1 Cairo Electricity Production Company (CEPC) Egypt:18 March. 2009 Eng.:Ahmed Emam - CEPC Chairman...

1

Cairo Electricity Production Company (CEPC)

Egypt : 18 March. 2009

Eng. : Ahmed Emam - CEPC Chairman

The Impact of Chemical Additives of fuel to improve Generating Plants’ performance

WEC-PGP

The Impact of Chemical Additives of fuel to improve Generating Plants’ performance

WEC-PGP

2

Contents

• CEPC Overview.

• CEPC Statistics.

• Introduction for heavy fuel firing.

• Cairo West case study

3

CEPC Overview

4


• CEPC is a state-owned firm, affiliated to the Egyptian Electricity Holding Company (EEHC).

• CEPC has a total installed capacity of 4,605 MW, representing 20% of the total installed capacity connected to the unified national grid.

• In all power plants, CEPC has a group of workshops that are adequately equipped to serve the maintenance activities of these power plants. CEPC has its own qualified and skilled staff for maintenance and operation of CEPC power plants.

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• CEPC has established a central workshop at 10th of Ramadan city to be specialized in the manufacturing of steam boilers equipment for CEPC and other EEHC affiliated Companies.

• All the power generation units owned by CEPC are environmentally friendly and operate under the limits allowed by the Egyptian environmental law.

• CEPC objectives cover production, management, operation, maintenance, and sale of electric power from its owned power plants. Furthermore, implementation of new power plants projects as per EEHC plan, and conduction of researches and studies within CEPC generation zone.

6

Shoubra El-khaima Power Station

Cairo West Power Station

Cairo South Power Station

Cairo North Power Station

Wadi Hoff Power Station

CEPC Power StationsCEPC Power Stations

Nil

e R

ive

r

Ismalia C

anal

7

CEPC Power StationsCEPC Power Stations

StationsShoubra El-Khaima

Cairo West Cairo South Cairo NorthWadi Hof

Type Steam SteamCombined

CycleCombined

CycleGas

Units

No.4 x 315

4 x 87.5

2 x 330

Com14 x 60 St 3 x 110 Gas

Com21 x 55 St 1 x 110 Gas

Com1 2 x250 Gas1 x250 St

Com22 x250 Gas1 x250 St

3 x 33.3

Installed Capacity

(MW)1260 1010 MW 735 MW 1500 MW 100 MW

Comm.

Date

1984 & 85

& 88

1966 & 79 & 94

1957 & 65 & 89 & 94

2004 & 06 & 08

1985

8

CEPC Statistics

9

CEPC Generated Energy Development (KWH)

1718218492 18016

21736 22557

25485 25114

0

5000

10000

15000

20000

25000

30000

2001

/200

2

2002

/200

3

2003

/200

4

2004

/200

5

2005

/200

6

2006

/200

7

2007

/200

8

YEAR

Million KWH

10

CEPC Distributed Energy by Plants2007-2008

29%Cairo North

2%Wadi Hof 29%

Shobra

23%Cairo West

17%Cairo South

11

CEPC Generation Supply Mix 2007/2008

Steam, 52.1 %C.Cycle, 34.1%

S.Cycle, 13.8%

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CEPC Power Plants Statistics

Installed Capacity

Max LoadCapacity Factor

Load Factor

Used Factor

Availability Reliability Fuel Cons.

(MW) (MW) % % % % % gm/KWH

2001/2002 3181 2957 61.31 66.33 93.94 87.99 98.61 222.59

2002/2003 3181 3033 66.37 69.6 95.35 92.47 98.99 224.33

2003/2004 3181 3017 64.48 67.98 94.84 91.30 99.41 221.58

2004/2005 3681 3575 67.41 69.41 97.12 92.01 98.45 232.42

2005/2006 4355 4069 67.97 63.28 93.76 91.59 98.34 225.16

2006/2007 4355 4161 66.80 69.92 95.55 90.51 98.96 218.74

2007/2008 4355 4078 65.65 70.11 93.64 87.35 99.32 218.93

Year

13

Fuel Type Consumption2007/2008

Solar0.010%

N.gas86.90%

Mazoat13.09%

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Percentage Of Nat. Gas & Mazout per Total Fuel

0

10

20

30

40

50

60

70

80

90

100

2001/2002 2002/2003 2003/2004 2004/2005 2005/2006 2006/2007 2007/2008

YEAR

%

Gas%

Mazout%

15

Cairo West Mazout Consumption

82.3 4858 3180

353166

535200

645500

585000

0

100000

200000

300000

400000

500000

600000

700000

YEAR

To

n M

azo

ut

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Introduction for Heavy Fuel Firing

17

Introduction

• Today, about 90% of the total energy production all over the world is provided by combustion of fossil fuels. Unfortunately, hydrocarbon combustion has a major impact on the global environment through the emission of CO2, which is a greenhouse gas.

• The increase in consumption of petroleum-derived liquids as fuel for transportation, electric power generation, heating, and process engineering is resulting in a reduction in the quality of residual oils that are becoming heavier. This quality reduction translates into lower heating values, but above all, into higher viscosity, as well as higher levels of asphaltenes, Conradson carbon, etc. At the same time, the world natural reserve of bituminous petroleum is estimated to be three times higher than that of regular fuel oils.

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• Combustion of heavy oils contain vanadium, sulfur, and sodium contents results in highly corrosive deposits. The slag produced during combustion has a low melting temperature and adheres to hot metal surfaces (450oC and above). Vanadium salts are extremely corrosive, since they dissolve the protective oxide film on the metal surface and then transport oxygen to the clean surface that corrodes.

• During combustion, such elements give rise to complex low-melting-point compounds. These sticky deposited materials capture ash, soot, and coke, which reduce the heat transfer and cause corrosion.

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Effects of Ash Deposition

• Slag build-up reduces the heat transfer from combustion into the water tubes.

• Even minor slag thickness reduce heat transfer significantly.

• This reduces steam temperature and steam production.

• To compensate, fuel consumption is increased.

• Loss of refractory is possible when severe slagging occurs.

• Results in lower “Heat Rate” (Tones Fuel/MW).

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Secondary Superheat Pipes

Before After

21

Furnace Bottom Pipes

Before After

22

Reheat Pipes

Before After

23

Primary Superheat Pipes

Before After

24

Cold End Corrosion

• Very detrimental as will corrode metal surfaces within the hot gas path if acid dew-point is achieved in the system.

• Collects fly ash therefore increases ash fouling rates, blocking passages in air heaters etc.

• Stack exit temperature run hotter

Reduces Efficiency.

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Gas/Air Heater Baskets

Before After

26

Gas/Air Heater Baskets

Before After

27

Various Methods to Prevent Boiler

Corrosion

i. Use of high quality fuel.

ii. Flue gas desulphurization.

iii. Use of chemical additives (applicable method).

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Main Effects of using Additives in Oil-Fired Boilers

A. Reduce emissions of SO3 and acid smut.

B. Minimize corrosion in air heaters, economizers, furnaces

and super heaters.

C. Reduce tube fouling.

D. Reduce flue gas opacity.

E. Prevent slagging and deposits.

F. Improve soot quality and reduce soot quantity.

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• The most effective among the several fuel additives used are based on MgO or Mg(OH)2, which are generally available in oil dispersed forms. Magnesium additive is the best choice for three reasons:

i. They combine with the vanadium oxides and hence increases the melting point of the ash components to a level above the system temperatures so they are no longer sticky.

ii. They modify the ash that does form to a soft, powdery and extremely friable form.

iii. They effectively neutralizes the acid that condenses on the cooler parts of the air heating system forming neutral MgSO4.

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Cairo West Case Study

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Cairo West Power PlantCase Study

• This paper presents the trial tests carried out for the

performance evaluation of one (MgO) of the three

chemical additives selected at Cairo West Plant. The

plant has 2 oil-fired boilers, which provide high-

pressure steam for operation of turbine driven

generators. The fuel oil used in the boilers is high

sulphur, low vanadium residual oil supplied by Misr

Petroleum Company.

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Objectives of Study

1. To evaluate the performance of different Fuel Chemical Additives in reducing Stack Emissions and increasing combustion efficiency.

2. To determine the effect of additives on SO3, SO2 and NOx generation and acid dew point.

3. To evaluate the quality and quantity of soot/dust production.

4. To determine the optimum dose rate.

5. To evaluate hot and cold side corrosion rates with and without additive.

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EXPERIMENTAL

• Cairo West Boiler #6 was selected for the trial tests as the test unit because it had the independent tank facility for chemical additive dosing. This boiler is Hitachi make with a maximum capacity to generate 330 MW power, steam flow 1013t/h, and fuel flow 70t/h. It has 12 on 2 levels steam assisted burners.

• The test unit was put in operation and after achieving stable condition; operational and chemical parameters were monitored without dosing any chemical additive for two weeks. Then the chemical was dosed at the high rate of 10L/hr to achieve stabilization (pH at 5min. ≈ 4.2).

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Analytical Parameters and Procedures

1. Flue gas analysis

The following parameters were determined in the boiler flue gases after the air heater (at the stack) as per the methods indicated against each:

a. SO2, NOx, CO, CO2, O2, hydrocarbons and flue gas

temperature were monitored using a portable flue gas analyzer (Madur).

b. Acid dew point and Rate of Build Up (RBU) of acid were determined using a portable Land (Model-200) instrument.

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2. Ash (Soot) Analysis:

Regular soot samples were collected and analyzed for the following parameters:

a. pH (at 5 min. & 60 min.).b. Acid content of ash as H2SO4 by titrimetry (Acidity).

3. Fuel Oil Analysis

• Fuel oil used during the study were withdrawn from the storage tanks and given for analysis to external agencies (Table 1).

• The following parameters were analyzed:

a. Physical Parameters: Gravity, Viscosity at 50 oC and gross calorific value.

b. Chemical Parameters: Carbon, Nitrogen, Hydrogen, Sulphur, Vanadium and Sodium.

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4. Boiler Shut Down Inspection

• Internal inspection of the boiler was carried out at the end of additive testing. Besides visual checks and photographic documentation chemical analysis of several deposit samples were carried out.

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I. Flue gas Characteristics

a. Acid Dew Point

• Variation of acid dew points as a function of time is shown in Figure 1.The dew points before the additive dosing showed an average value of 148 oC.

• After additive dosing the dew points varied in the range of 130 – 135 oC, a decrease of 15 – 20oC is realized. This could be considered quite a significant improvement obtained by additive dosing.

RESULTS

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147146

133

135

132

134

140 140

132132

136

134

135135

135

134133

134

137

135

137137

137.5

137136

138137

135

139138

134.5

140

139

140

141

139

135135.5

133.5

137.5

136 135

136

137

138

137

137.5 136137

130

134

138

142

146

150

6 7 10 11 13 15 16 19 22 25 26 27 28 29 30 1 3 4 5 6 8 10 11 15 19 21 24 4 5 6 7 8 11 12 13 15 19 20 21 22 23 27 29 1 4 9 14 15 19

Dew-Point

Without Injection

From 6/11/2008 to 19/2/2009

Without Injection

° C

Date

CAIRO WEST POWER STATION

Unit 6


Unit 6 Result of Dew pointduring 6/11/2008 to 19/2/2009

For PentoMag

Fig.1Fig.1

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II. Soot/Ash Characteristics

a. pH and Sulphuric Acid Content (Acidity)

• pH of the ash sample collected before additive dosing showed an average of 1. Dramatic increase was noticed with additive dosing. At the dose rate of 340 ppm the pH at 5 min. and 60 min. showed an average value up to 4.2 (Fig. 2,3).

• Acidity of the ash sample collected showed a result 27% acidity, and after dosing (340ppm) is decreased to average value around 0 to 1%, as shown in Fig. (4).

III. Quality Control of Fuel Oil

• Samples of the fuel oil were analyzed during the course of the study and the results are shown in the Table 1.

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Unit 6


Unit 6 Result of PH- 5minduring 6/11/2008 to 19/2/2009

For PentoMag

0

2

4

6

8

16 6 7 14 15 16 20 21 25 29 30 4 5 10 11 13 3 4 5 12 13 15 22 23 24 25 29 2 5 9 14 15 18

PH-5

PH

without Injection

Date

Fig.2Fig.2

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Unit 6


Unit 6 Result of PH- 60minduring 6/11/2008 to 19/2/2009

For PentoMag

0

2

4

6

8

16 6 7 15 16 20 21 25 29 30 4 5 10 11 13 3 4 5 12 13 15 22 23 24 25 29 2 5 9 14 15 18

PH-60

PH

Without Injection

Date

Fig.3Fig.3

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Result of Acidity (%)during 6/11/2008 to 18/2/2009

For PentoMag

0

5

10

15

20

25

30

16 6 7 15 16 20 21 25 29 30 4 5 10 11 13 3 4 5 12 13 15 22 23 24 25 29 2 5 9 14 15 18

Acidity (%)

Acidity

Without Injection

Date

Fig.4Fig.4


Unit 6


Unit 6

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Table (1)Fuel Oil Specifications

Properties Unit Value*Net Heating value MJ/kg 40.64

Density at 15 oC Kg/m3 942.2

Sulfur %m/m 2.48

Water (by distillation) %v/v 5.80

Sediments %m/m 0.03

Viscosity at 50 oC cst 145.7

Flash Point oC 108.8

Asphaltenes %m/m 5.10

Vanadium mg/kg 46

Sodium mg/kg 293

Ash %m/m 0.113

* Average Values for the last 6 years analysis.* Average Values for the last 6 years analysis.

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IV. Operation Parameters

a. Boiler Load

• Attempts were made to maintain load at a constant level during the course of the test period in order to reduce variation on different test parameters. Boiler efficiency remained almost constant (≈ 88.8%) before and during the additive dosing. It is very important to note that the efficiency of the boiler was not affected as a result of additive dosing. On other side the load does not decreased due to ash contamination in the air heater during the test (Fig.5).

b. Air Heater Dp

• The pressure differential (Δp) across the air heaters was monitored continuously in order to check fouling of air heaters due to the additive dosing. As seen from Figure 5, Δp across the air heaters remained steady, this indicates no fouling due to additive dosing Fig. 6.

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Unit 6


Unit 6 Relation time & Max LoadBefore & After using Fuel additive

Fig.5Fig.5

320

310

330

300295

285280

270

260

235230

215

205

325330

315310

305 302

280285

290292295

297300

180

220

260

300

340

Start 1 w eek 2 w eek 3 w eek 4 w eek 5 w eek 6 w eek 7 w eek 8 w eek 9 w eek 10 w eek 11 w eek 12 w eek

Peroid

MW

Max Load without Injection Max Load with Injection

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Result of Gas Dp at GAH (mmc)

during 8/10/2008 to 15/12/2008


Unit 6


Unit 6

5

7

9

11

13

15

17

19

Gas at GAH mmc

Date

mmc

After cleaning &

before pentomag

After pentomag

Fig.6Fig.6

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V. Boiler Inspection

• On 24/12/2008 the boiler was shutdown and the following parts was inspected.

(a) Combustion Chamber (Furnace).

(b) Super Heater.

(c) Economizer.

(d) Air Heater (upstream and downstream).

(e) Heating Elements.

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• Results of Boiler Inspection

• Condition of the furnace was generally good with soft scales on the tubes and some loose hard deposits in between the tubes.

• Primary super heater tubes were found to have a uniform of 2-3 mm thickness of thin scales. The scales were yellowish white and soft powdery material

• Flue ducts at upstream and down stream of the air heater had uniform grayish deposits.

• Air heater elements were found to be generally satisfactory at the upstream (hot end) but the down stream (cold end) air heater elements were found to be dirty

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CONCLUSIONS

1. The neutral character of the boiler soot generated during the additive dosing further confirmed the Non-corrosive nature of the flue gas. Soot samples were found to be dry and friable. The average pH of 3 and 4.5 at 5 minutes & 60 minutes, and no free acidity or very little total acidity at the dose rate of 340 ppm showed by the soot samples indicated the neutral and non-corrosive nature.

2. Boiler efficiency was not affected due to additive dosing. Appreciable increase (30 – 40 oC) in the flue gas exit temperature (economizer out/GAH in) was noted during the additive dosing, which is presumably due to the formation of reflective coating (whitening effect) of neutral compounds on the heat exchange surfaces reducing the heat transfer capacity; however, the boiler efficiency was not affected.

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3. On dosing of chemical fuel additive sufficient reduction in Acid Dew Point was observed thereby avoiding cold end corrosion.

4. Air heater ducts were found to be covered with neutral magnesium compounds which are effective in preventing corrosion of metallic parts in the area where the temperatures are below the acid dew points as a result of which there is condensation of acidic flue gases that leads to corrosion.

5. No adverse effects were noticed on the internals of the boiler due to additive dosing. Heat exchanger tubes in the super heater and economizer areas were found to have deposits of a thickness of 2- 4 mm, which were soft, and in the form of flakes.

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Thank You for Your Kind Attention

1 Cairo Electricity Production Company (CEPC) Egypt:18 March. 2009 Eng.:Ahmed Emam - CEPC Chairman...

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Transcript of 1 Cairo Electricity Production Company (CEPC) Egypt:18 March. 2009 Eng.:Ahmed Emam - CEPC Chairman...