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We developed a drop-tube reactor with a separation unit containing a quartz glass filter that is capable of fractionating alkali and alkaline earth metals (AAEMs) released as solid particle, vapor, and combined with water-soluble and water-insoluble tar. The ratio of released AAEMs in pulverized wood chips that had been steam-gasified was examined by changing the temperatures of the reactor and the separation unit independently. We found that approximately 63-80% of the released AAEMs were combined with tar. In addition, as the gasification temperature increased, the yields of the AAEMs combined with water-soluble and water-insoluble tars remained nearly constant, even though the amount of recovered water-soluble tar decreased as a result of secondary decomposition. This finding implies that AAEMs released by the secondary decomposition of watersoluble tar are fine particles that cannot be collected in a quartz glass filter. Additionally, yields of condensed AAEMs substantially increased as the gasification temperature increased, implying that the evolution of AAEMs from char was enhanced at high gasification temperatures. Evaluation of the water-soluble and water-insoluble tar using a Fourier transform infrared spectrometer (FTIR) and an elemental analyzer indicated that AAEMs likely combine with the OH groups of carboxylic acids and phenols in water-soluble tar. This finding infers that the AAEMs recovered from water-insoluble tar are present in aromatic compounds that are derivatives of benzene, xylene, furfural, and naphthalene in the product gas.

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The effect of coal char on the decomposition of rice straw derived tar was investigated in a two-stage fixed bed reactor. The reactor was divided into a pyrolysis zone (upper part) and a volatile-char contacting zone (lower part). Rice straw was pyrolysed at different temperatures in the upper part. Coal char, prepared by the pyrolysis of Indonesian coal at either 600°C (char600) or 800°C (char800), was located in the lower part. Volatiles from the rice straw (upper part) were produced and then came in contact with the coal char at the lower part under the N 2 (pyrolysis) or steam/N 2 (steam reforming) gas flow. Under pyrolysis, both char600 and char800 exhibited a catalytic effect on the thermal tar decomposition. The coal chars also played a significant catalytic activity on the decomposition of the heavy aromatic hydrocarbons that were generated at a high pyrolysis temperature. In the presence of steam, char600 also exhibited a catalytic role in tar steam reforming, while char800 did not reveal any such significant catalytic activity because of the predominant coke/carbon formation.

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