Hiroaki Kanemoto

An adaptive State estimator for pulverizer control using moments of particle size distribution

An adaptive state estimator for pulverizers consisting of blending, grinding, and classifying processes has been developed in order to improve control of pulverized-coal-fired power stations. Though coal flow and non-Gaussian particle size distributions in the processes are mutually related, the estimator is able to efficiently simulate flow and normalized moments of the distributions with a state vector. The estimator also identifies coal grindability for adapting to variation in coal characteristic in parallel with the process simulation. The accuracy of the adaptive estimation and the effectiveness in improving the load-swinging performance have been validated at a 1000-MWe class power station.

A Demonstration Study on a High Performance Vertical Roller Mill for a Pulverized Coal Firing Boiler

We have developed new technologies to improve particle classification performance of vertical roller mills using a rotary nozzle ring with reverse swirling flow and a louver separator. A rotary nozzle and a louver are installed in primary and secondary classification sections of the mill, respectively. A series of tests using a pilot scale mill showed that these technologies reduce the fraction of coarse particles, power consumption of the mill and mill differential pressure. For an industrial scale-up, we conducted a demonstration test using a vertical roller mill equipped in a 700MW thermal power plant consisting of a pulverized coal firing boiler and six mills with approx. 70t/h nominal grinding capacity in each. In this paper, we discuss demonstration test results on the viewpoint of decreasing coarse particle fractions, power consumption and mill differential pressure. Under normal operating conditions, the coarse particle fraction in pulverized coal was reduced more than 50%, power consumption was reduced 7% and differential pressure was reduced approx. 50%. Additionally, power consumption was reduced approx. 15% under high coal feed conditions. We confirmed that these new technologies effectively improved performance in higher mill loading rates. These results provide a prospect of upgrading the plant performance, especially in reducing unburned carbon in fly ash and power consumption of auxiliary equipment.Copyright