Types of Superheater Boiler – Superheater is a subcritical boiler component that serves to heat the saturated steam, at constant working pressure, so it becomes superheated steam. In its development since the beginning of the 20th century, along with various boiler design races, some engineering experts patented the design of different superheater. Here are the types of superheater boiler, according to the patents:
1. Radiant Superheater
Radiant superheater is a superheater positioned in the boiler’s combustion chamber, so the superheater pipes instantly absorb the radiant heat from the combustion inside the furnace. In modern water-tube boilers, these superheater radiant pipes are placed hanging over the top of the boiler furnace. These pipes will absorb the second greatest heat energy, after the wall tubes (raiser/evaporator tube).
At radiant superheater, the more steam flows in the superheater pipes of radians, the steam temperature output are decreasing.
2. Convective Superheater
As the name implies, the convective superheater is the superheater pipes of the boiler which placed in the flow of the flue gases that still contain heat. These convective superheater pipes will absorb heat from combustion exhaust gases convectionally. This concept aims primarily to maximize heat absorption from combustion.
In contrast to the radian superheater, the characteristic of the convection superheater is that the more steam flows in the convection superheater pipes, the superheater steam temperature output increased.
3. Separately Fired Superheater
Separately fired superheater is a superheater that is placed separately from the main boiler, which has own separate combustion system with the main boiler. This superheater design is not like the radians or convection types that still use the combustion heat inside the furnace, but instead put additional burners in the area of superheater pipes. This type of superheater is not popularly used, and even tends to be extinct due to efficiency of combustion ratio with steam quality that is not better than other superheater types.
4. Combination Radiant and Convection Superheater
The last superheater type is the most popular, and still applied today. This superheater simultaneously combines two opposite characteristics between radiant and convection superheater, resulting in more homogeneous superheated steam temperature output in various steam flow. The graph below will explain these characteristics.
In modern subcritical boilers, the superheater component of radians is subdivided into several stages. As in the subcritical boiler diagram below for example, after passing the Primary Superheater which is a convection superheater, steam is streamed sequentially to the Platent Secondary Superheater, Intermediate Secondary Superheater, then the last is the Final Secondary Superheater. This design aims to maximize the absorption of radiant heat from combustion inside the furnace.