Standard Technical Features of BTG System for Supercritical 660 ...

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Standard Technical Features of BTG System for Supercritical 660/800 MW Thermal Unitsi) Chutes between outlet of raw coal bunker shut off valves and inlet to thecoal feeders.ii) Chutes between outlet of coal feeder and inlet to the pulverizers.8.3.2 The internal diameter of coal chutes selected shall not be less than following:Coal ChuteMinimum I.D.i) Between bunker outlet gate & feeder inlet 914.4 mmii) Between feeder outlet & pulveriser inlet600 mm8.3.3 Chutes shall be made of minimum 12 mm thick SS-410 material and shall beof full welded construction.8.3.4 Provision shall be made for the insertion of poke rods in two directions at rightangles to each other on the chute at outlet of the bunker and at inlet to thefeeders.8.3.5 The chute between feeder outlet and pulverizer inlet shall have a stainless steellined hopper with suitable reinforcement.8.3.6 Permanent chutes shall be provided at the feeder floor near each feeder forunloading of coal from bunkers on trucks at ground level. Each bunker outletchute shall have arrangement for fixing a temporary chute for diversion of coalflow to the permanent emptying chute near each feeder. Two (2 nos.)temporary chute shall be provided for each steam generator for the abovepurpose. Necessary handling/ lifting arrangement and suitable platform &approach shall be provided for quick installations and removal of temporarychutes.8.3.7 Suitable indicators shall be provided in the downspout between bunker andfeeder to detect presence or flow of coal to ensure minimum seal height atinlet to RC feeder and trip the RC feeder if the level of coal tends to be belowthis seal height.8.4 Raw Coal Feeders8.4.1 Each mill shall be fed with coal by an independent coal feeder. All stipulationsof NFPA (latest edition) shall be complied for feeders. In addition, thefollowing features shall be provided:i) Feeder type Gravimetric, belt type with minimum size of 914.4mm.ii) Raw coal feeder 1.2 times the maximum capacity of coal pulverizer.iii) Environment a) Ambient temperature : 50 0 C (min.).withstand capability b) Explosion pressure : 3.5 kg/cm² (g) (min.).c) Other environmental conditions envisaged.63
Standard Technical Features of BTG System for Supercritical 660/800 MW Thermal Unitsiv) Feeder accuracy a) In-situ weighing accuracy : ± 0.5%.b) Repeatability : 0.1%.c) Shall have in-built facility for calibration.v) "No coal" flow detection to be provided to stop the feeder when no coal isdetected on the conveyor and when pluggage occur at feeder outlet. Paddletype coal alarm switch shall be provided for this purpose at the followinglocations:a) Over the feeder conveyor chain/belt : For indication of loss of coal flowto feeder.b) Near the feeder discharge : To stop the feeder in the event ofcoal pluggage at the feeder outlet.8.4.2 The feeder casing shall be designed to withstand an explosion pressure of 3.5kg/cm 2 (g).8.4.3 The feeder belt shall be of multiply reinforced rubber of single piececonstruction with arrangement for tracking and to prevent spillage.8.4.4 Width of the belt shall have sufficient margin while operating in conjunctionwith the feeder inlet opening provided.8.4.5 All RC feeder components coming in contact with coal (except belt) shall bemade of stainless steel.8.4.6 Facility for spraying water inside the casing shall be provided and provisionfor purge air to the feeder shall be made.8.4.7 The feeder control system shall be microprocessor based. Coal weighing shallbe automatic and shall include local & remote indication of rate of flow &totaliser counter.8.5 Coal Pulverizers8.5.1 Coal pulverizers shall be one of vertical spindle type classification. Thepulverisers offered can be of Bowl or Roller or Ball & Race or equivalenttype.Each pulverizer shall supply coal to only one burner elevation.8.5.2 Sizing of coal pulverisersSelection, sizing and total number of coal pulverisers to be provided for eachSteam Generator shall confirm to following stipulations:i) Number of mills for eachsteam generatorAdequate to achieve 100% TMCR for allspecified coal(s) and all operatingconditions, but not less than six (6) millsfor 660 MW unit and eight (8) mills for800 MW unit.64
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