Strategies for Reduced Energy Use and Cost in Pulp and Paper Mills by Energy Integration of the Paper Drying Process

Kristian Lindell

Research output: ThesisDoctoral Thesis (compilation)

Abstract

The cost of energy for drying paper is substantial for the pulp and paper industry, and studies of various strategies for energy cost reductions such as increased energy efficiency, increased heat recovery from the exhaust drying air and reduced cost of the process heat are presented in this thesis. The energy use and cost studies were performed using a block-model based simulation tool developed for this specific purpose.

For a multicylinder drying-section, the heat recovery potential was shown to vary from 25 to 60%, based on total energy available in the exhaust air stream, as the dew point of the drying air was varied in the range of 45 to 70 °C. For minimum energy costs, the dryer should be operated at the highest dew point possible. Dryer-limited paper machines should, however, always be operated at the lowest exhaust air humidity possible since the revenue from the extra produced paper is much higher than the additional cost of energy.

The use of drying-sections including gas-fired paper dryers was shown to increase the heat recovery potential by up to 40%. However, due to the higher cost of natural gas and the reduced backpressure power generation with such drying-sections, the overall energy costs will be significantly higher. If black liquor gasification is implemented the produced syngas can be used as a substitute for the fossil natural gas. The process economics will improve significantly, especially if the gas is used to fire a combined cycle system and the exhaust gases from the gas turbine are used as make-up drying air in the impingement hood. At current energy price levels, in-house power generation based on biomass fuels is greatly favoured by the electricity certificate system, and the high power-to-heat ratio of the combined cycle system is thus favourable.

Differentiated pricing of secondary energy was shown to be a useful strategy for promoting the recovery and reuse of such energy, thus increasing the overall energy efficiency and reducing the energy costs for the pulp and paper mills.
Original languageEnglish
QualificationDoctor
Awarding Institution
  • Division of Chemical Engineering
Supervisors/Advisors
  • Stenström, Stig, Supervisor
Award date2007 Jan 26
Publisher
ISBN (Print)978-91-7422-141-1
Publication statusPublished - 2007

Bibliographical note

Defence details

Date: 2007-01-26
Time: 13:30
Place: Kemicentrum, Getingevägen 60, Lund, hörsal B.

External reviewer(s)

Name: Westermark, Mats
Title: Professor
Affiliation: Div. of Energy Processes, Dept. of Chemical Engineering and Technology, Royal Institute of Technolog

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<div class="article_info">Kristian Lindell and Stig Stenström. <span class="article_issue_date">2004</span>. <span class="article_title">Assessment of different paper drying processes to reduce the total energy costs from a mill perspective</span> <span class="journal_series_title">Proceedings of the 14th International Drying Symposium (IDS 2004), São Paulo, Brazil, 22-25 August 2004.</span>, <span class="journal_pages">pp 1233-1240</span>.</div>
<div class="article_info">Kristian Lindell and Stig Stenström. <span class="article_issue_date">2005</span>. <span class="article_title">A study of mill-wide energy use and costs for combined paper dryers with internal and external heat recovery</span> <span class="journal_series_title">Proceedings of the 3rd Nordic Drying Conference (NDC 2005), Karlstad, Sweden, 15-17 June 2005</span>, </div>
<div class="article_info">Kristian Lindell and Stig Stenström. <span class="article_issue_date">2006</span>. <span class="article_title">A modular process modelling tool for the analysis of energy use and cost in the pulp and paper industry</span> <span class="journal_series_title">Drying Technology</span>, <span class="journal_volume">vol 24</span> <span class="journal_pages">pp 1335-1345</span>. (inpress)</div>
<div class="article_info">Kristian Lindell and Stig Stenström. <span class="article_issue_date">2006</span>. <span class="article_title">Integration of black liquor gasification with a gas fired paper drying process</span> <span class="journal_series_title">Proceedings of the 15th International Drying Symposium (IDS 2006), Budapest, Hungary, 20-23 August 2006</span>, <span class="journal_pages">pp 931-938</span>.</div>
<div class="article_info">Kristian Lindell and Stig Stenström. <span class="article_issue_date"></span>. <span class="article_title">Energy pricing in the pulp and paper industry</span> <span class="journal_series_title">Nordic Pulp and Paper Research Journal</span>, (submitted)</div>

Subject classification (UKÄ)

  • Chemical Engineering

Free keywords

  • Paper
  • Pappers- och massateknik
  • pulp and paper technology
  • Wood
  • Energiforskning
  • Chemical technology and engineering
  • Kemiteknik och kemisk teknologi
  • Combined dryer
  • Energy research
  • Black liquor gasification
  • Heat recovery
  • Secondary energy
  • Co-generation
  • Costs
  • Energy
  • Drying

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