Combustion handling of pitch from coal tar: Why is pitch always mixed with creosote oil before burning in a pressure-atomized burner or transferring through pipelines?

Introduction / Context:
Pitch is a high-viscosity, high-softening-point residue from coal tar distillation. Efficient handling and combustion require suitable rheology for pumping and atomization.

Given Data / Assumptions:

• Pitch alone is too viscous at moderate temperatures.
• Creosote oil is a lighter coal-tar distillate.
• Goal: enable pipeline transfer and burner atomization without extreme heating.

Concept / Approach:
Blending pitch with creosote oil lowers viscosity and softening point. This improves pumpability, reduces line pressure drop, and ensures better atomization and combustion stability in burners. Calorific value of pitch is not inherently “very low”; the key issue is fluidity and handling.

Step-by-Step Solution:
Identify limiting property → very high viscosity of pitch.Add suitable cutter stock → creosote oil to reduce viscosity.Result → acceptable flow through pipelines and reliable atomization → cleaner, steadier combustion.

Verification / Alternative check:
Fuel oil handling practice commonly uses “cutter stocks” to meet viscosity specs for burners and transfer systems.

Why Other Options Are Wrong:

• (a) Pitch has substantial calorific value; viscosity, not energy content, is the problem.
• (b) Neutralization of residual acids is not the main reason for blending.
• (d) Only viscosity reduction is the primary, decisive reason.
• (e) Increasing ash is undesirable, not a target.

Common Pitfalls:
Confusing fuel quality (calorific value) with rheology; atomization depends on viscosity, temperature, and nozzle design.

Final Answer:
Because creosote oil reduces viscosity, providing fluidity and enabling pumping/atomization at practical pressure drop