Choosing the Optimal Technology for Expanding the Adjustment Range of the CCGT-450 Power Unit

A method of unloading the 450 MW CCGT-unit by reducing the load of gas turbines and recovery heat boilers up to the level of the capacity limits of gas turbines and further reduce the load of the CCGT unit with steam turbine unloading: transfer of part of its HPC (high pressure cylinder) or HPC completely in the motor (low steam) mode (MM); using by-pass steam distribution high pressure steam through the discharge part of it into the steam line low-pressure and low-pressure cylinder. The features of hydrodynamic processes of the HPC compartments in the MM and the choice of the optimal cooling scheme for a group of stages operating in low-flow mode are given. Direct-flow and counter-flow schemes of cooling steam movement, their advantages and disadvantages, as well as the possibility of controlling the temperature state of the flow part of the HPC are considered. For bypass steam distribution, various options and ratios of high-pressure steam discharge are considered according to the specified scheme. It is shown that the considered method of unloading the CCGT allows to expand its adjustment range when the CCGT operates in both condensation and heating modes. An estimation of the energy efficiency of using this modes of CCGT unloading when passing through the gap of energy consumption schedules is given.