Steam Purity in Heat Recovery Steam Generators

August 20, 2019

Author: E. S. Beardwood. International Water Conference 2014, Paper Number IWC 14-28. Engineers’ Society of Western Pennsylvania,

ABSTRACT: The paper will discuss the effects of impurities in HRSG boiling waters on steam purity and carryover into the steam turbine. The equation used for predicting vaporous silica carryover  and the equation used for predicting mechanical carryover of other impurities will be applied to determine for a given operating pressure and pH, the allowable impurity in the HRSG evaporator circuits. The determination of the final Total Steam Purity (TSP), which includes attemperation water, will be provided in a fashion that allows the user to assess such without interpolations of multiple graphs. This then allows for the setting of upper impurity control limit values allowable within the boiling waters of multiple drum steam generators and ease of assessment of off specification steam purity. Conditions leading to off specification steam purity will also be itemized to provide site operating personnel directions to investigate for steam purity control restoration.