Characteristics of Fuel Pellets Made by Mixing Paper Sludge and Forest Byproducts

Abstract

In this study, for reusing the sludge generated in a fine paper mill as fuel, the characteristics of the pellets prepared by mixing auxiliary raw materials such as pulp mill chip rejects, camellia oilseed cake, Sancho pruning remnants, and mulberry pruning remnants were evaluated. The pellet yield decreased as more sludge containing about 50% of the inorganic fillers was mixed with each auxiliary material, but the camellia oilseed cake, unlike the others, was of great help in improving the pellet yield. The Van Krevelen diagram showed that, as more sludge was added to the woody biomass in preparing the pellets, they tended to have a similar elemental composition to that of coal or lignite. The sludge addition to the woody biomass had a negative effect on the calorific value of the pellets, but the lower calorific value of 2400-3000 kcal/kg was acquired even when more than 50% of sludge was added. The sludge pellets containing the camellia oilseed cake had a faster ignition point than those mixed with the other woody biomass, but the flame duration was shorter. This study showed that the sludge from fine paper mills containing about 50% of cellulose fibers could be used to produce economical solid fuels if mixed with other woody biomass in an appropriate ratio.