|1||Raw material for BLCP BLCP Power Station is bituminous coal imported from Australia and Indonesia. The coal is transported from ships to the berth located at the south-west the coal yard, The total storage capacity is 662,000 tons sufficient for 60-days continuous electricity generation.
|2||From the coal yard, the coal is transported via conveyors to bunkers and coal pulverizers where it is ground to suitable size for inputting into boiler furnance in suspension in transport air. Combustion of coal provides heat which which is then transferred to demineralized water in the tubes surrounding the furnace.
|3||Boiling water and steam are separated in the boiler drum located at the top of the boiler. The water is further heated in the furnace, whereas the steam enters superheat coil where the temperature is increased and the pressure be properly adjusted before entering a steam turbine.
|4||The steam transfers energy to the trubine and turn the generator, which is connected to the turbine. (Figure 3 reveals the operation of BLCP Power Station). When the generator turns round, the magnetic field crossing the coils within the generator results in electrical power.
|5||The power is transformed by a generator transformer so that the voltage will match the system of EGAT.
|6||The steam passing through the steam turbine drops in temperature and pressure and will be condensed in the condenser. The condensed water is rerurned to the boiler again to produce more steam.
|7||While heavy ash called 'bottom ahs' settle at the botom of the boiler furnace, fly ash will be carried with the flue gas through the boiler and at the outlet will be trapped by electrostatic precipitator. Since the coal has sulfur as an impurity, combustion leads to a reaction which produces sulphur dioxide(SO2). Therefore, a sea water flue gas desulfunization plant is provided to trap SO2 before it is emitted into the air. NOx will also be minimised by use of low NOx burners of advanced design using the latest technology.
Each unit has large sub-critical single drum assisted circulation boiler.
The steam turbine is of the single reheat, condenser, tandem compound type, comprising three cylinders, There is a combine HP/IP cylinder in which the high temperature steam is expanded, followed by two double flow LP cylinders that exhaust steam to a single condenser. The steam turbine is equipped with control valves, stop valves, and control systems to ensure safe operation under all circumstances. The design of the turbine is optimized to achieve high efficiency and reliability.
The brushless exciter type generator is cooled by water and hydrogen. It is a 3 phase, 2 pole, 3000 rpm machine and generates power at 19 KV. The voltage is increased to 500 KV in the main generator transformer to supply power via the power station switchyard to the EGAT 500 KV Grid System. Isolated phase bus-ducts are used to transfer power from the generator to the generator transformer.
Each condenser unit is the horizontal radial flow one-pass, surface cooling type with divided water box and the turbine exhaust inlet-hoods at the top. Three vacuum pumps are used to remove air and gas from the condenser. The condenser water boxes are coated with rubber to prevent corrosion, and condenser tubes are made form titanium. The condenser is also fitted with the on-line ball cleaning equipment for automatic cleaning purpose.
|5||Electrostatic Precipitators (EP)
Each boiler has two electrostatic precipitators connected in parallel, each treating 50% of the flue gas leaving the boiler. The precipitators are of the rigid frame out-door type, each having four fields and being capable of a dust collection efficiency greater than 99%.
|6||Flue Gas Desulfurization System (FGD)
The Flakt seawater washing FGD system is used. Each boiler is equipped with a single absorber tower capable of treating about 70% of the flue gas. A booster fan is provided to transfer the flue gas to the absorber via a quencher where the gas is cooled down by seawater sprays to the design inlet temperature. The absorber tower is of the packed type Warm seawater from the condenser is supplied to inlet noggles at the top of the absorber tower by booster pumps. The seawater is then sprayed down the absorber tower through the packing and flue gas flows up the tower in the opposite direction to the seawater. This brings the seawater into contact with all of the flue gas to remove the SO2 from the flue gas. As the SO2 is absorbed by the seawater its pH is reduced so making it acidic. After leaving the absorber, the seawater is treated in aeration ponds where the sulfide is oxidized to sulphate, releasing CO2 and raising the pH to neutral. After aeration the seawater is mixed with the remainder of the condenser cooling water before discharge back to the sea. Treated flue gas leaving the absorber tower is reheated by mixing with untreated flue gas from the boiler, after which it is released into the atmosphere.
Steam from the LP turbines will be condensed in condenser using seawater in a once through cooling system. The condensate will be pumped from the condenser hot will through the gland steam condenser and low pressure heaters to raise its temperature before entering the deaerator. The hot condensate will be pumped from the deaerator by turbine driven boiler feed pumps through high pressure feed heaters and the boiler economizer into the boiler drum.
In the boiler drum steam will be separated from the remaining water which will be further circulated in the boiler to generate steam. The steam will flow from the boiler drum to the superheater to raise its temperature to the level required for the HP turbine. Steam temperature will be controlled by means of spray water desuperheaters.
Main Steam and Reheat Steam
The main steam supply leaving the superheater at high temperature and pressure will enter the HP turbine through governor valves which control the quantity of steam supplied. After transferring energy to the HP turbine most of the steam will be returned to another section of the boiler for reheating to the high temperature required for the IP turbine. The reheated steam will enter the IP turbine, pass on to the LP turbines via the cross over pipes and finally be exhausted to the condenser. The power produced by the generator will be supplied to the EGAT 500 KV grid via isolated phase bus ducts, the generator transformer and the station switchyar
Cooling Eater and FGD Process
The power station will abstract 5.34 million m3 per day of seawater with both units operating at base load. This is used for cooling purposes and to operate the seawater washing flue gas desulfurization (FGD) system. This water will be drawn in from the harbor at low velocity (0.3 m/s) to avoid interference with shipping and to allow fish to escape from the intake current.
A bar screen will be installed to remove large debris from the intake water. A traveling screen will provide a finer screening of the water to remove small fish and other smaller aquatic life. These screens will protect the cooling water intake pumps and the rest of the cooling system from blockage. Debris collected on the bar screen will be removed and disposed of as a waste.
The traveling screens will be back-washed to remove debris. If the organisms in the wash water are found to be generally viable they will be returned to the sea by gravity in a channel or pipe. The velocity of flow in this will be such as to minimize damage to fish and other marine life. If only dead debris is being collected, this will be removed and disposed of off-site as waste.
The cooling water system will require intermittent dosing with chlorine to control biological fouling of the system. If uncontrolled, fouling would result in decreased heat transfer efficiency in the condensers and hence loss of generating effluent standard of 1.0 mg/1. In fact, any residual active chlorine in the water leaving the condensers will be reduced on contact with the FGD process water containing unoxidized SO2 or sulfite. As no further biofouling control will be required downstream of the aeration lagoon, the residual oxidant levels in the discharge will be negligible.
The water will pass through the condensers in the power station to cool the steam leaving the turbines. A portion of this flow is then routed to the FGD absorber where it is sprayed through the flue gas after it has passed through the electrostatic precipitators. The natural bicarbonate alkalinity in the seawater absorbs SO2 from the gas, with a resultant fall in pH as it does so. The system is designed for an efficiency of 70% removal of the SO2 from the flue gas.
The low pH seawater is then passed to a water treatment plant where it is mixed with the remainder of the cooling water flow and aerated to strip off the free CO2 produced from the bicarbonates. This removal of CO2 increases the pH of the water again, such that the discharge from the aeration lagoons has a pH value 7.0. The aeration also oxidizes sulfite in the water to sulfate, resulting in a well-oxygenated discharge with a low chemical oxygen demand. Heat is transferred into the water both in the condensers and the FGD absorber. The system is designed not to exceed a maximum temperature of 40 °C at the discharge.
The discharge will be via a channel placed at the southern shoreline of the site with a velocity of 1.5 m/s.
Fresh Water Supply
The power station will consume fresh water for domestic and operation process such as boiler make-up at the rate of 4,500 m3/day. The present commitments for the supply of water from the Dok Krai reservoir and Nong Pla Lai. About 2,179 m3 of raw water will be supplied to the water treatment system to produce the so-called tap water for domestic and process purposes. The other 2,321 m3/day raw water will be supplied directly to control dust in the coal yard and the ash handling with the rate of 1,821 m3and 500 m3, respectively.
Emissions and Effluents
Air Emission from Main Stacks
The power plant has two flues within a common stack. The following characteristics are those of combined stack.
BLCP 1400 MW
|Height of nearby structures||80||m.|
|No. of Flues||2||in combined stack|
|Sulfur in coal||0.70||max %|
|Pollutants||Loading (g/s)||Concentration *||Emission Std.|
|SO2||1020||262 ppm||320 ppm|
|NOx||681||241 ppm||350 ppm|
|TSP||64||43 mg/m3||120 mg/m3|
|CO||-||94 ppm||870 ppm|
* (At 1 atm 25 C and 7% O2 excess dry, ppm = part per million)
Air Pollution from coal management:
- dust generation at the unloader, transfer points, from the stacks and within the station
The dust generated from these sources will be controlled by closed conveyors or open conveyers with wind guards fitted. Water sprays will be provided at coal stockpiles, with a sprinkler system which will operate automatically. In addition, there will be a wind fence set downwind of the coal stockyard to provide additional protection.