Hydrothermal liquefaction process of food waste in batch and continuous lab scale reactors

Due to the energy burden that represents the drying step, wet biomass is often underexploited for energy purpose. Indeed, this step represents one of the most energy consuming step in a thermochemical process and is often economically prohibitive. During hydrothermal liquefaction, conversion of biomass takes place at temperatures between 250 and 374 °C and at pressures above the saturation pressure to ensure that water remains in the liquid phase, typically above 100 bars, avoiding enthalpy energy penalties [1]. To avoid competitive use of land for food supply and excessive cost of entrance biomass, blackcurrant pomace and brewery’s spent grains have been selected and tested on liquefaction as food residues. Experiments have been carried out in a 600 mL batch reactor (PARR), allowing maximum temperature of 320°C and maximum pressure of 130 bars. Effects of operating parameters such as temperature and holding time, biomass pretreatment and reactor configuration are investigated on mass yields, aqueous phase composition and energy balance. Results obtained in the batch reactor constitute the reference of this study, in the comprehension of the mechanism of the liquefaction of food residues. Also, these results form the basis for a model to scale up the process, and are confronted to the results on a continuous lab scale plant. Please click Additional Files below to see the full abstract

Heat of reaction of hydrothermal liquefaction reactions

Wet waste streams include a wide variety of products such as food processing residues, sewage sludge but also the organic fraction of municipal solid waste. Humidity typically varies from 50 to above 90 %. Dewatering and drying is possible for most feedstocks but at a significant cost. Hydrothermal liquefaction produces a biocrude that can be further upgraded into biofuels. The conversion takes place at temperatures between 250 and 400 °C and at pressures above the saturation pressure to ensure that water remains in the liquid phase, typically above 100 bar [1]. Even though the basic principles of hydrothermal liquefaction are well known, there are still some significant scientific questions and technical issues. One of the important questions that remain is the heat of reaction and the heat balance of the reaction. Please click Additional Files below to see the full abstract

Modélisation des phénomènes de désactivation des catalyseurs à base de cobalt utilisés dans différent réacteurs de synthèse Fischer-Tropsch

La désactivation reste un enjeu important lors de la synthèse Fischer-Tropsch, car il limite la vie des catalyseurs, ainsi que leurs productivités catalytiques. Elle peut être liée à certains mécanismes selon la littérature. Le frittage a été proposé comme la source principale de désactivation initiale, et avec le cokage comme phénomène responsable de la désactivation à long-terme dans ce travail. Le but de cette thèse est de développer les modèles mécanistiques capables de prédire le changement d activité catalytique des catalyseurs FT à base de cobalt avec le temps. Dans la première étape, le changement des propriétés physico-chimiques des particules avec le temps est considéré. Un modèle de frittage est développé, qui inclut l effet d accélération de l eau par formation d une couche d oxyde de cobalt à la surface. Ce mécanisme nous permet de lier l agglomération des particules à certaines conditions opératoires, notamment le rapport molaire de H2O/H2. Nous avons aussi développé un mécanisme pour l empoisonnement des sites catalytiques par dépôt de carbone pour la désactivation à long-terme. Ce mécanisme permet d évaluer le changement de fraction des sites libres avec le temps, ainsi que les fractions molaires de CO, H2, et H2O.Ces deux modèles microscopiques sont ensuite intégrés dans les modèles des réacteurs à lit fixe et slurry pour coupler les propriétés des catalyseurs et l activité catalytique. L effet des conditions opératoires sur la taille des cristallites, la fraction des sites actifs et la conversion sont considérés. Les modèles sont ensuite employés dans les réacteurs de laboratoire pour s accorder avec les résultats expérimentaux.Catalyst deactivation remains a major challenge in Fischer-Tropsch synthesis; as it reduces the catalyst lifetime as well as its productivity. Deactivation can be attributed to certain mechanisms according to the literature. Sintering is proposed in this work to be responsible for the initial deactivation whereas coking is suggested to be the main cause of long-term deactivation. The final objective of this thesis is to develop the mechanistic models which could predict the extent of catalyst deactivation with time. In the first step, the change in the catalyst physico-chemical properties with time on stream is considered. A three-step sintering model is proposed which involves the effect of water acceleration through the formation of surface cobalt oxide layer. This mechanism allows correlating the crystallites growth with certain operating conditions especially the H2O/H2 molar ratio inside the reactor. We have also developed a mechanism for the active site poisoning by carbon deposition for the long-term deactivation. This mechanism helps to evaluate the change in the active sites coverage with time as well the CO, H2, and H2O mole fractions. The two microscopic models are then integrated in the reactor models in order to correlate the change in the catalytic activity with the catalyst properties. We have developed the models dedicated to fixed bed and slurry reactors. The effect of operating conditions on the crystallite size, active sites fraction, and conversion is considered by the simulations. The models are then employed in the laboratory scale reactors to fit the experimental data and to optimize the deactivation constants.LILLE1-Bib. Electronique (590099901) / SudocSudocFranceF

Etude et modélisation cinétique individuelle et par regroupements des réactions d'hydrotraitement sur catalyseur commercial CoMo/Al2O3

Dans un contexte de forte demande en carburants, la diversification des charges pétrolières et la sévérité des normes actuelles sur les carburants conduisent à des modifications des unités industrielles de raffinage en vue de leur optimisation. L approche proposée dans cette thèse consiste à améliorer la description des cinétiques des réactions d hydrotraitement des gazoles pour pouvoir prédire les effets de changements de conditions opératoires et de charge dans un simulateur du procédé industriel. La cinétique a été étudiée pour 7 charges de compositions initiales différentes sur catalyseur commercial CoMo/Al2O3 pour des températures comprises entre 320C et 380C à 45MPa de pression. La méthodologie adoptée a permis de balayer une gamme de soufre final allant de 5000 ppm jusqu à quelques ppm correspondant à l HDS ultra-profonde. Un réacteur parfaitement agité continu (Mahoney-Robinson) a été utilisé pour mesurer les vitesses de réaction. Des techniques analytiques (Sulf UV, CPG-SCD, CPG-NCD, HPLC) ont été mises au point pour quantifier les espèces soufrées, azotées et aromatiques présentes dans les gazoles. L influence de H2, H2S, des familles de réactivité a pu ainsi être observée. Un modèle cinétique de forme Langmuir-Hinshelwood à deux sites (voies hydrogénante et désulfuration directe) pour l HDS des espèces soufrées individuelles a été établi. Il intègre 188 paramètres cinétiques pour 33 composés et a donné des résultats satisfaisants. L H2S est le composé le plus inhibiteur pour la voie DDS et les composés di- et tri-aromatiques pour la voie d hydrogénation. Enfin, un modèle pour l HDA et l HDN des différentes familles identifiées est également proposé.In the context of a growing demand for fuel, the diversity of feedstocks and the severity of the actual specifications have led to major modifications in the industrial refinery processes for their optimization. The approach of this thesis consists in improve the kinetic descriptions of the hydrotreatment reactions of gas oils to predict the effects of operating conditions and gas oil nature changes in an industrial process simulator. The kinetic has been studied for 7 gas oils with different initial compositions over a CoMo/Al2O3 commercial catalyst for 320-380C range of temperature and 45MPa total pressure. The methodology used in this work has permitted to cover a total sulfur range from 5000ppm to few ppm corresponding to the deep HDS. A continuous stirred tank reactor (Mahoney-Robinson) has been used to measure the reactions rates. Analytic technics (Sulf UV, CPG-SCD, CPG-NCD, HPLC) have been set to quantify the sulfur, nitrogen and aromatic species present in the gas oils. The influence of H2, H2S, individual sulfur species or reactivity groups of sulfur species, groups of aromatic and nitrogen compounds have been observed. A bi sites kinetic model (hydrogenation and direct desulfurization pathways) for the HDS of the individual sulfur species resulting from a Langmuir-Hinshelwood mechanism has been established with 188 parameters for 33 compounds and has given satisfying results. The H2S is the most inhibiting compound for the direct desulfurization and the di- and tri-aromatics for the hydrogenation. At last, a model for the HDA and HDN of the different identified families is presented as well.LILLE1-Bib. Electronique (590099901) / SudocSudocFranceF

Hybrid catalysis: Study of a model reaction for one-pot reactor combining an enzyme and a heterogeneous catalyst

International audienc

Development of a kinetic model for HTL conversion of waste biomass

International audienceThe objective of this work is to develop a simulation tool in order to predict the HTL product distribution in term of aqueous phase, gas phase, bio-oil and bio-char for an organic waste based on it biochemical composition and the conversion conditions (temperature and residence time). A reaction scheme was proposed after compositional analysis of the resources and the reaction products. The kinetic parameter of this mechanism were optimized by minimizing the differences with the experimental yields of gas, aqueous phase, bio-oil and bio-char for 24 experimental points. Each point was produced from 2 to 4 experiments.The model is able to reproduce the evolution of the different product fraction with time except at the beginning between 0 and 20 min this is during the heat up time were the temperature is always changing leading to a non-stationery situation. This tool can be used for a process simulation in the prediction of product yields and. To obtain a more precise model, a work is ongoing in the laboratory with quantification of intermediate species in an objective of developing a comprehensive and predictive model of intermediate species or intermediate family of species.

Evaluation of the Heat Produced by the Hydrothermal Liquefaction of Wet Food Processing Residues and Model Compounds

Hydrothermal liquefaction has proven itself as a promising pathway to the valorisation of low-value wet food residues. The chemistry is complex and many questions remain about the underlying mechanism of the transformation. Little is known about the heat of reaction, or even the thermal effects, of the hydrothermal liquefaction of real biomass and its constituents. This paper explores different methods to evaluate the heat released during the liquefaction of blackcurrant pomace and brewers’ spent grains. Some model compounds have also been evaluated, such as lignin, cellulose and glutamic acid. Exothermic behaviour was observed for blackcurrant pomace and brewers’ spent grains. Results obtained in a continuous reactor are similar to those obtained in a batch reactor. The heat release has been estimated between 1 MJ/kg and 3 MJ/kg for blackcurrant pomace and brewers’ spent grains, respectively. Liquefaction of cellulose and glucose also exhibit exothermic behaviour, while the transformation of lignin and glutamic acid present a slightly endothermic behaviour

Development of a kinetic model for HTL conversion of waste biomass

International audienceThe objective of this work is to develop a simulation tool in order to predict the HTL product distribution in term of aqueous phase, gas phase, bio-oil and bio-char for an organic waste based on it biochemical composition and the conversion conditions (temperature and residence time). A reaction scheme was proposed after compositional analysis of the resources and the reaction products. The kinetic parameter of this mechanism were optimized by minimizing the differences with the experimental yields of gas, aqueous phase, bio-oil and bio-char for 24 experimental points. Each point was produced from 2 to 4 experiments.The model is able to reproduce the evolution of the different product fraction with time except at the beginning between 0 and 20 min this is during the heat up time were the temperature is always changing leading to a non-stationery situation. This tool can be used for a process simulation in the prediction of product yields and. To obtain a more precise model, a work is ongoing in the laboratory with quantification of intermediate species in an objective of developing a comprehensive and predictive model of intermediate species or intermediate family of species.