Converter linings — basic versus acidic Bessemer (Thomas) practice In the basic Bessemer (Thomas) steelmaking process, the converter is lined with which refractory so that highly basic slags can be formed for phosphorus removal?

Introduction / Context:
The choice of converter lining is central to the chemistry of steelmaking. A basic lining withstands lime-rich slags necessary for dephosphorisation, while an acidic lining is compatible with silica-rich slags but cannot remove phosphorus efficiently.

Given Data / Assumptions:

• Process considered: basic Bessemer (Thomas).
• Target: phosphorus removal using basic slag (lime/dolomite).
• Refractory must resist chemical attack from basic oxides.

Concept / Approach:
Dolomite (CaO·MgO) baked with tar binders yields a basic refractory suitable for the Thomas converter. It tolerates high-basicity slags and supports reactions that transfer phosphorus from the metal to the slag as stable phosphates. Silica bricks, in contrast, are acid refractories and react unfavorably with basic slags, making them unsuitable for the Thomas route.

Step-by-Step Solution:
Identify need: basic lining for basic slag and P removal.Select refractory: tar-bonded burnt dolomite bricks provide the required basicity and resistance.Exclude acid refractories (silica) that hinder lime-rich slag practice.Therefore, pick “a mixture of tar and burnt dolomite bricks”.

Verification / Alternative check:
Classic steelmaking texts list Thomas converters with dolomite or magnesia-based linings for high-basicity operation.

Why Other Options Are Wrong:
Silica bricks are for acid practice; “either” ignores chemical incompatibility; “none” and “pure magnesia only” do not reflect the historical standard for Thomas converters described in many curricula.

Common Pitfalls:
Confusing basic oxygen steelmaking (modern BOF) with historical Bessemer variants; both require careful lining selection based on slag chemistry.

Final Answer:
a mixture of tar and burnt dolomite bricks