+46 (0)31 763 26 00 info@acosense.com

Recovery Boiler

Recovery boiler

The overall goal of the project is to analyse the black liquor with respect to its combustion properties. One part is to analyse the black liquor as such but also entire sections of the evaporation process and the combustion of the black liquor in the recovery boiler as such. Doing so, a deeper understanding of the process can be achieved, compared to analysing the classical properties of the black liquor, and also “hidden” properties and process stages can be mapped. As a result, unwanted process stages can be avoided and operators can map, foresee and remain in favourable process stages.

The project is carried out together with Nordic Paper Bäckhammar.

When producing kraft pulp, black liquor is produced as a by-product. The black liquor contains process chemicals and to recover these the black liquor is burned in the recovery boiler. Black liquor is a complex fuel and the properties can vary greatly. The fluid is also a fantastic possible raw material for future biofuels and materials.

Large scale processing of black liquor is seen as a key activity in moving towards a fossil free future, but this solution is also held back due to the risk to increase problems in the recovery cycle with potential downtime and production loss as consequence. This is already today a problem for pulp mill. The change in black liquor properties are with present technology hard or sometimes even impossible to detect and can vary with both raw material and production.  This leads to mills being very careful with inducing process changes like extracting lignin from black liquor that can increase disturbances.

Acosense have together with Nordic Paper Bäckhammar investigated the possibilities to analyse black liquor on a deeper level than for example just specific properties like for instance dry substance content. 

A main target for the project is to design a digital tool that can be used during recovery boiler operation to handle these variations effectively and make the operation easier and traceable and also making the transition into utilizing the black liquor for biofuels and materials possible.

A previous project by Acosense and Nordic Paper Bäckhammar has shown that it is possible to analyse the black liquor inlet to the recovery boiler (droplet formation) and to get digital fingerprints for different process states in the form of frequency spectrums. Work is ongoing to develop an intuitive user interface for process operators for fast decision support in the control room based on these black liquor fingerprints.

With the use of machine learning one want to derive suggestions for operating settings for optimum operation based on the different process states that are identified based on the black liquor finger prints. In this it is also included to analyse the recovery boiler operating parameters, image-based technology for combustion analysis to derive a tool that visualizes a digital fingerprint of the black liquor properties for effective and structured handling of process variations in the recovery cycle. 

Contakt person
Pia Holmblad, pia.holmblad@acosense.com, +46 31 763 26 13

Acosense optimises the processing industry by literalilly listening to it. By applying Active Acoustic Spectroscopy a new level of understanding can be reached. Not only fluid properties can be analysed but entire process sections can be understood and superviced. 


Acosense AB
Stampgatan 20A
411 01 Göteborg
+46 (0)31 763 26 00