Gas coal

Pyrex glass is preferable, but this requires an oxy-coal gas blowpipe for manipulation. Suitable melting point tubes may be purchased from dealers in scientific apparatus or chemicals. It is, however, excellent practice, and an essential part of his training, for the student to learn to prepare bis own capillary tubes. 

The main problem in this technique is getting the atoms into the vapour phase, bearing in mind the typically low volatility of many materials to be analysed. The method used is to spray, in a very fine mist, a liquid molecular sample containing the atom concerned into a high-temperature flame. Air mixed with coal gas, propane or acetylene, or nitrous oxide mixed with acetylene, produce flames in the temperature range 2100 K to 3200 K, the higher temperature being necessary for such refractory elements as Al, Si, V, Ti and Be. 

A comparison of the characteristics associated with propellant burning, explosive detonation, and the performance of conventional fuels (see Coal Gas, NATURAL Petroleum) is shown ia Table 1. The most notable difference is the rate at which energy is evolved. The energy Hberated by explosives and propellants depends on the thermochemical properties of the reactants. As a rough rule of thumb, these materials yield about 1000 cm of gas and 4.2 kj (1000 cal) of heat per gram of material. 

The discovery that usehil chemicals could be made from coal tar provided the foundation upon which the modem chemical industry is built. Industrial chemistry expanded rapidly in the late nineteenth century in German laboratories and factories where coal-tar chemicals were refined and used in synthesis of dyes and pharmaceuticals. But coal-tar production has an eadier origin, dating back to the discovery by William Murdock in 1792 that heating coal in the absence of air generated a gas suitable for lighting. Murdock commercialized this technology, and by 1812 the streets of London were illuminated with coal gas (1). 

Substitute or synthetic natural gas (SNG) has been known for several centuries. When SNG was first discovered, natural gas was largely unknown as a fuel and was more a religious phenomenon (see Gas, NATURAL) (1). Coal (qv) was the first significant source of substitute natural gas and in the early stages of SNG production the product was more commonly known under variations of the name coal gas (2,3). Whereas coal continues to be a principal source of substitute natural gas (4) a more recendy recognized source is petroleum (qv) (5). 

Coal can be converted to gas by several routes (2,6—11), but often a particular process is a combination of options chosen on the basis of the product desired, ie, low, medium, or high heat-value gas. In a very general sense, coal gas is the term appHed to the mixture of gaseous constituents that are produced during the thermal decomposition of coal at temperatures in excess of 500°C (>930°F), often in the absence of oxygen (air) (see Coal CONVERSION PROCESSES, gasification) (3). A soHd residue (coke, char), tars, and other Hquids are also produced in the process ... 

J. F. Farnsworth, Proceedings Coal Gas Fundamentals Symposium, Institute of Gas Technology, Chicago, 1979. 

Gas oil fractions (204—565°C) from coal Hquefaction show even greater differences in composition compared to petroleum-derived counterparts than do the naphtha fractions (128). The coal-gas oils consist mostly of aromatics (60%), polar heteroaromatics (25%), asphaltenes (8—15%), and saturated... 

Large-scale recovery of light oil was commercialized in England, Germany, and the United States toward the end of the nineteenth century (151). Industrial coal-tar production dates from the earliest operation of coal-gas faciUties. The principal bulk commodities derived from coal tar are wood-preserving oils, road tars, industrial pitches, and coke. Naphthalene is obtained from tar oils by crystallization, tar acids are derived by extraction of tar oils with caustic, and tar bases by extraction with sulfuric acid. Coal tars generally contain less than 1% benzene and toluene, and may contain up to 1% xylene. The total U.S. production of BTX from coke-oven operations is insignificant compared to petroleum product consumptions. 

In 1982, Texaco started up a 900 t/d gasifier at Southern California Edison s Cool Water faciUty. This was the first coal gasification plant to operate in an electric utihty environment, providing coal gas as fuel to a GE-frame 7E combustion turbine. The Cool Water gasification plant operated for over... 

The product gas after cleanup consists of primarily CO and H2. Combustion of coal gas in high firing-temperature gas turbines converts virtually all of the CO to CO2, and gas turbine exhaust is expected to contain no more than 10 ppm CO when operating at design conditions. Carbon monoxide emissions from a CGCC plant are thus expected to be around one-tenth those of a modem coal-fired plant equipped with low NO burners. 

Particulate removal from the coal gas is effected either through a series of dry-sofld and wet-sofld removal steps or through the use of dry soflds filters, so that the gas fed to the combustion turbine is essentially free of suspended particulates. The emissions of total suspended particulates (TSP) from a CGCC plant are about one-third those from a comparable pulverized coal plant equipped with a fabric filter and EGD unit. 

Eor shifting coal-derived gas, conventional iron—chromium catalysts can be used. Because coal gas has a significantly higher concentration of carbon monoxide than is found in gas streams in conventional refineries, the catalyst must be able to withstand high thermal loads. However, potential catalyst poisons such as phenol and other hydrocarbons are not a concern in entrained-bed gasifiers. 

Miscellaneous Fuels A variety of gases have veiy minor market shares. These include reformed gas, oil gases, producer gas, blue water gas, carbureted water gas, coal gas, and blast-furnace gas. The heating values of these gases range from 3.4 to 41 MJ/m (90 to 1100 Btii/ftq. They are produced by pyrolysis, the water gas reaction, or as by-products of pig-iron production. 

Coke-oven gas Producer gas Water gas Carbureted water gas Synthetic coal gas... 

Naphthalene Prttpane Coal gas (town gas) Petroleum Toluene Water gas Hydrogen ... 

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