Literature Review on Heat Transfer in Two- and Three-Phase Bubble Columns

Abstract

Fischer-Tropsch synthesis (FTS), an exothermic reaction where hydrogen and carbon monoxide synthesis gas are converted to hydrocarbon products, has been under development since the 1930's. The interest in FTS depends on current and perceived future prices of crude oil but is increasingly viewed as an option for exploiting stranded natural gas. Other advantages of FTS hydrocarbons include the absence of sulphur, nitrogen, heavy metal contaminants, low aromatic content and the ability to produce high value middle distillates/fuels. Current interest is directed towards slurry bubble processes – comprising gas, liquid, and solid phases. Industrial slurry phase FTS reactors may range in size from 6 – 10 m in diameter and upwards of 30 m in height and include multiple internal heat transfer tubes. Such systems offer numerous advantages including high heat transfer rates, good mixing, and ease of online catalyst addition and withdrawal. However, one disadvantage is the complex hydrodynamics associated with slurry bubble columns, which make scale-up difficult. A literature review on heat transfer studies and correlations has been completed focusing on previous experimental setups, the synthesis of the key findings/parameters, and the identification of the necessary criteria required for reactor design and scale-up.The parameters having the most pronounced impact on heat transfer in slurry bubble columns and three-phase fluidized beds are the superficial gas velocity and liquid properties such as viscosity and surface tension, which significantly alter the bubble properties and the column hydrodynamics. The effect of particles is poorly understood and is a complex function of particle diameter and concentration. The experimental results and correlations reported here from the majority of studies are dependent upon the equipment and properties of the three phases studied – resulting in very limited applicability to other systems or for scale-up. Other concerns include the use of relatively low gas velocities, ambient temperature and pressure, relatively large particles, and relatively small columns employed in most studies, which are not relevant to industrial operating conditions. Furthermore, studies involving multiple internals were relatively few. Most columns were only equipped with a single tube or small heat flux probe thereby measuring only the local heat transfer and not taking into account the effect on column hydrodynamics of multiple internals. Of these studies only a few tubes were equipped with heaters (that did not run the entire tube length) and heat flux probes while the remaining probes were inactive.

Fischer–Tropsch Synthesis in Slurry Bubble Column Reactors: Experimental Investigations and Modeling – A Review

“…Hulet et al [309] reviewed the heat transfer studies in BCRs and recommended that more work involving columns with internals needs to be conducted to develop reliable models for predicting large-scale unit performance. Kölbel and Ralek [310] suggested the insertion of honeycombed cross section vertical shafts inside the column, with cooling pipes located in corners or around the shafts.…”

Bubble columns for condensation at high concentrations of noncondensable gas: Heat‐transfer model and experiments

“…The heat transfer is via a heattransfer resistance R impact , and the mass transfer is represented by the heat source q lt;impact . Several researchers 19,20,[23][24][25] have previously studied the thermal resistance between the pool of liquid and the immersed surface in a bubble column reactor. In the this article, this resistance is represented as R bc between T coil and T column .…”

“…18 They are used especially in chemical processes involving reactions that have a very high heat release rate associated with them (such as the Fischer-Tropsch process used in the manufacture of synthetic fuels). 19,20 We propose to apply this device for condensation of the air-vapor mixture with a large percentage of air present in it. Figure 1 illustrates the proposed device schematically.…”

Bubble column reactors for high pressures and high temperatures operation

“…They can also be used to operate other processes such as gas conversion to produce fuels or fermentation and biological wastewater treatment in the field of biochemical processes. The Fischer-Tropsch synthesis, which is the coal liquefaction to produce fuels, is carried on bubble columns and M a n u s c r i p t 2 is widely studied in the literature (Behkish et al, 2002;Deckwer et al, 1980;Gandhi et al, 1999;Hulet et al, 2009;Krishna and Sie, 2000).…”