Abstract: The boiler furnace temperature field is determined by coal combustion, working medium heat absorption, NO_x generation, as well as fouling and slagging, etc. It tends to be damaged by some uncertain factors, which will eventually affect the safe and stable operation of boilers. Therefore, the combustion adjustment experiment is performed at the load level of 300 MW, 270 MW and 240 MW respectively on Unit 2 of a power plant, and the real-time temperature data are collected by the acoustic temperature measurement system. Then, the processed data results are superimposed onto the original signals in the form of bias signals. By controlling the secondary air door opening size, the balance of temperature field and NO_x emission concentration are optimized in closed-loop control. The experiment results show that the temperature field balance has been improved and the NO_x emission concentration is also reduced effectively. Through this study the issue of lacking flexibility in manual adjustment based on operators’ experience is resolved. The intelligent level of the boiler control is also improved, which is very helpful for combustion optimization.

Key words: acoustic temperature measurement, DCS, closed-loop control, temperature field, secondary air, NOx emissions