Hydrogen coal-derived

This chapter examines the opportunity for coal-derived hydrogen production technologies, with special emphasis on environmental considerations. It describes a state-of-the-art coal-to-hydrogen demonstration planned by the U.S. Department of Energy (DOE), a project now underway in North Dakota, and it explores the potential role of coal in a hydrogen energy economy of the future. 

The coal-to-hydrogen opportunity is real, and coal-derived hydrogen prices probably will not be subject to the market fluctuations that characterize natural gas prices. Coal-to-hydrogen production is already competitive elsewhere in the world, although economic considerations will dictate... 

Lanning B., Arps J. (2005), Cost-effective method for producing self-supported palladium alloy membranes for use in efficient production of coal derived hydrogen , Quaterly Techn. Prog. Report, DOE. 

The Pott-Broche process (101) was best known as an early industrial use of solvent extraction of coal but was ended owing to war damage. The coal was extracted at about 400°C for 1—1.5 h under a hydrogen pressure of 10—15 MPa (100—150 atm) using a coal-derived solvent. Plant capacity was only 5 t/h with an 80% yield of extract. The product contained less than 0.05% mineral matter and had limited use, mainly in electrodes. 

Processes for hydrogen gasification, hydrogen pyrolysis, or coking of coal usually produce Hquid co-products. The Hygas process produces about 6% Hquids as benzene, toluene, and xylene. Substitution of petroleum residuum for the coal-derived process oil has been used in studies of coal Hquefaction and offers promise as a lower cost technology (104). 

The H-Coal process could operate in one of two modes, depending on the desired product slate. In the "syn-cmde" mode, a fluid-bed coking unit was employed to maximize recovery of distillate from the Hquefaction product (Fig. 7a). When operated in the fuel oil mode (Fig. 7b), no coker was used and the primary product was a coal-derived low sulfur fuel oil. Total hydrogen demand on the process was also reduced in the latter mode of operation. 

Conventional coal-tar fuels from retorting Typical coal-derived fuels with different levels of hydrogenation Synthetic crude oils, by hydrogenation ... 

It has been demonstrated that a solvent-extraction procedure with N-methyl pyrrolidone is capable of producing coal-derived extract pitches with low-ash contents. Moreover, the properties of the pitches can be varied by partial hydrogenation of the coal prior to extraction. The yield of the pitches along with the physical and chemical properties of the cokes and graphites vai in an understandable fashion. 

It has been demonstrated that certain coal minerals, particularly iron compounds, catalyze the hydrogenation of coal-derived solvents (15). Mukherjee et al (16) hydrogenated float/ sink fractions of an Indian coal and found that the conversion increased with the amount of mineral matter present in the fraction. 

A schematic diagram of the liquid solvent extraction process is illustrated in Figure 1. Where the production of liquid hydrocarbons is the main objective an hydrogenated donor process solvent is used, whereas in the production of needle coke this is not necessary and a coal derived high boiling aromatic solvent may be used (e.g. anthracene oil). An essential economic requirement of the process is that a high extraction yield of the coal is obtained and this will depend upon the coal used and the digestion conditions. 

In step one, conversion of coal to a THF soluble product is rapid. The THF solubles are unstable in the presence of a coal derived solvent, but in the absence of hydrogen. In step two, the addition of molecular hydrogen to the system or of Tetralin to the solvent to increase hydrogen transfer to the coal increases the THF soluble conversion but does not lower the sulfur... 

Microautoclave data was also obtained with Wilsonville Batch I solvent utilizing Indiana V coal. Batch I solvent was obtained from Wilsonville in mid-1977. Other batches of recycle solvent were received later. Batch I solvent had inspections most like the Allied 24CA Creosote Oil used for start-up at the Wilsonville Pilot Plant. Succeeding batches of solvent received by CCDC showed substantial differences, presumably due to equilibration at various operating conditions. As the Wilsonville solvent aged and became more coal derived, the solvent aromaticity decreased with an increase in such compounds as indan and related homologs. The decrease in aromaticity has also been verified by NMR. A later solvent (Batch III) also showed an increase in phenolic and a decrease in phenanthrene (anthracene) and hydrogenated phenanthrene (anthracene) type compounds. 

Sternberg et al. (7) showed that the presence of asphaltenes in coal-derived oils caused a marked increase in the viscosity. This group also showed that these asphaltenes were acid-base complexes and that hydrogen bonding occurs between the acidic and basic components of asphaltenes (9, 10). Recent work (J3, 11) on coal liquefaction bottoms has shown the importance of hydrogen bonding on the viscosity of coal liquids. 

The liquefaction process is initiated by the thermal generation of coal-derived free radicals which in turn react with solvent to form solvent radicals by hydrogen abstraction. These sol-... 

Velazquez-Vargas, L.G. et al., Hydrogen Production from Coal derived Syn Gas Using Novel Metal Oxide Particles, Proceedings of the 23th Annual International Pittsburgh Coal Conference, Pittsburgh, PA, September 2006. 

The transportation fuels produced and marketed (Table 18.9)40 met the South African fuel specifications of that time and included some coal-derived liquids (not shown in Figure 18.5). Although the refinery originally produced no jet fuel, it was demonstrated that the hydrogenated kerosene range oligomers from olefin oligomerization over a solid phosphoric acid catalyst met the requirements for jet fuel.38 (Semisynthetic jet fuel was approved in 1999 and fully synthetic jet fuel was approved in 2008 DEFSTAN 91-91/Issue 6). 

Only a limited number of coal-derived pitches were examined by H NMR because of their low solubility in solvents commonly used m conventional proton magnetic resonance. Table 12 reports the distribution of hydrogen for three of the pitches. Unlike coal-tar pitches, which typically have over 85% of the hydrogen bonded to aromatic carbon, the materials listed in Table 12 are characterized by a high content of aliphatic hydrogen. 

Table 19. Effect of blending hydrogenated coal-derived pitch and coal extract on green coke yields, WVGS 13423 ...

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