Coal effect

Pyrolysis of coal effectively occurs in a plasma jet of nitrogen or Ar-N2 mixture (Ar + 10% N2). The major products of pyrolysis are acetylene, hydrogen cyanide (HCN), and CO. When the coal pyrolysis occurs in a plasma jet of pure nitrogen, the major product of pyrolysis is HCN, whereas acetylene dominates if the amount of nitrogen in the Ar-N2 mixture is relatively small. The yield of HCN in the pyrolysis in the pure nitrogen plasmajet is close to the amount of volatile compounds in the coal. Acetylene yield in this case is about... 

Extraction Rate and Agent Initially, the extraction process proceeds rapidly and becomes slow after a few hours (25). An extracting agent is effective if at 473 K the liquid is capable of dissolving 20 to 40% of a bituminous coal. Effective extracting agents are pyridine, picolines, aliphatic amines, ethylenediamine, phenol, cresol, o-phenylphenol, acetophenone, furfural etc. while benzene, trichloroethylene etc. are less effective. 

Guha, O.K. Roy, J., and Choudhury, A., Non-polar carbon adsorbents from coal Effect of coal rank studied by molecular probe chromatography. Fuel, 70( 1), 9-12 (1991). 

The presence of coal effectively doubles the head losses. The deposition velocity is expressed from Equation 4-24 ... 

Ability to gasify all coals effectively regardless of coal rank, caking characteristic, or the amount of coal fines... 

In the case of UCG, it is presumed that h, generated is partly transferred to the wall made of coal or char. As the heat conducted to the wall is utilized in water gas reaction, pyrolysis, drying, and preheating of coal effectively. Consequently, the reactor of UCG can be thought as adiabatic one, and most of h, turns to the sensible heat of gas in the reactor. 

Fuel switch. The choice of fuel used in furnaces and steam boilers has a major effect on the gaseous utility waste from products of combustion. For example, a switch from coal to natural gas in a steam boiler can lead to a reduction in carbon dioxide emissions of typically 40 percent for the same heat released. This results from the lower carbon content of natural gas. In addition, it is likely that a switch from coal to natural gas also will lead to a considerable reduction in both SO, and NO, emissions, as we shall discuss later. 

Utility costs vary enormously. This is especially true of fuel costs. Not only do costs vary considerably between different fuels (coal, oil, natural gas), but costs also tend to be sensitive to market fluctuations. Contractual relationships also have a significant effect on fuel costs. The price paid for fuel may depend very much on how much is purchased. 

Different types of other coal liquefaction processes have been also developed to convert coals to liqnid hydrocarbon fnels. These include high-temperature solvent extraction processes in which no catalyst is added. The solvent is usually a hydroaromatic hydrogen donor, whereas molecnlar hydrogen is added as a secondary source of hydrogen. Similar but catalytic liquefaction processes use zinc chloride and other catalysts, usually under forceful conditions (375-425°C, 100-200 atm). In our own research, superacidic HF-BFo-induced hydroliquefaction of coals, which involves depolymerization-ionic hydrogenation, was found to be highly effective at relatively modest temperatnres (150-170°C). 

Boghead coal Bogue calculation Bohlin rheometer Bohr effect Boilers... 

Coal is expected to be the best domestic feedstock alternative to natural gas. Although coal-based ammonia plants have been built elsewhere, there is no such plant in the United States. Pilot-scale projects have demonstrated effective ammonia-from-coal technology (102). The cost of ammonia production can be anticipated to increase, lea ding to increases in the cost of producing nitrogen fertilizers. 

The main difference between gas works and coke oven practice is that, in a gas works, maximum gas yield is a primary consideration whereas in the coke works the quality of the coke is the first consideration. These effects are obtained by choice of a coal feedstock that is suitable to the task. For example, use of lower volatile coals in coke ovens, compared to coals used in gas works, produces lower yields of gas when operating at the same temperatures. In addition, the choice of heating (carbonizing) conditions and the type of retort also play a principal role (10,35). 

Process Pa.ra.meters, The most notable effects ia gasifiers are those of pressure (Fig. 1) and coal character. Some initial processiag of the coal feedstock maybe requited. The type and degree of pretreatment is a function of the process and/or the type of coal (see Coal conversion processes, CLEANING AND DESULFURIZATION). 

Fixed orSlowlj M-OvingFeds. For fuel-bed burning on a grate, a distillation effect occurs. The result is that hquid components which are formed volatilize before combustion temperatures are reached cracking may also occur. The ignition of coal in a bed is almost entirely by radiation from hot refractory arches and from the flame burning of volatiles. In fixed beds, the radiant heat above the bed can only penetrate a short distance into the bed. 

The fuels Hsted in Table 2 are generally representative of fuels to be encountered over the range of industrial furnaces and, depending on the type (cooled or refractory wall), exhibit operating temperatures considerably different from adiabatic values. The choice of fuel is dependent upon a number of factors including cost, availabiUty, cleanliness, emissions, reflabiUty, and operations. Small furnaces tend to bum cleaner, easier to use fuels. Large furnaces can more effectively use coal. 

The tiansition from a choice of multiple fossil fuels to various ranks of coal, with the subbituminous varieties a common choice, does in effect entail a fuel-dependent size aspect in furnace design. A controlling factor of furnace design is the ash content and composition of the coal. If wall deposition thereof (slagging) is not properly allowed for or controlled, the furnace may not perform as predicted. Furnace size varies with the ash content and composition of the coals used. The ash composition for various coals of industrial importance is shown in Table 3. 

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