Better Combustion Airflow Monitoring at the Hunan Yiyang Power Plant

China has experienced tremendous growth in electricity demand over the past two decades. Coal-fired plant construction has exploded in the country to meet its seemingly insatiable appetite for electricity. Because most power plants in China use coal as fuel, it is imperative that new coal-fired plants be as clean and efficient as possible. This demand for cleaner plants has led to new and improved instrumentation now being used in new construction projects.

The Hunan Electric Power Design Institute designed a state-of-the-art coal-fired power plant in Yiyang City, Hunan Province called Hunan Yiyang Project Two, or Yiyang II, to meet the Chinese government's increasingly more stringent environmental control regulations (Figure 1). Yiyang I had been built on the same site about 10 years earlier. Overseeing the project was Beijing Desheng Power Engineering Consulting Co. and Hunan Province Thermal Power Construction Co., with project management handled from a field office set up in Yiyang City.

The Design Process
One notable advancement over the Yiyang I design came in the design of the combustion airflow path and the airflow measurement instrumentation. At Yiyang II, combustion air is routed through a series of preheaters. By using otherwise wasted heat to preheat the air used in the boiler, greater efficiencies were obtained. Additionally, all airflows are measured and balanced using advanced high-temperature immersible thermal mass flow technology, resulting in more precise combustion control and thus far lower emissions from the cleaner-burning coal.

In Yiyang II, combustion air to the boiler is supplied from one primary air fan, preheated, and then split into primary, secondary, and tertiary airflows. This design is illustrated in Figure 2.