Routing and tank allocation for a chemical tanker

155 Pages·2015·4.19 MB·English

Routing and tank allocation for a
chemical tanker
Mari Jevne Arnesen
Magnhild Gjestvang
Industrial Economics and Technology Management
Submission date: June 2015
Supervisor: Kjetil Fagerholt, IØT
Co-supervisor: Kristian Thun, IØT
Norwegian University of Science and Technology
Department of Industrial Economics and Technology Management

Description of the thesis
The purpose of the thesis is to model port operations done by a chemical tanker, with the
objective of finding optimal routes in a port. The problem is considering one specific ship
delivering and picking up cargoes in a port, complying with restrictions regarding time
windows and draft limits. Cargo handling and stowage requirements are of particular
relevance for a chemical shipping company, and are also included.
The following topics will be studied:
A tanker routing problem modeled as a pickup and delivery problem including time
•
windows and draft limits, solved both as a MIP implemented in Xpress Mosel and
by using a dynamic programming algorithm implemented in Java.
A pickup and delivery problem including time windows, draft limits, and tank
•
allocation, solved both exactly and by using a heuristic.
Testing and discussion of results from generated test instances.
•
An evaluation of the models and solution methods developed.
•
i
ii
Preface
This master thesis is the final result of the work for our Master in Science in Industrial
Economics and Technology Management, with specialization in Managerial Economics
and Operations Research. The thesis is a continuation of our work for the project thesis,
done in the fall semester 2014.
The purpose of the thesis has been to model port operations done by a chemical tanker,
with the objective of finding optimal routes in a port. This master thesis is a part of
the GREENSHIPRISK project, which is a collaboration between Odfjell, Western Bulk,
MARINTEK, Norwegian School of Economics, and Norwegian University of Science and
Technology.
We would like to thank our supervisor Professor Kjetil Fagerholt for his insights and help-
ful guidance. We would also like to express our gratitude to our co-supervisor, Kristian
Thun, for his support and feedback, especially in the phase of developing the Java-code
used in this thesis, as we had no knowledge with Java as a programming language. At
last, we would like to thank our contact in the case company, Klaus Walderhaug, for his
contribution of real case data and valuable input on shipping related issues.
Trondheim, June 5, 2015
Mari Jevne Arnesen Magnhild Gjestvang
iii
iv
Abstract
This thesis considers a chemical tanker arriving a port with several terminals where
customers are to be served. The customers have both pickup and delivery requirements,
and the intention is to find a feasible route for serving the customers such that the total
time used in port is minimized. Chemical tankers carry chemicals in compartments, and
the routing decision is complicated when these chemicals need to be allocated to specific
tanks. Draft limits at the terminals and time windows for when the cargoes can be served
will also influence the terminal sequence the ship can follow.
A literature study examining problems with similar characteristics is presented. There
hasbeendonerelativelylittleresearchonshiproutingandschedulingcomparedtovehicle
routing, and this thesis contributes to the literature by studying a pickup and delivery
problem with time windows and draft limits. This has never previously been explicitly
studied. Also including tank allocation to the problem is an additional contribution to
literature, as the allocation of cargoes to tanks is an important planning problem for
chemical shipping companies.
Two models are developed, one without and one with tank allocation. The models are
solved with two different solution methods. The model without tank allocation is solved
exactly by direct implementation in a commercial mixed integer programming solver
(MIP-solver), and by using a dynamic programming algorithm. The model with tank
allocation is solved exactly with a MIP-solver and by using a heuristic. The heuristic
consists of a dynamic programming algorithm to find ship routes and a MIP-solver to
find feasible tank allocations. The computational study in this thesis includes testing of
the two models using both solution methods for instances of different sizes, and analyses
of the models and solution methods.
The results from the computational study show that when the problem without tank
allocation is solved using a MIP-solver, only small instances are solved in a short time.
v
The results from the computational study show that the MIP-solver is able to solve the
problem without tank allocation in a short time only when instances of small sizes are
considered. The run times increase drastically when the number of cargoes increases or
tankallocationis included. The dynamic programming algorithmandthe heuristic shows
promising results when solving the models without and with tank allocation, respectively.
Bothsolutionmethodsareabletosolvetheproblemsforinstancesofrealisticsizes. These
solution methods are therefore considered suitable to be a part of a tool used for decision
support for chemical shipping companies.
vi
Sammendrag
Denne avhandlingen betrakter en kjemikalietanker som ankommer en havn med flere
terminaler hvor kunder skal betjenes. Skipet skal enten hente eller levere laster hos de
ulike kundene, og hensikten med problemet er å finne en mulig rute slik at den totale
tiden som brukes i havnen er minimert. Kjemikalietankere oppbevarer lastene i tanker, og
allokeringen som må gjøres når laster skal tilordnes tanker kompliserer ruteplanleggingen.
Dypgangsrestriksjonerforterminaleneogtidsvinduerfornårlastenekanbetjeneskanogså
påvirke ruten skipet kan seile.
I avhandlingen presenteres en litteraturstudie hvor problemer med lignende egenskaper
har blitt undersøkt. I forhold til klassisk ruteplanlegging har det blitt gjort relativt lite
forskningspesifiktpåmaritimruteplanlegging. Denneavhandlingenbidrartillitteraturen
ved å studere et pickup and delivery-problem med tidsvinduer og dypgangsrestriksjoner.
Detteproblemetharikkeblittstuderteksplisittfør. Åinkluderetankallokeringimodellen
er et ekstra bidrag til litteraturen, da dette er et viktig planleggingsproblem for rederier
med kjemikalietankere.
To matematiske modeller har blitt utviklet; en med og en uten tankallokering. Modellene
er løst med to ulike løsningsmetoder. Modellen uten tankallokering er løst ved direkte
implementeringienkommersiellproblemløserforblandedeheltallsmodeller(MIP-solver),
og ved bruk av en dynamisk programmeringsalgoritme. Begge disse løsningsmetodene er
eksakte. Modellen med tankallokering er løst eksakt ved bruk av en MIP-solver og ved
bruk av en heuristikk. Heuristikken bruker en dynamisk programmeringsalgoritme til å
finne mulige skipsruter for så å bruke en MIP-solver til å løse tankallokeringsproblemet.
Beregningsstudiet i denne avhandlingen omfatter testing av de to modellene med de ulike
løsningsmetodene. Testingen er gjort på instanser av forskjellige størrelser for å analysere
hvordan løsningsmetodene fungerer.
Resultatene i beregningsstudiet viser at løsningsmetoden som innebærer å bruke en MIP-
solver kan løse problemet uten tankallokering raskt kun for små instanser. Kjøretidene
vii
øker drastisk når antallet laster i instansene øker, eller når tankallokering inkluderes i
problemet. Løsningsmetodene som bruker den dynamiske programmeringsalgoritmen og
heuristikken for å løse henholdsvis problemene uten og med tankallokering viser deri-
mot gode resultater når instansene er av realistiske størrelser. Disse løsningsmetodene
vurderes derfor som lovende til å kunne være en del av et verktøy som kan brukes for
beslutningsstøtte for rederier som står ovenfor lignende problemer.
viii