Energy Recovery from Waste Paper and Deinking Sludge to Support the Demand of the Paper Industry: A Numerical Analysis

Abstract

The recovery of fibres from waste paper (WP) and deinking sludge (DIS) reduces the stress on nature compared to the collection of virgin pulp for paper production. Moreover, if not recycled, WP and DIS are mainly landfilled and incinerated, being thus responsible for the release of greenhouse gases (GHGs) into the atmosphere. In this context, energy recovery from WP and DIS would contribute to increasing energy independence and improving waste management in the pulp industry. From a broader perspective, it would increase renewable energy generation, supporting the paper industry in reducing fossil fuel consumption and GHGs emissions, in line with the goals of the European Union (EU) Green Deal 2021. For these reasons, in the present study, the combined heat and power generation potentiality of WP–DIS blends through gasification in combination with an internal combustion engine is numerically assessed for the first time. The air gasification process is simulated by applying a restricted chemical equilibrium approach to identify the optimum operating temperature (850 °C) and equivalence ratio (0.2). Electrical and thermal energy generation potentiality, considering WP and DIS production in the EU in 2019, is estimated to be in the ranges of 32,950–35,700 GWh and 52,190–56,100 GWh, respectively. Thus, it can support between 25 and 28% of the electrical and 44–48% of the thermal energy demand of the paper manufacturing sector, reducing the CO2 emission in the range of 24.8–28.9 Gt.

Comparison of Combustion and Gasification for Energy Recovery from Residual Woody Biomass

“…It decomposes wood residues into conventional (C, H2, N2, S, H2O, and O₂) and non-conventional (ash) components based on ultimate elemental analysis applied through an external Fortran subroutine in a calculator [12].…”

“…Several assumptions are taken into account to simulate CHP generation from residual wood through combustion and gasification [11,12,14]:…”

“…Tar formation neglect does not have any effect on energy potentiality and environmental impact analysis which are the main aim of the present study [20][21][22]. The reactions considered in the model development of combustion and gasification together with the heat of reaction (∆𝐻) [12] are presented in Table 2. Gasification reactions do not reach equilibrium at unique gasification temperatures as the kinetic constant of each reaction highly depends on temperature [23].…”

“…Consequently, syngas composition predicted through the developed model differs from the experimental campaign, reducing the accuracy of the model [11]. According to the available literature, the deviation between the simulation results and experimental outcomes should be lower than ± 20% to have a reliable model [11,12]. This condition can be ensured by assigning a specific temperature at each gasification reaction to restrict the equilibrium position, as expressed in the Eq.…”

“…Numerical analysis for the optimization of operating parameters involved in the cogeneration process from biomass with maximum process performances can save time and economic costs if compared to performing an experimental campaign [11,12]. For this reason, numerical modelling is commonly employed to predict the performance of systems aimed at energy recovery from biomass.…”