COGENERATION PROJECTCOGENERATION PROJECTPERFOMANCE OF THE COGEN PLANTPERFOMANCE OF THE COGEN PLANT

19981998

BY BY

GAIQUI VivianGAIQUI Vivian

FUEL Steam & Power Generation FUEL Steam & Power Generation Existing Plant No. 1Existing Plant No. 1

BOILERBOILER Fives Cail BabcockFives Cail Babcock Rating:110T on Bagasse ModeRating:110T on Bagasse Mode 90T on Coal Mode90T on Coal Mode Steam Pressure:45barsSteam Pressure:45bars Steam Temp: 450°cSteam Temp: 450°c

TURBO GENERATOR GROUPTURBO GENERATOR GROUP Creusot Loire/Jeumont SneiderCreusot Loire/Jeumont Sneider Power: 21.7 MwPower: 21.7 Mw Extraction Pressure:1,5barExtraction Pressure:1,5bar Condensor Capacity:110tCondensor Capacity:110t

FUEL Steam & Power Generation FUEL Steam & Power Generation Power Plant No. 2Power Plant No. 2

BOILERBOILER John Thompson AfricaJohn Thompson Africa Single Pass/Suspended boilerSingle Pass/Suspended boiler

Rating:100 T on Bagasse ModeRating:100 T on Bagasse Mode 80 T on Coal Mode80 T on Coal Mode Steam Pressure:45 BarsSteam Pressure:45 Bars Steam Temp: 450 °cSteam Temp: 450 °cTURBO GENERATOR GROUPTURBO GENERATOR GROUP

ABB/SIEMENSABB/SIEMENS Extraction & CondensingExtraction & Condensing

Power: 18.8 MwPower: 18.8 Mw Extraction Pressure:1,5barExtraction Pressure:1,5bar Condensor Capacity:100tCondensor Capacity:100t

POWER PLANT 1 & 2 (steam & Power)POWER PLANT 1 & 2 (steam & Power)

AdvantagesAdvantages

High overall efficiencyHigh overall efficiency Any type of fuel may be used Any type of fuel may be used

(Bagasse/Coal)separately or in combined (Bagasse/Coal)separately or in combined modemode

Heat to power ratios can be varied Heat to power ratios can be varied through flexible operationsthrough flexible operations

Ability to meet more than one site heat Ability to meet more than one site heat grade requirementgrade requirement

Wide range of sizes availableWide range of sizes available Long working lifeLong working life

THE BOILER THE BOILER The choice was a The choice was a JOHN THOMPSON AFRICA JOHN THOMPSON AFRICA Boiler Boiler with operating pressure of:with operating pressure of:

- 4500 Kpa - 4500 Kpa with a mean temp. of with a mean temp. of 440ºc440ºc

(same working pressure as Boiler No.1)(same working pressure as Boiler No.1)

These specific conditions were chosen toThese specific conditions were chosen to

optimize the power generation capacity whileoptimize the power generation capacity while

at the same time refraining the need for at the same time refraining the need for sophisticated and high cost of water treatment.sophisticated and high cost of water treatment.

THE DEMIN PLANTTHE DEMIN PLANTAfter a survey of the existing Demin Water Plant After a survey of the existing Demin Water Plant

and in addition of the return condensate from the and in addition of the return condensate from the Sugar Factory Process Results shows that the Sugar Factory Process Results shows that the existing DEMIN WATER PLANT was enough existing DEMIN WATER PLANT was enough efficient and sufficient for the 2 boilers need.efficient and sufficient for the 2 boilers need.

Flow Rate service:15m³/hrFlow Rate service:15m³/hr

Capacity:250m³ nett. Between regenerationCapacity:250m³ nett. Between regeneration

Raw water quality: Cations 91mg/lRaw water quality: Cations 91mg/l

Anions 71mg/lAnions 71mg/l

pH 6,5-7,5pH 6,5-7,5

Operating pressure: 500kpaOperating pressure: 500kpa

JTA BOILER EFFICIENCY JTA BOILER EFFICIENCY To maintain the steam temp.within the close limits To maintain the steam temp.within the close limits

required by the 18.8Mw/h Extraction/Condensing required by the 18.8Mw/h Extraction/Condensing turbo alternator. turbo alternator.

The single pass boiler is fitted with two stage The single pass boiler is fitted with two stage superheaters and interstage attemperator.superheaters and interstage attemperator.

(This differenciate with others conventional boilers which are (This differenciate with others conventional boilers which are usually fitted with spray Attemperator and requires a high usually fitted with spray Attemperator and requires a high quality water)quality water)

While in this case of the JTA Boiler, the While in this case of the JTA Boiler, the attemperation is achieved by passing a attemperation is achieved by passing a portion of the steam through a heat portion of the steam through a heat exchanger heated in the of the boiler exchanger heated in the of the boiler water drum.water drum.

EFFICIENCY OF COMBUSTION CONTROL EFFICIENCY OF COMBUSTION CONTROL

Grit refiring is also in operation to improve Grit refiring is also in operation to improve combustion efficiency on coal mode.combustion efficiency on coal mode.

Optimal boiler efficiency is achieved by Optimal boiler efficiency is achieved by

reducing the flue gas temperature to 130ºc by reducing the flue gas temperature to 130ºc by means of a heated economisers,So as to avoid means of a heated economisers,So as to avoid risk of dew point corrosion in the lower banks of risk of dew point corrosion in the lower banks of economiser tubes while firing coal,a feed water economiser tubes while firing coal,a feed water heater preheats the feed water to approx. 135 heater preheats the feed water to approx. 135 ºc (steam from turbine MP outlet)ºc (steam from turbine MP outlet)

WET SCRUBBER WET SCRUBBER

The outlet flue gas passes through a wet The outlet flue gas passes through a wet gas scrubber to reduce gas scrubber to reduce

particulate emissions to below particulate emissions to below 120mg/nm³ both on Bagasse and 120mg/nm³ both on Bagasse and coal,ensuring the running of the plant coal,ensuring the running of the plant

“ “ ENVIRONMENTAL FRIENDLY”ENVIRONMENTAL FRIENDLY”

THE BAGASSE & COAL HANDLINGTHE BAGASSE & COAL HANDLING Once again the existing installation was Once again the existing installation was

upgraded to Feed the Boiler No.2upgraded to Feed the Boiler No.2

- COAL HANDLING- COAL HANDLING

With slight modification to of COAL HANDLING With slight modification to of COAL HANDLING installation /distribution equipments,the BOILER 2 is installation /distribution equipments,the BOILER 2 is feeded correctly.feeded correctly.

- BAGASSE HANDLING- BAGASSE HANDLING

On the other side by adding 3 New belt conveyors,the On the other side by adding 3 New belt conveyors,the

routing of Bagasse Feed to BOILER 1 & 2 are being done routing of Bagasse Feed to BOILER 1 & 2 are being done sufficiently. sufficiently.

The Turbo Generator GroupThe Turbo Generator Group The ABB/Siemens reaction Turbine with:The ABB/Siemens reaction Turbine with:- Rating of 18.8Mw Rating of 18.8Mw - Working INLET Pressure 45bars/440°c steam andWorking INLET Pressure 45bars/440°c steam and- Medium Steam Temperature at 6bars/135°c Medium Steam Temperature at 6bars/135°c - Extraction Steam 2bars for the Sugar Factory ProcessExtraction Steam 2bars for the Sugar Factory Process- Turbine speed 6800rpmTurbine speed 6800rpm- Voltage system:6.6Voltage system:6.6- Alternator speed:1500rpmAlternator speed:1500rpm

And fitted with:And fitted with:

-100T/h surface condensor-100T/h surface condensor

-Aero cooling Tower of 3 Units-Aero cooling Tower of 3 Units

Performing with INLET Water Temp Max.35°cPerforming with INLET Water Temp Max.35°c

The Turbine General DescriptionThe Turbine General DescriptionFor the conversion of Thermal energy into mechanical power,the For the conversion of Thermal energy into mechanical power,the

Turbine receives Superheated steam of 44bars/430°c from the Turbine receives Superheated steam of 44bars/430°c from the main steam line.The live steam coming from the main steam main steam line.The live steam coming from the main steam line passes through the Live-steam emergency stop Valve,the line passes through the Live-steam emergency stop Valve,the three control valves,the control stage nozzles and the control-three control valves,the control stage nozzles and the control-wheel-blades entering the wheel chamber and flow through the wheel-blades entering the wheel chamber and flow through the reaction part.The enthalpy drop of steam across the 18stages reaction part.The enthalpy drop of steam across the 18stages of the turbine is transformed into energy in a continuos of the turbine is transformed into energy in a continuos process.Steam flow through the control valves and the control process.Steam flow through the control valves and the control wheel into the turbine. wheel into the turbine.

The Turbine is equiped with an Extraction line,where it is possibleThe Turbine is equiped with an Extraction line,where it is possible

to lead steam after the 12to lead steam after the 12thth reaction stage into Extraction line. reaction stage into Extraction line.

A bleed line make possible to lead steam after the 9A bleed line make possible to lead steam after the 9thth reaction reaction stage into the bleed line.stage into the bleed line.

The steam turbine is equiped with a control wheel to enable a The steam turbine is equiped with a control wheel to enable a good efficiency at partial load points due to flow control without good efficiency at partial load points due to flow control without throtting losses. throtting losses.

STEAM & POWER GENERATION STEAM & POWER GENERATION INTERCROPINTERCROP

- During INTERCROP season the Two Power During INTERCROP season the Two Power Plants namely:Plants namely:

- Power Plant No. 1 Max Rating: 21.7MwPower Plant No. 1 Max Rating: 21.7Mw

& & - Power Plant No.2 Max Rating: 18.8 MwPower Plant No.2 Max Rating: 18.8 Mw

Export Max off crop:32Mgw/hExport Max off crop:32Mgw/h

STEAM & POWER GENERATIONSTEAM & POWER GENERATION CROP SEASON CROP SEASON

-The Two POWER PLANTS operates on Extraction Mode -The Two POWER PLANTS operates on Extraction Mode and Bagasse firingand Bagasse firing

Export Max :22MwExport Max :22Mw - Extraction Steam to FACTORY PROCESS- Extraction Steam to FACTORY PROCESS*Steam Flow to Factory:300t/h*Steam Flow to Factory:300t/h*Steam Pressure:2bars*Steam Pressure:2bars*Condensate Return from process at Full load:130t*Condensate Return from process at Full load:130t

Performance 2008:Performance 2008:Cane Crushed:976,000tCane Crushed:976,000t

Bagasse:312,500tBagasse:312,500t

BOILER EFFICIENCY on BAGASSE MODEBOILER EFFICIENCY on BAGASSE MODE Bagasse has a calorific value of 19,250 KJ/kg at 0% Bagasse has a calorific value of 19,250 KJ/kg at 0%

moisture content.The nett calorific value of bagasse at moisture content.The nett calorific value of bagasse at 48% moisture content is approx. 8,000KJ/kg.Moisture 48% moisture content is approx. 8,000KJ/kg.Moisture content is the most determinant parametercontent is the most determinant parameter.A lower .A lower

moisture content result in a higher calorific valuemoisture content result in a higher calorific value. .

However,most mills in MAURITIUS produce a bagasse However,most mills in MAURITIUS produce a bagasse with 48% moisture.During combustion, steam to with 48% moisture.During combustion, steam to bagasse ratio is normally taken as 2.2.bagasse ratio is normally taken as 2.2.

By working out the recorded datas the efficiency is:By working out the recorded datas the efficiency is:1t 1t of Bagasse =2.1t/Steamof Bagasse =2.1t/Steam

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