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 ...
Standard Technical Features of BTG System for Supercritical 660/800 MW Thermal Units23.1 GeneralCHAPTER- 23CHEMICAL DOSING SYSTEM23.1.1 Water chemistry of boiler feed water during normal operation of the plantshall be maintained using combined water treatment (CWT) comprising ofoxygen dosing and ammonia dosing in the condensate and feed water as perthe guidelines of EPRI, USA/ VGB, Germany/ CEGB, UK/ relevant Japanesestandard. The parameters of feed water proposed to be maintained in case ofCWT are as below:i) Cation conductivity : ≤ 0.15 micro siemens/ cmii) Hydrazine : Niliii) pH value (25 0 C) : 8- 9.3iv) Oxygen : 20- 200 ppbv) Iron : ≤ 5 ppbvi) Silica : ≤ 10 ppb23.1.2 During startup or chemistry excursions, all volatile type of treatment (AVT)using ammonia and hydrazine dosing shall be used. The following parametersshall be maintained in case of AVT:i) Cation conductivity : ≤ 0.25 micro siemens/ cmii) Hydrazine : 10-15 ppbiii) pH value (25 0 C) : 9.0- 9.6iv) Oxygen : ≤ 7 ppbv) Iron : ≤10 ppbvi) Silica : < 10 ppb23.1.3 The concentration of sodium and chloride in the condensate at the outlet ofCPU shall be considered as 2 ppb each under normal operating conditions.During start-up condition, the sodium and chloride content at the outlet ofCPU shall be considered as ≤ 5 and ≤ 10 ppb respectively.23.2 Oxygen Dosing System23.2.1 Oxygen shall be dosed in the condensate and in feed water circuit of each uniti.e. at outlet of condensate polishing unit and at the outlet of deaerator (suctionline of boiler feed water pumps). Oxygen dosing at additional points shall alsobe provided, if required, as per manufacturer's standard practice.201
Standard Technical Features of BTG System for Supercritical 660/800 MW Thermal Units23.2.2 The dosing system shall be provided with set of oxygen cylinders alongwithrequired cylinder isolation/ check valves, cylinder manifolds, isolation valvesin the common manifold, piping from manifold, dosing (automatic type)valves, check (non-return type) valves, associated control system andinstruments etc.23.2.3 The dosing rate of oxygen shall be regulated automatically by control systembased on the quality of condensate water and quality of feed water as the casemay be.23.2.4 For each dosing location, system shall be designed for dosage rate of 200 ppb.The number of oxygen cylinders to supplied and installed shall cater for onemonth requirement of each unit.23.3 All Volatile Treatment (AVT) System23.3.1 Under AVT, ammonia and hydrazine shall be dosed in the feed water atsuction lines to the boiler feed pumps as well as at the condensate pumpsdischarge after the condensate polishing unit. Ammonia shall be used as pHcontrol agent and hydrazine as oxygen scavenger.23.3.2 Each unit shall be provided with skid mounted dosing systems for ammoniaand hydrazine, each system comprising of 1x100% capacity measuring tank,1x100% capacity preparation/ dosing tank and 2x100% metering pumpscomplete with strainers, piping, valves, fittings, instrumentation and controlpanel etc. Ammonia and hydrazine shall be received in containers/ barrels andhand pumps (drum pumps) shall be provided for transfer of ammonia andhydrazine to the respective measuring tanks. The flow of chemical frommeasuring tank to the preparation/ storage tank shall be by gravity.23.3.3 Space provision shall be kept in the main plant building for storage ofammonia and hydrazine containers/ barrels as per one month requirement ofeach unit. The measuring and preparation/ storage tanks for each chemicalshall be sized for one day requirement of the unit. Metering pumps for eachchemical shall be of horizontal positive displacement, reciprocating andvariable stroke type. All the chemical measuring/ preparation/ storage tanksand metering pumps shall be of SS-316 construction. The provision shall bemade for flushing of the metering pumps by the condensate/ DM water.202
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<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 Units23.2.2 The dosing system shall be provided with set <strong>of</strong> oxygen cylinders alongwithrequired cylinder isolation/ check valves, cylinder manifolds, isolation valvesin the common manifold, piping from manifold, dosing (automatic type)valves, check (non-return type) valves, associated control system andinstruments etc.23.2.3 The dosing rate <strong>of</strong> oxygen shall be regulated automatically by control systembased on the quality <strong>of</strong> condensate water and quality <strong>of</strong> feed water as the casemay be.23.2.4 For each dosing location, system shall be designed <strong>for</strong> dosage rate <strong>of</strong> 200 ppb.The number <strong>of</strong> oxygen cylinders to supplied and installed shall cater <strong>for</strong> onemonth requirement <strong>of</strong> each unit.23.3 All Volatile Treatment (AVT) <strong>System</strong>23.3.1 Under AVT, ammonia and hydrazine shall be dosed in the feed water atsuction lines to the boiler feed pumps as well as at the condensate pumpsdischarge after the condensate polishing unit. Ammonia shall be used as pHcontrol agent and hydrazine as oxygen scavenger.23.3.2 Each unit shall be provided with skid mounted dosing systems <strong>for</strong> ammoniaand hydrazine, each system comprising <strong>of</strong> 1x100% capacity measuring tank,1x100% capacity preparation/ dosing tank and 2x100% metering pumpscomplete with strainers, piping, valves, fittings, instrumentation and controlpanel etc. Ammonia and hydrazine shall be received in containers/ barrels andhand pumps (drum pumps) shall be provided <strong>for</strong> transfer <strong>of</strong> ammonia andhydrazine to the respective measuring tanks. The flow <strong>of</strong> chemical frommeasuring tank to the preparation/ storage tank shall be by gravity.23.3.3 Space provision shall be kept in the main plant building <strong>for</strong> storage <strong>of</strong>ammonia and hydrazine containers/ barrels as per one month requirement <strong>of</strong>each unit. The measuring and preparation/ storage tanks <strong>for</strong> each chemicalshall be sized <strong>for</strong> one day requirement <strong>of</strong> the unit. Metering pumps <strong>for</strong> eachchemical shall be <strong>of</strong> horizontal positive displacement, reciprocating andvariable stroke type. All the chemical measuring/ preparation/ storage tanksand metering pumps shall be <strong>of</strong> SS-316 construction. The provision shall bemade <strong>for</strong> flushing <strong>of</strong> the metering pumps by the condensate/ DM water.202
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