Characteristics and kinetic study on catalytic and non-catalytic pyrolysis of PVC and wind blades in molten salts via thermogravimetric analysis

Background

Polyvinylchloride (PVC) is widely used in modern society and daily life due to excellent properties such as good machinability, long lifespan, low cost and chemical resistance. The huge production of PVC results in a significant amount of waste PVC. Waste PVC is a distinctive solid waste containing chlorine because PVC monomers contain 56.7 wt.% chlorine. The recycling and disposal processes of waste PVC are different from those of other types of plastic wastes due to the incorporation of chlorine, various stabilizers, plasticizers, and flame retardants during the manufacturing of PVC products. The treatment of waste PVC by chemical recovery methods, including pyrolysis, hydrothermal treatment, ionic liquid dissolution, AND mechanical ball milling, has been the focus of research for decades, not only for the waste management of waste PVC, but also for the energy recovery.

Wind turbine blades are typically made of fiber (carbon fiber or glass fiber)-reinforced lightweight polymer composites. Because of the inhomogeneity and complicated nature of these blades, their recycling is economically challenging. Pyrolysis can be a promising option to produce energy and useful materials through recycling of complicated inhomogeneous waste substances. Thus, pyrolytic recycling of decommissioned wind turbine blades would become a solution not only for their disposal but also for the recovery of high-value products (i.e., upcycling of decommissioned wind turbine blades).

Molten salts pyrolysis can offer not only enhanced heat transfer during plastic pyrolysis, but also exist catalytic effect on the reaction upon various salt compositions. According to previous research, the main pyrolysis temperature range of plastics is between 350 °C and 600 °C. Molten salts exhibit different melting and boiling point characteristics due to different combinations of cations and anions. Chlorides and alkali metal salts have been studied in the field of plastic pyrolysis, but chlorides will seriously inhibit the yield of pyrolysis oil. Notably, the production of plastic into pyrolytic oil (rather than pyrolysis gases) is the current mainstream process with the advantages of storage, transportation, and high-value utilization. Overall, alkali metal salts may be the optimal system for plastic pyrolysis, which is beneficial for improving oil yield and enriching main components.

This project is divided into two master theses focusing on PVC foam and wind blades, respectively.

Methodology

The main work includes:

1. Literature studies of molten salt pyrolysis system and kinetic/thermodynamic study via thermogravimetric analysis.  

2. Conduct TG-FTIR of PVC plastic with/without pretreatment to determine its primary decomposition temperature and evolved gas components.

3. Conduct TG-FTIR of wind blades to determine its primary decomposition temperature and evolved gas components

4. Conduct TGA and DSC analysis of selected molten salt systems to determine their melting and boiling points.

5. Conducting micro-scale tests of plastic molten salt pyrolysis using TG-FTIR to explore its catalytic and dichlorination performance.

Prerequisites

To be applicable, the student should be familiar with thermochemical reactions, kinetics and thermodynamics.

To apply send your CV together with university grades and expected starting date!

Suggested Time Plan

Oct. 2024 – Jun. 2025 (open for change)

Contact Persons

Hanmin Yang

hanmin@kth.se