Nov 21, 2013 1

Boiler Water Chemistry

Best Practices - A key to success in Super Critical Boilers

By: Team NTPC

Nov 21, 2013 2

NTPC Overview

OT – Introduction

Oxygen Dosing System Details

Operation and Control

AVT v/s OT – Data Comparison

AVT v/s OT - Benefits

Results and Conclusion

PRESENTATION OUTLINE

Nov 21, 2013 3

Our Vision

““To be the worldTo be the world’’s s largest and best largest and best power producer, power producer, powering Indiapowering India’’s s

growthgrowth””

Nov 21, 2013 4

Today ~41 GW*

Coal Gas Nuclear Hydro Renewables

2032~ 128 GW

Planning for Accelerated Growth

Capacity under construction: ~20 GW

* 10 MW Solar PV Projects

Nov 21, 2013 5

NTPC’s Growth Journey

1133320249

41794*

1975

NTPC incorporated

1997

Became a NavratnaCompany

2004

Listed on Indian Stock Exchanges(GoI holding

89.5%)

2010

• Became a MaharatnaCompany

• GOI divested 5% equity

1982

First 200 MW unit

commissioned

2013

• GOI further divested 9.5% equity

*10 MW Solar PV

Nov 21, 2013 6

Note: Capacity includes capacity under construction; Map not to scale

RIHAND(3,000 MW)RIHAND(3,000 MW)SINGRAULI

(2,000 MW)SINGRAULI(2,000 MW)

FARIDABAD(430 MW)FARIDABAD(430 MW)

DADRI(817 MW)DADRI(817 MW)

NCTPP(1,820 MW)NCTPP(2,310 MW)

ANTA(413 MW)ANTA(413 MW)

AURAIYA(652 MW)AURAIYA(652 MW)

UNCHAHAR(1,050 MW)UNCHAHAR(1,050 MW)

TANDA(440 MW)TANDA(440 MW)

KAHALGAON(2,340 MW)KAHALGAON(2,340 MW)

FARAKKA(2,100 MW)FARAKKA(2,100 MW)

KORBA(2,600 MW)KORBA(2,600 MW)

VINDHYACHAL(4,260 MW)VINDHYACHAL(4,260 MW)GANDHAR

(648 MW)GANDHAR(648 MW)

KAWAS(645 MW)KAWAS(645 MW) TALCHER KANIHA

(3,000 MW)TALCHER KANIHA

(3,000 MW)

RAMAGUNDAM(2,600 MW)RAMAGUNDAM(2,600 MW)

SIMHADRI(2,000 MW)SIMHADRI(2,000 MW)

KAYAMKULAM(350 MW)KAYAMKULAM(350 MW)

TALCHER Thermal(460 MW)TALCHER Thermal

(460 MW)

KOLDAM(800 MW)KOLDAM(800 MW)

TAPOVAN VISHNUGAD(520 MW)TAPOVAN VISHNUGAD

(520 MW)

LOHARINAG PALA(600 MW)LOHARINAG PALA

(600 MW)

SIPAT2,980 MWSIPAT2,980 MW

BARH3,300 MWBARH3,300 MW

BTPS(705 MW)BTPS(705 MW)

BONGAIGAON(750 MW)BONGAIGAON(750 MW)

VALLUR(1,500 MW)VALLUR(1,500 MW)

MAUDA(1,000 MW)MAUDA(1,000 MW)

RGPPL(1480 MW)

RGPPL(1480 MW)

IGSTPP(1,500 MW)IGSTPP(1,500 MW)

DURGAPUR(120 MW)DURGAPUR(120 MW)

BHILAI574 MWBHILAI574 MW

ROURKELA(120 MW)ROURKELA(120 MW)

NABINAGAR(1,000 MW)NABINAGAR(1,000 MW)

GAS POWER STATIONS

COAL POWER STATIONONGOING HYDRO POWER PROJECTS

ONGOING THERMAL PROJECTS

Pan India Presence

No. of plants

Capacity MW Share

NTPC OwnedCoal 16 32,355 77.42%

Gas/Liquid fuel 7 3955 9.46%Solar 2 10 0.02 %

Sub-Total 25 36,320 86.9%Owned by JVs

Coal 6 3534 8.46%Gas 1 1940 4.64%

Sub-Total 7 5474 13.1%Total 32 41,794 100%

Nov 21, 2013 7

Implementing high efficiency technology

Sustainable Power Development

Hydro, Renewable & Nuclear Energy forays

1499 MW hydro capacity under construction Developing Wind and Solar capacities – 1000 MW by 2017 Anushakti Vidhyut Nigam Ltd. - JV company formed with NPCIL for nuclear

power development - NTPC(49% ) & NPCIL( 51%) – 14 GW by 20

Nov 21, 2013 8

Investment of more than 1% of PAT for R&D Activities and Climate Change studies

ECBC (Energy Conservation Building Code) compliant building

ISO/NABL 17025 Certified Labs, CBB certification

Research & Technology Development

Focus Areas

Efficiency & Availability Improvement and Cost Reduction

Renewables and Alternate Energy

Climate Change and Environment

Scientific Support to Stations

Nov 21, 2013 9

Oxygenated treatment – Feed water treatment or conditioning.

Injection of High purity oxygen gas at CPU & Deaerator outlet

Conversion of Fe3O4 (Magnetite) to hydrated FeOOHand Fe2O3 (Hematite).

Hydrated FeOOH and/or Fe2O3 block the pores in the magnetite layer and forms a more adherent protective layer and reduces the migration of iron

Prevents flow accelerated corrosion (FAC).

OXYGENATED TREATMENT (OT)

Nov 21, 2013 10

FEED WATER SPECIFICATION

S.N Parameter Units

Normal OperationDuringStart upAlkaline

water Treatment

Oxygenated Treatment

1 pH Min 9.0 8-8.5 Min 9.0

2 ACC, ms/cm ms/cm Max 0.2 <0.15 Max 0.5

3 D O ppb < 5 30-150 Max 100

4 Iron ppb < 2 < 2 < 20

5 Sodium ppb < 2 < 2 < 10

6 Silica ppb <10 < 10 < 30

7 Turbidity NTU <2 < 2 <5

Nov 21, 2013 11

STEAM PARAMETERS LIMITS

Parameter NormalAction 1 (2 weeks per year)

Action 2(2 days per

year)

Action 3(8 hours per year)

Immediate shut down

ACC, ms/cm<0.15 >0.2 >0.3 >0.6 >2

Silica, ppb 10 >10 >30 >40 >50

Sodium, ppb <3 >3 >6 >12 >24

Chloride, ppb <3 >3 >6 >12 >24

Nov 21, 2013 12

STEAM WATER ANALYSIS SYSTEM (SWAS)

Online Monitors:

S.No System Type of measurement1 Make up DM water SP.COND., CATION

CONDUCTIVITY (ACC)

2 CEP discharge pH, ACC, Na, DO, SP.COND.,

3 CPU Outlet pH, ACC, Na, SILICA, SP.COND.,

4 Deaerator outlet DO

5 Feed water at economizer inlet

pH, ACC, COND., SILICA

Nov 21, 2013 13

STEAM WATER ANALYSIS SYSTEM (SWAS) contd….

S.No System Type of measurement6 Separator outlet steam ACC, SP.COND., SILICA

7 Main steam pH, ACC, Na, SILICA, SP.COND.,

8 Water separation storage tank of boiler

Cation conductivity (ACC)

9 Reheated steam Cation conductivity (ACC)

Nov 21, 2013 14

STARTUP, OPERATION AND SHUTDOWN

Stop oxygen feed at least one hour before shutdown

Increase ammonia feed rate to achieve a pH > 9.0

Open Deaerator vents

Nov 21, 2013 15

Normal Running condition

During shut downAmmonia vaporise to upper layer

During shut downDissolution of iron in low pH water

Crud load during start up

Water wall tube deposits from feed iron transport

CRUD LOAD DURING START UP

Nov 21, 2013 16

BOILER PROTECTIVE LAYER

Migration of Fe2+ to fluid boundary layer FeOOH/Fe2O3 block pores lowering Fe2+ migration

AVT OT

Nov 21, 2013 17

The piping material is of SS 316

OXYGEN DOSING SYSTEM

Pressure Regulating Valve

Flow Control Valves

Gas Cylinders

Motorised Valves

Nov 21, 2013 18

Five gas cylinders charge at once at regulated pressure 42 ksc

The safety valve operates, if gas pressure is >50ksc.

Four dosing lines - two each at D/A and CPU outlet

Dosing line with one Motorised (MOV) and one Flow control

valve (FCV)

The MOV is fully opened and gas flow is controlled by FCV.

OPERATION AND CONTROL

Nov 21, 2013 19

The injection control isautomatically adjusted by

Condensate water flow and Feed DO.

OXYGEN DOSING OPERATION

Nov 21, 2013 20

CONVERSION TO OT - ACTIVITIES

Pre OT Activities

Instruments Installation – DO meter, ACC

Install Sampling lines – ACC, pH, K at each CPU Vessel

Replacement of De-aerator O/L sample line by Feed water line to analyzer for round the clock monitoring of Feed DO.

PORTABLE D.O. METER

PORTABLE A.C.C. METER

Nov 21, 2013 21

CPU Availability 100% CPU availability Formal training to Shift –Chemist regarding CPU operation.

Training Session The training session for operators regarding OT & Actions to be taken during start-up, shut-down and in normal

operation.

Database Recording and observing parameters for three months before

start comprising Feed & CEP DOMonitoring of ACC of cycle chemistry under AVT condition to

ensure the readiness of boilers for conversion to OT.

OT CONVERSION - ACTIVITIES

Nov 21, 2013 22

U#3, Feed Water D.O. in AVT

0.00

5.00

10.00

15.00

20.00

25.00

01.01

.2013

10.01

.2013

12.01

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19.01

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24.01

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31.01

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06.02

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08.02

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10.02

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13.02

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15.02

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19.02

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20.02

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25.02

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26.02

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Day(s)

Diss

olve

d O

xyge

n (p

pb)

Feed Water

U#3, Feed and MS ACC value in AVT

0.00

0.05

0.10

0.15

0.20

04-12

-2012

08-12

-2012

13-12

-201

225

-12-20

1201

.01.201

310

.01.201

319

.01.201

324

.01.201

331

.01.201

304

.02.201

309

.02.201

313

.02.201

318

.02.201

325

.02.201

326

.02.201

3

Day(s)

ACC

(uS/

cm)

Feed WaterMain Steam

DO/ACC DATA TREND BEFORE OT

U#2, Feed Water D.O. in AVT

0.00

5.00

10.00

15.00

20.00

25.00

11-12

-2012

18-12

-2012

25-12

-2012

01-01

-2013

08-01

-2013

15-01

-2013

22-01

-2013

29-01

-2013

05-02

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12-02

-2013

19-02

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26-02

-2013

05-03

-2013

Day(s)

Dis

solv

ed O

xyge

n (p

pb)

Feed Water

U#2, Feed and MS ACC value in AVT

0.00

0.05

0.10

0.15

0.20

11-12

-2012

13-12

-2012

20-12

-2012

29-12

-2012

01.01

.2013

08.01

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15.01

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21.01

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28.01

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04.02

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11.02

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18.02

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25.02

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02.03

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04.03

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08.03

.2013

Day(s)

ACC

(uS/

cm)

Feed WaterMain Steam

Nov 21, 2013 23

COMMISSIONING ACTIVITIES.

Instrument Checking Calibration of all pressure gauges and transmitters

Checking of following for protection of FCV.

• Pressure regulating valve & set at 42ksc

• Pressure safety valve & set at 50ksc.

Valve Operation Checking of all MOVs and FCVs for local and remote

operation.

Leak Detection Test Pressurizing of dosing lines

Checking for any gas leakage at every weld-joint.

Nov 21, 2013 24

BALLOONBALLOON

GAS FLOW MEASUREMENT & FCV SETTING

Most important activity as dosing of oxygen gas with in limit is dependent on FCV setting.

Measurement of gas flow using Balloons (spherical and cylindrical) and a connector

Nov 21, 2013 25

Based on DO data of different units, decision to start OT first in one unit.

Steady rate of passivation, [target value of DO is set max. 80 ppb (range 30 -150 ppb)].

Initially operation at 9.0 to 9.2 pH and then slowly and steadily convert to lower value by monitoring Feed ACC.

Afterwards operate DO level at 80 -110 ppb range.

CONVERSION TO OT - GUIDELINES

Nov 21, 2013 26

CONVERSION TO OT – Case study

Case study 1: Oxygen dosing started The D/A vents fully closed and oxygen dosed at CPU O/L. Feed DO started increasing from 6.8 ppb to 20 ppb within 10hrs After two days, Feed DO attained 20-40 ppb range only Additionally the dosing carried out at D/A O/L as minor passing

was observed from D/A vent. After that, DO increased to 65-80 ppb. The target value achieved within 5days of start of OT. In the second phase, operation started at DO level of 80-110

ppb.

Nov 21, 2013 27

U#3 Feed Water D. O. in initial month (March, 2013)

0.00

20.00

40.00

60.00

80.00

100.00

120.00

02.03

.2013

04.03

.2013

05.03

.2013

05.03

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07.03

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08.03

.2013

11.03

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14.03

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15.03

.2013

16.03

.2013

25.03

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01.04

.2013

Days

Disslov

ed O

xyge

n (ppb

)

U#3 Feed Water D. O. trend upto July, 2013

0.00

20.00

40.00

60.00

80.00

100.00

120.00

140.00

02.03

.2013

05.03

.2013

07.03

.2013

11.03

.2013

15.03

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18.03

.2013

01.04

.2013

29.04

.2013

11.05

.2013

18.05

.2013

20.05

.2013

27.05

.2013

17.06

.2013

08.07

.2013

Days

Dissl

oved

Oxy

gen

(ppb

)

CONVERSION TO OT – Case Study

Nov 21, 2013 28

CONVERSION TO OT – Case Study

Case study 2:

Oxygen dosing started

The D/A vents fully closed

Oxygen dosed at CPU O/L & D/A outlet simultaneously

Feed DO started increasing from 9.2 ppb to 40 ppb within 48hrs

After three days, Feed DO attained 50 ppb range

The target value achieved within 5days of start of OT.

In the second phase, operation started at DO level of 80-110 ppb.

Nov 21, 2013 29

U#2 Feed Water D. O. trend in March, 2013

0.0

20.0

40.0

60.0

80.0

100.0

15-Mar-

13

17-Mar-

13

19-Mar-

13

21-Mar-

13

23-Mar-

13

25-Mar-

13

27-Mar-

13

29-Mar-

13

31-Mar-

13

Days

Disslov

ed Oxy

gen (ppb

)

U#2 Feed Water D. O. trend upto 29th July, 2013

0.00

20.00

40.00

60.00

80.00

100.00

120.00

15.03

.2013

16.03

.2013

25.03

.2013

15.04

.2013

29.04

.2013

13.05

.2013

20.05

.2013

27.05

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17.06

.2013

27.06

.2013

Days

Disslov

ed O

xyge

n (p

pb)

CONVERSION TO OT – Case Study

Nov 21, 2013 30

U#3, Avg ACC value

0.00

0.05

0.10

0.15

0.20

Dec'12

Jan'1

3

Feb'1

3

Mar'13

Apr'13

May'13

Jun'1

3

Month

ACC

(uS/

cm)

Feed WaterMain Steam

AVT v/s OT – DATA COMPARISON

U#2, Avg ACC value

0.00

0.05

0.10

0.15

0.20

Dec'12

Jan'1

3

Feb'13

Mar'13

Apr'13

May'13

Jun'1

3

Month

AC

C (u

S/cm

)

Feed WaterMain Steam

Feed and Main Steam ACC The Feed and MS A.C.C. values of OT - almost stable (0.09-

0.10 μS/cm)

Values are less in comparison to AVT (0.2 μS/cm)

Nov 21, 2013 31

U#3, Avg Iron value

012345678

Dec'12

Jan'1

3Feb

'13Mar'

13Apr'

13May

'13Ju

n'13

Jul'13

Aug'13

Month

Iron

(ppb

)

Feed WaterMain steam

U#2, Avg Iron value

012345678

Dec'12

Jan'1

3Fe

b'13

Mar'13

Apr'13

May'13

Jun'1

3Ju

l'13Aug

'13

Month

Iron

(ppb

)

Feed WaterMain steam

Feed and Main Steam Iron values Rise in Feed and MS iron values of OT at the start (3-4 ppb)

and decrease afterwards (2-3 ppb)

Values lesser in comparison to AVT (more than 5 ppb).

AVT V/S OT – DATA COMPARISON

Nov 21, 2013 32

BENEFITS of OT over AVT50% increase in CPU load

AVT - 240000 M3 load

OT - 360000 M3 load

Environmental benefits and Safety

Increase in CPU loading results decrease in regeneration frequency.

Reduction in spent regenerant waste. Environmental benefit.

Reduction in Ammonia consumption by 64%

Reduction in DM Makeup (Cyclic)

Cyclic make up reduction ( less than 1%)

AVT- D/A vents open; OT - close/throttle the vent

Nov 21, 2013 33

Reduction of chemical cost :

ChemicalConsumption (Ltr)AVT OT

Cost (in Rs) AVT OT

Ammonia 1100 400 39600 14400

Oxygen (No. of Cyl.) -- 15 -- 1950

Total Cost ( in Rs) 39600 16350

MONTHLY SAVINGS (in Rs): 39600-16350 = 23250/-

(monthly average values of chemicals consumed is taken, and current price is considered)

BENEFITS of OT over AVT

Nov 21, 2013 34

CPU- RegenerationReduction in monthly consumption of HCl & NaOH as CPU loading is increased by 50%.

ChemicalCONSUMPTION (Ltr)

AVT OT Cost (in Rs)

AVT OT ACID (HCl) 31 MT 20 MT 48050/- 31000/-

ALKALI (NaOH) 8 MT 5 MT 210224/- 131390/-

TOTAL COST (in Rs) 258274/- 162390/-

Total monthly savings (in Rs.) = 23250.00 + 95884.00 = Rs. 119134/-.

BENEFITS of OT over AVT

* Cost of HCl is taken as Rs.1550/MT and Alkali as Rs. 26278/mt. thus monthly savings of Rs. 95884/-

Nov 21, 2013 35

RESULTS AND CONCLUSIONS

The judicious and efficient CPU operation helps to maintain stringent Feed -water quality.

Increase in the Feed DO range to 80-110ppb, and maintaining ACC in the range of 0.09-0.11 S/cm.

Stabilization of steam water cycle chemistry - evident from the analytical parameters & CPU cleaning process (hematite layer conversion)

Success factor of conversion to OT will be more promising after physical inspection of boiler components

Nov 21, 2013 36

TRANSFORMING LIVES