Method for determining content of target component in gas mixture by means of raman spectroscopy

Abstract

Provided in the present invention is a method for determining the content of a target component in a gas mixture by means of Raman spectroscopy, comprising: performing Raman spectroscopy detection on a gas mixture to obtain a Raman spectrogram; selecting one characteristic peak from the Raman spectrogram as a reference peak, the component corresponding thereto being a reference component, and normalizing characteristic peaks in the Raman spectrogram relative to the reference peak, so as to obtain a relative Raman peak height of each characteristic peak; in combination with the Raman spectrogram of a pure target component, determining the peak position of the characteristic peak of each target component in the Raman spectrogram of the gas mixture; on the basis of the relative Raman peak height of the target component and a regression coefficient obtained on the basis of a training sample set of the gas mixture, determining the molar ratio or volume ratio of the target component to the reference component in the gas mixture; and, on the basis of the molar ratio or volume ratio of the target component to the reference component, determining the molar fraction or volume fraction of each target component in the gas mixture.

Description

Method for determining the content of target components in gas mixtures by Raman spectroscopy Technical Field

[0001] The present invention relates to a method for determining the content of target components in a gas mixture by using Raman spectroscopy, and in particular to a method for determining the content of each target component in an ethylene cracking gas mixture by using Raman spectroscopy. Background Art

[0002] Material analysis is crucial for production facilities producing basic organic chemical raw materials, including ethylene, propylene, and butadiene, particularly in ethylene cracking furnaces. The gaseous material (cracked gas) at the outlet of an ethylene cracking furnace primarily contains light components such as H2, CH4, C2H6, C2H4, C3H8, C3H6, and C4H8. Measuring the content of these components in the cracked gas can reveal the cracking depth and distribution of cracked products in the cracking furnace, thereby helping to optimize the cracking reaction process parameters.

[0003] Gas chromatography (GC) is one of the commonly used methods for analyzing the composition of gas mixtures. For example, for the composition analysis of cracked gas in an ethylene cracking furnace, a multidimensional gas chromatograph is mainly used. Through a multi-column and multi-valve switching system, various techniques such as cutting, backflushing, and capillary columns are adopted to detect different components in the sample gas in different paths and on different detectors (such as a hydrogen flame ionization detector (FID) to detect the hydrocarbon content in the gas mixture, and a thermal conductivity detector (TCD) to detect the H2 content and N2 content in the gas mixture), so as to obtain the analysis results of multiple components in the cracked gas, such as H2 to toluene. Its advantages are comprehensive analysis results and a large amount of information, but the interval between two injections (i.e., the time required for sample analysis and instrument preparation for re-injection) is usually around 20 minutes, and even up to 30 minutes or longer. In addition, online chromatographic detection and analysis also have the disadvantages of complex systems, multiple auxiliary equipment, and heavy on-site maintenance workload, which limits its widespread application.

[0004] Due to the increasing output of cracking furnaces and the diversity of cracking feedstocks, maximizing production efficiency requires increasingly rapid detection and analysis of specific production indicators, such as cracking depth, to enable timely adjustment of process parameters and optimization of product distribution. In recent years, near-infrared and Raman spectroscopy methods have been increasingly used for the rapid detection and analysis of cracking feedstocks and liquid products. Laser Raman spectroscopy, a molecular structure characterization technique based on the Raman scattering effect, enables rapid, non-destructive analysis of samples. Its simple structure, low maintenance costs, and ease of operation make it widely used in the oil refining, chemical, and pharmaceutical industries.

[0005] However, laser Raman spectroscopy is currently difficult to use for analyzing gas mixtures with multiple components due to issues such as low gas molecular density, small scattering cross-sections, and weak Raman spectra. This is particularly true for process gas mixtures, such as ethylene cracking gas, which are near atmospheric pressure, have weak Raman signals, a large number of components, and significant signal interference, making it difficult to obtain fast and accurate analysis results.

[0006] In summary, existing gas mixture detection and analysis methods have problems such as slow speed and / or poor result accuracy, and therefore cannot achieve rapid and accurate detection and analysis of gas mixtures, especially gas mixtures with multiple components, such as ethylene cracking gas mixtures. Summary of the Invention

[0007] In response to the technical problems in the existing methods for detecting and analyzing gas mixtures, which are slow and / or have poor result accuracy, the present invention provides a method for determining the content of a target component in a gas mixture by Raman spectroscopy. This method can achieve rapid and accurate detection and analysis of gas mixtures (such as ethylene cracking gas mixtures).

[0008] To achieve the above objectives, in a first aspect, the present invention provides a method for determining the content of a target component in a gas mixture by Raman spectroscopy, wherein the method comprises:

[0009] 1) Performing Raman spectroscopy on the gas mixture to obtain a Raman spectrum;

[0010] 2) selecting a characteristic peak from the Raman spectrum as a reference peak, and the component corresponding to the characteristic peak as a reference component, and normalizing the characteristic peaks of each target component in the Raman spectrum relative to the reference peak to obtain the relative Raman peak height of each characteristic peak;

[0011] 3) determining the peak position of the characteristic peak of each target component in the Raman spectrum of the gas mixture in combination with the Raman spectrum of the pure target component;

[0012] 4) determining a molar ratio or volume ratio of the target component to the reference component in the gas mixture based on the relative Raman peak height of the characteristic peak at the specific peak position of the target component obtained in steps 2) and 3) and one or more, preferably one or two, regression coefficients obtained from a training sample set of the gas mixture; and

[0013] 5) Determining the mole fraction or volume fraction of each target component in the gas mixture based on the mole ratio or volume ratio of the target component to the reference component obtained in step 4).

[0014] In a second aspect, the present invention provides a Raman spectroscopy analysis device, which includes a processor and a memory, wherein the memory stores at least one computer program, and when the at least one computer program is executed by the processor, the processor executes the method for determining the content of a target component in a gas mixture by Raman spectroscopy according to the first aspect.

[0015] In a third aspect, the present invention provides a computer-readable storage medium storing at least one program instruction, which, when executed by a processor, causes the computer to execute the method for determining the content of a target component in a gas mixture by Raman spectroscopy according to the first aspect.

[0016] In a fourth aspect, the present invention further provides a computer program product comprising at least one program instruction, which, when executed by a processor, causes the processor to execute the method for determining the content of a target component in a gas mixture by Raman spectroscopy according to the first aspect.

[0017] In a fifth aspect, the present invention provides an online detection and analysis system for a gas mixture based on Raman spectroscopy, comprising a sampling unit, a Raman spectroscopy detection unit, and the Raman spectroscopy analysis device according to the second aspect;

[0018] The sampling unit is respectively connected to the outlet pipeline of the reactor and to a Raman spectrum detection unit, wherein the Raman spectrum detection unit is used to detect the gas mixture collected by the sampling unit to obtain a Raman spectrum of the gas mixture; the Raman spectrum detection unit is also connected to a Raman spectrum analysis device, wherein the Raman spectrum analysis device is used to analyze the Raman spectrum of the gas mixture to obtain the mole fraction or volume fraction of each target component in the gas mixture.

[0019] The method according to the present invention can achieve at least the following technical effects:

[0020] (1) The Raman spectroscopic analysis method and online detection system for the content of each component in a gas mixture according to the present invention can achieve rapid and accurate quantitative analysis of process gas mixtures (such as ethylene cracking gas mixtures);

[0021] (2) The Raman spectroscopy analysis method for the content of each component in a gas mixture according to the present invention determines the content of each component based on the relative Raman peak height of each component. The model structure is simple and has strong adaptability, and can be applied to the online real-time analysis of the composition of cracked gas obtained from different reactions. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] FIG1 is a flow chart of an embodiment of a method for determining the content of a target component in a gas mixture by Raman spectroscopy according to the present invention;

[0023] FIG2 is an original Raman spectrum of an untreated ethylene cracked gas mixture detected by one embodiment of the method for determining the content of a target component in a gas mixture by Raman spectroscopy according to the present invention;

[0024] FIG3 is a Raman spectrum obtained after target background subtraction and baseline correction of FIG2 ;

[0025] FIG4 is a Raman spectrum obtained after target background subtraction and baseline correction and normalization processing of FIG3;

[0026] FIG5 is a schematic structural diagram of an embodiment of a Raman spectroscopic analysis device according to the present invention;

[0027] FIG6 is a hardware architecture diagram of an embodiment of an online detection and analysis system for ethylene cracking gas mixture based on Raman spectroscopy according to the present invention;

[0028] FIG7 is a working principle diagram of an embodiment of an online detection and analysis system for ethylene cracking gas mixture based on Raman spectroscopy according to the present invention;

[0029] Figure 8 is a comparison of the volume fraction values ​​of four target components (H2, methane, ethylene, propylene) determined by an embodiment of the method for determining the content of target components in a gas mixture by Raman spectroscopy according to the present invention and the volume fraction values ​​of the four target components (H2, methane, ethylene, propylene) determined by gas chromatography. DETAILED DESCRIPTION

[0030] The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the technical solutions of the present invention, and do not play a limiting role.

[0031] It should be noted that, in the absence of conflict, the features of the various technical solutions of the present invention can be combined with each other.

[0032] It should also be noted that, in the specification of this application, unless otherwise expressly specified or limited, the terms "installation" and "connection" should be understood in a broad sense. For example, they can refer to fixed installation or connection or detachable installation or connection; direct installation or connection or indirect installation or connection; and wired connection or wireless connection. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0033] Any specific numerical value disclosed herein (including the endpoints of a numerical range) is not limited to the exact value of the numerical value, but should be understood to also include values ​​close to the exact value, such as all possible values ​​within ±5% of the exact value. Moreover, for a disclosed numerical range, any combination of the endpoints of the range, between the endpoints and the specific points in the range, and between the specific points can be used to generate one or more new numerical ranges, and these new numerical ranges should also be considered to be specifically disclosed herein.

[0034] Unless otherwise specified, the terms used herein have the same meaning as commonly understood by those skilled in the art. If a term is defined herein and its definition is different from the commonly understood meaning in the art, the definition herein shall prevail.

[0035] The expressions "comprising" or "including" herein should be interpreted as including all the specifically mentioned features as well as optional, additional, unspecified features. As used herein, the use of the term "comprising" also discloses solutions in which no further features than the specifically mentioned features are present, for example, the expressions "consisting essentially of" and "consisting of.

[0036] In the context of this application, the terms "one or more" and "at least one" have the same meaning and can be used interchangeably; the terms "one or several" and "at least one" have the same meaning and can be used interchangeably.

[0037] In a first aspect, as shown in FIG1 , the present invention provides a method for determining the content of a target component in a gas mixture by Raman spectroscopy, wherein the method comprises:

[0038] 1) Performing Raman spectroscopy on the gas mixture to obtain a Raman spectrum;

[0039] 2) selecting a characteristic peak from the Raman spectrum as a reference peak, and the component corresponding to the characteristic peak as a reference component, and normalizing the characteristic peaks of each target component in the Raman spectrum relative to the reference peak to obtain the relative Raman peak height of each characteristic peak;

[0040] 3) determining the peak position of the characteristic peak of each target component in the Raman spectrum of the gas mixture in combination with the Raman spectrum of the pure target component;

[0041] 4) determining the molar ratio or volume ratio of the target component to the reference component in the gas mixture based on the relative Raman peak height of the characteristic peak at the specific peak position of the target component obtained in steps 2) and 3) and one or more, preferably one or two, regression coefficients obtained from a training sample set of the gas mixture; and

[0042] 5) Determining the mole fraction or volume fraction of each target component in the gas mixture based on the mole ratio or volume ratio of the target component to the reference component obtained in step 4).

[0043] In the context of the present application, the “target component” includes the reference component and other components other than the reference component whose contents in the gas mixture need to be determined.

[0044] Preferably, when the target component includes more than one characteristic peak in the Raman spectrum of the gas mixture, one characteristic peak is selected and its relative Raman peak height is used to determine the molar ratio or volume ratio of the target component to the reference component in step 4).

[0045] In the context of this application, the term "gas mixture" refers to a product mixture containing more than one gas produced by a reaction, preferably a cracking reaction, in particular a hydrocarbon steam cracking reaction. For example, the raw materials for preparing the gas mixture can be products obtained by processing crude oil, such as ethane, propane, tops, raffinate, naphtha, kerosene, diesel and / or hydrotreated tail oil. The term "steam cracking" refers to a process in which petroleum hydrocarbons or petroleum fractions (such as naphtha) undergo molecular fragmentation and / or dehydrogenation reactions at high temperatures (e.g., above 750°C) in the presence of water vapor, usually without the use of a catalyst.

[0046] The term "cleavage reaction" refers to a chemical transformation process in which a higher molecular weight compound is converted into one or more lower molecular weight compounds using thermal energy. According to the present invention, the cleavage reaction may or may not be catalyzed. Preferably, the cleavage reaction is an uncatalyzed cleavage reaction carried out at a temperature of 700-1000°C.

[0047] According to the present invention, the "gas mixture" can be an online detection gas mixture and / or a process gas mixture collected at the outlet of a continuous reactor. Existing Raman spectroscopy analysis methods for the component content of a gas mixture usually require pressurizing the gas to be detected to enhance the signal in order to obtain accurate analysis results, and pressurization requires additional equipment and operations and may cause the gas to be detected to be liquefied, resulting in inaccurate analysis results. The method for analyzing the component content of a gas mixture according to the present invention can be used to analyze the Raman spectra obtained by detecting gases at normal temperature and pressure, and is therefore more suitable for online detection of gas mixtures and / or process gas mixtures. The "continuous reactor" refers to a process in which reactants enter the reactor in a continuous manner and react under stable reaction conditions maintained inside the reactor. Typically, reactants enter and leave the reactor at a fixed rate, and the material concentration does not change with time.

[0048] Preferably, the gas mixture is a process gas mixture and / or an online detection gas mixture. Preferably, the "process gas mixture and / or online detection gas mixture" is not a finished gas, but rather a product gas mixture collected at the outlet of a continuous reactor, preferably a continuous cracking reactor outlet, in particular a steam cracking reactor outlet.

[0049] The "Raman spectrum" can be a Raman spectrum measured by any type of spectrometer commonly used in the field of chemistry and chemical engineering. For example, the Raman spectrum can be obtained using a spectrometer (Ocean Optics QE Pro).

[0050] The "reference peak" refers to a characteristic peak in a Raman spectrum whose relative Raman intensity is 1, obtained through normalization. Accordingly, the "normalization process" refers to the process of setting the relative Raman intensity of the reference peak to 1 and adjusting the relative intensities of other characteristic peaks in the Raman spectrum accordingly.

[0051] Because Raman spectroscopy produces fingerprint peaks, each component in a mixture may produce multiple characteristic peaks with varying intensities and positions. This can complicate determining the content of each component in the mixture. Therefore, accurately selecting a reference peak is crucial and can effectively improve the accuracy of analytical results for the content of each component in the mixture.

[0052] The "Raman spectrum of a pure target component" refers to the Raman spectrum obtained by separately measuring each pure target component and an optional balance gas. Preferably, an inert gas, such as N2, is used as the balance gas during the test. In actual analysis, by separately measuring the Raman spectrum of each pure target component, the characteristic peak position of each target component in the Raman spectrum of the gas mixture can be obtained. These characteristic peaks are Raman scattering peaks unique to each substance, corresponding to specific vibrational modes of the molecule.

[0053] Optionally, before selecting characteristic peaks of the target component based on the Raman spectrum of the pure target component and using them to calculate the molar ratio or volume ratio relative to the reference component, an optimization step 3') of the relative Raman peak height of the characteristic peak is included between steps 3) and 4).

[0054] Specifically, for step 3'), in order to overcome or at least reduce the influence of coexisting substances on the relative Raman peak height of the target component, the relative Raman peak height of one or more characteristic peaks obtained by normalization in step 2) can be subtracted from the 50 cm radius around the respective peak position. -1 Within, preferably 30cm -1 The relative Raman peak height of the reference peak at the reference point within is obtained to obtain the optimized relative Raman peak height of the characteristic peak.

[0055] For example, the gas mixture contains 3-20 target components, a characteristic peak is selected for each target component, and its molar ratio or volume ratio relative to the reference component is calculated using its relative Raman peak height. Step 3' of optimizing the relative Raman peak heights as described above can be performed for some or all of the target components, e.g., 1-3, e.g., 1, 2, or 3 target components. For example, the gas mixture contains 5-15 target components, a characteristic peak is selected for each target component, and its molar ratio or volume ratio relative to the reference component is calculated using its relative Raman peak height. Step 3' of optimizing the relative Raman peak heights as described above can be performed for some or all of the target components, e.g., 1-5 or 2-4, e.g., 1, 2, 3, 4, or 5 target components. For example, the gas mixture contains 7-20 or 7-15 target components. For each target component, a characteristic peak is selected and its molar ratio or volume ratio relative to the reference component is calculated using its relative Raman peak height. Step 3') of optimizing the relative Raman peak height as described above can be performed for some or all of the target components, for example, 1-7, 2-6, or 3-5, for example, 1, 2, 3, 4, 5, 6, or 7 target components.

[0056] For example, if the target component A is selected at 1200 cm -1 The molar ratio or volume ratio of the reference component is calculated by the characteristic peak at 1150 cm -1 Up to 1250cm -1 A reference point within the range (e.g. 1220cm -1 For optimization, the original relative Raman peak height a of the characteristic peak can be subtracted from the relative Raman peak height b of the reference point to obtain the optimized relative Raman peak height a'.

[0057] According to the present invention, the "normal temperature" refers to 10°C to 40°C, preferably 15°C to 35°C; the "normal pressure" refers to an absolute pressure of 0.1 MPa-0.15 MPa.

[0058] Regarding step 4), the one or more regression coefficients can be determined according to any commonly used chemometric method or statistical regression model. For example, the regression coefficients can be determined using the least squares method, such as the least squares method in Matlab.

[0059] Preferably, the training sample set of the gas mixture includes a Raman spectrum of the gas mixture and a molar ratio or a volume ratio of a target component to a reference component in the gas mixture.

[0060] Preferably, the molar ratio or volume ratio of the target component to the reference component in the gas mixture of the training sample set is obtained by measuring the content of each target component in the gas mixture by gas chromatography.

[0061] When the gas mixture is a process gas mixture and / or an online detection gas mixture, the regression coefficient is preferably determined by the following steps:

[0062] i) collecting gas mixture samples at the outlet of the continuous reactor at two or more time points;

[0063] ii) performing Raman spectroscopy and gas chromatography on the gas mixture samples collected at the same time point, respectively, wherein a relative Raman peak height of the target component relative to the reference component is obtained from the measured Raman spectrum, and a molar ratio or volume ratio of the target component to the reference component is obtained by gas chromatography, wherein the relative Raman peak height and the molar ratio or volume ratio corresponding to each group obtained at each time point form a training sample set; and

[0064] iii) using the training sample set in combination with a statistical regression model to establish the relationship between the relative Raman peak height and the molar ratio or volume ratio described in step ii), thereby obtaining the regression coefficient.

[0065] According to the present invention, the detection time of a gas mixture in a gas chromatograph can be determined based on the number and type of target components in the gas mixture and the peak emission times of these target components when detected by the gas chromatograph. For example, if the target component emits a peak early when detected by the gas chromatograph, the gas chromatograph detection time can be appropriately shortened. In other words, it is sufficient to wait until all target components whose content is to be determined have emitted a peak, without having to wait for all components to emit a peak.

[0066] Preferably, the gas mixture samples are collected at 5 or more time points, preferably 10 or more time points, more preferably 15 or more time points, and even more preferably 20 or more time points. For example, the gas mixture samples are collected at 5 to 50 time points, preferably 10 to 40 time points, more preferably 15 to 35 time points, and even more preferably 20 to 30 time points.

[0067] In some embodiments, two gas mixture samples are collected simultaneously and subjected to Raman spectroscopy and gas chromatography detection, respectively. In some embodiments, the collected gas mixture samples are first subjected to Raman spectroscopy detection and then to gas chromatography detection.

[0068] Preferably, the relative Raman peak height of the target component in step ii) is obtained from the measured Raman spectrum and according to the method described in the aforementioned steps 2) and 3). Specifically, a characteristic peak is selected from the Raman spectrum as a reference peak. Preferably, a characteristic peak with the same peak position as in step 2) is selected as the reference peak, and its corresponding component is used as the reference component. The characteristic peaks of each target component in the Raman spectrum are normalized relative to the reference peak to obtain the relative Raman peak height of each characteristic peak. When the target component includes more than one characteristic peak in the Raman spectrum of the gas mixture, a characteristic peak is selected (preferably a characteristic peak with the same peak position as in the aforementioned step 4)) and its relative Raman peak height is used to determine the regression coefficient.

[0069] For step ii), in order to obtain the molar ratio or volume ratio of the target component to the reference component in the gas mixture of the training sample set, for example, the molar fraction or volume fraction of each target component in the gas mixture can be measured by gas chromatography, and then the molar ratio or volume ratio of the target component to the reference component in the gas mixture can be calculated.

[0070] Since the regression coefficients used in the method of determining the content of each component in a gas mixture of the present invention are obtained based on a training sample set of the gas mixture (rather than one or two components therein) and the molar ratio or volume ratio in the training sample set is obtained using gas chromatography, the influence of other components in the gas mixture other than the target component on the Raman spectrum is fully considered. Therefore, with the help of the regression coefficients of the present invention, the content of each target component in the gas mixture can be obtained more accurately.

[0071] Once the training sample set is used to obtain the regression coefficients used in the method for determining the content of each component in a gas mixture of the present invention, the regression coefficients can be subsequently repeatedly used to quickly and accurately determine the molar ratio or volume ratio of the target component to the reference component in similar gas mixtures, thereby quickly and accurately obtaining the mole fraction or volume fraction of each target component in the gas mixture. For large-scale production processes (e.g., with an annual output of 100,000 tons or more) that maintain substantially identical reaction raw materials and similar reaction types and conditions over a long period of time (e.g., a year or longer), quickly and accurately adjusting the process parameters for online detection of the content of each major component in the gas mixture can effectively improve the yield of the target component (e.g., ethylene).

[0072] Preferably, the method according to the present invention comprises, between steps 1) and 2), a step 1') of performing background subtraction and baseline correction on the original Raman spectrum of the gas mixture.

[0073] Background subtraction refers to the removal of the effects of background factors other than the feed components on the Raman spectrum, thereby improving the accuracy and reliability of the Raman spectral data. Baseline correction refers to the process of adjusting the baseline of the feed component peak to zero. Background subtraction and baseline correction can be performed using any conventional methods and standards available in instrument analysis software.

[0074] FIG2 shows an original Raman spectrum obtained by detecting a gas mixture using a Raman spectrometer (Ocean Optics QE Pro). The original Raman spectrum in FIG3 is obtained after background subtraction and baseline correction, wherein P0, P1, and P2 are characteristic peaks of N2, ethylene, and H2, respectively. FIG4 is obtained after normalization with the P1 peak as the reference peak. It can be seen that by introducing background subtraction and baseline correction technology into the method according to the present invention, and normalizing each characteristic peak in the Raman spectrum with a characteristic peak of the reference component as the reference, the repeatability of the Raman spectrum can be greatly improved, and the influence of the pressure fluctuation of the gas mixture and the change of the spectral detection conditions (such as laser power) on the Raman spectrum can be significantly reduced.

[0075] According to the present invention, the gas mixture contains organic gases and / or inorganic gases.

[0076] Preferably, the gas mixture comprises 2 or more, preferably 3 or more, more preferably 5 or more, and even more preferably 7 or more organic gases. For example, the gas mixture comprises 2 to 20, or 3 to 20, or 5 to 15, or 7 to 10 organic gases.

[0077] More preferably, the organic gas is a gas composed of carbon and hydrogen elements and optionally having an unsaturated bond, wherein the organic gas preferably has one to seven carbon atoms, more preferably one to four carbon atoms, and even more preferably one to three carbon atoms.

[0078] Preferably, the gas mixture contains at least one organic gas composed of carbon and hydrogen elements and having unsaturated bonds.

[0079] With the aid of the method of the present invention for determining the content of a target component in a gas mixture by Raman spectroscopy, a process gas mixture containing a plurality of (e.g., 5 or more, or even 7 or more) organic gases at normal temperature and pressure can be accurately obtained and / or the content of each component in the gas mixture can be detected online.

[0080] Preferably, the gas mixture contains n target components, wherein n is an integer greater than or equal to 2, preferably greater than or equal to 3, more preferably greater than or equal to 5, preferably less than or equal to 50, more preferably less than or equal to 30, and still more preferably less than or equal to 20, and their mole fraction or volume fraction is c j (j=1,...,n), their Raman peak height is P j (j=1,...,n). According to the principle of Raman spectroscopy, for different components in the same mixture, the Raman peak height ratio of the jth component to the reference component should be proportional to their mole fraction or volume fraction, and has nothing to do with the detection conditions and the feed gas pressure. The following formula can be obtained:

[0081] In formula (1), P j is the Raman peak height of the jth component in the gas mixture, P1 is the Raman peak height of the reference component in the gas mixture, K j is the Raman intensity factor of the jth component in the gas mixture, K1 is the Raman intensity factor of the reference component in the gas mixture (it is usually assumed that the Raman intensity factor of the reference component is 1), c j is the mole fraction or volume fraction of the jth component in the gas mixture, and c1 is the mole fraction or volume fraction of the reference component in the gas mixture, where j=1 corresponds to the reference component.

[0082] For the normalized spectrum of any gas mixture, let the characteristic peak height (i.e. relative Raman peak height) P1 of the reference component be 1, and the formula (1) can be obtained:

[0083] Where z j is the molar ratio or volume ratio of the jth component of the gas mixture to the reference component, c j is the mole fraction or volume fraction of the jth component in the gas mixture, c1 is the mole fraction or volume fraction of the reference component in the gas mixture, P j is the relative Raman peak height of the jth component in the gas mixture, k j is the regression coefficient of the jth component in the gas mixture, where j = 1 corresponds to the reference component.

[0084] Formula (2) is more suitable for the case where the gas mixture has fewer components (for example, it is composed of only 5 or fewer gases and contains 2 or fewer organic gases, and the characteristics of each component peak are more obvious.

[0085] In order to improve the calculation accuracy of the analysis model, formula (2) can be further expanded to: j =k j0 +k j1 P j,(j=1,…,n) (3)

[0086] Where z j is the molar ratio or volume ratio of the jth component in the gas mixture to the reference component, P j is the relative Raman peak height of the jth component in the gas mixture, k j0 is the first regression coefficient of the jth component in the gas mixture, k j1 is the second regression coefficient of the jth component in the gas mixture, where j = 1 corresponds to the reference component.

[0087] The regression coefficient k in formulas (2) and (3) is j 、k j0 and k j1 Preferably, it is determined by steps i), ii) and iii) as described above.

[0088] Preferably, for any gas mixture of unknown composition, which contains n target components, wherein n is an integer greater than or equal to 2, preferably greater than or equal to 3, more preferably greater than or equal to 5, preferably less than or equal to 50, more preferably less than or equal to 30, and even more preferably less than or equal to 20, the sum of the mole fractions or volume fractions of the n target components is 1, that is: c1+c2+…+c n =1 (4)

[0089] Where z1=1, so formula (4) can be further expanded to: c1(z1+z2+…+z n )=1 (5)

[0090] Therefore, the mole fraction or volume fraction of each target component in the gas mixture is:

[0091] Where c j is the mole fraction or volume fraction of the jth component in the gas mixture, z j is the molar ratio or volume ratio of the jth component in the gas mixture to the reference component, z i is the molar ratio or volume ratio of the i-th component in the gas mixture to the reference component, where j=1 corresponds to the reference component.

[0092] By means of the above-mentioned regression coefficients of the present invention and the above-mentioned formula (2) or (3), in particular formula (3), and formula (6), for determining the molar ratio or volume ratio of the target components in the gas mixture, the molar fraction or volume fraction of each target component in the gas mixture, in particular, the molar fraction or volume fraction of each target component in the gas mixture or process gas mixture can be obtained simply, quickly and accurately.

[0093] Preferably, the gas mixture is an ethylene cracking gas mixture containing ethylene obtained by a cracking reaction, preferably a steam cracking reaction. In addition, the gas mixture can also be a cracking gas mixture containing other hydrocarbons such as propylene obtained by a cracking reaction.

[0094] The terms "ethylene cracking gas" or "ethylene cracking gas mixture" are used interchangeably in the context of this application and refer to a mixture containing ethylene obtained by cracking a certain raw material. Such a mixture is preferably a process gas mixture and / or an online detection gas mixture.

[0095] Preferably, the ethylene content in the target component of the "ethylene cracking gas" or "ethylene cracking gas mixture" is 15 wt % or more, preferably 20 wt % or more, more preferably 30 wt % or more, for example 15 wt % to 70 wt %, or 20 wt % to 60 wt %, or 30 wt % to 50 wt %, relative to the total weight of the target component of the ethylene cracking gas or the ethylene cracking gas mixture.

[0096] Preferably, the ethylene cracking gas mixture comprises hydrogen, methane, ethane, ethylene, acetylene, propane, propylene, propyne and optionally butene and / or butadiene.

[0097] Preferably, the reference component of the ethylene cracking gas mixture is ethylene.

[0098] Preferably, the -1 The characteristic peak of ethylene nearby is used as the reference peak.

[0099] According to the context of the present invention, the expression "1345cm -1 "Nearby" refers to 1345cm -1 ±10cm -1 , preferably 1345cm -1 ±5cm -1 , more preferably 1345cm -1 ±2cm -1 .

[0100] By selecting the -1 The characteristic peak of ethylene nearby is used as a reference peak, which can effectively improve the accuracy of the analysis results of the content of each component in the ethylene cracking gas mixture.

[0101] When the gas mixture is an ethylene cracking gas mixture used as an online detection gas or a process gas, and hydrogen, methane, ethane, ethylene, acetylene, propane, propylene and propyne account for more than 80 volume % of the target component content of the gas mixture, in order to obtain the regression coefficient of the present invention, the analysis period for detecting the target component of the gas mixture by a gas chromatograph can be about 15 minutes (TCD and FID detectors can be used), wherein the "analysis period" generally includes the programmed heating time, the peak separation time and the programmed cooling time.

[0102] Optionally, prior to Raman spectroscopy detection of the ethylene cracked gas mixture, direct Raman signal enhancement measures can be implemented from a hardware perspective, including increasing laser power, widening the collection angle of Raman scattered light, reducing optical signal transmission loss, improving spectrometer detection sensitivity while reducing detection noise (e.g., by using CCD cooling), and appropriately increasing the spectrometer integration time (e.g., setting the spectrometer integration time to 30-90 seconds). These measures can further enhance the online Raman spectroscopy detection signal of the ethylene cracked gas mixture.

[0103] Preferably, the Raman spectroscopy detection is performed under the following conditions: a laser power of greater than or equal to 1 W, preferably 1 W to 3 W; and / or a spectral linewidth of less than or equal to 0.2 nm, preferably less than or equal to 0.15 nm; and / or a spectral integration time of 30 to 90 seconds, preferably 50 to 70 seconds, and more preferably 45 to 60 seconds. These detection conditions can address the issue of low pressure in the ethylene cracking gas mixture affecting detection accuracy.

[0104] In addition, the Raman spectrum detection can be performed in the range of 300 to 3100 cm -1 spectral range and / or no greater than 10cm -1 , preferably no more than 8cm -1 , more preferably no more than 6cm -1 The measurement is carried out under the condition of spectral resolution, thereby ensuring that the Raman spectrometer is suitable for the detection of process gas mixtures and / or online detection gas mixtures, and ensuring the stability of the Raman spectrometer under online working conditions. At the same time, the spectral range can ensure that the Raman characteristic spectrum region of the target component in the ethylene cracking gas mixture is covered, and the spectral resolution can ensure the measurement accuracy of the spectrum.

[0105] Raman spectroscopy can be detected using a charge-coupled device (CCD) detector. To reduce detector noise and improve the signal-to-noise ratio, a high-sensitivity Raman spectrometer can be used. The detector in such a Raman spectrometer can be a back-illuminated CCD detector array with a semiconductor cooler (also known as a thermoelectric cooler, abbreviated TEC), where the cooling temperature is typically below or equal to -15°C.

[0106] Based on the above hardware selection and parameter design, the Raman spectrum detection signal is improved and the noise level is reduced, while making the project implementation and application relatively convenient.

[0107] The present method, when used to analyze the content of an ethylene cracking gas mixture, can determine the mole fraction or volume fraction of each target component in the gas mixture in approximately one minute or less. Compared to gas chromatography, the Raman detection method of the present invention significantly shortens detection and analysis time and achieves comparable accuracy to gas chromatography in determining the mole fraction or volume fraction of each target component.

[0108] In addition, the implementation environment of the method for performing Raman detection and analysis on a gas mixture according to the present invention may include a terminal and a server, and the method may be executed on the terminal or the server. The terminal and the server may be communicatively connected to realize interactive transmission of information.

[0109] The terminal can be any electronic product that interacts with the user through one or more methods such as keyboard, touchpad, touch screen, voice interaction, etc., such as PC (Personal Computer), PPC (Pocket Personal Computer), tablet computer, etc.

[0110] A server can be a single server or a server cluster consisting of multiple servers. It can also be a cloud server that provides basic cloud computing services such as cloud services, cloud databases, cloud computing, cloud functions, cloud storage, network services, cloud communications, middleware services, domain name services, security services, CDN (Content Delivery Network), as well as big data and artificial intelligence platforms.

[0111] In a second aspect, the present invention further provides a Raman spectroscopy analysis device, as shown in Figure 5, the Raman spectroscopy analysis device may include a processor 201 and a memory 202, wherein the memory stores at least one computer program, and when the at least one computer program is executed by the processor, the processor executes the method for determining the content of a target component in a gas mixture by Raman spectroscopy according to the first aspect.

[0112] In addition, the Raman spectroscopy analysis device may also have components for realizing various functions of the device, including a wired or wireless network interface, a keyboard, and an input and output interface, so as to perform input and output.

[0113] In a third aspect, the present invention further provides a computer-readable storage medium storing at least one program instruction, which, when executed by a processor, causes the processor to execute the method for determining the content of a target component in a gas mixture by Raman spectroscopy according to the first aspect.

[0114] In a fourth aspect, the present invention further provides a computer program product comprising at least one program instruction, which, when executed by a processor, causes the processor to execute the method for determining the content of a target component in a gas mixture by Raman spectroscopy according to the first aspect.

[0115] A computer program product including computer executable instructions can be stored in the computer readable storage medium. All or part of the steps in the method according to the first aspect of the present invention can be defined by the computer executable instructions included in the computer program product stored in the computer readable storage medium, and executed by a processor that executes the computer executable instructions to implement the method for determining the content of the target component in the gas mixture by Raman spectroscopy according to the first aspect. The computer readable storage medium includes a tangible non-transitory machine-readable storage medium and may also include a high-speed random access memory, such as a dynamic random access memory (DRAM), a static random access memory (SRAM), a double data rate synchronous dynamic random access memory (DDR RAM) or other random access solid-state memory devices, and may include a non-volatile memory, such as one or more magnetic disk storage devices (such as internal hard disks and removable disks), magneto-optical disk storage devices, optical disk storage devices, flash memory devices, semiconductor memory devices (such as erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM)), compact disk read-only memory (CD-ROM), digital versatile disk read-only memory (DVD-ROM) disk or other non-volatile solid-state storage devices.

[0116] In a fifth aspect, the present invention provides an online detection and analysis system for a gas mixture based on Raman spectroscopy, comprising a sampling unit, a Raman spectroscopy detection unit, and the Raman spectroscopy analysis device according to the second aspect;

[0117] The sampling unit is respectively connected to the outlet pipeline of the reactor and to a Raman spectrum detection unit, wherein the Raman spectrum detection unit is used to detect the gas mixture collected by the sampling unit to obtain a Raman spectrum of the gas mixture; the Raman spectrum detection unit is also connected to a Raman spectrum analysis device, wherein the Raman spectrum analysis device is used to analyze the Raman spectrum of the gas mixture to obtain the mole fraction or volume fraction of each target component in the gas mixture.

[0118] In some embodiments, the sampling unit is provided separately from the Raman spectrum detection unit. In this case, when the sampling unit includes a Raman probe, the Raman probe is provided separately from the Raman spectrum detection unit. In some embodiments, at least a portion of the sampling unit and the Raman spectrum detection unit are integrated into a Raman spectrometer. In this case, when the sampling unit includes a Raman probe, the Raman probe can be integrated into the Raman spectrometer with the Raman spectrum detection unit.

[0119] In one embodiment, as shown in Figure 6, one end of the Raman spectrometer is connected to an online sampling device via a dedicated Raman optical cable to facilitate Raman spectral detection of the target. The other end of the Raman spectrometer is connected to a remote monitoring PC via a communication optical cable to obtain Raman analysis results for each target component in the gas mixture.

[0120] In one embodiment, an online sampling device (such as the 1# field sampling unit in Figure 6) is directly installed on the reaction device, including a gas sampler and a gas Raman probe. When the material flow of the reaction device is small and it is an intermittent reaction device, after its own rapid cooling and three-stage water-cooled separation and recovery system, it can already meet the subsequent online analysis needs. Therefore, the online gas sampler of the reaction device is located after the three-stage water cooling, and the material temperature is close to room temperature. The sampler allows the gas mixture to pass through the filtration reflux section and the cooling and dehydration section, leaving solid particles, heavy components and water in the process pipeline, taking out the light components and sending them evenly to the Raman probe at a certain flow rate. The purified gas mixture is mainly composed of H2 and C1-C4 hydrocarbons. The Raman probe connected to the sampler is connected to the Raman spectrometer using a dedicated Raman optical cable.

[0121] In one embodiment, the working principle of the online Raman spectroscopy detection and analysis device is shown in Figure 7. The monochromatic excitation light emitted by the laser is irradiated to the target sample in the sampling tube (also called the flow cell) through a dedicated optical fiber and a Raman probe. The excited Raman scattered light is collected by the Raman probe and transmitted to the spectrometer by a dedicated optical fiber for spectrometry and analog-to-digital conversion. Finally, the Raman spectral data is transmitted to the computer for preprocessing and analysis model calculation to obtain the corresponding component content or other indicators of the target sample.

[0122] The Raman spectrometer can adopt a positive pressure explosion-proof form. The key components of the online detection and analysis system include: a laser (such as a 532nm laser), a Raman spectrometer, a programmable logic controller and an embedded PC. The embedded PC can be configured with control software for various optical components, Raman spectrum preprocessing software, and gas mixture component quantitative analysis software.

[0123] This application may include the following technical solutions:

[0124] Item 1: A Raman analysis method for mixed gas content, characterized in that the analysis method comprises:

[0125] Splitting the mixed gas into n key components, and selecting one component from the n key components as a reference component;

[0126] Performing spectral signal processing on the original Raman spectrum of the mixed gas to obtain the normalized spectrum of the mixed gas;

[0127] Based on the normalized spectrum of the gas mixture, the relative Raman peak heights of n key components are determined;

[0128] Determine the molar ratio of the n-1 key components relative to the reference component based on the relative Raman peak heights and regression coefficients of the n-1 key components;

[0129] Based on the molar ratio of the n-1 key components relative to the reference component, the mole fractions of the n key components are determined respectively.

[0130] Item 2. The Raman analysis method for the mixed gas content according to Item 1, characterized in that the spectral signal processing is performed on the original Raman spectrum of the mixed gas to obtain a normalized spectrum of the mixed gas, comprising:

[0131] Perform background subtraction and baseline correction on the original Raman spectrum of the mixed gas to obtain the corrected Raman spectrum;

[0132] The independent characteristic peak of the reference component is used as the spectrum normalization benchmark peak to normalize the calibrated Raman spectrum and obtain the normalized spectrum of the mixed gas.

[0133] Item 3. The Raman analysis method for the mixed gas content according to Item 1, characterized in that the determination of the relative Raman peak heights of n key components based on the normalized spectrum of the mixed gas comprises:

[0134] Combined with the Raman spectrum of pure component sample gas, the relatively independent characteristic peaks of n key components of the mixed gas are determined;

[0135] According to the relatively independent characteristic spectral peaks of the n key components of the mixed gas, the relative Raman peak heights of the n key components of the mixed gas are determined in the normalized spectrum of the mixed gas.

[0136] Item 4. The Raman analysis method for the mixed gas content according to Item 1, wherein the molar ratio of the n-1 key components to the reference component is calculated by the following formula: j (t) = k j0 +k j1 P j (t),(j=2,…,n)

[0137] Among them, zj (t) is the molar ratio of the jth component of the mixed gas relative to the reference component, P j (t) is the relative Raman peak height of the jth component in the mixed gas, k j0 is the first regression coefficient of the jth component of the mixture, k j1 is the second regression coefficient of the jth component of the mixture.

[0138] Item 5. The Raman analysis method for the mixed gas content according to Item 4, characterized in that the analysis method further comprises:

[0139] Determine the first and second regression coefficients of n-1 key components of the mixed gas based on the training sample set of the mixed gas;

[0140] The training sample set of the mixed gas includes: a normalized spectrum of the mixed gas and a molar ratio or a volume concentration ratio of n-1 key components of the mixed gas relative to a reference component.

[0141] Item 6. The Raman analysis method for the mixed gas content according to Item 5, characterized in that determining the first and second regression coefficients of n-1 key components of the mixed gas based on a training sample set of the mixed gas comprises:

[0142] Determine the molar ratios of n-1 key components of the mixed gas relative to the reference components based on the training sample set of the mixed gas;

[0143] Determine the relative Raman peak heights of the n-1 key components based on the normalized spectrum of the mixed gas and the characteristic peak positions of the n-1 key components;

[0144] According to the molar ratio of the n-1 key components to the reference component and the relative Raman peak height of the n-1 key components, the first and second regression coefficients of the n-1 key components of the mixed gas are determined respectively in combination with the statistical regression model.

[0145] Item 7. The Raman analysis method for the mixed gas content according to Item 1, characterized in that the mole fractions of the n components are calculated using the following formula: c1+c2+…+c n =1;

[0146] Among them, c j is the mole fraction of the jth component in the mixed gas, z j is the molar ratio of the jth component in the mixed gas to the reference component, j = 1, 2, ... n.

[0147] Item 8: An online detection method for ethylene cracking gas based on Raman spectroscopy, characterized in that the detection method comprises:

[0148] Using a Raman spectrometer to detect ethylene cracking gas and obtain the original Raman spectrum of the ethylene cracking gas;

[0149] Determine the mole fraction of each key component of the ethylene cracking gas using the Raman analysis method for the mixed gas content according to any one of claims 1 to 7 based on the original Raman spectrum of the ethylene cracking gas;

[0150] Among them, the key components of ethylene cracking gas include: hydrogen, methane, ethane, ethylene, acetylene, propane, propylene, propyne and other composite components. Other composite components are C4 olefins or butadiene. The reference component of ethylene cracking gas is ethylene.

[0151] Item 9: The online detection method for ethylene cracking gas based on Raman spectroscopy according to Item 8, characterized in that the detection method further comprises: -1 The nearby ethylene independent Raman peak was used as the reference peak for spectral normalization.

[0152] Item 10. The online detection method for ethylene cracking gas based on Raman spectroscopy according to Item 8 is characterized in that the detection method further comprises: before detecting the ethylene cracking gas, configuring the laser power of the Raman spectrometer to be greater than or equal to 1 W, configuring the line width to be less than or equal to 0.1 nm, and setting the spectrum integration time to 30 to 90 s.

[0153] Item 11. A Raman analysis device, characterized in that the Raman analysis device includes a processor and a memory, the memory storing at least one computer program, and the at least one computer program being loaded and executed by one or more of the above processors so that the processor executes the Raman analysis method for the mixed gas content according to any one of claims 1 to 7.

[0154] Item 12. A computer-readable storage medium, characterized in that the computer-readable storage medium stores at least one program code, and the program code is loaded and executed by a processor to enable a computer to perform the Raman analysis method for mixed gas content described in any one of Items 1-7.

[0155] Item 13. An online detection system for ethylene cracking gas based on Raman spectroscopy, characterized in that the detection system comprises a sampling unit, a Raman spectrometer, and the Raman analysis equipment described in Item 11;

[0156] One end of the sampling unit is connected to the outlet pipeline of the ethylene cracking furnace, and the other end of the sampling unit is connected to a Raman spectrometer. The Raman spectrometer is used to detect the sample gas extracted by the sampling unit to obtain the original Raman spectrum of the ethylene cracking gas. The Raman analysis equipment is connected to the Raman spectrometer to analyze the original Raman spectrum of the ethylene cracking gas and obtain the mole fraction of each key component of the ethylene cracking gas.

[0157] Example

[0158] The following embodiments will further illustrate the method of the present application in conjunction with the accompanying drawings, but the present application is not limited thereto.

[0159] I) Equipment and raw materials

[0160] The following devices and materials were used during the implementation of this embodiment:

[0161] Cracking unit: CBL type reaction unit designed and developed by Sinopec;

[0162] Laser: Changchun New Industries Laser MGL-N-532-3W, spectral linewidth ≤ 0.15nm, power 2.3W;

[0163] Raman probe: Jiangyin Yunxiang RPB-532-N-FF;

[0164] Optical fiber: commercially available, suitable for 532 nm laser;

[0165] Raman spectrometer: Ocean Optics QE Pro, whose detector is a back-illuminated CCD detector array with TEC;

[0166] Gas chromatograph: Agilent 7890A, using Agilent HP-5A molecular sieve column (for H2 and CH4) and Agilent HP-PLOTAl2O3 column (for other hydrocarbon gases), and Agilent thermal conductivity detector (TCD) (for H2) and Agilent flame ionization detector (FID) (for hydrocarbon gases).

[0167] 15 standard gas samples: purchased from Dalian Date Gas Co., Ltd., each containing pure substances with nitrogen as the balance gas and the following volume percentages: methane 90.04%, ethane 90.14%, ethylene 90.80%, acetylene 1.00%, propylene 49.62%, propane 50.30%, propyne 1.01%, propadiene 1.01%, 1.3-butadiene 9.80%, 1-butene 9.72%, isobutylene 10.32%, cis-2-butene 10.00%, trans-2-butene 9.97%, n-butane 9.97%, isobutane 9.64%;

[0168] Reaction raw materials: naphtha, its density at 20℃ (d4 20 ) is 0.6826 g / cm 3 , the distillation properties are shown in Table 1:

[0169] Table 1: Distillation properties of the reaction raw material naphtha Note: The initial distillation point refers to the temperature when the first drop of raw material is distilled out, and the final distillation point refers to the temperature when the last drop of raw material is distilled out.

[0170] II) Prepare the training sample set and determine the regression coefficients

[0171] It is known that steam cracking can produce a cracking gas mixture containing the following main components: H2, methane, ethane, ethylene, acetylene, propane, propylene, propyne, and some C4+ organic gases. The sum of the contents of these components in the cracking gas mixture is approximately equal to 100%, among which the C4+ organic gases are mainly C4 olefins and dienes. The above 15 standard gas samples were independently detected using a Raman spectrometer to obtain Raman spectra containing characteristic peaks of one of the 15 gases and N2. Due to the 2331cm -1 The peak position of N2 is known, so the characteristic peak positions of these 15 gases in the Raman spectrum can be obtained. Since Raman spectrum detection produces fingerprint peaks, organic gases usually produce multiple characteristic peaks with different intensities and peak positions. Here, one characteristic peak is selected for each of the above main components and listed in Table 2.

[0172] Table 2: Characteristic peak positions of the main components in the cracked gas mixture

[0173] A naphtha reaction feedstock is added to a CBL-type cracking unit at a flow rate of 3 kg / hour, and the temperature of the cracking unit is increased. When the temperature stabilizes at 800°C, two cracked gas mixtures are collected at the cracking unit outlet after being cooled to room temperature by cooling water. One of the collected cracked gas mixture samples is irradiated by a laser via an optical fiber and a Raman probe to generate a Raman signal, which is then transmitted via the Raman probe and the optical fiber to a Raman spectrometer for Raman spectral detection. The spectral integration time is set to 50 seconds. The other collected cracked gas mixture sample is subjected to gas chromatography detection using a gas chromatograph to obtain component data within a 15-minute operating cycle.

[0174] The Raman spectrum of the cracked gas mixture was subjected to background subtraction and baseline correction. -1 The independent characteristic peak of ethylene is used as the reference peak, ethylene is used as the reference component, and each characteristic peak in the Raman spectrum is normalized to obtain a processed Raman spectrum. The characteristic peak positions of the pure substances shown in Table 2 are then used to determine the characteristic peak positions of the target components in the measured Raman spectrum of the cracked gas mixture, thereby obtaining the corresponding original relative Raman peak heights. Then, the relative Raman peak heights of their respective reference peak positions shown in Table 3 are subtracted from the original relative Raman peak heights of CH4, C2H6, C2H2, C3H8, C3H4, and C4+ to obtain their respective optimized relative Raman peak heights (not shown).

[0175] Table 3: Reference peak positions of the main components in the cracked gas mixture

[0176] Furthermore, the volume fractions of the main components in the cracked gas mixture are obtained by gas chromatography, and their volume ratios relative to the reference component ethylene are further obtained. This yields a first set of data for a training sample set comprising the relative Raman peak heights of the main components and their volume ratios relative to the reference component ethylene.

[0177] Repeat this process twice more at 800°C to obtain the second and third sets of training data. Continue increasing the cracking unit temperature by 10°C, using this process to obtain three more sets of data until the temperature reaches 880°C. This process is then repeated to obtain the final three sets of data, resulting in a total of 27 sets of training data.

[0178] The least squares algorithm was used to fit the 27 sets of data in the training sample set to obtain the regression coefficients k of the main components in the cracked gas mixture shown in Table 4. j1 and k j0 .

[0179] Table 4: Regression coefficients of the main components in the cracked gas mixture

[0180] The regression coefficient k of each main component is obtained j1 and k j0 It is used for determining the volume fraction of the corresponding main components in the online cracked gas mixture collected at the outlet of the naphtha cracking reaction unit.

[0181] III) Performing Raman spectroscopy and gas chromatography detection on the target cracked gas mixture

[0182] Naphtha reaction feedstock is continuously introduced into a CBL cracking unit at a flow rate of 3 kg / hour. The temperature of the cracking unit is increased. When the temperature stabilizes at 820°C-850°C and the reaction has run for 39 minutes, two cracked gas mixtures, cooled to room temperature by cooling water at the cracking unit outlet, are collected. One cracked gas mixture sample is irradiated with a laser via an optical fiber and a Raman probe to generate a Raman signal, which is then transmitted via the Raman probe and optical fiber to a Raman spectrometer for Raman spectral detection. The spectral integration time is set to 50 seconds, thereby obtaining a first set of data for the target cracked gas mixture. The other cracked gas mixture sample is subjected to gas chromatography using a gas chromatograph to obtain component data within 15 minutes of operation. The volume fractions of the main components in the obtained cracked gas mixture are used for comparison with the results obtained by the Raman spectroscopy method of the present invention.

[0183] The above operation was repeated when the reaction ran for 57 min, 70 min, 78 min, 94 min, 102 min, 162 min, 172 min, 191 min, 205 min, 225 min and 237 min, respectively, to obtain the 2nd to 12th groups of data of the target cracking gas mixture.

[0184] IV) Processing the Raman spectrum of the target cracked gas mixture and obtaining the relative Raman peak height

[0185] The 12 sets of Raman spectra were subjected to background subtraction, baseline correction and normalization to obtain their original relative Raman peak heights. Then, the relative Raman peak heights of the reference peak positions shown in Table 3 were subtracted from the original relative Raman peak heights of the main components of the 12 sets of data to obtain their respective optimized relative Raman peak heights. The optimized relative Raman peak heights are listed in Table 5, where the relative Raman peak height at 1345 cm -1 The independent characteristic peak of ethylene is used as the benchmark peak, and ethylene is used as the reference component.

[0186] Table 5: Optimized relative Raman peak heights of the main components in the cracked gas mixture

[0187] V) Calculate the volume fraction of the main components in the target cracking gas mixture

[0188] For n=9 main components, namely H2, methane, ethane, ethylene, acetylene, propane, propylene, propyne and C4+ organic gases, their respective regression coefficients k shown in Table 4 are j1 and k j0 The optimized relative Raman peak heights of the respective components shown in Table 5 are substituted into the formulas (3) and (6) shown below to obtain the volume fraction of each main component in the cracked gas mixture. j =k j0 +k j1 P j ,(j=1,…,9) (3)

[0189] z j is the molar ratio or volume ratio of the jth component in the target cracking gas mixture to the reference component, P j is the relative Raman peak height of the jth component in the target cracking gas mixture, k j0 is the first regression coefficient of the jth component in the target cracking gas mixture, k j1 is the second regression coefficient of the jth component in the target cracked gas mixture, where j=1 corresponds to ethylene.

[0190] c j is the mole fraction or volume fraction of the jth component in the target cracking gas mixture, zj is the molar ratio or volume ratio of the jth component in the target cracked gas mixture to the reference component, and z is the molar ratio or volume ratio of the ith component in the target cracked gas mixture to the reference component, where j=1 corresponds to ethylene. The calculated volume fractions of the main components are listed in Table 6, and the volume fractions detected by gas chromatography are also listed in Table 6 for comparison with the analysis results of the Raman spectroscopy method of the present invention.

[0191] Table 6: Volume fractions of the four main components in the cracked gas mixture obtained using the Raman spectroscopy method of the present invention and the gas chromatography method not of the present invention

[0192] For a more intuitive comparison, the volume fraction results of the four key components H2, CH4, C2H4, and C3H6 in Table 6 are plotted as Figure 8. From the data in Table 6 and Figure 8, it can be seen that the volume fractions of the four key components in the cracked gas mixture obtained using the Raman spectroscopy method of the present invention are substantially the same as or very similar to the volume fractions obtained using gas chromatography, thereby proving that the Raman spectroscopy method of the present invention can accurately obtain the content of each component in the online gas mixture. However, due to the long detection time of gas chromatography, it takes an analysis cycle of 15 minutes or longer to obtain the volume fractions of a group of major components using gas chromatography, while it only takes about 1 minute to obtain the volume fractions of a group of major components using the Raman spectroscopy method of the present invention. Therefore, compared to gas chromatography, the Raman spectroscopy method of the present invention can significantly more quickly obtain results with comparable accuracy.

[0193] For large-scale production processes (e.g., annual production of 100,000 tons or more) in which the reaction raw materials remain essentially the same and the reaction type and conditions are similar over a long period of time (e.g., one year or longer), the Raman spectroscopy method of the present invention can quickly and accurately obtain the online detection content of each key component in the gas mixture, thereby enabling the online reaction process parameters to be quickly and accurately adjusted, thereby effectively improving the yield of key components (e.g., ethylene).

[0194] Within the technical concept of the present invention, various modifications can be made to the above technical solution of the present invention, and these modifications all fall within the protection scope of the present invention.

[0195] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction.

[0196] In addition, the various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for determining the content of a target component in a gas mixture by Raman spectroscopy, wherein the method comprises: 1) Performing Raman spectroscopy detection on the gas mixture to obtain a Raman spectrogram; 2) Selecting a characteristic peak from the Raman spectrogram as a reference peak, and the corresponding component as a reference component, and normalizing the characteristic peaks of each target component in the Raman spectrogram with respect to the reference peak to obtain the relative Raman peak height of each characteristic peak; 3) Combining the Raman spectrogram of the pure target component to determine the peak positions of the characteristic peaks of each target component in the Raman spectrogram of the gas mixture; 4) Determining the molar ratio or volume ratio of the target component to the reference component in the gas mixture based on the relative Raman peak height of the characteristic peak at the specific peak position of the target component obtained in steps 2) and 3) and one or more, preferably one or two regression coefficients obtained from the training sample set of the gas mixture; and 5) Determining the molar fraction or volume fraction of each target component in the gas mixture based on the molar ratio or volume ratio of the target component to the reference component obtained in step 4).

2. The method according to claim 1, wherein the gas mixture is a process gas mixture collected at the outlet of a continuous reactor and / or an on-line detection gas mixture.

3. The method according to claim 1 or 2, wherein between steps 3) and 4), it includes step 3') of obtaining the optimized relative Raman peak height of the characteristic peak by subtracting the relative Raman peak height of the reference peak at a reference point within 50 cm, preferably within 30 cm, near the respective peak positions from the relative Raman peak height of one or more characteristic peaks obtained by the normalization process in step 2). -1 Therein, the reference point is within 50 cm, preferably within 30 cm -1 from the relative Raman peak height of the reference peak at the reference point to obtain the optimized relative Raman peak height of the characteristic peak).

4. The method according to any one of the preceding claims, wherein the training sample set of the gas mixture comprises the Raman spectrogram of the gas mixture and the molar ratio or volume ratio of the target component to the reference component in the gas mixture.

5. The method according to claim 4, wherein the molar ratio or volume ratio of the target component to the reference component in the gas mixture of the training sample set is obtained by measuring the content of each target component in the gas mixture by gas chromatography.

6. The method according to any one of claims 2 to 5, wherein the regression coefficient is determined by the following steps: i) Collecting gas mixture samples at the outlet of a continuous reactor at two or more time points, preferably 5 or more time points, more preferably 10 or more time points, still more preferably 15 or more time points; ii) Performing Raman spectroscopy detection and gas chromatography detection on the gas mixture samples collected at the same time point respectively, wherein the relative Raman peak height of the target component is obtained from the measured Raman spectrogram and preferably according to the methods of steps 2) and 3), and the molar ratio or volume ratio of the target component to the reference component is obtained by gas chromatography detection, and the corresponding relative Raman peak heights and the molar ratio or volume ratio obtained at each time point form a training sample set; and iii) Using this training sample set and combining a statistical regression model to establish the relationship between the relative Raman peak height and the molar ratio or volume ratio described in step ii), thereby obtaining the regression coefficient.

7. The method according to any one of the preceding claims, wherein the method includes a step 1') of background subtraction and baseline correction for the Raman spectrogram of the gas mixture between steps 1) and 2).

8. The method according to any one of the preceding claims, wherein In step 1), the gas mixture for Raman spectroscopy detection is a gas mixture at normal temperature and pressure.

9. The method according to any one of the preceding claims, wherein the gas mixture comprises two or more, preferably three or more, more preferably five or more, still more preferably seven or more organic gases, such as 2 to 20, or 3 to 20, or 5 to 15, or 7 to 10 organic gases. Preferably, the organic gas is a gas composed of carbon and hydrogen elements and optionally having unsaturated bonds, wherein the organic gas preferably has one to seven carbon atoms, more preferably one to four carbon atoms, still more preferably one to three carbon atoms.

10. The method according to any one of the preceding claims, wherein the gas mixture comprises n target components (n is an integer greater than or equal to 2, preferably greater than or equal to 3, more preferably greater than or equal to 5), and the molar ratio or volume ratio of the target components to the reference component in the gas mixture in step 4) is obtained by calculating with the following formula (2): z j = k j P j , (j = 1, …, n) (2) Among them, z j is the molar ratio or volume ratio of the j-th component in the gas mixture to the reference component, P j is the relative Raman peak height of the j-th component in the gas mixture, k j is the regression coefficient of the j-th component in the gas mixture, where j = 1 corresponds to the reference component.

11. The method according to any one of the preceding claims, wherein the gas mixture comprises n target components (n is an integer greater than or equal to 2, preferably greater than or equal to 3, more preferably greater than or equal to 5), and the molar ratio or volume ratio of the target components to the reference component in the gas mixture in step 4) is obtained by calculation using the following formula (3): z j = k j0 + k j1 P j , (j = 1, …, n) (3) Among them, z j is the molar ratio or volume ratio of the j-th component in the gas mixture to the reference component, P j is the relative Raman peak height of the j-th component in the gas mixture, k j0 is the first regression coefficient of the j-th component in the gas mixture, k j1 is the second regression coefficient of the j-th component in the gas mixture, where j = 1 corresponds to the reference component.

12. The method according to any one of the preceding claims, wherein the gas mixture comprises n target components (n is an integer greater than or equal to 2, preferably greater than or equal to 3, more preferably greater than or equal to 5), and the mole fraction or volume fraction in step 5) is obtained by calculation using the following formulas (4) and (6): c1 + c2 + … + c n = 1 (4), Among them, c j is the mole fraction or volume fraction of the j-th component in the gas mixture, z j is the molar ratio or volume ratio of the j-th component in the gas mixture to the reference component, j = 1, …, n, where j = 1 corresponds to the reference component.

13. The method according to any one of the preceding claims, wherein the gas mixture is an ethylene cracking gas mixture containing ethylene obtained by a cracking reaction, preferably a steam cracking reaction.

14. The method according to claim 13, wherein the ethylene cracking gas mixture comprises hydrogen, methane, ethane, ethylene, acetylene, propane, propylene, propyne and optionally butene and / or butadiene, and the reference component of the ethylene cracking gas mixture is preferably ethylene.

15. The method according to claim 13 or 14, wherein the characteristic peak of ethylene located near 1345 cm -1 is used as the reference peak.

16. The method according to any one of claims 13 to 15, wherein the Raman spectroscopy detection is carried out under the following conditions: the laser power is greater than or equal to 1 W, preferably 1 W to 3 W; and / or the spectral line width is less than or equal to 0.2 nm, preferably less than or equal to 0.15 nm; and / or the spectral integration time is 30 s to 90 s, preferably 50 s to 70 s, more preferably 45 s to 60 s.

17. A Raman spectroscopy analysis device, comprising a processor and a memory, wherein at least one computer program is stored in the memory, and when the at least one computer program is executed by the processor, the processor executes the method for determining the content of the target component in the gas mixture by Raman spectroscopy according to any one of claims 1 to 16.

18. A computer-readable storage medium, wherein at least one program instruction is stored, and when the program instruction is executed by a processor, the processor executes the method for determining the content of the target component in the gas mixture by Raman spectroscopy according to any one of claims 1 to 16.

19. A computer program product, comprising at least one program instruction, and when the program instruction is executed by a processor, the processor executes the method for determining the content of the target component in the gas mixture by Raman spectroscopy according to any one of claims 1 to 16.

20. An on-line detection and analysis system for a gas mixture based on Raman spectroscopy, comprising a sampling unit, a Raman spectroscopy detection unit and the Raman spectroscopy analysis device according to claim 17; The sampling unit is respectively connected to the outlet pipeline of the reactor and to the Raman spectroscopy detection unit, wherein the Raman spectroscopy detection unit is used to perform Raman spectroscopy detection on the gas mixture collected by the sampling unit to obtain a Raman spectrogram of the gas mixture; the Raman spectroscopy detection unit is also connected to the Raman spectroscopy analysis device, wherein the Raman spectroscopy analysis device is used to analyze the Raman spectrogram of the gas mixture to obtain the mole fraction or volume fraction of each target component in the gas mixture.

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