Manufacture of coke from coal – identifying the correct industrial process Coke is produced by which of the following methods?

Introduction / Context:
Coke is a high-carbon, porous solid used in metallurgical operations such as blast furnaces. Understanding how coke is manufactured distinguishes it from other solid fuels and from charcoal or briquetted products.

Given Data / Assumptions:

• Feedstock: bituminous coal (typically), although other ranks can be used.
• Process environment: absence of air (oxygen) to prevent combustion.
• Heating duration: approximately 42–48 hours in ovens (by-product or non-recovery types).

Concept / Approach:
Coking (destructive distillation) removes volatile matter by heating coal in an oxygen-free environment. Volatile by-products (tar, ammonia, gas) are distilled off, leaving a strong, carbon-rich residue called coke. The time and temperature profile are chosen to achieve the desired mechanical strength and porosity for metallurgical use.

Step-by-Step Solution:
Recognize that true coke production is carbonisation, not simple drying or pressing.Identify key condition: strong heating for many hours without air (destructive distillation).Match with the option specifying 42–48 hours in the absence of air.Select that option as the correct description of coking.

Verification / Alternative check:
By-product coke ovens (e.g., Otto-Hoffmann) operate with long coking times and recover gases and tars, aligning with the description of extended heating without oxygen.

Why Other Options Are Wrong:

• Drying and pulverising: pre-processing, not coking.
• Moulding under pressure: produces briquettes; not coke.
• Heating wood with limited air: that yields charcoal, not coke from coal.
• Catalytic hydrogenation: relates to coal liquefaction, not solid coke manufacture.

Common Pitfalls:
Confusing coke (from coal) with charcoal (from wood) or briquettes (pressed fines with binders). The defining feature of coke is destructive distillation of coal in absence of air for extended periods.

Final Answer:
when coal is strongly heated continuously for 42 to 48 hours in the absence of air in a closed vessel