Comparison of desulfurization before and after coke oven gas treatment

Gas Chromatograph for Hydrogen Sulfide Analysis in Gas (trace hydrogen sulfide, major hydrogen sulfide) Overview: In gas, coke oven gas contains high levels of hydrogen sulfide (H2S), which poses a significant threat to the air environment as well as to human health and product production; therefore, the H2S content in gas must be strictly controlled. Product quality inspection and in-process control analysis in coking plants primarily rely on traditional chemical analysis methods. Among the conventional methods for measuring hydrogen sulfide content in gas, gas chromatography will become an effective tool for the inspection of chemical products and for intermediate control analysis in the coking industry. Methods for detecting hydrogen sulfide in gas: In the coking industry across the country, several methods are commonly used to measure the hydrogen sulfide content in gas. Chemical titration: This method involves calculating the weight of H2S. Advantages include high accuracy and good reproducibility, making it suitable for analyzing amounts of hydrogen sulfide that are present in relatively large quantities. Disadvantages include a long analysis time (around 2 hours), complicated procedures, and high consumption of chemical reagents. The iodine titration method specified in national standards has a high detection limit, resulting in significant errors when analyzing trace amounts of H2S. Methylene blue spectrophotometry: Suitable for the analysis of low concentrations of H2S (1–30 mg/m3). Advantages: accuracy of analysis results, as well as reduced credibility. Disadvantages: The operation steps are complex, time-consuming, and it is also limited by the detection limit. It provides little guidance on the production process. Meanwhile, both of these methods are affected by other sulfur-containing compounds. Gas chromatography: Advantages: simple operation, short processing time, and improved repeatability. Gas chromatography is now widely used; it is employed to measure the hydrogen sulfide content in coke oven gas. Tests have shown that using gas chromatography for this purpose also helps to avoid the influence of other sulfur compounds in the gas on the measurement of hydrogen sulfide. It fully meets the requirements for the routine and trace analysis of H2S at different concentrations; gas chromatography is a simple and rapid analysis method. During the coking process, coke plants produce large amounts of sulfur-containing gases such as H2S, SO2, COS, and CH3SCH3. Sulfides have a significant impact on both human health and the environment. Furthermore, it has a severe impact on the subsequent production of methanol from coke oven gas, causing a series of problems such as blockages and corrosion in the equipment and pipelines within the system, as well as catalyst poisoning and deactivation. Therefore, it is very necessary to detect and control the sulfuride content during the current production process. This sulfide is mainly composed of H2S as well, so current analysis methods are all used to analyze H2S. Experimental steps for the gas chromatograph: 1. Operate the GC-7890 model of gas chromatograph – turn on the gas switch and the power switch of the instrument. Wait until the instrument’s temperature reaches stability; this takes about 10 minutes. After that, ignite the instrument and wait until the baseline stabilizes. 2. Connect the calibration gas cylinder directly to the sample interface of the six-way valve using PTFE tubing; the outlet of the six-way valve sample is connected to an air duct, which leads the gas to a beaker filled with water to absorb any excess H2S gas. 3. Preparation of the gas chromatograph standard curve: Low-concentration standard gases are analyzed using a gas chromatograph; each sample is analyzed three times to assess its reproducibility. The average value is calculated using software, and then a standard curve is generated via the same software. The GC-7900 model gas chromatograph produced by Qingsheng Keji is equipped with an FPD detector as well as a specially treated column designed for sulfur compound analysis. The lowest detection limit of this gas chromatograph for hydrogen sulfide is 1 mg/m3. (Gas chromatograph, gas chromatograph for gas analysis, water gas chromatograph, portable gas chromatograph, analytical instrument, micro gas chromatograph, chromatograph, analytical instrument) Gas chromatograph – Instruments and reagents: GC-7900 model gas chromatograph equipped with a flame photometric detector (FPD); automatic inert six-way valve, the entire sampling system is made of polytetrafluoroethylene tubes; 1 ml polytetrafluoroethylene dosing loop. Chromatography column: 10% TCP (trimethylphenyl phosphate); the column is also made of polytetrafluoroethylene tubes. Gas sources: high-purity nitrogen, oxygen, hydrogen. Dedicated chromatography workstation. Experimental conditions for gas chromatograph analysis of gas: Column oven (COL): 50°C; Injector (ING): 200°C; Detector (DET): 200°C. Carrier gas flow rate: 30 ml/min; Hydrogen flow rate: 140 ml/min; Air flow rate: 2170 ml/min. These conditions provide optimal sensitivity and noise levels. High precision. Sample pre-treatment device: In traditional systems, a dryer filled with anhydrous CaCl2 is connected to the sample filtration gas sampling port; nowadays, sample filtration devices are used, filled with molecular sieves or desiccants. Sampling device: Sampling is carried out using sampling bags. Sampling location: Coal is taken from gas pipelines. Sampling requirements: Sampling can be performed once the temperature of the gas sample has stabilized; sampling and analysis can start directly by using sampling bags at the inlet of the six-way valve. Gas chromatograph calibration curve: Two sets of calibration curves are calculated, which is related to the instrument’s range; for concentrations that are relatively low, the highest range is used. For lower concentrations, use the smallest range. Doing this is closely related to the samples being inspected. Ensure the rationality and accuracy of sample testing. The selection of FPD detection conditions should be based on the optimal response value; choosing appropriate detection conditions will yield the best detection results. The main influencing factors are gas flow rate, detector temperature, and sample concentration. This parameter is sensitivity; a sample bag containing gas can be placed at room temperature before it is used for analysis. Each time a sample is taken, it is important to maintain a constant injection speed and volume (1 mL for the volumetric tube). Multiple parallel measurements were carried out under the same conditions, and the relative standard deviation was calculated as 18701981667

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