Coal carbonisation — In low-temperature carbonisation of coal, what is the typical yield of coke oven gas, expressed approximately in normal cubic metres (Nm³) per ton of dry coal?

Introduction:
Coke oven gas yield is a key performance indicator in coal carbonisation. Low-temperature carbonisation (about 500–700 °C) aims to produce smokeless domestic coke and by-products such as tar and gas. Understanding the approximate gas yield helps with capacity planning for gas cleaning, storage, and use as a fuel.

Given Data / Assumptions:

• Process: low-temperature carbonisation of dry coal.
• Quantity sought: approximate coke oven gas yield in Nm³ per ton of dry coal.
• Normal conditions indicate volume at standard temperature and pressure.

Concept / Approach:
At low temperatures, coal devolatilises gently, favoring tar production and yielding a moderate quantity of gas. In contrast, high-temperature carbonisation (about 900–1200 °C) maximises metallurgical coke strength and tends to yield substantially more gas but less tar. Typical reference values place low-temperature gas yield near the lower hundreds of Nm³/ton.

Step-by-Step Solution:
Identify operating regime: low-temperature (not metallurgical/high-temperature) carbonisation.Recall typical ranges: gas yield for low-temperature carbonisation ≈ 120–200 Nm³/ton.Choose the nearest listed figure within the plausible range: 160 Nm³/ton.

Verification / Alternative check:
Process handbooks typically report that high-temperature carbonisation produces higher gas volumes (several hundred Nm³/ton), confirming that figures like 500 or 750 Nm³/ton are characteristic of higher-temperature operations rather than low-temperature practice.

Why Other Options Are Wrong:

• 60: Too low for typical low-temperature practice.
• 500 and 750: More representative of high-temperature or different processes.
• 300: Still on the high side for low-temperature carbonisation.

Common Pitfalls:
Confusing low-temperature with high-temperature yields; ignoring that “normal” cubic metres refer to standard conditions (important for fair comparison).

Final Answer:
160