Fuel conversion characteristics of black liquor and pyrolysis oil mixture for efficient gasification with inherent catalyst

Abstract

This paper describes the technical feasibility of a catalytic co-gasification process using a mixture of black liquor (BL) and pyrolysis oil (PO). A technical concern is if gasifiers can be operated at low temperature (~1000 ºC) without problems of tar, soot or char, as is the case for pure BL due to the catalytic effect of fuel alkali. Hence, we investigated fuel conversion characteristics of BL/PO mixture: conversion of single droplet in flame, and char gasification reactivity. 20wt.% (BP20) and 30wt.% (BP30) were selected for weight fraction of PO because of lignin precipitation in BP30. Single droplet was devolatilized and gasified in a methane flame with a flat flame burner at various droplet sizes. Conversion time and swelling ratio were investigated with imaging. They were more sensitive to initial droplet size and reaction atmosphere than the mixing of BL and PO. Char gasification reactivity was measured in an isothermal thermogravimeter (iTG) at T=880–940 ºC and PCO2=1 bar. Both BP20 and BP30 showed complete char conversion and there was no statistically significant difference in char reactivity among BP20, BP30 and BL. These results show that PO can be co-gasified in BL gasification process without major changes in the operation.Godkänd; 2014; 20140830 (umeken