Wits COMPS Advanced Fischer Tropsch Process

There is an alternative and it is an already proven solution.

Introduction
The Fischer-Tropsch (FT) Process converts a mixture of carbon monoxide (CO) and hydrogen (H2) to hydrocarbons. The carbon monoxide and hydrogen mixture (referred to as synthesis gas) can be obtained from coal, natural gas or biomass. Synthesis gas is versatile in that it can be used to produce not only hydrocarbons (mainly liquid fuels) but electricity and other chemicals (methanol, ammonia) as well.
The Fischer Tropsch reaction takes place in the presence of a catalyst, usually iron or cobalt. The temperature, pressure and catalyst determine the range of product. Fischer Tropsch can be operated in two modes: high-temperature (300 -350?C) process with iron-based catalysts or low-temperature (200 - 240?C) process with either iron or cobalt catalysts.

History
The Fischer Tropsch process was discovered in the 1920’s by German scientists and by 1938 Germany was running nine industrial plants which produce fuel from coal. In the 1950’s, the South Africa Coal Oil and Gas cooperation (SASOL) commissioned an FT plant based on coal in Sasolburg, South Africa. Research on Fischer Tropsch has continued ever since at SASOL. Due to the oil crisis of the mid 1970s, Sasol constructed two much larger coal-based FT plants which came on-line in 1980 and 1982 respectively. These two plants produce approximately 160 000 bbl/day of fuel which supplies 28 % of South Africa’s fuel requirements. Further commercial ventures, which have used natural gas as a feedstock, include Shell’s plant in Malaysia and the PetroSA plant in South Africa. In the last few years the interest for FTS has significantly grown due to the increase in oil prices as well as the high demand for energy. Recent commercial ventures include the development of a GTL (gas-to-liquids) plant, Oryx GTL, in a joint venture of Sasol with Qatar Petroleum at Ras Laffan in Qatar.
Product
Fischer–Tropsch technology produces a mixture of synthetic hydrocarbons, commonly referred to as synthetic crude oil or syncrude, a mixture of straight chain hydrocarbons with a distribution of different amounts of carbon atoms in each molecule. These vary from methane (CH4) to long (C18+) waxes. The reaction produces water and low temperature heat as byproducts.

Products from the high temperature FT have fewer carbon atoms in the molecules, contain more oxygenates and have more branching in the carbon skeleton of the produced molecules than the low temperature systems. This leads to improved gasoline quality. The low temperature routes produce longer carbon chain molecules and less oxygenates. The number of carbon atoms in the spectrum is higher than for the high temperature FT. This leads to a good quality diesel and the products which are heavier than diesel can be readily converted to diesel by a process called hydrocracking.

The Fischer Tropsch process produces high value, clean-burning fuels. FT fuels can be used in conventional engines with no modification and have improved combustion which reduces emissions. The resulting fuels are colourless, odourless and low in toxicity. FT fuels have less sulphur, nitrogen oxide, carbon monoxide and particulate matter emissions than petroleum fuels.

COMPS Technology
The technology on offer is a new generation of Fischer Tropsch Technology. This South African developed technology can be applied in both Gas to Liquid (GTL), Coal to Liquid (CTL) as well as Biomass to Liquids (BTL). The technology offers reduced CO2 emissions, reduced capital and operating costs as well as simplicity of operation and ease of scalability.

The COMPS approach is to build small modular processes which have the advantages of being less capital intensive, more flexible and faster time-to-market.

This design is the result of an application of the process synthesis and optimisation methods developed at the Centre and our collaborations with other world leaders in the field. These methods were used to identify and systemically reduce or eliminate the inefficiency present in the process.

The design builds on our extensive experience in the areas of Fischer Tropsch Catalysis, Process assessment and Process Synthesis.

How does this technology compare to the Conventional Fischer Tropsch Synthesis Technology?
Conventional Fischer Tropsch technologies make use of a pure oxygen feed with a large process recycle. This requires the inclusion of such capital intensive items such as cryogenic air separation and reformer units. These impact on, not only the capital and operating costs of the process, but also increase the CO2 emissions of the process. The elimination of this equipment permits a significant cost saving as well as a reduction in the CO2 emissions by as much as 20 %.

Click for Full Flowchart

Click for Full Flowchart

Fischer Tropsch Reactor
Three main types of reactor are used for FT reaction: Fixed bed reactors, Fluidised bed reactors and Slurry bed reactors. A major aspect of the reactor design is the efficient and rapid removal of heat from the highly exothermic FT reaction. An overheating of the catalyst would adversely affect product selectivity and catalyst lifetime.

COMPS on the basis of their more than 15 years of experience with FT technology and their unique analytical methods have proposed that the first incarnation of the technology to be implemented makes use of a dry-feed fixed-bed reactor.

Fixed-bed reactors are well understood and we have the capability to model these accurately. This permits the rapid assessment of piloting information. In addition the ability to pilot on a small scale with a small number of the full size and length tubes permits a high degree of confidence when moving from the pilot to commercial design. This confidence cannot be duplicated by other reactor designs. In fact the only difference between pilot fixed bed reactors and full scale reactors is the number of tubes in the reactor shell.

In terms of heat removal; by controlling the size of the tubes and designing the shell-side steam energy removal system appropriately, it is possible to ensure the necessary heat removal.

Commercialization
COMPS is currently involved with Golden Nest in the building of a CTL plant in China and with Linc Energy in the building of a Fischer Tropsch plant in Australia.

Golden Nest project:
COMPS is involved in the building of a demonstration coal-to-liquids (CTL) plant in the Shaanxi province in China. The R75-million (US$10.5-million) demonstration plant project is expected to be more efficient than the current technology. The project is being funded by the Golden Nest Technology Group, which contracted COMPS in 2003 for the development of the conceptual foundation of a coal-to-liquids (CTL) plant.

The construction of the plant was completed toward the end of last year (October 2007) followed by cold commissioning that started in November 2007. The plant was successfully started up in April 2008 and it currently operates at 40% capacity. More modules are expected to be brought online and the plant will be operating at its full capacity in the beginning of August 2008. The data from the demonstration plant will be used for the development of the commercial plant.

Linc Energy project:

Linc Energy Ltd is currently in the process of constructing a CTL demonstration plant based on COMPS Fischer-Tropsch technology near Chinchilla, Queensland, Australia. The plant will be unique in that it will be the first CTL plant in the world to be operated using underground coal gasification. This is an extremely exciting venture as it could quite substantially reduce the CAPEX requirements of a commercial CTL plant by eliminating the need for gasifiers, which are extremely expensive.

The plant will have a limited capacity (5 bbl/day) but the scale is irrelevant as the fixed bed reactors will be piloted at full scale tube sizes and therefore will be perfectly representative of commercial scale operation. The plant is being commissioned at present.

COMPS has provided LINC Energy with a range of consulting services in respect of this project. The conceptual design for the FT synthesis section and associated product recovery system of this plant was developed by the COMPS team. The same team then acted in an advisory role in respect of the completion of the basic and detailed design of the process components and the subsequent fabrication thereof.

In parallel with these activities, COMPS has been responsible for the testing of the catalysts proposed for the process. This has resulted in a short listing of the catalysts to be used for the demonstration plant as well as important information for the operation and product selectivity of said catalysts. This information is to be used in the start-up and operation of the demonstration facility.

Conclusions
The COMPS team has developed a novel technology design that is less capital intensive, based on proven technology and implementation strategies, is simpler to start up and operate than exist commercial technologies. In addition to these benefits, the proposed process design offers reduced water consumption and CO2¬ emissions when compared to equivalent commercial technologies. In short, we believe that in this technology we are offering an opportunity to leapfrog, technologically, over the other available designs.