What type of refractory is commonly used around inspection and burner openings?

The correct answer indicates that plastic chrome ore is commonly used around inspection and burner openings due to its high resistance to thermal shock and its ability to withstand the intense heat produced in combustion processes. This type of refractory material has excellent structural integrity, ensuring that it maintains its shape and effectiveness even under extreme temperature fluctuations often present in burner areas.

Plastic chrome ore also has good workability, allowing it to be easily molded and applied around complex geometries of burners and inspection ports. This characteristic is crucial in ensuring that the refractory seals well and minimizes any potential for heat loss or gas leakage.

Other types of refractory materials may not provide the same combination of thermal resistance and workability required for these specific applications. For example, silica may not have the same level of durability under varying thermal conditions, and while fire clay and calcium silicate have their own properties, they may not perform as effectively around high-stress areas such as burner openings compared to plastic chrome ore.