Techno-economic analysis of hydrothermal carbonization of pulp mill biosludge

For many mills, the biosludge from wastewater treatment is difficult to recycle or dispose of. This makes it a challenging side stream and an important issue for chemical pulping. It often ends up being burned in recovery biomass boiler, although moisture non-process element (NPE) contents make problematic fuel. Biosludge has proven resistant attempts reduce its moisture. When incinerated heat dry matter combustion insufficient yield positive net heat. Mixing sludge with black liquor evaporator plant incineration boiler more energy efficient, but still additional load on plant, as well introducing NPEs liquor. In this study, treating by hydrothermal carbonization (HTC), mild thermochemical conversion technology, investigated. The HTC process some notable advantages treatment; taking place water, suited sludge, hydrochar product much easier dewater than untreated sludge. two designs are simulated using IPSEpro simulation software, followed economic analysis. Low temperature levels used minimize investment costs steam consumption. results show that if payback periods could be short at likely electricity prices. before mixing profitable only freed capacity can increase firing solids content.