An important element of the renovation and maintenance strategy of thermal power plants (TPPs) is their compliance with environmental norms. Aimed at regulating the pollution by TPPs, the Ministry of Environment, Forests and Climate Change (MoEFCC) had revised the standards for emissions from TPPs in December 2015. Existing plants were given two years, that is, up to December 2017, to comply with these revised standards, and plants to be commissioned after January 1, 2017 were required to ensure compliance from the start of operations.
In order to meet the new standards by the stipulated deadline, new emission control systems, including flue gas desulphurisation (FGD) systems and electrostatic precipitators (ESPs), needed to be installed and retrofitted at power plants. For this, the Central Electricity Authority (CEA) had prepared a region-wise implementation plan as per which the countrywide installation was planned to be completed by December 2023. After several rounds of discussions with the Ministry of Power (MoP) and MoEFCC, it was decided that all plants must meet the norms by 2022.
The revised phased implementation plan (to be implemented by 2022) for the installation of FGD systems and upgradation of ESPs was prepared by the CEA in consultation with the regional power committees and MoP, and submitted to the MoEFCC on October 13, 2017. As per the revised plan, FGD systems will be installed in 414 units with an aggregate installed capacity of about 161 GW and ESPs will be upgraded in 231 units with a capacity of about 66 GW. In December 2017, the Central Pollution Control Board (CPCB) issued directives to TPPs to ensure compliance as per the revised plan. Power Line takes a look at the emission control requirements and the implementation plan…
Emission norms
Apart from tightening the existing standards of suspended particulate matter (SPM) emissions, the ministry issued new standards pertaining to nitrogen oxide (NOx) and sulphur oxide (SOx), which did not exist earlier. TPPs have been classified into three categories: units installed before December 31, 2003; installed after 2003 till December 31, 2016; and units installed after December 31, 2016. Different emission standards have been set for the three categories. For TPP units older than 2003, the norms are relatively relaxed as compared to plants commissioned thereafter and for under-construction plants. Further, the SOx and mercury emission standards are more stringent for plants with a higher capacity (more than 500 MW).
Revised plan
Different technologies have been identified to control different types of emissions. For meeting PM norms, plants are required to retrofit/upgrade/install ESPs; for meeting SOx emission norms, FGDs will have to be installed; and for reducing NOx emissions, plants need to install selective non-catalytic reduction (SNCR) and selective catalytic reduction (SCR) technologies. Besides SCNR and SCR systems, the CPCB has also suggested that plants should undertake pre-combustion modifications in boilers, and install low NOx burners and over-fire air systems.
As per the submissions of the regional power committees and the CEA, about 72 GW (36.5 per cent) of the total coal-based capacity of 197 GW is non-compliant with the new PM norms and requires retrofitting or upgradation of ESPs. Of this, ESPs are planned to be upgraded across 231 units iwth 66 GW of capacity. Meanwhile, FGD systems are planned to be installed in plants aggregating about 160 GW of capacity. This capacity excludes plants that are already retired or are planned to be retired (8,217 MW), that have already installed FGD or circulating fluidised bed combustion boilers (12,974 MW) or do not have space to install FGD (16,789 MW).
Retrofitting/Replacement of ESPs requires a complete shutdown of four to six months for each unit. FGD installation, on the other hand, requires 30-36 months for the entire process, including design and engineering, regulatory approvals, arrangement of funds, tendering, erections and commissioning. Since all the plants cannot be shut down simultaneously, the implementation has to be planned in such a manner that sufficient capacity is operational at all points of time. With respect to SNCR and SCR, these technologies are not established for coal with high ash content and hence, are required to be validated for Indian coal. Pilot implementations are being undertaken at nine NTPC units to study SNCR and SCR technologies. The revised plan for the implementation of the new norms, thus, has been prepared considering the above-mentioned points and the techno-economic feasibility of the technologies while ensuring that affordable and regular power is available to all.
Further, the installation of FGD and other pollution control equipment at TPPs has been prioritised in the national capital region, near large habitations and in critically polluted areas in the phasing plan. A majority of the units will complete the installation of these technologies in 2021 and 2022. Around 350 units (128.7 GW) out of 414 units (161.4 GW) will complete the installation of FGD systems in 2021 and 2022, and 200 units (53.4 GW) out of 231 units (65.9 GW) will complete the upgradation of ESPs in these two years (see figures).
Issues and challenges
To begin with, a huge demand for the installation of FGDs is going to be created simultaneously in a short period, given the short time frame for implementation. This could result in bottlenecks in the timely supply of equipment and installation. Another key issue in the implementation of emission control technologies is the requirement for design modifications in upcoming units. Such units are likely to face delays in commissioning and an increase in project costs due to the required modifications. The plants will also be required to re-work their power purchase agreements in order to account for the cost of implementing the technologies. With these technologies, auxiliary power consumption and operations and maintenance costs will also increase, which will, in turn, affect plant efficiency.
Further, one of the key raw materials for the operation of FGDs is good quality limestone. A 500 MW unit requires approximately 60,000 tonnes of limestone in a year. This implies that about 27 million tonnes of limestone will be required per year for 225 GW of capacity. Availability and transportation of this huge quantity of limestone of appropriate quality will pose a major challenge in the achievement of the desired outcomes. Further, around 38 million tonnes of gypsum will be generated every year when all plants have operational FGDs. The disposal/utilisation of such a large quantity of gypsum is another area of concern. The MoEFCC is working out a way for the disposal of gypsum and calcium sulphite.
The way forward
With an extension of five years in the timeline for meeting the emission standards, power utilities are now required to adhere to the revised implementation plan for the installation of various technologies. Orders for emission control equipment are expected to pick up over the next two years in order to complete implementation by 2022. A capex of about Rs 1.3 trillion will have to be undertaken over the next five years in order to meet the emission reduction targets, as per an analysis by Mumbai-based Motilal Oswal Securities Limited. Around 40 GW of plants have already been tendered for the installation of FGDs, with over 80 per cent of the tenders issued by NTPC alone. The implementation of FGDs is already under way for 13.85 GW of NTPC’s capacity and notice inviting tenders have been issued for 24.65 GW of capacity, as per NTPC’s “Earning Conference Call for the third quarter of 2017-18”, held on January 31, 2018.
Meanwhile, suppliers need to upgrade their facilities to cater to such a huge requirement of FGD installations in a limited period of time and the government needs to ensure, through continuous monitoring, that power plants take the required measures and emissions are brought down progressively. Further, plants that do not have the space to install FGD systems are required to explore alternative measures such as the use of dry sorbent injection technology or the use of low-sulphur coal in order to comply with the new norms.