Combined Cycle Gas Turbine Unit Research Articles

A performance study of PEMS applied to the Hsinta power station of Taipower

Abstract Predictive emission monitoring systems (PEMS) have been shown to be a promising technology for calculating the emissions from gas-fired stationary sources. One of the first demonstration PEMS in Taiwan was installed and operated successfully at the Hsinta power plant of the Taiwan Power Company (Taipower) in 2000. To improve the accuracy of this PEMS model, further studies were conducted at the same combined cycle gas turbine (CCGT) unit #1 of the Hsinta power plant. To optimize the NOX PEMS model, several functions were progressively developed including a log model, a one-level linear model, a three-level linear model, a 15-variable linear model, and a 15-variable with start-up mode model. The latter gave the relative accuracies (RA) and correlation coefficients between PEMS and a continuous emission monitoring system (CEMS) in the range of 3.38–14.77% and 0.955–0.989, respectively, which fulfill the criteria of the USEPA draft on PEMS performance specifications. Similarly, this model demonstrated RAs for low, medium, high level, and a three-level average less than 20% which meet CEMS requirements set out by Taiwan EPA.

Reliability and durability from large heat recovery steam generators

Experience with heat recovery steam generators (HRSGs) designed for larger-heat-input and higher-steam conditions highlights limitations in some features of traditional designs extrapolated from smaller HRSGs that operated predominantly continuously. Many combined-cycle units may be subjected to periods of regular overnight shut-down much earlier than expected and, unless anticipated during the initial design, there will be significant adverse impact on reliability and durability. Very premature problems already experienced on large HRSG designs in combined-cycle and cogeneration applications give an early warning that more widespread problems will arise as HRSGs are subjected to more thermal cycling. Problems that arise when inadequate attention is given to transient conditions over the full range of operation of the combined-cycle gas turbine unit, including at part loads, during shut-downs and restarts from diverse pre-start conditions, are highlighted. The paper gives examples of how the damage to HRSGs during shut-down and starts can be mitigated by minor modifications and sympathetic operating procedures and suggests how prudent purchasers can enhance reliability and lower lifetime costs at a small premium in installed cost by specification of appropriate design features. Other weaknesses which cause problems for operation and maintenance are discussed.