Process Steam and its use in a Steel Plant...

Process Steam and its use in a Steel Plant Process steam is the general term used for steam which is used in process applications such as a source of energy for process heating, process cooling, pressure control and mechanical drives among others. Process steam is a popular mode of conveying energy and may come into contact with the final process or product. Like compressed air, steam is often thought of as a utility which is often generated at a central location and then distributed to various points-of-use throughout the steel plant. At atmospheric pressure the saturation temperature is 100 deg C. However, if the pressure is increased, this allows the addition of more heat and an increase in temperature without a change of phase. Therefore, increasing the pressure effectively increases both the enthalpy of water, and the saturation temperature. Water and steam can coexist at any pressure, both being at the saturation temperature. Steam at a condition above the saturation condition is known as superheated steam. Temperature above saturation temperature is called the degree of superheat of the steam and water at a condition below the saturation condition is called sub-saturated water. Steam used as process steam is usually of the following types. (Fig 1) Saturated steam – Steam is said to be ‘saturated’ with energy at a given and constant pressure when the addition of more heat to the generation system results in more steam, but no rise in steam temperature. In this state, the steam cannot hold more heat energy in a given volume unless pressure is allowed to rise. Dry steam – It is the steam that contains 100 % of water vapour in the gas phase. Dry saturated steam – Achieving the above states of dry and saturated steam simultaneously...