Coal fired power plants

Non-invasive flow measurement on boiler feed water flows

Coal fired power plants belong to the most common power plants in the world. By burning coal, feed water is heated up into steam for subsequent electricity generation. Measuring the feed water flows to the boiler is of crucial importance for continuous process optimization and to avoid premature failure of the tubes.

A North American coal power plant with more than 200MW capacity approached FLEXIM as of continuing problems with failing boiler feed water tubes – a problem which seemed to be only present at full load situations. Together, the plant operator and FLEXIM, decided to establish a number of flow measurement points on 14” carbon steel pipes with downward vertical flows at 320 °C / 600 °F and 170 bar / 2450 psi, by making use of FLEXIM’s WaveInjector mounting fixture, which allows the flow measurement at such extreme pipe wall temperatures.

The measurement points were located at the discharge of three circulating water pumps. The initial testing showed high aeration levels during normal operation and by using the diagnostics of the FLUXUS ultrasonic clamp-on flow meter, it was determined that steam from the steam drum was being entrained into the boiler feed water – a cause for premature tube failure.

Thus, it was decided to increase the water drum level and subsequently forced outages due to boiler tube failure could be decreased. Further, the steam entrainment was causing poor heat transfer in the boiler. With decreased steam entrainment levels, the plant can now operate at peak conditions while accurately monitoring boiler feed water flows and ensuring evenly distributed flows.

Advantages:

  • Measurement of extremely hot (up to 400 °C / 750 °F and beyond) and pressurized feed water with FLEXIM’s WaveInjector solution
  • No cutting or welding into the pipe, no pressure losses - completely non-intrusive
  • Free of wear and tear, unaffected by entrained gaseous bubbles or solids
  • Highly accurate and reliable due to carefully matched and paired transducers and elaborate digital signal processing
  • Sophisticated diagnostic tools for further process optimization
  • No pressure losses inside the pipe