Heat recovery steam generator system (HRSG) consists of an important part of combined cycle power generation plants. That are being regarded as the 21st century for their high power generation efficiency and environmental friendliness enabled by reduced emission of CO2. Babcock-Hitachi K.K. is pursuing the adoption of once through type HRSG as well. HRSG generates steam by use of exhaust heat from gas turbine and feed it to steam turbine. Babcock-Hitachi K.K. offers HRSG of various capacities to suit the size of a given gas turbine. Customers can also select a vertical or horizontal HRSG depending on the space available.