Gas chromatography method for detecting trace sulfur in synthesis gas

Abstract

The invention belongs to the technical field of analytical chemistry and industrial gas detection, and discloses a gas chromatography method for detecting trace sulfur in synthesis gas, which comprises a sample injector, a chromatographic column, a detector and a data processing unit, and is characterized in that the system adopts an open tubular capillary chromatographic column with short size and small inner diameter; according to the present invention, by combining the constant temperature box and the chromatographic column flow control mode, various sulfides (such as H2S, COS and the like) in the synthesis gas are not separated in the chromatographic system, but flow out through the combined chromatographic peak, and based on the characteristics of good inertness and low adsorption of the system, only the single sulfide standard gas (such as COS standard gas) is required to perform calibration, such that the calibration accuracy is high; the total sulfur content in the synthesis gas can be rapidly and accurately quantified by detecting the area of the combined peak. The method is short in analysis time, low in detection limit and suitable for rapid quality monitoring of the synthesis gas process.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of analytical chemistry and industrial gas detection, in particular to a gas chromatography method for detecting trace sulfur in synthesis gas. BACKGROUND

[0002] Coal synthesis gas and purified gas contain a certain amount of sulfides, which exist in various forms, mainly including inorganic sulfur (mainly hydrogen sulfide H2S) and organic sulfur (such as carbonyl sulfur COS, mercaptan, sulfide, thiophene, etc.). Different forms of sulfur pose a multi-dimensional and systematic harm to the whole process of coal chemical industry, and are a key factor affecting the safe, stable, efficient and environmentally friendly operation of the device. Among them, hydrogen sulfide (H2S) as the highest content of sulfur form, has the most extensive and intense influence. H2S can irreversibly and strongly poison noble metal catalysts (such as Cu, Zn, Ni, Co-based catalysts used in methanol synthesis, Fischer-Tropsch synthesis, methanation and shift reaction), leading to rapid deactivation and causing huge economic losses. Even ppb (parts per billion) level of residual, long-term accumulation can also cause serious damage.

[0003] As part of the organic sulfur, carbonyl sulfur (COS) is an example. Compared with H2S, COS has stronger chemical inertness at low temperature, which leads to its possible "penetration" to the downstream in the normal temperature desulfurization unit (such as low-temperature methanol wash) as it cannot be completely absorbed. The penetrated COS will undergo hydrolysis reaction (COS + H2O → CO2 + H2S) under the action of high temperature and shift catalyst after entering the shift section, generating H2S in situ. This is equivalent to "reinjection" inside the system, not only poisoning the expensive and efficient shift catalyst, but also making the total sulfur in the purified gas exceed the standard, which poses a serious threat to the subsequent synthesis section. Therefore, accurate and rapid detection of the total sulfur content in synthesis gas is of great importance to process control and product quality.

[0004] At present, gas chromatography (GC) is often used in combination with sulfur-specific detectors (such as FPD, SCD) for analysis. However, the existing technology has obvious defects:

[0005] (1) Serious matrix interference: High concentrations of H2, CO, CO2 and other main components in synthesis gas will interfere with the detection of sulfides, and conventional chromatographic columns are difficult to achieve effective separation of sulfides under complex matrix.

[0006] (2) System adsorption and decomposition: Traditional chromatographic columns and piping systems have active sites, which are prone to adsorb polar sulfides such as H2S, resulting in low detection results, peak tailing and memory effect, and the authenticity of the data is difficult to guarantee.

[0007] (3) Analysis cycle is long and calculation is complicated: in order to separate various sulfur forms, a programmed temperature is usually adopted, and the analysis time is up to 20 minutes or more. The total sulfur calculation needs to be quantified for each separated sulfur peak and then summed up, which not only requires that the chromatographic column has very high separation capacity, but also needs to be equipped with multiple sulfur standard gas, and the method development is complex, high in cost and low in efficiency.

[0008] Therefore, the technical field urgently needs a new technical scheme capable of overcoming the above-mentioned defects and realizing rapid, accurate and simple detection of trace total sulfur in synthesis gas, and for this purpose, the present application provides a gas chromatography method for detecting trace sulfur in synthesis gas to solve the above problems. SUMMARY

[0009] In view of the deficiencies of the prior art, the present application provides a gas chromatography method for detecting trace sulfur in synthesis gas, which can significantly reduce the adsorption of sulfides, greatly shorten the analysis time and simplify the calibration process.

[0010] To achieve the above-mentioned purpose, the present application provides a gas chromatography method for detecting trace sulfur in synthesis gas, comprising a sample injector, a chromatographic column, a detector and a data processing unit, characterized in that: the chromatographic column is an open-tube capillary column with a short size and a small inner diameter, and the specifications are: length 1-10 meters, inner diameter 0.10-0.25 millimeters; the system configuration can make various sulfides in the synthesis gas sample flow out in the form of a combined chromatographic peak, thereby realizing quantitative analysis of total sulfur.

[0011] As a preferred technical scheme of the present application, the specifications of the open-tube capillary column are preferably length 5 meters and inner diameter 0.18 millimeters. Compared with the traditional long packed column or capillary column, the mass transfer resistance of the short column is small, which can effectively avoid the separation phenomenon of sulfides in the column due to strong adsorption or delayed diffusion, and is the key to realizing the rapid "unified peak" of various sulfides.

[0012] Preferably, the detector is a detector with high selectivity to sulfides, preferably a flame photometric detector (FPD) or a sulfur chemiluminescence detector (SCD).

[0013] Preferably, the gas chromatography method for detecting trace sulfur in synthesis gas comprises the following steps:

[0014] a. Set the chromatographic column box to constant temperature mode, the temperature range is 60-80℃, and the split ratio is 1-5;

[0015] b. Set the carrier gas control mode to chromatographic column flow control, and the flow range is 3-8 mL / min;

[0016] c. Inject the synthesis gas sample into the sample inlet, so that the various sulfides in the sample enter the detector in the form of a unified chromatographic peak after passing through the chromatographic column.

[0017] d. The detector detects the uniform chromatographic peak and outputs a peak area signal;

[0018] e. The data processing unit compares the peak area signal with a calibration curve established using a single sulfide standard gas to calculate the total sulfur content in the syngas.

[0019] Preferably, the chromatographic column oven adopts a constant temperature mode, with a preferred constant temperature of 70°C, a constant temperature time of ≥2 minutes, and a preferred split ratio of 2. Compared with programmed temperature rise, the constant temperature mode further shortens the analysis cycle and ensures the reproducibility of the analysis results.

[0020] Preferably, the carrier gas is high-purity helium (He), high-purity hydrogen (H2), high-purity oxygen (O2), and high-purity nitrogen (N2), and the preferred carrier gas flow rate is 5 mL / min, with a linear velocity of 199.1 cm / s. This mode can provide a stable and high carrier gas flow rate, which helps to drive the sulfides through the chromatographic column quickly and in a concentrated manner, preventing them from staying in the column for too long and undergoing adsorption or separation.

[0021] Preferably, the single sulfide standard gas is carbonyl sulfide (COS) standard gas or hydrogen sulfide (H2S) standard gas.

[0022] Preferably, the method has a detection limit of 0.01 ppm or higher for total sulfur (v / v).

[0023] Compared with existing technologies, the present invention provides a gas chromatography method for detecting trace sulfur in syngas, which has the following advantages:

[0024] 1. This invention utilizes a short-sized open-tube capillary column with very few active sites, combined with optimized carrier gas conditions, to greatly reduce the adsorption of sulfides, and in particular, ensure the accurate quantification of H2S, thus solving the problem of target analyte loss in trace analysis.

[0025] 2. By shortening the column length and adopting isothermal analysis, this invention significantly reduces the total analysis time from 20-25 minutes in traditional methods to less than 2 minutes, meeting the needs of rapid monitoring in industrial settings.

[0026] 3. By adopting an innovative "unified peak elution" mode, this invention simplifies the complex "multi-peak separation and summation" into "single-peak quantification," requiring only one standard gas to complete the total sulfur calibration, significantly reducing the difficulty and cost of operation.

[0027] 4. This invention utilizes the system's good inertness and low adsorption properties, requiring only a single sulfide standard gas (such as COS standard gas) for calibration. It can quickly and accurately quantify the total sulfur content in syngas by detecting the area of ​​the uniform peak. Moreover, the analysis cycle is short (≤2 minutes), the sensitivity is high (detection limit can reach above 0.01 ppm), and the reproducibility is good. It is particularly suitable for rapid and accurate monitoring of trace total sulfur in syngas and purified gas in industrial sites such as coal chemical industry. Attached Figure Description

[0028] Fig. 1 This is a flow path diagram of the sulfide analysis system of the present invention;

[0029] Fig. 2 The original sulfur peak spectrum / ppm was adjusted according to the present invention.

[0030] Fig. 3 The total sulfur peak spectrum / ppb is adjusted according to the present invention. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Example

[0033] Please see Figs. 1-3 In this implementation plan, Example 1: System Configuration and Parameter Settings

[0034] Chromatograph: Gas chromatograph equipped with an autosampler valve and a sulfur chemiluminescence detector (SCD).

[0035] Chromatographic column: DB-1 open capillary column with dimensions of 5 m x 0.18 mm x 0.00 μm was used.

[0036] Operating parameters:

[0037] Column oven temperature: 70℃ (constant temperature, maintained for 2 minutes)

[0038] Inlet temperature: 200℃

[0039] Detector temperature: 250℃

[0040] Carrier gases: High-purity helium (He), high-purity hydrogen (H2), high-purity oxygen (O2), and high-purity nitrogen (N2).

[0041] Carrier gas control mode: Column flow control, set to 5.0 mL / min

[0042] Flow split ratio: 2:1

[0043] Injection volume: 2 mL (gaseous sample)

[0044] Linear speed: 199.1 cm / s.

[0045] In this embodiment, Example 2: Detection Method

[0046] Calibration curve construction: Using carbonyl sulfide (COS) standard gas at different concentrations, the samples were injected and analyzed under the above chromatographic conditions, and the retention time and peak area of ​​the uniform sulfur peak were recorded. A calibration curve was established by performing linear regression of peak area against sulfur concentration (calculated as sulfur atoms).

[0047] Sample testing: Take 2 mL of the syngas sample to be tested and analyze it under the same conditions as the calibration.

[0048] Result Calculation: The data processing system automatically identifies the peak area of ​​the uniform sulfur peak in the sample chromatogram and directly calculates the total sulfur concentration in the sample (expressed in ppm or ppb) based on the calibration curve established in step 1.

[0049] Comparative Example: Traditional Method

[0050] A 60m x 0.32mm Plot Q column was used, with programmed temperature ramping (60℃ for 5 min, then ramped up to 180℃ at 20℃ / min and held for 14 min) to analyze the same syngas sample. The results showed that sulfides such as H2S and COS were completely separated, with an analysis cycle of up to 25 minutes, and the H2S peak exhibited tailing.

[0051] Verification of effectiveness: The method of this invention completes the analysis within 2 minutes. The total sulfur detection results are basically consistent with the summation results of the traditional method, which takes a long time. Moreover, the relative standard deviation (RSD) is less than 3% in the repeatability experiment, which proves the accuracy and reliability of this method.

[0052] In the description of this invention, the terms "comprising," "including," or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising a reference structure" does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. It should be noted that, herein, relational terms such as "first," "second," etc., are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations.

[0053] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A gas chromatography method for detecting trace sulfur in syngas, comprising an injector, a chromatographic column, a detector, and a data processing unit, characterized in that: The chromatographic column is a short-sized, small-diameter open capillary column with specifications of 1-10 meters in length and 0.10-0.25 mm in inner diameter. The system is configured to elute multiple sulfides in the syngas sample as a single merged chromatographic peak, which is then detected by the detector. The data processing unit is configured to calculate the total sulfur content in the syngas based on the signal of the merged chromatographic peak and a calibration curve established using a single sulfide standard gas.

2. The gas chromatography method for detecting trace sulfur in syngas according to claim 1, characterized in that: The preferred specifications for the open capillary column are a length of 5 meters and an inner diameter of 0.18 millimeters.

3. The gas chromatography method for detecting trace sulfur in syngas according to claim 1, characterized in that: The detector is a detector with a high selectivity to sulfides, preferably a flame photometric detector (FPD) or a sulfur chemiluminescence detector (SCD).

4. A gas chromatographic method for detecting trace sulfur in syngas according to any one of claims 1-3, characterized in that: Includes the following steps: a. Set the column oven to constant temperature mode, with a temperature range of 60-80℃ and a split ratio of 1-5; b. Set the carrier gas control mode to column flow control, with a flow rate range of 3-8 mL / min; c. Inject the syngas sample into the injection port so that the various sulfides in the sample enter the detector as a uniform chromatographic peak after passing through the chromatographic column; d. The detector detects the uniform chromatographic peak and outputs a peak area signal; e. The data processing unit compares the peak area signal with a calibration curve established using a single sulfide standard gas to calculate the total sulfur content in the syngas.

5. The gas chromatography method for detecting trace sulfur in syngas according to claim 4, characterized in that: The preferred constant temperature in step a is 70℃, the constant temperature time is ≥2 minutes, and the split ratio is optimized to 2.

6. The gas chromatography method for detecting trace sulfur in syngas according to claim 4, characterized in that: The carrier gas in step b is high-purity helium (He), high-purity hydrogen (H2), high-purity oxygen (O2) and high-purity nitrogen (N2), and the preferred carrier gas flow rate is 5 mL / min and the linear velocity is 199.1 cm / s.

7. The gas chromatography method for detecting trace sulfur in syngas according to claim 4, characterized in that: The single sulfide standard gas mentioned in step e is carbonyl sulfide (COS) standard gas or hydrogen sulfide (H2S) standard gas.

8. The gas chromatography method for detecting trace sulfur in syngas according to claim 4, characterized in that: The method achieves a detection limit of over 0.01 ppm (v / v) for total sulfur.

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