Modelling of fixed bed and slurry bubble column reactors for Fischer–Tropsch synthesis

An extensive review of slurry bubble column reactor and fixed bed reactor steady state models for Fischer–Tropsch synthesis is presented in this work. Material, energy and momentum balance equations are presented here along with the relevant findings of each study for modelling purposes. For fixed bed reactor models, one-dimensional and two-dimensional models can be differentiated, with the latter being better at predicting hot spots and thermal runaways, although the computational effort required solving them is also higher. Fixed bed reactors can also be classified as pseudo-homogeneous or heterogeneous models, the former considering that all phases are in thermal and chemical equilibrium, and the latter having different profiles for the catalyst particles, generally including a pellet model. For slurry bubble column reactors, single-class and double-class bubble models can be differentiated. The double-class bubble models represent better churn-turbulent regimes at the expense of a higher computational effort.

Advances in membranes and membrane reactors for the Fischer-Tropsch synthesis process for biofuel production

The biomass-to-liquid (BtL) process is a promising technology to obtain clean, liquid, second-generation biofuels and chemicals. The BtL process, which comprises several steps, is based upon the gasification of biomass and the catalytic transformation of the syngas that is obtained via the Fischer-Tropsch synthesis (FTS) reaction, producing a hydrocarbon pool known as syncrude. The FTS process is a well-established technology, and there are currently very large FTS plants operating worldwide that produce liquid fuels and hydrocarbons from natural gas (NG) (gas-to-liquids, GtL process) and coal (coal-to-liquids, CtL process). Due to the limited availability of local biomass, the size of the BtL plants should be downscaled compared to that of a GtL or CtL plant. Since the feasibility of the XtL (X refers to any energy source that can be converted to liquid, including coal, NG, biomass, municipal solid waste, etc.) processes is strongly influenced by the economies of scale, the viability of small-scale BtL plants can be compromised. An interesting approach to overcome this issue is to increase the productivity of the FTS process by developing reactors and catalysts with higher productivities to generate the desired product fraction. Recently, by integrating membrane reactors with the FTS process the gas feeding and separation unit have been demonstrated in a single reactor. In this review, the most significant achievements in the field of catalytic membrane reactors for the FTS process will be discussed. Different types of membranes and configurations of membrane reactors, including H2O separation and H2-feed distribution, among others, will be analyzed.

A review of Fischer Tropsch synthesis process, mechanism, surface chemistry and catalyst formulation

For more than half a century, Fischer-Tropsch synthesis (FTS) of liquid hydrocarbons was a technology of great potential for the indirect liquefaction of solid or gaseous carbon-based energy sources (Coal-To-Liquid (CTL) and Gas-To-Liquid (GTL)) into liquid transportable fuels. In contrast with the past, nowadays transport fuels are mainly produced from crude oil and there is not considerable diversity in their variety. Due to some limitations in the first generation bio-fuels, the Second-Generation Biofuels (SGB)’ technology was developed to perform the Biomass-To-Liquid (BTL) process. The BTL is awell-known multi-step process to convert the carbonaceous feedstock (biomass) into liquid fuels via FTS technology. This paper presents a brief history of FTS technology used to convert coal into liquid hydrocarbons; the significance of bioenergy and SGB are discussed aswell. The paper covers the characteristics of biomass, which is used as feedstock in the BTL process. Different mechanisms in the FTS process to describe carbon monoxide hydrogenation aswell as surface polymerization reaction are discussed widely in this paper. The discussed mechanisms consist of carbide, CO-insertion and the hydroxycarbene mechanism. The surface chemistry of silica support is discussed. Silanol functional groups in silicon chemistry are explained extensively. The catalyst formulation in the Fischer Tropsch (F-T) process as well as F-T reaction engineering is discussed. In addition, the most common catalysts are introduced and the current reactor technologies in the F-T indirect liquefaction process are considered.

Modeling of transport phenomena in fixed-bed reactors for the Fischer-Tropsch reaction: a brief literature review

Currently, few processes can be considered practical alternatives to the use of petroleum for liquid fuel production. Among these alternatives, the Fischer-Tropsch synthesis (FTS) reaction has been successfully applied commercially. Nevertheless, many of the fundamentals of this process are difficult to understand because of its complexity, which depends strongly on the catalyst and the reactor design and operating conditions, as the reaction is seriously affected by mass and heat transport issues. Thus, studying this reaction system with transport phenomena models can help to elucidate the impact of different parameters on the reaction. According to the literature, modeling FTS systems with 1D models provides valuable information for understanding the phenomena that occur during this process. However, 2D models must be used to simulate the reactor to correctly predict the reactor variables, particularly the temperature, which is a critical parameter to achieve a suitable distribution of products during the reaction. Thus, this work provides a general resume of the current findings on the modeling of transport phenomena on a particle/pellet level in a tubular fixed-bed reactor.

Recent advances in reactors for low-temperature Fischer-Tropsch synthesis: process intensification perspective

The low-temperature Fischer-Tropsch (LTFT) process aims to produce heavy cuts such as wax and diesel. For many years, there have been studies and improvements on the LTFT process to make the existing reactors more efficient. Recent studies have proposed innovative configurations such as monolithic loop and membrane reactors as well as microchannel reactor, which improved the performance of LTFT synthesis. This persuades us to update the existing knowledge about the available reactors. Some fundamental features of the current reactors, which belong to the classes of conventional reactors (fixed-bed reactors and slurry reactors) and innovative reactors, are discussed to assist the selection of the most efficient reactors specifically for heavy-cuts production. Published experimental and theoretical works with respect to developments in reactor technology and significant advances in catalysis (such as using structured packing, foams, and knitted wire as catalyst supports due to their excellent radial mixing properties) of the FT process are analyzed and discussed. Consequently, it is shown that the LTFT innovative reactors have higher CO conversions and selectivity of desired heavy cuts. Furthermore, the place of innovative reactors among conventional reactors in terms of effective process parameters on the product distribution has been estimated.

Progress in Reactors for High-Temperature Fischer–Tropsch Process: Determination Place of Intensifier Reactor Perspective

High-temperature Fischer–Tropsch (HTFT) process aims to produce lighter cuts such as gasoline and diesel. For many years there have been studies and improvements on HTFT process to make the existing reactors more efficient. Recent studies proposed new configurations such as dual-type membrane reactor and coupling configurations reactor, which improved the performances of this process. This achievement persuades us to update the existing knowledge about the available reactors for HTFT process. In this article, features and performances overview of two classes of reactors are reviewed. The first class consists of the reactors which are based on older studies, and the second one includes recent studies which are called product intensifier reactors. Finally, it is shown that the product intensifier reactors have higher CO conversions and lower selectivity of undesired by-products which results in higher production yield of gasoline. Furthermore, the place of product intensifier reactor among common reactors with regard to the influence of the process parameters on the product distribution has been estimated.