Experimental study of co-pyrolysis of polyethylene/sawdust mixtures

A study of the behavior of the thermal decomposition of mixtures of biomass and thermoplastics, such as polyethylene, is of interest for processes for the thermal recovery of industrial and urban wastes such as pyrolysis or gasification. No solid residue is formed during the thermal degradation of pure polyethylene. However, the addition of biomass, which generates char can vary the product distribution and increase the heating value of the gas obtained. A study of the thermal degradation of pine sawdust, polyethylene and mixtures of polyethylene and pine sawdust has been carried out in a fluidized bed reactor. Experiments were carried out at five different temperatures: 640, 685, 730, 780, and 850 ºC. The yields and composition of the derived oil, wax, and gas were determined. The addition of polyethylene increases the gas production and decreases the production of waxes and liquids for the different temperatures tested. The main gases produced from the co-pyrolysis process were, at low temperatures, carbon monoxide ethylene, carbon dioxide, propylene, butadiene, methane and pentadiene while at high temperatures the gas composition changed drastically, the main components being carbon monoxide (more than 33 wt.%), ethylene, methane benzene and hydrogen. The analysis of the liquid fraction shows a decrease of the concentration of oxygenated and aliphatic compounds

EXPERIMENTAL STUDY OF CO-PYROLYSIS OF POLYETHYLENE/SAWDUST MIXTURES by

A study of the behavior of the thermal decomposition of mixtures of biomass and thermoplastics, such as polyethylene, is of interest for processes for the thermal recovery of industrial and urban wastes such as pyrolysis or gasification. No solid residue is formed during the thermal degradation of pure polyethylene. However, the addition of biomass,which generates char, can vary the product distribution and increase the heating value of the gas obtained. A study of the thermal degradation of pine sawdust, polyethylene and mixtures of polyethylene and pine sawdust has been carried out in a fluidised bed reactor. Experiments were carried out at five differen

Yields and ageing of the liquids obtained by slow pyrolysis of sorghum, switchgrass and corn stalks

A laboratory scale reactor has been set up to pyrolyse different kinds of biomass under slow heating rates and a range of peak temperatures. Yields of solid and liquid products (i.e. char and oil) were measured allowing the effects of temperature and biomass feedstock to be determined. Small differences in char and oil yields were found between the three biomass feedstocks. Pyrolysis oil samples were collected and characterised with size exclusion chromatography (SEC), ultra violet fluorescence (UV-F) and infra red (IR) spectroscopies to study their structural changes as a function of time after collection, i.e. to assess the ageing of the bio-oils. The effects of several variables on the stability of product liquids were examined: e.g. pyrolysis temperature, storage temperature, solvent addition, type of biomass feedstock. Rapid structural changes in the oil samples were found to occur within about 48 h of preparation. Ageing of oils is thought to be caused by polymerisation reactions taking place in the product liquids. The positive effects on the oil stabilisation due to low storage temperatures (5 C) and the addition of a solvent (methanol or acetone) were confirmed. However, in order to stop the ageing process completely, the concentration of these solvents in the final pyrolysis oil-solvent mixture needed to be greater than 25% (w/w). At lower solvent concentrations bio-oil ageing was slowed down but could not be suppressed altogether. © 2013 Elsevier B.V. All rights reserved

Structural Properties and Molecular Mass Distributions of Biomass-Coal Cogasification Tars as a Function of Aging

This work describes an analytical approach to determine changes in mass distributions and structural properties of biomass/coal co-gasification tars, after storage of these samples as a function of temperature, time and presence of ambient light. The samples examined were tars recovered during the co-gasification of pine and a sub bituminous coal (70:30 wt%). It is shown that the approach used was able to reveal even subtle differences in the tar, which occurred during its ageing under different storage conditions. Precipitation was observed to occur in the tars after 5 °C, and in the presence of ambient light. Size exclusion chromatography and laser desorption mass spectrometry revealed the presence of molecular masses from 2000 u in the tars. UV-fluorescence spectroscopy provided information on extents of (aromatic) conjugation, providing evidence of sizes of fused-aromatic systems in these tars up to at least 8 rings. The study revealed that the molecules that contained the largest conjugated aromatic ring systems, rather than the molecules with the greatest masses, were primarily involved in the ageing reactions, resulting in precipitation occurring. Different ageing mechanisms were identified depending on whether the tar was stored cold (5°C) in the dark, at room temperature in the dark or in presence of ambient light.JRC.F.2-Cleaner energ

Advanced Methods for Determining Mass Distributions and Structural Properties of Tars from the Gasification of Biomass and Coal - Beyond the Range of GC-MS

The influence of storage conditions were examined for a tar sample recovered during the co-gasification of pine and a Polish black coal. Detailed information regarding molecular mass distribution and average mass estimates were measured by size exclusion chromatography and laser desorption mass spectrometry. These techniques revealed the presence of molecules with masses from 2000 u in these tars. UV-fluorescence spectroscopy provided information on extents of (aromatic) conjugation. Different reactions mechanisms were observed depending whether the tar was stored cold (5°C) or at room temperature.JRC.F.2-Cleaner energ

The Effect of Ionic Liquid Cation and Anion Combinations on the Macromolecular Structure of Lignins

Imidazolium based ionic liquids (ILs) composed of anions such as chloride, acetate and alkyl phosphate have come to be considered as effective non-derivatizing solvents for cellulose, lignin and lignocellulosic biomass. After dissolution and thermal treatment of three technical lignins (organosolv, alkali and alkali low sulphonate) with an array of ILs, it was shown that these solvents behave as either reactants or catalysts, significantly reducing the molecular mass of these macromolecules and altering their structure. The degree of lignin structural modification is shown to be primarily influenced by the anion. Lignin fragmentation mechanisms were defined and a fragmentation hierarchy of the lignin macromolecule as a function of the IL anion was established. It was determined that sulfates > lactate > acetate > chlorides > phosphates in terms of the relative impact on reducing lignin molecular weight, with evidence of different anions causing cleavage of different linkages within the lignin. Of the ILs studied, sulfate based ionic liquids most comprehensively broke down the largest lignin molecules, resulting in fragments >1000–3000 u (by polysaccharide calibration). The lactate anion, while appearing less capable of breaking down the largest lignin molecules, causes the formation of significant quantities of the smallest sized fragments observed (2000–500 u). The new lower molecular mass species formed from the organosolv lignin are shown to have a more highly conjugated structure than their parent molecules, while a reduction in conjugation was observed in the alkali lignins. Using size exclusion chromatography coupled with UV detection, at least 40% of the original large-lignin molecules, from each of the lignins studied, were observed to remained intact. We hypothesize that fragmentation is effected either via catalytic means or through nucleophilic attack of inter-lignin β-O-bonds.JRC.F.2-Cleaner energ

The effect of ionic liquid cation and anion combinations on the macromolecular structure of lignins

Imidazolium based ionic liquids (ILs) composed of anions such as chloride, acetate and alkyl phosphate have come to be considered as effective non-derivatizing solvents for cellulose, lignin and lignocellulosic biomass. After dissolution and thermal treatment of three technical lignins (organosolv, alkali and alkali low sulphonate) with an array of ILs, it was shown that these solvents behave as either reactants or catalysts, significantly reducing the molecular mass of these macromolecules and altering their structure. The degree of lignin structural modification is shown to be primarily influenced by the anion. Lignin fragmentation mechanisms were defined and a fragmentation hierarchy of the lignin macromolecule as a function of the IL anion was established. It was determined that sulfates > lactate > acetate > chlorides > phosphates in terms of the relative impact on reducing lignin molecular weight, with evidence of different anions causing cleavage of different linkages within the lignin. Of the ILs studied, sulfate based ionic liquids most comprehensively broke down the largest lignin molecules, resulting in fragments >1000-3000 u (by polysaccharide calibration). The lactate anion, while appearing less capable of breaking down the largest lignin molecules, causes the formation of significant quantities of the smallest sized fragments observed (2000-500 u). The new lower molecular mass species formed from the organosolv lignin are shown to have a more highly conjugated structure than their parent molecules, while a reduction in conjugation was observed in the alkali lignins. Using size exclusion chromatography coupled with UV detection, at least 40% of the original large-lignin molecules, from each of the lignins studied, were observed to remained intact. We hypothesize that fragmentation is effected either via catalytic means or through nucleophilic attack of inter-lignin β-O-bonds

Structural Properties and Molecular Mass Distributions of Biomass-Coal Cogasification Tars as a Function of Aging

This work describes an analytical approach to determine changes in mass distributions and structural properties of biomass/coal cogasification tars, after storage of these samples as a function of temperature, time, and presence of ambient light. The samples examined were tars recovered during cogasification of pine and a sub-bituminous coal (70:30 wt %). It is shown that the approach used was able to reveal even subtle differences in the tar, which occurred during its aging under different storage conditions. Precipitation was observed to occur in the tars after <14 h of storage at >5 °C. Size exclusion chromatography and laser desorption mass spectrometry revealed the presence of molecular masses from <200 atomic mass unit (u) to >2000 u in the tars. UV-fluorescence spectroscopy provided information on extents of conjugation, providing evidence of sizes of conjugated aromatic systems in these tars up to at least 8 rings. The study revealed that the molecules that contained the largest conjugated aromatic systems, rather than the molecules with the greatest masses, were primarily involved in the aging reactions that resulted in precipitation occurring. Different aging mechanisms were identified, depending on whether the tar was stored in darkness or in the presence of ambient light