Start-up system for once-through boilers

摘要

A start-up system for once-through boilers including the reduction of minimum flow during start-up to 15% full load by the use of multi-lead internal ribbed tubing to the enclosure tubes in the high heat input zones, the use of a variable pressure by-pass stop valve in the main flow path, a pressure reducing means in the by-pass system and two steam spray attemperators from the flash tank or separators. The first steam attemperation is to the outlet of the secondary superheater and the second to the outlet of the reheater.