ANS:B - steam heater

Sulphur is commonly melted in the sulphuric acid plant by employing a steam heater. In the sulphuric acid manufacturing process, solid sulphur is often stored and transported in solid form but needs to be melted before it can be further processed. One of the common methods for melting sulphur is by using a steam heater. In this method, high-pressure steam is passed through coils or jackets surrounding the solid sulphur, transferring heat to the sulphur and causing it to melt. Using steam as the heating medium offers several advantages:

1. Steam is readily available in the plant, often as a byproduct of other processes.
2. Steam is a relatively safe and clean heating medium.
3. Steam heaters can be designed to provide precise control over the melting process.

While other methods such as electrical heaters, direct fuel oil-fired heaters, or gas-fired furnaces can also be used to melt sulphur, steam heaters are preferred in many sulphuric acid plants due to their efficiency, safety, and environmental considerations.