Improving Level Control in Combined-Cycle and Coal-Fired Power Plants

by | Jun 1, 2018 | Industry, Level, Measurement Instrumentation, Power Generation

Jim Cahill

Chief Blogger, Editor

Emerson's Matthew Brummer


Levels of intermittent, renewable sources of energy for the electrical grids around the globe continue to grow. Power plants designed for more consistent, base load operation are under greater stress.

In this recorded Power magazine webcast, Optimizing Level Control for Maximum Reliability and Efficiency in Combined Cycle and Coal Plants, Emerson’s Matthew Brummer joins moderator and Power magazine executive editor, Aaron Larson.

Here’s the overview of this 42-minute webcast:

The operational realities of power generating units today are vastly different than they were year’s ago. Most units were designed for baseload operation, whereas today they’re being cycled to account for an increased renewable portfolio and low natural gas prices.

We’re seeing more equipment failures because of these operating profiles. In year’s past, plants were well staffed, which made it easy to maintain operations. Today, however, staff and expertise are depleted and maintaining plant assets is much more challenging. Having a plan to lead your utility into the future will be more critical than ever to stay up and running. A key component in planning needs to be choosing the right technology for boiler drum and feedwater heater levels.

Matthew gives answers to these considerations, practices and questions facing power producers:

  • Eliminate measurement uncertainty during start-up and shut-down as water evaporates and condenses from wet legs
  • How to provide greater stability during periods where there is significant load fluctuation
  • Eliminate the risk of wet legs freezing and causing an unplanned outage
  • Reducing the frequency of blowdowns
  • What are minimum code requirements? What would be optimal?
  • How does guided wave radar provide more consistent drum level control for combined cycle plants?
  • How does feedwater heater monitoring minimize heat rate in coal-fired plants?

He opens his part of the presentation by describing some of the challenges that power producers face. These producers want to better understand how technology can help with quicker response to changing electrical load requirements, how to minimize forced outages and how to improve overall efficiency in converting fuel sources into electrical energy.

The thermal stress caused by load cycling of coal-fired and combined-cycle plants increases operating & maintenance costs according to a National Renewable Energy Laboratory (NREL) study, Power Plant Cycling Costs.

For North American power producers, the aging workforce is another challenge. The US Bureau of Labor Statistics estimates that around half the work force in the electric utility sector will retire over the next decade. They are finding difficulty filling open positions due to a shortage of talent and experience.

Matthew focuses his presentation around boiler drums—feedwater, deaerators, and the high-temperature heaters. Level measurement plays an important role in these applications, and he noted that no one technology is best suited for every level measurement.

Power Plant Boiler & Heater Level Measurement Technologies

Level measurement specialists like Matthew ask many questions when helping power producers select the right level measurement technology for the application. Questions such as, “Is it foaming, is it turbulent, etc.” He also describes applicable codes such as ASME PG.60.1.1 for the Permissible Design for Visual Level Gages.

Differential pressure (DP) level measurement or displacers in older plants are the most common instruments used for measuring boiler liquid level. Common reliability concerns include plugging issues, freezing, and unreliable readings at non-normal operating conditions. Blowdown procedures are typically performed on the DP Level impulse lines. Operators may not get readings until the wet leg on the low side of the DP transmitter refills with liquid. These tubing lines may also leak over time.

Changes in load and dynamic conditions such as shutdown and startup can cause transmitter inaccuracies caused by low pressure side losses in water, condensation, or specific gravity changes.

To address these challenges, Matthew described how Guided Wave Radar technology is being used with multiple radars in two-out-of-three (2oo3) voting schemes used for safe, accurate, and efficient boiler operation.

Watch the full presentation for more recommendations and best practices on how to increase the safety, reliability and efficiency of your power plant operations as it pertains to the level measurements around the critical assets.

Learn more about ways to improve Power Plant Availability on Emerson.com. You can also connect with a Power Industry expert to discuss ways to improve your power plant’s performance.

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The opinions expressed here are the personal opinions of the authors. Content published here is not read or approved by Emerson before it is posted and does not necessarily represent the views and opinions of Emerson.