Nội dung

Sumitomo Corporation for EVNGENCO1 Duyen Hai 3 Extension, 1 x 660 MWnet Power Project 1.1.3 July 7, 2014 SUPERCRITICAL SPIRAL WOUND BOILER OVERVIEW The steam generating unit described herein is a balance draft coal-fired Babcock & Wilcox (B&W) Spiral Wound Universal Pressure (SWUP™) boiler. The boiler contains a dry-bottom furnace, superheater, reheater, economizer, and air heater components. This unit is designed for both base load and variable pressure load cycling operation as well as on-off cycling operation. Figure 1 below depicts a typical B&W SWUP™ boiler. Figure 1: B&W once-through spiral wound universal pressure (SWUP™) boiler for pulverized coal firing with SCR B&W Proposal P-043049 PROPRIETARY AND CONFIDENTIAL Copyright © 2014 Babcock & Wilcox Power Generation Group, Inc. All rights reserved Page 1 of 5 Sumitomo Corporation for EVNGENCO1 Duyen Hai 3 Extension, 1 x 660 MWnet Power Project July 7, 2014 A Unique Design- Ideal for Rapid Load Changes A unique feature of the B&W SWUP™ boiler is that the furnace tubes, from the lower furnace inlet headers to a location near the furnace arch, are spiral wound around the furnace instead of vertical. In this arrangement, each tube in the furnace passes through similar heat absorbing areas, keeping heat absorption from tube to tube reasonably uniform. This, results in a reduced fluid temperature variation leaving the furnace which minimizes thermal upset that can restrain rapid load change. Additionally, the ability of this design to operate at variable load pressure is further enhanced by using a startup system with a recirculation pump (up to the once-thru point only) specifically designed for rapid startup. Furthermore, since the tubes are at an angle, there are fewer flow paths compared to vertical tube geometry which increases mass flux in the tubes. A high mass flux is desired within the tube to maintain nucleate boiling during subcritical operation and to provide enhanced cooling during supercritical operation. Fuel Flow Raw coal discharged from the feeders to the pulverizers is pulverized and transported by primary air to the burners, located on the furnace walls with opposed firing. Air Flow Air from the forced draft fans is heated in the air heaters, routed to the each section the compartmented windbox and distributed to the burners and NOx ports, if applicable, as secondary air. High pressure fans provide air from the atmosphere to a separate, primary section of the air heater. A portion of this primary air is bypassed around the primary air heater as tempering primary air. The preheated and tempering primary air are mixed in a controlled manner to obtain the desired pulverizer fuel-air mixture outlet temperature. The primary air is used to dry and transport the fuel from the pulverizer through the burners to the furnace. Gas Flow Hot flue gas from the furnace passes across the finishing banks of the superheater and reheater. Before exiting the boiler, the gas is divided into two parallel paths with one path passing over a portion of the superheater, the other a portion of the reheater. This portioning of the flue gas provides a means of steam temperature control for the unit, as flow quantities are adjusted by dampers at the boiler exit, as shown in Figure 2 below. B&W Proposal P-043049 PROPRIETARY AND CONFIDENTIAL Copyright © 2014 Babcock & Wilcox Power Generation Group, Inc. All rights reserved Page 2 of 5 Sumitomo Corporation for EVNGENCO1 Duyen Hai 3 Extension, 1 x 660 MWnet Power Project July 7, 2014 These dampers are well proven, low maintenance B&W standard design with an excellent operating record dating back to the mid 1970’s. The damper and slotted idler bearing design has even proven successful in applications with ash content in excess of 40%. This design allows for reheat steam temperature control without the use of spray and the resulting negative impact to heat rate. Reheat Path Damper Superheat Path Damper Figure 2: Gas biasing dampers on a typical Carolina-type SWUP™ boiler Attemperators are provided in the reheater and superheater systems. The reheater attemperator is designed to be used during transient loads and upset conditions, while the superheater attemperators are used to control main steam temperatures during operation. This arrangement of convection surface, attemperation and damper system provides extended capability to obtain design steam temperatures in the superheater and reheater over a broad range of loads. Gases leaving the superheater and reheater sections pass across the economizer to the air heater and then to the appropriate environmental control equipment. B&W Proposal P-043049 PROPRIETARY AND CONFIDENTIAL Copyright © 2014 Babcock & Wilcox Power Generation Group, Inc. All rights reserved Page 3 of 5 Sumitomo Corporation for EVNGENCO1 Duyen Hai 3 Extension, 1 x 660 MWnet Power Project July 7, 2014 Water and Steam Flow The actual water and steam flow path is specifically tailored for each project so it may differ slightly from the following general description. B&W optimizes the heating surface of all of the boilers that it designs, ensuring that we offer the correct arrangement for the desired requirements. The following is a typical description of the water and steam flow path for a SWUP™ boiler. Feedwater enters the bottom economizer header and passes upward through the economizer tube bank. It is then collected in the economizer outlet header and flows through the downcomer to the lower furnace area. Supply tubes are routed to the lower furnace headers, and from there the fluid passes upward through the spiral tubes to a transition section located below the furnace arch. Then the tubes are routed vertically, and the fluid passes up the vertical tubes to the upper furnace wall headers and piped to a fluid mix header. From the mix header, the fluid flows in to the vertical steam separators. During operation below the once through point (e.g. when the fluid leaving the furnace is a steam-water mixture) the steam separators separate the steam from the water. The water flows down into a collecting tank which supplies the boiler recirculation pump. The steam exits the top of the separator and flows into a header that supplies the roof tubes. The fluid then travels through the roof tubes to the rear roof header. Steam from the rear roof header passes into the support tubing located between tube rows of the primary superheater and to the convection pass enclosure rear wall headers. The fluid flows through the primary superheater support tubes and the rear wall tubes to the baffle wall header. The steam flows through the baffle tubes and is collected into the primary superheater inlet header. The steam from the rear wall tubes also flows to the convection pass enclosure front and side wall headers, through the wall tubes, to the upper baffle wall screen headers and is also collected in the primary superheater inlet header. The steam rises through the primary superheater and discharges to the outlet header, from which it flows through piping containing the first stage of spray attemperators. Partially superheated, the steam enters the platen secondary superheater and flows through it to the outlet headers. The second stage of spray attemperators is located in the pipes connecting the platen secondary superheater to the finishing portion of the secondary superheater. Note that this piping is “crossed over” to aid in the reduction of steam temperature side-to-side imbalances. Once the now superheated steam flows through this final portion to the outlet header and discharge pipes, it is directed to the high pressure section of the steam turbine. The low pressure steam from the turbine returns to the boiler for reheating. At the reheater inlet header, the steam flows through the reheater tube bank to the outlet header where it is then routed back to the intermediate pressure and then low pressure sections of the steam turbine-generator set. A typical SWUP™ convection pass can be seen in Figure 3 below. B&W Proposal P-043049 PROPRIETARY AND CONFIDENTIAL Copyright © 2014 Babcock & Wilcox Power Generation Group, Inc. All rights reserved Page 4 of 5 Sumitomo Corporation for EVNGENCO1 Duyen Hai 3 Extension, 1 x 660 MWnet Power Project July 7, 2014 Bank A) Superheater Platens B) Secondary Superheater Inlet C) Secondary Superheater Outlet D) Reheater Pendant E) Reheater Crossover F-I) Reheater Horizontal J) Primary Superheater Pendant K-M) Primary Superheater Horizontal N-P) Economizer Figure 3: Typical SWUP™ convection pass layout B&W Proposal P-043049 PROPRIETARY AND CONFIDENTIAL Copyright © 2014 Babcock & Wilcox Power Generation Group, Inc. All rights reserved Page 5 of 5