gasification of lignin rich residues for the production of biofuels via syngas fermentation comparison of gasification technologies

This paper reports the use of lignin-rich residues from second generation bioethanol production, to produce syngas that can be applied in the gas fermentation process. Three gasification technologies at a different scale were considered in this study. Fixed bed updraft gasification of about 30 kg/h solid feed, bubbling fluidized bed gasification of about 0.3 kg/h solid feed and indirect gasification of about 3 kg/h solid feed. Two lignin-rich residues with different properties were tested and the results were evaluated in terms of feedstock pretreatment (grinding, drying and pelleting) and syngas quality requirements for the fermentation process. The molar H 2 /CO ratio (ranging from 0.6 to 1.0) and the tar yield (18–108 g/Nm 3 ) obtained from the three gasification technologies was quite different. For the syngas fermentation process, low H 2 to CO ratio is preferred, as most of the organisms grow better on CO than H 2 . Furthermore, different contents of impurities that can reduce the fermentability of the gas (such as hydrocarbons, HCN, HCl, NH 3 , COS and other organic S- compounds) were detected in the product gas. The concentration of these compounds in the syngas is related to the content of the corresponding compounds in the original feedstock. The different characteristics of the lignin-rich feedstocks are related to the specific pre-treatment technologies for the (hemi)cellulose extraction. By tuning the pre-treatment technology, the properties of the feedstock can be improved, making it a suitable for gasification. Tar and unsaturated hydrocarbon compounds need to be removed to very low levels prior to the fermentation process. As a next step, the combination of the gasification and the appropriate product gas cleaning, with the syngas fermentation process for the production of bio-alcohols will be evaluated and the overall efficiency of the gasification-fermentation process will be assessed. © 201

Screening of winery and olive mill wastes for lignocellulolytic enzyme production from Aspergillus species by solid-state fermentation

Wastes from olive oil and wine industries (as exhausted grape marc, vineshoot trimmings, two-phase olive mill waste, vinasses, and olive mill wastewater) were evaluated for lignocellulolytic enzyme production (as endocellulases, endoxylanases, and feruloyl esterases) by solid-state fermentation (SSF) with Aspergillus niger, Aspergillus ibericus, and Aspergillus uvarum. To study the effect of different solid medium composition and time in enzyme production, a PlackettBurman experimental design was used. Variables that had a higher positive effect in lignocellulolytic enzyme production were urea, time, and exhausted grape marc. The maximum values of enzymatic activity per unit of substrate dry mass were found with A. niger for feruloyl esterase. Enzymatic extracts from SSF with A. niger achieved maximum feruloyl esterase activity (89.53 U/g) and endoxylanase activity (3.06 U/g) and with A. uvarum for endocellulase activity (6.77 U/g). The enzyme cocktails obtained in the SSF extracts may have applications in biorefinery industries.Jose Manuel Salgado is grateful for the postdoctoral fellowship (EX-2010-0402) of the Education Ministry of Spanish Government. Luis Abrunhosa was supported by the grant SFRH/BPD/43922/2008 from Fundacao para a Ciencia e Tecnologia-FCT, Portugal

A Fractal Approach To the Analysis of Low-temperature Combustion-rate of A Coal Char .2. Model Development

There is increasingly large body of evidence for the existence of carbons characterized by a porous structure amenable to a topological representation based on the concepts of fractal geometry (Part I[1] and references therein). Moving from these findings, a model based on simple hypotheses is proposed for the prediction of the combustion rate of carbons characterized by a fractal pore structure. Its concern is the low temperature combustion behavior of carbons under conditions typical of chemical, kinetically controlled regime. The soundness of the model is checked satisfactorily by comparing its predictions against those obtained by a more detailed approach based on the recursive application of the Thiele analysis. The proposed model provides a useful framework for interpreting the experimental results presented in Part I[1], obtained in combustion of char from a bituminous coal. It is inferred that diffusion of oxygen within micropores is strongly activated, even at the moderately high temperature used in the combustion experiments. The formation of relatively stable oxygen-carbon complexes by dissociative oxygen chemisorption and the scarce mobility of oxygen in the chemisorbed state are indicated as possible reasons for the limited accessibility of the micropore surface

A transient kientics study of the combustion reactivity of a coal char

Transient kinetics experiments have been used to characterize the combustion reactivity and the reactive surface area of char obtained from a bituminous coal. They consisted of isothermal-pulsed combustion of char samples with reiterated combustion and desorption stages. Experiments showed that the combustion rate passed through a sharp maximum at the begnning of each combustion stage, to decline afterwards as the carbon conversion degree increased. Combustion rate and reactive surface area have been determined as functions of the carbon conversion degree and of the oxygen partial pressure during the combustion stage. Direct correlation between combustion rate and reactive surface area is satisfactory at lowoxygen partial pressure; it becomes poorer when data at higher pressure are included in the comparison. A descriptive model based on a Monte Carlo simulation technique has been developed to shed light onsome features of transient and steady behaviour observed in experiments. In particular, the relevance of nonuniform reactivity of the exposed surface to the combustion behaviour and to overall char reactivity is assessed on the basis of qualitative comparison between model calculations and experimental results. Simulation results suggest that a pronounced "screening effect" of more stable surface oxides with respect to more reactive ones takes place. It should be responsible for the sharp maxima observed in the combustion rate vs time experimental relationship at the beginning of the combustion stages. The model predicts the steady combustion rate to be lower than that obtained by averaging the intrinsic reactivity of different classes of active sites on the basis of their concentrations in the unconverted solid. © 1994 Combustion Institute

A Fractal Approach To the Analysis of Low-temperature Combustion-rate of A Coal Char .1. Experimental Results

The combustion reactivity of char obtained by devolatilization of South African bituminous coal has been investigated by thermogravimetric analysis in the temperature range of 653 to 733 K at oxygen partial pressures from 0.21 to 1 bar. Samples of the same char, either unreacted or preburned in a fixed bed reactor to given levels of carbon burn-off, have been characterized from the standpoints of their surface area and of their volume and size distribution of pores. Different experimental techniques, namely mercury porosimetry and adsorption of either carbon dioxide or nitrogen, and models for the interpretation of porosimetric data have been used. Analysis of meso- and macropore size distributions, and of adsorption isotherms in the low relative pressure region, has been directed to check whether the topological structure of the porous matrix of the char might be described as a fractal

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

Etanolo da biomasse lignocellulosiche. Produzione di etanolo da paglia di grano mediante pretattamento di steam explosion, idrolisi enzimatica e fermentazione

Consiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7 Rome / CNR - Consiglio Nazionale delle RichercheSIGLEITItal