Prevention of Particulate Emissions
AUTHOR: Zhangfa Wu
DATE: December 2000
This report examines the upstream factors affecting particulate emissions from pulverised coal fired power plants. It identifies the opportunitiesi for prevention of the emissions before the particulate control system. Coal quality affects the fly ash and flue gas properties which control the performance of particulate control units. Coal cleaning reduces particulate emissions. Care must be taken as coal cleaning decreases the sulphur content which may increase the fly ash resistivity. Switching to low sulphur coals or low heating value coals decreases the ESP efficiency.
Coal blending can either improve or impair the ESP performance, depending on the coals being blended. Dry bottom boilers produce much higher particulate laods to ERSPs or fabric filters than wet bottom boilers. Most combustion modifications increase unburned carbon in the fly ash, lowering the ESP efficiency. The impact can be mitigated by firing high reactivity or high volatile coals, reducing the size of coal particles, and optmising combustion. Flue gas conditioning improves the ESP performance by modifying the fly ash characteristics. It is an effective way to upgrade ESP's when switching to low-sulphur coals or meeting more stringent emission legislation.