Bahamin Bazooyar

With the growing demand for plastic production and the importance of plastic recycling, new approaches to plastic waste management are required. Most of the plastic waste is not biodegradable and requires remodeling treatment methods. Chemical recycling has great potential as a method of waste treatment. Plastic pyrolysis allows for the cracking of plastic polymers into monomers with heat in the absence of oxygen, allowing energy recovery from the waste. Fluidized bed reactors are commonly used in plastic pyrolysis; they have excellent heat and mass transfer. This study investigates the influence of low and medium process temperatures of pyrolysis on fluidized bed reactor parameters such as static pressure, fluidizing gas velocity, solid movement, and bubble formation. This set of parameters was analyzed using experimental methods and statistical analysis methods such as experimental correlations of changes in fluidized bed reactor velocities (minimal, terminal) due to temperature increases for different particle sizes; CFD software simulation of temperature impact was not found. In this study, computational fluid dynamics (CFD) analysis with Ansys Fluent was conducted for the fluidization regime with heat impact analysis in a fluidized bed reactor (FBR). FBR has excellent heat and mass transfer and can be used with a catalyst with low operating costs. A two-phase Eulerian–Eulerian model with transient analysis was conducted for a no-energy equation and at 100 °C, 500 °C, and 700 °C operating conditions. Fluidizing gas velocity increases the magnitude with an increase of the operating temperature. The point of fluidization could be determined at 1.1–1.2 s flow time at the maximum pressure drop point. With the increase of gas velocity (to 0.5 m/s from 0.25 m/s), fluidizing bed height expands but when the solid diameter is increased from 1.5 mm to 3 mm, the length of the fluidized region decreases. No pressure drop change was observed as the fluidized bed regime was maintained during all analyses. The fluidization regime depends on gas velocity and all the applied fluidization gas velocities were of a value in between the minimal fluidization velocity and the terminal velocity.

In this work, a catalytic combustor for micro electrical mechanical system for syngas was designed and analysed using Direct Numerical Simulation (DNS) in conjunction with finite rate chemistry. The effect of catalyst (platinum (Pt), palladium (Pd), palladium oxide (PdO), and rhodium (Rh)), bed type (packed with twelve catalyst shapes and four catalyst monolith), shapes (packed: cylinder, hollow cylinder, four cylinder, single cylinder, single cylinder, crosswebb, grooved, pall-ring, hexagonal, berl-saddle, cube, intalox-saddle, and sphere, monolith: triangular, rectangular, hexagonal, and circular), and operating conditions (inlet temperature and velocity, fuel/air ratio, different concentrations CH4-H2-CO) on combustion efficiency and pressure drop were studied using different parameters (combustion efficiency (η), pressure drop, effectiveness factor ( ψ ), and fuel conversions (H2 and CH4 conversions)). Analysis under different operating conditions reveals that the designed combustor can operate effectively with syngas of varying compositions with a high combustion efficiency of over 85%. Combustion mainly takes place on the surface of the catalyst without gas phase reaction with pressure drops between 18 Pa to 155 Pa. The intalox saddle shape catalysts resulted in the bed effectiveness factor 0.931. The Damköhler for hydroxyl radicals (OH) over the entire length of the reactor is uniformly distributed and well below 3, suggesting uniform combustion.