Hydrogen from coke-oven gas (as practiced historically at Rourkela): which commercial separation method is used at scale to recover H2 from the coke-oven gas stream?

Introduction / Context:
Coke-oven gas is a by-product gas containing hydrogen, methane, CO, nitrogen, and other components. In integrated steel-fertilizer complexes, part of the hydrogen requirement for ammonia can be met by recovering H2 from this gas. Understanding the practical, scalable separation method is critical for appreciating legacy hydrogen sources in fertilizer plants.

Given Data / Assumptions:

• Coke-oven gas includes H2 along with permanent gases and light hydrocarbons.
• Recovery is on a commercial scale, not laboratory-scale polishing.
• Rourkela is cited as a historical example in the fertilizer context.

Concept / Approach:
Cryogenic separation exploits differing condensation/boiling points to separate hydrogen from heavier gases at very low temperatures. On large streams like coke-oven gas, cryogenic plants are industrially proven. Alternatives listed here are unsuitable at scale: palladium adsorption selectively allows H2 permeation but is expensive and used for ultra-pure polishing, not bulk recovery. Amine solutions (ethanolamine) remove acid gases like CO2 and H2S, not hydrogen; pyrogallol solutions absorb oxygen, not a route to bulk H2 recovery.

Step-by-Step Solution:
Identify bulk separation requirement: large throughput H2 recovery.Select technology that scales: cryogenic fractionation of light gas mixtures.Exclude chemisorption/absorption routes that target CO2/O2 rather than H2.Conclude cryogenic operations are the correct industrial method.

Verification / Alternative check:
Historic flowsheets show cryogenic units paired with purification (e.g., small methanation/PSA polishing) in steel-fertilizer complexes using coke-oven gas hydrogen.

Why Other Options Are Wrong:
Palladium adsorption: niche, high cost, suited to purification not bulk separation.Amine/pyrogallol absorption: remove acid gases or oxygen, not hydrogen.

Common Pitfalls:
Confusing H2 purification with H2 recovery; mixing up acid gas scrubbing with hydrogen separation.

Final Answer:
Cryogenic operations (low-temperature cooling)