Novel Application of Pretreatment and Diagnostic Method Using Dynamic Pressure Fluctuations to Resolve and Detect Issues Related to Biogenic Residue Ash in Chemical Looping Gasification

Andrea Di Giuliano,Javier Gil,Katia Gallucci,Raúl Pérez-Vega,Ibai Funcia

doi:10.3390/pr8091137

Andrea Di Giuliano, Javier Gil + Show 3 more

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https://doi.org/10.3390/pr8091137

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Abstract

Biogenic residues are a promising feedstock to produce liquid biofuels via chemical looping gasification (CLG), but they form ashes with a high inorganic matter content, thus causing agglomeration and deposition in CLG-fluidized beds made of oxygen carriers (OC). The aim of this work is to develop pretreatments for residual biomasses to prevent this issue. Raw forest pine (as a reference material) and wheat straw residues were considered. The latter were pretreated by torrefaction at 250, 260, or 270 °C and through the washing of torrefied biomasses. Torrefaction encouraged a de-chlorinating effect, while washing allowed the removal of 30–40% of S, 60–70% of K, and 40–50% of P. The analysis of pressure fluctuation signals (standard deviations and dominant frequencies) was utilized to verify the improvement of the performance of treated biomass in fluidized beds: three OCs were, respectively, coupled with ashes from all biomasses, then fluidized from 700 to 1000 °C at two and three times the minimum fluidization velocity. The diagnostic method used to analyze pressure fluctuations was shown to be effective for detecting the incipient fading of bubbling fluidization. This phenomenon was related to the agglomeration or the severe fragmentation of OC particles mixed with ashes, thanks to scanning electron microscopy and particle-size measurements. These characterizations and pressure fluctuations analyses confirmed the general improvement of wheat straw performances after pretreatments.

Highlights

The maximum target of a temperature increase of 2 ◦ C above preindustrial levels, proposed by theParis Agreement [1], is becoming an increasingly urgent issue in the current global scenario [2], requiring the reduction to zero of greenhouse gas (GHG) emissions by the end of this century [1,3]
The aim of this study is to apply the analysis of instantaneous pressure fluctuations, both in the frequency and time domains, as a tool to detect de-fluidization phenomena in bubbling fluidized beds made of materials to be used in the chemical looping gasification (CLG) of biogenic residues
Two biogenic residues were selected for this work, because of their availability and potential for use in Europe and worldwide: wheat straw and raw pine forest residues, both coming from Navarra in the North of Spain

Summary

Introduction

The maximum target of a temperature increase of 2 ◦ C above preindustrial levels, proposed by theParis Agreement [1], is becoming an increasingly urgent issue in the current global scenario [2], requiring the reduction to zero of greenhouse gas (GHG) emissions by the end of this century [1,3]. Processes 2020, 8, 1137 been denoted as bio-energy with carbon capture and storage (BECCS) [5] This allows negative CO2 emissions to be achieved, with an estimated contribution ranging between 2.2 and 12 Gt CO2 of all CO2 sequestrated by CCS (i.e., 4–15 Gt) at the half-way point of the century [6]. Chemical looping technologies are among the most promising BECCS options, since they are considered to bring about the lowest energy and cost penalty for CO2 capture [7] Among these techniques, the chemical looping gasification (CLG) of biomass has currently aroused great interest in terms of obtaining environmentally friendly liquid biofuels and H2 [8,9]

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