Chemical composition of agromass ash and its influence on ash melting characteristics
¹Lithuanian Energy Institute, Laboratory of Heat–Equipment Research and Testing, Breslaujos str. 3, LT–44403 Kaunas, Lithuania
²Lithuanian Energy Institute, Center for Hydrogen Energy Technologies, Breslaujos str. 3, LT–44403 Kaunas, Lithuania
The increasing demand for biofuels leads to a growing need for agromass, such as herbaceous plants and agricultural waste. However, agromass contains high quanitites of alkali metals, mainly potassium and sodium, which limits agromass usage in thermoconversion processes. Alkali metals react with other ash forming elements which leads to ash related problems such as agglomeration, fouling and slagging during agromass burning. In this study, chemical composition and melting behaviour of ashes formed at 550 °C are investigated. Three herbaceous plants (reed canary grass, hemp, orchard grass), four types of agricultural waste (straws of rye, wheat, buckwheat and canola) and two types of woody biomass (birch, spruce) are selected. Ash melting behaviour, composition and bulk structure are determined using a high temperature furnace with a video camera, inductively coupled plasma atomic emission–spectrometry and X–ray diffraction technique, respectively. Ash melting behaviour of selected agromass types shows that the hemp ash has the highest shrinkage starting temperature which reaches 1,079 °C. This is due to the high content of calcium and low content of potassium and sodium in hemp ash. Three main components calcium carbonate, potassium sulfate and potassium chloride have been identified in ashes after agromass and woody biomass are heat–treated at temperature of 550 °C.