Fuels and by-product gases (coke oven gas): Approximately what percentage by volume of hydrogen is present in typical coke oven gas leaving the recovery system?

Introduction:
Coke oven gas (COG) is a valuable by-product from the carbonization of coal in metallurgical coke ovens. It contains hydrogen, methane, carbon monoxide, carbon dioxide, nitrogen, and light hydrocarbons. Knowing the hydrogen content is important for calorific value estimation, gas cleaning design, and as a feed for synthesis operations.

Given Data / Assumptions:

• Typical, cleaned coke oven gas composition after tar and ammonia removal.
• Percentages are approximate volumetric percentages.
• Plant-to-plant variability exists, but standard textbook values are acceptable.

Concept / Approach:
Standard compositions show hydrogen as the major component of COG. Typical ranges are roughly: H2 (50–60%), CH4 (25–30%), CO (5–10%), CO2 (1–3%), N2 and others (balance). Selecting a representative value within the standard range ensures accurate preliminary design calculations and energy balances.

Step-by-Step Solution:
Identify the dominant constituent of COG: hydrogen.Recall the common textbook value: about 55–60% by volume.Choose the nearest offered value in the list: 58%.

Verification / Alternative check:
Plant data sheets for coke ovens and fuel system references typically quote hydrogen near 55–60% vol., validating the selection of 58% as a representative value.

Why Other Options Are Wrong:

• 4% or 22%: Far below typical hydrogen content; would imply an atypical gas.
• 84%: Too high; not consistent with the presence of methane and carbon oxides.
• 35%: Still well below the usual range.

Common Pitfalls:
Confusing COG with blast furnace gas (which is CO/CO2 rich and much lower in H2) or with producer gas. Each process gas has a distinct signature composition and calorific value.

Final Answer:
58