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A combined terminal location and ship routing problem
Linköping University, Department of Mathematics, Optimization . Linköping University, The Institute of Technology.
Linköping University, Department of Mathematics, Optimization . Linköping University, The Institute of Technology.
Södra Cell AB, Växjö, Sweden.
2006 (English)In: Journal of the Operational Research Society, ISSN 0160-5682, Vol. 57, no 8, 928-938 p.Article in journal (Refereed) Published
Abstract [en]

In this paper, we consider a combined terminal location and ship routing problem at Södra Cell AB. The purpose is to supply the customers' annual demand for pulp products while minimizing the distribution costs. Customers are supplied with various pulp products from pulp mills in Scandinavia by ships, trains, or lorries. The ship routes go from the pulp mills to terminals in Europe. From each terminal, the products are transported to customers by lorry, train, or barge. Some customers can be supplied directly from the pulp mills by trains or lorries. We have developed a mathematical model to select which terminals to use and, at the same time, determine the shipping routes. The mixed integer programming model was solved directly using a commercial solver. When the number of routes generated is large, the time required to obtain an optimal solution is too long. Hence, we have developed heuristics in order to obtain an acceptable solution in reasonable time. In addition to the basic case, five different scenarios were tested. Our heuristics provide solutions that are within 0.12% of the optimal ones.

Place, publisher, year, edition, pages
2006. Vol. 57, no 8, 928-938 p.
Keyword [en]
mixed integer programming, facility location, transportation, ship routing
National Category
Mathematics
Identifiers
URN: urn:nbn:se:liu:diva-14462DOI: 10.1057/palgrave.jors.2602057OAI: oai:DiVA.org:liu-14462DiVA: diva2:23546
Available from: 2007-05-14 Created: 2007-05-14 Last updated: 2013-11-07
In thesis
1. Supply chain optimization in the forest industry
Open this publication in new window or tab >>Supply chain optimization in the forest industry
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The scope of this thesis is modelling and solving large-scale planning problems in the supply chain within the forest industry. Five research papers are included, the first three of which focus on the modelling, and the last two on the solution methods. All problems included are tactical multi-commodity problems expressed as mixed integer programming (MIP) models. The work has been done in collaboration with two Swedish companies within the forest industry.

In Paper I, a problem concerning the supply chain of forest fuel for Sydved Energileveranser AB is modelled and solved. We study the problem of deciding when and where forest residues are to be converted into wood chips, and how the residues and chips are to be transported and stored in order to satisfy energy demand at heating plants. The company has long-term contracts with forest owners and saw mills. Decisions in the model include whether or not additional harvest areas and saw mills are to be contracted and which terminals to use. The planning horizon is one year and monthly time periods are used.

Papers II--V are based on planning problems at Södra Cell AB. The planning horizon is normally one year. Papers II--III consider only one time period. In Paper II the supply chain from pulp mills to customers is modelled and the combined problem of deciding terminal locations and which ship routes to use is studied. Shipping vessels chartered on short or long term are used to transport products to terminals in Europe. From each terminal, the products are transported to customers by truck, train, or a combination of both. In addition, trains and trucks can be used for transports directly to customers from mills. In Paper III the entire supply chain, from harvest areas to customers, is considered. Decisions included are transportation of raw materials, production mix, the distribution of pulp products, and the selection of potential orders and their quantities at customers. The ship routes are considered as flow links.

In Papers IV--V the problems in Papers II--III are combined into one model and several time periods are used. Lagrangian heuristics based on Lagrangian decomposition are used as solution methods in both papers. In Paper IV, the approach leads to subproblems for each time period, whereas in Paper V, another approach that results in subproblems for different parts of the supply chain is developed.

All models are based on real data from the companies. The models are detailed and describe the problems accurately. The solution methods are developed such that the solution time is kept within practical limits. Results from Papers II--III have been used by Södra Cell AB to support the change of the terminal structure as well as in budget planning.

Abstract [sv]

Denna avhandling presenterar matematiska modeller och lösningsmetoder för optimering av olika logistikproblem inom skogsindustrin. Vi studerar försörjningskedjor för skogsbränsle och massaproduker, och beaktar den årliga planeringen i syfte att optimera flödet.

Det första problemet behandlar skogsbränsle och är ett samarbete med Sydved Energileveranser AB. Råmaterial i form av grenar och toppar från avverkningsplatser ska flisas och transporteras till värmeverk, eventuellt via terminaler. Det finns möjlighet att flisa både i skogen och på terminaler. Biprodukter från sågverk kan också användas som råmaterial. Vid behov kan utbudet av råmaterial utökas genom att fler avverkningsplatser och sågverk kontrakteras. Värmeverken har en efterfrågan, angiven i kWh per månad, som ska uppfyllas. Exempel på beslut som ska tas är var flisning ska ske, om nya avverkningsplatser ska kontrakteras, var lagring ska ske, samt hur och när skogsbränslet ska transporteras.

Nästföljande problem behandlar massaprodukter och är ett samarbete med Södra Cell AB. Olika sorters massaved från skogen och biprodukter från sågverk utgör råmaterial för produktion av massaprodukter. Råmaterialet transporteras till massabruk för tillverkning enligt specificerade recept. De färdiga produkterna transporteras sedan med fartyg till terminaler i Europa. Från terminalerna transporteras produkterna vidare till pappersbruk, vilka är företagets slutkunder. Massaprodukterna transporteras i vissa fall med lastbil eller tåg direkt från massabruken till kunderna. Efterfrågan är angiven inom vissa gränser i olika order. Vissa order är fasta, vilket innebär att dess efterfrågan måste uppfyllas, medan andra order är fria. Exempel på beslut som ska tas är vilka bruk olika produkter ska produceras på, hur många och vilka terminaler som ska användas, samt hur transporterna ska utföras för att ge bästa resultat.

Utifrån ovanstående beskrivningar har matematiska modeller formulerats. Ge-nom att lösa dessa kan vi få svar på logistik- och transportfrågorna och ett optimalt flöde kan hittas. För att lösa modellerna har kommersiell programvara använts. Heuristiker och mer avancerade optimeringsmetoder har också utvecklats i syfte att producera bra lösningar snabbare.

Place, publisher, year, edition, pages
Matematiska institutionen, 2007
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1105
Keyword
Supply chain, logistics, forestry, optimization, modelling, transportation, mixed integer programming models, försörjningskedjor, logistik, optimering, modellering, transportplanering, blandade heltalsproblem, skogsindustrin
National Category
Computational Mathematics
Identifiers
urn:nbn:se:liu:diva-8856 (URN)978-91-85831-85-2 (ISBN)
Public defence
2007-06-01, C3, C-huset, Linköpings universitet, Linköping, 10:15 (English)
Opponent
Supervisors
Note
Article 4 was a manuscript entitled "Solving a multi-period supply chain problem for a pulp industry using Lagrangian heuristics based on time periods" at the time of the thesis defence. Available from: 2007-05-14 Created: 2007-05-14 Last updated: 2009-04-28
2. Optimization approaches to tactical planning problems in the forest industry
Open this publication in new window or tab >>Optimization approaches to tactical planning problems in the forest industry
2004 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

By using decision support tools based on operations research (OR) and optimization in the supply chain in the forest industry, the planning process can be improved and higher profitability can be obtained. The focus of this thesis is on modelling two real-life problems. The problems are united by the facts that they concern tactical (annual) planning in the forest industry, and that the models are developed and tested with real data at Swedish companies.

In the first paper, a problem of the supply chain of forest fuel is modelled and solved. The problem of deciding when and where forest residues are to be converted into forest fuel, and how the residues are to be t ransported and stored in order to satisfy demand at heating plants is studied. Decisions also include whether or not additional harvest areas and saw-mills are to be contracted. In addition, we consider the flow of products from saw-mills and import harbours, and address the question about which terminals to use. The planning horizon is one year and monthly time periods are considered. The test data is from Sydved Energileveranser AB.

The second paper is a case study from Södra Cell AB. A combined problem of terminal location and ship routing is studied. The objective is to minimize the costs of distributing pulp products from pulp mills to customers (paper mills). Shipping vessels chartered on short or long term are used to transport products to terminals in Europe. In addition, trains and lorries are used for direct transports to customers from mills. From each terminal, the products are transported to customers by lorry, train, or a combination of both. Decisions about which terminals to use, which shipping routes to use, and which other transportation possibilities to use are included.

In both problems, relatively large mixed integer programming (MIP) models have been developed and solved using a commercial lp (linear programming) solver. Heuristics have also been developed in both problems in order to obtain faster solutions. Several scenarios of the problems have been tested and evaluated.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet, 2004. 17 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1071
National Category
Mathematics
Identifiers
urn:nbn:se:liu:diva-32396 (URN)18296 (Local ID)91-7373-893-X (ISBN)18296 (Archive number)18296 (OAI)
Presentation
2004-02-11, Glashuset, Hus B, Linköpings Universitet, Linköping, 10:15 (Swedish)
Opponent
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2013-11-07

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Gunnarsson (Lidestam), HeleneRönnqvist, Mikael

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