Patent ID: 7243618

Claim:
A steam generator, comprising: a steam separating drum having a drum water inlet and a drum steam outlet, said drum steam outlet operating at a first pressure; at least one evaporator including at least two evaporator sections, each of said evaporator sections including a plurality of heat-absorbing steam generating tubes connected in parallel; at least one of said evaporator sections comprising a natural circulation section, which receives water from said drum and outputs a steam water mixture into said drum; at least another of said evaporator sections comprising a once-through section, having an evaporator inlet and an evaporator outlet that outputs steam at said first pressure; a feedwater pump having an outlet that splits into at least a first feed line which feeds the drum and at least a second feed line which feeds the once-through evaporator section; and a control system including at least two feedwater control valves, one of said feedwater control valves in said first feed line, controlling the flow of water from said feedwater pump to said drum water inlet, and the other of said feedwater control valves in said second feed line, independently controlling the flow of water from said feedwater pump to said evaporator inlet for said once-through section.