Superheater is one of pressure parts in steam boiler. Superheater has some classifications. Outlet temperature in steam boiler is temperature of steam when leaves superheater that will be distributed to steam turbine. Outlet temperature in superheater is usually higher than outlet temperature in another pressure parts.
Based on use classification, process heating boiler has outlet temperature in superheater not exceed 350 C and the steam temperature is generally not adjusted. This condition is difference with power boiler, steam outlet temperature leaves superheater is usually above 400 C and need to adjust it.
Adjust steam outlet temperature in power boiler can be performed by using desuperheater or attemperator. The function is decrease outlet temperature if the temperature is higher than expected. One of methods to decrease steam temperature is using spray desuperheater. It spray water flow from feed water piping, so steam flow receive low temperature from water then decrease temperature it self. Location of spray desuperheater is usually between primary superheater and secondary superheater. Another way to adjust steam outlet temperature is maintain steam temperature control constant until load generally 70%. – 100% maximum continuous rating.
Steam temperature control can be executed by control excess air, burner management system, and flue gas circulation to gain maximum efficiency. Flue gas circulation should be controlled to give certain temperature when pass through both primary superheater and secondary superheater also ensure they had received enough heat transfer to generate expected steam outlet temperature.