Properties of biofuel fly ash and capabilities of its use for agricultural needs

M. Kulokas¹*, V. Zaleskas¹, N. Pedišius¹, M. Praspaliauskas¹ and K. Buinevičius²

¹Lithuanian Energy Institute, Laboratory of Heat–Equipment Research and Testing, Breslaujos st. 3, LT-44403 Kaunas, Lithuania
²UAB ‘Enerstena’ Centre of Research and Development, Ateities pl. 30A, LT-52163 Kaunas, Lithuania
*Correspondence: kulokas@lei.lt

Abstract:

The use of various types of biomass for energy production provides great prospects for reducing the consumption of fossil fuels and the negative impact on the environment. However, the use of biomass, in particular agromass for this purpose, results in relatively large amounts of bottom ashes and fly ashes, the composition and properties of which also raise a number of additional environmental problems. The composition and properties of fly ash are investigated in the paper, taking into account the possibilities of utilizing them for soil fertilization and other applications. Fly ash samples were collected from bunkers of flue gas cleaning equipment (electrostatic precipitator and cyclones) installed after water heating boilers, which are firing wood chips and chuffed straw. The composition of fly ash was determined using Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) and Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM/EDS) while particle size distribution was obtained using scattered-light aerosol spectrometer. Electrical Low Pressure Impactor (ELPI) was used to separate fly ash into 14 groups by particle diameter, and the analysis of their composition showed differences in the composition of the fly ash collected in cyclones and Electrostatic Precipitators (ESP). An analysis of the composition of samples in regard to the existing heavy metals norms and considering concentrations of elements beneficial to the growth of plants, enables to prepare recommendations for fertilization. The determined alkalinity of fly ash pH 13 confirms the possibility of their use for reducing soil acidity. The analysis of fly ash composition has shown that they contain elements, important for plant growth (Ca, Mg, K, P, N, S), and their concentrations determine the further use for soil quality improvement because the amount of these elements in the acid soils is reduced.

Key words:

agromass, biofuel, chemical and physical properties, fly ash

Chemical composition of agromass ash and its influence on ash melting characteristics

D. Čepauskienė¹, N. Pedišius¹ and D. Milčius²

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
*Correspondence: Deimante.Cepauskiene@lei.lt

Abstract:

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.

Key words: