ABSTRACT
Cultivation of the hazel and almond is widespread in Italy, especially in those small and medium enterprises that work in the confectionery industry. Particularly at the national level, the major producer regions are: Campania (40%), Lazio (33%), Piedmont (14%), Sicilia (10%) [1]. Almonds are instead produced in Sicily (72%), Apulia (25%), and Campania (2%) [1]. Due to the abundance in Italy (156.000 hectares [2]) of these wastes, this work will evaluate how different mixes could be exploited in small scale fluidized bed gasifier, rather than combustion in boilers and anaerobic digestion [3]. The biomass used is a mix composed of 50% of hazelnut shells and 50% of almond shells, each shell is taken from three different samples per each region. The Directive 2009/28/CEimplemented in Italy in 2010-set ambitious targets in order to ensure a clean and sustainable future. Its aim is to reduce greenhouses gases emissions by 20%, to produce 20% of energy from renewable sources and to decrease the consumption by 20% improving the energy efficiency. These goals must be reached by 2020. The above-mentioned regulation led the public administrations and private stakeholders to investigate new technologies which may face the growing energy demands by the use
biomass wastes. The disposal of these wastes is generally a problem for the industry. As indicated by the Legislative Decree 152/2006 residues from agricultural activities are classified as waste and therefore is within the scope of application of Part IV of the “Decreto Ambiente”. Article. 13 of Legislative Decree 205/2010 Italian (amendments to art. 185 of Legislative Decree 152/2006) states that “straw, pruning, mowing and other agricultural or forestry material” are not considered waste when used in agriculture, in forestry or for the production of energy. Thereby excluding the combustion of crop residues without energy production, this activity is configured as waste disposal of agricultural waste and must be submitted to the Italian Environmental Code. The energy use of these biomass residues could therefore involve both environmental and social benefits by promoting a new sector and the development of highly efficient energy conversion devices, with particular regard to emissions into the atmosphere [9]. The gasification process is a thermochemical process that allows the conversion of a solid fuel, biomass, in a gaseous fuel (syngas) usable in ICE and mTG [10]. Among the energy conversion processes of biomass, the used in this work is the fluidized bed gasification, with steam and catalytic cracking of the syngas. This type of gasification is preferable than others because the continuous mixing created within the reactor, brings to a uniform temperature in the bed, a production of syngas with a higher calorific value and because the use of olivine as hot sand, also a primary cracking of the TAR [11]. In the process of gasification biomass is thermally decomposed into syngas with the production of other compounds: char, ash and tar (Topic Atmospheric Residue, TAR) [12]. In this work two different types of residual agricultural biomass were considered, in particular almond and hazelnut shells. The biomass that will be introduced into gasifier is composed of 50% of hazelnut shells and 50% of almond shells. The samples, hazelnuts and almonds, were taken from three Italian regions. The samples were characterized and then used to perform gasification tests in order to verify the composition of the raw gas (in term of H2, CO, CO2, CH4 and TAR) and to assess two techniques in series capable to ensure satisfactory TAR removal efficiencies for the use of the gas in cogeneration systems:
– Catalytic cracking/steam reforming in a secondary reactor at 800 °C
– Vegetable sunflower oil as scrubber for absorption tar.
