The function of thermal power plants (TPPs) is rapidly evolving due to changes in the fuel mix, driven by the increasing prevalence of intermittent renewable energy sources. While TPPs have traditionally served as the primary providers of baseload power, they are now increasingly tasked with supporting the grid. Furthermore, stringent environmental regulations and ageing thermal plant fleets pose challenges to generation efficiency and plant availability. Therefore, it is essential for generation companies to embrace advanced operations and maintenance (O&M) practices to adapt to evolving trends and requirements, ensuring smooth and efficient operations. To this end, the adoption of innovative digital solutions such as digital twins, industrial internet of things, artificial intelligence (AI) and machine learning (ML) is gaining momentum within TPPs. Developers are also utilising data analytics tools to enhance cyclic efficiency by identifying and mitigating energy losses.
Best O&M practices
Due to the growing integration of renewable energy sources, many TPPs are now required to operate at minimum technical loads. To maintain performance under these conditions, there is a growing emphasis on utilising secondary air damper control tools. These tools help achieve the optimal mill combination and maintain an ideal boiler temperature. Additional strategies such as burner optimisation, reduced mill operation, advanced process control, predictive analytics, and enhanced digitalisation for monitoring boiler and turbine feeds are also being employed to ensure plant performance during flexible operations.
The heat rate of a power plant is a critical factor that directly impacts profitability. Heat rate degradation, often caused by high energy drain valve passage, must be closely monitored. Strategies such as optimising cooling tower fans, cleaning condenser tubes, and regularly monitoring terminal temperature differentials of heaters are being implemented to improve heat rate efficiency. Pile age monitoring at the fuel level is also crucial for minimising heat loss and maximising heat value utilisation. Advanced coal blending techniques are being adopted to optimise fuel usage efficiently and cost-effectively.
The use of gamma rays is gaining popularity for monitoring emissions, assessing electrostatic precipitator hopper emptiness and scheduling maintenance accordingly. Exfoliation meters are employed to monitor oxide layer deposition in coils, while small oil igniting systems and phased array ultrasonic tests help identify metallurgical flaws. Implementing an oxygenated treatment cycle chemistry programme can reduce corrosion and iron carryover. Other O&M practices include furnace mapping for combustion evaluation, equipment changeover scheduling, cross-checking air preheater intake with gas analysers, and managing boiler tube leakage and smart soot blowing.
To enhance operational efficiency, power plants should prioritise maximal mechanisation with minimal manual labour. Examples include the use of electric impact wrenches, powered gantry cranes, portable plasma cutting machines, and battery-operated cranes and trolleys. Additionally, utilities can focus on key operational areas while outsourcing less critical tasks to partners who adhere to strict performance indicators. Inventory management can be optimised through vendor-managed inventories and annual rate contracts for fast moving items.
Emerging trends in O&M
In recent times, there has been a growing trend towards adopting new and innovative technologies to enhance O&M efficiency. For example, utilities are increasingly leveraging data analytics, ML and AI to monitor operating parameters and detect deviations or faults early on. By employing these advanced tools, utilities can improve their cyclic efficiency by identifying and addressing energy losses.
Furthermore, utilities are implementing reliability-centred maintenance (RCM) strategies aimed at enhancing the reliability of power plants. RCM focuses on analysing the risk and cost associated with maintaining specific equipment to prioritise maintenance activities effectively. This approach integrates preventive, predictive, real-time, reactive and proactive maintenance techniques to maximise equipment availability while minimising maintenance costs. RCM emphasises reliability over availability and takes a proactive approach to prevent failures rather than reacting to them. It utilises real-time data for analytics and predictions, enabling engineers to identify opportunities for reliability improvement and receive automatic notifications when equipment health deteriorates beyond a certain threshold.
A comprehensive maintenance strategy involves conducting root cause analysis for various types of equipment failures, generation losses, and mean time between breakdowns to optimise O&M activities. Utilities also perform failure mode and effects analysis to prioritise maintenance based on the severity, frequency, detection rating and financial impact of potential failures.
To ensure uninterrupted operations, utilities are developing zero-forced-outage plans for critical equipment and operations. Additionally, they are implementing preventive maintenance methods tailored to different equipment categories and strengthening condition-based maintenance practices. These efforts collectively contribute to maximising equipment reliability, minimising downtime and optimising resource utilisation in the utility sector.
Fly ash and water management
Indian coal has a high ash content, leading to significant ash generation from coal-based power plants. The improper handling and storage of fly ash by these plants have adverse health effects on local residents and contribute to air and water pollution. Therefore, it is necessary to dispose of or repurpose fly ash in a scientifically managed manner. Various methods can be used to effectively utilise ash, including its incorporation into the building sector for making bricks, blocks, tiles, cement, concrete and plaster. Additionally, it can be used as a base for land reclamation, filling low-lying areas, raising ground levels and filling mines. Furthermore, it can be utilised in construction projects such as roads, embankments, ash dykes and roadblocks. Fly ash can also be used in agricultural and wasteland area development, among other applications.
Coal-based TPPs in India are major consumers of water, utilising around 70 per cent of the total industrial water. Water is vital for various plant operations, such as cooling towers and ash handling systems, leading power plant operators to recognise the necessity of reducing water usage through improved efficiency practices and technological advancements. TPPs have diverse water needs, including coal and ash handling, steam production, condensation, maintenance, firefighting and domestic purposes. Cooling processes, especially in coal-based TPPs, account for the largest water demand, typically 80-90 per cent of the total requirement. Thus, enhancing water efficiency primarily focuses on improving cooling technologies.
An emerging technology in this regard is the air-cooled condenser, which uses dry cooling to condense steam inside air-cooled tubes, reducing the need for large volumes of cooling water and making it suitable for regions facing water scarcity. Increasing the cycles of concentration (CoCs) of cooling water is crucial for water conservation in cooling systems. Elevating CoCs helps reduce the amount of blowdown and makeup water needed. While many systems operate at two to four CoCs, achieving six cycles or more is feasible. Furthermore, TPPs are transitioning towards zero liquid discharge (ZLD), deploying advanced wastewater treatment technologies to purify and recycle all wastewater generated, making it reusable within the plant. A ZLD system employs various technologies to recover, recycle and reuse treated wastewater, effectively closing the water loop within the plant.
Conclusion
Effective O&M practices have become increasingly important in coal-based power generation, particularly due to challenges such as changing fuel mixes, flexible operation requirements, and stricter environmental and safety standards. By employing the best O&M practices, power plant operators can achieve high performance levels and ensure the longevity of their equipment. Looking ahead, there is expected to be growing adoption of O&M strategies and digital solutions to support sustainable operations for power generation companies in the future.