As sensitivity towards the environment has increased over the past few years, policymakers have issued various guidelines with the objective of either reducing fly ash generation or ensuring its proper utilisation and transportation. In addition, guidelines restricting water consumption by thermal power plants (TPPs) have been issued with a view to address environmental concerns.
A brief overview of the relevant water consumption and fly ash guidelines impacting power producers….
Water consumption norms
In December 2015, the Ministry of Environment, Forest and Climate Change (MoEFCC) notified new water consumption limits for TPPs. As per the modified norms, all existing TPPs with once-through cooling systems need to install cooling towers and achieve a specific water consumption of 4 cubic metres (m3) per MWh (maximum). Meanwhile, existing cooling tower-based plants will have to reduce their specific water consumption to a maximum of 3.5 m3 per MWh.
The existing plants will have to comply with the water consumption limits within a period of two years from the date of notification of the guidelines (December 7, 2015). However, new units commissioned from January 1, 2017 onwards will have to restrict their specific water consumption to 2.5 m3 per MWh. In addition, these plants are required to achieve zero liquid discharge.
These new water consumption limits are expected to impact the process of ash handling adopted by TPPs. The fly ash and bottom ash generated by TPPs are typically disposed of into an ash pond in the form of wet slurry, which needs a significant amount of water. Thus, the new norms make it necessary for TPPs to adopt ash disposal methods that require less water. Some steps that can be taken to reduce water consumption in ash disposal are decreasing the water-ash ratio for slurry disposal, recirculating pond water, deploying high concentration slurry disposal systems for fly ash, and using dry bottom systems.
Fly ash utilisation norms
The MoEFCC has issued various notifications on fly ash utilisation standards on a regular basis. The first notification was issued on September 14, 1999, which was subsequently amended on August 27, 2003; November 3, 2009; March 25, 2015; and January 25, 2016.
According to the ministry’s 2009 amendment, all coal/lignite power stations/ expansion units in operation before November 2009 (the notification date) were required to achieve a fly ash utilisation target of at least 50 per cent of fly ash generated within one year of the date of issue of the notification, at least 60 per cent within two years, 75 per cent within three years, 90 per cent within four years, and 100 per cent within five years of the date of the notification. The policy also required that the unutilised fly ash against the targeted level should be utilised, in addition to the targets of the corresponding years. Similarly, stipulations were prescribed for plants commissioned after November 3, 2009.
As per the amendments in January 2016, the MoEFCC has made it mandatory for units located within a 300 km radius of a TPP to use fly ash-based building products (cement or concrete, fly ash bricks, blocks, tiles) in all construction projects, for road or flyover embankment construction as well as for the reclamation of low-lying areas. In addition, the new amendments have made the use of ash-based bricks and other products mandatory in all government schemes like the Mahatma Gandhi National Rural Employment Guarantee Scheme, the Swachh Bharat Abhiyan and the Urban and Rural Housing Scheme, where the built-up area is more than 1,000 square feet, as well as in infrastructure construction such as buildings in designated industrial estates or parks or special economic zones. The amendment has also directed the Ministry of Agriculture to consider the promotion of ash utilisation in agriculture as a soil conditioner.
Moreover, the amendment has issued certain directives relating to transportation of fly ash. It states that every coal- or lignite-based TPP has to install dedicated dry ash silos with separate access to roads with the objective of easing the delivery of fly ash. The TPPs will also promote, adopt and set up ash-based product manufacturing facilities on their premises or in the vicinity of their premises to reduce the distance for the transportation of fly ash. TPPs situated in the vicinity of cities will promote, support and assist in setting up ash-based manufacturing units to meet the requirements of bricks and other building construction materials, and to reduce transportation costs. The amendment requires TPPs to comply with the new provisions in addition to 100 per cent utilisation of the fly ash generated by them, by December 31, 2017.
Coal washing norms
The MoEFCC brought out guidelines for coal washing in September 1997. As per the guidelines, power plants that are more than 1,000 km away from the pithead (and those located in urban, sensitive or critically polluted areas) are required to use coal with less than 34 per cent ash content. These guidelines were made effective from June 2001.
On January 1, 2014, the MoEFCC amended these guidelines, making it mandatory for the following coal-based TPPs to use raw or blended or beneficiated coal with ash content not exceeding 34 per cent on an average quarterly basis:
- A stand-alone TPP of any capacity, or a captive TPP of 100 MW or above capacity located beyond 1,000 km from the pithead or in an urban area or an ecologically sensitive area or a critically polluted industrial area, irrespective of its distance from the pithead, except a pithead power plant, with immediate effect.
- A stand-alone TPP of any capacity, or a captive TPP of 100 MW or above capacity located between 750 km and 1,000 km of the pithead, with effect from January 1, 2015.
- A stand-alone TPP of any capacity, or a captive TPP of 100 MW or above capacity located between 500 km and 749 km of the pithead, with effect from June 5, 2016.
However, these provisions are not applicable to a TPP using circulating fluidised bed combustion or atmosphere fluidised bed combustion or pressurised fluidised bed combustion or integrated combined cycle technology or any other clean technologies as may be notified by the central government.
Loading, unloading, storage and transportation guidelines
The fly ash utilisation guidelines issued by the MoEFCC in November 2009 called for the transportation of fly ash in an environment-friendly manner. However, no separate directives were issued for the same. In 2013, the Supreme Court directed the Central Pollution Control Board (CPCB) to frame guidelines pertaining to loading, unloading, storage and transportation of the fly ash generated by TPPs. The CPCB came out with the same in December 2013. The key guidelines issued by the CPCB include:
Maximising dry collection
- Coarse fly ash from the first field electrostatic precipitator (ESP) hoppers to be collected and stored separately in a coarse fly ash silo. Similarly, fine ash from the second field onwards of the ESP hopper to be collected separately.
- Bottom ash to be collected in dry form. Wet collections and disposal of bottom ash to be minimised as much as possible.
Loading, unloading and storage
- Installation and periodic maintenance of bag filters with dry fly ash collection and storage in silos at loading and unloading points.
- Installation of a weighbridge under the fly ash loading chute.
- Closure of the openings of tankers used for transportation.
- Transportation through polyvinyl chloride-coated mild steel pipes rather than through a pneumatic system.
- Construction of fly ash storage silos using anti-abrasive and anti-corrosive materials.
- The suggestions for transportation have been made for different fly ash and bottom ash end-user industries/ functions. These include cement asbestos manufacturing; fly ash-based brick, tile and block manufacturing; mine/abandoned quarry backfilling; and road construction and filling of low-lying areas.
- A key suggestion pertains to the deployment of tankers/bulkers or mechanically covered trucks for the purpose of transporting fly ash.
Adherence to these norms assumes immense significance as indigenous coal varieties are known to have a high ash content of 35-45 per cent. While the guidelines suggest various measures and ways to curtail the deleterious effects of fly ash on the environment, effective implementation and proper coordination are required, along with action against the defaulters to ensure timely compliance.