Enhancing Efficiency

R&M experience of coal-based power plants

The renovation and modernisation (R&M) of thermal power plants (TPPs) is undertaken primarily to equip existing units with the latest technologies in order to improve their performance in terms of output, reliability and availability, reduce their maintenance requirements and enhance efficiency. However, R&M is not a substitute for regular annual or capital maintenance/overhaul. R&M helps bring down the O&M requirements of TPPs and reduces forced shutdowns, resulting in higher uptime and thus higher revenue. In recent times, the key growth drivers for R&M have been tightened emission norms and flexibilisation requirements.

A look at these new R&M requirements and the recent R&M projects in the country…

Changing requirements

In December 2015, the Ministry of Environment, Forest and Climate Change notified and revised the emission norms (including particulate matter, sulphur oxides and nitrogen oxides) for TPPs. To meet the norms, power plants are required to install/retrofit various technology solutions such as electrostatic precipitators (ESPs), flue gas desulphurisation systems, and selective non-catalytic reduction and selective catalytic reduction systems. Undertaking R&M of the existing emission control equipment can also help in reducing emission levels as seen in the case of the Guru Nanak Dev TPP at Bhatinda. After R&M of the ESP installed at the plant, the suspended particulate matter (SPM) emissions decreased from 140 mg per Nm3 to less than 100 mg per Nm3.

Another emerging application of R&M pertains to the flexibilisation of TPPs. With the increasing penetration of renewable energy, maintaining grid stability and security has become a challenge. Flexible operation requires frequent and rapid ramp-up and ramp-down of power plant capacity. While power plants operating on supercritical technology offer flexibility in operations, old power plants experience severe deterioration in performance under flexible operations. This can be avoided with appropriate R&M measures. These include reduction in mill size, increase in the number of mills, installation of advanced burners and indirect firing systems in boilers, and the use of special alloys for improved material strength.

R&M experience

Since 1985, when the R&M programme was initiated as a sponsored scheme by the central government, R&M/life extension (LE) works have been completed at almost 650 coal-based units with an aggregate capacity of over 80,000 MW. Of this, over 50,000 MW of capacity underwent R&M/LE in the first 15 years of the launch of the programme. However, the pace of implementation of R&M/LE slowed down during the Tenth Five Year (2002-2007) Plan period, which witnessed R&M works at units aggregating 3,500 MW only, the lowest in any plan. The R&M programme implemented during the above plan periods focused primarily on improving plant availability. In the Eleventh Plan period (2007-2012), the pace of R&M/LE works picked up with around 17,000 MW of capacity undergoing R&M. In the Twelth Plan period (2012-2017), R&M/LE works were carried out at 7,200 MW of units.

Since April 2017, no R&M project has been completed. However, a few thermal units were shut down in 2017-18. These include Unit 7 (100 MW), Unit 12 (200 MW) and Unit 13 (200 MW) of Uttar Pradesh Rajya Vidyut Utpadan Nigam’s Obra TPP, Unit 6 (110 MW) of Bihar State Power Generation Company Limited’s Barauni TPP and Unit 6 (210 MW) of Maharashtra State Power Generation Company Limited’s Koradi TPP. LE works were completed by Gujarat State Electricity Corporation Limited at two units aggregating 410 MW. These included the 200 MW Unit 4 of the Ukai thermal power plant (TPP) and the 210 MW Unit 3 of the Wanakbori TPP.

Planned R&M projects

In the Thirteenth Five-Year Plan (2017-22), 63 projects totalling 14,580 MW have been identified by the Central Electricity Authority (CEA) for LE/R&M works across the state sectors. Of these, as of December 2017, 31 units aggregating 7.4 GW, all of which are in the state sector, were yet to be awarded. The LE works identified for 2017-22 include 34 units aggregating 7,570 MW in the state sector. R&M works identified for 2017-22 include 29 units (7,010 MW) of the state.

Issues and challenges

Even in greenfield thermal and hydro projects, R&M works are being delayed.  Further, utilities usually award R&M works to original equipment manufacturers (OEM), which often take up R&M contracts on a negotiated basis, resulting in increased R&M costs for the utility. Often, when a plant/unit is opened up for R&M/LE, new defects and damaged equipment are noticed, for which additional materials have to be procured, leading to time delays and increase in costs. The contract document often does not address these technical surprises.

Another key reason for the slow growth of R&M in India is that power generating units have to be shut down for six to eight months. Not many utilities are willing to do so and face a subsequent loss of revenue. Also, obtaining regulatory clearances for plant shutdowns for R&M works is a tedious process. Further, there is a lack of specialised entities for conducting residual life assessment (RLA) studies of power plants efficiently. Constraints are also faced in defining the scope of work and guarantees.

Conclusion

There is an urgent need to renovate and modernise older power plants in the country for efficient power generation and optimal utilisation of resources. To this end, it is important to ensure data monitoring, robust reporting and maintenance, adequate assessment, minimum time lag between technical studies (RLA, detailed project report preparation, etc.), and the actual award of contract and commencement of R&M works. Further, adequate regulatory support is needed to achieve the desired results. Utilities also need to adopt effective O&M practices.

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