Producer and derived gases – how is Mond gas generated? Identify the correct industrial method of producing Mond gas (a low-calorific-value fuel gas rich in hydrogen and nitrogen).

Introduction / Context:
Mond gas is a historical industrial fuel gas developed by Ludwig Mond for use in engines and furnaces. Understanding how different manufactured gases are produced helps differentiate their composition, calorific value, and typical applications.

Given Data / Assumptions:

• Feedstock includes low-grade or waste coal.
• Process temperature near 650°C.
• Large excess of steam with some air present.

Concept / Approach:

Mond gas production uses a gasifier where air and a substantial quantity of steam pass over incandescent low-grade coal at about 650°C. The air supplies limited combustion to maintain temperature, while steam promotes endothermic reactions producing a hydrogen- and nitrogen-rich gas with moderate carbon monoxide. The result is a low-calorific but copious gas suited for engines of the late 19th/early 20th century and for certain furnace duties.

Step-by-Step Solution:

Verification / Alternative check:

Process descriptions consistently cite the combination of air and abundant steam with waste coal around 650°C as the hallmark of Mond gas production, distinguishing it from producer gas or water gas methods.

Why Other Options Are Wrong:

Mixed air–steam blast without large steam at ~650°C describes general producer gas.Carbonisation of bituminous coal yields coke oven gas, not Mond gas.Steam over incandescent coke without air is water gas (blue gas).Electrolysis with methanation is unrelated to coal gasification.

Common Pitfalls:

Confusing Mond gas with producer or water gas; key differences are steam proportion, temperature, and nitrogen dilution.

Final Answer:

passing air and a large amount of steam over waste coal at about 650°C