Carbonisation of Coal – Temperature Range for Hard (Metallurgical) Coke Hard coke is obtained by high-temperature carbonisation of coal, typically in the range of about 900° to 1100°C.

Introduction / Context:
Coking converts coal into a carbon-rich, porous solid used in metallurgical furnaces. The temperature regime of carbonisation determines the properties of the product, including strength, porosity, and volatile content.

Given Data / Assumptions:

• Carbonisation in the absence of air (destructive distillation).
• Controlled heating with by-product recovery in modern coke ovens.
• Distinct low- and high-temperature regimes produce different coke qualities.

Concept / Approach:

Low-temperature carbonisation (about 500°–700°C) yields softer, smokeless fuels with higher volatile content. High-temperature carbonisation (about 900°–1100°C) drives off volatiles more completely and sinters the carbon matrix, forming hard, strong metallurgical coke required for blast furnaces.

Step-by-Step Solution:

Verification / Alternative check:

Industrial practice and materials handbooks consistently cite ~1000°C as a representative temperature for strong coke production.

Why Other Options Are Wrong:

Lower ranges leave too much volatile matter and inadequate structure; significantly higher ranges are uncommon and risk excessive energy input and structural degradation.

Common Pitfalls:

Confusing soft (domestic) coke with metallurgical coke; overlooking the role of heating rate and coal blend on final properties.

Final Answer:

900° to 1100°C