Recovery Boiler Reheat Steam Cycle

摘要

High electricity costs and incentives for renewable energy are driving pulp companies to improve the power generating potential of their mills. In Japan, where energy costs have traditionally been high, recovery boilers have been built that run superheat cycles with pressures and temperatures as high as 135 bar (1950 psi) and 515C (960F). In North America there are boilers that have operating conditions of 107 bar (1550 psi) 496C (925F) but approximately 60% of the recovery boilers in North America operate at or below 62 bar (900 psig).Since the 1960s electrical generating utilities have operated natural circulation boilers in excess of 180 bar (2600 psig) at the superheater outlet. These utility boilers operate with superheater and reheater temperatures from 538C (1000F) to 568C (1055F). The reheat cycle greatly improves thermal efficiency of the power generation cycle. Utility boiler experience applied to a pulp mill steam cycle would greatly improve the electrical power generation potential of a pulp mill steam cycle. Babcock & Wilcox power generation group has made developments in the recovery boiler design that will allow a recovery boiler to operate at utility pressures and with reheat steam cycles.