• Energy Research

The catalytic co-pyrolysis of grape seeds and waste tyres for the production of high-quality bio-oils was studied in a pilot-scale Auger reactor using different low-cost Ca-based catalysts. All the products of the process (solid, liquid, and gas) were comprehensively analysed. The results demonstrate that this upgrading strategy is suitable for the production of better-quality bio-oils with major potential for use as drop-in fuels. Although very good results were obtained regardless of the nature of the Ca-based catalyst, the best results were achieved using a high-purity CaO obtained from the calcination of natural limestone at 900 °C. Specifically, by adding 20 wt% waste tyres and using a feedstock to CaO mass ratio of 2:1, a practically deoxygenated bio-oil (0.5 wt% of oxygen content) was obtained with a significant heating value of 41.7 MJ/kg, confirming its potential for use in energy applications. The total basicity of the catalyst and the presence of a pure CaO crystalline phase with marginal impurities seem to be key parameters facilitating the prevalence of aromatisation and hydrodeoxygenation routes over the de-acidification and deoxygenation of the vapours through ketonisation and esterification reactions, leading to a highly aromatic biofuel. In addition, owing to the CO2-capture effect inherent to these catalysts, a more environmentally friendly gas product was produced, comprising H2 and CH4 as the main components.

4 figures, 2 tables.-- Supplementary information available.-- © 2016. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/ The production of upgraded bio-oils by an integrated process using a mixture of calcined limestone and sand as a heat carrier with catalytic properties was experimentally studied at pilot scale. The integrated process consisted of two main steps: biomass catalytic pyrolysis in an Auger reactor for bio-oil production and char combustion in a fluidised-bed combustor for heat carrier heating and regeneration. A temperature of 450 °C was fixed as an optimum value to carry out the catalytic pyrolysis step. Temperatures ranging from 700 to 800 °C were assessed in the char combustor. Process simulation demonstrated that solid recirculation from the combustor to the pyrolysis reactor was marginally affected in this temperature range. However, an optimum char combustion temperature of 800 °C was selected from an environmental point of view, since lower polyaromatic emissions were detected whilst NOx emissions were kept under the legislation limits. Under designated conditions, several pyrolysis-combustion cycles were carried out. A moderate deactivation of the catalyst by partial carbonation was found. This fact makes necessary the incorporation of a purge and an inlet of fresh heat carrier in order to maintain the bio-oil quality in the integrated process. Authors thank to Spanish MINECO and European Union FEDER funds for providing support for this work (projects CTQ2012-37984-C02-01 and ENE2015-68320-R). Peer reviewed

Catalytic co-pyrolysis of grape seeds and waste tyres was performed in a fixed-bed reactor using calcined calcite as a catalyst. The organic phase obtained was analysed for its further application as a potential and stable drop-in fuel. Remarkable positive effects were achieved after the joint incorporation of both waste tyres and calcined calcite to grape seeds in the process. More specifically, the addition of considerable amounts of waste tyres (between 20 and 40 wt%) with a constant ratio of feedstock to calcined calcite of 1 were considered the optimal experimental conditions to promote positive synergistic effects on bio-oil yields and its characteristics as a fuel. Thus, when the proportion of waste tyres in the feed reached 40 wt%, the organic phase yield was considerable improved, reaching up values higher than 73 wt%, significantly greater than those obtained from conventional pyrolysis (61 wt%). Moreover, oxygen content was reduced to 4.2 wt%, minimizing any problems related to corrosivity and instability. HHV was enlarged from 15.3 up to 27.3 MJ/kg, significantly increasing the value of the resulting bio-oil. pH values and specially total acid number were also improved reaching values down to 1 mg KOH/gbio-oil in all cases. Additionally, a more valuable chemical composition was achieved since the production of aromatic and cyclic hydrocarbons was maximized, while a significant reduction in phenolic compounds was achieved. Moreover, bio-oil sulphur content was drastically reduced in comparison with the pyrolysis of waste tyres by itself from 0.6 down to 0.2 wt%. The role of calcined calcite was directly related to the promotion of dehydration reactions of acids and phenols in order to generate hydrocarbons. On the other hand, radical interactions between the biomass and waste tyres pyrolysis products played a fundamental role in the production of more valuable compounds. Finally, the CO2 capture effect produced a more environmentally friendly gas while maintaining its calorific value.

Abstract Scrap tyres are a growing environmental problem because they are not biodegradable and their components cannot readily be recovered. In this investigation, the thermochemical recycling of rubber from old tyres by pyrolysis and the value of the products obtained have been studied. First, thermobalance experiments were carried out, studying the influence of the following variables: heating rate, flow rate, particle size and temperature. These thermobalance results were extended by performing experiments in a fixed bed reactor, studying the effect of the main process variables on yields of derived products: oils, gases and solid residue. The oils have been characterized using a combination of analytical techniques (TLC–FID, GC–MS and simulated distillation). No relationship between functional group composition of the oils determined by TLC–FID and process variables was found. The carbonaceous material obtained was characterized by N 2 and CO 2 adsorption. The possible uses of this char have been analyzed taking into account and calculating the emissions that would be produced if the char were burnt.

The characteristics of bio-oil produced from biomass pyrolysis can be improved by co-feeding waste materials. In this work, co-pyrolysis of lignocellulosic biomass with six different waste plastics (waste tyre (WT), polylactic acid (PLA), polystyrene (PS), polyethylene terephthalate (PET), polypropylene (PP) and high density polyethylene (HDPE)) were conducted in a thermogravimetric analyser to study thermal decomposition of the mixtures. The distributed activation energy model (DAEM) was applied to pure feedstocks at 5 and 10 °C/min heating rates to fit the kinetic parameters. The model was used to simulate the co-pyrolysis of biomass/plastic mixtures assuming additive effect of components at different weight proportions and heating rates. Profiles of the fraction of mass remaining for mixtures at 100 °C/min were reproduced with a remarkable agreement. Discrepancies between the experimental and calculated profiles were considered as a measure of the extent of interactions occurring in the co-pyrolysis. Projections of the behaviour of mixtures under flash pyrolysis conditions were performed to study important aspects of the process, such as radical interactions and optimum working temperature The authors wish to thank the Spanish MINECO and European Union FEDER funds (project ENE2015-68320-R) and the Regional Government of Aragon (DGA) for the research groups support programme (project T04_17R). Peer reviewed

AbstractGasification represents a potential technology for the conversion of biomass into usable energy. The influence of the main gasification parameters, i.e. the type of biomass used and its composition, as well as the composition of the outlet gas, were studied by a multivariate statistical analysis based on principal component analysis (PCA) and partial least square (PLS) regression models in order to identify the main correlations between them and to the contents of methane, ethylene and tar in the outlet gas. In this work, the experimental data used as input for the multivariate statistical analysis came from a TRL-4 gasification plant running under sorption enhanced conditions, i.e. using steam as the gasifying agent and CaO as the bed material. The composition of the biomass feed played an important role in the quality of the outlet gas composition. In fact, biomasses with high ash and sulphur contents (municipal solid waste) increased ethylene content, while those with high-volatile matter content and fixed C content (wood pellets, straw pellets and grape seeds) mainly increased CO and CO2 formation. By increasing the gasification bed temperature and the CaO/C ratio, it was possible to reduce the methane and the collected tar contents in the outlet gas. Other light hydrocarbons could also be reduced by controlling the Treactor and TFB. Methane, ethylene and tar contents were modelled, cross-validated and tested with a new set of samples by PLS obtaining results with an average overall error between 8 and 26%. The statistically significant variables to predict methane and ethylene content were positively associated to the thermal input and negatively to the CaO/C ratio. The biomass composition was also remarkable for both variables, as mentioned in the PCA analysis. As far as the tar content, which is undesirable in all gasification processes, the decrease in the tar content was favoured by high bed temperature, low thermal input and biomass with high-volatile matter content. In order to produce an outlet gas with adequate quality (e.g. low tar content), a compromise should be found to balance average bed temperature, sorbent-to-mass ratio, and ultimate and proximate analyses of the biomass feed. Graphical abstract