Chapter 4 4.1 Economic analysis A technical and economic analysis is proposed in this chapter, with the aim of an evaluation of the feasibility of the energy valorisation of the residues under investigation. The calculation procedure has been performed by means of using a tool developed by the IDM-Alto Adige (Innovation Development Marketing) for the project “Wood up” concerning the possibility of the char valorisation downstream of the gasification plants already existing in South Tyrol [32]. The tool implements all the benchmark data collected in the already existing plants in the region, thus the economic analysis have been performed considering the possibility of exploiting an existing configuration. Three technologies, using woodchip as input fuel, have been considered.
4.2 Calculation procedure adopted for the economic evaluation A common methodology has been applied in the case of all the residues in order to have an estimation of the input parameter needed by the employed tool (i.e. kgbiomass/kWhel). As first step, the actual average biomass flowrate in [kg/s] has been computed from the benchmark data of annual consumption of biomass (𝑇𝑜𝑡𝑎𝑙 𝑦𝑒𝑎𝑟𝑙𝑦 𝑏𝑖𝑜𝑚𝑎𝑠𝑠 [𝑡]) and yearly working hours ℎ𝑦𝑒𝑎𝑟 : 𝑚̇𝑏𝑖𝑜𝑚𝑎𝑠𝑠,𝑎𝑐𝑡𝑢𝑎𝑙 =
𝑇𝑜𝑡𝑎𝑙 𝑦𝑒𝑎𝑟𝑙𝑦 𝑏𝑖𝑜𝑚𝑎𝑠𝑠 1000 ℎ𝑦𝑒𝑎𝑟
3600
𝑘𝑔
[𝑠]
(4.1)
Imposing a cold gas efficiency CGEactual for a medium size plant equal to 0.8 and considering a low heating value of the woodchip 𝐿𝐻𝑉𝑎𝑐𝑡𝑢𝑎𝑙 of the actual plant equal to 16 MJ/kg, the input power for the benchmark case and the electric efficiency can be computed: 𝑃𝑖𝑛,𝑏𝑖𝑜𝑚𝑎𝑠𝑠,𝑎𝑐𝑡𝑢𝑎𝑙 = 𝑚̇𝑏𝑖𝑜𝑚𝑎𝑠𝑠,𝑎𝑐𝑡𝑢𝑎𝑙 𝐿𝐻𝑉𝑎𝑐𝑡𝑢𝑎𝑙 [𝑘𝑊] (4.2)
𝜂𝑒𝑙 = 𝑃
𝑃𝑒𝑙 𝑖𝑛,𝑏𝑖𝑜𝑚𝑎𝑠𝑠,𝑎𝑐𝑡𝑢𝑎𝑙
𝐶𝐺𝐸𝑎𝑐𝑡𝑢𝑎𝑙
(4.3)
The need syngas mass flowrate can be computed, assuming an heating value equal to 4.5 MJ/kg, as: 𝑚̇𝑠𝑦𝑛𝑔𝑎𝑠 = 𝐿𝐻𝑉
𝑃𝑒𝑙
𝑠𝑦𝑛𝑔𝑎𝑠 1000
𝑘𝑔
[ 𝑠 ] (4.4) 81
