Steam Generators

B&W provides both designs for new installations and as replacement units:

B&W once-through steam generator (OTSG)
The OTSG is a vertical shell counterflow straight-tube heat exchanger design which directly generates superheated steam as the feedwater flows through the steam generator in a single pass.
Recirculating steam generator (RSG)
In a RSG, only part of the feedwater is converted to steam as the water passes through the unit. After the steam is separated from the water, the steam is sent to the turbine for power generation while the water is returned to the tube bundle for additional steam generation.

These steam generator designs use a vertical shell and an inverted U-tube heat exchanger bundle, with steam separation equipment located inside the top shell of the RSG.