Post on 11-Dec-2015
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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
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Contents
• CEPC Overview.
• CEPC Statistics.
• Introduction for heavy fuel firing.
• Cairo West case study
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CEPC Overview
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Cairo Electricity Production Company (CEPC)
• 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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Cairo Electricity Production Company (CEPC)
• 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.
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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
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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
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CEPC Distributed Energy by Plants2007-2008
29%Cairo North
2%Wadi Hof 29%
Shobra
23%Cairo West
17%Cairo South
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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
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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%
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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
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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
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Furnace Bottom Pipes
Before After
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Reheat Pipes
Before After
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Primary Superheat Pipes
Before After
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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
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Gas/Air Heater Baskets
Before After
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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
CAIRO WEST POWER STATION
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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CAIRO WEST POWER STATION
Unit 6
CAIRO WEST POWER STATION
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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CAIRO WEST POWER STATION
Unit 6
CAIRO WEST POWER STATION
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
CAIRO WEST POWER STATION
Unit 6
CAIRO WEST POWER STATION
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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CAIRO WEST POWER STATION
Unit 6
CAIRO WEST POWER STATION
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
CAIRO WEST POWER STATION
Unit 6
CAIRO WEST POWER STATION
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