Energy densification is the overall objective of the on-going bioliq project. Bioslurry, obtained via fast pyrolysis of low-grade biogenic resources, is converted into high quality syngas in a high pressure entrained flow gasifier. The modeling of this three-phase system involving high pressure and high temperature sub-processes is very challenging. The detailed representation of the chemical sub-processes goes along with an increase of the computational cost. In this work, a novel approach is developed to achieve fast and accurate Computational Fluid Dynamics (CFD) simulations of the gasification of a slurry fuel in a laboratory entrained flow gasifier under atmospheric pressure. The method investigated relies on a sectional approach to describe the char gasification. An Euler-Euler approach is used for the modeling of the slurry/gas phase system. Ethylene glycol is used to represent the liquid part of the slurry. Experimental

The steel industry currently faces significant challenges. These are enormous environmental impacts, material usage, energy consumption, and byproducts of the processes. [1] In 2020, the total crude steel production was 1869 million tons (Mt). [2] The conventional blast furnace-basic oxygen furnace (BF-BOF) route produces 70% of the global crude steel, [3] utilizing coke to produce iron by reducing iron ore, which emits high amounts of CO 2 in the environment. Steel production contributed 6.7% of the global anthropogenic emissions of CO 2 in 2020, and the average emission is estimated to be 1.8 t CO 2 / per t steel. [4] This corresponds to %3.46 Gt CO 2 per year, eventually leading to even higher annual emissions in 2050 due to the growing steel demand. Given this high level of CO 2 emissions, steel production cannot rely on continuous process optimization but instead, needs fundamental technological changes to meet future emission limitations.Under these circumstances, the direct reduction (DR) process of iron oxide is a promising technology to reduce the CO 2 emissions where hematite (Fe 2 O 3 ) is reduced by syngas (H 2 /CO-mixture) or even with pure hydrogen (H 2 ). Many mathematical models have been proposed in the literature to predict the gaseous reduction behavior of iron oxide. However, due to a large number of influencing factors in the direct reduction process, for example, gas composition, operating pressure, temperature, or solid material characteristics (porosity, tortuosity, grain size, gangue contents, mineralogy, etc.), uncertainty is relatively high. Researchers usually try to balance between model simplicity and accuracy (agreement with experimental data). To avoid the inherent complexity of the direct reduction process, McKewan [5] developed a simple one-interface shrinking core model by considering the interface chemical reaction as the rate-limiting step. They concluded while validating against their data that diffusion and chemical reaction should be considered simultaneously. Tsay et al. [6] developed a model based on a three-interface shrinking core model for H 2 /CO mixtures, considering the same diffusivities and mass transfers for reactants and products. However, this approach has the evident weakness of assuming a distinct sharp interface between different solid oxides. A transient isothermal model based on the grain model has been proposed by Valipour et al. [7] to simulate a porous hematite pellet's thermal and kinetic behavior in a syngas environment. They showed how models not considering the film resistances deviate systematically from the experimental data.Aside from the fundamental mathematical approach, the chemical kinetics of reduction of iron oxide with H 2 /CO mixtures has not been adequately investigated, especially the carbon deposition phenomena. Turkdogan et al. [8] studied the kinetics of direct reduction process of iron oxide using hydrogen. They found out that the transformation process of hematite to iron is mediated by magnetite (Fe 3 O 4 ) and wüstite (Fe (1Ày) O).

The direct reduction of iron ore pellets with syngas or hydrogen is a promising technology to reduce the CO2 emissions of the iron and steel industry. The conversion rate of single iron ore pellets to iron is extensively investigated. In most of these studies, a shrinking core model is employed to reproduce the experimental observations. However, this model presents an inherent bias by assuming a sharp separation between a fully converted region and a fully unreacted one. Herein the present study, an improved porous solid model is proposed. This model solves the mass balances of the individual gas species and the solid ones assuming spherical symmetry. The governing equations, the main algorithm, and validation cases are presented. The present model also offers wide flexibility to incorporate complex phenomena such as porosity changes or carbon deposition. Furthermore, the proposed model is integrated into a computational fluid dynamics (CFD) environment. It is verified that identical input parameters yield almost identical results in both frameworks, opening the gate toward reliable CFD simulations of industrial‐scale reactors.

The thermochemical conversion of biomass, through gasification and consecutive fuel synthesis, can produce high-quality fuels. Entrained-flow gasification is regarded as the forthcoming technology providing syngas of sufficient quality, though the technology readiness level needs to be raised to allow its wide use. To this end, investigations within the bioliq project have been conducted on the gasification of fast pyrolysis products: pyrolysis oil and biochar, forming together a so-called bioslurry. This article will present the parametrization and results of numerical simulations of entrained-flow gasification. A first set of simulations on the gasification of a liquid fuel on two well-referenced experimental data sets is presented. Here, the liquid is monoethylene glycol, a surrogate for pyrolysis oil. Then, simulations of slurry fuels are considered, where the conversion of the biochar particles is numerically solved with a sectional approach. The simulations prove to retrieve the experimental results with a high accuracy, thus making CFD simulations based on the proposed approaches an adapted tool to investigate further operating conditions or for scaling-up. Particular attention is drawn on the parametrization of the approach. It will be shown that the majority of the model’s parameters, such as the pseudospecies size distribution, composition, and thermodynamic properties, can be derived from regular analytical chemistry techniques. The parameter with the highest sensitivity was identified to be the gasification reaction rate of the secondary char. The proposed model is sensitive to the properties of different types of biochar as well as to the amount of solid in the slurry fuel. By presenting a methodology, which can be quickly adapted to further solid fuels, the present work will allow for tackling the variability of biomass-derived fuels and find suitable operating conditions adapted to specific biomass conditions.

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