Fuel conditioning and combustion in hard coal and lignite-fired power plants

For efficient and clean combustion, coal from the different sources needs to be mixed to even out variations in size, moisture content and chemical composition. The processing steps in the coal preparation area might involve dewatering, sorting, crushing, screening etc. in order to keep the coal within a required quality range. Measurement of bulk materials is difficult; uneven surfaces, different moisture levels and high levels of dust are some of the challenges. Previously, the level measurement technologies used nucleonic sources or maintenance intense mechanical level meters.

KROHNE pioneered radar level measurement technology and offers a broad range of sophisticated FMCW and TDR technologies, both for liquids and all kinds of solids level measurement. The OPTIWAVE-series of FMCW radar level meters operate from 6 to 80GHz. For dusty environments the patented drop antenna of the OPTIWAVE 6400 avoids dust build-up in metallic horns and drastically improves availability. For coal storage and preparation OPTIWAVE 6400 is used within the entire handling chain from the coal storage and mixing, on the conveyor belts and in the coal bunkers, replacing the nucleonic technology.

The majority of coal power plants are fired by pulverized coal burners. The flow of coal to the pulverizer is controlled by the coal feeder. The pulverizer crushes, dries and then classifies the coal according to particle size: hot air dries and transports the coal to the burners. The burners need to be ignited by a low volatile fuel, such as gas or oil, until they are stable. The whole start-up and ignition process is controlled by the burner management system.

The OPTISONIC 7300 ultrasonic gas flowmeter measures these natural gas flows. These provide an immediate response and with no moving parts are maintenance free. The high turndown ratio makes the flowmeter suitable for low load and highly flexible operation, where . tolerating frequent flow starts/stops, which was not the case with older flow technologies. For oil burners, the OPTISONIC 3400 ultrasonic flowmeter has a full bore measuring tube and no moving parts. The typical heavy fuel oils used, which may contain ash or solids, used to cause wear and damage to the original mechanical flowmeters used here: the OPTISONIC is unaffected by such entrained solids.