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The Bergius Process is a method of production of liquid hydrocarbons for use as synthetic fuel by hydrogenation of high-volatile bituminous coal at high temperature and pressure. It was first developed by Friedrich Bergius in 1913, in 1931 Bergius was awarded the Nobel Prize in Chemistry for his development of high pressure chemistry.[1]

Contents

Process

The coal is finely ground and dried in a stream of hot gas. The dry product is mixed with heavy oil recycled from the process. Catalyst is typically added to the mixture. A number of catalysts have been developed over the years, including tungsten or molybdenum sulfides, tin or nickel oleate, and others. Alternatively, iron sulphides present in the coal may have sufficient catalytic activity for the process, which was the original Bergius process.

The mixture is pumped into a reactor. The reaction occurs at between 400 to 500 °C and 20 to 70 MPa hydrogen pressure. The reaction produces heavy oils, middle oils, gasoline, and gases. The overall reaction can be summarized as follows:

n{\rm C} + (n+1){\rm H}_2 \rarr {\rm C}_n{\rm H}_{2n+2}

The immediate product from the reactor must be stabilized by passing it over a conventional hydrotreating catalyst. The product stream is high in naphthenes and aromatics, low in paraffins and very low in olefins. The different fractions can be passed to further processing (cracking, reforming) to output synthetic fuel of desirable quality. If passed through a process such as Platforming, most of the naphthenes are converted to aromatics and the recovered hydrogen recycled to the process. The liquid product from Platforming will contain over 75% aromatics and has a RON of over 105.

Overall, about 97% of input carbon fed directly to the process can be converted into synthetic fuel. However, any carbon used in generating hydrogen will be lost as carbon dioxide, so reducing the overall carbon efficiency of the process.

There is a residue of unreactive tarry compounds mixed with ash from the coal and catalyst. To minimise the loss of carbon in the residue stream, it is necessary to have a low-ash feed. Typically the coal should be <10% ash by weight. The hydrogen required for the process can be also produced from coal or the residue by steam reforming. A typical hydrogen demand is ~8 kg hydrogen per ton of dry, ash-free coal.

History

Friedrich Bergius developed the process during his habilitation. A techniques for the high-pressure and high-temperature chemistry of carbon-containing substrates yielded in a patent in 1913. In this process liquid hydrocarbons used as synthetic fuel are produced by hydrogenation of lignite (brown coal). He developed the process well before the commonly-known Fischer-Tropsch process. Karl Goldschmidt invited him to built an industrial plant at his factory the Th. Goldschmidt AG (now known as Evonik Industries) in 1914.[2] The production began only in 1919, after the World War I ended, when the need for fuel was already declining. The technical problems, inflation and the constant criticism of Franz Joseph Emil Fischer, which changed to support after a personal demonstration of the process, made the progress slow and Bergius sold his patent to BASF, where Carl Bosch worked on it. Before World War II several plants where built with an annual capacity of 4 million tons of synthetic fuel. These plants were extensively used during World War II to supply Germany with fuel and lubricants.[3]

Use

Ruins of coal elevator in a synthetic gasoline plant from WWII (IG Farben Industrie Police, Poland)

The Bergius process was extensively used by Nazi Germany and targeted for bombing during the Oil Campaign of World War II. At present there are no plants operating the Bergius Process or its derivatives commercially. The largest demonstration plant was the 200 ton per day plant at Bottrop, Germany, operated by Ruhrkohle, which ceased operation in 1993. There are reports [4] of the Chinese company constructing a plant with a capacity of 4 000 ton per day. It was expected to become operational in 2007 [5], but there has been no confirmation that this was achieved.

See also

References

External links

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