COGENERATION PROJECT PERFOMANCE OF THE COGEN PLANT 1998 BY GAIQUI Vivian OBJECTIVES OF THE PROJECT

FUEL Steam & Power Generation Existing Plant No. 1 BOILER Fives Cail Babcock Rating:110T on Bagasse Mode 90T on Coal Mode Steam Pressure:45bars Steam Temp: 450°c TURBO GENERATOR GROUP Creusot Loire/Jeumont Sneider Power: 21.7 Mw Extraction Pressure:1,5bar Condensor Capacity:110t

FUEL Steam & Power Generation Power Plant No. 2 BOILER John Thompson Africa Single Pass/Suspended boiler Rating:100 T on Bagasse Mode 80 T on Coal Mode Steam Pressure:45 Bars Steam Temp: 450 °c TURBO GENERATOR GROUP ABB/SIEMENS Extraction & Condensing Power: 18.8 Mw Extraction Pressure:1,5bar Condensor Capacity:100t

POWER PLANT 1 & 2 (steam & Power)

Advantages High overall efficiency Any type of fuel may be used (Bagasse/Coal)separately or in combined mode Heat to power ratios can be varied through flexible operations Ability to meet more than one site heat grade requirement Wide range of sizes available Long working life

THE BOILER The choice was a JOHN THOMPSON AFRICA Boiler with operating pressure of: - 4500 Kpa with a mean temp. of 440ºc (same working pressure as Boiler No.1) These specific conditions were chosen to optimize the power generation capacity while at the same time refraining the need for sophisticated and high cost of water treatment.

THE DEMIN PLANT After a survey of the existing Demin Water Plant and in addition of the return condensate from the Sugar Factory Process Results shows that the existing DEMIN WATER PLANT was enough efficient and sufficient for the 2 boilers need. Flow Rate service:15m³/hr Capacity:250m³ nett. Between regeneration Raw water quality: Cations 91mg/l Anions 71mg/l pH 6,5-7,5 Operating pressure: 500kpa

JTA BOILER EFFICIENCY To maintain the steam temp.within the close limits required by the 18.8Mw/h Extraction/Condensing turbo alternator. The single pass boiler is fitted with two stage superheaters and interstage attemperator. (This differenciate with others conventional boilers which are usually fitted with spray Attemperator and requires a high quality water) While in this case of the JTA Boiler, the attemperation is achieved by passing a portion of the steam through a heat exchanger heated in the of the boiler water drum.

EFFICIENCY OF COMBUSTION CONTROL Grit refiring is also in operation to improve combustion efficiency on coal mode. Optimal boiler efficiency is achieved by reducing the flue gas temperature to 130ºc by means of a heated economisers,So as to avoid risk of dew point corrosion in the lower banks of economiser tubes while firing coal,a feed water heater preheats the feed water to approx. 135 ºc (steam from turbine MP outlet)

WET SCRUBBER The outlet flue gas passes through a wet gas scrubber to reduce particulate emissions to below 120mg/nm³ both on Bagasse and coal,ensuring the running of the plant “ ENVIRONMENTAL FRIENDLY”

THE BAGASSE & COAL HANDLING Once again the existing installation was upgraded to Feed the Boiler No.2 - COAL HANDLING With slight modification to of COAL HANDLING installation /distribution equipments,the BOILER 2 is feeded correctly. - BAGASSE HANDLING On the other side by adding 3 New belt conveyors,the routing of Bagasse Feed to BOILER 1 & 2 are being done sufficiently.

The Turbo Generator Group The ABB/Siemens reaction Turbine with: Rating of 18.8Mw Working INLET Pressure 45bars/440°c steam and Medium Steam Temperature at 6bars/135°c Extraction Steam 2bars for the Sugar Factory Process Turbine speed 6800rpm Voltage system:6.6 Alternator speed:1500rpm And fitted with: -100T/h surface condensor -Aero cooling Tower of 3 Units Performing with INLET Water Temp Max.35°c

The Turbine General Description For the conversion of Thermal energy into mechanical power,the Turbine receives Superheated steam of 44bars/430°c from the main steam line.The live steam coming from the main steam line passes through the Live-steam emergency stop Valve,the three control valves,the control stage nozzles and the control-wheel-blades entering the wheel chamber and flow through the reaction part.The enthalpy drop of steam across the 18stages of the turbine is transformed into energy in a continuos process.Steam flow through the control valves and the control wheel into the turbine. The Turbine is equiped with an Extraction line,where it is possible to lead steam after the 12th reaction stage into Extraction line. A bleed line make possible to lead steam after the 9th reaction stage into the bleed line. The steam turbine is equiped with a control wheel to enable a good efficiency at partial load points due to flow control without throtting losses.

STEAM & POWER GENERATION INTERCROP During INTERCROP season the Two Power Plants namely: Power Plant No. 1 Max Rating: 21.7Mw & Power Plant No.2 Max Rating: 18.8 Mw Export Max off crop:32Mgw/h

STEAM & POWER GENERATION CROP SEASON -The Two POWER PLANTS operates on Extraction Mode and Bagasse firing Export Max :22Mw - Extraction Steam to FACTORY PROCESS *Steam Flow to Factory:300t/h *Steam Pressure:2bars *Condensate Return from process at Full load:130t Performance 2008: Cane Crushed:976,000t Bagasse:312,500t

BOILER EFFICIENCY on BAGASSE MODE Bagasse has a calorific value of 19,250 KJ/kg at 0% moisture content.The nett calorific value of bagasse at 48% moisture content is approx. 8,000KJ/kg.Moisture content is the most determinant parameter.A lower moisture content result in a higher calorific value. However,most mills in MAURITIUS produce a bagasse with 48% moisture.During combustion, steam to bagasse ratio is normally taken as 2.2. By working out the recorded datas the efficiency is:1t of Bagasse =2.1t/Steam

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