PDF《1,050-MW Coal-Fired Boiler》

s dynamic response is improved. Furthermore, a three- stage superheater spray system was used to control the temperature of the main flow of steam, while gas- recirculation and gas-biasing dampers were installed to overcome the performance differences encountered in the firing of various imported coals. Use of High-Strength Materials When high-level steam conditions are selected, it is essential to use high-strength materials in order to reduce the thicknesses of the walls of parts under pressure, resulting in low level of thermal stress and small pressure drops. Two austenitic steels, SUS304J1HTB (18Cr-9Ni 3Cu-Nb-N) and SUS321J1HTB (18Cr-10Ni-Ti-Nb), both of which have very high levels of creep strength in the high-temperature region, were selected for use in the pendant superheaters and reheaters. The performance of these materials had been fully confirmed by our earlier experiences with 600?C-level utility boilers. Reliable ferritic piping of STPA29 (9Cr-1.8W) and SUS410J3TP (11Cr-2W-0.4Mo) was selected for the superheater headers. By employing these materials, wall thickness in the high-temperature zone is kept within a similar Fig. 2― Tachibana-Wan Thermal Power Station. The No.

2 unit is at right. TABLE 1. Main Specifications of the Boiler Babcock-Hitachi supercritical sliding-pressure-operation Benson boiler Water-fuel ratio control and three-stage spray attemperation Parallel gas dampering and intermediate spray attemperation 3,000 t/h 2,490 t/h 25.0 MPa (g) 600?C 610?C 288?C Pulverized-coal fired Balanced draught system 35% ECR C MCR 35% ECR C MCR Boiler type Steam flow Main Reheat Main Main Reheat Main Reheat Main Reheat Steam pressure Steam temperature Economizer inlet: feed-water temperature MCR Combustion system Draught system Steam-temperature control system Steam-temperature control range Item Specifications MCR:maximum continuous rating ECR: economical continuous rating Experiences in Designing and Operating the Latest 1,050-MW Coal-Fired Boiler

102 range to that seen in conventional boilers.The strengths of various ferritic steels are compared in Fig. 4. Combustion System For environmental protection, the Hitachi NR2 burner has been applied to achieve low levels of emission of NOx (oxides of nitrogen) and high levels of combustion efficiency. Following on from the development of Hitachi'

s NR burner in which an innovative concept of in-flame NOx reduction is applied, Babcock-Hitachi K.K. has developed the NR2 burner. This burner features a strengthened flame in terms of high-temperature reduction and achieved extremely low levels of NOx emission and high levels of combustion efficiency4). The Hitachi NR2 burner is based on an improved in-flame NOx-reduction technology, which incorporates two novel devices: a pulverized-coal (PC) concentrator and a space creator. The configuration of the burner is shown in Fig. 5. This burner enables a Fig. 3― Technologies Applied in the Tachibana-Wan No.

2 Boiler. State-of the-art technologies of not only in terms of combustion technologies and other items, as well as in the steam parameters are incorporated in the design. Fig. 4― Allowable-Stress Data on High-Strength Ferritic Steels. STPA29 and SUS410J3TP are notably strong in the high- temperature region. Fig. 5― Configuration of Hitachi NR2 Burners. The pulverized-coal concentrator and space creator accelerate high-temperature in-flame NOx reduction. High-strength ferritic steel piping Multi-stage superheater spray systems Two large-capacity steam-water separators High-strength austenitic steel tubes Spirally wound water-wall of multi-ribbed tubes NO ports are provided for two-stage combustion Large-capacity low-NOx Hitachi NR2- burners Large-capacity MPS-300 pulverizers Temperature (?C) Allowable stress (MPa)