Posted By: Vivek Gharote

June 18, 2016
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Overview

The following is a general description of a 270 MW subcritical, reheat steam generator of capacity 865 TPH at BMCR. The steam generator is a radiant reheat, natural circulation, single drum, semi outdoor type unit, designed for 100% coal firing which is the principal fuel. The complete furnace section is of welded wall type, arranged as a gas and pressure tight envelope. The extended side wall section (where the reheaters are located) is also covered with water cooled section. The circulation system is complete with the six number of unheated down comers, supply and riser piping. The superheated steam system has mainly three sections. The low temperature superheater section (arranged in the second pass of the unit), the radiant platen superheater (arranged at the outlet section of the furnace) and the final superheater (arranged after the reheater). Two number desuperheaters have been provided in between the LTSH and the platen superheater for controlling the superheated steam temperature. The complete second pass of the boiler (upto the economizer) has been covered with the steam cooled superheater wall sections. The complete reheater has been arranged in one section in the horizontal pass of boiler in between the radiant platen superheater and the final superheater section. Two number reheater desuperheaters have also been envisaged in the cold reheat steam piping at the inlet of the reheater. To minimise unbalance in Reheater outlet temperature, two nos. reheater outlet headers have been provided. The location and selection of the superheater and the reheater sections have been so chosen that the rated temperatures of superheat and reheat are anticipated to be achieved from 60% TMCR to 100% BMCR load of the boiler. The steam generator is also capable of operating on sliding pressure mode. The boiler includes bare tube economizer made of seamless steel tubes arranged in between the LTSH section and the regenerative airpreheaters. The boiler has two number regenerative air pre-heaters of tri-sector type, as the last stage of heat recovery. The tri-sector air-heater has separate sections for heating the primary air (required for the pulverisers) and the secondary air, with the flue gases. The fuel preparation section has primarily six numbers Bowl Mills XRP 943. Each mill has got separate raw coal feeder. The pulverized fuel from top of mill is taken through pulverized fuel piping, one each to the four corners of the furnace. The burner wind box section is located in the four corners of the furnace and arranged for tilting tangential firing. The complete boiler is of top supported type and is provided with all the required structural supporting steel work, galleries and staircases. The boiler has two numbers radial primary air fans and two numbers forced draught fans of axial reaction type for supplying the required primary/secondary air for the boiler. The dust collection system for the boiler includes four numbers of electrostatic precipitators. The boiler is equipped with two numbers of radial ID fans with VFD, arranged after the dust collecting system, The complete integral piping, valves & fittings, all air and gas ducting with dampers/gates are provided. Necessary refractory materials are also provided; the details of the various sections of the boiler are elaborated in the following pages. Layout The boiler and auxiliaries layout is of "Cold Primary Air System” with Rear Mill Arrangement. The arrangement is such that the boiler with furnace and second-¬pass with the regenerative tri-sector air heater, followed by Bowl mill bay, ESP, ID fan and the common stack. There are two cold primary fans. The suction of the fans is from the atmosphere and the cold air is discharged into the cold air header and further into the PA section of the trisector Air Preheater. The hot air goes to the Hot primary air header. The coal mill is supplied hot air through the hot primary air header and cold air through the cold primary air header. The two FD Fans suck the air from atmosphere and it is discharged into the SA Section of the Trisector Air Heater. The heated air is supplied to the windbox. The pulverized coal & air mixture from the coal mill outlet goes to the combustion chamber through the coal pipes. The ID Fans are located just before the Chimney and after the ESP.

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vinayreddy

February 23, 2018
What is exit temperature through chimney
64x64

vinayreddy

May 7, 2018
What is exit temperature through chimney
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