Siemens PG acquired Sustec’s coal gasification activities in mid-2006 in order to supplement its power plant business with products and services related to coal gasification. (Earlier post.) The acquisition comprises the German firm Future Energy GmbH as well as a 50% stake in a Chinese joint venture with the Shenhua Ningxia Coal Group.

The Shenhua Ningmei DME project is the first major coal gasification plant contract that Siemens has been awarded since the acquisition of Sustec.

Siemens Fuel Gasification Technology (formerly Future Energy) GSP Gasifier

Siemens Fuel Gasification Technology’s (formerly Future Energy’s) gasification technology is an entrained-flow pressure gasification system that gasifies a stream of pulverized coal (or atomized liquid fuel or a fuel slurry) with oxygen. Different implementations of the gasifier technology can handle different feedstocks, such as biomass. The gasification pressure ranges from 5 to 26 bar, and the gasification temperature ranges from 1,400º to 1,600º C.

The method offers very high carbon conversion (greater than 99%), and produces a tar-free synthesis gas.

Separately, Xinhua reported that Shenhua Group plans to expand the output of its direct coal liquefaction plant in Mongolia to 6 million tonnes a year by 2010. The project currently is slated to produce 3.2 million tonnes of fuel a year. The first phase, at a cost of 24.5 billion yuan (US$3.15 billion) begins production at the end of 2007.

Shenhua is also building indirect coal liquefaction plants in partnership with Sasol and Shell.

Shenhua’s first direct coal liquefaction train is due to come online in 2007.

Indirect coal liquefaction (ICL) first gasifies the coal and then uses a Fischer-Tropsch process to convert the syngas into products. Direct coal liquefaction (DCL) cuts out the intermediate gasification step, and uses high-pressure hydrogenation to take the coal directly to the end product. DCL is based on the Bergius process, discovered by Friedrich Bergius in 1921 (slightly before Fischer and Tropsch).

(Bergius, who shared the Nobel Prize in Chemistry in 1931 with Carl Bosch for their contributions to the invention and development of chemical high-pressure methods, also tackled developing a process for the hydrolysis of cellulose in wood and similar substances to sugar for fermentation.)

According to the Headwaters Group, which is supplying the DCL technology to Shenhua for the Mongolian plant, one of the main differences between DCL and ICL is the quality of the raw liquid products.

DCL raw products contain more ring structure. Therefore DCL naphtha is an excellent feedstock for production of high-octane gasoline, while DCL distillate requires considerable ring opening (mild hydrocracking) to generate on spec diesel fuel. On the other hand, the straight-chain structure hydrocarbons produced by ICL technology result in high-cetane diesel fuel but ICL naphtha needs substantial refining (isomerization and alkylation) to produce on spec gasoline. Both processes produce low-sulfur, low-aromatic fuels after the refining step.

DCL plants produce more liquid fuel per ton of coal than ICL plants. However, ICL plants are better suited for polygeneration of fuels, chemicals and electricity than DCL plants.

—American Coal Council publication, p. 50

In addition to the greenhouse gas emissions issues attendant to both processes—which would need to be handled with some form of capture and storage—DCL liquids have a high content of polycyclic aromatic hydrocarbons (PAHs), a class of organic compounds that include potent mutagenic and carcinogenic compounds.

Further hydrogenation can deal with the PAHs, but at additional financial and energy cost.

Overall, China will invest more than one trillion yuan (US$128 billion) to develop alternative coal-based synthetic fuels projects to ease the country’s dependence on oil imports. The projects aim to produce 30 million tons (about 600,000 barrels per day) of coal liquids and 20 million tons of dimethyl ether (DME) by 2020. Coal-to-olefin (CTO) output is expected to hit 8 million tons and coal methanol to reach 66 million tons. (Earlier post.)

Resources:

• The GSP Process: Entrained-flow Gasification of Different Types of Coal (Future Energy)

• Siemens Global Gasification and Integrated Gasification Combined Cycle Update (Siemens)

• A comparison of direct and indirect liquefaction technologies for making fluid fuels from coal (Robert H. Williams and Eric D. Larson, 2003)