Friday, December 26, 2008

Ultra-mega thermal plants & the Ultra-Mega fly-ash menace

The Tribune, Chandigarh, India - Science Tribune
Ultra-mega thermal plants; Mega flyash problems

Dr G.S. Dhillon

A recent report datelined Bathinda, filed by TNS correspondent S.P. Sharma appeared in The Tribune dated October 31 describing the situation at Bathinda City: “It flyash all the way in Bathinda” along with a photograph of a scooterist virtually sailing through a cloud of flyash.

This has made many of us ponder what would be the state of affairs once the two proposed “ultra-mega thermal plants” of Talwandi Sabo and Gidderbaha start operating.
Guru Nanak Dev Thermal Plant, Bathinda: Flyash is everywhere.
Guru Nanak Dev Thermal Plant, Bathinda: Flyash is everywhere. Tribune photo: Malkiat Singh

An attempt has been made in this article to consider the problem.

At the present stage, the thermal plants installed in Punjab have the capacity of 2120 MW, with 1260 MW Super Plant at Ropar, 440 MW Plant at Bathinda and 420 MW at Lehra Mohabat.

The annual production of solid waste in the form of flyash (containing 20 per cent furnace bottom ash) from all the above listed TPs is around 20 lakh tons.

The new thermal plants planned would add an additional generation capacity of 6480MW:

l 1980 MW from the Talwandi Sabo Ultra-Mega Thermal Plant.

l 2640 MW from the Gidderbaha Ultra-Mega Thermal Plant,

l 1320 MW from the Rajpura Mega Thermal Plant

l 540 MW from the Goindwal Thermal Plant.

At that stage, the total thermal power generation capacity would be 8600 MW and the annual flyash production requiring proper handling would be above 80 lakh tonnes.

The regulations issued by the Ministry of Environment and Forest (MOEF), Government of India, require that “all the thermal plants will have to ensure 100 per cent utilisation of the solid waste (flyash plus furnace bottom ash) within the prescribed period, which is nine years after their commissioning in the case of new TPs to be set up. In the case of the older existing plants, the time limit to achieve the 100 per cent utilisation target is “by the year 2015” i.e. within the next seven years.

Flyash is fine powdery material and its particles are spherical in shape and of glassy nature. The flyash contains a reactive material which reacts with “lime” in the presence of water, to form calcium silicate hydrate, which acts as a binding material.

This property of flyash is utilised for part replacement of cement in the case of cement concrete using OPC (Ordinary Portland Cement). Also PPC (Portland Puzzolana Cement) is obtained by mixing flyash with burnt clinker before grinding. The proportion of flyash, conforming to IS: 3812 (Part I-1) may vary between 15 per cent to 35 per cent.

l Flyash can be used to form a “flowable fill” which pours freely and get set quickly and provide strength equal to that of “compacted soil”. So flyash in this form can be used to fill up trenches, cuts, abandoned mine etc.

l Flyash can be used for building embankments for road construction.

l Flyash can be used as “filler” in the manufacture of plastic components replacing “plastic resin”.

Roller compacted concrete using flyash has been found to possess many merits and used in many situations. In case of the Ghatgar pumped storage scheme, the roller compacted concrete using flyash was used for construction of the Saddle Dam and the Upper Dam.

Flyash has been beneficially used for “soil conditioning” of agricultural soils in Maharashtra and flyash has also been used to provide “fertiliser capability”. For this purpose it should be used in the “wet” form

For burnt clay bricks, a 25 per cent replacement of soil with flyash is now a must for brickkilns located within 100 km. radius of TPs as per orders from the MOEF.

Building blocks using upto 88 per cent of flyash: furnace bottom ash (in equal proportion) and 12 per cent lime have been produced by PMET, who has obtained a patent for the same. The blocks are “cured” in an auto-clave for six hours at steam pressure of 200 psi and 370 degree F temperature. The product thus obtained is called “BRIXX”.

In case of the Ropar super thermal plant, the ash ponds were found to pollute groundwater and objections were raised the Punjab Pollution control Board and the PSEB was asked to take necessary steps’ to check this menace.

Also, the air pollution has been found to be acute around the Ropar thermal plant area and so it has been decided to raise the chimney height by 200 ft to correct the situation by dispersing the pollutants over a wider area so as to minimise their intensity.

Farmers in the areas surrounding the Ropar TP have complained of reduction in crop yields on account of ground water as well as atmospheric pollutants. This aspect needs to be studied by agencies like the PAU.

This scenario is true for all thermal plants, though the intensity of the problem could vary. For the new Ultra-Mega Thermal Plants coming up, one can only hope that all the necessary environmental clearances are obtained and implemented in letter and spirit to avoid an environmental catastrophe.

While Punjab enters the “Ultra-Mega Thermal” era to tackle its rising power needs, we should also plan ahead for disposal and utilisation of the mega-quantities of the solid wastes that would be obtained (flyash & FBA), so that environmental degradation is not obtained in the area of influence around these Ultra-Mega Thermal Plants.

Progress and growth at the cost of the environment is not an acceptable trade-off. Keeping in mind that the binding 100 per cent flyash usage regulations are still 7-9 years away from implementation, we hope that we can avoid the Bathinda scooterist’s plight being repeated in other cities and villages of Punjab — the green state.

No comments: