Análise do impacto do processo organosolv para pré-tratamento de biomassa lenhocelulósica na redução das emissões de gases com efeito de estufa (GEE)

CIES2020 - XVII Congresso Ibérico e XIII Congresso Ibero-americano de Energia SolarRESUMO: No âmbito do projeto H2020 AMBITION, foram desenvolvidos processos de pré-tratamento inovadores e energeticamente eficientes, a fim de serem integrados num conceito de melhoria do processamento da biomassa para a produção de correntes líquidas de açúcares e derivados de lenhina para aplicações em bioenergia e produtos de valor acrescentado. O objetivo deste trabalho consiste em analisar os impactos ambientais do pré-tratamento organosolv de biomassa (palha de trigo e resíduos de eucalipto) utilizando misturas etanol/água, a fim de avaliar a sua integração num processo multiproduto de modo a originar elevados rendimentos de açúcares e recuperar lenhina de alta qualidade num conceito de biorrefinaria. O processo foi simulado em SuperPro Designer (Intelligen Inc.) para determinar os balanços de massa e energia, bem como para desenvolver o Inventário de Ciclo de Vida (LCI). A Avaliação do Ciclo de Vida (ACV) foi realizada utilizando o software SimaPro 9.0 (PRé Consultants BV) com a base de dados Ecoinvent 3.5, sendo comparada com os processos clássicos de pré-tratamento à escala industrial (e.g. explosão com vapor). O processo organosolv com etanol e para uma razão líquido-sólido (RLS) padrão de 10, apresenta resultados em termos de emissões de GEE (numa abordagem gate-to-gate) ligeiramente superiores aos obtidos para a explosão com vapor, concluindo-se posteriormente que na tecnologia organosolv, só a redução da RLS pode conduzir a melhorias significativas em termos ambientais.ABSTRACT: Within the H2020 AMBITION project, innovative and energy efficient pre-treatment processes were developed in order to be integrated in a biomass processing improvement concept that would produce liquid streams of sugars and lignin derivatives for applications in bioenergy and added-value products. The objective of this work is to analyse the environmental impacts of organosolv pre-treatment of biomass (wheat straw and eucalyptus residues) using ethanol/water mixtures in order to assess its integration in a multi-product process to produce high sugar yields and recover high quality lignin in a biorefinery concept. The process was modelled in SuperPro Designer (Intelligen Inc.) to determine mass and energy balances as well as to develop the Life Cycle Inventory (LCI). The Life Cycle Assessment (LCA) was performed using SimaPro 9.0 software (PRé Consultants BV) with the Ecoinvent 3.5 database and compared with classical industrial scale pre-treatment processes (e.g. steam explosion). The organosolv process with ethanol with a standard liquid-to-solid ratio (LSR) of 10, presents, in terms of GHG emissions (in a gate-to-gate approach), slightly higher GHG emissions than those obtained for the steam explosion, leading to the conclusion that a reduction in the solid-liquid ratio in organosolv technology causes significant environmental improvements.info:eu-repo/semantics/publishedVersio

A pragmatic continuum level model for the prediction of the onset of keyholing in laser powder bed fusion

Laser powder bed fusion (L-PBF) is a complex process involving a range of multi-scale and multi-physical phenomena. There has been much research involved in creating numerical models of this process using both high and low fidelity modelling approaches where various approximations are made. Generally, to model single lines within the process to predict melt pool geometry and mode, high fidelity computationally intensive models are used which, for industrial purposes, may not be suitable. The model proposed in this work uses a pragmatic continuum level methodology with an ablation limiting approach at the mesoscale coupled with measured thermophysical properties. This model is compared with single line experiments over a range of input parameters using a modulated yttrium fibre laser with varying power and line speeds for a fixed powder layer thickness. A good trend is found between the predicted and measured width and depth of the tracks for 316L stainless steel where the transition into keyhole mode welds was predicted within 13% of experiments. The work presented highlights that pragmatic reduced physics-based modelling can accurately capture weld geometry which could be applied to more practical based uses in the L-PBF process

3D Finite Element Analysis in the selective laser melting process

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On the influence of building position on dimensional accuracy and surface quality of aluminum blocks manufactured by L-PBF

The precision of the objects fabricated by laser powder bed fusion (LPBF) and their overall quality is currently commonly increased by process optimization, however the relatively complicated process-structure–property relationship may represent a significant obstacle to its efficiency. This study aims to determine the effects of the position of L-PBF manufactured blocks on the building plate on their geometrical dimensions, tolerances (GD&T) and surface roughness. Within the study, 9 cubical specimens were manufactured from AlSi10Mg powder via LPBF using optimized process parameters, consistent for all the samples, and their GD&T and surface roughness were subsequently analyzed by CMM and perthometer. The system utilized to manufacture the samples was supplied with 200 W Yb-laser with the 90 µm diameter of the laser spot. The fabrication of the blocks and their subsequent GD&T analysis were simulated numerically to further explain the mechanisms of distortion creation. Numerical results were validated by experiments, where the maximal relative error reached 6.88 %. Statistical significance of position on GD&T was demonstrated for dimensional deviations, bottom faces planarity, parallelism of top and bottom faces and perpendicularity of top and x-oriented faces and the regression equations were assessed (with R2 96.30 %, 93.09 % and 99.79 %, 94.54 %, 98.47 %, 99.65 %, and 99.28 %, respectively). The lowest dimensional errors (0.0738 mm in x-, 0.1048 mm in y-, and −0.3844 mm in z-direction) were detected in the block located in the middle of the building plate, which can be reasoned by favorable thermal fields as the specimens are surrounded from all sides by other blocks cumulating heat. Similarly as with dimensional errors, the errors of planarity, parallelism and perpendicularity correlated with the thermal fields over the building platform, resulting in the least distorted cube located in the middle of the base plate

Pilot plant air-steam gasification of nut shells for syngas production

Autothermal gasification of hazelnut and almond was carried out and the performances of a pilot plant with a feeding rate of 20-30 kg/h were evaluated. Air, mixes of air with steam and oxygen with steam were used as gasification medium; the gas flows corresponded to different equivalence ratios of combustion, ER(O2), and water reaction, ER(H2O). The recording of the thermal profile inside the reactive bed during the runs made it possible to highlight a sequence of exothermic and endothermic reactions. In the plant tests, the residues were completely converted in gaseous and liquid energy carriers with a cold gas efficiency (CGE) ranging from 61% to 75% while the production of biooil ranged from 90-250 g/kg of fed nutshell (dry basis). The molar ratio H2/CO in syngas increased by using steam as co-gasification agent. Steam was necessary to stabilize the process in the case of using oxygen as main gasification agent. Oxy-steam gasification also provided the best results in terms of syngas heating value and thermal power output of the plant. The tar yield was inversely correlated to the residence time of the gas in the bed, in according with a zero order reaction for tar cracking into incondensable hydrocarbons. © 2017, ETA-Florence Renewable Energies. All rights reserved