Chemical Engineering Basics MCQ Questions & Answers | Chemical Engineering

The volume of blast furnace slag is about 3 times the volume of hot metal (pig iron) of the same weight.

In the blast furnace process, iron ore (mainly iron oxide) is reduced to produce pig iron, and the impurities in the ore (like silica and alumina) combine with flux (like limestone) to form slag. The slag is less dense than pig iron, which leads to it occupying more volume for the same weight. Typically, for every ton of pig iron produced, approximately 3 tons of blast furnace slag are generated, meaning the volume of slag is about three times that of the hot metal.

Option A: 1.5 This option is incorrect. The volume of slag is far more than 1.5 times the volume of hot metal. The ratio is much higher.

Option C: 5 This option is incorrect. The volume of slag is not five times that of the hot metal. A ratio of 3:1 is more common and realistic for most blast furnace operations.

Option D: 7 This option is incorrect. Although the volume of slag can vary based on the specific process and furnace conditions, the typical ratio is about 3:1, not 7:1.

Therefore, the correct answer is Option B: 3, which is the typical volume ratio of blast furnace slag to pig iron.

Radiation: The heat transfer by radiation is independent of surface texture (like cavities or pock-marks) and relies on the emissivity and temperature of the surface. Hence, the heat transfer by radiation does not increase due to the presence of cavities.

Convection: Cavities on a heat transfer surface can enhance convection by disturbing the boundary layer, promoting turbulence and fluid mixing. This increases the rate of convective heat transfer.

Nucleate Boiling: Cavities act as nucleation sites, facilitating bubble formation and improving heat transfer during boiling.

Conduction: Surface irregularities could affect conduction slightly but are less significant in comparison to the other modes of heat transfer. Thus, Option C: Radiation is the correct answer because it remains unaffected, while other modes of heat transfer may increase with a pock-marked surface.