Improvement of a multi-tubular Fischer–Tropsch reactor with gas recycle by appropriate combination of axial activity distribution and gas velocity

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Kern, Christoph ; Jess, Andreas:
Improvement of a multi-tubular Fischer–Tropsch reactor with gas recycle by appropriate combination of axial activity distribution and gas velocity.
In: Catalysis Science & Technology. Bd. 13 (2023) Heft 7 . - S. 2212-2222.
ISSN 2044-4761
DOI: https://doi.org/10.1039/D3CY00093A

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Abstract

Fischer–Tropsch fixed bed synthesis is frequently conducted with a gas recycle and a CO conversion per pass of less than about 60. In this paper, we have investigated the influence of a gas recycle on the performance of a multitubular reactor (tube length 12 m, diameter 3 cm) for different total CO conversions (XCO,total) and superficial gas velocities (us). The impact of the axial distribution of the intrinsic activity of the Co catalyst in the tubes was also studied. XCO,total is 95 for the optimal value of us of 1 m s−1 combined with a constant activity coefficient Ca of 3 (which equals a Co content of the catalyst of 30 wt); the conversion per pass is then 45. Further improvement (XCO,per pass = 47) is possible by using tubes with two zones of equal length (6 m) and a suitable activity distribution (Ca,1 = 2.5, Ca,1 = 3.5). An activity grading (Ca,mean = 3) with Ca,initial = 2.2 until Tmax of 240 °C is reached at z = 2.2 m and then a stepwise rise to Ca of 4 in the remaining 9.8 m leads to XCO,per pass of 49, the maximum for the given conditions.