MANUSCRIPT TITLE:Supercritical Boilers : ComparingVertical Tube Low Mass Flux and SpiralFurnace Designs

摘要

This paper attempts to provide techno-economic data for different types of once throughrnboiler circuitry design. Three furnace designs discussed in this paper include:rn1. Vertical tube furnaces using smooth (and ribbed) bore tubing, and having high massrnfluxes. These designs, often requiring multi-pass circuitry, do not possess anyrninherent flow change ability when confronted by an increase of heat supply to anyrnindividual tube. The market for this type of design has diminished, with many ownersrnof existing units moving to refurbish these boilers.rn2. Spiral-wound furnace designs featuring support straps for mechanical integrity. Thesernboiler designs offer adequate tube protection, but have higher manufacturing andrnerection cost.rn3. Vertical, internally ribbed tube, low mass flux Benson furnaces. Mitsui Babcockrnremains the only company to have supplied and gained operational experience on arncommercial basis with this technology.rnSpiral wound once through furnace designs are widespread, and a booming market for thisrnboiler design is currently prevailing especially in China, US and Europe.rnUtilizing the 600 Mew spiral furnace once through boilers being supplied by Mitsui Babcockrnfor the Wangqu project in Shanxi Province PRC as a basis, comparisons are made with arnreplicated hypothetical boiler design employing a vertical, internally ribbed tube low massrnflux furnace.rnThe key advantages of vertical, internally ribbed tube furnaces having low mass flux are:rn? Lower water/steam pressure loss when compared to an equivalent spiral boilerrndesign, providing boiler feed pump power reduction and better thermal cyclernefficiency thereby reducing fuel consumption and emissions.rn? Reduction of boiler design, manufacturing and erection cost.rn? Opportunity to refurbish to supercritical operation existing vertical-tube furnacernwith internally smooth tubing with lower cost in respect to spiral furnace designrnalternative.rn? Opportunity to refurbish oil, gas and coal fired once through boilers improvingrntheir overall performance.rnRelative supply costs for the spiral wound and vertical- ribbed low mass furnace designs arerngiven with explanations relating to associated weights, support structure implications andrnmanufacturing / erection considerations.rnThe reduced schedule associated with the adoption of vertical tube low mass flux technologyrnwhen applied to the refurbishment of existing boilers is also noted.rnThis paper will present a detailed overview enabling decision makers to be better informedrnwith regard to the choice between spiral and vertical tube low mass flux furnace designs, andrnadditionally discusses the refurbishment of existing vertical-tube high mass flux furnaces.