High temperature sub-critical boiler with steam cooled upper furnace and start-up methods
AssigneeThe Babcock & Wilcox Company
InventorsEric L. Wells, Albert J Bennett, Jeremy L. Remus
Life of this patent
Estimating the term…
Abstract
A boiler is disclosed in which the furnace is divided into a lower furnace and an upper furnace. The lower furnace uses water-cooled membrane walls, while the upper furnace uses steam-cooled membrane walls that act as superheating surfaces. A steam-cooled circuit includes a steam separator, a primary superheater, and the steam-cooled membrane walls of the upper furnace. During start-up, a diversion path is opened that reduces dry steam flow through the primary superheater and increases dry steam flow through the steam-cooled membrane walls of the upper furnace. This protects the steam-cooled membrane walls from excessive thermal stresses during start-up.
Claims9
A boiler comprising:
- a an upper furnace including a plurality of steam-cooled membrane walls, the steam-cooled membrane walls comprising pipes sealed by membrane disposed between and connected to the pipes, the plurality of steam-cooled membrane walls including an upper furnace front wall and upper furnace side walls;
- a convection pass downstream of the upper furnace, the convection pass having steam-cooled membrane walls and extending downwards;
- wherein the upper furnace and the convection pass share a common steam-cooled membrane wall, the common steam-cooled membrane wall comprising pipes sealed by membrane disposed between and connected to the pipes, and the common steam-cooled membrane wall being both a wall of the upper furnace and a wall of the convection pass;
- a primary superheater comprising pipes without membrane, the primary superheater being disposed in the convection pass;
- a secondary superheater disposed in the upper furnace;
- a steam separator having a dry steam outlet;
- running sequentially from the dry steam outlet to the primary superheater, through the common steam-cooled membrane wall and the upper furnace front wall, to the upper furnace side walls, and to the secondary superheater;
- startup control circuitry configured to (i) reduce flow to the primary superheater and (ii) divert flow from the dry steam outlet of the steam separator to the steam-cooled membrane walls of the upper furnace through a valved diversion path that bypasses the primary superheater.
A boiler, comprising:
- a an upper furnace;
- a convection pass downstream of the upper furnace, the convection pass extending downwards;
- wherein the upper furnace and the convection pass share a common steam-cooled membrane wall, the common steam-cooled membrane wall comprising pipes sealed by membrane disposed between and connected to the pipes, and the common steam-cooled membrane wall being both a wall of the upper furnace and a wall of the convection pass;
- a steam separator having a dry steam outlet;
- one or more primary superheaters comprising pipes without membrane, the one or more primary superheaters being disposed in the convection pass;
- one or more secondary superheaters comprising pipes without membrane, the one or more secondary superheaters being disposed in the upper furnace;
- a steam-cooled circuit running from the dry steam outlet to the one or more primary superheaters and subsequently to the common steam-cooled membrane wall and then to the one or more secondary superheaters, and containing one or more reduction valves between the one or more primary superheaters and the common steam-cooled membrane wall;
- a diversion path running from the dry steam outlet through one or more diversion valves to a location upstream of the common steam-cooled membrane wall and downstream of the one or more primary superheaters;
- and
- control circuitry for switching dry steam flow from the steam separator through the steam-cooled circuit or the diversion path.
Dependencies are inferred from the claim text.