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Producción de bio-hidrógeno mediante gasificación catalítica de biomasa con captura integrada de CO2
|Autor:||Esteban Díez, Gonzalo|
|Director:||Pevida García, Covadonga ; Rubiera González, Fernando|
|Fecha de publicación:||2017|
|Editor:||Universidad de Oviedo|
|Resumen:||[EN]Hydrogen has been proposed as the energy carrier of the future. How-ever, for the Hydrogen Economy to be feasible, hydrogen production must be cheap, accessible and sustainable. Nowadays, more than 96% of H₂ is produced from fossil fuels, contributing to increase the CO₂ con‑centration in the atmosphere and leading to a progressive Climate Change. The most widespread method for hydrogen production con-sists in the steam reforming of methane (SMR), which employs several catalytic reactors at different temperatures to produce gas with a 70% H₂ content that should be later purified.
In this context, integration of steam reforming and CO₂ capture in a sin‑gle step process called Sorption Enhanced Steam Reforming (SESR) is considered a promising technology. This process allows to reduce the number of required reactors and the reaction temperature, increasing yield and H₂ purity at the same time. The ultimate consequence is to achieve lower costs of installation and operation. Additionally, if a re-newable fuel like biomass is fed to the reactor, production of cheaper, accessible and sustainable hydrogen is possible, as biomass has zero net impact in the atmospheric CO₂ concentration, thus reducing the contri‑bution of hydrogen to Climate Change.|
To optimize the SESR process, an appropriate selection of catalyst and sorbent for CO₂ must be made, together with a proper optimization of the operating conditions. A Pd/Ni-Co-hydrotalcite derived material has been chosen as catalyst, while dolomite has been selected as CO₂ sorbent. All experiments were preceded by thermodynamic equilibrium calculations to estimate the maximum limits of yield, selectivity and concentration of products. This results were later compared with the ex-perimental results obtained. A fluidized bed reactor was employed to assess the optimal conditions for the SESR process. The three main variables modified during these experiments were temperature, steam to carbon ratio (S/C) and weight hourly space velocity (WHSV). Acetone was employed as model com-pound to simulate the behaviour of biomass pyrolysis derived bio-oil.
The fluidized bed reactor was also employed to investigate the effect of bio-oil composition on the performance of the SESR process. The behav-iour of blends with different proportions of acetic acid and acetone was tested along a wide range of temperatures. The values of steam propor-tion and WHSV were chosen from the optimized parameters obtained in the previous work. Thereafter, to reach a deeper knowledge of the influence of composition, several blends of phenol, acetic acid and ace-tone were prepared at similar proportions to those found in pyrolysis bio-oil, and tested for the SESR process. Sorption Enhanced Catalytic Steam Gasification (SECSG) was carried out employing two solid lignocellulosic biomasses. During these exper-iments, a fixed bed reactor was fed semi‑continuously with the bio‑masses in order to evaluate the effect of temperature and biomass composition on yield and H₂ production. The present work has demonstrated that temperature is the most influ-ent factor in the SESR process, followed by S/C and WHSV. It is possible to achieve a H₂ purity higher than 99.5% between 525 and 625 °C, for both the model compounds and the lignocellulosic biomass. However, other process variables such as H₂ yield and selectivity are greatly af‑fected by the nature of the fuel and the reactor employed, needing higher temperatures to reach the same values. The concentration of some by-products, like CO and CH₄, is also very sensitive to changes in temperature and feed, increasing when the process moves away from the optimal conditions.
|Descripción:||Tesis doctoral presentada en el Departamento de Energía de la Universidad de Oviedo, 2017.|
|Aparece en las colecciones:||(INCAR) Tesis|
Ficheros en este ítem:
|TD_Esteban_Díez_Gonzalo.pdf||9,62 MB||Adobe PDF|
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