Process integration of near-neutral hemicellulose extraction in a Scandinavian kraft pulp mill - Consequences for the steam and Na/S balances
Journal article, 2011

While in a conventional kraft pulp mill, most of the hemicellulose and lignin fraction of the wood is burned in the recovery boiler to produce steam, in a biorefinery it can partially be used to produce added-value products. In this paper, the most important consequences of integrating a bioethanol production plant with a model pulp mill are presented in terms of steam and Na/S balances. The model mill represents an average Scandinavian hardwood kraft pulp mill, and the bioethanol plant is based on the "near-neutral" hemicellulose pre-extraction method. Regarding the steam balance, a comprehensive heat integration study is performed. Implementing hemicellulose extraction increases the net steam demand by 48 MW. However, process integration at the mill and the bioethanol plant individually leads to significant steam savings, and a corresponding net increase of steam by only 3 MW. Additional steam savings can be achieved if the total integration of the two processes (between the pulp mill and the bioethanol plant) is considered (3 MW), resulting in a biorefinery with no increase of steam demand. As regards the Na/S balance, it is shown that green liquor export from the mill to the bioethanol plant results in severe disruptions in the sodium and sulphur balance of the mill. Different attempts to solve this problem are discussed, but are very costly and/or negatively affect the water and steam balance of the mill.

oceedings

Process integration

pre-extraction

Near-neutral

recovery

p23

Pinch analysis

softwood

ethanol

biorefinery

Pulp mill

energy efficiency

opportunities

Hemicellulose extraction

separation

Hardwood

model

heat integration

Author

Valeria Lundberg

Industrial Energy Systems and Technologies

Erik Marcus Kristian Axelsson

Industrial Energy Systems and Technologies

Maryam Mahmoudkhani

Industrial Energy Systems and Technologies

Thore Berntsson

Industrial Energy Systems and Technologies

Applied Thermal Engineering

1359-4311 (ISSN)

Vol. 43 42-50

Subject Categories

Paper, Pulp and Fiber Technology

DOI

10.1016/j.applthermaleng.2012.03.037

More information

Created

10/7/2017