Fractional condensation and aging of pyrolysis oil from softwood and organosolv lignin

Abstract

Softwood and organosolv lignin were pyrolized in a fluidized bed reactor. In each case, fractional condensation was achieved through two cyclonic condensers, maintained at different temperatures, and separated by an electrostatic precipitator. The produced oil was analyzed for liquid yield, water content, acidity, calorific value, carbon-hydrogen-nitrogen-oxygen content, viscosity, and rheology. To assess the effects of aging on the quality of the bio-oil, these tests were repeated after one-, two-, three- and nine- month intervals. The organosolv lignin is found to provide lower oil yields (30%) than softwood (50%). It is shown that higher carbon and lower oxygen content in the feedstock correlates to better bio-oil quality. Lignin, with a higher carbon and lower oxygen content than softwood, results in bio-oil with less water, lower acidity, higher heating values, and higher dynamic viscosities. Increasing the condensing temperature of the first condenser delays the condensation of water and light organics in the condensing train, affecting the properties of bio-oil, especially for the softwood. Tests on aging of the bio-oil demonstrate that viscosity is the only property significantly affected by the shelf life of the oil. Present data are favorably compared with available published data, for both feedstock types.