The operations and maintenance (O&M) of thermal power plants (TPPs) is critical to guarantee that they operate efficiently and without interruption. Adopting effective O&M methods has become essential in the coal-based power generating segment, given the constraints of a shifting fuel mix, flexible operation, and tougher environmental and safety requirements. Adopting the best O&M procedures at TPPs is important not only for achieving high levels of performance, but also for ensuring the health of the power plant equipment. But doing so requires a number of changes to the personnel, technology, procedures and infrastructure. The need to lower generation costs and enhance efficiency further encourages the adoption of O&M.
New and emerging requirements
TPPs are being subjected to numerous rounds of load cycling as a result of increasing renewable energy penetration, necessitating quick ramp-up and ramp-down capabilities. Due to pressure and temperature cycling, power plants are experiencing an increase in creep-related failure. Utilities must run their thermal units at the technical minimum load in order to be flexible. This may result in an unstable furnace during low-load operation, increasing the secondary heat rate and power generation costs, as well as secondary oil consumption on account of frequent reserve closures.
Apart from this, strict emission norms for sulphur oxides and nitrogen oxides have resulted in a high capex requirement for the installation of flue gas desulphurisation, selective catalytic reduction, and selective non-catalytic reduction, as well as an increase in opex, thus raising the cost of generation from TPPs even further. With the changing landscape and the difficulties facing TPPs, such as a shifting fuel mix, flexible operations, and tougher environmental requirements, effective O&M methods have become critical in maintaining ongoing operations.
Best O&M practices
Most TPPs have begun to operate under minimum technical load because of the integration of renewables. As a result, the secondary air damper control tool is gaining prominence for its utility in getting the best mill combination and maintaining an optimum boiler temperature. Gamma rays can be utilised to monitor emission levels, as they can be used to assess electrostatic precipitator hopper emptiness and schedule maintenance accordingly. Exfoliation meters are also becoming popular. They are used to monitor the deposition of oxide layers in coils. Furnace mapping can be used to evaluate boiler combustion and manage the furnace outlet temperature. Furthermore, the use of equipment changeover tools can aid in the scheduling of changeovers in accordance with SAP and the maintenance of equipment health.
Cross-checking the air preheater (APH) intake for oxygen and carbon monoxide with a potable gas analyser for combustion optimisation, and APH and duct in-leakage monitoring are some other operational practices. The heat rate of a power plant is a crucial metric that directly affects the profitability of a firm. Heat rate degradation is caused by high energy drain valve passage, and therefore it must be monitored on frequently basis. Optimisation of cooling tower fans and cleaning of condenser tubes should also be undertaken. Furthermore, at regular intervals, utilities should monitor the terminal temperature differential of heaters. Air ingress into the condenser can be detected using helium gas testing. Radiation loss can also be reduced by conducting an insulating study of essential pipes and the furnace area.
Utilities can create a robust maintenance strategy based on root cause analysis for various kinds of equipment, generation loss and mean time before breakdown. Based on the severity, frequency, detection rating, and financial impact of the failure, a failure modes and effects analysis (FMEA) of equipment should be performed. For essential equipment and operations, a zero-forced-outage plan should be developed. It is important to monitor the overhauling readiness index and the overhauling quality index. Other maintenance techniques for decreasing maintenance downtime include boiler tube leakage management and modular replacement of subassemblies and major assemblies. A preventive maintenance programme based on the equipment categorisation category must also be followed, alongside strong condition-based maintenance.
For effective O&M, new and innovative solutions are gaining traction. Among them are a small oil igniting system and a phased array ultrasonic test for the identification of metallurgical flaws. Drones can be used to measure the amount of coal heaps and examine bunkers, while robotics can be used to identify silting in underwater pipes. Thermal imaging of coal yards may also be used to cut down on heat loss. Meanwhile, an oxygenated treatment cycle chemistry programme can help decrease corrosion and iron carryover. In addition, cycle chemistry recommendations for start-up and flushing should be implemented, as well as cycle chemistry instrumentation, as recommended by the International Association for the Properties of Water and Steam. In addition, for smooth operations, a strategy of maximal mechanisation with minimal manual work can be used. Electric impact wrenches, electrically powered 2T gantry cranes, electric-operated rotor stands, portable plasma cutting machines, battery-operated pick and carry cranes, or Teflon wheel-mounted fabricated trolleys are all examples of mechanisation.
One of the essential procedures at the fuel level is pile age monitoring, which helps to decrease heat loss and maximise heat value utilisation. The coal blending technique should be used to make the most efficient and cost-effective use of the fuel. During technical minimum loading, selective bunkering would help in the use of low calorific value coal. To decrease inventory build-up, an inventory strategy should be established.
Machine learning, artificial intelligence and data analytics can offer several benefits. Data analytics, used to track operational parameters for reliable operation, can aid in the early discovery of deviations or faults. Through the identification of energy loss online and the recommendation of corrective steps, data analytics may aid in the development of cycle efficiency. It can also aid in optimisation of the maintenance strategy by limiting unplanned outages and removing needless preventive maintenance. Real-time monitoring of important parameter variations and condition monitoring can also be used to check the health of equipment.
Utilities should target and enhance key operational areas, while outsourcing non-important sectors to business partners that adhere to stringent KPI monitoring. Inventory management should be implemented using vendor-managed inventories and an annual rate contract for fast-moving items.
Challenges and the way forward
Going forward, coal-based units have to prepare for flexible operations and transition to cyclic operations as against baseload operations. This implies that not only will plant components deteriorate at a faster rate, there will also be higher O&M expenses due to the reduced life of components, additional costs owing to an increase in the heat rate and auxiliary power consumption, and an increase in oil consumption on account of frequent start/stops.
Utilities should therefore establish best-in-class O&M procedures to achieve business excellence and ensure long-term economic viability. To keep the cost of generation low, activity-based budgeting and cost-cutting measures, as well as optimal fuel mixing are required. Implementing new technology and focusing on innovation, automation and mechanised work to reduce manpower requirements are among the strategic goals. Root cause analysis, FMEA, reliability-centred maintenance, multi-year overhaul plans, zero-forced-outage strategies and systematic inventory management are some of the key maintenance procedures. Utilities should have a plant performance improvement suite and aim to reduce start-up time to achieve operational excellence and maximise plant availability and load factor.
Overall, the adoption of new and innovative technologies, cost savings and work mechanisation should be prioritised. Capacity building and training using augmented reality and hands-on maintenance work could enable TPPs to improve their O&M. Furthermore, best practices in O&M enable optimal solutions to the difficulties in the power industry, help maintain plant safety and availability, and enhance asset flexibility, while keeping maintenance costs at a minimum. These are unique solutions that cannot be generalised. To increase the performance of various units, a tailored strategy is required. n
Based on a remarks by Manasa Ranjan Rout, then Joint President, Operations and Maintenance, Adani Power