PhD Defence by Amirali Rezazadeh

Principal supervisor:
Associate Professor Ioannis V. Skiadas
DTU Chemical Engineering

Co-supervisors:
Emeritus Kaj Thomsen
DTU Chemical Engineering

Associate professor Hariklia N. Gavala
DTU Chemical Engineering

Associate professor Philip Loldrup Fosbøl
DTU Chemical Engineering

Examiners:
Associate professor Jens Abildskov (Chairman)
DTU Chemical Engineering

Head of Section Jørgen Peter Jensen
COWI A/S

Principal Scientist Antoon J.B. ten Kate
Nouryon

Chairperson at defence:
Associate professor Xiaodong Liang
DTU Chemical Engineering

The defence will also be held virtually. If you wish to follow the defense virtually you can sign up by sending an e-mail to Christian Ove Carlsson cc@kt.dtu.dk latest 7 September at 9:00. You will then afterwards receive an invitation to join the virtual defence.

Popular science summary

Nowadays, plastics have been widely used in every aspect of our lives. Its widespread application in every corner of today's economy creates a massive demand for its production. This increment in plastic manufacturing escalates the concern about the growing amount of waste around the world. Plastic wastes are mainly either incinerated in the waste handling industry or dumped into nature. The increasing amount of plastic residues hurts the environment as well as the economy. It damages the environment since the plastic materials are considered as noxious material remaining in a substantial volume in the waste streams. From the economic point of view, it can lead up to 50-60% of capital loss due to not recycling and not coming back to the life cycle.

The 12th UN sustainable development goal asks for urgent action to ensure that plastic products do not lead to the overexploitation of resources or harm the environment. This thesis aims to contribute to the elimination of the plastic waste issue on a global basis. The contribution is on offering plastic producers and waste recyclers a profitable way to treat and recycle plastic residues. I work on developing a sustainable and beneficial chemical recycling process to close the plastic life cycle. Specifically, I focus on one of the most used plastics, Poly-Ethylene Terephthalate, abbreviated to “PET”.

I explore experimentally the thermodynamics of a chemical system widely used in the plastic recycling industry. This chemical system, which is mainly the product of depolymerization reactions, contains terephthalic acid, disodium terephthalate, sodium hydroxide, sodium chloride, ethylene glycol, and water. The studied chemical system is an electrolyte solution involving various ions and molecules.

This experimental study clearly draws a picture of properties and thermodynamic characteristics, including solid-liquid equilibrium, vapor-liquid equilibrium, density, and viscosity examinations. The thermodynamics of the defined chemical complex is mathematically modelled in order to predict its behavior at various conditions. The model adaption is carried out based on a data bank consisting of almost all of the existing experimental works in addition to the experimental results obtained through this Ph.D. study.

Furthermore, this thesis presents a closed chemical process to recycle PET polymers. The design and simulation of the proposed process are carried out in ASPEN Plus software. In addition to the base case design, several improvements to save up to 15% energy consumption are suggested.