Core Monitored Gases: High-Risk Gases in Metallurgical Processes

The gas risks in the metallurgical industry primarily stem from fuel combustion, metal smelting reactions, and auxiliary material decomposition, involving the following four categories of critical gases:

1. Carbon Monoxide (CO) – Dual Risks of Toxicity and Explosiveness

● Source: Generated during incomplete combustion or reduction reactions in processes like blast furnace ironmaking, converter steelmaking, and coke oven gas production (e.g., ).

● Risk Characteristics: Colorless and odorless, highly toxic (200–250 times more affinity to hemoglobin than oxygen), causing hypoxia in humans (mild: headache, nausea; severe: coma, death). Its explosive limit is 5%–74% (by volume), making it prone to accumulation in enclosed or poorly ventilated areas (e.g., blast furnace tuyere platforms, gas pipeline valve rooms) and triggering explosions.

2. Hydrogen (H₂) –Highly Flammable and Explosive

● Source: Produced when water (H₂O) reacts with high-temperature metals (e.g., iron, steel) or reducing agents (e.g., carbon) during metallurgical processes (e.g.,). Some metallurgical furnaces (e.g., hydrogen-based direct reduction iron processes) also use hydrogen as a reducing agent.

● Risk Characteristics: Lighter than air (air density: 1.29 kg/m³; hydrogen: 0.089 kg/m³), it accumulates near roof areas. Its explosive limit is extremely wide (4%–75%), and it can ignite with minimal energy (static electricity or sparks).

3. Methane (CH₄) –Common Flammable Gas

● Source: A major component of coke oven gas (a byproduct of coking, typically 20%–30% of the gas mixture), or released during leaks of metallurgical furnace fuels (e.g., natural gas).

● Risk Characteristics: Explosive limit of 5%–15%, lighter than air, it gathers in elevated areas (e.g., roofs) and can explode when mixed with air and exposed to ignition sources.

4. Hydrogen Sulfide (H₂S) –Highly Toxic

● Source: Generated during high-temperature decomposition of sulfur-containing elements in iron ore, copper ore, and other raw materials (e.g., , with secondary reactions potentially producing H₂S). Coke oven gas may also contain trace H₂S (requiring desulfurization).

● Risk Characteristics: Highly toxic (threshold limit value TLV-TWA: 10 ppm, short-term exposure limit STEL: 15 ppm). Low concentrations produce a "rotten egg" odor, but high concentrations rapidly numb the olfactory nerves, leading to undetectable exposure. Its explosive limit is 3%–45.5%, combining toxicity and explosion risks.

Additionally, some metallurgical scenarios may require monitoring of oxygen (O₂) concentration anomalies (e.g., oxygen depletion in confined spaces) and nitrogen oxides (NOₓ) (irritating combustion byproducts).