Black Liquor Gasification Characteristics. 1. Formation and Conversion of Carbon-Containing Product Gases

Abstract

Experimental measurements of the carbon-containing gases produced during gasification and pyrolysis of dry solids from two black liquors were made at high heating rates, at 700−1100 °C. The product gases were analyzed for carbon-containing species by Fourier transform infrared spectrometry. The 12 most abundant carbon-containing light product gases were quantified. Devolatilization of black liquor proceeded rapidly and was complete within the shortest sampling interval (0.3 s) in all of the laminar entrained-flow reactor experiments. Less than 15% of the carbon in the black liquor solids was converted to light gases during devolatilization. In a nitrogen atmosphere, additional carbonaceous material from tar was converted to light gases via secondary reactions after devolatilization was complete, and fixed carbon was gasified by reduction of Na2SO4 and Na2CO3. Neither the presence of water vapor nor the composition of the black liquor solids had a large effect on the transformation of organic matter to light gases during devolatilization. These parameters also had little impact on the evolution of light gases during secondary cracking and reforming reactions at low temperatures (700−800 °C). However, at higher temperatures (900−1100 °C), these variables had a greater impact. The water gas shift reaction apparently played a major role in the distribution of carbon between CO and CO2 during secondary reactions at longer residence times and higher reactor temperatures.