Optimal Multi-Period Investment Analysis for Flexible Pulp Mill Utility Systems
Kapitel i bok, 2015

The techno-economic potential for new technologies in pulp mills is conventionally studied assuming annual averages, based on the assumption that the pulp mill is continuously operated at a constant production rate close to its design capacity. Recent work has shown, however, that a technology, such as lignin extraction, which can improve the operating flexibility of the pulp mill utility system, has a value associated with its flexibility that is not captured in such average-value models. These previous results indicated a risk of significant errors if heat load variations were not properly modelled. This paper presents a multi-period optimization model for the planning of design and operating decisions connected to pulp mill utility systems, which in this work has been extended with back-pressure and condensing turbine models. The model optimizes technology selection, equipment capacities and operating loads under the influence of demand variations, considering part-load efficiencies and operating load limits. Application of the model to an illustrative example showed that lignin extraction can compete with electricity production already at a lignin price of 22 €/MWh in the presence of variations due to poor off-design performance for the turbines. This demonstrates the usefulness of the proposed modelling approach.

Lignin extraction

Pulp mill

Utility system

Steam turbine



Elin Svensson

Chalmers, Energi och miljö, Industriella energisystem och tekniker

Computer Aided Chemical Engineering

1570-7946 (ISSN)

Vol. 37 1853-1858


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