Design Technology for Supercritical Sliding Pressure Operation Vertical Water Wall Boilers - First report: History of Practical Application and Introduction of Enhanced Rifled Tube -
A supercritical sliding pressure operation once‐through boiler with vertical water wall tubes uses high‐cooling‐capability rifled tubes for its furnace walls. This type of boiler consists of vertically arranged tubes, instead of a complex spirally wound structure, so that it can improve performance, reliability and economic efficiency. Mitsubishi Heavy Industries, Ltd. (MHI) started to employ this type of boiler for commercial operation at Unit 1 (700 MW) of the Matsuura Power Plant of Kyushu Electric Power Co., Inc. as the world's first application in 1989, as well as in Units 1 and 2 (700 MW each) in the Kawagoe Thermal Power Plant of Chubu Electric Power Co., Inc. in 1989 and 1990. Since then, MHI has provided approximately 50 units of this type 10 domestically and 40 overseas including licensing of the technology. The superiority of this type of boiler has been universally acknowledged, and in recent years, several boiler manufacturers have started to introduce this type. It has been verified that applying high‐cooling‐capability rifled tubes to the boiler furnace wall enhances the self‐correcting action relaxing the steam temperature imbalance across the furnace water wall outlet section, which is caused by inevitable variations of heat absorption in each part of the water walls. This preferable action encourages not only load follow‐up performance, but also durability against the upgraded steam condition, the former of which is required by expanding the introduction of renewable energy and the latter required for the reduction of greenhouse gas emissions. This report explains the design optimization of the furnace water wall system reflecting operational data, advanced technological methods, and the operating guidelines established based on continuous research and development work on heat transfer and hydrodynamic characteristics for furnace water walls with rifled tubes. Also, this report partially introduces the higher‐performance vertical water wall tube boiler using new rifled tubes, which will be detailed in the upcoming document (second report).
