Probing synergies between lignin-rich and cellulose compounds for gasification

The fixed bed gasification of lignin rich and deficient mixtures was carried out to probe the synergistic effects between two model compounds, Lignin Pink (LP) rich in Na and Cellulose Microcrystalline (CM). Reaction conditions utilized the most commonly used air ratios in current wood gasifiers at 750 °C and 850 °C. It was found that by increasing the lignin content in the mixture, there was a selectivity change from solid to gas products, contrary to a similar study previously carried out for pyrolysis. This change in product mix was promoted by the catalytic effect of Na edge recession deposits on the surface of the char. As a result, the water gas shift reaction was enhanced at 850 °C for the LP48CM52 mixture across all air ratios, this was evidenced by a strong correlation between the produced H2 and COx. Meanwhile, by lowering the lignin content in the mixtures, the reactivity of cellulose microcrystalline was found to generate more char at higher temperature, similar to lignin mixtures when undergoing pyrolysis

Products from the high temperature pyrolysis of RDF at slow and rapid heating rates

The high-temperature pyrolysis behaviour of a sample of refuse derived fuel (RDF) as a model of municipal solid waste (MSW) was investigated in a horizontal tubular reactor between 700 and 900 °C, at varying heating rates, and at an extended vapour residence time. Experiments were designed to evaluate the influence of process conditions on gas yields as well as gas and oil compositions. Pyrolysis of RDF at 800 °C and at rapid heating rate resulted in the gas yield with the highest CV of 24.8 MJ m-3 while pyrolysis to 900 °C at the rapid heating rate generated the highest gas yield but with a lower CV of 21.3 MJ m-3. A comparison of the effect of heating rates on oil products revealed that the oil from slow pyrolysis, contained higher yields of more oxygenates, alkanes (C8-C39) and alkenes (C8-C20), while the oil from rapid pyrolysis contained more aromatics, possibly due to the promotion of Diels-Alder-type reactions

Comparative Studies of the Pyrolytic and Kinetic Characteristics of Maize Straw and the Seaweed Ulva pertusa

Seaweed has attracted considerable attention as a potential biofuel feedstock. The pyrolytic and kinetic characteristics of maize straw and the seaweed Ulva pertusa were studied and compared using heating rates of 10, 30 and 50°C min−1 under an inert atmosphere. The activation energy, and pre-exponential factors were calculated by the Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS) and Popescu methods. The kinetic mechanism was deduced by the Popescu method. The results indicate that there are three stages to the pyrolysis; dehydration, primary devolatilization and residual decomposition. There were significant differences in average activation energy, thermal stability, final residuals and reaction rates between the two materials. The primary devolatilization stage of U. pertusa can be described by the Avramic-Erofeev equation (n = 3), whereas that of maize straw can be described by the Mampel Power Law (n = 2). The average activation energy of maize straw and U. pertusa were 153.0 and 148.7 KJ mol−1, respectively. The pyrolysis process of U.pertusa would be easier than maize straw. And co-firing of the two biomass may be require less external heat input and improve process stability. There were minor kinetic compensation effects between the pre-exponential factors and the activation energy

Fe catalysis for lignocellulosic biomass conversion to fuels and materials via thermochemical processes

Recently, international research is aiming at developing gasification and pyrolysis processes for the cost-effective thermochemical conversion of non-food biomass to biofuels. Gasification produces a mixture of carbon monoxide and hydrogen, known as syngas. Pyrolysis produces a liquid bio-oil. Both syngas and bio-oil can be used directly or can be converted to clean fuels and other valuable chemicals. Catalysis is central to achieving this aim. This study presents results from lignocellulosic biomass pyrolysis, air and steam gasification in the presence of Fe. Noncatalytic and catalytic pyrolysis and gasification experiments were carried out at temperature range of T = 500-760 °C under an inert helium atmosphere for pyrolysis and at T = 750-1050 °C with air and steam as the gasification agents for gasification. The effect of temperature (°C), heating rate (°C/min), gasification medium (steam or air), air ratio (λ), steam to biomass ratio (S/B) as well as the catalytic effect of Fe naturally dispersed in the biomass char were studied. The influence of the iron traces originated from the native biomass and ending up in the char residue is mostly studied. Moreover, experiments were performed and results discussed of Fe residues utilization mixed with the bed material to act as catalyst for the conversion of biomass. The results of the performed study showed that olive kernel pyrolytic char is highly reactive comparing to cellulosic biomass char, due to its porous structure, increased surface area and ash content rich in metals. In combination, the presence of metals in olive kernel ash (especially Fe metal) can play an active catalytic role in tar cracking. Additional results have also shown that the addition of Fe residue as in bed catalyst for upgrading non edible residual biomass, favorises the production of H 2 rich gas (syngas) due to Fe pronounced catalytic activity. © 2012 Elsevier B.V

Investigation of agricultural and animal wastes in Greece and their allocation to potential application for energy production

Agricultural and animal wastes constitute a high proportion of biomass in Greece, and are able to play an important role towards the satisfaction of heat and/or energy and related material supply, with respect to the environmental protection targets. This paper describes pyrolysis, gasification and combustion, as a potential agricultural and animal waste exploitation method, and presents a comparison between those treatments when utilized as a source for renewable energy. The aim of the present work was to strengthen the interest in agricultural and animal waste potential for energy production in Greece, through a methodology for the feasibility of utilization of those kinds of wastes as renewable energy resources. A combination of technical, economic and environmental issues is presented here, and focus on the benefits that thermochemical conversion is able to offer, either in investigation or in future technological application for alternative exploitation methods of animal and agricultural wastes. © 2006 Elsevier Ltd. All rights reserved