Characterization of Selected Nigerian Biomass for Combustion and Pyrolysis Applications

Abstract

Biomass is the most utilised form of renewable energy, especially in developing nations, and is a possible replacement for fossil fuel in power generation. The most commonly used method for recovering energy from biomass is combustion. Many countries are exploring the utilisation of energy crops and indigenous residues to deliver sustainable sources of biomass. For these bioresources, detailed characterisation of the fuel properties is essential in order to optimise the combustion processes. In this study, some potential energy crops and woods from Nigeria, namely Terminalia superba, Gmelina arborea, Lophira alata, Nauclea diderrichii, and also one 2 abundant agricultural residue, palm kernel expellers (PKE) were characterised for their combustion properties. Standard characterisation methods such as proximate and ultimate analyses, metals analysis, and ash fusion test were used for this purpose and the results were compared to some UK biomass. In addition, their thermal conversion was assessed by thermogravimetric analysis and pyrolysis-gas chromatographyÐmass spectrometry. Finally, combustion studies were conducted by suspending single biomass particles in a methane flame to obtain information on reactivities and combustion characteristics. Results indicate that the ash fractions in the Nigerian woods were low in K, Si, and Ca, resulting in low calculated alkali indices, hence these fuels are not predicted to cause severe fouling problems. Furthermore, the analysis of the evolved product during devolatilisation from Py-GC-MS suggests that the content of oil is high in Gmelina. Finally, the results from the single particle combustion experiments revealed longer char burn out rate for Lophira and Nauclea when compared with those of Terminalia and Gmelina.Keywords: biomass, torrefaction, energy, combustion, pyrolysis. Nigeria has large reserves of gas and solid minerals, and the largest oil reserves in Africa.Consequently the country has a very high dependence on crude oil, which contributes seedling nurseries, and plantation management [7]. Woods in the plantations include Gmelina, Terminalia, teak, eucalyptus, and pine. Tropical rain forest is the major source of timber supply and energy crops in Nigeria with high plant diversity of over 4,600 plant species. The forest covers 10% of the countryÕs land area with over 560 tree species at a range of about 30 to 70 species per hectare for trees ≥ 5 cm diameter at breast height (dbh) [8].Terminalia superba is a tree found in the tropical lowland forest in Nigeria. The tree is planted around April at the beginning of the rainy season, and thrives on rich, well-drained alluvial soils, although it can also be cultivated on other soil types namely lateritic sands, gravel and clays, lava, black basaltic clays and crystalline soils. The wood air dries rapidly, degrades slightly and is lightweight to medium-weight, with a density ranging from 370Ð730 kg/m³ at a moisture content of about 12% [9]. Once the wood is dried, it becomes stable. The chemical composition

March 2017

“…This is usually the norm with most tropical rainforests worldwide, they have the most diversified plants species of the different forest types (SCBD, 2010). This agrees with Akinrinola et al (2014) and the report of (USAID, 2008). It also confirms the findings of Onyekwelu et al (2006) that Nigeria's rainforests have a high plant diversity with over 560 tree species, at a range of about 30 to 70 species per hectare.…”

The potential use of torrefied Nigerian biomass for combustion applications

“…At present the amount of biomass used for large scale electricity generation is limited, but many studies have been made into the use of solid biomass fuels alone or cofired with coal, for example [6][7][8]. Here we study four woods and an agricultural residue, Palm Kernel Expeller (PKE) all of which are widely available in Africa and Asia [3,4,9,10], Only a few studies have specifically considered the properties and use of torrefied Nigerian woody biomass [9,10].…”

Combustion characteristics of coal gangue and biomass under an O2/CO2 atmosphere

“…Biomass has the characteristics of large output, wide distribution, and strong recyclability. Biomass, which mainly includes byproducts of agricultural and forestry production processes, possesses a low ash content and a high volatile content [7][8][9]. Biomass combustion and photosynthesis are reversible processes of carbon transport, and almost no CO 2 emissions occur in the whole process.…”