Thermal Conductivity of Cobalt-Based Catalyst for Fischer–Tropsch Synthesis

Abstract

In this study, the thermal conductivity of cobalt-based catalyst specimens in the temperature range from 160 • C to 255 • C are measured via a steady-state apparatus. The apparatus and procedures are applied to several specimens of cobalt-based catalyst powder compacts. Specimens with different degrees of porosity are produced by pressing cobalt-based catalyst powder with a particle size of (80 to 360) mesh. The thermal conductivity of cobalt-based catalyst powder compacts is investigated as functions of temperature, specimen density, porosity, and powder size. The results indicate that the thermal conductivity of the catalyst specimens increases linearly with temperature and density and is practically independent of the particle size of the powder in an atmosphere of air, while the porosity dependence of the thermal conductivity is inverse to that of density. In addition, the effects of some measuring factors on the thermal conductivity show that the reliability of the thermal conductivity measurements of cobalt-based catalyst specimens are influenced easily by parallelism, specimen roughness, and moisture content, whereas the specimen thickness and water bath temperature have only a slight effect on the reliability. A Cu Cross-section area of copper heat probe (m 2 ) A S Cross-section area of specimen (m 2 ) L 1Horizontal distance between two thermocouples welded on the lower heat probe (m) L 2 Distance between the measuring end of the upper heat probe and thermocouples welded on the lower heat probe (m) L S Thickness of specimen (m) R Correlation coefficient R Total thermal resistance (km 2 · W −1 ) t 1 , t 2 Temperatures of the lower heat probe ( • C) t 3 , t 4 Temperatures of the upper heat probe ( • C) Greek Symbols λThermal conductivity (W · m −1 · • C −1 ) λ Cu Thermal conductivity of copper heat probe (W · m −1 · • C −1 ) δL S /L S Measuring error of specimen thickness δ D/D Measuring error of specimen diameter δ t/tMeasuring error of temperature difference

Multidimensional modeling of a microfibrous entrapped cobalt catalyst Fischer‐Tropsch reactor bed

“…The effective thermal conductivity of the bed is calculated from the volume-averaging of the bulk fluid (k f ) and solidphase (k p ) thermal conductivities. The latter is obtained from a volume-averaging of dense inert packing and porous catalyst thermal conductivities, with the former assumed as copper to represent MFECC fibers with k Cu 5380 W=m K (adopted from Yaws critical database 49 ), while the effective thermal conductivity is calculated as follows 50 @T @r 50 @ r50; @T @r 5h T c 2T ð Þ@ r5r bed ; T5T o @ z5z 3 ; @T @z 50 @ z50 (18) In all case scenarios considered in this study, the coolant temperature was maintained equal to the inlet gas flow temperature, and the wall boundary heat-transfer coefficient (h) was evaluated as k w 512 W=m K, assuming a stainless steel of wall thickness 1:5310 24 m.…”

“…The pellet solid‐phase thermal conductivity was determined via previously developed correlation fitted to data provided in Ref. for cobalt‐based FTS catalysts …”

“…1,[6][7][8][9] The utilization of cobalt-based catalysts for FTS reaction was originally reported in 1902 1 and commercially deployed in the 1920s, is the major area of development for improvements in physical and chemical properties of the catalyst. [10][11][12][13][14][15][16][17][18] The primary challenge in FTS reactor design is management of the acute reaction exothermicity (DH $ 2152 kJ) to avoid the formation of local hot spots. The hot spot formation significantly increases methane selectivity, which is extremely counterproductive.…”

“…GTL technology and its counterparts, coal‐ and biomass‐to‐liquid technologies (occasionally lumped together as XTL; where X represents: natural gas, coal, or biomass), enable production of petrochemicals from diverse fossil and renewable hydrocarbon resources . The utilization of cobalt‐based catalysts for FTS reaction was originally reported in 1902 1 and commercially deployed in the 1920s, is the major area of development for improvements in physical and chemical properties of the catalyst . The primary challenge in FTS reactor design is management of the acute reaction exothermicity ( ∼ −152 kJ) to avoid the formation of local hot spots.…”

Study on Effective Radial Thermal Conductivity of Gas Flow through a Methanol Reactor

“…A model with a linear variation of λ er in the vicinity of the wall is proposed to the description of the radial heat transfer in the packed bed. Wu et al [25] investigated the thermal conductivity of catalyst powder compacts and found that the thermal conductivity of the catalyst specimens increases linearly with temperature and density and practically independent of the particle size of the powder in an atmosphere of air, while the porosity dependence of the thermal conductivity is inverse to that of density. Because of the critical importance of heat exchange, mathematical models should be able to represent satisfactorily the relatively complex heat transfer mechanism inside the bed.…”