Published: November 21 International Petroleum Technology Conference. You can access this article if you purchase or spend a download. Sign in Don't already have an account? Personal Account. You could not be signed in. Please check your username and password and try again. Sign In Reset password. Sign in via OpenAthens. Pay-Per-View Access. Buy This Article. Annual Article Package — Buy Downloads. View Your Downloads. View Metrics. Even though the technology for syngas generation is considered proven, its application in GTL plants is complex and costly.
Significant research is ongoing in this area to reduce cost. The FT synthesis section involves the conversion of synthesis gas to long-chain, heavy paraffinic liquid. Paraffin is a mixture of high-molecular-weight alkanes i. Large quantities of water are produced as a byproduct, which is required to be treated before disposal or reuse.
Small quantities of CO 2 , olefins, oxygenates, and alcohols are also produced as byproducts. Large quantities of heat are generated in the process that must be removed. This energy is partially recovered by the production of steam. The product slate from a FT reactor is dependent on the type of catalyst and the operating conditions of the reactor. Generally, an iron-based or cobalt-based catalyst is used for FT synthesis.
The choice of the catalyst is to some extent related to the type of feed to the GTL plant. For natural gas feed, a cobalt-based catalyst is more likely to be used. Several publications [4] [5] discuss the pros and cons of the various reactor designs. The operating conditions vary depending on:. The FT product is totally free of the sulfur, nitrogen, metals, asphaltenes, and aromatics that are normally found in the petroleum products produced from crude oil. Table 1 compares the quality of the products from the FT process with that of conventional refinery-based products.
These products are processed further in the product-upgrading unit to primarily produce naphtha, kerosene, and diesel. There is a variety of specialty products that can be produced from FT products such as:. The market for these products is limited. The product-upgrading step involves processes very similar to processes used in a crude-oil refinery.
Besides the three process steps detailed in this section, the GTL facility includes a large utility plant, offsites, and infrastructure. GTL production can be described as utility intensive; it is both a large producer and consumer of energy. The magnitude of the utilities for a GTL plant is evident from the large amount of power required to operate these plants. The GTL plant is not based on just one technology but brings together several technologies on a large scale.
These technologies include:. GTL plants produce petroleum products, which are sold in a commodity market. The size of the market is large, on the order of 1, million tonnes per annum. GTL technologies available from different licensors differ in process configuration, thermal efficiencies, and capital cost; hence, the amount of gas required to produce a specific amount of liquid varies. With only two commercial GTL plants built in the past 10 years, there is little information available on the capital cost of these facilities.
However, it is widely believed that technology developments in syngas generation, FT reactor, and catalyst technology have resulted in significant reduction in capital costs of GTL plants in recent years. Since natural gas burns much more cleanly than oil and is also more abundant, developing this technology would appear to offer an important step in the future of energy supply and towards a cleaner environment. But, at least until recently, the main barrier to the mainstream use of GTL has been the complexity of the process — and therefore the cost.
Changing natural gas into a liquid is not a new idea; in fact, synthetic fuel production technology was invented in the s, when the most common technique, the Fischer-Tropsch F-T synthesis, was first developed. This was used in Germany in the s and particularly during WWII, when the country was finding it difficult to source conventional oil and refined product supplies. By , Germany was using F-T technology at an industrial scale, with nine plants producing about 14, bpd.
Source: Shell. Using coal as the feedstock, by the s South Africa was producing several thousand barrels of synthetic oil a day, developing a number of plants over subsequent years; this is referred to as 2nd generation GTL technology.
The technology continued to evolve, with gas becoming the preferred source. The commercialization of this technology is still evolving, and there are only a handful of large, fully commercialized plants in the world, all complex and expensive to build and run. The main barriers to efficiency appear to be the low productivity of the Fischer-Tropsch reactors, short catalyst lifetime, by-products such as organic acids and heavy alcohols which have to be dealt with and, most importantly, the need to build petrochemical plants to turn hard waxes produced by the standard F-T method into marketable products.
Methods of producing liquids from gas outside the F-T process, without the use of catalysts, have also been developed, in which air or oxygen is burned together with natural gas at high temperatures and pressure to cause particle oxidation, but these have yet to be proved commercial. Therefore, although the F-T process is now nearly years old, the cost of GTL, in small-scale operations at least, remains very expensive.
Franz Fischer a and Hans Tropsch b invented the technique named after them which converts gas or coal into synthetic liquid fuel. An innovative Houston-based company believes it has found a solution to unlock the economic efficiency of the GTL business. The process is uniquely optimized for the production of clean hydrocarbons without oxygenates, thus reducing further waste management issues. We are now looking at the 4th generation of GTL technology — and a major step forward towards commercialization of this process at all scales.
The F-T reaction is carried out at constant temperature as cooling water is circulated on the shell side to maintain the reaction at isothermal conditions. The produced water is collected and reused for the auxiliary and steam system.
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