What do a piece of lignite and an apple have in common?

26 June 2015 – A person taking a hearty bite of an apple does not usually think of lignite, a domestic fuel and raw material. Although it might not be immediately obvious, the relationship between a lump of coal and a round piece of fruit from the supermarket is not so far-fetched.

Many apples have a skin coated with a fine layer of wax for protection — the same principle applies to cheese rind, which gives the dairy product a longer shelf life. This very wax can be obtained from the use of lignite as a raw material.

“You can produce pretty much anything that is usually made of oil or natural gas from lignite — almost anything, from plastic buckets and mobile phone displays to thermal insulation for homes”, says Urs Overhoff, project manager in the research and development team at RWE Generation. This is how it works: the coal is first dried, cleaned and converted into a gaseous substance (synthesis gas) using a coal gasifier. Then, in the last step, catalysts are used to convert the synthesis gas into the final product.

For some time now, the Chinese have used coal for a variety of purposes other than energy generation. The reasons for this are geopolitical in nature: Mongolia has huge lignite deposits but there is hardly any natural gas. Hence, people in the Far East began to convert coal into synthetic natural gas in large plants and transport it in pipelines to the industrial sites. There, it is used to produce fuel and basic materials for the chemical industry or the heating market.

RWE has been in this field since the 1940s (team: reported), and today it is actively driving research and development in the Coal Innovation Centre at the Niederaussem power plant. This includes developing new approaches for using lignite as a raw material. Previous RWE research projects are now proving helpful. The processes are being adapted and optimized in light of the current situation and new conditions. Because technology has moved on, new ideas are creating a better economic base and increasing efficiency.

The current project: on a test stand in Niederaussem, RWE will soon test catalysers to produce naphta, waxes and fuels using the so-called Fischer-Tropsch technique, a large-scale technical process for coal liquefaction. Naphtha is used, among other things, as a raw material for the petrochemical industry: “Many products can be produced using naphtha, including plastics, which are also needed for laptops or cars. The waxes can be used to produce components for pharmaceutical products and adhesives, for example, for chip boards.” But the pure wax can also be used to produce candles or lubricants, or as a fine, thin protection for apples and cheese.