Circuit assembly for once-through steam generators

A once-through boiler comprising:

• (a) A plurality of circuit assemblies, each said circuit assembly comprising:
• a plurality of vertical heat transfer tubes, a plurality of crossover tubes, and a plurality of U-bend tubes, welded together into at least one independent once-through steam generating serpentine flow path, means for installing said heat transfer tubes horizontally into individual said circuit assemblies in the shop, means for supporting said circuit assembly by hanging, means for transferring the weight of said circuit assembly to the ground, means for spacing said heat transfer tubes for thermal effectiveness, means for sealing said circuit assembly to prevent blowby leakage, means for accommodating thermal expansion of said circuit assembly, means for damping tube vibration, means for dewatering said circuit assemblies, means for repairing said circuit assembly, means for transporting said circuit assemblies horizontally to the field, means for connecting said circuit assemblies in series in the field and thereby providing said boiler with individual preheater, vaporizer and superheater in each once-through flow path, means for interspersing different independent steam pressure flow paths to provide high thermal performance to the boiler with multiple pressure, whereby said boilers with long horizontal gas flow paths, and with a plurality of different steam generating flow paths, can be constructed from said circuit assemblies having widths narrow enough to be transported,
• (b) a plurality of circuit sub-modules comprising:
• a plurality of said circuit assemblies stacked in parallel with a plurality of connection weld joints to at least one high pressure feedwater header, and at least one high pressure steam header,
• (c) a boiler casing comprising:
• a gas inlet duct, a gastight shell structure around said circuit sub-modules, a boiler exhaust stack, an insulation system, a plurality of blowby seals, whereby hot gas flow is sealed and directed to flow across said circuit assemblies, and whereby said circuit assemblies are supported and blowby loss is minimized,
• (d) means for effecting the flow of water into said feedwater headers of said circuit assemblies, whereby water as it flows through said circuit assemblies is heated, evaporated to steam by hot gases flowing horizontally across said heat transfer tubes that are vertically positioned in the gas flow path that is directed by said boiler casing from a gas turbine heat source,
• (e) means for distributing water flow uniformly to the feedwater inlet end of said circuit assemblies to stabilize flow and provide uniform outlet steam temperature from each independent flow path in said circuit assembly, said means for distributing water comprising a flow resistor at the feedwater inlet end of each flow path in said circuit assembly,
• whereby any size of the boiler can be constructed from said circuit assemblies with most of the welds completed in the shop and a plurality of different pressures can be provided to the boiler and,
• whereby said circuit asssemblies with long tubes can be transported to the field horizontally for erection into a vertical operating position.