Testing and measurement (T&M) solutions are crucial for maintaining operational efficiency and optimising the operations and maintenance of power plants. They also play a vital role in maintaining the life expectancy of power plant assets. They are useful in early detection of failures or major deviations in power plant equipment, helping minimis equipment outage. Moreover, T&M solutions are useful for ensuring efficient fuel combustion in boilers and for monitoring power plant emissions. T&M solutions such as continuous emission monitoring systems (CEMS) and predictive emission monitoring systems (PEMS) are gaining traction for monitoring power plants emission levels and undertaking corrective measures in a timely manner.
CEMS
Gaseous components such as CO, NOx and SO2 need to be monitored continuously in the flue gas in the stack, along with gas flow, temperature and dust, to measure plant performance and emission levels. CEMS is a comprehensive solution for determining gas and/or dust concentration, accompanied by the required conversion to produce results in the units of the applicable emission limitation. CEMS deploys complex extractive analysers, which remove flue gas samples from the duct and use a series of individual gas sensor modules or more advanced spectroscopic techniques to determine the composition. Although stack measurements can be used in combustion control, it is preferable to analyse flue gas as close to the combustion process as possible. Such in-situ analysis can take the form of sensors placed directly in the flue gas, or line-of-sight optical absorption measurements, in which a transmitter and a receiver are placed on either side of the duct or furnace. CEMS provides continuous measurement of data on a real-time basis at the monitoring site of interest, even in the absence of skilled staff required to perform the analysis. In the sampling systems and online analysers, the corresponding major steps of traditional analysis such as sample collection, transportation, conditioning, calibration and analysis procedures are usually automated. In case of a sudden disturbance in the production process/pollution control system, the online analysers provide timely information and, accordingly, immediate corrective/preventive measures can be undertaken. Overall, CEMS can help gather real-time data, and allow plant operators to remotely access plant performance and continuous performance check of air pollution control devices/treatment methods.
PEMS
PEMS are software-based solutions that can provide reliable and accurate realtime emission estimations. PEMS entails the use of an empirical model to predict emissions based on historical and realtime process data. PEMS exist as standalone versions but are widely used as part of an integrated environmental monitoring approach, capable of addressing multiple sources in one plant. When combined with data acquisition and handling systems, and integrated in plant – wide IT and communications networks, PEMS can be a viable diagnostic tool for lowering emissions and improving combustion efficiency through surveillance of emission variations and associated changes in plant process conditions.
Drone applications
Drones are being increasingly deployed to remotely monitor power plant boilers, fuel storage tanks, transmission lines, turbines and chimney. Drones can monitor all aspects of power plant structures and equipment, and track changes in performance over time. The use of drones for the inspection offers several advantages such as quick overview and evaluation of the power plant condition, monitoring of inaccessible areas, reduced plant downtime and safety of power plant personnel.
New drone technologies are being designed for faster and better inspection of chimney linings in power plants. Power plants use huge chimneys and boilers in their energy production work. They require periodic chimney and boiler inspections to ensure that there are no issues that might require maintenance. The efficient inspection of chimneys that reveal details of damages like corrosion areas and cracks in the concrete makes it easier to take immediate action, especially with visual data that can be used in the maintenance and repair work. It also reduces maintenance-related downtime and costs.
Drones are relevant for monitoring of power stations with flue gas desulphurisation (FGD) equipment. To internally inspect these power station FGD chimneys, drones with specific capabilities have been developed. The chimneys of these power stations are subject to harsh operating conditions and the internal linings of FGD chimneys are exposed to a continuous formation of acidic condensate that can attack the lining at temperatures of 50-80 ºCelsius. Lining failure due to insufficient material quality or faulty workmanship, or even localised damage can lead to immediate corrosion and, possibly, structural damage. During a unit outage, drones can be operated inside the chimney. They provide a comprehensive, high-resolution image of the internal lining system. Based on the data collected by the drone, the technicians can evaluate the lining and prepare a full report on its condition and any possible problems.
Other solutions
Efficient fuel combustion is essential for cost-effective power generation and emission reduction of power plants. Sufficient air is required to achieve complete coal combustion, while excessive air promotes NOX formation. Increasing the amount of air also lowers overall plant efficiency, as the increased volume of air flowing through the boiler leads to increased fan power consumption and greater heat losses. One of the solutions for maintaining the right air-fuel mix is monitoring the flue gas oxygen. The level of oxygen present in the combustion of waste gas is a key indicator of the amount of air supplied to the process. It can be monitored by using combustion gas oxygen analysers, which accurately measure the oxygen content in the combustion gas. Furthermore, these analysers can be used in conjunction with flow meters to regulate the amount of air supplied to the burner. Actuators can also be used to operate the plant at the optimum ratio of fuel, air and operating pressure. Improving the range and accuracy of the sensor information available from the boiler as well as using advanced control systems to maintain a balance between boiler variables and optimum input settings for any given situation is also useful.
To achieve optimum performance in a coal-fired power plant, careful monitoring of the quality of water and steam in the feedwater is essential. Multiple chemicals need to be monitored and controlled for optimum steam raising efficiency. Dissolved oxygen in the feedwater can cause pitting in the boiler, reducing its operating life. Dosing the feedwater with hydra – zine reduces oxygen to form nitrogen and water. However, excess hydrazine is wasteful and costly, whereas too little is unable to adequately control the dissolved oxygen levels. Further, pH analysers are used for monitoring feedwater acidity or alkalinity, as are conductivity analysers for measuring ionic content. By indicating the level of contamination, they can be used to decide the type and duration of treatment required.
Digital T&M instruments
The correct combination of T&M equipment plays a vital role in checking the health of the critical power plant equipment. At present, online inspection and troubleshooting procedures play a critical role for utilities in reducing cost and downtime, and improving efficiency. T&M instruments such as electrical flue gas analysers, thermal imagers, digital manifolds and digital gauges are being used for quick decision-making and troubleshooting. These instruments are user friendly and wireless as far as sensor and display are concerned. They are also IoT enabled, precise and accurate. Further, they offer online viewing of the process parameters, which is of tremendous use in effective monitoring of power plants.
To conclude, for enhancing the life of any power plant equipment, periodic checks are very important. Lapses in preventive and predictive maintenance can lead to unsafe conditions, resulting in revenue loss and system breakdown. To this end, comprehensive T&M solutions for the operation and maintenance of power plants will go a long way in providing real-time data so that utilities can repair or replace faulty units in time.
