Digital Tools

TPPs turn to a suite of solutions for safe and flexible operations

Digitalisation holds big promise for the power industry. It can help reduce emissions, enhance plant efficiency, and manage grid stability given the growing renewable energy capacity. However, many power plants are still operated manually. This calls for digitalising the existing power plants through sensors and remote monitoring so that plant data can be captured and processed to help improve performance. Besides, constant monitoring of the temperature and pressure of coal with digital tools can help manage emissions and improve efficiency.

Benefits of digitalisation

The concept of a digital twin has gained traction in the power sector. It offers a number of benefits, including improved efficiency, for a power plant. It creates a digital model for feedback of the plant’s characteristics and helps the power plants to leverage big data for driving efficiency and generation. The digital twin can be made available in different configurations, covering the complete power plant including boiler, turbine, generator and balance of plant system. The overall objective is to build a model of power plant behaviour. There are two digital models for this – thermodynamic model (TDM) and machine learning model (MLM). TDM is based on thermodynamic equations with data input. It is a traditional approach based on the conservation of mass and energy. MLM, meanwhile, is based on training data, that is, input plus measured output. It is equipped to automatically detect the most relevant input data based on actual operations data and remove systemic errors.

Digital solutions and applications

Digital applications are being used to achieve maximum steam temperature in the boiler without violating material limits. Temperature optimisers are robust and easy to parameterise, and are equipped with adaptive state space controllers. Also, they can be used during start-up/shutdown and over the entire load range. They can also work as a solution to control the reheat steam temperature. The deployment of such solutions can improve efficiency and reduce reheater attemperation. Further, digital solutions can be effectively used for more accurate evaluation of operational history (EOH) and the implementation of state-of-the-art EOH solutions. A key challenge for operators is that thermal stresses during operation are not considered in EOH. As a result, maintenance needs may not be recognised. EOH solutions are applicable when part load leads to steam temperature changes, especially reheat temperature. These solutions can provide better outage planning as well as enhanced operational flexibility. Soot blowing optimisation is another important application for digital solutions in power plants. Through this, the cleanliness factor of heating surfaces can be monitored. It is observed that many times cleanliness does not change uniformly over time, indicating that the deposition of soot is not uniform over time. Thus, instead of soot blowing at regular intervals, an information-based decision can be taken for blowing the soot. The monetary benefit of using digital solutions at this stage is around Rs 1 million per annum, based on the amount of demineralised water saved and loss of steam.

Another use case for digital solutions is signal improvements since one or more bad signals could lead to high chances of tripping. This requires focus on signal quality improvement. All signals can be configured in one human machine interface for quality checks so as to prevent a unit from tripping due to bad signals and poor maintenance.

Digital solutions can also help in merit order despatch. In a multi-unit plant, it is possible to meet the demand for power and steam in more combinations and attain the optimum capacity utilisation factor by loading highest efficiency machines more and lowest efficiency machines less. With real-time monitoring, digital tools can provide the right combination of steam and power to be taken from each unit to achieve overall optimum generation. Typically, the performance improvement that can be attained through a merit order despatch is about 0.1 per cent. Furthermore, an optimum fuel mix can be achieved using advanced solutions. Real-time boiler efficiency can be determined based on the type of fuel used. After analysing patterns over the long term, it is possible to optimise boiler efficiency. Boiler leakages can also be plugged with the help of digital solutions, which reflect power decreases at the steam turbine level in real time. This is detected by comparing the expected and measured value recorded in the system. Digital solutions can record the heat rate based on the actual performance of steam turbines and report deviations, if any. Further, if there is insufficient condenser vacuum, it can compare the expected and measured values, and calculate deviations and flag issues, if any. The root cause of such a vacuum could often be two plastic nets in a pipe, which may cause leakage.

Conclusion

A key advantage of digitalisation is efficient operations management. In addition, digital plants can help monitor the emissions of a power plant in real time. This helps in saving reagent costs, while keeping a check on the pollution level. Another benefit is flexible plant operations. With regard to power evacuation from a renewable energy plant vis-à-vis a fossil fuel plant, digitalisation can help in decision-making by factoring in projected generation from wind energy, solar energy, etc.

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