Remove Impurity Method and Technology in Acetylene Production from CaC2

During the production of acetylene by carbide method, various impurity gases are generated, including hydrogen sulfide (H2S), phosphine (PH3), arsine (AsH3), and moisture. These impurities not only affect the quality of acetylene, but may also pose safety hazards for subsequent use. The following are the systematic removal methods and technical standards for impurities in acetylene production by Inner Mongolia Menghua Chemicals Co., Ltd.

1. Hydrogen Sulfide (H2S) Removal Methods;

As one of the most common impurities, Hydrogen sulfide (H2S) primarily originates from the reaction between Calcium sulfide (CaS) in calcium carbide and water. Effective removal methods include:

Copper Sulfate Solution Treatment ：

Principle: H2S reacts with CuSO4 solution to form CuS precipitate and H2SO4；

Reaction: H2S + CuSO4 → CuS↓ + H2SO4

Features: Simple operation, high removal efficiency, suitable for labs and small-scale production；

Precautions: Regular CuSO4 solution replacement required to avoid saturation；

Sodium Hydroxide Neutralization ：

Principle: Neutralization reaction between H2S and NaOH solution；

Reaction: H2S + 2NaOH → Na2S + 2H2O

Features: Effective for high-concentration H2S but generates sulfur-containing wastewater；

Application: Often used as secondary purification combined with oxidation methods；

Sodium Hypochlorite Oxidation ：

Principle: Oxidizes H2S to H2SO4 using NaClO's oxidative properties；

Reaction: 4NaClO + H2S → H2SO4 + 4NaCl

Features: Ideal for large-scale industrial production with >99% purification efficiency；

Parameters: Typical NaClO solution concentration≈0.10%；

2. Phosphine (PH3) Removal Methods;

Phosphine (PH3) from the reaction of Calcium phosphide (Ca3P2) in calcium carbide with water, and its removal method includes：

Copper Sulfate Solution Treatment :‌

Principle: PH3 reacts with CuSO4 to form Cu3P precipitate；

Features: Simultaneous H2S & PH3 removal but requires acidic control；

Limitations: Limited effectiveness for low-concentration PH3；

Sodium Hypochlorite Oxidation :

Principle: NaClO oxidizes PH3 to H3PO4；

Reaction: 4NaClO + PH3 → H3PO4 + 4NaCl

Process: Typically conducted in same scrubber as H2S removal；

Key: Requires temperature and pH control；

Ferric Chloride-Diatomite Filler Technology ：

Principle: FeCl3 oxidizes PH3 with diatomite as carrier；

Advantages: No wastewater, low maintenance, suitable for High-PH3 processes；

Application: Novel purification technology for dry acetylene processes；

3. Arsine (AsH3) Removal Methods;

Arsine (AsH3) comes from Calcium arsenide (Ca3As2) in calcium carbide, and its removal method is similar to that of Phosphine (PH3);

Copper Sulfate Solution Treatment :

Principle: AsH3 reacts with CuSO4 forming Cu3As precipitate；

Features: Multi-impurity removal but requires precise condition control；

Sodium Hypochlorite Oxidation :

Principle: NaClO oxidizes AsH3 to arsenic acid；

Process: Integrated with H2S、PH3 removal；

Precautions: Enhanced slag treatment to prevent arsenic pollution；

4. Moisture Removal Methods;

Affecting purity and safety, primary dehydration approaches include:

Concentrated Sulfuric Acid Drying :

Principle: Utilizes H2SO4's hygroscopicity；

Parameters: 98% H2SO4 at 20-40°C in drying towers；

Effect: Achieves ≤0.05% moisture (per GB 6819-2004)；

Molecular Sieve Drying :

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；

Dry Process Dehydration :

Features: Preliminary dehydration via dust-cooling towers；

Advantage: 60%+ water savings compared to wet processes；

5. Acetylene Purification System Workflow;

Complete systems typically involve:

Gas Cooling & Pretreatment：Crude acetylene cooled below 40°C，Coarse impurities removed via flame arrestors and separators.

Purification Treatment :

Primary scrubber: 0.10% NaClO oxidizes H2S/PH3/AsH3；

Secondary scrubber: Further oxidation；

Alkali wash: 15% NaOH neutralizes acidic byproducts；

Drying Dehydration :

H2SO4 towers or molecular sieve units;

Dew point monitoring ensures compliance;

Compression & Storage :

Pressure maintained below 1.5MPa;

Cylinders packed with porous material and acetone solvent;

6. Technological Trends;

Dry Process Adoption :‌

Atomized water reactions reduce wastewater; Advanced fillers lower maintenance costs;

Smart Control Systems :‌

Real-time monitoring of parameters; Automated reagent dosing;

Eco-Innovations :‌

Waste utilization (e.g., carbide slag cement); Closed-loop water systems achieving zero discharge;