Solar-hybrid Thermochemical Gasification of Wood Particles and Solid Recovered Fuel in a Continuously-Fed Prototype Reactor

Abstract

Solar thermochemical gasification is a promising solution for the clean production of low-emission synthetic fuels. It offers the possibility to upgrade various biomasses and waste feedstocks and further provides an efficient way to sustainably store solar energy into high-value and energy-intensive chemical fuels. In this work, a novel continuously-fed solar steam gasifier was studied using beechwood and solid recovered fuels (SRF) particles. Solar-only and hybrid solar/autothermal gasification experiments were performed at high temperatures to assess the performance of the reactor and its flexibility in converting various types of feedstocks. The hybrid operation was considered to increase the solar reactor temperature when the solar power input is not sufficient thanks to partial feedstock oxy-combustion. The hybrid solar process is thus a sustainable alternative option outperforming the conventional gasification processes for syngas production. Wood and waste particles solar conversion was successfully achieved, yielding high-quality syngas and suitable reactor performance, with Cold Gas Efficiencies (CGE) up to 1.04 and 1.13 respectively during the allothermal operation. The hybrid process allowed operating with a lower solar power input, but the H2 and CO yields noticeably declined. SRF gasification experiments suffered furthermore from ash melting/agglomeration issues and injection instabilities that undermined the continuity of the process. This study demonstrated the solar reactor flexibility in converting both biomass and waste feedstocks into syngas performed in continuous feeding operation. The experimental outcomes showed the feasibility of operating the reactor in both allothermal (solar-only) and hybrid allothermal/autothermal (combined solar and oxy-combustion heating) for continuous syngas production with high yields and energy conversion efficiencies.

Experimental assessment of woody biomass gasification in a hybridized solar powered reactor featuring direct and indirect heating modes

“…It measures how well the biomass is converted into syngas and quantifies the improvement (if higher than 1) of the calorific value between the initial feedstock and the produced fuel. Finally, the solar-tofuel energy conversion efficiency was calculated, as defined in Equation 8 [25]. Unlike CGE, it includes at denominator the total solar energy absorbed by the gasifier during the biomass injection periods.…”

“…However, in order to overcome the variability of solar resource, reactor hybridization has been recently investigated to ensure both allothermal (solar only) and hybrid allothermal-autothermal (combustion-aided) gasification. Boujjat et al [25] experimentally studied beech wood gasification by steam at temperatures in the range 1200-1300°C (Equation 1). Injection of oxygen and additional biomass aimed to initiate combustion (Equation 2), in order to compensate for solar power input daily variations.…”

Valorization of agricultural wastes for biofuel applications

“… NA High product yield Generation of chemicals and minerals as by products Catalysts deactivation Appropriate catalyst to be developed ( Arregi et al., 2016 ) Solar gasification A thermochemical conversation of biomass into syngas by using solar energy as heat source to stimulate the reactions. NA Good H 2 yield Improved conversion efficiency at low temperature Pulverization of feedstock not necessary Minimum CO 2 generation Expensive solar collector Cost reduction measures needed ( Boujjat et al., 2020 ) Supercritical conversion Thermochemical production of hydrogen from supercritical water as gasifying agent. High H 2 content No need to dry feedstock High conversion efficiency Production of other clean gaseous fuels Difficulty in selecting supercritical medium Simple and easy process Multiple products ( Tushar et al., 2020 ) NA = Not Applicable; COD = Chemical Oxygen Demand; H 2 = Hydrogen; CH 3 = Methane; CO 2 = Carbon dioxide.…”

Design and validation of reactant feeding control strategies for the solar-autothermal hybrid gasification of woody biomass

“…Three main thermochemical performance indicators were determined [21]. The carbon-conversion efficiency (CCE, Equation 9) quantifies the fraction of carbon atoms (contained in wood feedstock) converted into syngas components (mainly CO, CO 2 , and CH 4 ).…”

“…It was however noticed that increasing the H 2 :CO mole ratio from 1.0 to 1.7 required a water flow rate nine times higher than the stoichiometric one [16], thus questioning the actual feasibility of such control. Boujjat et al also investigated SAHG both experimentally [19] and numerically [20], using a hybridized spouted-bed reactor and eventually proposing an application to solid-recovered fuel gasification [21]. Recent experimental investigations of the hybridized spouted-bed revealed the impact of O 2 injection rate, operating temperature (in the range 1200-1300 °C) and reactor heating mode (direct versus indirect heating of the cavity) [22].…”