Visualization of Carbon Particle Tracking and Hydrogen Production in a Solar Reactor
Nesrin Ozalp, JayaKrishna Devanuri, Mohamed Mohamed and Abdalla Abdalla
Texas A&M University at Qatar
Solar thermal cracking of natural gas has attracted researchers for its emission-free production of hydrogen, which has three times more energy content than that of natural gas, and emits mostly water vapor when it is used as a fuel in cars or power plants. The basic mechanism of the solar cracking process is simple: concentrated solar energy is directed to a reactor chamber, where natural gas is injected and absorbs solar energy resulting with hydrogen gas (H2) and solid carbon (C) production. However, there is a major problem affecting natural gas cracking solar reactors’ performance, which can be observed from the first figure; reactor clogging due to solid carbon deposition during the course of this two‐phase solar thermochemical processing. We focused our research efforts to solve this problem so that solar reactors can run without explosion and they can be safely used in hydrogen production without damaging the environment. In order to solve the reactor clogging due to carbon deposition, we have developed a two‐phase, three‐dimensional CFD model including kinetics, heat transfer and incoming solar flux for an in-house developed solar reactor we named “aero-shielded solar cyclone reactor.” The validation for our CFD model has been carried out against the experimental results of the Swiss Federal Institute of Technology and the Weizmann Institute of Science. To further improve our successful CFD code, we optimized the flow conditions for our own reactor and visualized our simulation with Ensight (3D visualization application). We have simulated the gas particle interaction and temperature variations inside the reactor using FLUENT in a Lagrangian frame work by considering the effect of turbulence in a swirl dominated flow. Since FLUENT is compatible with the visualization tool EnSight, the carbon particle tracking and temperature variation inside the reactor are effectively visualized in a three dimensional domain. This 3D visualization of the flow aspects, temperature, concentration variations inside the reactor and thermal hydraulics of gas-particle flow helped us thorough understanding of the solar cracking process and consequently allowed us to successfully solve the carbon clogging problem. The above figures show the path lines and the mole fraction of carbon inside the aero-shielded solar reactor. It can be observed from these figures that carbon deposition on the walls and clogging at the reactor exit is successfully avoided.
