Vapor generator

Claim 1

In a ship propulsion system wherein superheated and reheated steam is selectively supplied to a forward drive turbine and only superheated steam to an astern drive turbine, the combination with the propulsion system of a vapor generator comprising: walls defining a setting; partition wall means dividing the setting into a furnace, a superheater gas pass laterally adjoining the furnace and arranged to receive all of the furnace gas outflow, a reheater gas pass, and a vertically elongated convection gas pass disposed intermediate and laterally adjoining the superheater and reheater gas passes and arranged for gas discharge through an outlet at the lower end portion of the reheater gas pass, said convection gas pass having adjacent first and second inlets at the upper end portion thereof, said first inlet being arranged to receive all of the gas outflow from the superheater gas pass; an outlet gas pass arranged to receive all of the gas outflow from the reheater gas pass; at least one bank of superheater tube banks positioned in the superheater gas pass; a plurality of fluid heating tube banks including at least one reheater tube bank positioned in the reheater gas pass, said reheater tube bank being arranged upstream gas flowwise of the remaining fluid heating tube banks in said reheater gas pass; firing means associated with said furnace to produce heating gases for flow through the setting; a forced draft fan; an air inlet duct connected to the forced draft fan for delivering combustion air to said firing means; and tempering means for introducing a low temperature gaseous fluid through the second inlet of the convection gas pass, said tempering means including a tempering duct flow-connecting the air inlet duct to the second inlet of said convection gas pass.