ASH MELTING TEMPERATURE PREDICTION FROM CHEMICAL COMPOSITION OF BIOMASS ASH

Solid fuels, including biomass, consist of combustible, ash and water. Ash in fuel is result of reaction of minerals presented in the biomass. Minerals and other different substances which form ash got into biomass during growth. Ash is solid residue resulted from the perfect laboratory combustion of fuel. It is composed of minerals that are present in the fuel. Some species of biomass ash have low ash melting temperature and can cause various problems in combustion boilers. Ash slags and sinters can avoid heat transfer in heat exchangers, which can cause corrosion of heat transfer surfaces.Ash melting temperature can be determined on the basis of standard STN ISO 540 in some laboratory. Meltability of ash is characterized by the physical state of the ash, which occurs during the heating process under well-defined conditions in furnace. There exist 4 types of ash melting temperature - Shrinkage temperature (ST), Deformation temperature (DT), Hemisphere temperature (HT) and Flow temperature (FT). Experimental determination of ash melting temperature is quite expensive. In paper is described method of prediction ash melting temperature from known chemical composition of biomass ash. There is proposed mathematic model for determination of all ash melting temperatures. There is need to know the proportion of SiO2, CaO, K2O, MgO and Al2O3 in biomass ash. The mathematical model is relatively accurate with real ash melting temperatures and reaches accuracy about 90 % compared with ash melting temperatures obtained by STN ISO 540 method