The Ministry of Environment, Forest and Climate Change (MOEF&CC) notified new emission norms for thermal power plants (TPPs) in December 2015 with an objective to reduce the emission of major pollutants such as particulate matter (PM), sulphur oxide (SOx), nitrogen oxide (NOx) and mercury. In order to meet the standards, new emission control systems, including flue gas desulphurisation (FGD) and electrostatic precipitators (ESPs), are required to be installed at TPPs in a phased manner by 2022. For TPPs located in critically polluted areas, including Delhi-NCR, the target date for compliance is December 2019. In June 2018, the environment ministry notified water consumption as well as chimney height limits for TPPs with FGDs.
The new norms lay considerable emphasis on reducing SOx emissions. SOx emissions, which are currently as high as 1,000-1,200 mg per Newton cubic metre (Nm3), have to be brought down to 600 mg per Nm3 for units that are 15-25 years old. For five to seven-year-old units, the emission level needs to be reduced to 300 mg per Nm3, and the latest commissioned units need to limit their SOx emissions to 100 mg per Nm3.
In terms of NOx emissions, the new norms mandate TPPs installed before December 31, 2003 to limit their emissions to 600 mg per Nm3. For plants installed between December 31, 2003 and December 31, 2016, the limit is fixed at 300 mg per Nm3 and for those installed after December 31, 2016, it is 100 mg per Nm3.
The limits for PM range between 30 mg per Nm3 and 100 mg per Nm3 depending upon the age of the plant with the latest units having stricter limits. Further, mercury emissions have been capped at 0.03 mg per Nm3 for all TPPs.
FGD and ESP installation plan
As per the Central Electricity Authority’s FGD phasing plan, about 166,917 MW of thermal power capacity spread across 441 units is required to install FGD systems between 2018 and 2022. About 12,790 MW of this capacity (across 33 units) is located within a 300 km radius of Delhi-NCR.
However, implementation has been tardy with FGDs being commissioned in only three units aggregating 1,820 MW, as of June 2019. All three units belong to the private sector. These are two 660 MW units of CLP India’s Mahatma Gandhi Thermal Power Station (TPS) in Jhajjar (Haryana) and one 500 MW unit of Tata Power’s Trombay TPS in Mumbai, (Maharashtra).
The tenders for installing FGDs have been issued for capacity aggregating 95,325 MW or 57 per cent of the targeted capacity while bids have been awarded for 13,860 MW (8.3 per cent), as of June 2019. Further, feasibility studies have been undertaken for capacity totalling 161 GW (97 per cent of the targeted capacity), completed for about 136.6 GW (82 per cent), and tender specifications are ready for 106.4 GW (63.8 per cent).
Bharat Heavy Electricals Limited (BHEL) has won a significant chunk of FGD orders so far. As of August 2019, the company had secured 23,000 MW of orders for FGD and emission control equipment. In addition, BHEL is in L1 position for about 19 GW of capacity that is in the bidding pipeline. Tenders for another 30 GW are expected to be floated in 2019.
As per the ESP upgradation plan prepared by the CEA, 220 thermal power units of 63,425 MW capacity are to be covered between 2018 and 2022.
NOx control
As per a study by the Centre for Science and Environment, of the 197 GW of installed coal capacity in the country, about 187 GW has to meet the NOx emission norms of either 600 mg per Nm3 or 300 mg per Nm3, based on the plant commissioning dates. These plants do not have to implement secondary methods for NOx emission control as compliance with the norms can be achieved through primary methods. Meanwhile, about 10 GW of capacity, or 5 per cent of the total coal-based capacity, has to meet the 100 mg per Nm3 standard. These projects will need to opt for secondary methods of NOx control such as selective catalytic reduction (SCR) and selective non-catalytic reduction (SNCR).
Many TPPs have started installing primary control systems for NOx reduction and around 50 per cent of the power plants already comply with the relevant NOx norms (300 mg per Nm3 or 600 mg per Nm3).
In April 2019, NTPC Limited awarded a Rs 1.42 billion contract to GE for the supply and installation of low-NOx combustion systems for 10 GW of TPP capacity across the country. This is the first large-scale project that NTPC has awarded for installing low-NOx combustion technology at its TPP fleet. The company has seven SCR and two SNCR pilot tests under execution by seven vendors. It is also implementing combustion tuning in thermal power units installed before December 2003. The outcome of the NTPC studies on SCR and SNCR systems is expected to pave the way for the implementation of post-combustion de NOx systems in the country.
In a key development, the MOEF&CC has, in-principle, agreed to change the NOx norms for TPPs installed between January 1, 2004 and December 31, 2016 from 300 mg per Nm3 to 450 mg per Nm3. Further, revision of NOx norms for TPPs installed after January 1, 2017 is under consideration by the environment ministry.
Challenges
Developers are facing many challenges in the implementation of SOx norms. Limited availability of SOx control equipment vendors and the lack of skilled manpower for the implementation of these systems is a key challenge. Further, time constraint is another issue as the installation of an FGD system in a thermal power unit takes about three years from the date of order placement followed by the shutdown of the unit for two to six months depending upon the technology adopted by the TPPs. A minimum time of about six months is required for bidding and finalisation of a tender. In addition, obtaining and transporting limestone to the TPP site is a problem.
The capex requirement of FGD systems is also significant. The bidding price for wet-type FGD varies from Rs 3 million per MW to Rs 6 million per MW depending upon location, type of unit, coal quality, age of units, etc. Considering an average cost of about Rs 4.5 million per MW for installing an FGD system, the total capex for 166 GW of existing and 50 GW of under-construction capacity comes to about Rs 972 billion. There is a cost associated with generation loss during FGD installation. The plant’s operational expenditure increases after FGD installation on account of increase in auxiliary consumption by 1-2 per cent, increase in heat rate as well as additional costs of limestone and gypsum disposal. Air quality control systems also restrict the load operation of TPPs, thereby reducing their flexibility.
There are similar challenges in meeting the PM norms. Currently, the common technologies used for PM control are electrostatic precipitators (ESPs), fabric filters, and microprocessor-based control. Upgradation/Augmentation of ESPs requires the shutting down of the unit for four to six months. The cost of installing PM control equipment stands at about Rs 2.5 million per MW and this translates into a total capex of Rs 163.5 billion for the capacity that needs to be implemented under the ESP upgradation plan.
In order to help developers in meeting the new norms, the MoP and CEA are taking various steps. In a letter dated May 30, 2018, the MoP issued directions to the CERC to consider the costs related to the implementation of new environmental norms under change in law provisions and allow them as pass-through in tariffs. In December 2017, the CEA issued standard technical specifications for retrofitting wet limestone-based FGD systems in a typical 1,000 MW coal-based power plant. The CEA has taken up the matter of limestone requirement of power plants with the Ministry of Mines. The CERC and state electricity regulatory commissions have directed developers to approach the CEA to decide optimum technology, associated cost and other issues related to emission control equipment. The CEA is suggesting the technology and cost to IPPs on a case-by-case basis as the deployment of emission control technology depends on various factors such as unit capacity, plant load factor, configuration, heat rate, gross calorific value, the sulphur content in coal, fuel consumption, vintage of the unit, the use of reagent, by-product disposal, plant location and opex requirement.
Conclusion
The status of TPPs’ compliance with the new norms is below par owing to various challenges in implementation. Given the slow pace of implementation of various emission control systems by TPPs, the MoP is seeking to dilute the norms. Also, there are plans for according priority to plants installing emission control equipment in the merit order despatch. Going forward, the adherence to environment norms will largely depend on gencos’ willingness and the government’s push. n
With inputs from a presentation by Rajeev Kumar, Director, TPRM, Central Electricity Authority, at a Power Line conference