Pyrolysis of coal, plasma

Deuterium and Carbon-13 Tagging Studies of the Plasma Pyrolysis of Coal... 

Y Tigh temperature arc or plasma pyrolysis of coal produces acetylene... 

Acetylene yield is close to the total amount of volatiles, and its concentration in the gas is about 5-9%. Note that the acetylene yield in plasma pyrolysis of coal is practically independent of the amount of mineral components in the coal (Chakravartty et al., 1976). 

Table 10-10. Plasma Pyrolysis of Coal in Hydrogen Plasma Using Electric Arcs with Vortex and Magnetic Stabilization...

Nicholson, R. and Littlewood, K. 1972. Plasma pyrolysis of coal. Nature, 236 391-MX). 

Acetylene traditionally has been made from coal (coke) via the calcium carbide process. However, laboratory and bench-scale experiments have demonstrated the technical feasibiUty of producing the acetylene by the direct pyrolysis of coal. Researchers in Great Britain (24,28), India (25), and Japan (27) reported appreciable yields of acetylene from the pyrolysis of coal in a hydrogen-enhanced argon plasma. In subsequent work (29), it was shown that the yields could be dramatically increased through the use of a pure hydrogen plasma. 

Both the electric arc and the plasma jet have been used for the pyrolysis of coal. Acetylene is the principal hydrocarbon product, its yield being three times more in a hydrogen atmosphere than in an argon atmosphere. Since the thermodynamic stability of acetylene decreases rapidly below about 1600 K, the product gases must be quenched rapidly in order to prevent the decomposition of acetylene (Sect. 2). 

Various plasma jet devices have been used to study the discharge pyrolysis of coal. One such device used by a number of workers is shown in Fig. 16 240 245. A direct... 

Pyrolysis of coal with consequent formation of acetylene in an inert plasma environment is evidence that the carbon and hydrogen present in the coal are reacting,... 

Thermal Plasma Jet Pyrolysis of Coal in Argon, Hydrogen, and Their Mixtures Plasma Jet Production of Acetylene from Coal... 

Heating of Coal Particles and Acetylene Quenching During Pyrolysis of Coal in Argon and Hydrogen Plasma Jets... 

Coal pyrolysis often leads to intensive formation of small and mostly spherical particles with sizes of 60-90 nm (Kozlova Kukhto, 1976 Shimansky, 1979). They originate from fast plasma heating of the coal particles and intensive formation of volatile compounds inside of them. This leads to an explosive decay of the coal particles into very small sizes. Another source of the small particles is the formation of soot in the plasma system from the preliminarily formed acetylene (Razina et al., 1973). Other factors affecting heating and pyrolysis of coal particles are the plasma-gas temperature and residence time of the... 

Figure 10-38. Yields of (l)HCN and(2)acety-lene during pyrolysis of coal in nitrogen plasma as a function of percentage of volatiles in the coal.

Pyrolysis of Coal in Thermal Nitrogen Plasma Jet with Co-Production of Acetylene and Hydrogen Cyanide... 

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... 

Direct Pyrolysis of Coal with Production of Acetylene (C2H2) in Arc Plasma of Argon and Hydrogen... 

Vdovenko, M.I., Ibraev, Sh.Sh., Messerle, VE. (1987), Plasma Gasification of Coals with Utilization of Mineral Fraction, in Plasma Gasification and Pyrolysis of Low Quality Coals, p. 59, Energy Institute, ENIN, Moscow. 

Some of the techniques that have been employed to study the flash pyrolysis of coal are (1) laser, (2) microwave, (3) flash tube, (4) plasma, (5) electric arc, (6) shock tube, (7) electric current, and (8) entraining gas (for example, see Hanson and Vanderborgh, 1979 Howard, 1981a,b Nelson et al., 1988 Mackie et al., 1990 Plotczyk et al., 1990 Maswadeh et al., 1992 Monsef-Miizai et al., 1992 Pyatenko et al., 1992). Most of the techniques can, at the present time, be classed as research tools that are useful as characterization techniques but the entraining gas technique is under serious consideration for commercialization. In fact, each particular method has some unique aspect that, because of the novelty of the concept, makes a brief discussion here. 

Plotczyk, W.W., Resztak, A., and Szymanski, A. 1990. Plasma pyrolysis of brown coal. Journal de Physique... 

The pyrolysis products are quite stable in this case. This plasma process also has an advantage compared to the conventional process described by the same chemical formula (10-35). The conventional process requires the application of coke, whereas the plasma-chemical one starts directly from coal. In the experimental system of plasma production of calcium carbide (CaC2), the size of the coal particles is 8-44 pm and the molar ratio between carbon (of coal) and CaO is in the range 1-3. The experimentally achieved conversion degree in the optimal regime of the process is 90% for caibon and 70% for CaO. Achieving higher... 

Razina, G.N., Fedoseev, S.D., Gvozdarev, V, Staroverov, VA. (1976), Influence of Gas-Dynamic Factors on the Gas-Phase Products of Coal Pyrolysis in Conditions of Plasma Temperatures, in Modern Processes of Conversion of Solid Fuels, Adv. of Moscow Institute of Chemical Engineering (Mendeleev University), vol. 91, p. 94, Moscow. 

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