Impact of process changes on heat transfer and scaling rates in kraft black liquor evaporators

Scaling in evaporators is a major problem for chemical recycling in kraft pulp mills. For many mills disruptions in evaporation are a dominant cause of production losses and reduction of the plant energy efficiency and availability, aspects of fundamental importance for future biorefineries. By understanding how different operating conditions and process changes affect the performance of the evaporation plant, we will develop strategies for controlling the scaling rate and maintaining a high plant efficiency, and consequently to reduce the risk of sudden production losses.

The project will conduct experiments at world-unique pilot evaporator and utilize state-of-the-art numerical simulations to achieve this goal. The heat transfer and scaling rates dependence on temperature, dry solids and salt content will be experimentally investigated. A numerical framework for simulating crystallization in liquid films under industrially relevant conditions will be established to provide explanations for experimental observations on crystallization on the heat transfer surfaces. The project will provide clear recommendations and measures for the industry on predicting and avoiding scaling in black liquid evaporators.

Project partners:

Chalmers Tekniska högskola, Billerud, Holmen, RISE, SCA, Södra Skogsägarna, Valmet




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