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

Standard Technical Features of BTG System for Supercritical 660 ... 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 Unitsiv) Fan BalancingThe fans shall be statically and dynamically balanced before shipment andbalancing of each fan shall be checked and adjusted at site, if necessary.7.1.5 Flow measuring devicesi) The draft plant shall include flow measuring devices in the air system fortotal air flow measurements and control with adequate number of tappingpoints.ii) Three independent pairs of tapping points with the necessary isolatingvalves shall be provided for control, measurement and test.iii) Two nos. duplex temperature element with thermowells for temperaturecompensation shall be provided.iv) Fan inlet flow measurement shall be provided using fan inlet elbow.However, if such an arrangement is not possible, flow element (venturi/aerofoil system) shall be provided with three pair of tapping points atsuction of each FD Fan.7.2 Duct Work7.2.1 Duct work sizing criteriai) Allowable velocities in the duct work shall be as below.a) Maximum velocity for cold air and hot air shall be 16 m/sec and20m/sec respectively.b) Maximum gas velocity shall be 13 m/sec (15 m/sec for units basedon high GCV low ash coals) except in flue gas duct from ID fanoutlet to chimney inlet, where the maximum velocity limit can be 16m/sec.ii) The velocities in the ducts shall not exceed the above limits under thefollowing conditions, all occurring together:a) Design/ best/ worst coal firing at 100% BMCR load whichevergives maximum flow.b) 25% excess air over and above the stoichiometric air at economizerinlet.c) Air heater air in leakage 10% for secondary air and 15% for primaryair or actual guaranteed whichever is higher.d) Design ambient temperature of 27 0 C and 60 % RH.57

Standard Technical Features of BTG System for Supercritical 660/800 MW Thermal UnitsThe above velocities shall not be exceeded even in case of operationwith one stream of ID, FD, PA fans and air heater operation at 60% ofBMCR load.7.2.2 Loads for duct and structure designThe duct design shall take into account following loads all occurring together:i) Wind loads.ii)Dead weight including weight of insulation, lining, wash water and thevertical live load.iii) Horizontal ducts to be designed for minimum 245 kg/m² additional flyash loading on the surface or for one fourth of duct full of ash or formaximum possible accumulation of ash in the ductwork, under allnormal, upset or abnormal operating conditions, whichever is higher.Flue gas ducts downstream of ESP shall be designed for additional flyash loading on the surface as above or for one tenth of duct full of ash orfor maximum possible accumulation of ash in the ductwork, under allnormal, upset or abnormal operating conditions, whichever is higher.The ash accumulation considered for economizer bypass duct (ifprovided) upto Guillotine gate shall be 100% filled with ash. The ashdensity for the purpose of loading shall be taken as 1350 kg/m 3 .iv) Expansion joint reaction.v) The following minimum load factors shall be applied to the design loadsfor duct work (excluding support structure):Temperature ( 0 C) 27 37 93 149 205 260 316 321Loading factor 1.00 1.02 1.12 1.19 1.25 1.29 1.34 1.42vi)The ductwork and its structure shall take into account loads due to futureaddition of FGD interconnection ducts and dampers in the duct betweenID fan outlet and chimney inlet transition piece.7.2.3 Duct design pressureAll flue gas ducts, air ducts and the wind boxes shall also be designed for ±660 mmwc pressure or maximum conceivable pressure of the relevant fans,whichever is higher, at 67% of yield strength of material.7.2.4 Type of duct constructionThe ducts shall be of rectangular cross-section and shall be of all weldedconstruction. Following requirements shall be complied with:58

<strong>Standard</strong> <strong>Technical</strong> <strong>Features</strong> <strong>of</strong> <strong>BTG</strong> <strong>System</strong> <strong>for</strong> <strong>Supercritical</strong> <strong>660</strong>/800 MW Thermal Unitsiv) Fan BalancingThe fans shall be statically and dynamically balanced be<strong>for</strong>e shipment andbalancing <strong>of</strong> each fan shall be checked and adjusted at site, if necessary.7.1.5 Flow measuring devicesi) The draft plant shall include flow measuring devices in the air system <strong>for</strong>total air flow measurements and control with adequate number <strong>of</strong> tappingpoints.ii) Three independent pairs <strong>of</strong> tapping points with the necessary isolatingvalves shall be provided <strong>for</strong> control, measurement and test.iii) Two nos. duplex temperature element with thermowells <strong>for</strong> temperaturecompensation shall be provided.iv) Fan inlet flow measurement shall be provided using fan inlet elbow.However, if such an arrangement is not possible, flow element (venturi/aer<strong>of</strong>oil system) shall be provided with three pair <strong>of</strong> tapping points atsuction <strong>of</strong> each FD Fan.7.2 Duct Work7.2.1 Duct work sizing criteriai) Allowable velocities in the duct work shall be as below.a) Maximum velocity <strong>for</strong> cold air and hot air shall be 16 m/sec and20m/sec respectively.b) Maximum gas velocity shall be 13 m/sec (15 m/sec <strong>for</strong> units basedon high GCV low ash coals) except in flue gas duct from ID fanoutlet to chimney inlet, where the maximum velocity limit can be 16m/sec.ii) The velocities in the ducts shall not exceed the above limits under thefollowing conditions, all occurring together:a) Design/ best/ worst coal firing at 100% BMCR load whichevergives maximum flow.b) 25% excess air over and above the stoichiometric air at economizerinlet.c) Air heater air in leakage 10% <strong>for</strong> secondary air and 15% <strong>for</strong> primaryair or actual guaranteed whichever is higher.d) Design ambient temperature <strong>of</strong> 27 0 C and 60 % RH.57

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