Since the Ministry of Environment, Forest and Climate Change (MoEF&CC) notified new emission norms for thermal power plants (TPPs) in December 2015, gencos have been chalking out a number of strategies to ensure that TPPs comply with the new norms. They are actively working to deploy various emission control systems including flue gas desulphurisation (FGD), selective catalytic reduction (SCR), selective non-catalytic reduction (SNCR) and electrostatic precipitators (ESPs) to ensure that their TPPs are able to meet the norms in a phased manner by 2022.
A look at the progress and plans for the installation of emission control systems of some of the leading private gencos…
With regard to suspended particulate matter (SPM), almost all the company’s units are already meeting the PM requirement. For meeting SO2 emission norms, plans are under way to install FGD systems at the 4,000 MW Mundra power plant of Coastal Gujarat Power Limited, the 2×520 MW Maithon power plant and the Jojobera plant as well as two regulated units, which are supplying power to the Jamshedpur Distribution Company. Further, FGDs are planned for the 3×660 MW Prayagraj power project of Renascent Power, which is a Tata Power group company.
Since Mundra is a coastal plant, the company is considering using a seawater-based FGD system. Since cooling seawater is already available near the plant, the company will use condenser return cooling water for scrubbing the flue gas. In the case of Maithon, wet limestone-based FGD is being considered on the basis of life cycle cost analysis. In the case of Jojobera Unit 1, which has a life of around 10 years, the company is exploring semi-dry-type or wet FGD technology. For the Prayagraj plant, it plans to install wet limestone-based FGD.
For NOx abatement, the company is looking at meeting the norms through in-combustion modifications. Also, it is exploring other technologies like SCR and SNCR, for which it is already in discussion with various SNCR vendors. For Jojobera Units 1-3, the prescribed limit is 600 mg per Nm3, which will require only combustion tuning.
The company’s 1,400 MW Rajpura TPP is compliant with the specific water consumption norms, for which the applicable limit is 3.5 m3 per kWh. The plant is SPM compliant as well. The entire power generated from the TPP is contracted with Punjab State Power Corporation Limited for a period of 25 years under a power purchase agreement for the exclusive benefit of Punjab.
For SOx abatement, the company is in the process of FGD installation. Its plant uses domestic washed coal and has SO2 emissions in the range of 1,600-1,800 mg per Nm3. It has selected wet limestone-based FGD as the most suitable technology, given the size of the plant. The company has already placed the order for the installation of FGD through international competitive bidding. The engineering and construction work for the same has started, but the work has currently been impacted due to Covid-19. The installation is expected to be completed by 2022.
For sourcing limestone, the company is tying up with cement manufacturers, who can purchase on behalf of Nabha Power and supply to them. The company is also looking at the long-term disposal of gypsum. Limestone consumption is expected to be close to 0.12 million tonnes per annum (mtpa) and gypsum generation will be around 0.2 mtpa.
For NOx abatement, combustion tuning has been done and low NOx burners have been installed, besides an over fire assembly. Further, with the expected revision in the NOx abatement limit by the MoEF&CC to 450 mg per Nm3, the plant will become NOx compliant.
CESC has three plants – two in West Bengal and one in Maharashtra. Units 1 and 2 of the Budge Budge TPP (3×250 MW) in West Bengal, commissioned in 1997-98, are more than 23 years old, while Unit 3, commissioned in 2010, is 10 years old. The 2×300 MW Haldia TPP (in West Bengal) and the 2×300 MW Dhariwal TPP (in Maharashtra) are fairly new, around five to six years old. With respect to PM and specific water consumption norms, all the stations are operating well below the norms. The company is focusing on being SOx and NOx compliant. It has undertaken due diligence and has decided to go ahead with wet limestone-based FGD for all its thermal power stations, given its higher uptake than ammonia-based FGD. The company has completed the feasibility studies and is now working on the tender specifications for all the three stations.
CLP India’s 2×660 MW Jhajjar power plant was built in 2012-13. At that time, the new environmental norms were not in place, though the company had installed an emission control system. With the existing facility, therefore, the plant has become compliant with environmental norms. The FGD system in the Jhajjar plant has been fully operational since February 2019. In fact, in the Delhi-NCR region, it is the only plant that is SOx compliant.
For PM control, the plant has a hybrid system with an ESP and a fabric filter, which has made it PM compliant. Normally, the plant operates in the range of 20-30 mg per Nm3 for PM, which is far below the prescribed limit of 50 mg per Nm3. The company is expecting a revision in NOx emission norms, which will make them NOx compliant too.
Challenges and the way forward
One of the initial challenges that companies faced was with respect to technology selection, as there was a lack of domain expertise, and a paucity of vendors and suppliers. However, discussions were held with domestic as well as international vendors to understand the best suitable technology. Further, in December 2017, the Central Electricity Authority came out with a notification, which gave detailed specifications for plants of more than 500 MW capacity for greater clarity.
During the tendering process, a key issue that gencos have raised is with regard to vendors’ availability, given that the latter were initially tied up with bulk tenders. This was a challenge for single-plant owners and hence, such plants saw an extension of tender dates and, consequently, a delay in implementation. Further, the current Covid-19 pandemic has led to delays in meeting stipulated tight deadlines and in project execution, as engineering, procurement and construction vendors have sought time extensions owing to the nationwide lockdown in April and May 2020. Another issue has been the cost pass-through and regulatory challenges involved. Lack of clarity on auxiliary power consumption and opex, in fact, continues to pose a lingering issue. With the Central Electricity Regulatory Commission releasing the draft regulation for the recovery of the capex and opex of FGD, the issue could likely be addressed in the near future after discussions. There is also an issue with cost recovery for the untied capacity for FGD installation cost. Another issue is with regard to the sulphur content in coal. If it is higher, that is, beyond the prescribed 5 per cent, then it can lead to higher SOx emissions. Space constraints in the already existing plants is an additional challenge.
Gencos have also been facing challenges with regard to meeting the NOx norms. Most companies are unable to meet the existing NOx norms, so there is a need to revisit them. With the MoEF&CC planning to revise the NOx norms, gencos are hopeful of meeting them. Further, there are technology constraints in the market, as gencos feel that the current SCR/SNCR technologies have not been found suitable to meet the norms for bigger capacity plants, especially those exceeding 500 MW.
To conclude, various challenges such as Covid-19, followed by supply disruptions from China, have posed problems in meeting the December 2022 deadline. Going forward, adherence to environment norms in a timely manner will largely depend on gencos’ efforts, government’s push and timely delivery by contractors.
Based on remarks by Siddharth Ghosh, General Manager (Operations), CLP India; Rajesh Kumar, Head (Operations), Nabha Power Limited; Saikat Majumdar, Chief Manager (Operations), Haldia Energy Limited; and C.P. Tiwari, Head (Technology and Process Engineering), Tata Power, at a recent webinar organised by Power Line