Mass Flow Meters in Power Plants

The production of electricity in a natural gas power plant is a difficult process because of the numerous steps involved with the various kinds of fluids being used and optimized. The founder of Sierra Instruments, Dr. John Olin points out how vortex flow meters, thermal mass flow meters, and ultrasonic flow meters can enhance the flow energy management in power plant applications in this recent video from Sierra Instruments.

How a Power Plant Works

When most people think of power plants, they instantly visualize a picture of smokestacks and hot coals towering in the sky. But that is not the case. Most power plants in recent times are either in the process of switching to natural gas or burning natural gas.

To begin the process of producing electricity, power plants bring together fuel (coal or natural gas) and air, creating combustion. This creates an exothermic reaction and heat is released. The heat boils water in a boiler producing steam. This steam runs through a turbine, which causes the turbine to spin, thus generating electricity.

Best Flow Meter Technologies for Flow Energy Management in Power Plant Applications

There is liquid, gas, and steam that needs to be measured to enhance the efficiency of energy production and save costs on energy waste. Efficient energy production also helps power plants to minimize the CO₂ released into the atmosphere, which contributes to climate change in the form of greenhouse gases. The question becomes which flow meter technology measures each fluid the most effectively.

1. Inlet Air and Fuel (Natural Gas) for Combustion – Power plant managers must accurately measure the natural gas and air ratio for efficient combustion in the boilers. Too much natural gas is uneconomical and is a waste of money. Inadequate natural gas will not produce a flame that is hot enough to efficiently boil the water in the boilers. For combustion applications, thermal mass flow meters are optimal. This is because mass flow rate, not volumetric, is the quantity of direct interest whenever the molecules of the gas are the control variable in the process. Thermal mass flow meters are unaffected to changes in inlet temperature and pressure because these meters count the molecules of gas. These meters directly measure molecular flow (count gas molecules). Hence, they provide the most repeatable, reliable, and accurate gas measurement for power plant gas flow applications. With new developments in four-sensor thermal technology and software, some thermal flow meters have +/-0.5% accuracy which matches the accuracy of Coriolis meters at a fraction of the cost. In certain situations, vortex technology is also used as an alternative depending on the gas flow application.
2. Inlet Water to the Boiler – To account for efficient steam production and to detect any possible unnecessary leaks, power plant operators must also know how much water is entering into the boiler. The preferred method is clamp-on ultrasonic liquid flow meters to measure the inlet water flow to the boiler. The advantages of this technology are that it is non-invasive with no pipe cutting, it is immune to external noise, and it is fairly simple to install. New updates in ultrasonic technology now have on board apps and software that make the meter very easy to install, giving a “between goal posts” visual signal for an accurate installation. InnovaSonic^®207i is an example of an ultrasonic meter currently available on the market for performing this task.
3. Steam Production – To ascertain the efficiency of steam production from the boilers, which is critical to turn the turbine for energy production, power plant operators must get an accurate measurement of the steam flow. Vortex shedding flow meters are perfect for measuring superheated and saturated steam as well as liquids and gases. Insertion vortex flow meters are ideal for large steam pipes with an easy-to-use hot tap retractor. New technology and sensor advancement account for external vibration thereby making the vortex flow meters even more accurate. New on board software apps also permit easy set up, trouble shooting, tuning, datalogging, and in-situ calibration validation.

How to Integrate Thermal Mass Flow Meters, Vortex, and Ultrasonic Flow Meters into Power Plants

It is crucial that all of these flow meters are seamlessly integrated into the process of a power plant. Recently, Sierra’s complete family of Flow Energy Management flow meters, coined the Big-3 (Thermal, Vortex, Ultrasonic), has been released and is ideal for accomplishing the task of integrating vortex, thermal, and ultrasonic technology into power plants and other types of industrial flow processes. The advantage is that now power plant operators can work with just one company to specify, install, and maintain all their flow meters for all steam, gas, and liquid flow measurements. Sierra designs, manufactures, and calibrates all these flow meters at their headquarters in Monterey, California, USA, to guarantee lifetime support and the best quality.

The following are some of the other benefits of the Sierra Big-3:

• Best-in-class sensor technology that has been perfected over four decades
• On board software apps for easy set up, tuning, validation, gas mixing and datalogging
• Shared Raptor OS iSeries operating system for high quality flow rate calculation
• Commissioning and global support throughout the lifetime of the product
• Calibration expertise with high accuracy water loop and gas loop facilities

This information has been sourced, reviewed and adapted from materials provided by Sierra Instruments.

For more information on this source, please visit Sierra Instruments.