Combustion Properties of Mixed Black Liquor Solids from Linter and Reed Pulping

In order to find the suitable alkali recovery process for linter and reed pulping discharges, the physicochemical properties of the black liquor solids from linters pulping and black liquor solids from reed pulping were analyzed. The swelling volume index, calorific value, and pyrolysis characteristics of five samples of mixed black liquor solids were tested. The kinetics of the combustion process of the samples were further studied. The results showed that the calorific value and swelling index of the reed black liquor was higher and its inorganic content was lower. During the combustion period, the droplet undergoes four stages; drying, devolatilisation or pyrolysis, char burning, and smelt reaction. With the increase of reed pulping black liquor solids in the sample, the activation energy decreased, while the frequency factors increased. As a result, the combustion performance of the mixed solids was significantly improved.