The determination of crude benzene content in coal gas before and after washing the benzene tower by gas chromatography has the advantages of high efficiency, high selectivity, high sensitivity, fast analysis speed, small sample size, and high quantitative accuracy. Gas chromatography has been widely used in the analysis of various impurity contents in coking plants. Crude benzene is a mixture of various organic compounds, mainly composed of benzene, toluene, xylene, and * benzene. In addition, it also contains a small amount of impurities such as phenols, pyridine bases, sulfides, and some unsaturated compounds. Among them, benzene and toluene have the highest content, accounting for about 80% to 90%. Benzene derivatives are toxic, especially low boiling point substances, which are even more toxic. The analysis of benzene derivatives is of great significance in coking production. The analysis of benzene derivatives in the coking industry has always used activated carbon adsorption method, which has long measurement time, high toxicity, and cannot obtain quantitative results of benzene derivatives, and cannot meet the requirements of modern production.

Analysis principle: This method uses a hydrogen flame ionization detector chromatograph, with Apison as the stationary liquid, 6201 carrier, gas collected in a gas sampling bag, and injected into the instrument through a six way valve. After separation by a chromatographic column, the components enter the hydrogen flame ionization detector one by one, and the chromatogram is obtained on the chromatographic workstation. Quantitative calibration is performed based on the external standard method at a single point.

Analyze operating conditions:

GC-2010 gas chromatograph (Tengzhou Zhongkepu)

Detector: FID；

Column length: 2 meters;

Column diameter: 3mm;

Carrier gas flow rate (N2): 30 mL/min;

Hydrogen flow rate: 30 mL/min;

Air flow rate: 300 mL/min;

Sample injector temperature (INR): 200 ℃;

Column temperature (COL): 150 ℃;

Detector temperature (DET): 200 ℃;

Attenuation: 8;

Range: 10;

Six way valve quantitative tube: 1 mL;

Analytical purity: benzene, toluene;

Syringe: 1 each of 100 mL, 10 μ L, and 1 μ L

Analysis Steps
1. Enter the standard sample
Stabilize the instrument under the aforementioned chromatographic operating conditions, use a six way valve to introduce the prepared standard sample gas, obtain the standard spectrum on the chromatographic workstation, calculate the correction factor using the calculated content of benzene and toluene in the standard sample (g/m3), repeat the above process three times, take the average correction factor, and then create a single point correction template.
2. Enter the sample to be tested
Use a six way valve to enter the collected gas sample to be tested (a glass tube is installed in front of the six way valve, with a small amount of degreased cotton inside to prevent contamination of the chromatographic column caused by high gas moisture), obtain the sample spectrum, and use the above template to calculate the content of benzene and toluene (g/m3) using the external standard method. Under the above chromatographic conditions, the chromatograms of benzene in the obtained gas are shown in Figure 1, Figure 2, and Figure 3. From Figures 1, 2, and 3, it can be seen that under the selected chromatographic conditions, benzene and toluene in the gas can be separated from other components in the gas, with sharp peaks and reasonable retention time.

Testing substance:Benzene in gas

Before and after using the benzene washing towerChromatographic determination method for crude benzene content in coal gasGreatly reducing inspection costs, improving the accuracy and reliability of testing, shortening testing time, and increasing the recovery rate of coking crude benzene. This method has the following characteristics: firstly, it shortens the analysis cycle; Secondly, it has improved the accuracy of analysis; The third is to use a six way valve to seal the sampling, which basically eliminates the pollution of benzene and its homologues to the environment. At the same time, the environmental toxicity during the operation process is low, which improves the working environment; Fourthly, the sampling volume is small, the operation is simple, and easy to master; Fifth, the reproducibility of the measurement results is good, and the accuracy and precision of the results can meet the needs of production control