‌Test Method and Standard for Impurities in Acetylene Produced from CaC2

During the production of acetylene by carbide method, various impurity gases are generated, which not only affect the quality of acetylene but may also pose safety hazards for subsequent use. The following are the comprehensive detection methods and technical standards for impurities in acetylene produced by Inner Mongolia Menghua Chemicals Co., Ltd.

1. Common impurity types and sources in Acetylene；

The main impurities in acetylene produced from calcium carbide include:

Hydrogen Sulfide (H2S)‌: Generated by the reaction of calcium sulfide (CaS) in calcium carbide with water；

‌Phosphine (PH3)‌: Produced by the reaction of calcium phosphide (Ca3P2) in calcium carbide with water；

‌Arsine (AsH3)‌: Formed by the reaction of calcium arsenide (Ca3As2) in calcium carbide with water；

‌Moisture‌: Originates from the reaction water and environmental humidity；

2. Impurity Testing Methods；

1）General Testing Methods ：

Gas Chromatography ‌: Used to determine acetylene purity and trace impurities (e.g., oxygen, nitrogen)；

‌Chemical Absorption Method‌: Quantitatively detects acidic gas impurities such as H2S and PH3 through specific reagent reactions；

‌Dew Point Method ‌: Measures moisture content in gas cylinders, with a standard requirement of ≤0.05%；

2） Hydrogen Sulfide (H2S) Testing Method ：

Methylene Blue Spectrophotometry, Hydrogen Sulfide (H2S) reacts with p-aminodimethylaniline to form methylene blue, measured at 665nm absorbance.

3） Phosphine (PH3) Testing Method ：

Spectrophotometry, Bromine water oxidizes PH3 to phosphate ions, which react with ammonium molybdate to form molybdenum blue, measured at 700nm.

4）Moisture Testing Method ：

Dew Point Method,Measures gas dew point temperature and converts it to moisture content.

3. Testing Equipment and Usage；

Common Testing Equipment

Acetylene Detector‌: Uses electrochemical or infrared sensor technology, suitable for explosion-proof environments, range 0–10,000 ppm.

Hydrogen Sulfide Detector‌: Electrochemical sensor, range 0–100 ppm, minimum reading 1 ppm, response time ≤30 seconds.

Phosphine Detector‌: Modular design with intelligent sensor detection technology.

Moisture Analyzer‌: Dew point analyzer, measurement range down to -22°C dew point.

Equipment Usage Guidelines

‌Installation Location‌: Select height based on gas density (acetylene detectors should be installed above potential leak sources).

‌Regular Calibration‌: Calibrate every 6–12 months using standard gases.

‌Alarm Settings‌: Recommended three-level alarms (low: 0.5%, high: 1.0%, critical: 2.0%).

‌Maintenance‌: Regularly inspect sensors, displays, and batteries; keep equipment clean and dry.

4. Testing Frequency and Sampling Methods；

Sampling Methods

Randomly select products pre-approved by the manufacturer.

Sample 2 cylinders per batch (1 for testing, 1 as backup), with a minimum sampling base of 10 cylinders.

Use dedicated steel cylinders for sampling.

Testing Frequency

Routine testing cycle: 3–5 working days.

Real-time monitoring of key parameters (temperature, pressure, etc.) during production.

Full-item testing required before product release.

Principle: Selective water adsorption by molecular sieves；

Advantages: Deep drying, easy regeneration, ideal for electronic-grade acetylene；

Application: Widely used in PVC production to extend catalyst life；

5. Result Evaluation Standards (Chinese Standard);

‌Acetylene Purity‌: ≥99.5% (volume fraction).

‌Hydrogen Sulfide Content‌: ≤0.1% (volume fraction).

‌Phosphine Content‌: ≤0.05% (volume fraction).

‌Moisture Content‌: ≤0.05% (mass fraction).

6. Safety Precautions；

Ensure proper ventilation before testing to prevent gas accumulation.

Operators must wear personal protective equipment (respirators, protective suits, etc.).

Avoid electromagnetic interference and humid environments for detectors.

Immediately stop testing and investigate if abnormal readings occur.

Through systematic testing methods and strict standard controls, the quality of acetylene produced from calcium carbide can meet national standards, ensuring safe usage.