A preheating system for preheating fluid medium to be fed into the HRSG is disclosed. The system includes a feed line and a recirculation line. The feed line is adapted to feed the fluid medium to a Low Pressure Economizer (LPE) of the HRSG. The feed line is adapted to be adjoined to an inlet of the LPE, and an outlet of the LPE enables therefrom the flow of the fluid medium in further portion of the HRSG. The recirculation line is adapted to be connected between the outlet and the inlet of the LPE, in parallel to LPE to recirculate the fluid medium to the LPE. A particular method of preheating using such a system is equally disclosed.

A method for heat integration between a chemical synthesis plant that runs an exothermic reaction and (ii) and a partner plant that generates a working fluid such as steam (e.g., runs a power cycle). The present disclosure describes both internal and external heat integration. Internal heat integration may provide heat from the exothermic reaction (e.g., from methanol synthesis) to a reboiler associated with a distillation column of the chemical synthesis plant. External heat integration may use heat from the exothermic reaction to preheat a condensed water stream (which stream is downstream from the turbine and condenser of the power cycle). Such reduces the need for bleed off the turbine to preheat condensed water as part of the power cycle. A bleed off the turbine provides heat to the reboiler associated with the distillation column of the chemical synthesis plant. Heat integration provides overall improved energy use within both plants.

The invention relates generally to methods and apparatus for start-up and control of liquid salt energy storage combined cycle systems.