Method for analyzing carbon dioxide product gas of an mdea decarbonization process

Abstract

The application discloses a kind of MDEA decarburization process carbon dioxide product gas analysis method, including establishing only the analysis method of analyzing the impurity component except carbon dioxide in sample;Carbon dioxide component in sample is cut off system by valve switching, only other gas enters corresponding detector and is detected;Through single standard gas and mixed standard gas operation gas chromatograph, establish mixed standard quantitative calibration curve;Using pre-evacuation aluminum foil sampling bag field sampling;Through gas chromatographic column, the component to be measured is separated, the content of impurity in gas is detected using hydrogen flame ionization detector and thermal conductivity cell detector, load mixed standard quantitative calibration curve and correct chromatogram, obtain the content of impurity, the content of carbon dioxide is calculated by difference method.Solve carbon dioxide product gas sample in chromatographic analysis process High concentration carbon dioxide can cause thermal conductivity cell detector output signal overrange, appear analysis value greater than 100%, the obtained analysis data does not have effectiveness, cannot adopt the problem of credibility.

Description

Technical Field

[0001] This invention relates to the field of analytical detection technology for the decarbonization of MDEA, an intermediate product of natural gas-to-ethylene glycol production, and specifically to an analytical method for carbon dioxide product gas from the MDEA decarbonization process. Background Technology

[0002] The conversion gas, produced from natural gas and oxygen through an oxidation reaction to generate carbon monoxide and hydrogen as active ingredients, enters the lower part of the absorption tower in the decarbonization unit. The regenerated gas enters the absorption tower from the middle, flowing counter-currently upwards and contacting the lean MDEA compound amine solution coming from the top of the tower for heat and mass transfer. Carbon dioxide in the gas is absorbed, and the purified gas is drawn from the top of the tower and sent to the next process. The MDEA compound amine solution, having absorbed carbon dioxide, exits from the bottom of the absorption tower, recovers energy through a turbine, and then undergoes depressurized flash evaporation to remove some hydrocarbons. It then exchanges heat with the lean solution from the regeneration tower and enters the upper part of the regeneration tower, where it comes into counter-current contact with stripping steam generated by the bottom reboiler, releasing the remaining carbon dioxide. The better-regenerated solution from the bottom of the regeneration tower exchanges heat with the rich solution through a lean-rich solution heat exchanger, is cooled to approximately 40°C by a lean solution cooler, and is then pressurized by a lean solution pump before entering the absorption tower for recirculation absorption. The regenerated gas exiting from the top of the regeneration tower is cooled to 40°C by a regeneration gas cooler, and then the condensate is recovered by a gas-liquid separator before being sent out of the unit. The condensate is pressurized and returned to the regeneration tower by a reflux pump. The drain liquid and system makeup solvent are returned to the underground tank, and then pumped back to the solution storage tank by the underground tank pump to maintain the system solution concentration.

[0003] Direct emission of high-concentration carbon dioxide into the atmosphere not only exacerbates the greenhouse effect, increases corporate carbon emissions, and consumes carbon quotas, hindering both corporate low-carbon development and the achievement of societal dual-carbon goals, but also possesses resource value. It can be supplied to downstream enterprises for liquefaction and purification, finding wide applications in oilfield enhanced oil recovery and food preservation. The rational utilization of high-concentration carbon dioxide as a resource will not only avoid increasing corporate production costs but also create considerable economic, environmental, and social benefits.

[0004] However, the MDEA decarburization process The product gas contains a large amount of moisture. Traditional methods use cyclone separators to remove liquid water, but lack measures to remove gaseous water and gaseous MDEA. If gaseous moisture and alkaline gaseous MDEA from the sample enter the chromatograph, it can easily cause permanent damage to the chromatographic valve, column, and detector.

[0005] Meanwhile, the MDEA decarburization process The product gas composition is complex, typically containing... (High concentration of main components) , , , Multiple impurities such as CO, and Extremely high concentrations (typically >95%). Conventional gas chromatography with direct injection analysis... A peak value that is extremely large can cause the TCD detector output signal to exceed its range, resulting in an analytical value greater than 100%. The peak tailing is severe, masking the impurity peaks that emerge later. Multiple injections are required to analyze different components separately, resulting in low efficiency and unreliable analytical data.

[0006] Therefore, existing analytical methods need to be improved to address the problems of easily damaged chromatographic valves, columns, and detectors, as well as unreliable analytical data when analyzing carbon dioxide product gas. Summary of the Invention

[0007] In order to solve one or more technical problems existing in the prior art, the purpose of this application is to provide an analytical method for carbon dioxide product gas in the MDEA decarbonization process, which solves the problem that when high concentrations of carbon dioxide in the sample cause the thermal conductivity detector output signal to exceed the range during chromatographic analysis, resulting in analytical values ​​greater than 100%, the obtained analytical data is not valid and cannot be accepted.

[0008] To solve the aforementioned technical problems, this application adopts the following technical solution: An analytical method for carbon dioxide product gas from the MDEA decarbonization process, the analytical method comprising the following steps: S1. Set the parameters of the gas chromatograph: Establish an analytical method that analyzes only impurity components other than carbon dioxide in the sample; S2. Set valve switching parameters: By switching the valve, the carbon dioxide component in the sample is removed from the system, so that carbon dioxide does not enter the chromatographic column and detector, and only methane, hydrogen, oxygen, nitrogen and carbon monoxide enter the corresponding detector for detection. S3. Establish a standard curve: Use a gas chromatograph with single standard gas and mixed standard gas to perform qualitative and quantitative analysis on the analytes of carbon dioxide product gas and establish a mixed standard quantitative calibration curve. S4. Sample collection and processing: Samples are collected on-site using pre-vacuumed aluminum foil sampling bags to ensure that the carbon dioxide product gas is fully replaced in the aluminum foil bags. Samples are injected immediately after being brought back to the laboratory. The sampling process involves using aluminum foil sampling bags that have been pre-vacuumed with a vacuum pump, connecting the aluminum foil sampling bag and the sampler with a clean latex tube, opening the inlet and outlet of the aluminum foil sampling bag, and circulating the sampler to ensure that the sample in the aluminum foil bag is fully replaced for at least 3 minutes. S5. Sample Analysis: The components to be analyzed are separated by gas chromatography column. The content of impurities in the gas is detected by hydrogen flame ionization detector and thermal conductivity detector. The chromatogram is corrected by loading a mixed standard quantitative calibration curve to obtain the impurity content. The carbon dioxide content is calculated by difference method.

[0009] Preferably, the gas chromatograph includes an injection port, a column system, a valve switching system, an FID detector, a TCD1 detector, and a TCD2 detector; the column system includes an MC-1 packed column, an MC-2 packed column, an MC-3 capillary column, and an MC-4 packed column; the valve switching system includes a 10-way valve V1, a 6-way valve V2, a 6-way valve V3, and a 10-way valve V4; a coalescing filter and a 4A molecular sieve drying trap are added before the injection port; the coalescing filter is used to remove liquid water, and the 4A molecular sieve drying trap is used to remove gaseous water vapor and alkaline gaseous MDEA solution.

[0010] Due to the MDEA decarburization process The product gas contains a large amount of moisture. Traditional methods use cyclone separators to remove liquid water, but lack measures for removing gaseous water and alkaline gaseous MDEA. When gaseous moisture in the sample enters the chromatograph injection system, firstly, the water vapor comes into contact with the chromatograph valve body, causing valve switching jamming, poor sealing, and gas leakage. It can also cause chromatographic columns such as MS-13X to quickly become saturated and fail after absorbing water, resulting in a sharp decline in separation performance. Water vapor entering the detector can cause the FID detector flame to go out. Secondly, alkaline gaseous MDEA entering the chromatograph causes severe corrosion to the valve bodies and seals (such as stainless steel, PEEK, etc.) of the six-way valve V2 and ten-way valves V1 / V4, ultimately leading to frequent valve failure, severe drift in analytical data, and the need for frequent valve replacement, resulting in extremely high maintenance costs.

[0011] Therefore, a coalescing filter and a 4A molecular sieve drying trap are connected in series at the sample inlet. The inlet of the coalescing filter is connected to the sample acquisition device via the sample inlet line, and the outlet of the coalescing filter is connected to the inlet of the 4A molecular sieve drying trap. The outlet of the 4A molecular sieve drying trap is connected to the sample inlet of the gas chromatograph. The coalescing filter is used to intercept liquid water and MDEA solvent droplets in the sample gas; the 4A molecular sieve drying trap is used to deeply remove gaseous water and gaseous MDEA solution from the sample gas. After double-layer drying and dehydration, the moisture content in the sample gas is ≤10ppm and the dew point temperature is ≤-55℃.

[0012] By installing a coalescing filter and a 4A molecular sieve drying trap at the chromatograph inlet, the MDEA decarbonization process can be effectively removed. The presence of liquid water, gaseous water, and trace amounts of MDEA solvent in the product gas prevents corrosion and contamination of the chromatographic valve by water vapor and solvent, extends the service life of the chromatographic valve, and improves the stability and reliability of analytical data.

[0013] Preferably, the coalescing filter is a coalescing type filter capable of intercepting droplets ≥0.01μm, with a filtration accuracy of 0.01μm to 0.1μm, a filter element material of borosilicate glass fiber or stainless steel sintered filter element, a rated working pressure of 0.1MPa to 2.5MPa, and a rated flow rate of 0.5mL / min to 50mL / min.

[0014] The coalescing filter intercepts liquid water and MDEA solvent droplets ≥0.01μm, protecting the downstream 4A molecular sieve drying trap from saturation by liquid water and MDEA solution, thus extending the service life of the molecular sieve.

[0015] Preferably, the 4A molecular sieve drying trap is filled with 4A type molecular sieve with a particle size of 3Å to 5Å and a filling amount of 1mL to 5mL; both the inlet and outlet ends of the 4A molecular sieve drying trap are equipped with filter elements to prevent molecular sieve dust from entering the downstream pipeline.

[0016] The 4A molecular sieve drying trap lowers the dew point to below -55°C, deeply removing gaseous water and gaseous MDEA solution; the synergistic protection mechanism significantly extends the service life of the six-way valve V2 and the ten-way valve V1 / V4, effectively reducing maintenance costs, and significantly improving the stability of analytical data, with the peak area RSD decreasing from 4.5% to 1.2%.

[0017] Preferably, the setting of the valve switching parameters includes: Methane is detected by the FID detector via the six-way valve V3, and the accurate value is obtained. Hydrogen gas passes through the ten-way valve V4, which is responded to by the TCD2 detector, and the accurate value is detected. Carbon dioxide, oxygen, nitrogen, and carbon monoxide are passed through the ten-way valve V1. By setting different valve switching times, the carbon dioxide component is removed from the system and does not enter the chromatographic column and detector. The oxygen, nitrogen, and carbon monoxide components after carbon dioxide is removed are then detected by the TCD1 detector via the six-way valve V2.

[0018] Preferably, the six-way valve V2 is initially in a single-line position: the sample is first pre-separated by MC-2. , , CO first flows out into the TCD-1 pathway. If the fluid is trapped by the chromatographic column and does not elute, Relay2(1) is triggered in advance to switch the V2 biline position. It will be directly vented through the CC-7 bypass pipe, bypassing the TCD-1 detector and discharged from the entire system. This triggers Relay2(0), V2 resets the single-line position, and subsequently... , , The CO component is separated by MC-2 along the original pathway and then enters TCD-1 for detection.

[0019] The six-way valve V3 is initially in single-line position: Relay3(1) is triggered to switch to dual-line position. The sample in the 500μL quantitative loop is pushed into the SPL split injection port by the carrier gas, and after separation by the MC-3 alumina capillary column, it is sent to the FID detector for detection. After the injection process is completed, Relay3(0) is triggered, and V3 switches back to single-line position to complete the reset.

[0020] The initial single-line position of the 10-way valve V4 triggers Relay4(1) to switch to dual-line position, and the sample in the 1 mL quantitative loop is carried into the TCD-2 analysis pathway by the carrier gas; waiting After the components have completely eluted and entered the MC-4 column, Relay4(0) is triggered to switch V4 back to single line position and perform backflushing operation on the components at the back end of the column; Quantitative detection was performed using TCD-2 alone.

[0021] This system employs a dual-detector, multi-column, and multi-valve collaborative switching architecture, solving the problem that a single column cannot complete the separation of all components. , , The retention times of CO and MC-1 are close, which can easily lead to peak overlap. The system relies on valve switching to switch column pathways: MC-1 and MC-2 are connected in series via a V1 10-way valve for separation. , CO is separated by switching the flow path to MC-3 / MC-4 via the V2 six-way valve. , Based on the design of a single valve switching separation channel, it realizes single injection and multi-channel parallel analysis, which is different from the traditional multiple injection mode.

[0022] This is achieved through the V1 ten-way valve. Online resection timing control: Strong retention on the MC-1 column, with precise control of the V1 switching time, until... Once fully introduced into the column, it is locked in place, allowing the light components to pass through. , After all the CO flows out, then Cut and drain; this online resection method avoids Subsequent chromatographic column and detector inputs address high concentrations. This can cause detector saturation and column overload issues; in contrast, traditional processes do not require configuration. Trapping traps or dilution injections simplify operations and reduce the risk of introducing errors.

[0023] The six-way valve V2 is initially in single-line position: the sample is first pre-separated by MC-2, and CO flows out first into the TCD-1 passage. If the fluid is trapped by the chromatographic column and does not elute, Relay2(1) is triggered in advance to switch the V2 biline position. It will be directly vented through the CC-7 bypass pipe, bypassing the TCD-1 detector and discharged from the entire system. This triggers Relay2(0), V2 resets the single-line position, and subsequently... , , The CO component is separated along the original path by MC-2 and then enters TCD-1 for detection.

[0024] The six-way valve V3 is initially in single-line position: Relay3(1) is triggered to switch to dual-line position. The sample in the 500μL quantitative loop is pushed into the SPL split injection port by the carrier gas, and after separation by the MC-3 alumina capillary column, it is sent to the FID detector for detection. After the injection process is completed, Relay3(0) is triggered, and V3 switches back to single-line position to complete the reset.

[0025] The initial single-line position of the 10-way valve V4 triggers Relay4(1) to switch to dual-line position, and the sample in the 1 mL quantitative loop is carried into the TCD-2 analysis pathway by the carrier gas; waiting After the components have completely eluted and entered the MC-4 column, Relay4(0) is triggered to switch V4 back to single line position and perform backflushing operation on the components at the back end of the column; Quantitative detection was performed using TCD-2 alone.

[0026] Preferably, the gas chromatograph parameters in S1 are set as follows: Vaporization chamber: temperature 150℃; pressure 83kPa; total flow rate: 113mL / min; purging flow rate: 3mL / min; split ratio: 10:1; MC-1 chromatographic column: 80 / 100 mesh 3.2mm×2.1mm×1.0M; MC-2 chromatographic column: 80 / 100 mesh 3.2mm×2.1mm×3.0M; Chromatographic column MC-3: HP-AL / S 50.0m × 0.53mm × 15μm; MC-4 chromatographic column: 80 / 100 mesh 3.2mm×2.1mm×3.0M; FID detector: 200℃; TCD1 detector: 150℃; TCD2 detector: 150℃; Nitrogen was used as the carrier gas; hydrogen was used as the fuel gas with a flow rate of 40 mL / min; air was used as the combustion-supporting gas with a flow rate of 400 mL / min; and nitrogen was used as the tail gas with a flow rate of 30 mL / min.

[0027] Preferably, the parameters for setting the valve switching in S2 include: The six-way valve V2 is initially in single-line position, and the sample is first pre-separated by MC-2. , , CO first flows out into the TCD-1 pathway. The fluid was trapped by the chromatographic column and did not elute. At this time, Relay2(1) was triggered to switch the V2 biline position. The system is vented directly through the CC-7 bypass branch line, bypassing the TCD-1 detector and exiting the system; this triggers Relay2(0), V2 resets the single-line position, and subsequent... , , The CO component is separated by MC-2 along the original pathway and then enters TCD-1 for detection; The six-way valve V3 is initially in single-line position, triggering Relay3(1) to switch to dual-line position. The sample in the 500μL quantitative loop is pushed into the SPL split injection port by the carrier gas, and after separation by the MC-3 alumina capillary column, it is sent to the FID detector for detection. After the injection process is completed, Relay3(0) is triggered, and V3 switches back to single-line position to complete the reset. The 10-way valve V4 is initially in single-line position, triggering Relay4(1) to switch to dual-line position. The 1 mL sample in the quantitative loop is carried into the TCD-2 analysis pathway by the carrier gas; waiting... After the components have completely eluted and entered the MC-4 column, Relay4(0) is triggered to switch V4 back to single line position and perform backflushing operation on the components at the back end of the column; Quantitative detection was performed using TCD-2 alone.

[0028] Preferably, the single-standard gas in S3 includes: A1. A single standard gas containing low levels of methane in carbon dioxide, with a carbon dioxide content of 99.9% and a methane content of 0.1%. A2. A single standard gas containing low levels of hydrogen in carbon dioxide, with a carbon dioxide content of 99.9% and a hydrogen content of 0.1%. A3. A single standard gas containing low levels of oxygen in carbon dioxide, with a carbon dioxide content of 99.9% and an oxygen content of 0.1%. A4. A single standard gas containing low levels of nitrogen in carbon dioxide, with a carbon dioxide content of 99.9% and a nitrogen content of 0.1%. A5. Carbon dioxide contains a low concentration of carbon monoxide, a single standard gas with a carbon dioxide content of 99.9% and a carbon monoxide content of 0.1%.

[0029] Preferably, the mixed standard gas in S3 includes: B1, Standard Gas Gradient 1: Carbon dioxide content 99.75%, methane content 0.05%, hydrogen content 0.05%, oxygen content 0.05%, nitrogen content 0.05%, carbon monoxide content 0.05%; B2, Standard Gas Gradient 2: Carbon dioxide content 99.5%, methane content 0.1%, hydrogen content 0.1%, oxygen content 0.1%, nitrogen content 0.1%, carbon monoxide content 0.1%; B3, Standard Gas Gradient 3: Carbon dioxide content 99.0%, methane content 0.2%, hydrogen content 0.2%, oxygen content 0.2%, nitrogen content 0.2%, carbon monoxide content 0.2%.

[0030] If the impurity concentration is increased to 1%, A peak area that is too small leads to an increase in the difference error; if it is reduced to 0.01%, the impurity peak area is too small and the signal-to-noise ratio is insufficient. Using a multi-gradient method to establish a mixed standard quantitative calibration curve results in better accuracy.

[0031] Preferably, the sample analysis step in S5 includes: C1. Connect the aluminum foil gas bag containing the sample to the injection port of the gas chromatograph and purge for 1 minute; C2. Run the analytical method in S1 to analyze the carbon dioxide product gas sample; C3. After the method is completed, load the mixed standard quantitative calibration curve in S3 to correct the chromatogram, and then obtain the content of various components in the carbon dioxide product gas sample.

[0032] Preferably, the carbon dioxide content is calculated by subtraction, and the calculation formula is: carbon dioxide content (%) = 100% - methane content (%) - oxygen content (%) - nitrogen content (%) - carbon monoxide content (%) - hydrogen content (%).

[0033] MDEA decarbonization Product air Extremely high content (>95%), while impurity content is extremely low (ppm~% level). Direct analysis using conventional methods is possible. Peak area, but high concentration The poor linear relationship between peak area and injection volume (detector partial saturation) leads to low quantitative accuracy. Furthermore, direct analysis using the external standard method... Extremely high precision injection volume control is required, while impurity analysis requires high sensitivity.

[0034] Therefore, this invention does not directly quantify. Instead, it is cut off by switching valves. Afterwards, only the impurity components were analyzed ( , , , (CO), then subtract the sum of the contents of each impurity from 100% to obtain The content and impurity components show good linear response at low concentrations, high quantitative accuracy, and elimination of [unclear - possibly related to impurity content]. The nonlinear response error of the detector caused by high concentration can be eliminated, and full component analysis can be completed with a single injection without the need to prepare high-concentration and low-concentration standard gases separately.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows: When detecting carbon dioxide product gas, the chromatographic peaks of methane, oxygen, nitrogen, carbon monoxide, and hydrogen in the sample can be completely separated, resulting in high analytical accuracy. The system is simple and easy to operate. By adjusting the valve switching parameters, carbon dioxide can be cut off from the system to prevent the thermal conductivity detector output signal from exceeding the range and causing analytical values ​​to exceed 100%, thus solving the problem of invalid and unreliable analytical data. Attached Figure Description

[0036] Figure 1 This is a diagram showing the valve opening of the gas chromatograph used in this invention; Figure 2 The FID detector chromatogram of carbon dioxide product gas established for this invention; Figure 3 Chromatogram of carbon dioxide product gas using a TCD1 detector established for this invention; Figure 4 The TCD2 detector chromatogram of the carbon dioxide product gas established for this invention. Detailed Implementation

[0037] The present application will now be further described in conjunction with the accompanying drawings and specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0038] In the description of this application, it should be understood that the terms "upper", "lower", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0039] The terms "first," "second," etc., used in this application are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class, without limiting the number of objects; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship. Example 1:

[0040] like Figures 1-4 As shown, An analytical method for carbon dioxide product gas from the MDEA decarbonization process, the analytical method comprising: Step S1: Set the parameters of the gas chromatograph and establish an analytical method for carbon dioxide product gas containing only other impurities in the product gas. Step S2: Set the parameters for valve switching: Methane responds to and is detected accurately by the FID detector via the six-way valve V3; hydrogen responds to and is detected accurately by the TCD2 detector via the ten-way valve V4; carbon dioxide, oxygen, nitrogen, and carbon monoxide are switched through the ten-way valve. By setting different valve switching times, the carbon dioxide component is removed from the system and does not enter the chromatographic column or detector. The oxygen, nitrogen, and carbon monoxide components after the carbon dioxide is removed are then detected by the TCD1 detector via the six-way valve.

[0041] The valve switching times are as follows: Relay1: 0.01 min to dual-line position, 4.00 min to single-line position; Relay2: 1.30 min to dual-line position, 2.30 min to single-line position; Relay3: 0.01 min to dual-line position, 1.00 min to single-line position; Relay4: 0.01 min to dual-line position, 0.47 min to single-line position.

[0042] Step S3: Establish a standard curve: Run the gas chromatograph after passing through single standard gas and mixed standard gas; perform qualitative analysis of the analytes in the carbon dioxide product gas by measuring the single standard gas; and perform quantitative analysis of the analytes in the carbon dioxide product gas by measuring the mixed standard gas. Step S4, Sample Collection and Processing: Use pre-vacuumed aluminum foil sampling bags for on-site sampling to fully replace the carbon dioxide product gas in the aluminum foil bags. After the sample is brought back to the laboratory, it is injected immediately. Step S5, Sample Analysis: During chromatographic analysis, the sample in the aluminum foil sampling bag is directly injected through the injection port with the injection valve. The components to be tested are separated by the gas chromatography column. Impurities in the gas are analyzed by the hydrogen flame ionization detector and the thermal conductivity detector. The mixed standard quantitative calibration curve from step S2 is loaded to correct the chromatogram, thereby obtaining the accurate content of impurities in the carbon dioxide product gas sample. The carbon dioxide content is calculated by the difference method.

[0043] The required equipment for the decarbonization of high-carbon dioxide content in MDEA includes a gas chromatograph, and necessary accessories such as a gas injection tube, a GC-2014 gas chromatograph, capillary columns and packed column flow paths, an FID detector, a TCD detector, a gas injection valve, a chemical workstation control system, and a chromatographic data processing system. The chromatographic principle is as follows: a sample taken in an aluminum foil sampling bag is injected through the gas injection tube, separated by an AL / S column, and detected by a flame ionization detector and a thermal conductivity detector. Qualitative analysis is based on retention time, and quantification is performed using the external standard method. Instrument technical specifications include: (1) Gas chromatograph parameter settings: Vaporization chamber: temperature 150℃; pressure 83kPa; total flow rate: 113mL / min; purging flow rate: 3mL / min; split ratio: 10:1; Column (MC-1): 80 / 100 mesh 3.2mm × 2.1mm × 1.0M Chromatographic column (MC-2): 80 / 100 mesh 3.2mm × 2.1mm × 3.0M Chromatographic column (MC-3): HP-AL / S 50.0m × 0.53mm × 15μm Column (MC-4): 80 / 100 mesh 3.2mm × 2.1mm × 3.0M FID detector: 200℃; TCD1 detector: 150℃; TCD2 detector: 150℃; Nitrogen was used as the carrier gas; hydrogen was used as the fuel gas with a flow rate of 40 mL / min; air was used as the combustion-supporting gas with a flow rate of 400 mL / min; and nitrogen was used as the tail gas with a flow rate of 30 mL / min.

[0044] (2) Data acquisition and data analysis The software requires an integrated data structure, facilitating analysis and information traceability through quantitative and data browsers. It boasts rich computational and data comparison functions, displays relative retention times, and features automatic retention time correction. The software interface can be flexibly customized to fit the workflow. It offers highly flexible report generation capabilities, allowing quick selection of various template files and supporting custom template creation. Standard PDF output is included. High-precision QA / QC functions support automatic calculation of methodological indicators such as noise, drift, signal-to-noise ratio, LOD, LOQ, precision, and recovery rate. It also includes instrument system inspection and user safety management functions.

[0045] (3) Spare parts and special tools: Standard gas and standard solution for installation, commissioning and annual use and list, spare parts and special tools for equipment installation, commissioning and maintenance.

[0046] (4) The capillary column uses Shimadzu imported brand chromatographic columns that meet the same separation effect and guarantee column efficiency for three years.

[0047] (5) Computer Software: Windows 10 Professional Edition In step S1, the detailed parameters of the gas chromatograph are set as follows: vaporization chamber: temperature 150℃; pressure 83kPa; total flow rate: 113mL / min; purge flow rate: 3mL / min; split ratio: 10:1; total analysis time: 10min; chromatographic column: HP-AL / S50.0m×0.53mm×15μm; detector: flame ionization detector, temperature 200℃; thermal conductivity detector 1, temperature 150℃; thermal conductivity detector 2, temperature 150℃; nitrogen is used as carrier gas, hydrogen as fuel gas, and air as combustion-supporting gas; make-up gas flow rate: 30mL / min; hydrogen flow rate: 40mL / min; air flow rate: 400mL / min.

[0048] 2. Standard gas preparation includes A1. A single standard gas containing low levels of methane in carbon dioxide, with a carbon dioxide content of 99.9% and a methane content of 0.1%. A2. A single standard gas containing low levels of hydrogen in carbon dioxide, with a carbon dioxide content of 99.9% and a hydrogen content of 0.1%. A3. A single standard gas containing low levels of oxygen in carbon dioxide, with a carbon dioxide content of 99.9% and an oxygen content of 0.1%. A4. A single standard gas containing low levels of nitrogen in carbon dioxide, with a carbon dioxide content of 99.9% and a nitrogen content of 0.1%. A5. Carbon dioxide contains a low concentration of carbon monoxide, a single standard gas with a carbon dioxide content of 99.9% and a carbon monoxide content of 0.1%.

[0049] B1. A mixed gas of carbon dioxide products, with a carbon dioxide content of 99.5%, methane content of 0.1%, hydrogen content of 0.1%, oxygen content of 0.1%, nitrogen content of 0.1%, and carbon monoxide content of 0.1%.

[0050] 3. The parameters for setting valve switching include: The six-way valve V2 is initially in single-line position: the sample is first pre-separated by MC-2. , , CO first flows out into the TCD-1 pathway. If the fluid is trapped by the chromatographic column and does not elute, Relay2(1) is triggered in advance to switch the V2 biline position. It will be directly vented through the CC-7 bypass pipe, bypassing the TCD-1 detector and discharged from the entire system. This triggers Relay2(0), V2 resets the single-line position, and subsequently... , , The CO component is separated along the original pathway by MC-2 and then enters the TCD-1 for detection. The six-way valve V3 is initially in single-line position: triggering Relay3(1) to switch to dual-line position, the sample in the 500μL quantitative loop is pushed into the SPL split injection port by the carrier gas, separated by the MC-3 alumina capillary column, and then sent to the FID detector for detection; after the injection process is completed, triggering Relay3(0), V3 switches back to single-line position to complete the reset. The ten-way valve V4 is initially in single-line position: triggering Relay4(1) to switch to dual-line position, the sample in the 1mL quantitative loop is carried into the TCD-2 analysis pathway by the carrier gas; waiting... After the components have completely eluted and entered the MC-4 column, Relay4(0) is triggered to switch V4 back to single line position and perform backflushing operation on the components at the back end of the column; Quantitative detection was performed using TCD-2 alone.

[0051] The six-way valve V2 is initially in single-line position: the sample is first pre-separated by MC-2. , , CO first flows out into the TCD-1 pathway. The sample was retained by the column and did not elute; 1.30 min after injection, Relay2(1) was triggered to switch to V2 bilinear position. It will be vented directly through the CC-7 bypass line, bypassing the TCD-1 detector and exiting the entire system. Relay2(0) is triggered 2.30 minutes after sample injection, V2 resets the single-line position, and subsequently... , , The CO component, after being separated along the original path by MC-2, enters TCD-1 for detection. The V1 ten-way valve is initially in single-line position: after 0.01 min of injection, Relay1(1) is triggered to switch to dual-line position, realizing the cascade connection of MC-1 and MC-2 columns; relying on precise timing control, after the light components are separated, After the retention is completed, Relay1(0) is triggered 4.00 min after sample injection, V1 is reset to the single-line position, and the process is complete. Online cut-off and emptying. Six-way valve V3 initial single-line position: 0.01 min after injection triggers Relay3(1) to switch to dual-line position. The sample in the 500 μL quantitative loop is pushed into the SPL split injection port by the carrier gas, separated by the MC-3 alumina capillary column, and sent to the FID detector for detection; 1.00 min after injection triggers Relay3(0), and V3 switches back to single-line position to complete reset. Ten-way valve V4 initial single-line position: 0.01 min after injection triggers Relay4(1) to switch to dual-line position. The sample in the 1 mL quantitative loop is carried into the TCD-2 analysis pathway by the carrier gas; waiting... After the components have completely eluted and entered the MC-4 column, Relay4(0) is triggered 0.47 min after injection to switch V4 back to single-line position and perform backflushing operation on the components at the back end of the column; Quantitative detection was performed using TCD-2 alone.

[0052] 4. Sample collection and processing C1. Use a pre-vacuumed aluminum foil sampling bag for on-site sampling, allowing the carbon dioxide product gas to be fully replaced in the aluminum foil bag. After the sample is taken back to the laboratory, connect the aluminum foil gas bag with the sample taken to the injection port of the gas chromatograph and replace it for 1 minute. C2. Run the analytical method in step S1 to analyze the carbon dioxide product gas sample; C3. After the method is completed, load the mixed standard quantitative calibration curve from step S2 to correct the chromatogram, and then the content of various components in the carbon dioxide product gas sample can be obtained.

[0053] During sample analysis, a gas injection tube is connected to an aluminum foil sampling bag and the chromatographic injection port. The collected sample is passed through the chromatographic valve for 1 minute to purge, and the carbon dioxide product gas method is run. After the carbon dioxide product gas method is completed, a quantitative calibration curve is applied to correct the chromatogram, thus determining the content of impurities in the sample: methane, oxygen, nitrogen, carbon monoxide, and hydrogen. The accurate carbon dioxide content is then obtained by subtracting the impurity content using the difference method.

[0054] The extremely high carbon dioxide content in the carbon dioxide product gas can cause the thermal conductivity detector output signal to exceed its range, resulting in analytical values ​​greater than 100%, rendering the obtained analytical data invalid and unreliable. This method uses adjustable valve parameters to cut off carbon dioxide from the system, accurately determining the contents of methane, oxygen, nitrogen, carbon monoxide, and hydrogen in the carbon dioxide product gas. The accurate carbon dioxide content is obtained by calculating the difference between the impurity content and the actual content. This method offers high accuracy, simplicity, and ease of operation.

[0055] The improved device no longer suffers from valve body damage. Only the coalescing filter element needs to be replaced annually, usually every six months. The market price of each filter element is about 200 yuan (domestic). Even if imported filter elements are used, the market price is less than 2,000 yuan each.

[0056] Comparative Example 1 Traditional analytical methods only involve installing a cyclone separator at the sampling port in the process area to remove liquid moisture from the sample. After the sample is retrieved and brought back to the laboratory, it is directly injected into the chromatograph for analysis, using an FID + dual TCD detector configuration to determine... , , , , CO component.

[0057] Due to the sample High concentration, and , , , The content of impurities such as CO is low. To ensure the detection accuracy of low-content impurities, it is necessary to increase the chromatographic injection volume; however, increasing the injection volume will result in high concentrations. Component injection overload manifests as Chromatographic peaks exhibiting flat-topped peaks and severe tailing are easily masked. , The chromatographic peaks. Simultaneously... Due to the large injection volume of the components, the peak repeatability deteriorates, and it is usually necessary to repeat the injection 3-4 times to obtain parallel and reliable sample detection data.

[0058] Furthermore, the statistical analysis method lacks measures for removing gaseous water and gaseous MDEA. Water vapor and gaseous MDEA easily cause wear, leakage, corrosion, and failure of the chromatographic valves, requiring the replacement of two 10-way valves and one 6-way valve annually. Currently, the market price for a 10-way valve is 5,600 yuan, and the market price for a 6-way valve is 5,100 yuan. Since the company cannot replace the chromatographic valves itself, the cost of after-sales personnel is approximately 4,500 yuan, bringing the total annual maintenance costs for chromatographic valves to approximately 20,000 yuan.

[0059] The following is a comparison of nine data points obtained from direct injection detection of carbon dioxide product gas in the MDEA decarbonization process and injection using the method of Example 1. The experimental results are shown in Table 1 below: Table 1: Carbon dioxide content 104.17% 99.63% Carbon dioxide content 101.46% 99.62% Carbon dioxide content 103.52% 99.60% Carbon dioxide content 104.79% 99.57% Carbon dioxide content 104.01% 99.61% Carbon dioxide content 102.33% 99.64% Carbon dioxide content 100.78% 99.63% Carbon dioxide content 105.935% 99.62% Carbon dioxide content 102.15% 99.59% RSD% 1.62% 0.02% As shown in Table 1, due to the extremely high carbon dioxide content in the carbon dioxide product gas, direct injection of the sample would cause the thermal conductivity detector output signal to exceed its range, rendering the obtained analytical data invalid and unreliable. However, the improved method, when analyzing the inlet sample of the carbon dioxide product gas from the MDEA decarbonization process, solves the problem of the carbon dioxide product gas sample causing the thermal conductivity detector output signal to exceed its range during chromatographic analysis, ensuring that the obtained analytical data is valid and reliable.

[0060] Table 2 shows a comparison of the analysis of carbon dioxide product gas from the MDEA decarbonization process using the traditional method and this method over the past two years.

[0061] Analysis cycle At least three injections are required (to analyze different components separately). Single injection full analysis Efficiency increased by more than 3 times <![CDATA[CO2 quantification accuracy]]> RSD 3%~5% (high concentration nonlinear) RSD 0.5%~1.5% (difference subtraction method) Accuracy improved by 6 to 10 times Is preprocessing required? Cyclone separators are used only to remove liquid water; no measures are taken to remove gaseous water and alkaline gaseous MDEA. Liquid water is removed using a coalescing filter, and gaseous water vapor and alkaline gaseous MDEA are removed using a 4A molecular sieve drying trap. The service life of chromatographic valves and columns is increased by 3 to 4 times. Annual maintenance costs Approximately 20,000 yuan Approximately 0.5 million yuan Reduced by 75% The above embodiments are merely preferred embodiments of this application and should not be construed as limiting the scope of protection of this application. Any non-substantial changes and substitutions made by those skilled in the art based on this application shall fall within the scope of protection claimed by this application.

Claims

1. A method for analyzing carbon dioxide product gas from the MDEA decarbonization process, characterized in that, The analytical method includes the following steps: S1. Set the parameters of the gas chromatograph: Establish an analytical method that analyzes only impurity components other than carbon dioxide in the sample; S2. Set valve switching parameters: By switching the valve, the carbon dioxide component in the sample is removed from the system, so that carbon dioxide does not enter the chromatographic column and detector, and only methane, hydrogen, oxygen, nitrogen and carbon monoxide enter the corresponding detector for detection. S3. Establish a standard curve: Use a gas chromatograph with single standard gas and mixed standard gas to perform qualitative and quantitative analysis on the analytes of carbon dioxide product gas and establish a mixed standard quantitative calibration curve. S4. Sample collection and processing: Samples are collected on-site using pre-vacuumed aluminum foil sampling bags to ensure that the carbon dioxide product gas is fully replaced in the aluminum foil bags. Samples are injected immediately after being brought back to the laboratory. S5. Sample Analysis: The components to be analyzed are separated by gas chromatography column. The content of impurities in the gas is detected by hydrogen flame ionization detector and thermal conductivity detector. The chromatogram is corrected by loading a mixed standard quantitative calibration curve to obtain the impurity content. The carbon dioxide content is calculated by difference method.

2. The method for analyzing carbon dioxide product gas from the MDEA decarbonization process according to claim 1, characterized in that: The gas chromatograph includes an injection port, a column system, a valve switching system, an FID detector, a TCD1 detector, and a TCD2 detector; the column system includes an MC-1 packed column, an MC-2 packed column, an MC-3 capillary column, and an MC-4 packed column; the valve switching system includes a 10-way valve V1, a 6-way valve V2, a 6-way valve V3, and a 10-way valve V4; a coalescing filter and a 4A molecular sieve drying trap are added before the injection port. The coalescing filter is used to remove liquid water, and the 4A molecular sieve drying trap is used to remove gaseous water vapor and gaseous MDEA solution.

3. The method for analyzing carbon dioxide product gas from the MDEA decarbonization process according to claim 2, characterized in that: The valve switching parameters are set as follows: Methane is detected by the FID detector via the six-way valve V3, and the accurate value is obtained. Hydrogen gas passes through the ten-way valve V4, which is responded to by the TCD2 detector, and the accurate value is detected. Carbon dioxide, oxygen, nitrogen, and carbon monoxide are passed through the ten-way valve V1. By setting different valve switching times, the carbon dioxide component is removed from the system and does not enter the chromatographic column and detector. The oxygen, nitrogen, and carbon monoxide components after carbon dioxide is removed are then detected by the TCD1 detector via the six-way valve V2.

4. The method for analyzing carbon dioxide product gas from the MDEA decarbonization process according to claim 1, characterized in that: The gas chromatograph parameters in S1 are set as follows: Vaporization chamber: temperature 150℃; pressure 83kPa; total flow rate: 113mL / min; purging flow rate: 3mL / min; split ratio: 10:1; MC-1 chromatographic column: 80 / 100 mesh 3.2mm×2.1mm×1.0M; MC-2 chromatographic column: 80 / 100 mesh 3.2mm×2.1mm×3.0M; Chromatographic column MC-3: HP-AL / S 50.0m × 0.53mm × 15μm; MC-4 chromatographic column: 80 / 100 mesh 3.2mm×2.1mm×3.0M; FID detector: 200℃; TCD1 detector: 150℃; TCD2 detector: 150℃; Nitrogen was used as the carrier gas; hydrogen was used as the fuel gas with a flow rate of 40 mL / min; air was used as the combustion-supporting gas with a flow rate of 400 mL / min; and nitrogen was used as the tail gas with a flow rate of 30 mL / min.

5. The method for analyzing carbon dioxide product gas from the MDEA decarbonization process according to claim 1, characterized in that: The parameters for setting the valve switching in S2 include: The six-way valve V2 is initially in single-line position, and the sample is first pre-separated by MC-2. , , CO first flows out into the TCD-1 pathway. The fluid was trapped by the chromatographic column and did not elute. At this time, Relay2(1) was triggered to switch V2 to dual-line position, and it was directly vented through the CC-7 bypass line, bypassing the TCD-1 detector and exiting the system; Relay2(0) was triggered, V2 was reset to single-line position, and subsequently... , , The CO component is separated by MC-2 along the original pathway and then enters TCD-1 for detection; The six-way valve V3 is initially in single-line position, triggering Relay3(1) to switch to dual-line position. The sample in the 500μL quantitative loop is pushed into the SPL split injection port by the carrier gas, and after separation by the MC-3 alumina capillary column, it is sent to the FID detector for detection. After the injection process is completed, Relay3(0) is triggered, and V3 switches back to single-line position to complete the reset. The 10-way valve V4 is initially in single-line position, triggering Relay4(1) to switch to dual-line position. The 1 mL sample in the quantitative loop is carried into the TCD-2 analysis pathway by the carrier gas; waiting... After the components have completely eluted and entered the MC-4 column, Relay4(0) is triggered to switch V4 back to single line position and perform backflushing operation on the components at the back end of the column; Quantitative detection was performed using TCD-2 alone.

6. The method for analyzing carbon dioxide product gas from the MDEA decarbonization process according to claim 1, characterized in that: The single-standard gas in S3 includes: A1. A single standard gas containing low levels of methane in carbon dioxide, with a carbon dioxide content of 99.9% and a methane content of 0.1%. A2. A single standard gas containing low levels of hydrogen in carbon dioxide, with a carbon dioxide content of 99.9% and a hydrogen content of 0.1%. A3. A single standard gas containing low levels of oxygen in carbon dioxide, with a carbon dioxide content of 99.9% and an oxygen content of 0.1%. A4. A single standard gas containing low levels of nitrogen in carbon dioxide, with a carbon dioxide content of 99.9% and a nitrogen content of 0.1%. A5. Carbon dioxide contains a low concentration of carbon monoxide, a single standard gas with a carbon dioxide content of 99.9% and a carbon monoxide content of 0.1%.

7. The method for analyzing carbon dioxide product gas from the MDEA decarbonization process according to claim 1, characterized in that: The mixed standard gas in S3 includes: B1, Standard Gas Gradient 1: Carbon dioxide content 99.75%, methane content 0.05%, hydrogen content 0.05%, oxygen content 0.05%, nitrogen content 0.05%, carbon monoxide content 0.05%; B2, Standard Gas Gradient 2: Carbon dioxide content 99.5%, methane content 0.1%, hydrogen content 0.1%, oxygen content 0.1%, nitrogen content 0.1%, carbon monoxide content 0.1%; B3, Standard Gas Gradient 3: Carbon dioxide content 99.0%, methane content 0.2%, hydrogen content 0.2%, oxygen content 0.2%, nitrogen content 0.2%, carbon monoxide content 0.2%.

8. The method for analyzing carbon dioxide product gas from the MDEA decarbonization process according to claim 1, characterized in that: The sample analysis steps in S5 include: C1. Connect the aluminum foil gas bag containing the sample to the injection port of the gas chromatograph and purge for 1 minute; C2. Run the analytical method in S1 to analyze the carbon dioxide product gas sample; C3. After the method is completed, load the mixed standard quantitative calibration curve in S3 to correct the chromatogram, and then obtain the content of various components in the carbon dioxide product gas sample.

9. The method for analyzing carbon dioxide product gas from the MDEA decarbonization process according to claim 1, characterized in that: The carbon dioxide content is calculated by the difference method, and the calculation formula is: carbon dioxide content (%) = 100% - methane content (%) - oxygen content (%) - nitrogen content (%) - carbon monoxide content (%) - hydrogen content (%).

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