Modern steam generators typically include a radiant section and a convection section. Due to differing performance requirements of the radiant and convection sections, the radiant section often has a round cross-section, while the convection section often has a rectangular cross-section. Previous designs utilized a target wall to affect the transition. An angled transition section is disclosed herein that substantially eliminates the target wall and/or the reverse target and provides a corresponding improvement in steam generator efficiency.

Sulfur trioxide is produced from a feed stream comprising sulfur-containing compounds and dissolved metals, such as alkali metals, in a plant comprising an incineration furnace, a waste heat boiler, a dilution air heater, a dust removal absorber and an SO.sub.2 converter. The plant may further comprise a sulfuric acid condenser for the production of sulfuric acid.

Sulfur trioxide is produced from a feed stream comprising sulfur-containing compounds and dissolved metals, such as alkali metals, in a plant comprising an incineration furnace, a waste heat boiler, a dilution air heater, a dust removal absorber and an SO.sub.2 converter. The plant may further comprise a sulfuric acid condenser for the production of sulfuric acid.

Disclosed herein is a once-through evaporator comprising an inlet manifold; one or more inlet headers in fluid communication with the inlet manifold; one or more tube stacks, where each tube stack comprises one or more inclined evaporator tubes; the one or more tube stacks being in fluid communication with the one or more inlet headers; where the inclined tubes are inclined at an angle of less than 90 degrees or greater than 90 degrees to a vertical; one or more outlet headers in fluid communication with one or more tube stacks; and an outlet manifold in fluid communication with the one or more outlet headers.

Disclosed herein is a once-through evaporator comprising an inlet manifold; one or more inlet headers in fluid communication with the inlet manifold; one or more tube stacks, where each tube stack comprises one or more inclined evaporator tubes; the one or more tube stacks being in fluid communication with the one or more inlet headers; where the inclined tubes are inclined at an angle of less than 90 degrees or greater than 90 degrees to a vertical; one or more outlet headers in fluid communication with one or more tube stacks; and an outlet manifold in fluid communication with the one or more outlet headers.

A heat recovery steam generator (HRSG) includes a first casing having an interior enclosing at least one duct for gas to flow therein along a gas flow axis. Each duct is defined by duct defining members that are spaced apart from each other and extend into the interior of the first casing. A plurality of stiffening members are elongated along the gas flow axis. Each of the stiffening members are positioned between two of the duct defining members. The stiffening members and duct defining members have a substantially similar coefficient of thermal expansion.

A heat recovery steam generator (HRSG) includes a first casing having an interior enclosing at least one duct for gas to flow therein along a gas flow axis. Each duct is defined by duct defining members that are spaced apart from each other and extend into the interior of the first casing. A plurality of stiffening members are elongated along the gas flow axis. Each of the stiffening members are positioned between two of the duct defining members. The stiffening members and duct defining members have a substantially similar coefficient of thermal expansion.

An evaporation cycle of a natural circulation steam generator. An evaporator is in flow connection with a downcomer pipe and includes a first evaporative section and a second evaporative section connected in parallel with the first evaporative section and arranged at a higher level than the first evaporative section. The evaporator cycle is not associated with another external source of motive force than heat from the gas flow to assist the flow of the water in the evaporator, and the evaporator has a vertically extending outlet collector for collecting the steam and water from the first and second evaporative sections to the riser pipe. The outlet collector includes a lower portion and an upper portion above the lower portion. The first evaporative section is in direct flow connection with the lower portion and the second evaporative section is in direct flow connection with the upper portion.

An evaporation cycle of a natural circulation steam generator. An evaporator is in flow connection with a downcomer pipe and includes a first evaporative section and a second evaporative section connected in parallel with the first evaporative section and arranged at a higher level than the first evaporative section. The evaporator cycle is not associated with another external source of motive force than heat from the gas flow to assist the flow of the water in the evaporator, and the evaporator has a vertically extending outlet collector for collecting the steam and water from the first and second evaporative sections to the riser pipe. The outlet collector includes a lower portion and an upper portion above the lower portion. The first evaporative section is in direct flow connection with the lower portion and the second evaporative section is in direct flow connection with the upper portion.

Modern steam generators typically include a radiant section and a convection section. Due to differing performance requirements of the radiant and convection sections, the radiant section often has a round cross-section, while the convection section often has a rectangular cross-section. Previous designs utilized a target wall to affect the transition. An angled transition section is disclosed herein that substantially eliminates the target wall and/or the reverse target and provides a corresponding improvement in steam generator efficiency.