbers for some chemical substances (tested individually rather than as a mixture), along with the temperature (T) and pressure (P) values ​​at which these wavenumbers were obtained.

[0097] Table 1

[0098] NIR spectra of binary mixtures (ammonia and water; urea and water; etc.) were also obtained to investigate the presence of overlapping peaks. Shifts of all characteristic peaks were observed in all mixtures compared to NIR spectra performed on individual chemicals.

[0099] With the aid of other analytical techniques (e.g., HPLC for urea and acid-base titration for ammonia), binary mixtures were quantified using a univariate calibration model. Other NIR spectra were obtained for binary mixtures where the proportions of the chemicals differed and they were present at different temperatures.

[0100] NIR spectra of ternary mixtures (e.g., urea, water and ammonia; ammonium carbamate, urea and water; urea, biuret and triuret; etc.) were also obtained.

[0101] PLS regression (a specific chemometric method) involving multivariate calibration is used for quantitative purposes of ternary mixtures.

[0102] For each calibration experiment, a reference solution was prepared using weighed water and urea and placed in a reactor. The first reference NIR spectrum was then acquired. Ammonia was incorporated and added to the same solution. After the system reached equilibrium to establish interaction with ammonia, a second NIR reference spectrum was acquired. Then, a third spectrum was acquired under equilibrium conditions when a set temperature (i.e., 185 °C) was reached. The reaction was then quenched, and a sample of the solution was taken at high temperature and pressure; urea was quantified by HPLC, and ammonia by titration. In this way, reference values ​​were obtained at the end of the experiment to account for spectral changes due to increases in temperature and pressure. Different final temperatures were tested for each different component of the calibration solution, for example, from 80 °C to 185 °C.

[0103] After calibrating the compounds, it was observed that urea decomposed to produce ammonia and carbon dioxide, while ammonium carbamate decomposed to produce urea and water. Throughout the experiment, the weight percentage of urea was monitored over time.

[0104] The reaction was carried out at a temperature increased from 25°C to 185°C; the temperature was then held constant for 120 minutes to verify that equilibrium had been reached. The amounts of urea and NH3 were then quantified (HPLC and titration) and compared with NIR spectra and the areas of relative characteristic peaks. Furthermore, the reverse reaction initiated by urea and water was observed over time to verify the results and ensure that equilibrium conditions had been reached.

[0105] Figure 1 The quantitative changes of urea over time are shown in the reactions from urea to ammonia and carbon dioxide, and from ammonium carbamate to urea and water.

[0106] Once the carbamate decomposes, urea melts above 130°C, the urea concentration becomes more stable (after about 30 minutes), and the production or decomposition trend becomes clearly visible.

Claims

1. Near-infrared (NIR) spectroscopy, preferably Fourier transform-near-infrared (FT-NIR) spectroscopy, is used to obtain one or more NIR spectra and thereby determine one or more chemical substances in one or more process streams of a urea process, said urea process including at least one of a synthesis process, an evaporation process, a crystallization process, a wastewater treatment process, and / or a refining process.

2. The use according to the preceding claims, wherein the measurement comprises real-time measurement and in-situ measurement of the chemical substance in the process flow, or consists of real-time measurement and in-situ measurement of the chemical substance in the process flow.

3. The use according to any one of the preceding claims, wherein the acquisition of one or more NIR spectra is performed without sampling the one or more process streams.

4. The use according to any one of the preceding claims, wherein the one or more process flows are liquid process flows, and wherein the NIR spectral analysis covers 12000 cm⁻¹. -1 Up to 7500 cm -1 Or 11995 cm -1 Up to 7355 cm -1 The electromagnetic spectrum region.

5. The use according to the preceding claims, wherein the one or more liquid process flows are aqueous process flows.

6. The use according to any one of the preceding claims, wherein the chemical substance is selected from ammonia, carbon dioxide, ammonium carbamate, water, urea, biuret, triuret, cyanuric acid, and combinations thereof; preferably ammonia and carbon dioxide, and / or water and carbon dioxide, and / or urea and carbon dioxide, and / or ammonium carbamate; more preferably at least ammonia, carbon dioxide, water, urea, and biuret, and optionally ammonium carbamate.

7. The use according to any one of the preceding claims, wherein the process stream comprises a high-pressure urea reactor, a high-pressure stripping tower, a high-pressure condenser, and / or a high-pressure scrubber used in the urea synthesis process; and / or the process stream is a feed stream and / or effluent stream of the high-pressure urea reactor, the high-pressure stripping tower, the high-pressure condenser, and / or the high-pressure scrubber, and / or the low-pressure section (e.g., the low-pressure recovery section) used in the urea synthesis process.

8. A method comprising the following steps: (I) Ammonia and carbon dioxide are reacted in the urea synthesis section to obtain urea or biuret-containing urea, for example, high biuret urea. (II) Near-infrared (NIR) spectroscopy analysis is performed on one or more process flows of the urea synthesis section to obtain one or more NIR spectra, thereby qualitatively determining one or more chemical substances in the one or more process flows; (III) Process the one or more NIR spectra to obtain a quantitative determination of the one or more chemical substances.

9. The method of claim 8, wherein step (II) comprises real-time measurement and in-situ measurement of the chemical substance in the process stream or consists of real-time measurement and in-situ measurement of the chemical substance in the process stream.

10. The method according to any one of claims 8 to 9, wherein the one or more process flows are not sampled prior to the performance of step (II).

11. The method according to any one of claims 8 to 10, wherein the one or more process flows are liquid process flows, and wherein the NIR spectral analysis covers 12000 cm⁻¹. -1 Up to 7500 cm -1 Or 11995 cm -1 Up to 7355 cm -1 The electromagnetic spectrum region.

12. The method according to the preceding claims, wherein the one or more liquid process flows are aqueous process flows.

13. The method according to any one of claims 8 to 12, wherein the chemical substance is selected from ammonia, carbon dioxide, ammonium carbamate, water, urea, biuret, triuret, cyanuric acid, and combinations thereof; preferably ammonia and carbon dioxide, and / or water and carbon dioxide, and / or ammonia and urea, and / or urea and carbon dioxide, and / or ammonium carbamate; preferably, wherein the chemical substance is at least ammonia, carbon dioxide, water, urea, and biuret, and optionally ammonium carbamate.

14. The method according to any one of claims 8 to 13, wherein the urea synthesis section in step (I) is a high-pressure urea synthesis section, and wherein the process flow is contained in the high-pressure urea reactor, high-pressure stripping tower, high-pressure condenser, and / or high-pressure scrubber of the high-pressure urea synthesis section; and / or the process flow is the feed flow and / or effluent flow of the high-pressure urea reactor, high-pressure stripping tower, high-pressure condenser, and / or high-pressure scrubber of the high-pressure urea synthesis section, and / or the low-pressure section (e.g., the low-pressure recovery section).

15. The method according to any one of claims 8 to 14, wherein the qualitative determination in step (II) comprises identifying characteristic peaks of the one or more chemical substances in the NIR spectrum at a specific temperature and a specific pressure, and wherein the quantitative determination in step (III) comprises applying a chemometric method to the data of the NIR spectrum; preferably, the data includes characteristic peak area / intensity; more preferably, wherein the chemometric method includes multivariate calibration; even more preferably, the chemometric method is a partial least squares (PLS) regression method, and / or a principal component regression (PCR) method, and / or a multiple linear regression (MLR) method, or includes a partial least squares (PLS) regression method, and / or a principal component regression (PCR) method, and / or a multiple linear regression (MLR) method.

16. The method according to any one of claims 8 to 15, wherein the specific temperature is room temperature to 300°C, preferably 40°C to 280°C, more preferably 50°C to 250°C, and wherein the specific pressure is 80 bar to 350 bar, preferably 90 bar to 325 bar, more preferably 100 bar to 300 bar.

17. The method according to any one of claims 8 to 16, further comprising: (IV) Based on the quantitative determination in step (III), at least one of the following in the urea synthesis section is adjusted: the ammonia to carbon dioxide (N / C) equivalent ratio, the water to carbon dioxide (H / C) equivalent ratio, and the urea to carbon dioxide (U / C) equivalent ratio.

18. An apparatus comprising: (A) Urea synthesis section, in which ammonia and carbon dioxide react to obtain urea or biuret-containing urea, such as high biuret urea; (B) One or more near-infrared (NIR) spectral probes, said one or more NIR spectral probes being located at one or more process flows in said urea synthesis section; (C) At least one NIR spectrometer, said at least one NIR spectrometer being functionally connected to the NIR spectrometer probe to obtain one or more NIR spectra; (D) At least one processing unit of the one or more NIR spectra, the at least one processing unit being configured to obtain a quantitative determination of the one or more chemical substances.

19. The apparatus according to the preceding claims, wherein the apparatus does not have a sampling device for the one or more process flows.

20. The apparatus according to any one of claims 18 to 19, wherein the one or more NIR spectral probes and the at least one NIR spectral device are configured to cover 12000 cm⁻¹ -1 Up to 7500 cm -1 Or 11995 cm -1 Up to 7355 cm -1 The electromagnetic spectrum region.

21. The device according to any one of claims 18 to 20, further comprising: (E) An adjustment device for at least one of the ammonia to carbon dioxide (N / C) equivalent ratio, the water to carbon dioxide (H / C) equivalent ratio, and the urea to carbon dioxide (U / C) equivalent ratio in the urea synthesis section, the adjustment device being functionally connected to the processing unit such that the adjustment of the adjustment device is based on the quantitative determination; Preferably, the one or more NIR spectral probes are at least partially located within the high-pressure urea reactor, high-pressure stripping tower, high-pressure condenser, and / or high-pressure scrubber of the urea synthesis section; and / or the one or more NIR spectral probes are located at the feed stream and / or effluent stream of the high-pressure urea reactor, high-pressure stripping tower, high-pressure condenser, and / or high-pressure scrubber of the urea synthesis section, and / or the low-pressure section (e.g., the low-pressure recovery section).

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