Abstract: A method for improving pulp mill steam cycle efficiency includes the steps of providing at least one deaerator tank having a first pressure, and lowering the pressure of said deaerator tank to a second pressure. Feedwater is supplied to a pre-economizer, where it is heated. The water is then delivered to at least one feedwater heater, where it is heated. The water is then delivered to an economizer. By this method boiler steam rate is increased while boiler efficiency is maintained and turbine extraction for deaerator and feedwater heating is minimized.

Abstract: An enhanced steam cycle utilizing a dual pressure recovery boiler with reheat. A dual pressure designed recovery boiler furnace is provided with a lower furnace and an upper furnace. The lower furnace is operated at a lower temperature to prevent or reduce corrosion of the lower furnace wall tubes. The lower furnace can be either a low pressure natural circulation steam generating (drum) system or economizer. The upper furnace operates as a high pressure natural circulation steam generating (drum) system, or as a once-through supercritical steam generating system at higher temperatures and pressures permitting implementation of higher efficiency reheat steam cycles.

Abstract: A dual-path parallel superheater includes a drum for delivering steam, a steam receiving apparatus opposite the drum for receiving steam, a first surface and a second which receive steam from the drum to provide first and second paths for superheating the steam before delivering it to the steam receiving apparatus. There are also spray attemperators along the first and second paths.

Abstract: A method for improving pulp mill steam cycle efficiency includes the steps of providing at least one deaerator tank having a first pressure, and lowering the pressure of said deaerator tank to a second pressure. Feedwater is supplied to a pre-economizer, where it is heated. The water is then delivered to at least one feedwater heater, where it is heated. The water is then delivered to an economizer. By this method boiler steam rate is increased while boiler efficiency is maintained and turbine extraction for deaerator and feedwater heating is minimized.

Abstract: An enhanced steam cycle utilizing a dual pressure recovery boiler with reheat allows a large increase in electrical generation with various turbine cycles while overcoming traditional lower furnace material limitations. A dual pressure designed recovery boiler furnace is provided with a lower furnace and an upper furnace. The lower furnace is operated at a lower temperature to prevent or reduce corrosion of the lower furnace wall tubes caused by the reducing environment. The lower furnace can be either a low pressure natural circulation steam generating (drum) system or economizer. Unlike the lower furnace, the upper furnace is not exposed to a reducing environment and is therefore not as susceptible to severe corrosion rates. The upper furnace is operated at higher temperatures and pressures which permit implementation of higher efficiency reheat steam cycles.