Biomass

Pagina 1

1 EXERCISE ON BIOMASS Solar and Biomass power generation – AA 2018/19 Prof. Giampaolo Manzolini – Ing. Marco Binotti Problem 1 Table 1 reports the dry-basis ultimate (elemental) analyses of ten unconventional fuels (seven types of biomass and three types of waste), and their values of lower heating value (LHV), moisture content and density. For each feedstock evaluate: 1. The dry ash free (“d.a.f.”) atomic composition (weight basis) 2. The higher heating value (assuming that the complete oxidation product of Chlorine is HCl), dry basis 3. The LHV and the HHV of the as received feedstock 4. the energy density (expressed as MJ/m3) 5. the mass flow rate of as received biomass re quired by a plant having 100 MW of thermal input (LHV basis) 6. the corresponding mass flow rate of moisture in the feedstock 7. the mass flow rate of stoichiometric air required by the combustion process 8. the product gas composition 9. the daily production of ash Assess the main disadvantages associated to the use of such feedstocks with respect to the use of a bituminous coal, such as Illinois #6 reported in Table 1. Take into account the following features: fuel availability and cost, transport, fuel storage, pollutant emissions, ash disposal. Problem 2 Consider a biomass-fired plant made of - a covered storage area - a wood chipper - a biomass boiler - an Organic Rankine Cycle generating electricity and heat (CHP). On the basis of the following data: - the feedstock, green oak (at the harvest conditions, as characterized in Table 1), is received as timbers (with an average diameter of 50 cm, average length of 2.5 m) in the covered storage area and arranged into log piles whose height is 5 meters and void fraction is 15%. - the average air condition of the storage area is 15 °C, 70% relative…