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Energy and emission implications of optimized white liquor causticity, TAPPI Journal January 2026

ABSTRACT: Optimizing the causticizing plant offers significant opportunities for energy and emissions savings in kraft mills by minimizing the chemical and water deadload introduced into the recovery cycle via white liquor. Modern control strategies utilize both feedforward and feedback loops to manage causticity, enabling more aggressive targets closer to equilibrium levels. This paper evaluates the benefits of optimizing white liquor chemistry through a detailed CADSIM Plus simulation model, replicating the chemistry of a Canadian bleached kraft mill that adopted an automated causticizing control system. The control system increased causticity from 77.0% to 82.3% at a fixed total titratable alkali (TTA) of 126.5 grams of sodium dioxide per liter (gNa2O/L). Modeling this chemistry change indicated a 1.5 metric tons per hour (t/hr) reduction in evaporator steam demand and a 2.8% increase in black liquor higher heating value. Consequently, the improved heating value resulted in a 1.5% rise in recovery boiler steam production and a 5.3% reduction in biomass energy consumption in power boilers, leading to a 4.8% decrease in biogenic carbon dioxide (CO2) emissions. Additionally, reducing the inorganic and water deadload throughout the recovery cycle may support higher as-fired dry solids targets, enhancing recovery boiler energy efficiency by lowering the water evaporation requirement during black liquor combustion. However, implementing a causticizing control system requires careful assessment of potential lime kiln bottlenecks, as increased causticity demands may affect kiln operations depending on broader mill conditions. Overall, an automated causticizing control system enhances process efficiency, reduces energy consumption and emissions, and positions kraft mills for improved productivity and longterm sustainability.

Barrier Properties of Lab and Semi-pilot Coatings with Different CNF Formulations, TAPPICon25

Conical vs Double Disk Refining Technology Evaluations and the Effects on Energy Consumption and Physical Paper Properties of High Yield Southern Softwood, TAPPICon25

ENHANCING TISSUE WET PRESSING PERFORMANCE AND DRY END MATERIAL EFFICIENCY FOR COST SAVINGS, TAPPICon25

Process Evaluation for Sustainability Using TAPPI TIP 0404-63, TAPPICon25

Developing and Using Modeling to Understand and Improve Industrial Oxygen Delignification Processes, TAPPICon25

Water-barrier coating based on lignin oil found on the principle of an O/W Pickering emulsion stabilized by different nanocelluloses together with or without pectin, TAPPICon25

Techno-economic analysis of hydrothermal carbonization of pulp mill biosludge, TAPPI Journal March 2023

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

Colloidal Properties of Dissolved Kraft Lignin, 1992 Papermakers Conference Proceedings

Colloidal Properties of Dissolved Kraft Lignin, 1992 Papermakers Conference Proceedings

New Regulations and Their Affect on High Availability Monito

New Regulations and Their Affect on High Availability Monitoring and Control Systems, 1995 Process Control, Electrical & Information Conference Proceedings