Availability of coals

Thus, DOE said, utilities will get different treatment, depending upon the availability of coal. If a utility burning gas or oil can readily convert to coal, it will still be ordered to do so. But if conversion to coal isn t practical in the next few years for utilities currently burning oil or gas, they ll be urged to keep using gas or to switch to gas from oil."... 

Another important factor in the availability of coal is an adequate supply of transportation facilities, particularly railroad hopper cars. There is little or no storage at the mines except for unit train shipments, so mines generally cannot operate without an adequate supply of coal cars, wluch determines the number of days of active mine operation. Because of the close a Bnity of coal and rail transportation, the deterrents to expanded coal productive capacity also affect the development of new transportation facilities. Of considerable importance in the future will be an increase in the number of unit trains, which help to reduce transportation costs and the potentials for more coal slurry pipelines and for mine-mouth generating plants for the extra-high-voltage transmission of coal-produced electricity. 

In addition to the requirement of using coal with a low sulphur content, there is also the objection to strip mining this material. The undesirability of this also contributes to the uncertainty in the estimates of the true availability of coal. 

The Industrial Revolution, which began in Britain in the eighteenth century, was based on the availability of coal to power steam engines and, moreover, coal was cheaper and much more efficient than wood in most steam engines. International trade expanded exponentially when coal-fed steam engines were built for the railways and steamships in the 1810-1840 period. 

Figure 2.4 Availability of coal-based integrated gasification combined cycle (IGCC) power plants (data adapted from Ref. [36]).

As early as 2500 bce m India indigo was used to dye cloth a deep blue The early Phoenicians discovered that a purple dye of great value Tyrian purple could be extracted from a Mediterranean sea snail The beauty of the color and its scarcity made purple the color of royalty The availability of dyestuffs underwent an abrupt change m 1856 when William Henry Perkin an 18 year old student accidentally discovered a simple way to prepare a deep purple dye which he called mauveme from extracts of coal tar This led to a search for other synthetic dyes and forged a permanent link between industry and chemical research... 

Methanol. If methanol is to compete with conventional gasoline and diesel fuel it must be readily available and inexpensively produced. Thus methanol production from a low-cost feed stock such as natural gas [8006-14-2] or coal is essential (see Feedstocks). There is an abundance of natural gas (see Gas, natural) woddwide and reserves of coal are even greater than those of natural gas. 

Although small amounts of hquids are produced during coal pyrolysis, significant amounts of coal-derived hquids did not become available until after the... 

Rates of production of lignite have continued to increase since 1960. In 1980 374 x 10 tons of coal equivalent (tee) were produced. One tee is the amount of energy available from combustion of a metric ton of coal having a heat content of 29.3 GJ, ie, 29.3 MJ/kg (12, 600 Btu/lb) (3). In 1989 this figure had risen to 460 x 10 tee. This 23% increase is somewhat less than the 28% increase in hard coal production during this period (see Coal). In 1990 the 1130 X 10 metric tons of lignite produced worldwide represented 24% of the total coal production. 

When energy alternatives are available, a compromise between cost and quaHty is often realized. Blending of coals can be used to achieve more desirable quaHties. For example, lignite from the former Yugoslavia has been blended with, and even substituted for, the highly caking Rasa coal used for coke production in the iron (qv) and steel (qv) industries. 

Until 1960—1970, in countries where natural gas was not available, large amounts of coal were carbonized for the production of town gas, as well as a grade of coke which, although unsuitable for metallurgical use, was satisfactory as a domestic fuel in closed stoves. The early cast-iron and siUca horizontal retorts used at gasworks were replaced by continuous vertical retorts. These operated at flue temperatures of 1000—1100°C. The volatile products were rapidly swept from the retort by the introduction of steam at 10—20% by weight of the coal carbonized. 

Crude Tar. Current world output of crude tar is estimated at between 11 and 12 x 10 t/yr. Table 8 gives such details as are available. The amount distilled is about 10 x 10 t/yr. Production of low temperature tar included in the U.K. total for 1994 was 35,000 t at its 2enith 203,000 t were produced in 1975. World production of all coal tar in 1975 was estimated at 17.3 x 10 t. The quantity of tar distilled at five yearly intervals since 1984 is shown in Table 9. Some comparative figures for the prices of coal-tar bulk products for 1982 and 1994 are given in Table 10. 

Although froth flotation is recognized as the best available fine coal cleaning technique, it becomes iueffective when the particle size is much smaller than 0.1 mm or when the feed contains a large amount of clay, resulting iu low coal recovery or poor selectivity. A solution to these problems is the use of modified flotation devices. 

Vinyl carbazole is obtained by reacting carbazole, readily available as a byproduct of coal tar distillation, with acetylene in the presence of a catalyst and solvent under pressure Figure 17.7). 

In addition to supplying transportation fuels and chemicals, products from coal liquefaction and extraction have been used m the past as pitches for binders and feedstocks for cokes [12]. Indeed, the majority of organic chemicals and carbonaceous materials prior to World War II were based on coal technologies. Unfortunately, this technology was supplanted when inexpensive petroleum became available dunng the 1940s. Nevertheless, despite a steady decline of coal use for non-combustion purposes over the past several decades, coal tars still remain an important commodity in North America. 

Consider coal burning in a boiler house. The assessor may not be able to measure the mass of sulfur dioxide (SOj) leaving the boiler stack, because of access problems and the lack of suitable sampling ports on the stack. The only information available is that the coal is of soft quality, containing 3% sulfur by weight and, on average, 1,000 kg of coal is burned each day. 

In this study detailed fault trees with probability and failure rate calculations were generated for the events (1) Fatality due to Explosion, Fire, Toxic Release or Asphyxiation at the Process Development Unit (PDU) Coal Gasification Process and (2) Loss of Availability of the PDU. The fault trees for the PDU were synthesized by Design Sciences, Inc., and then subjected to multiple reviews by Combustion Engineering. The steps involved in hazard identification and evaluation, fault tree generation, probability assessment, and design alteration are presented in the main body of this report. The fault trees, cut sets, failure rate data and unavailability calculations are included as attachments to this report. Although both safety and reliability trees have been constructed for the PDU, the verification and analysis of these trees were not completed as a result of the curtailment of the demonstration plant project. Certain items not completed for the PDU risk and reliability assessment are listed. 

This report presents a set of failure rate and time-to-restore data for typical components of a coal gasification combined cycle power generation unit. The data was used to examine the reliability and availability of a generic power generation unit using risk analysis models. 

The primary cost variable in barge shipments is fuel a midsize towboat can consume 5000 gal (18.9 kl) of diesel fuel daily. Barge shipments are also dependent on weather conditions low water or frozen rivers and canals can halt shipments. As ivith ocean vessels, the barges that move coal also ship other bulk commodities, making the rates and availability of barges for coal shipments dependent on conditions in other markets. Backliaiils (i.e., shipment of one commodity to a terminal and return with a different product) can substantially reduce coal rates. 

The sulfur content of coals available to utilities ranges from about 4 percent in high-sulfur coals to less than 1 percent in some Western coals. Although transportation costs maybe higher for Western coals, many Eastern utilities elect to burn Western coals to comply with increasingly stringent SO, regulations. 

---