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 Unitsiii)During start up conditions, quality of the influent shall be considered asbelow:a) TDS, ppb : 2000b) Silica, ppb : 150c) Crud, ppb (mostly black oxide of Iron) : 1000During start-up condition, the sodium and chloride content at the outletof CPU shall not exceed 5 ppb and 10 ppb respectively. For designpurposes, average crud loading shall be considered as 500 ppb. Undersuch conditions, total crud content of the effluent shall not exceed 150ppb.Useful service run between two regenerations under start-up conditionshall not be less than 50 hours.iv)Under condenser tube-leakage condition, the plant shall be designed for2000 ppb TDS in addition to the normal influent contaminants stated inas specified at (ii) above. The cation and anion load in 2000 ppb TDSshall be based on the circulating water analysis. Under such condition,both sodium content and silica content of the effluent shall be limited to20 ppb maximum.Useful service run between two regeneration under condenser tubeleakage condition shall not be less than 50 hours.v) The bed cross section shall be such that the average velocity ofcondensate through it shall not exceed 2 meters/min at the design flowrate. For spherical vessels, average velocity shall be limited to 1.75meters/min at the design flow. The effective depth of the mixed resin bedin the condensate polisher service vessels shall not be less than 1100mm.vi) At the design flow rate, the pressure drop across the polisher servicevessels with clean resin bed shall not exceed 2.1 kg/cm 2 . Maximumpressure drop under dirty conditions will be restricted to 3.5 kg/cm 2including the pressure drop across effluent resin traps.vii) Cation resins shall be regenerated by technical grade hydrochloric acidto IS:265 (concentration 30-33% by volume) and anion resins by sodiumhydroxide, rayon grade to IS:252 available as 48% lye or as flakes.22.3 System Requirements for CPUi) Service Vesselsa) Design pressure of service vessels shall be equal to shut off pressureof condensate extractions pump + 5% margin. For all other pressurevessels the design pressure shall be at least 8 kg/cm 2 (g).b) Design temperature of the vessel shall take care of all operatingregimes including HP-LP bypass operation.195
Standard Technical Features of BTG System for Supercritical 660/800 MW Thermal Unitsc) Service vessels shall be designed and constructed in accordancewith the ASME code Section- VIII or equivalent internationalstandard or IS 2825. Suitable mill tolerance shall be considered fordetermining the thickness of the shell and dished ends. A minimumthinning allowance of 2 mm shall be considered for the dished ends.d) The service vessels shall be fabricated from carbon steel plates toSA 285C or SA-516 Gr. 70 or equivalent and internally rubber linedto 4.5 mm thickness (minimum). The lining used shall be soft rubberhaving a shore durometer reading of 40-70 on the A scale, or semihardrubber having a durometer reading of 45-70 on the D scale.ii)Exchange Resinsa) The cation- anion ratio shall be in the range 1.5:1 to 2:1 on volumebasis. In case any non ionic resin is used the same shall represent atleast 10 % of the bed volume, but not less than 15 cm of the beddepth in the resin separation/ cation regeneration tank.b) Base of the ion-exchange resins shall be copolymer of styrene anddivinylbenzene forming a macroporous or macroreticular structure.The type of resins shall be as below:1. Cation resin : Strong acid, with sulfonic acidfunctional group.2. Anion resin : Strong base, with quaternaryammonium (type- I) functionalgroup.3. Inert resin : Non ionic, compatible with the(if applicable)above type resins.c) The resin shall be suitable for the condensate temperature that maybe achieved in all operating regimes of TG cycle. However, theanion resin shall be suitable for temperature upto 60 0 C.d) Resins shall be monosphere with uniformity coefficient of 1.1.iii)Emergency Bypass Systema) Each CPU shall be provided with an automatic bypass system forthe condensate polisher on the condensate inlet and outlet headers ofthe unit. In the event of excessive pressure differential between thecondensate inlet and outlet headers, this control valve will openautomatically to bypass requisite quantity of condensate to preventthis pressure differential from exceeding a preset limit.196
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Standard Technical Features of BTG System for Supercritical 660 ...

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