Coal-to-Chemicals

Gasification and the chemical industry have a long history, with modern gasification used by the industry since the 1950s. With rising crude oil prices, and concerns about its ability to meet demand into the future, coal gasification is increasingly being used as a source for chemical production. Please see the Markets section below for more information about the growth of the coal-to-chemicals industry.

In coal-to-chemicals, synthesis gas (syngas)—a gaseous mixture of primarily carbon monoxide and hydrogen—is produced by gasification of coal (note: other feedstocks are also capable of gasification to produce syngas). The syngas can then be fashioned into a number of useful chemical building blocks, like methanol or acetyls for example. Ammonia and urea are significant products of coal-to-chemicals for use in fertilizers. The syngas composition—specifically, the ratio of hydrogen to carbon monoxide—is important for some downstream processes, so a water-gas shift reactor is sometimes used to change this balance. Different required composition ranges and the water-gas shift reaction are discussed in the more detailed subsections at right.

This page will serve as a brief introduction to the coal-to-chemicals technology and markets as well as the advantages and challenges of coal-to-chemicals.

Market
Producing chemicals from coal through gasification has been used since the 1950s and, as such, has already carved out a share of the chemicals market. One important example is the production of methanol, of which, 9% worldwide is produced by gasification (Gasification, Higman C., Van der Burgt M., 2003). Many chemicals are high-value products and gasification provides the option of using relatively inexpensive coal to produce them. Methanol and ammonia are especially important as key building blocks for further chemical synthesis. According to the 2010 Worldwide Gasification Database, a survey of current and planned gasifiers, from 2004 to 2007 chemical production increased its gasification product share from 37% to 45%. From 2008 to 2010, 22% of new gasifier additions will be for chemical production. (For more on the markets for other gasification products and in general, see the Markets section.)

	Ammonia storage tanks in Starbuck, MN. Photo by Nic McPhee

The quickly growing Chinese economy has given rise to a number of coal-to-chemical facilities, some already operating—21 plants came online from 2004 to 2007—and many planned for the near future. China, like the United States, has large domestic coal supplies and growing demand for chemical products like ammonia-based fertilizers and methanol, for direct use and as a building block in other chemical syntheses. The World Gasification Database 2007 shows that of 41 coal-to-chemicals plants worldwide in operation or planned by 2010, 35 are in China: 22 active and 13 planned.

While no new United States coal-to-chemical plants are planned to come online before 2010 (see below for information on the existing Eastman Coal-to-Chemicals Plant), the U.S. chemical industry as a whole shipped $629.3 billion in 2007, a 9% increase over 2006. In particular, agricultural chemicals, like ammonia-based fertilizers (see the Great Plains Synfuels Plant for more on the coproduction of ammonia and SNG) rose 14.5% in price. Overall, the high price of natural gas led to a 7.4% drop in agricultural chemical production, which indicates an opportunity for coal-to-chemical plants (data from Facts & Figures, July 7, 2008, Chemical & Engineering News).

	Eastman Coal-to-Chemicals Plant Kingsport, TN

Eastman Coal-to-Chemicals Plant
In addition to agricultural chemicals like ammonia and urea for fertilizer, methanol is a substantial product of coal-to-chemicals gasification worldwide. One of the earliest and most notable coal-to-chemicals plants in the United States is owned and operated by Eastman Chemical Company and based in Kingsport, Tennessee, where the plant produces methanol and acetyl chemicals, produced from methanol and carbon monoxide through a reaction called carbonylation. Acetic acid and acetic anhydride are commonly used in pharmaceutical and industrial applications and can be processed into products like paints, fibers, photographic film, tool handles, cigarette filters and more. Methanol also has important uses, as a fuel or fuel additive, for example.

The Eastman coal-to-chemicals plant, first opened in 1983, was designed to process syngas from the gasification of Southwest Virginia and Eastern Kentucky coal into 500 million pounds per year of acetic anhydride and acetic acid, enough to supply half of Eastman’s raw acetyl needs. Acetyl chemicals are important to many of Eastman’s products, but especially those at the Kingsport site, where five of seven manufacturing divisions rely on acetyls as a raw material. The success of the operation led to a decision to expand the plant capacity to an excess of 1 billion pounds per year to meet all of Eastman’s needs, a testament to the ability of gasification to reliably, economically, and efficiently meet the coal-to-chemical requirements of Eastman’s Kingsport facility.

	Huayi Group coal to chemical plant, Shanghai, China. Photo courtesy Huayi and Praxair.

Huayi Group Coal-to-Chemicals Plant
Located in Shanghai, the Huayi Group’s facility is one of the earliest and most successful coal-to-chemical plants in China. Partnered with Praxair for air separation technology and currently using GE gasifiers, it produces 800 kilotons (kt) methanol and 500 kt glacial acetic acid (glacial indicates without water, in this case). The plant brought in $4.68 billion in revenue in 2007 and intends to develop further downstream processes to balance acetic acid production and to manufacture products like olefins, dimethyl ether, and others. (Huayi – Praxair Partnership in Integrated Coal to Chemical Site, Presentation, Gasification Technologies Conference, Oct 7, 2008.)

Advantages
The synthesis of many chemicals often begins with a hydrocarbon source, frequently crude oil or natural gas. As both crude and natural gas increase in price and increased demand raises questions about supply, coal is an attractive solution. Coal can be cleanly gasified and is relatively inexpensive and domestically abundant with estimates of over two centuries in reserve at current consumption rates. Producing chemicals from coal is a way to increase energy security and diversity and as the Eastman Coal-to-Chemicals plant has shown (described above), it can be done profitably and with good reliability. From a market standpoint, chemicals are growing in demand, especially in rapidly developing China. Environmentally, the syngas cleaning process can reduce emissions below regulated standards and is well-positioned if carbon dioxide capture becomes regulated. Although coal, petroleum and natural gas are most common, chemical production through gasification can potentially use a wide variety of feedstocks including refinery waste, biomass, and municipal waste. Steam produced by the gasification process can often be effectively integrated to meet a chemical plants needs, increasing efficiency. Coal-to-chemicals is also well-suited to cogeneration with an IGCC power plant, because of the way each can respond to product demand, explained in more detail on the Co-generation page.

Challenges
Of the “coal-to-” processes, coal-to-chemicals is potentially the most stable, having been demonstrated by Eastman and several other projects to be profitable and reliable. Coal-to-chemicals technology is seeing a large market growth, especially in China, indicating confidence in the technology. However, challenges to coal-to-chemicals are still similar to the challenges that face other uses of gasification, mainly cost (capital and operating/maintenance) and availability. For the production of some chemicals like methanol, ammonia, acetyls, etc., the economics of coal-to-chemicals are favorable—the Eastman Coal-to-Chemicals plant is profitable, for example—and so cost is not a barrier to project realization. The economics of gasification can continue to be improved, however. Increased availability, either through new materials or better maintenance methods, is also an area where research and development could lead to substantial improvements. These general gasification challenges are discussed in the linked Challenges section. Research and development ideas are also discussed below and in the linked Research & Development section.

The Eastman Coal-to-Chemicals Plant in Kingsport, Tennessee, lists production rate, reliability, maintenance cost, and safety as primary importance to the facility’s operation. Increasing process efficiency to produce more product over a period of time or per coal input helps defer high initial capital costs. Related to, and perhaps more important than, production rate is reliability. An outage can have drastic consequences on the economics of a plant, so availability is an important factor to consider during planning. Through a well-defined maintenance schedule, redundant units, and improvements to problem areas (identified through a consistent “run review” schedule), the Eastman plant has been able to demonstrate over 98% gasifier uptime since 1986. Eastman also found that having more frequent, planned maintenance—even though it increased turnaround time—has lowered the number of failures, increased production, and decreased overall maintenance costs. Similarly, by having plans and procedures in place, the plant has been able to establish an excellent safety record.

Problem areas identified by Eastman are similar to other gasifiers, mainly materials issues such as feed injector (burner) failure from corrosion and refractory wear. Eastman has found that routine maintenance and improvements from research and development have substantially reduced these problems.

Research and Development
Many of the research and development avenues being undertaken for other gasification applications will also have beneficial results for coal-to-chemicals. For example, novel membrane-based air separation methods, show promise towards lowering the cost of pure oxygen supply for gasification. This would lower the energy and operation costs of the gasifier system and possibly the air separation unit’s capital costs. Clean-up methods could allow for higher temperature or more efficient syngas clean-up, which would also reduce costs associated with heat loss and operation. Research into increasing gasifier availability, much of which has been done by Eastman specifically related to coal-to-chemicals, will increase the productive and profitable periods of gasifier operation while also reducing maintenance costs.

Some of Eastman’s research and developments include:

• Fuel injector (burner) design improvements (six patents)
• Knowledge leading to improved shut-down/start-up procedures and decreased downtime
• Procedures for virtually seamless switching between gasifiers (cycling the spare) for maintenance

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