Analysis and comparison of biomass pyrolysis/gasification condensates: an interim report

Abstract

This report provides results of chemical and physical analysis of condensates from eleven biomass gasification and pyrolysis systems. The analyses were performed in order to provide more detailed data concerning these condensates for the different process research groups and to allow a determination of the differences in properties of the condensates as a function of reactor environment. The analyses were performed on condensate samples provided by the reactor operators and are considered representative of the operating conditions given but they are not necessarily representative of optimum operating conditions in the specific reactors.The samples were representative of the various reactor configurations being researched within the Department of Energy, -Biomass Thermochemi ca 1 Conversion program. The condensates included tar phases, aqueous phases and, in some cases, both phases depending on the output of the particular reactor system. The analyses included gross compositional analysis (elemental analysis, ash, moisture), physical characterization (pour point, viscosity, density, heat of combustion, distillation),_ specific chemical analysis (gas chromatography/mass spectrometry, infrared spectrophotometry, proton and carbon-13 nuclear magnetic resonance spectrometry) and biological activity (Ames assay).These results are from the first phase of a longer term program to determine the properties, handling requirements, and utility of the condensates recovered from biomass gasification and pyrolysis. The analytical data demonstrates the wide range of chemical composition of the organics recoven!d in the condensates and suggests a direct relationship between operating temperature and chemical composition of the condensates. A continuous pathway of thermal degradation of the tar components as a function of temperature is proposed. Variations in the chemical composition of the organic components in the tars are reflected in the physical properties of tars and phase stability in relation to water in the condensate. The biological activity appears to be limited to the tars produced at high tempera"':ures as a result of formation of polycyclic aromatic hydrocarbons in high concentrations. Future studies of the time/temperature relationship to tar composition and the effect of processing atmosphere should be undertaken. Further processing of the condensates either as wastewater treatment or upgrading of the organics to useful products is also recommended.

A review of the chemical and physical mechanisms of the storage stability of fast pyrolysis bio-oils

“…For example, extraneous contamination levels of 2270 ppm iron, 1950 ppm zinc, and 80 ppm lead were reported by Elliott (1986) to be in an early SERI (NREL) bio-oil, which had been produced using a galvanized scrubbing tower for condensate recovery. (This scrubber was taken out of service shortly after the analyses were made.)…”

Large-Scale Pyrolysis Oil Production: A Technology Assessment and Economic Analysis

“…This is the primary reason why bio-oils exhibit a pH in the range of 2.0-3.0. Table 2 lists the chemical properties of bio-oils produced from three different types of biomass: birch, pine, and poplar [26]. The birch and pine were produced at VTT in Finland using a circulating fluidized bed reactor while the poplar was produced in a vortex reactor at NREL.…”

“…Increasing the cracking severity (time/temperature relationship) is known to alter the chemical profile of the resulting oils. Elliot [26] described the relationship between compound classes and the temperature to which the vapors were exposed to before quenching. That relationship is described in the example shown below.…”

“…Because this is an important issue to the eventual commercialization of this technology, researchers began to investigate the health effects of bio-oil in the mid 1980s. Elliot [26] used the Ames test to look at the mutagenic activity of bio-oil as a function of the thermal severity of the process used to generate the oils. With the low temperature "primary" oils, produced in the range of 500° -600°C no mutagenic activity was observed.…”

Hot Gas Conditioning: Recent Progress with Larger-Scale Biomass Gasification Systems; Update and Summary of Recent Progress

“…Products formed at temperatures above approximately 800 °C or exposed to long residence times may also contain refractory polyaromatic products as explained above. Studies have shown (Elliott, 1985) that these refractory tars may contain materials that are classified as hazardous and will require a higher level of care in handling and disposal.…”