André Peter Steynberg

Fischer-Tropsch Reactors

Publisher Summary This chapter reviews that there are four types of fischer-tropsch (FT) reactor in commercial use at present. Three broad categories of catalyst are used in these reactors. The four types of reactor are: circulating fluidized bed reactor, fluidized bed reactor, tubular fixed bed reactor, and slurry phase reactor. It discusses that the fluidized bed reactors operate in the temperature range 320oC to 350oC. This temperature range is 100oC higher than the typical operating temperature range used with the reactors of around 220oC to 250oC. Hence, the term high temperature fischer-tropsch (HTFT) is used to describe the reactors on the left hand side and the term low temperature FT is used to describe the reactors on the right hand side. The key distinguishing feature between the HTFT and LTFT reactors is the fact that there is no liquid phase present outside the catalyst particles in the HTFT reactors. The chapter also discusses that as compared to many industrial operations the FT reaction is highly exothermic. This is an order of magnitude higher than the typical catalytic reactions in the oil refining industry. Any increase in the operating temperature of the FT synthesis will result in an undesirable increase in the production of methane and may result in catalyst damage.

Introduction to Fischer-Tropsch Technology

Publisher Summary This chapter describes the practical application of fischer-tropsch (FT) technology. It is the means by which synthesis gas containing hydrogen and carbon monoxide is converted to hydrocarbon products. The hydrocarbon products are mostly liquid at ambient conditions but some are gaseous and some may even be solid. For the above definition, the term “hydrocarbons” includes oxygenated hydrocarbons, such as alcohols. However, the sole production of an oxygenated hydrocarbon, such as methanol is excluded. The chapter explores that interest in FT technology is increasing rapidly. This is due to the recent improvements to the technology and the realization that it can be used to obtain value from stranded natural gas. In other words, remotely located natural gas will be converted to liquid hydrocarbon products that can be sold in worldwide markets. This is often referred to as the gas-to-liquids (GTL) industry. The chapter also discusses the application of FT technology usually involves complex integration, it inevitably consists of three basic steps: synthesis gas preparation, FT synthesis, and product upgrading.

Commercial FT Process Applications

Publisher Summary This chapter describes the fischer-tropsch (FT) process applications. The important applications are: feedstock and technology combinations, alternative routes for the production of fuels and chemicals, commercial ft plants, introduction to the gas loop, options for the production of high value hydrocarbons, coal conversion using ft technology, and environmental aspects. The chapter reviews feedstock and technology combinations in detail. It discusses that certain technologies compete for application with the same feedstock. Notable competitors are synthol (HTFT) and cobalt catalyst (LTFT) for natural gas feedstock, as well as iron catalyst (LTFT) and synthol (HTFT) for carbon rich feedstock. While FT technology costs may be an important issue, it is not necessarily the primary decision criteria. The opportunities to add value to the potential project by means of more lucrative co-products is an important consideration. So the desired chemical coproducts may narrow down the choice of technology. The chapter highlights that all the commercial applications to date involve the cooling of the FT reactor outlet gases and vapors to condense hydrocarbon products and reaction water that are separated from a tail gas. Some of this tail gas is typically recycled to the FT reactor.

Chapter 4 - Synthesis gas production for FT synthesis

Publisher Summary This chapter reviews that the technology used to prepare the synthesis gas used for fischer-tropsch (FT) synthesis can be separated into two main categories: gasification and reforming. Gasification is the term normally used to describe the processes for the conversion of solid or heavy liquid feedstock to synthesis gas, while reforming is used for the conversion of gaseous or light liquid feedstock to synthesis gas. Some technologies, particularly high temperature partial oxidation, can be used for a whole range of feeds and the literature may then refer to “gasification” to include methane reforming. The chapter explores that future FT synthesis units may include the co-production of electrical power, so an understanding of the issues relating to power generation is also relevant to the application of FT technology. The most common feeds used to prepare synthesis gas for FT synthesis are coal that is rich in carbon and natural gas that is rich in methane. It also discusses that gaseous hydrocarbons are already valuable products if they can be piped to nearby consumers. Only remotely located gas is considered for large-scale conversion to liquid fuels. However, smaller scale applications for the production of high value chemicals are common wherever natural gas is found. Coal conversion is more expensive than natural gas conversion, but may be worthwhile if the coal price is low enough and if both electricity and higher value hydrocarbon products are co-produced with liquid fuels on a large scale.

Fischer-Tropsch Based GTL Technology: a New Process?

Abstract The 21st century is witnessing the establishment of a new global business based on natural gas processing. The Gas-to-Liquids (GTL) industry is entering a new phase of expansion based on the use of the Fischer-Tropsch (FT) synthesis. While for many this might look like new technology, most of the fundamentals are not so new. Decades ago, the pioneers of this industry were able to foresee with ingenuity and provide with science the foundation that is used by todays engineers and scientists. They also predicted the unique benefits that could be expected from the use of synthetic fuels. Moreover, based on the unique composition of the primary products, they anticipated their importance as chemicals and other non-fuel products. The development of the FT-based GTL technology is intimately related to the initial efforts to apply it using coal as feedstock. Its evolution followed a logical process that was delayed by years of abundant, low cost petroleum and a lack of stringent fuel specifications aimed at protecting the environment. This work highlights some of these concepts, giving recognition to the FT technology pioneers.

Large scale production of high value hydrocarbons using Fischer-Tropsch technology

Publisher Summary This chapter provides some insights on how the different Fischer–Tropsch technologies can be used to produce mainstream bulk chemical products. For the production of light olefins, the high temperature Fischer–Tropsch (HTFT) process offers many advantages. Using HTFT technology (with optimized catalysts) for the production of light olefins the amount of olefin product can be further enhanced by cracking unwanted longer chain molecules to higher value shorter chain molecules. An overall mass selectivity of 15–30% towards propylene is viable via such a two step approach. Besides the higher olefin content, the low temperature Fischer–Tropsch (LTFT) promoted iron catalyst also has a higher wax yield than cobalt catalysts. As a result of these two differences, the LTFT iron catalyst may offer advantages for the production of various chemicals. A key disadvantage associated with the LTFT iron catalyst use is that it is expensive to reach high syngas conversions. However, for conversions up to about 50% the capital cost expressed per unit product is similar to that for cobalt catalysts.

A Slurry bed reactor for low temperature Fischer-Tropsch

Publisher Summary This chapter discusses the development of the slurry bed reactor and the reason for its development. Fischer–Tropsch (FT) synthesis is commercially performed in one of two ways. High Temperature Fischer–Tropsch is used for the production of a light syncrude for the production of petrol and diesel. Traditionally this is done in the Synthol process, which uses a circulating fluidised bed reactor (CFBR). Low temperature Fischer–Tropsch is used for the production of high molecular weight hydrocarbons, mostly waxes, which can be sold as such or which can be hydrocracked to excellent diesel. For this, Sasol has traditionally used the tubular fixed bed reactors (TFBR). In 1989, to replace the Synthol CFBR, Sasol commissioned the Sasol Advanced Synthol reactor (SASR), the basis of which is a conventional fluidised bed. It turned out to be much cheaper and more effective than the original Synthol CFBR, much easier to operate, with greater flexibility and much less maintenance. Recently, in May 1993, Sasol commissioned a commercial scale slurry bed reactor (SBR) as an alternative to the TFBR for low temperature Fischer-Tropsch synthesis. The experience with this reactor has been very good.

Intensification of commercial slurry phase reactors

Publisher Summary While air separation and synthesis gas generation remain the main contributors to the capital cost of the GTL process units, capital savings can also be achieved in synthesis gas conversion. Improvements in Fischer–Tropsch reactor design allows increased production capacity from the same reactor shell size or equivalent production capacity from smaller reactors through process intensification while maintaining or improving selectivity and overall synthesis gas conversion. The manufacture of large-scale reactors is costly with a limited number of suppliers who have the capacity to produce such vessels. This chapter focuses on the potential of the Fischer–Tropsch slurry phase reactor to contribute to cost reductions per barrel of product through reactor intensification. The cost reduction could be realized through a combination of a lower material and construction cost per barrel of product produced, as well as having access to a larger pool of potential manufacturers. Opportunities will be created to standardize certain components of reactor manufacture in partnership with preferred suppliers. A further benefit is the ability to match the FT reactor capacity to the increasing maximum capacity for vendor-supplied air separation units and synthesis gas-generation units. Single train capacities of ca. 7000 ton/day oxygen are expected to be achievable in the future, which corresponds to a FT reactor capacity of ca. 40,000 bpd.