Pyrolysis technology is a widely utilized process in biomass energy production

and has potential to serve as an alternative for recovery of straw black liquor. A 10 kg·h-1 stirring type pyrolysis experimental apparatus was employed to prepare black liquor char (BLC) and fuel gas

aiming to analyze the differences of total alkali recovery and silicon distribution between BLC-leached and smelt-dissolved green liquor. The results showed that the total alkali in BLC-leached green liquor was equal to or a bit higher than that of smelt-dissolved green liquor. Around 30% to 40% of silicon retained in BLC-leached carbon powder as forms of insoluble silicates

which were mainly compound silicates of non-process elements such as Al

Ca

Fe and Mn. Because of the retention of a considerable part of silicon in leaching solid phase

the silicon concentration was lower in BLC-leached green liquor than that of smelt-dissolved green liquor

and the ratio of Na2CO3 to Na2SiO3 (or Na4SiO4) decreased to a large extent in the former green liquor compared to the latter. The findings indicate that chemical recovery using pyrolysis-leaching method is beneficial for decreasing the affects of silica problem especially improving the lime causticizing process.