Fischer-Tropsch Synthesis

The threat of depletion of crude oil resources over the last few decades has generated an increasing interest in practical applications of Fischer-Tropsch synthesis (FTS) based technologies [1].
FTS is a process to convert synthesis gas (a mixture of CO and H2) to a wide range hydrocarbons that can be used as liquid fuels or base chemicals. The feedstock for the generation of synthesis gas can be natural gas, coal and biomass. Indirect conversion of coal, natural gas and biomass into hydrocarbons can play a major role in solving the world’s current energy problems. The mixture of hydrocarbons produced by FTS is commonly referred to as a synthetic crude oil or syncrude for short [2].
This project is commissioned by ‘The Dow Chemical Company’.

Sasol has been operating Fischer-Tropsch plants on a commercial scale since 1955. LTFT processes are operated by
Sasol at Sasolburg in South Africa, producing predominantly high molecular mass linear alkanes and waxes. Shell developed a cobalt-based LTFT fixed bed process that was used for the gas-to-liquids (GTL) plant in Malaysia [5]. Both processes are carried out with the aim to produce liquid fuels (gasoline, diesel). Only little attention has been paid to LTFT for the production of compounds other than fuels.
The objective of this case study is to design a small-scale LTFT process for the production of syncrude which can be used for . The process should produce 50-100 kiloton of product per year. The pilot plant should have the potential to be developed further at a larger scale.
Furthermore some requirements have to be met by the product in order to allow it to be send to a steam cracker. The desired products are linear and saturated hydrocarbons with a chain length of
C5 – C20, as these hydrocarbons are easy to crack [4]. A low olefin to paraffin ratio is desired.

Also, oxygenates are not present in naphtha from crude oil. The presence of oxygenates has been taken into account.
However, details about the separation of oxygenates are beyond the scoop of this project. The requirement regarding the chain length is also important. Cracking of hydrocarbon molecules with more than 20 carbon atoms require more severe conditions than applied during steam cracking.

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Industrially they are converted to shorter chain hydrocarbons by hydrocracking [6]. Because long chain hydrocarbons have a higher boiling point their present will cause problems during steam cracking which takes place in the gaseous phase. In addition, the formation of methane is also undesired, since it is not valuable and it is used to make syngas.
Moreover, there are different possibilities for the feed. The feed can be chosen to be pure syngas or diluted syngas from waste streams.
This report is written in fulfillment of the course Conceptual Design Project (CPD). The CDP course is part of the 4th year’s curriculum for students studying the MSc program Chemical Engineering at the Chemical Engineering (ChemE) Department of the Faculty of Applied Sciences (TNW) at