Dr. Feichi Zhang

Students of chemical engineering/process engineering (or similar) with an interest in numerical work and a preference for programming. Knowledge in CFD, simulation of multiphase flow, and fluidized bed technology can facilitate entry into the work but are not mandatory.

Location: CS/CN

Motivation:

Plastic pyrolysis offers several advantages regarding the sustainable management of plastic waste, enabling the recovery of valuable resources from plastic waste. Through the thermal decomposition of plastics in the absence of oxygen, liquid or gaseous products such as pyrolysis oil are produced. These products can be further processed and used in the production of new plastics, chemicals, or other high-value products. This technology also allows for the processing of plastics that are difficult to recycle mechanically due to their composition or contamination. This includes mixed plastic waste, contaminated plastics, or plastics with special properties that hinder mechanical recycling methods. The development of efficient pyrolysis technologies requires a profound understanding, which is only limitedly achievable through experimental investigation. In this regard, numerical simulations are employed in this work to achieve a high level of detail in the pyrolysis process of plastic waste in a generic fluidized bed reactor.

Tasks:

The Euler-Lagrange method is to be applied for simulating the reactive particle-gas flow in the fluidized bed. An existing solver in the CFD code OpenFOAM will be utilized, which considers particle-particle collisions, inter-class heat transfer between particles, and the pyrolysis reaction. The focus of the work is to investigate the influences of key operating parameters such as reactor temperature, superficial gas velocity, sand mass, size of plastic particles, and plastic mixing ratio on the pyrolysis process. Additionally, the hydrodynamic behavior and its influence on the heating process of the plastic particles are to be examined. Subsequently, the consequences of enhanced heat transport due to the hydrodynamic interaction of sand-plastic-gas phases on the pyrolysis reaction or the conversion process of plastic particles are to be derived. The correlations between hydrodynamic behavior, plastic particle heating, and the pyrolysis process with the selected operating parameters are to be quantitatively determined. The results from OpenFOAM simulations are to be compared with computational results from simplified 0D models to identify the influence of ideal and more realistic conditions on the simulation results.

Further tasks may be assigned depending on the students' prior knowledge/interests, focusing on investigations of the effects of scaling up, plastic melt, detailed pyrolysis kinetics, and shockwave fluidized beds.

The work includes, among others, the following steps:

• Literature research and familiarization with the required program tools.
• Creation of the geometry and computational grid for the reactor system.
• Conducting simulations of the fluidized bed reactor for cold flow conditions on the high-performance computers at SCC/KIT.
• Conducting simulations of the fluidized bed reactor for reacting flow conditions on the high-performance computers at SCC/KIT.
• Presentation and analysis of the results, comparison with existing measurements.
• Derivation of a correlation between yield and operating parameters.
• Summary of the work and presentation.

Responsible:

Prof. Dr. Dieter Stapf