Renaissance of Syngas Technology
Where Coal Gasification Makes Sense
Nevertheless there are countries where coal is so cheap that gasification is economically feasible. South Africa is often cited as an example, but China is following in South Africa’s footsteps and is exploiting its coal reserves to cover its need for basic chemicals and to reduce its dependency on oil exporters. China is using Fischer-Tropsch synthesis as well as the Lurgi MegaMethanol process which can be used to produce polypropylene directly from coal. When the contracts worth € 100 million were awarded in November 2006 for two projects covering the raw gas upgrading, methanol synthesis and methanol-to-propylene process phases, Lurgi Executive Board Chairman Klaus Moll proclaimed with great satisfaction that this signified the breakthrough in the industrial use of the new technology. Although syngas plays a major role in polypropylene production, plastic production volumes are still relatively modest. More than half of the gas is used to produce ammonia, followed by refinery hydrogen at 22 percent and methanol at 14 percent. Despite all of the hype about the coal-to-chemical strategy launched by the Chinese who would like to export the chemicals, people sometimes forget that natural gas is still the main input material for syngas. Natural gas is readily available, cheap, the equipment needs are reasonable and the technology has a proven track record. Steam reforming and partial oxidation or a combination of the two are the most commonly used processes at the present time.
Crucial Drawback: Cost Expensive And Large Plants
This is all mature, state-of-the-art technology, but there is a crucial drawback. The plants are very expensive, extremely large and as the reaction temperature is just under 1000 °C they consume large amounts of energy. At a recent Dechema Colloquium, Karsten Büker who works in the Research & Development Division at Uhde in Dortmund/Germany pointed out that multi-stand systems which supply 100,000 standard cubic meters of hydrogen per line are currently state-of-the-art in the industry. As a result, even very minor improvements can produce real cost savings. Process engineers are currently concentrating on catalysts which are more active and display less of a tendency to coking. To counteract the trend to even larger plants, Uhde has developed an autothermic methane reformer which does however require upstream air decomposition. Nevertheless, due to advantages of scale, the capital investment costs are lower compared to a steam reformer, emphasized Büker.
Udhe expanded its portfolio at the beginning of the year when it acquired RWE’s High-Temperature Winkler Process (HTW Process). Besides its Prenflow (pressurized entrained flow) process, the company can now offer an additional solids gasification technique which is particularly suited for lignite and bituminous coal that has a high ash melting point as well as for biomass such as wood, peat and even domestic waste. Karsten Radtke, who is in charge of the Uhde Gas Systems Business Unit believes that these input materials offer significant potential for the future.