Question

Which of the following are the advantages of the Open hearth process over the Bessemer process?
a.The process is very fast.
b.Steel is obtained very fast.
c.Loss of iron as slag is minimized.
d.The byproduct is useful in the industries.

Answer 1

Here given both the processes i.e. the Open Hearth Process and the Bessemer process are used for mass production of steel from pig iron. The Bessemer process was introduced before the Open Hearth process. Hence, an open-hearth process was introduced to remove the limitations and provide more advantages over the Bessemer process.

Complete step by step solution:
The Open Hearth furnace and the Bessemer furnace are one of the many furnaces that are used to remove excess impurities like carbon from pig iron for the mass production of steel.
In the Bessemer process, the pig iron is heated and obtained in molten form. Air is passed through the molten iron, which results in the oxidation of the iron as well as the impurities and thus the impurities like silicon, carbon, phosphorous are removed in the form of oxides. The average time taken to form steel from pig iron in the Bessemer process is around $\;10$ to $\;20$ minutes.
As this process is very fast, we obtain the final product very fast, but we don’t have control over the removal of impurities and how much proportion of impurities is required to be removed. The slag (the waste that is left in the furnace after the removal of steel) is also not useful.
In the Open hearth process, the scrap material containing steel is mixed with pig iron and the mixture is heated till it completely melts. In this mixture, slag-forming agents like limestone are added. The oxygen in the iron oxide reacts with the pig iron and removes the required carbon content and forms steel.
The complete Open Hearth process takes $8$ to $9$ hours. Hence, the process is very slow and the product is also obtained very slowly. But as the process is slow, it is easy to control and we can decide the number of impurities required to be removed, by which the loss of iron as slag is minimized. Also, the byproduct like natural gas and tar is obtained as slag which is useful in the industries.

Hence, the correct answer is Option $(C)$ and $(D)$.

Note :
Production of steel using Bessemer process was mainly stopped because it did not gave us control over the final chemistry of the steel as it was very fast. Also, the removal of phosphorous from the ore was not very efficient and the low phosphorous ores were very costly. Henry Bessemer, the inventor of the Bessemer process knew that using a pure oxygen blast would be more beneficial and efficient rather than using the air blast, but the technologies present in that era did not permit using pure oxygen blast.