Science and Coal

Archive for the ‘family environment’ Category

High oil prices and the desire to reduce energy dependence in the United States have brought coal-to-liquid (CTL) technology to the forefront of the discussion about alternative fuel sources. Nearly 100 years old, CTL processes have long been used by countries lacking access to oil, most notably Germany, where production peaked during the 1940s; South Africa, which has been using CTL technology for fuel since the 1950s; and, more recently, China, where the Shenhua Group LLC began trial operation of the world’s first direct CTL facility in December 2008, and intends to eventually produce 1 million tons of coal-based liquid fuel a year. The U.S. Government promoted the development of CTL technologies following the oil shocks of the 1970s, but shelved the projects after the price of oil fell during the 1980s. In the current economic and political environment of the United States, with oil prices surpassing $100 per barrel in summer 2008 and generally projected to rise in the long term, synthetic fuel derived from coal may once again become economically viable, and several projects are in the initial design phase around the country. From an environmental standpoint, however, the carbon dioxide (CO2) emissions produced throughout the lifecycle of coal-based liquid fuel make it a less desirable option.

Turning Coal into Liquid Fuel
Coal can be converted into liquid fuel using several liquefaction processes; these processes can be divided into two general categories. The first category, indirect liquefaction, is a multi-step procedure that first requires the gasification of coal to produce a “syngas.” This syngas is then converted to liquid fuel via two methods: the Fischer-Tropsch process or the Mobil process. In the Fischer-Tropsch process, which is much more common, the syngas is then cleansed of impurities and subjected to further chemical refinement to produce a sulfur-free diesel or gasolinei. The initial syngas can be derived from coal alone, or from a coal / biomass mixture. The process is the same when biomass is included, but the amount of CO2 emitted during the process decreases as the proportion of biomass increases. In the less-common Mobil process, the syngas can be converted to methanol, which is subsequently converted to gasoline via a dehydration sequence. Indirect liquefaction of coal during Fischer Tropsch produces a significant amount of CO2 that is removed from the fuel as a necessary step during the final stages of the process. However, recent research has suggested a modified Fischer-Tropsch method that could significantly reduce CO2 emissions during liquefaction.ii
The second category, direct liquefaction, requires creating a chemical reaction at high temperatures and then using hydrogen gas and a catalyst to produce a liquid fuel. Direct liquefaction usually produces low-quality liquid fuel that is expensive to make compliant with U.S. standards for purity. Therefore, although the process is used in China, it is not a viable option for meeting the United States’ liquid fuel requirements and will not be discussed for the remainder of this brief. Read the rest of this entry »

Coal dust exposure is directly linked to severity of emphysema in smokers and nonsmokers alike, according to new research from the National Institute for Occupational Safety and Health (NIOSH).

‘In this study we have shown that coal mine dust exposure is a significant predictor of emphysema severity,’ said Eileen Kuempel, Ph.D., a senior scientist at NIOSH and lead author of the study.

The findings, which were reported in the August 1 issue of the American Thoracic Society’s American Journal of Respiratory and Critical Care Medicine (AJRCCM), highlight a health problem related to a growing industry. In the past 25 years, coal production has nearly doubled worldwide.

Dr Kuempel and colleagues compared lung autopsy results from 722 individuals, including 616 coal miners from West Virginia and 106 non-miners from West Virginia and Vermont. Those from West Virginia were collected from consecutive autopsies from 1957 and 1973 at the Beckley Southern Appalachian Regional Hospital as part of a black lung study. Those from Vermont were taken from consecutive autopsies performed at the University of Vermont between 1972 and 1978. Age at death, race, miner/non-miner status and smoking history were established where possible, and individual exposure to coal dust was estimated using work history data and job-specific dust exposure estimates. Read the rest of this entry »

The gas we use in our houses for heating and cooking may consist of gas manufactured from coal, natural gas, or a mixture of both. It may contain gas made from oil, too. There are several methods of manufacturing gas from coal. True coal gas, or coke-oven gas, is made by heating coal in an airtight oven. In this process called carbonization the coal changes into coke and gives off gas, together with ammonia, tar, and other impurities. Coolers and scrubbers remove impurities.

The coke produced in the ovens is used to make another kind of gas, called water gas, or blue gas. This is made by passing superheated (very hot) steam over white-hot coke. Carbureted water gas is blue gas which has been enriched by gases obtained by cracking, or breaking down oil by heating.

A further way of making gas from coal is called the Lurgi process. In this method, low-grade coal is heated very slowly under pressure. A mixture of steam and oxygen passing through the hot coal converts it into gas.

Each manufactured gas contains several inflammable gases. Coke-oven gas contains hydrogen, methane and carbon monoxide. Water gas contains only carbon monoxide and hydrogen. Oil gas enriches water gas by adding methane and other hydrocarbons which have a high heat value. The Lurgi process also produces hydrocarbons.