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UPCL's clarification regarding fly-ash generation and disposal
PRESS RELEASE NOTE
CLARIFICATION AND INFORMATION SHARING ON ASH GENERATION AND DISPOSAL at UPCL plant
UPCL unit was in shut down for annual maintenance for nearly 45 days during which period no fly ash or bottom ash could be generated. However as boiler was under maintenance, cleaning of boiler & hoppers was done and bottom ash swiped from boiler is removed and put in wet form as usual before a week. It is to inform that no leaking or overflowing have occurred till date as reported in media since ash dyke is laid with impervious liners and water recovery system is provided.
The allegation of using open lorry for dumping of ash is refuted as the methodology adopted for putting the fly ash in the ash pond is only through mixing with water and making in slurry form and discharged through ejector system. Fly ash is transported through closed bulkers only. Bottom ash is transported in dumpers which is in wet form and put inside the ash pond which is a normal practice. Further the allegation of contamination of wells and damaging of farm land due to increase in water levels in ash pond during monsoon is also not correct as ash pond is provided with impervious layer and overflow does not arise at all. Further it is a fact that the company is provided a water recycling system for reuse after treatment with in the plant.
Regarding the allegation of health condition of some individuals we reiterate that the individuals concerned are open opponents of the project for last two decades and hence the same is only with ulterior motive.
We describe as below the methodology and systems provided in UPCL for ash handling in the plant.
UPCL uses imported coal as fuel for power generation in boiler to produce steam which inturn is used in the turbines to generate power. The imported coal is having much lower ash content (used in UPCL) compared to Indian coal (which is as high as 35% to 50%) used in most of other power plants.
Coal is pulverised (powder form) before it is used in boiler and hence the ash is released in fly ash form (which is more than 80%) and bottom ash (the coarse form; which is less than 20%). Fly ash is carried along with flue gases and collected in Electro Static Precipitators (ESP) in dry form. Bottom ash is collected at the bottom of the Boiler in wet form.
Collection and disposal of fly ash:
80% of the ash collected as fly ash in ESPs is sent to ash silos through pneumatic conveying pipes inside the plant and stored for disposal. Fly ash is useful material and collected in dry form and issued to end users for cement manufacturing and other purposes like bricks, ready mix concrete etc. It is proposed to use 100% ash utilisation in future with a time frame. As on date more than 50% of ash is being used by cement manufacturers by lifting from our ash storage silos.
Unutilised fly ash only is transported in closed bulkers to ash pond for putting the ash in the slurry form through an ejector system fly ash is mixed with water jetting nozzle and disposed in slurry form. All the time a thin film of water is maintained to avoid the fugitive emissions.
Ash pond is constructed with impervious layers for not allowing the water to go down in ground to avoid contamination.
Collection and disposal of bottom ash:
Bottom ash (which is 20% of the total ash) from the boiler is in coarse form is collected in water impounded hopper and then transported to a storage bin inside the plant. Bottom ash only can be used in any land filling or road making etc. Hence the bottom ash in wet form is transported in open truck and put inside the ash pond to get pushed into the water on continuous basis. The truck is taken inside the pond through a ramp made of ash and ash is pushed into the water. Ramp is kept moist all the time by sprinkling water. Ash pond water is treated and reused for again mixing for slurry.
P. Krishna Gopal
Sr. General Manager – Operations
Padubidri, November 22nd 2011: UPCL's Senior Manager (operations), P. Krishna Gopal, in his press release, gave clarification regarding fly-ash generation and disposal at UPCL power plant, in detail. Following is the full text of the press release note received by us.