Air-blown gasification of Solid Recovered Fuels (SRFs) in lab-scale bubbling fluidized-bed: Influence of the operating conditions and of the SRF composition

Abstract

This article investigates the gasification of Solid Recovered Fuels (SRFs). To better understand the influence of SRF composition on gasification efficiency and syngas quality, two industrial SRFs having different compositions were studied. A detailed SRF characterization was performed (elemental analysis; ash composition; LHV; fraction of biomass, non-biomass, and inert materials) to precisely describe the chemical complexity of such materials. The gasification tests were performed at pilot-scale in a bubbling fluidized bed using air as gasifying agent, and olivine as bed material. The separate contribution of gasification temperature (T=750-900°C) and equivalence ratio (ER=0.21-0.35) on the gasification efficiency was investigated by sequentially varying these two parameters. Gasification tests revealed that the LHV of the syngas and the cold gas efficiency decreased by 45-50% and by 20-30%, respectively, with rising equivalence ratio. These evolutions were attributed to syngas oxidation reactions which promoted the formation of CO2. Indeed, mass balances calculation revealed that the part of carbon atoms in syngas in the form of CO2 rises from 43 to 54% for SRF1, and from 35 to 50% for SRF2. High plastic content in SRF2 was responsible for the formation of stable light hydrocarbons (CH4, C2H4 and C6H6) from the decomposition of the plastic polymer chains, and to lower amount of H2 compared to syngas from biomass-rich SRF1. The carbon conversion decreased by 8% with rising ER from 0.21 to 0.30 for SRF2, as a result of plastics-biomass interactions promoting secondary reactions and leading to char formation. For both SRFs, rising temperature significantly improved the gasification efficiency whatever the SRF composition, and decreased the CO2 concentration. These evolutions were attributed to the promotion of several reactions, such as gasification, steam and dry reforming, Boudouard reaction, and Reverse Water-Gas Shift reaction.

Gasification of Low-Grade SRF in Air-Blown Fluidized Bed: Permanent and Inorganic Gases Characterization

“…Gasification efficiency was evaluated based on four indicators: cold gas efficiency (CGE), carbon conversion (CC), syngas lower heating value (LHVsyngas), and the syngas yield (ηsyngas). A previous article has presented the effect of gasification conditions on these 4 indicators for two SRFs (one rich in biomass and glass, and a second richer in plastics) [78]. The present article supplements this previous study with another SRF which exhibits an interesting composition between biomassrich SRF and plastic-rich SRF.…”

Distribution of Inorganics and Trace Elements during Waste Gasification in a Bench-Scale Fluidized Bed

“…Due to the lower presence of oxygen, the lower the ER, the higher the tar yield. Even though the use of in-bed dolomite is expected to lead to lower tar concentration due to its catalytic effect, ,, this effect was not observed here when using dolomite as bed material, as the tar yields measured when using dolomite (experiment 6) were similar to those measured for the similar ER, but using sand as bed material (experiments 1 and 3). More experiments should be conducted in order to evaluate the catalytic effect of dolomite on tar cracking.…”

“…The LHV of the product gas varies from 4.0 to 5.3 MJ/kg of dry gas. The results shown in Figure a show a tendency for a linear decrease in the LHV with ER, which is explained by the combustion of the light gas with oxygen and the dilution of the caused by the N 2 fed with the air. , The steam addition, filter temperature, and bed material did not impact the LHV or the gasification efficiency. The CGE varies from 64.4% to 71.0%, and in agreement with previous observations, the CGE decreases with ER. , The same tendency is observed for the HGE, which varied from 81.4% to 85.8%.…”

Experimental Study of Entrainment and Mixing of Renewable Active Particles in Fluidized Beds

“…There are plenty of literature studies that investigated the thermochemical conversion of renewable fuels [7][8][9][10][11][12][13][14][15]. However, only a few of them addressed their fluid dynamical context.…”