(312e) Experimental Investigation of the Impact of Tubes Arrangement on Local Heat Transfer Coefficient in Fluidized Bed Reactor for Fischer-Tropsch Synthesis

The process of converting biomass, natural gas, and coal to liquid fuels and chemicals via Fisher Tropsch synthesis is currently a major interest of the energy and chemical industries, representing a valuable addition to expanding fuel and product resources. The fluidized bed reactor is the preferred reactor for carrying out the Fischer Tropsch process's exothermic reaction. Excess heat due to exothermicity of reaction is removed by inserting a bundle of cooling tubes into this reactor, thus controlling the reaction temperature. Designing and scaling-up this reactor is still a problematic engineering task due to the absence of reliable mathematical models to predict heat transfer for this reactor when equipped with a bundle of heat exchange tubes. Developing and improving any mathematical model or simulation requires reliable data, which is lacking for this kind of reactor. Therefore, this study aims for the first time to assess and quantify the influence of the presence of vertical tubes and their arrangement on the local heat transfer coefficient by using an advanced heat transfer technique. To achieve this aim, a plexiglass column with a diameter of 0.13 m and a height of 1.83 m was designed and fabricated. A bundle of thirty stainless steel tubes was inserted vertically into the fluidized bed column. This bundle of vertical tubes was covered 25% of the cross-sectional area of the column to simulate the industrial Fischer-Tropsch reactor. Two types of tube arrangements (i.e., square and triangle pitch) were investigated in this study. Additionally, two different particles, namely glass beads and aluminum oxide, were used in this investigation. The specifications of those solid particles were chosen according to Fischer-Tropsch industrial requirements. Measurements of the local heat transfer coefficient were measured at different radial and axial locations under a wide range of superficial gas velocities (0.02 to 0.4 m/s). Furthermore, a two-dimensional (2D) image was created by measuring the local heat transfer coefficient at thirty locations at an axial level of 13 cm from the gas distributor. This 2D image visualizes local heat distribution over the entire cross-sectional column.

The knowledge and findings gained from this study would further improve the fundamental understanding of the impact of vertical tubes on heat transfer in fluidized bed reactors. Additionally, the data will also be used to verify reactor models and CFD codes and simulations that promote such a reactor's design and scale-up purposes. The results of this work will be presented in detail on the conference day.