Completed Research
Stress Analysis and Modeling of a Microchannel Reactor for Fischer-Tropsch Synthesis
Rajan B. Kher, MS, 2018
(Thesis: University of Pittsburgh ETD)
The main objective of this research is to conduct stress analysis calculations and modeling of a MCR for Fischer-Tropsch (F-T) synthesis with the aim to build an optimized lab-scale micro-channel reactor (MCR) in our laboratory. 2-D and 3-D models were used for stress analysis calculations in a MCR containing 10 channels and provided with two 10-mm diameter hole for gas entrance and exit. The analyses, including total deformations, von Mises stresses and principal stresses, were calculated with ANSYS using the Finite Element Method. Two different construction materials for the MCR, namely Plexiglas and 316 Stainless Steel were considered in the calculations. Also, a 2-D pseudo-homogeneous dispersion model was built in MATLAB to investigate F-T synthesis using cobalt catalyst in the MCR. The effects of superficial syngas velocity and H2/CO ratios on the CO conversion were investigated. This study led to the following conclusions:
1. The 2-D stress analysis model predicted the failure of the MCR inlet surface by evaluating the elastic plastic fracture mechanics of the structure. The 3-D stress analysis showed that the maximum stresses exhibited within the structure were generally lower than the maximum yield strength of both Plexiglas and Stainless steel.
2. Increasing the inlet superficial gas velocity decreased the CO conversion and the temperature distribution in the MCR. The highest CO conversion and temperature values were exhibited at the centerline of the reactor. The temperature gradients decreased significantly with increasing superficial gas velocity. Decreasing the H2/CO ratio of the feed systematically decreased the CO conversion throughout the packed-channel, whereas increasing the H2/CO ratio resulted in higher and steeper CO conversion contours. The hydrocarbons yield was determined to be 3.84 bbl/day for 3600 channels with dimensions of 4 mm x 4 mm x 150 mm operating at P = 25 bar, T = 483 K, H2/CO ratio of 2, and a superficial inlet velocity of 0.05 m/s, the yield was also determined to be 4.24 bbl/day when operating at a superficial velocity of 0.01 m/s.