boiler manual umpp.pdf

P 08.03.18 S.W.KANG S.H.SONGRev. Date Prepared Coordinated Checked

Client :

Engineer :

Contractor :

Sub Suplier :

Project Title : Orig-Pc

T07073

Date Name Scale N/A SY Prepared 08.03.18 S.W.KANG DOC. TITLE Contents Coordinated CodeChecked 08.03.18 S.H.SONGApproved 08.03.18 S.C.SONGDept. Reg. No.

M001

P T07073-HAY-SY -M001 1/53

Owner Document No. : TCE.5146A-510-00-1189

Doosan Heavy Industries &Construction Co. Ltd.

Document No. :

4000 MW ULTRA MEGA POWER PROJECTAT MUNDRA, GUJARAT, INDIA

PROCESS AND SYSTEMDESCRIPTION

HAY

BOILER BASICDESIGN TEAM

First Issued Details of Revision

COASTAL GUJARAT POWER LIMITED(A WHOLLY OWNED SUBSIDIARY OF THE TATA POWER COMPANY LIMITED)

FOR INFORMATION

Pc

Type

Dept. UNID Rev Version

Page-No.

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UMPP Mundra ( 800MW x 5 Units ) Process and System Description

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DEFINITIONS 1.1 Plant Description

This is a document, derived from the clients plant requirements, which covers the following: Basic plant description with expected performance in the base load operation. It outlines the design basis of the plant and the basis of more detailed documents such as the individual System Operating Philosophies. 1.2 Process Flow Diagram (PFD) General The Process Flow Diagram (PFD) is the universal way to present the Heat and Material balances needed to meet the requirements described in the Plant Description Heat and Material balances are required to enable: - Specifications to be prepared for pipes/flues, equipment, instruments. Preparation of Operating and Maintenance manuals/operator training. Commissioning/Plant performance. Reference PFDs The Process Flow Diagrams cover the main processes involved in Power generation Systems, and incorporate the scope necessary to meet the requirements for Mundra(5x800MW), 4000MW Ultra Mega Project. 1.3 System Operating Philosophies A Boiler Plant comprises numerous systems, such as, Steam and Water, Air & Gas and Combustion. The Operating Philosophies for each of these systems describe the required degree of mechanical operation on selected parameters. 1.4 Piping and Instrumentation Diagram (P&ID) Piping and Instrumentation Diagrams (P&IDs) define the engineering and construction requirements for the sections of the plant in Doosans scope of supply. P&IDs which are attached in the technical specification cover all the processes involved in Power Generation Systems, and incorporate the scope necessary to meet the Doosans requirements for Mundra UMPP(5x800MW) Project.

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2.0 PROCESS AND INSTRUMENT DIAGRAM DESCRIPTION 2.1 PROCESS FLOW DIAGRAMS The Process Flow Diagram (PFD) is the universal way to present Heat and Material balances. Heat and Material balances are required to enable: Specifications to be prepared for pipes/flues, equipment, instruments. Preparation of Operating and Maintenance manuals/operator training. Commissioning/Plant performance The PFD should treat the boiler as an item of equipment, with a number of inputs and outputs linked to all the other equipment required to support the boiler. There are basically two sets of Heat and Material balances to be prepared, which have the following inputs and outputs with the boiler: Water/Steam flows Economiser/Reheater inlet and Superheater/Reheater outlet. Air/Gas flows Fans inlet and Stack inlet(EP outlet). The PFD output data is a diagram of each part of the system with design and normal operating conditions and associated pipe sizes, pipe thicknesses, pipe class and insulation code. 2.1.1 CONFIGURATION OF SUPERHEATER SYSTEM DESCRIPTION Two spray-type superheater(SH) desuperheaters for stage-1 (10HAH40-BR023A,B) are installed in the connecting links (10HAH40BR024) between the primary superheater(LTSH) outlet header(10HAH30) and division panel inlet headers(10HAH42), and two additional spray-type superheater (SH) desuperheaters for stage-2(10HAH50-BR029A,B) are installed in the connecting links between the division panel outlet headers(10HAH47) and the SH finishing inlet header(10HAH55) to reduce steam temperature, when necessary, and to maintain the temperatures at design values, within the limits of the nozzle capacity.

Temperature reduction is accomplished by spraying water into the path of the steam through a nozzle at the inlet end of the desuperheater. It is essential that the spray water be chemically pure and free of suspended and dissolved solids, containing only approved volatile organic treatment material, in order to prevent chemical deposition in the superheater and carry-over of solids to the turbine.

CAUTION: During start-up of the unit, if desuperheating is used to match the outlet steam temperature to the turbine metal temperatures, care must be exercised so as not to spray down below a minimum of 11C (20F) above the saturation temperature at the existing operating pressure. Desuperheating spray is not particularly effective at the low steam flows of start-up. Spray water may not be completely evaporated but be carried through the heat absorbing sections to the turbine where it can be the source of considerable damage. During start-up, alternate methods of steam temperature control should be considered.

The locations of the desuperheaters(Stage-1, 10HAH40-BR023A, B , Stage-2, 10HAH50-BR029A, B) between the Primary superheater (LTSH) and SH division panel section and between the SH division panel section and the SH finishing section, help ensure that water carry-over to the turbine does not occur. It also eliminates the necessity for high temperature resisting materials in the desuperheater construction.

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BLOWOUT PROCEDURE FOR DESUPERHEATER SPRAY WATER LINES Each desuperheater is fitted with a renewable liner to take the wear of erosion from the spray water stream, thus protecting the main desuperheater shell. Excessive noise from within a desuperheater usually indicates a worn liner and the Service Department of this Company should be contacted when this or any such abnormal conditions may arise. Sufficient clearances should be provided around the desuperheaters for replacing liners.

MAINTENANCE The spray water lines should be blown out before using the desuperheaters on a new unit and after repairs on the spray water lines have been made. They may also be blown when there appears to be any indication of plugging. Always have full pressure on the boiler when blowing out the desuperheaters.

Each desuperheater should be blown out in the following sequence:

Firstly close the isolating valves(10LAE52AA041, 10LAE52AA001) in the main spray line and open the blowoff(drain) valves(10LAE52AA401/2), and then open the valves in the bypass line (10LAE52AA002, 10LAE52AA042, 10LAE52AA071) for 1 minute. Secondly Close the bypass line valves(10LAE52AA001, 10LAE52AA041, 10LAE52AA071) and open the main spray line isolating valves(10LAE52AA041, 10LAE52AA001) and control valve(TCV,10LAE52AA071) but leave the blowoff valves(10LAE52AA401/2) open for another minute to clear the waste line before restoring the system to its operating status.

Repeat the above blowing sequence for the other spray stations. When blow the bypass station do the same condition. Above is shown by only one spray station.

NOTE: The blowoff valves should be installed close to the spray water piping and with no

bends intervening, if possible.

SUPERHEATER SCHEMATIC DIAGRAM

S-30

S-33

S-28

S-31

S-11

S-27 S-8

S-24

S-9S-16

S-17

S-18

S-12

S-29S-1

S-3

S-25 S-2

S-26

S-5

S-4

S-14 S-13

S-7

S-10

S-26A S-26B

S-32B S-32A

S-15

S-19

S-20

S-21

S-23

S-22 S-20B S-6

S-32

Separator

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Tag No. Circuit Name S-33 SH Final Outlet Header S-32b SH Final Outlet Term. Tubes S-32 SH Final Tubes S-32a SH Final Inlet Term. Tubes S-31 SH Final Inlet Header S-30 Links to SH Final Inlet Header S-29 SH Desuperheater #2 S-28 Links to SH Desuperheater #2 S-27 SH Panel Outlet Header S-26b SH Division Panel Outlet Term. Tubes S-26 SH Division Panel Tubes S-26a SH Division Panel Inlet Term. Tubes S-25 SH Panel Inlet Header S-24 Links to SH Panel Inlet Header S-23 SH Desuperheater #1 S-22 Links to SH Desuperheater #1 S-21 Low Temperature SH Outlet Headers S-19,20,20b Low Temperature SH Tubes S-18 Backpass Lower Rear Header S-15,16,17 Backpass Front,Roof & Rear Wall Tubes S-14 Backpass Lower Front Header S-13 Backpass Lower Side Header

S-12 Extended Wall Outlet Link to Backpass Lower Front Header S-11 Extended Wall Outlet Header S-9,10 Extended Wall Side & Floor Tubes S-8 Extended Wall Inlet Header S-7 Backpass Side Wall Tubes S-6 Backpass Side Wall Inlet Headers S-5 Furnace Roof Outlet Header S-3,4 Furnace Roof Tubes S-2 Furnace Roof Inlet Header S-1 Links to Roof Inlet Header

S-19,20,20B

S-1 S-18

S-29

S-30 S-26A,26,26B

S-3,4

S-2 S-28

S-21 S-27 S-22

S-24

S-32A,32,32B

S-31 S-33S-5

S-23

S-6

S-7

S-8

S-9,10

S-11

S-12

S-13

S-14

S-15,16,17

S-25

Separator

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2.1.2 CONFIGURATION OF REHEATER SYSTEM DESCRIPTION A spray-type reheater (RH) desuperheater(10LBC31-BR001, 10LBC32-BR001) is installed in the cold reheat piping to Platen Reheater inlet header(10HAJ10) to reduce steam temperature, when necessary, and to maintain the temperatures at design values, within the limits of the nozzle capacity. Temperature reduction is accomplished by spraying water into the path of the steam through a nozzle at the inlet end of the desuperheater. It is essential that the spray water be chemically pure and free of suspended and dissolved solids, containing only approved volatile organic treatment material, in order to prevent chemical deposition in the reheater and carry-over of solids to the turbine.

CAUTION: During start-up of the unit, if desuperheating is used to match the outlet steam temperature to the turbine metal temperatures, care must be exercised so as not to spray down below a minimum of 11 C (20F) above the saturation temperature at the existing operating pressure. Desuperheating spray is not particularly effective at the low steam flows of start-up. Spray water may not be completely evaporated but be carried through the heat absorbing sections to the turbine where it can be the source of considerable damage. During start-up, alternate methods of steam temperature control should be considered.

The location of the desuperheaters, at inlet of RH low temperature inlet header(10HAJ10), help ensure that water carry-over to the turbine does not occur. It also eliminates the necessity for high temperature resisting materials in the desuperheater construction.

MAINTENANCE Each desuperheater(10LBC31BR001, 10LBC32BR001) is fitted with a renewable liner to take the wear of erosion from the spray water stream, thus protecting the main desuperheater shell. Excessive noise from within a desuperheater usually indicates a worn liner and the Service Department of this Company should be contacted when this or any such abnormal conditions may arise. Sufficient clearances should be provided around the desuperheaters for replacing liners.

BLOWOUT PROCEDURE FOR DESUPERHEATER SPRAY WATER LINES The spray water lines should be blown out before using the desuperheaters on a new unit and after repairs on the spray water lines have been made. They may also be blown when there appears to be any indication of plugging. Always have full pressure on the boiler when blowing out the desuperheaters. Each desuperheater should be blown out in the following sequence :

Firstly close the isolating valves(10LAF52AA041, 10LAF52AA001) in the main spray line and open the blowoff(drain) valves(10LAF52AA401/2), and then open the valves in the bypass line (10LAF52AA002, 10LAF52AA042, 10LAF52AA071) for 1 minute. Secondly Close the bypass line valves(10LAF52AA001, 10LAF52AA041, 10LAF52AA071) and open the main spray line isolating valves(10LAF52AA041, 10LAF52AA001) and control valve(TCV,10LAF52AA071) but leave the blowoff valves(10LAF52AA401/2) open for another minute to clear the waste line before restoring the system to its operating status. Repeat the above blowing sequence for the other spray stations. When blow the bypass station do the same condition. Above is shown by only one spray station. NOTE: The blow-off valves should be installed close to the spray water piping and with no

bends intervening, if possible.

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Tag No. Circuit Name R-7 Reheater Outlet Header R-6b Reheater Final Outlet Term. Tubes R-6 Reheater Final Tubes R-6a Reheater Final Inlet Term. Tubes R-5 Reheater Intermediate Header R-4b Reheater Platen Outlet Term. Tubes R-4 Reheater Platen Tubes R-4a Reheater Platen Inlet Term. Tubes R-3 Reheater Inlet Header R-1 Reheater Desuperheater

R-4

R-3

R-4b

R-6

R-7

R-8

R-6a

R-1 R-2

REHEATER SCHEMATIC DIAGRAM

R-5

R-4a R-6b

R-2 R-8R-1

R-4 R-6

R-2 R-8R-1

R-3 R-7

R-5

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Tag No. Circuit Name E-10 Economizer Waterwall Inlet Links E-9 Economizer Mixing Line E-8 Economizer Outlet Links E-7 Economizer Hanger Tube Outlet Header E-6 Economizer Hanger Tubes E-5 Economizer Junction Headers

Economizer (Bank2) Tubes E-4

Economizer (Bank1) Tubes E-3 Economizer Inlet Header E-2 Economizer Inlet Leads E-1 Feedwater Line

E-7

E-6

E-5

E-4

E-8,9,10

E-3E-1

ECONOMIZER SCHEMATIC DIAGRAM

E-2

E-2

E-1

E-4 E-6

E-5

E-3

E-10

E-9

E-8

E-7

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2.2 PIPING AND INSTRUMENT DIAGRAMS

Piping and Instrumentation Diagrams (P&IDs) are key items in the documentation, which define the engineering and construction requirements for the sections of the plant in Doosans scope of supply. 2.3 PIPING AND INSTRUMENT DIAGRAMS DESCRIPTIONS STEAM AND WATER Each diagram in the design series has an associated diagram description, which has a System Purpose and Description of the P&ID. 2.3.1 P&ID Drawing Title: Economiser System and Feed Inlet Pipework

Drawing Number: Doosan : T07073-XG02-PI-D001 Owner : TCE.5146A-510-00-0612

Design Basis: IBR / ASME

System Purpose The transfer of feedwater from the Boiler Design Code boundary to the Furnace inlet header. The extraction of useful heat from the flue gas by water flow in the economiser(s) Prevent from evaporating the water at economizer outlet

Description of Drawing

The function of the economizer is to preheat the boiler feedwater before it is introduced into the furnace waterwalls by recovering some of heats of the flue gases leaving the boiler. The flow path and arrangement of the economizer circuits is shown on P&ID drawing T07073-XG02-PI-D001 and the Boiler General Arrangement drawings T07073-CC02-GA-A002. Feedwater is supplied to the economizer system via feed check valve(10LAB50AA002), which is used during dry mode operation, no BRP operation. But during wet mode operation feedwater is supplied through the another check valve(10HAG20AA003) which is located in the start-up bypass system(P&ID No. T07073-XG02-PI-D008). The feedwater flow is upward through the economizer sections, that is, in counter flow to the hot flue gases. Most efficient heat transfer is thereby accomplished, while the possibility of steam generation within the economizer is minimized by the upward water flow.

During start-up and low load before steam produced, minimum 5% load of feedwater excluding feedwater minimum recirculation flow is introduced to the economizer tube to prevent from steaming at economizer horizontal tube section. The water temperature of each economizer outlet string is measured using a quick response temperature transmitter(10HAC30CT101,102). The measured temperature is transmitted to the control system to be monitored whether or not evaporating at the economizer water at the economizer outlet. There is flow measurement(FE,10LAB50CF001) upstream of economizer system to measure the economizer inlet supply water quantity. Three flow transmitters(FT,10LAB50CF101, 102,103) control the feedwater flow that is deducted SH spray water from feedwater pump discharge flow. In case feedwater flow at economizer inlet falls below the low set points, alarm or trip signals are generated by the DCS based on the feedwater transmitters (FT,10LAB50CF101/2/3) signal. In case trip signal happens, all the fuel must be automatically tripped with a maximum time delay.

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Feedwater with required flow rate, pressure and temperature is delivered to the boiler boundary by a pump system. Pressure tapping points with isolating valve for test(PP,10LAB50CP401) and analogue transmitters (PT,10LAB50CP101,102) are included for monitoring and transmitting the economiser inlet pressure to the DCS, and for differential measurements where pressure loss guarantees from the economiser inlet to the superheater outlet are part of the specification requirements. Also temperature transmitters(TT,10LAB50CT101,102) are installed to monitor and transmit to the DCS. A drain line(MOV,10LAB50AA441) is branched out at the economiser inlet link(10LAB50BR001) and a branch for chemical cleaning service is provided on the drain line. Normally drain valve is closed except for maintenance. The economizer is located at the last stage of heat recovery in the back pass of the boiler. The economizer is arranged in four banks horizontally and made of bare tubes. The economizer banks are arranged in such a manner that each row is in line in relation to the row above and below. All tube circuits originate from the economizer inlet header(10HAC10BB001), and discharge into three economizer junction headers(10HAC20BB001-003). A set of economizer hanger tubes connect the junction headers to the economizer outlet header(10HAC25BB001). From the economizer outlet header (10HAC25BB001), the fluid flows through the two outlet links (10HAC30BR008), mixing link (10HAC30BR009), two water wall inlet links (10HAC30BR010) into the both of furnace lower side wall headers (10HAD10BB001). See the P&ID, No. T07073-XG02-PI-D002. A low point drain connection via the start-up flash tank(Drawing No. : T07073-XG02-PI-D009, Boiler Drain & Vent System, 10LCQ20BB001) in boiler area is provided for removal of water during dry storage. The vent line(10HAC30BR502) which is connected on the economizer outlet header (10HAC25BB001) has motorized vent valve(MOV,10HAC30AA541) and manual isolating valve(10HAC30AA501). The motorized vent valve is closed in time delay from detected the economizer inlet flow reaches over 10 ton/hr. The air vent release provides a convenient point for nitrogen gas injection for blanketing or inerting during periods of wet or dry storage respectively. An isolating(10HAC30AA201) and a screw down non-return valve(10HAC30AA202) are included for nitrogen supply isolation. One pressure part thermowell(TW,10LAB50CT401) is provided for performance testing. The temperature is sensed by a thermocouple(TT,10LAB50CT101,102), and the resultant signal is either transmitted directly to the DCS through a transmitter to a 4 20mA high level analogue input. The measured temperature is used for indication, and Top Feed Heater Out of Service operation (THOS). For availability reasons the feedwater temperature should be measured twice especially when the measured signal is used for control function manipulation. The frequency with which soot blowers are used depends entirely on local conditions. When the economizer is first placed in operation, the economizer soot blowers(Tag No. : 221-238, See P&ID No. T07073-XG-PI-D020) should be blown about once every shift. Observation of the increase in draft loss between blow outs will determine how long an interval may be set as a standard. In many cases, it has been found that blowing the economizer soot blowers once a day or less is sufficient.

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2.3.2 P&ID Drawing Title: Evaporation System Drawing Number: Doosan : T07073-XG02-PI-D002 Owner : TCE.5146A-510-00-0613 Design Basis: IBR / ASME

System Purpose Source of water for the evaporative circuits (i.e. the furnace walls). Source of 1. two phase mixture from the evaporative circuits into water and saturated steam. 2. overheated steam from evaporative circuits into superheater section

Description of Drawing The referenced drawing shows furnace system from furnace lower header(10HAD10BB001) to riser pipe(10HAD30BR009) of furnace outlet. During start-up and low load condition two-phase flow is circulated in the furnace with assistance by boiler recirculation pump(10HAG20AP001, P&ID No.T07073-XG-PI-008) and separated by four separators(10HAD40,42,43,45 BB031). But during normal operation the fluid is superheated in the furnace and separator has no separation. It is just the path of superheated steam which is produced in the furnace. Transfer of sub-cooled water from the economiser outlet header side connecting pipes (10HAC30BR008) to the furnace lower side headers(10HAD10BB001) through economiser outlet mixing line(10HAC30BR009). This incoming sub-cooled water is distributed to furnace wall tubes which are connected to the furnace lower front and rear header as a ring header configuration. All the furnace tubes which are divided evenly are originated from front and rear lower header. Furnace wall is consisted as spiral wall that has inclination with 17.3 degree. There are four intermediate headers(10HAD15BB001-004) at the transition area in the furnace, which is junction point of spiral wall and vertical wall tubes. The ratio of spiral wall tube(10HAD12) numbers to vertical wall(10HAD20) tube numbers are 1 to 3. That means vertical tube numbers are 3 times of spiral wall tube number. There are four furnace outlet headers(10HAD25BB001-004) and each header has four riser pipes(10HAD30BR009,BR020,BR029) these are arranged and connected with considering temperature distribution to the separators (10HAD40,42,43,45 BB031) respectively. Extraction of heat from the combustion process in the furnace through the spiral tube walls to the fluid. The heat transferred to the fluid causes density change that induces natural circulation of fluid from the separator storage tank(10HAD50BB033) to the furnace walls via the downcomers(10HAG10BR001), and back to the separators(10HAD40,42,43,45 BB031) as a two-phase mixture. The mixture of steam and water is collected at the top of the walls in outlet headers and transferred to the separators, which separate the steam and water by using centrifugal force at the separators(10HAD40,42,43,45 BB031). Regarding separator and storage tank, see the P&ID No. T07073-XG-PI-D003. Furnace lower ring header has two drain connections at the front(10HAD50BR402) and rear (10HAD50BR401) headers, and each intermediate header(10HAD15) has drain connections (10HAD15BR401,402,403,404). The drain lines are linked as a group of lower header (10HAD50BR403) and intermediate header(10HAD15BR405) respectively. This combined drain lines that discharge through isolating valve(lower ring header : MOV,10HAD50AA441 / Intermediate header : MOV,10HAD15AA441) to the manifold(10LCQ20BR402) which is located in front of boiler start-up flash tank. See P&ID No. T07073-XG02-PI-D009.

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Capped chemical cleaning and drain connections are fitted on the dedicated lower wall drains. The drain system of lower ring headers(10HAD10BB001) is in addition used to fill the boiler for hydrostatic testing. Filling water through the drains reduces the possibility of air pockets forming especially during hydrostatic testing. The present trend is for operators to fill the water in the boiler using the start up feed pump and a filling line. The warm-up line(10HAG30BR001) is activated to warm-up the start-up lines (10LCT10BR002, BR003, 10HAG10BR002,BR003. See P&ID No. T07073-XG02-PI-D008) to reduce the temperature deviation between metal and fluid in preparation of starting boiler during dry mode(once through mode) operation. It extracted from economiser outlet mixing line(10HAC35) and discharged(10HAG15BR001) to upstream(10LAE51BR002, 10LAE52BR002) of the 1st stage desuperheater separately. The motor operated valve(MOV,10HAG30AA041) is opened automatically by control logic when dry mode operation. These valves should be in their positions before changing to dry mode operation. (See P&ID No. T07073-XG02-PI-D008)

- BRP(10HAG20AP001) off - LL Line(10HAG10BR003) MOV(10HAG10AA042) Close - UG Line(10HAG20BR002) LCV(UG, 10HAG20AA041) Open - BRP Inlet(MOV,10HAG20AA041)/Outlet(MOV,10HAG20AA042) MOV Close - BRP Line(10HAG10BR004) Vent MOV(MOV,10HAG10AA041) Close - Pre Warm-up Stop MOV(MOV,10HAG30AA041) Open - WR/ZR Line Isolation MOV(MOV,10LCT10AA041) & LCV(ZR,10LCT10CG091, WR,10LCT10CG092) Close

Thermo-elements are attached on the unheated tube at the spiral wall tube outlet (TE,10HAD12CT001-CT116) and vertical wall tube outlet(TE,10HAD20CT001-CT076) to detect the unheated tube surface metal temperature, which is regarded as the same of steam temperature. The temperatures are monitored continuously and sent to the DCS. Alarm and trip(MFT) setting value is set for protecting from furnace wall tube overheating. In case high temperature is detected through the signal from settled thermo-element alarm signal is shown on the monitor. If a few numbers of thermo-element detect high temperature than trip set value and the detected high temperatures do not return to usual temperature after time delay, the boiler get the MFT signal by the DCS. Trip and alarm temperature is decided by considering allowable metal temperature and design metal temperature and tube thickness and operational circumstances. Temperature transmitters(TT,10HAD30CT101 -108) are installed on the two connection pipes out of four pipes(10HAD30) of each furnace outlet header(10HAD25BB001-004). 2.3.3 P&ID Drawing Title: Water separation system Circulation & Start-up system Drawing Number: T07073-XG02-PI-D003 & T07073-XG02-PI-D008 TCE.5146A-510-00-0614 & TCE.5146A-510-00-0619 Design Basis: IBR / ASME

System Purpose - This system is divided start-up and low load operation and Normal operation, that means wet

mode type(recirculation mode) and dry mode type(once through mode). - Wet Mode(Recirculation mode) : start-up and low load condition. Drain water from separator returns to the economizer inlet pipe.

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Boiler recirculation pump operation Boiler minimum flow rate to prevent from over heating High quality steam flows to the superheater section. - Dry Mode(Once through mode) : Normal operation

Description of Drawing 1) Description for Start-up and Low Load Circulation System A supercritical Once Through Boiler operates under Two modes-Dry Mode (Once Through Mode) and Wet Mode (Recirculation Mode). Transfer of two phase flow from the riser pipes(10HAD30) of furnace outlet headers(10HAD25) to the separators(10HAD40BB031, 10HAD42BB031, 10HAD43BB031, 10HAD45BB031) to separate water and steam by centrifugal force. Separated water goes through the storage tank (10HAD50BB033) and the Boiler recirculation pump(10HAD20AP001) discharges the drain water to the economizer inlet pipe(10LAB50BR001) and separated steam goes to the furnace roof inlet header(10HAH12). Water from separator storage tank(10HAD50BB033) drain line and from feed water pump discharge combines in the mixing piece(10HAG10AM001) to increase NPSH of boiler re-circulation pump(10HAG20AP001) by mixing hot and cold water. The minimum boiler water flow should be kept 35% load flow to prevent from furnace over-heating in order to ensure adequate cooling of the furnace waterwall tubes during start-up and low load operation. As a result, wet conditions prevail in the waterwall tubes of the evaporator, water separator and therefore, the saturated water is recirculated by means of the boiler circulation system. Boiler re-circulation pump(10HAG20AP001) assists to circulate mixed return water from mixing piece(10HAG10AM001) to save the plant energy, to keep minimum water quantity 35% load at the furnace. In other words, the primary purpose of the boiler recirculation system is to ensure a minimum flow of 35% load through the furnace tubes and thus protect them from overheating during start-up and low load operation of the boiler namely Wet mode. 2) Boiler Circulation System-Major Equipments

The boiler circulation system consists of the following major equipments:

z Water Separators(10HAD40,42,43,45BB031) z Separator Storage Tank(10HAD50BB033) z Mixing Piece(10HAG10AM001) z UG Valve(LCV,10HAG20AA091) z Boiler Recirculation Pump(10HAG20AP001) z Separator Drain Valves(WR: LCV,10LCT10AA092 / ZR:LCV,10LCT10AA091) z Flash Tank(10LCT20BB001)

In addition, associated piping, valves and fittings as required to make the system complete are envisaged. 3) Water Separator System & Storage Tank

The water separator system consists of four(4) vertical vessels with four(4) tangential inlet pipes which consist 4 riser pipes per one separator to receive the steam/water from furnace waterwall tubes via riser pipes(10HAD30BR009,BR020,BR029). Each Separator has one

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steam outlet pipe(10HAH10BR001). This outlet pipe(10HAH10BR001) is also located at the top of the water separator to lead the steam to the Roof inlet header(10HAH12BB001). Each separator is designed to handle over 25% BMCR steam flow. The capacity of separator storage tank is designed to accommodate the BMCR water quantity for 10 seconds. Also it has drain nozzle at the lower part. The separation of water and steam is done in the separator and the storage water is controlled by drain valves(WR, LCV,10LCT10AA092 / ZR : LCV,10LCT10AA091) and UG valve(LCV,10HAG20AA091). The storage tank drain water is connected to the drain line(10HAG10BR001) supplying the water either to the BRP(10HAG20AP001) or to the boiler start-up flash tank(10LCQ20BB001) via separator drain valves(MOV,10LCT10AA041, LCV, 10LCT10AA091/2) The storage tank height from tap to tap is 16444 mm and its inside diameter is 555 mm. - SEPARATOR STORAGE TANK LEVEL CONTROL

a) Overview

Storage tank water level is controlled by three level control valves, WR(LCV,10LCT10AA092), ZR(LCV,10LCT10AA091), UG(LCV,10HAG20AA091).

The purpose of circulating water control valve (UG valve) is to control the level with some range in the storage tank level, thus accurate and fast positioning is a prerequisite. It situated just downstream the BRP. It is also the hot start which determines the sizing of the UG valve.

Normally the drain flow from the separator storage tank is recirculating through evaporator by boiler circulation pump(BRP,10HAG20AP001) assistant via control valve(UG) located downstream of BRP into the economizer. UG valve is used for storage tank level control within some setting range and additionally UG valve has functions like control of limited BRP flow capacity and controls economizer inlet flow not to exceed dry mode flow. At the starting stage the full opened UG valve (LCV,10HAG20AA091) is closed as minimum opening position(15% to 23%) when BRP(10HAG20AP001) is ready to start. And after BRP starting the UG valve is controlled automatically and follows the set flow, minimum water wall flow of 35%TMCR, at economizer inlet. Even though the boiler is dry mode the start-up control system is allowed to be controlled by the DCS but steam re-circulation at the start-up system must be protected. When BRP is being operated at dry mode, Motor operated valve(MOV,10HAG10AA042) upstream of mixing piece(10HAG10AM001) must be at the close position and BRP must be stopped within 40%TMCR. Even though the boiler is operated as a dry mode condition, the storage tank(10HAD50BB033) becomes wet mode condition that means water column in storage tank increases wet mode set level(around over 3 meter) at over 40% load by abnormal problem, the BRP(10HAG20AP001) will not be started and the water level is controlled by ZR and WR (LCV,10LCT10CG091, 092) control valve. ZR and WR valves are used for controlling the storage tank level from boiler water filling also. When the storage tank water level decreases down to 3 meters from lower tap level, the UG valve opening position sets to 30%. If BRP operation is stopped the shut-off valve (MOV,10HAG10AA042) which located inlet of mixing piece(10HAG10AM001) will be closed fully with around 20 seconds time delay. When water level down to 1 meter the mixing piece inlet shut-off valve(MOV,10HAG10AA042) gets the lock signal from DCS. And UG valve gets full open signal by DCS with 30 seconds time delay after shut-off valve full close.

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In case BRP is stopped, UG valve is being fully opened but when the water level reaches 3 meter the UG valve opening gets to the 30% of set value. At the water filling period if normal water level(NWL) of storage tank is maintained automatically for two minutes with over 65% ZR valve opening and over 15% WR valve opening, it is assumed that the boiler water filling is over. The drained water through WR and ZR valve during filling up the boiler is drained to the sump via overflow line(10LCQ40BR401) in the condensate receiving tank(10LCQ40BB001). A set of two return valves (WR, ZR valve) is used to control the flow of saturated water from the separator storage tank(10HAD50BB033) into the boiler flash tank(10LCT20BB001). They are designed to accommodate the swell flow during start-up, assuming that the BRP is available for every start. Especially during start-up larger amounts of water (swell flow) need to be drained from the separator(10HAD40,42,43,45BB031). For this purpose additional drain capacity is provided, dumping the excess water into the flash tank(10LCQ20BB001) located in the boiler area. The respective control valves are situated near the flash tank and open when the separator level exceeds a certain threshold lying above the normal set value applicable for normal recirculation via BCP(10HAG20AP001) and control valve(WR, ZR) (split range control). To control the storage tank water level two control valves(ZR, WR) get the level signal by level transmitters(LT,10HAD50CL101,102,103) via DCS. The respective control valves are usually located near the boiler flash tank and open when the separator level exceeds a certain threshold lying above the normal set value applicable for normal recirculation via BRP and control valve (split range control). Before operated the control valves(ZR, WR) the mixing piece inlet shut-off valve(MOV,10LCT10AA041) should be remained open position. When ZR valve opens 80% of opening position the WR valve starts opening. The normal water level of storage tank is around 8.4 meter. These data may be changeable during detail process. The Storage tank Level control logic is designed to control the liquid level in the separator storage tank during boiler start-up and upset conditions to prevent liquid from overflowing into the superheaters. Control is accomplished with two split range drain valves. After start-up, a separate warming control valve(LCV,10HAG15AA071) will control the level of liquid in the separator wet leg.

b) Demand Development

The three (3) Storage tank level transmitter(LT,10HAD50CL101,102,103) signals are pressure compensated and then averaged to develop the process variable for the control loop. This value is compared to a set point and the resulting error signal is sent to the WR (LCV,10LCT10AA092) and ZR(LCV,10LCT10AA091) drain valves. These are split range valves (ZR : 11.4 13.5 meter, WR: 13.1-15.3 meter, Normal water Level : 8.4 meter. The basis level is lower tap level) with the ZR valve providing control from 0 to 50% and the WR valve starting to open at 50%. The WR valve is normally closed position, and is probably only opened when the water begins to boil, thereby causing a decrease in density and a corresponding rapid increase in water level. The water flow into the Separator during boiler start-up will be controlled by the UG valve. The economizer inlet flow will be compared to an operator adjustable set point. The set point will be low limited by the maximum BRP(10HAG20AP001) capabilities and high limited by the minimum required economizer inlet flow. The resulting error signal will be acted upon by a proportional plus integral controller to position the UG valve(LCV,10HAG20AA091). The UG valve is also used to protect the BRP from too low of an outlet pressure. The differential

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pressure across the BRP is measured and compared to a set point. The resulting error is sent to a proportional plus integral controller. The output of this controller is used to low limit the valve position. c) Interlocks

The ZR valve(LCV,10LCT10AA091) will be interlocked closed when the Separator outlet temperature is superheated by at least 20 C and the Unit load is larger than 40% load. The WR valve(LCV,10LCT10AA092) will be interlocked closed by the same conditions as the ZR plus the feedback that the ZR valve is closed.

The mixing piece(10HAG10AM001) inlet isolation valve(MOV,10HAG10AA042) is interlocked open when there is no fire in the boiler. When the Separator outlet temperature is superheated by at least 20 C and the Unit load is larger than 40% load, the mixing piece inlet isolation valve will be interlocked closed to prevent steam from recirculating through the BRP (10HAG20AP001).

The UG valve(LCV,10HAG20AA041) will be interlocked open when the BRP is off or when the mixing piece inlet isolation valve(MOV,10HAG10AA042) is closed. When the BRP is ready to start, the UG valve will be positioned about 15% to 23% open which represents an approximation of the initial position required by the UG valve to control the economizer inlet flow.

The Warming valve(MOV,10HAG30AA041) will be interlocked closed while the BRP is running and then released to control the Separator Wet Leg Level which is controlled by level control valve(LCV,10HAG15AA071) once the BRP is turned off. d) M/A Control Stations Each of the control valves will be supplied with M/A control station. The WR and ZR control stations will be rejected to and locked into manual if two out of three of the Separator level transmitters display bad quality. The UG valve control station will be rejected and locked into manual if the economizer inlet flow displays bad quality. The Warming valve control station will be rejected to and locked into manual' if the Separator Wet Leg level displays bad quality.

4) Recirculation Pump (10HAG20AP001)

One(1) No. Boiler recirculation pump(10HAG20AP001) of glandless, wet motor, vertical type is envisaged to assure water recirculation below minimum once thru load of 35%TMCR, wet mode. The pump will be supported through the downcomers which in turn are supported by separator storage tank(10HAD50BB033). Pump and motor foundations are not required. The boiler recirculation pump is sized for hot-start with high separator pressure. The pump head has to overcome the pressure loss from economizer inlet to the water separator at a flow of approximately 35% TMCR, which is the minimum evaporator flow. The boiler recirculation pump (BRP) is situated in the main stream of start-up feed line, meaning that the entire water flow to the economizer is passing through the BRP at low load. Thus the saturated water from the separator is mixed with cold boiler feedwater upstream of the BRP. This configuration has a number of advantages :

z Better NPSH due to mixing of cold feedwater with the saturated water from the

separator z No need for special NPSH control z Higher rates of pressure decrease in the boiler can be tolerated

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z The idling BRP is kept warm with no need for additional components z Lower thermal stress for the BRP casing

5) Mixing Piece (10HAG10AM001)

In the mixing piece the hot, slightly sub-cooled water from the separator is mixed with cold feedwater. The purpose of the mixing piece is to avoid formation of hot or cold water jets striking pipe walls in uncontrolled manner. The mixing piece consists of a vertical casing with the axial inlet for the hot water at the top and the outlet for the mixed water at the bottom. The cold feedwater enters radially through an elbow into the central pipe, which has many holes. The design is optimized for low pressure drop in the recirculation line, particularly in the case when there is little feedwater flow.

6) Warm-up System(See P&ID No. T07073-XG02-PI-D008)

When the boiler load is approx. 35%TMCR and above, the recirculation system is not in service and is kept warm by a system using hot water from the economizer outlet mixing link(10HAC30BR009) and keeping the piping from separator storage tank(10HAD50BB033) level control valves(drain valves-WR/ZR) up to the level-tanks warm. The BRP (10HAG20AP001) with mixing piece(10HAG10AM001) and valves are kept warm because a small amount of feedwater will flow through these. The warm-keeping system is activated by opening of the motor operated valve (MOV,10HAG30AA041) on warm water supply line(10HAG30BR001). The flow is restricted by the orifices(FO,10HAG30BP001, 10HAG30BP002, 10HAG10BP002) in combination with the manually activated trim valve. The distribution of the warm-keeping water is shown in P&ID drawing, the start up system configuration. The water is fed into the recirculation line(10HAG30BR401) and drain line (10LCT10BR003) to flash tank(10LCT20BB001) through nozzles in the body of the gate valve (MOV,10LCT10AA041) which is installed at the upstream of WR/ZR. The third feed point is directly into the recirculation line(downcomer) (10HAG10BR003) above recirculation isolation valve(MOV,10HAG10AA042). The two feed-points(10HAG30BR002, BR003) are combined as one line(10HAG30BR004) which equipped with an orifice as well as a non-return valve to assure equal flow in the two warm water supply lines(10LCT10BR001, 10HAG10BR005). The warm-keeping water from economizer outlet mixing line(10HAC30BR009) is slowly rising upwards through the above mentioned lines and is removed from the system through the spray water line(10LAE51BR002, 10LAE52BR002) to 1st superheater de-superheater. The remaining part of the recirculating system up to the Storage tank(10HAD50BB033) is kept warm by condensing steam at sub-critical conditions by supercritical fluid from the separators(10HAD40,42,43,45BB031), flowing very slowly downwards. Just above the junction point which is connected from downcomer(10HAG10BR002) to spray water line(10HAG15BR001), the condensate water level, wet leg level, is measured and its signal(LT,10HAG10CL101, 102) is primarily a pressure difference and is used directly for the water leg level control valve(LCV,10HAG15AA071) which is controlling the outflow from the warm-keeping system. In this way the function of the control valve(LCV,10HAG15AA071) is assured for sub-critical as well as for supercritical operation. The start up system including warm-keeping system shows the. on the P&ID No. T07073-XG02-PI-D008.

The most appropriate solution satisfying all functional requirements will be better determined during actual operation and experience.

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The warming control valve(LCV,10HAC15AA071) is used to maintain a warm condition in the piping between the Separator storage tank(10HAD50BB033) and mixing piece (10HAG10AM001) inlet isolation valve(MOV,10HAG10AA042), WR(LCV,10LCT10CG092), and ZR(LCV,10LCT10CG091) valves. This is accomplished by modulating the Warming control valve to adjust the flow water from the separator storage tank through the associated piping to the desuperheater spray header. The valve is controlled by comparing the Separator Wet Leg Level with an operator adjustable set point. The resulting error drives a proportional plus integral controller to position the warming valve. 7) Wet to Dry Mode Changing from wet to dry mode means that the control basis is changed from separator water level control to separator outlet steam temperature control. During the transfer two opposite storage events take place in the boiler, on one hand the energy content increases on the other the content of flow medium, wet content, decreases. To realize that, the fire intensity and the waterwall flow temporarily have to come apart. In the control conception this shifting is reached by first increasing the fire intensity and later the waterwall flow is increased. A load increase starting from low load with water recirculation system operation (automatic level control) and ending in the load range with pure once through operation(automatic temperature control). The following processes take place during this transfer in operation mode and the change mode is explained based on the feedwater flow is assumed as constant. : - Step 1 : The rising firing rate with constant minimum feedwater flow increases the steam

production and decreases the water return flow through separators. The wet steam enthalpy at separator inlet increases.

The steam quality at separator inlet reaches X(dryness) = 1 ; saturated steam flows into the separator; no water is separated anymore causing the water return valve (ZR,LCV,10LCT10CG091) to close.

- Step 2 : The further increase in firing rate still constant minimum feedwater flow effects a slow

superheating of the steam at separators(10HAD40,42,43,45). The boiler internal control is completely blocked feedwater flow on minimum value;

temperature control inactive because the actual steam temperature is still below its set point.

A good deal of the fire increase is not used for steam generation but for getting the

boiler on the higher energy level required for once through operation. The steam temperature at the separator reaches the set point value. - Step 3 : The further increase of the fire intensity causes the steam temperature to exceed the

set point. The temperature controller reacts by increasing the feedwater flow, which is allowed by the max-choice. The temperature control is fully active.

8) Feedwater control System The feedwater system and at least one feedwater pump, including the instrumentation and equipment, has been checked out and is available for operation. During a start-up, the feedwater flow should be controlled remote-manually until a continuous flow is established. The deaerator auxiliary steam supply is operational and de-aerated feedwater at 105 is available. To avoid oxygen corrosion in the boiler, the use of de-aerated feedwater with a temperature of greater than 102 is recommended.

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9) Normal operation

During normal operation the pressure moves as a sliding pressure mode from around 90 kg/cm2g of 35% load to 255 kg/cm2g of 90% load. From 90% to 100% load it is operated with constant pressure. It is called as a modified sliding operation. The feedwater entered Economiser is sub-cooled condition and the sub-cooled water is changed to superheated steam in the furnace at normal operation. Dry mode operation applies to the load range from 35% load upto full load. Separator outlet temperature by detecting four temperature transmitters (TT,10HAH10CT101-CT104) is used for controlling the feedwater flow. Four(4) spring loaded safety valves(PSV,10HAH10AA101,102,103,104) are installed on the separator outlet links(10HAH10BR001A-D) to prevent from over-pressure. They have the same set pressure and temperature as 304.9 bar(g) and 431.5. The separated vent pipes from each riser pipe from the same separator are combined as one pipe, which is connected to the flash tank inlet manifold(10LCQ10BR502) via motorized shut-off valve(MOV,10HAD30AA541-AA544). See the P&ID No.T07073-XG02-PI-D003 for more detail layout of vent pipes. Other vent pipes(10HAH10BR501-504) from separator outlet connection pipe (10HAH10BR001A-D) also combine as one pipe. The pipe(10HAH10BR506) is also connected to the flash tank inlet manifold(10LCQ10BR502). The manifold is connected to the flash tank vent stack (10LCQ10BR501) . The vent pipes allow trapped air to be vented during hydraulic testing, boiler start-up and for vacuum breaking when blowing down and emptying the boiler. The common air release provides a convenient point for nitrogen gas injection for blanketing or inerting during periods of wet or dry storage respectively. An isolating(10HAH10AA201) and a screw down non-return valve(10HAH10AA202) are included for nitrogen supply isolation. A sample point incorporating a probe, and complete with isolating valves(10HAH10AA601, AA602) is provided for steam extraction and subsequent analysis. This is required to ensure that saturated/superheated steam quality is of suitable for the operating pressure. The sampling line is extracted from vent line(10HAH10BR505) of separator outlet connection pipe (10HAHBR001A-D). To comply with ASME SEC.1 design code requirements, separator outlet connection pipe is fitted with four(4) numbers of safety valve(PSV,10HAH10AA101,102,103,104). These valves are designed to be discharged over 65% BMCR 2.3.4 P&ID Drawing Title: Superheater System (Roof inlet link to LTSH outlet

connection pipe) Drawing Number: T07073-XG02-PI-D004 TCE.5146A-510-00-0615 Design Basis: IBR / ASME

System Purpose Transfer of superheated steam from separator tank(10HAD50BB033) to Furnace roof inlet header(10HAH12) through four connection pipes(10HAH10).

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Transfer of superheated steam from Furnace roof inlet header to Roof outlet header(10HAH14) & Backpass inlet(upper) header(10HAH14). Transfer of superheated steam backpass inlet(upper) header to outlet(lower) header(10HAH18) via extended side wall tube and backpass side wall tubes. Transfer of LTSH inlet header(10HAH20) to LTSH outlet header(10HAH30) via LTSHs horizontal tubes and vertical tubes.

Description of Drawing From the roof inlet headers(10HAH12), steam flows along with the furnace roof tubes to the roof outlet header. Furnace roof tubes are revealed to the furnace radiant area but outlet side is in the radiant and convection area. Furnace roof outlet header(10HAH14) is connected to the both backpass side wall inlet headers(10HAH14). The roof outlet header is located above backpass section and the header divides the rear backpass area as a backpass sidewall inlet header(10HAH14) and extended wall inlet header(10HAH14). The above two headers are connected by the medium of roof outlet header . Therefore the same condition of steam from roof outlet header distributes to the backpass sidewall inlet header and extended wall inlet header. Extended side wall is located nose outlet vestibule section. Backpass lower side wall headers(10HAH18) have drain branches, which are connected to the manifold(10LCQ10BR502) of in front of boiler flash tank(10LCQ20BB001). Motorized shutoff valve(MOV,10HAH20AA441) and manual shutoff valve(10HAH20AA401) are installed at the common drain line. This drain valve(MOV,10HAH20AA441) can be closed when separator pressure reaches 3.5 bar(a). But the set pressure can be raise to satisfy no condensate water remains in the backpass header. The manual shut-off valve is always open condition except MOV maintenance. The steam flows from common header, roof outlet header, backpass side wall inlet header (10HAH14) and extended side wall inlet header(10HAH14), to backpass lower side wall outlet header(10HAH18) and backpass front wall lower header(10HAH18), which headers are combined as one header. But there is a extended wall outlet header(10HAH17) between roof outlet header and backpass lower front header. The extended outlet link (10HAH17) connects between two headers. The steam which flows down to the backpass side lower header goes to the LTSH(primary superheater) inlet header(10HAH20), which located in the bottom of backpass rear wall, adjacent to the backpass sidewall lower header. Through the LTSH tubes the steam heated more and goes to the LTSH outlet header(10HAH30) via LTSH horizontal(10HAH22) and pendent tubes(10HAH25). Metal temperature elements(TE,10HAH25CT001-CT033) for permanent are attached on the unheated tube surface at LTSH outlet section to check the stub metal temperature. 2.3.5 P&ID Drawing Title: Superheater System (LTSH outlet connection pipe to Panel

SH Outlet connection pipe) Drawing Number: T07073-XG02-PI-D005 TCE.5146A-510-00-0616 Design Basis: IBR / ASME

System Purpose The primary superheater(LTSH) outlet connection pipe(10HAH40) reaches to the Panel SH inlet header(10HAH42). Between two SH sections the long pipes provide an ideal location for

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the first stage attemperators. The length is long enough to be mixed completely of the injected spraywater with the superheated steam before entry to the Panel superheater(10HAH45). The primary superheater outlet steam temperature is measured for control and monitoring purposes in each attemperator inlet pipe(10HAH40) using temperature transmitters (TT,10HAH40CT101-104). The measurements are used by the DCS to provide redundant inputs for the steam temperature control system. The temperatures are transmitted to those of the inlet measurements. To reduce the steam temperature entering the panel superheater, spray water is added in the connecting pipes (10HAH40) between the primary SH outlet and the panel SH inlet. The source of this water is economiser inlet. The flow is sensed by a venturi type flow element that generates a differential pressure. A pressure differential is converted as a measured differential into a 4-20mA analogue signal as an input to the DCS. As the flow conditions do not necessarily match the element design parameters, compensation for pressure and temperature deviations is required. The temperature transmitter(TT,10LAB50CT101/2), and the pressure transmitter (PT,10LAB50CP101/2) which is located at the feedwater line provide the required inputs to the DCS for compensation of the spray flow. The temperature transmitters(TT,10HAH40CT101-8) send temperature values as an analogue inputs to DCS to reduce the steam temperature difference which is input in the control logic. The detected temperature values from the upstream transmitters (TT,10HAH40CT101/2/3/4) and downstream transmitters(TT,10HAH40CT105/6/7/8) of desuperheating stations are sent to the DCS to be compared with input value. Following flow measurement, the spray water line divides, with one line serving the 1st and 2nd stage attemperators on the A side(10LAE51BR002) of the boiler, and the other B side(10LAE52BR002) attemperators. Each spray station is made up of an actuated inlet isolating valve(10LAE51AA001,2 10LAE52AA001,2), modulating control valve (TCV,10LAE51AA071,072, 10LAE52AA071,072), and motorized discharge isolating valve (10LAE51AA041, 042, 10LAE52AA041,042). A double isolated drain valve(10LAE51AA401,2,3,4, 10LAE52AA401,2,3,4) between the motorized isolating and control valves is used to check for isolating valve leakage. The chosen pneumatic control valves are complete with intelligent I/P converters, fail fix devices, and valve position transmitters. 100% of redundancy spray station is provided at each spray line for emergency and for continuous spray use. On every installation it is necessary to ensure sufficient pressure exists to inject the spraywater into the steam stream. Therefore a study of the prevailing pressures related to boiler load is required. This generally shows that at the maximum spray flow there is insufficient feedwater pressure to inject the spray into the steam. This is of no consequence on boilers with dedicated spraywater booster pumps, feedwater pumps with additional spray booster stages, or conventional feedwater control valves at either the feed pump or feed heater discharge. The differential across the feed valves is adjusted by modulation of the valves to attain a suitable spraywater pressure. The steam line(10LAE50BR503) for sootblowing is extracted from LTSH outlet common line. The steam condition is enough for sootblowing and has enough superheated margin compared sootblowing steam. The warm-up line(10HAG15BR001) for maintaining the start-up system as a warm condition during normal operation is separated and associated with both desuperheater spray header(10LAE51/52BR002) and injected to the main stream(10HAH40).

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Each LTSH outlet header connection pipe(10HAH40) is fitted with an air release, which vents are common together to atmosphere through manual isolating valve(10HAH40AA501) and motorized isolating valve(MOV,10HAH40AA541). This allows trapped air to be vented during hydraulic testing, boiler start-up and for vacuum breaking when blowing down and emptying the boiler. The common air release provides a convenient point for nitrogen gas injection for blanketing or inerting during periods of wet or dry storage respectively. An isolating and screw down non-return valve(10HAH40AA201) are included for nitrogen supply isolation. The permanent metal temperature elements(TE,10HAH45CT001-CT012) for monitoring are attached on the unheated tube surface at Pendent SH outlet section to check the stub metal temperature. These temperature measurements are transmitted as converted to high level analogue inputs in transmitters. 2.3.6 P&ID Drawing Title: 2nd Attemperator and Final Superheater Drawing Number: T0073-XG02-PI-D006 TCE.5146A-510-00-0617 Design Basis: IBR / ASME

System Purpose Transfer of superheated steam from the panel superheater outlet by way of the second stage attemperators(10HAH50) to the final superheater inlet header(10HAH55). Collection of steam from the final superheater outlet header(10HAH60). Attemperation of the steam entering the final superheater to the conditions required to maintain the final steam temperature at the design condition over the specified load range. Description of Drawing The steam from panel SH outlet goes through 2nd stage attemperators and the temperature is adjusted as the required steam temperature to meet the final shperheater outlet temperature. As the steam flow has already been divided into two streams on exit from the panel superheater. The purpose of this connective configuration is to be considered the effect of combustion imbalance on the heat pick up of each steam stream at the tangential firing boiler characteristics, thereby attempting to naturally equalise the steam temperature at the outlet of each stream. Each final SH inlet connection pipe(10HAH50) is fitted with an air release, which when commoned together vents to atmosphere through manual isolating valve (10HAH40AA401) and motorized isolating valve(MOV,10HAH40AA441). This allows trapped air to be vented during hydraulic testing and boiler start-up. After suitable attemperation, the steam flow enters the final superheater inlet header, travels through the final SH loops(10HAH58) and emerges at the final superheater outlet header(10HAH60) with desired temperature, having extracted the required energy from the combustion process. The outlet connection pipe connects both steam streams and is across the entire boiler width as it is assumed that there will be two steam legs from the boiler to the turbine(supplied by others). The connection pipe of final superheater outlet header extends through the remote casing on each side of the boiler to provide a suitable connection for the turbine steam legs. To comply with ASME SEC.1 design code requirements, the superheater outlet connection pipe (supplied by others) is fitted with four(4) numbers of safety valve (PSV,10LBA11/12AA201,301). These valves are designed to be discharged over 35% BMCR. And ERVs which capacity is over 10% BMCR are settled. The combined capacity of the

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separator outlet connection pipe and superheater valves with ERV shall not be less than the maximum designed steaming capacity of the boiler. The valves discharge to atmosphere through pipework, stacks and silencers(SH outlet safety valves only) with suitable expansion provisions. Each valve has a body vent discharging to atmosphere. Silencer design is dependent on the international code requirements such as near and far field and steam releasing time is individually selected for the application. To reduce the steam temperature entering the final superheater, spray water is added in the connecting pipes between the panel SH outlet and the final SH inlet. The source of this water is a continuation of the piping supplying the 1st stage attemperators. Generally this will be the feed pump discharge (Economiser inlet). Each spray station is made up of an motorized inlet isolating valve(10LAE61AA041,042 10LAE62AA041,042), modulating control valve(TCV,10LAE61AA071,072, 10LAE62AA071, 072), and discharge isolating valves(10LAE61AA001/2, 10LAE62AA001/2). A double isolated drain between the motorized isolating and control valves is used to check for isolating valve leakage. The chosen pneumatic control valves are complete with intelligent I/P converters, fail fix devices, and valve position transmitters. Many valves such as temperature transmitter(TT,10LBA11/12CT101/2/3) thermowell (TW,10LBA11/12CT401/2), pressure transmitter(PT,10LBA11/12CP103/4/5/6), pressure tap(PP, 10LBA11/12CP401), safety valve(PSV,10LBA11/12AA201,301) and electric power operated valve(ERV,10LBA11/12AA192), are installed on the main steam pipe(supplied by others) for controlling, monitoring, and guarantee. Pressure tapping(PP,10LBA11/12CP401), complete with isolating valves(10LBA11/12 AA401/2), is available for the test gauge used during safety valve floating, and verification of inlet to superheater outlet pressure loss where this is a guarantee requirement. Start-up vent with two isolating valves(MOV,10LBA11/12AA541, 10LBA11/12AA001) and silencer is settled on the main steam line for air and steam release during boiler start-up. Motorized isolating valve(MOV,10LBA11/12AA541) for start-up vent is closed by DCS signal when boiler pressure( reaches approx. 3.5 to 5kg/cm2g. But when HP-Bypass system is used for boiler start-up the start-up vent closing set pressure can be changeable. Three pressure transmitters(PT,10LBA12CP104/5/6, PT,10LBA11CP104/5/6) on each final superheater outlet steam pipe are installed. These transmitters are not required for boiler/unit pressure control as the correct point for all pressure control is the main steam leg pressure adjacent to the turbine. Motor operated block valve on each side is installed on the final superheater outlet connection pipe by IBR code requirement. Main steam stop valve(MOV,10LBA12AA041) which is on the main steam line is provided for boiler itself hydraulic test and is used for isolating boiler from turbine. Thermo-elements are attached on the final SH outlet unheated tube(TE,10HAH58CT001-CT057) to detect the unheated tube surface metal temperature, which is regarded as the same of steam temperature. The temperatures are monitored continuously and sent to the DCS. Alarm and trip(MFT) setting value is set for protecting from furnace wall tube overheating. In case high temperature is detected through the signal from settled thermo-element alarm signal is shown on the monitor. If a few numbers of thermo-element detect high temperature than trip set value and the detected high temperatures do not return to usual temperature after some time delay, the boiler get the MFT signal by the DCS. Trip and alarm temperature is decided by considering allowable and design metal temperature and tube thickness and operational circumstances.

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2.3.7 P&ID Drawing Title: Reheater System Drawing Number: T07073-XG02-PI-D007 TCE.5146A-510-00-0618 Design Basis: IBR / ASME

System Purpose Transfer of steam from the inlet header through the pendent banks, intermediate header between pendent tubes, and outlet headers to the reheater outlet to the hot reheater legs Extraction of heat from the flue gases through predominantly radiant transfer in the pendant banks.

Description of Drawing Steam from the HP turbine exhaust is transferred to the boiler through pipework known as the Cold Reheat Pipes. These legs connect to the full width reheater inlet header(10HAJ10), and it is assumed that the pipes deliver a nominally equal quantity of steam. The pipe is fitted with a drip pot attached drains discharging to pit with double isolated valves(supplied by others). The steam temperature and pressure entering the reheater is measured for information and control purposes at each end of the inlet header using pressure transmitters(PT,10LCB31/32CP101) and temperature transmitters(TT,10LBC31/32CT101/2) . Two thermowells(TW,10LBC31/32 CT401/2) between reheater desuperheater in each pipe is installed for performance test performance. In addition a pressure test tap(PP,10LBC31/32CP401) is provided at each end of the inlet header for performance test purposes and for pressure measurement where pressure loss guarantees are required. The reheater steam flow is parallel with gas flow. Reheater inlet(10HAJ10) and outlet headers(10HAJ30) are over the roof tubes and between two headers intermediate header(10HAJ22) is located to mix the steam temperature and to get the even steam temperature at both ends of outlet header. The connection pipe from each side of header leads to the hot reheat legs that deliver reheated steam to the IP turbine inlet.

Burner tilt is used as a reheater temperature control and its inclination is 30 degrees. But for emergency attemperation, spray water system is installed at the cold reheat pipe. The spray water comes from Boiler feed water pump inter-stage step. Following flow measurement(FE,10LAF50CF001), the spray water line(10LAF50BR001) divides with two lines for two cold reheat pipes(supplied by others). Spray station is made up of a motorized inlet isolating valve(10LAF51/52AA041/2), modulating control valve(TCV,10LAF 51/52AA071/2) at both branches, and discharge isolating valve (10LAF51/52AA001/2). 100% of redundancy spray station is provided at both sides. A double isolated drain (10LAF51/52AA401/2/3/4) between the motorized isolating and control valves is used to check for isolating valve leakage. The chosen pneumatic control valves are complete with intelligent I/P converters, fail fix devices, and valve position transmitters. Double isolated air releases on the intermediate and outlet headers allow trapped air to be vented during hydraulic testing and boiler start-up. The common air release provides a convenient point for nitrogen gas injection for blanking or inerting during periods of wet or dry storage respectively. An isolating(10LBB20AA201) and screw down non-return valve(10LBB20AA202) are included for nitrogen supply isolation.

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In compliance with ASME SEC.1 design code requirements, the cold reheat pipes and hot reheat pipes are fitted with safety valves. These valves discharge 100% of the reheater design capacity. The valves discharge to atmosphere through pipework, stacks and silencers which is supplied only the lowest set pressure safety valve(PSV,10LBC31/32CP103) (where fitted) with suitable expansion provisions. Each valve has a body vent discharging to atmosphere. The discharge elbow and expansion chamber are drained to a hinged and lockable lid tundish, which in turn is connected to the boiler drains vessel vent. Silencer design is dependent on the international code requirements and contract specification such as near and far field and steam releasing time is individually selected for the application. 100% of Safety valve capacity is separated as 60% at cold reheat pipe(PSV,10LBC31/32AA101/2/3) and 40% at hot reheat pipe (PSV,10LBB11/12 AA101/2). At each end of the reheater outlet connection pipe, three temperature transmitters(TT, 10LBB11/12CT101/2/3) are installed for measurement and control of the final reheat steam temperature. One thermowell(TW,10LBB11/12CT401) at each end is available for performance test measurements. Pressure tappings(PP,10LBB11/12CP401), complete with isolating valves(10LBB11/12 AA303/4) are fitted on each end of the reheater outlet pipes(RHP is supplied by others). Pressure tapping is available for the test gauge used during safety valve floating, and verification of inlet to reheater outlet pressure loss where this is a guarantee requirement. Thermo-elements are attached on the intermediate header inlet tube stub(TE,10HAJ20CT001-052) and final RH outlet unheated tube(TE,10HAJ25CT020-043) to detect the unheated tube surface metal temperature, which is regarded as the same of steam temperature. The temperatures are monitored continuously and sent to the DCS. The alarm and trip set values is used by the thermo-element temperature at the final RH outlet tube stub. Alarm and trip(MFT) setting value is set for protecting from furnace wall tube overheating. In case high temperature is detected through the signal from settled thermo-element alarm signal is shown on the monitor. If a few numbers of thermo-element detect high temperature than trip set value and the detected high temperatures do not return to usual temperature after time delay, the boiler get the MFT signal by the DCS. Trip and alarm temperature is decided by considering allowable and design metal temperature and tube thickness and operational circumstances. 2.3.9 P&ID Drawing Title: Boiler Drain and Vent System Drawing Number: T07073-XG02-PI-D009 TCE.5146-510-00-0620 Design Basis: IBR / ASME

System Purpose Collection of boiler drains and vents, soot blowers, steam coil air heater drains. Collection of boiler water by separator storage tank lowering during start-up. Discharge of condensate to condensate receiving tank. Discharge of condensate water in the tank to condenser via condensate drain transfer pump. Discharge of flash steam to safe level. Discharge of steam air heater to flash tank

Description of Drawing Each boiler is provided with a complete drain system.

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The boiler start-up flash and blowdown tank(10LCQ20BB001) is a vertical cylindrical type vessel located at a level to have a gravity that the water in the flash tank drops in the condensate receiving tank(10LCQ40BB001). The flash tank is also provided with its own drain manifold connections(10LCQ20BR401/2) from different sources and a vent stack(10LCQ10BR501). Many vent pipes from boiler proper are joined into a single line near the flash tank vent stack and the steam in the single line discharges to the vent stack. The discharged steam is separated by flashing as steam and water. An anti-siphon pipe(10LCQ30BR401) is provided to ensure that the overflow pipework maintains a level of water at all times. Emergency drain line(10LCQ30BR402) is also provided at the bottom of the vessel with isolating valve(10LCQ30AA401) to dump directly at the sump area. Flash tank is designed to accumulate the furnace swelling flow during start-up and overflow drain from storage tank during wet mode operation by WR and/or ZR control valve. The tank receives drains from Gas airheater sootblower lines, boiler sootblower lines, auxiliary steam lines, and SCAH drain line and water wall headers. Drains flow from sootblowing system and SCAH drain line drain during normal operation and especially boiler proper drains during start-up and low load operation. To prepare the light-off and to fill up the boiler water the following conditions should be ready. - Backpass(MOV,10HAH12/18/20AA441), superheater(MOV,10HAH55AA441), and reheater

drain valves are open, and all vent valves(separator outlet : MOV,10HAH10AA541, 10HAD30AA541/2/3/4, furnace roof outlet :MOV,10HAH14AA541, panel SH inlet : MOV,10HAH40AA541, final SH inlet :MOV,10HAH50AA541, start-up vent, MOV,10LBA11/12 AA541) are closed. The economizer(MOV,10LAB50AA441) and furnace wall drain valves(MOV,10HAD15/50AA441) are closed, and economizer vent valves(MOV,10HAC30 AA541) are open.

- Close economizer outlet vent valve 20 seconds later than detecting the economizer inlet water flow reaches over 10 ton/hr.

After light-off open the panel SH vent valve(MOV,10HAH40AA541), final SH vent valve (MOV,10HAH50AA541), start-up vent valve(MOV,10LBA11/12 AA541), and RH outlet vent valves. The backpass drain valve can be closed when separator pressure reaches 3.5 bar(a). But the set pressure can be raise to satisfy no condensate water remains in the backpass header. Close the RH outlet vent valves when RH pressure reaches 3.5 bar(a) The condensate receiving tank(10LCQ40BB001) is a horizontal type vessel, which is located under the flash tank(10LCQ20BB001) and it has a space below the tank to settle the drain transfer pump(10LCQ50AP001/2) on the ground. The condensate receiving tank receives the flash tank drain water. With attached level transmitter(LT,10LCQ40CL101) the detected drain water level is sent to the DCS and its normal water level is maintained by the funnel and the funnel line(10LCQ40BR401) is connected to the boiler sump area. One steam vent line(10LCQ40BR501) for condensate receiving tank is connected over the flash tank vent stack. Installed two(2) drain transfer pump lead the drain water to the condenser. Drain transfer pump operation control logic is input in the logic so that it is operated automatically by the water level deviation. The pump capacity is 50%load and it is considered the worst condition at the start-up period. During the boiler start up drains from separator storage tank, furnace headers and auxiliary steam discharge saturated water and steam to the boiler flash tank. A large quantity of flash steam needs to be vented to atmosphere through vent stack during start up which will cause a great deal of noise pollution. Hence, to reduce the sound level to acceptable limits of the plant, a noise reducing device is provided in the vent stack.

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All the drain lines to the boiler drains tank must be provided with an adequate slope (1:100 boiler hot) to ensure complete drainage back to the drains vessel. The vessel must be designed to accept the total flow of drains that could occur during operation, and the possibility that they may be operated at full pressure and temperature. Steam Airheater is operated to meet the required average cold end metal temperature of Gas Airheater(10HLD10/20). The average cold end metal temperature is set to prevent GAHs cold end side from erosion due to sulphuric acid dew point. After heat up the primary and secondary air which pass through the SAHs the Condensate water drains to the SAH drain tank. The drained water goes to the flash tank(10LCQ20BB001) via SAH drain pump(10HLC80AP001/2). The pump capacity covers the drain water 100% of drain water and another is for stand-by. The tank level is controlled by the control valve(LCV,10HLC90CP441) which receives the signal from the level transmitters(LT,10HLC70CL101/2) The minimum recirculation line for drain pump is supplied to protect the motor cavitations. The strainer is inserted in the pump suction line not to enter the debris to the pump. It may be removed after start-up or in some time operation.

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2.4 PIPING AND INSTRUMENT DIAGRAMS DESCRIPTIONS AIR AND GAS Each diagram in the design series has an associated diagram description, which has a System Purpose and Description of the P&ID 2.4.1 P&ID Drawing Title: Combustion Air & Flue Gas System Coal feeder & Pulverizer System Primary air Sealing & Cooling air System Drawing Number: T07073-XG02-PI-D010/11/12/17/18 TCE.5146A-510-00-0622/623/628/629 Design Basis: NFPA 85 and DOOSAN in-house Design Rules System Purpose Provision of Total Air at the required temperature, pressure, and flow for combustion and pulverised fuel (PF) transport purposes. Heating of ambient air to the required temperature for meeting of cold end of gas air heater. Provision of suitable isolation of system components during start up, shutdown, and on fault conditions. Crossover duct between Secondary air duct. Provision of primary air at the required temperature, pressure, and flow for coal drying and pulverised fuel (PF) transport purposes. Removal of useful energy from the flue gas to heat the primary air and secondary air. Provision of seal air at required pressure, and flow for mill and feeder. Provision of code compliant ducts for the transport of primary and seal air. Heating of ambient air to the required temperature for dewpoint prevention in regenerative gas/airheaters, boiler start up. Removal of useful energy from the flue gas to heat the primary and secondary air. Provision of suitable isolation of system components during start up, shutdown, and on fault conditions. Provision of secondary air for combustion. Extraction of useful heat from the flue gas by water walls, super heaters, reheaters and economisers. Description of Drawing The referenced drawing depicts a typical two stream draught plant arrangement, variable pitch (VP) axial flow Forced Draught (FD) fans(10HLB10/20AN001) and steam airheaters (SAH,10HLC51/52). It caters for ambient air temperatures in the range 4 OC to plus 45OC. The steam airheater(10HLC51/52) is placed in a downstream of FD Fan and upstream of Gas Air Heater(GAH,10HLD10/20), where air heating is required for dewpoint protection of the GAH at low ambient temperature. Each FD fan draws air directly from atmosphere through silencer(10HLB10/20BS001). The dampers(MZ,10HLA10/20AA041) which located between Fans and SAHs are Multi vane, modulating type with electro-motor actuation. Steam air heating is required principally when low ambient air temperatures are experienced, but will also be necessary when operating with top feed heaters out of service, during oil firing and boiler start-ups. The ambient air inlet is fitted with Flat mesh screens to inhibit foreign particles entering the respective ducts. A silencer is provided in the FD fan total air inlet duct, the design of the

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silencer(10HLB10/20BS001) being dependent on the Noise requirements such as near and far field and is individually selected for the application. The temperature of total air to the FD fan(10HLB10/20AN001) is measured for airflow measurement correction and for monitoring the boiler performance. One transmitter(TT,10HLA is fitted with duplex thermocouple providing redundant inputs to the DCS, the measurement being transmitted as converted to high-level analogue inputs in transmitters. A pressure tapping point with analogue transmitter(PT,10HLB10/20CP101) is included for monitoring the FD fan air inlet pressure by the DCS, and hence to the Central Control Room (CCR). The airflow is measured to account the total combustion air entering into the system with aerofoil type(FE,10HLA30/40CF001) which is installed both downstream of hot secondary air duct for FD Fan and venture type(FE,10HFE51CF001) which is at the pulverizer inlet duct for PA Fan(10HFE15/25AN001). Further, it is also used for fan stall prevention. The measured airflow is temperature and pressure corrected to design conditions. This signal, after linearization, is characterised into the axial flow fan stall line, which is used to inhibit the blade pitch from increasing on both the stalling fan and its parallel partner (if operating) or if the pressure rise continues and crosses the upper limit, the final control element on both fans will be tripped to manual, and the vane pitch reduced until the stall condition is cleared. The pressure differential transmitters(PDT,10HFE15/25CP101/2) for PA Fan and FD fan (PDT,10HLB10/20CP101/2) that sensed the differential pressure and convert the measured differential into 4-20 mA analogue signals as an input to the DCS and a further pressure differential transmitter measures and transmits the static head rise across the fan. A pressure tapping point with analogue transmitter(PT,10HLA10/20CP101) is included for performance monitoring of the FD fan and transmitting the FD fan air outlet pressure to the DCS. This measurement may also be used to inhibit start of second fan if

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