Coal liquid residues

Cokers produce no liquid residue but yield up to 30% coke. Much of the low-sulfur product is used for electrolytic electrodes for smelting of aluminum. Lower-quality coke is burned as fuel im.xcd with coal. 

Table VII shows that the SCT-SRC plus upgrading yields significantly less gas and more liquid (residual material included) than the other processes. The hydrogen consumption in the two-step SCT process is higher than for the SRC-I process however, it is still lower than for the SRC-II process and significantly lower than for the H-Coal Syncrude operation.

A cogeneration system may use different fuels including natural gas, residual fuel oil, heating oil, diesel fuel and gasoline. Alternate fuel sources also include coal liquids or wood gas. 

Analytical separation and spectroscopic techniques normally used for petroleum crudes and residues were modified and used to characterize coal liquids, tar sands bitumens, and shale oils. These techniques include solvent extraction, adsorption, ion-exchange, and metal complexing chromatography to provide discrete fractions. The fractions are characterized by various physical and spectroscopic methods such as GLC, MS, NMR, etc. The methods are relatively fast, require only a few grams of sample, provide compound type fractions for detailed characterization, and provide comparative compositional profiles for natural and synthetic fuels. Additional analytical methods are needed in some areas. 

Since liquid sulfur dioxide boils at -10.2°C the extraction can be conducted at atmospheric conditions. The liquid sulfurdioxide is obtained by cooling the gas from the cylinder using a Dry Ice acetone bath. When a coal liquid (usually in a waxy state) is treated with liquid sulfur dioxide, the insolubles remain with the minerals and the coal fragments as a solid residue. TheS02 Solu-bles are separated from the insolubles by filtration. The filtrate is... 

When solvent refined lignite (SRL) produced from North Dakota lignite was treated with liquid sulfur dioxide, the bulk of the coal liquid dissolved except for the saturated hydrocarbons and the mineral rich residue. The S02-solublc part did not contain any saturated hydrocarbons. The THF extract of the insolubles was mostly alkanes ranging from n-dodecane (C 2H26 to n tetra tetrancontane (C44Hgg). 

Most coal liquids are composed of similar major chemical species, which may differ in exact composition. Liquid sulfur dioxide can be used to extract all the aromatic species of the coal liquid, free of saturated hydrocarbons and ash percursors. After removing the SO2 by degassing, distillation under reduced pressure can yield all the phenols and aromatic from the S02-solu-bles of the coal liquid. The residue, which is similar to GPC -fraction 2 of the S02 solubles, can be called coal asphaltenes. 

Also, it should be noted that shale oil is predominently in the middle distillate boiling range with low residue and naphtha content. The absence of resid in coal liquids results from the severe hydrogenation conditions imposed in the coal liquefaction processes and the use of the remaining residue for hydrogen production. For shale oil, the retorting process destroys most the residual materials leaving a syncrude that is mainly a distillate. 

This reactor allows easy data collection for high-temperature, high-pressure reaction systems that have difficult flow properties. This includes reactants that are solid at room temperature or mixtures of solids and liquids. Typical reactions performed in autoclaves are coal liquefaction, petroleum residuals and coal liquids upgrading, and high molecular weight hydrogenation experiments. 

COAL LIQUIDS (SRC-II) ARE IN MOST RESPECTS SUPERIOR TO RESIDUAL FUELS. THEY ARE MORE LIKE NO.2 DISTILLATES AND CAN SUBSTITUTE FOR PETROLEUM FUEL OILS IN THE MORE RESTRICTIVE ENVIRONMENTS. 

In other fuel markets, coal liquids can be more competitive. Industrial boilers presently are not amenable to stack gas scrubbing. The same is true of smaller utility plants. In particular, peak load units require a clean, storable liquid fuel as an alternative to natural gas. However, the high viscosity of primary coal liquefaction products is undesirable for many of these applications. Also, their residual sulfur and nitrogen contents may be excessive as emission standards become more stringent. 

Primary coal liquids must be upgraded in order to serve these markets. A logical route is to use current black oil conversion technology as practiced in the petroleum industry (2). An applicable UOP process is RCD Unibon (3). This comprises the direct processing of petroleum residues to reduce the sulfur and nitrogen content of heavy fuel oil or to combine desulfurization with conversion of residue to lighter, more valuable products. 

Several processes have been developed for coal liquefaction. Large-scale pilot plants have been in operation for the solvent-refining coal (SRC) process, and a pilot plant is being constructed for the H-Coal process, which is a direct catalytic process. Construction of demonstration plants is under consideration. The coal liquids produced from the current processes contain large amounts of residual fuels. They probably will be used initially as boiler fuels for stationary power plants. However, the nitrogen content of coal liquids is much higher than the petroleum residual fuels. The sulfur contents of coal liquids can vary considerably they depend on the type of coal and the liquefaction process used. Current coal liquefaction processes are capable of produc-... 

FLUID COKING A noncatalytic, thermal process for converting bitumen, petroleum residues, and coal liquids to lighter hydrocarbon fluids and gases. Developed by the Exxon Research Engineering Company and used commercially since 1954. See also FLEXICOKING. 

In addition to coal gasification, the formation of coal slurries is another new use of coal. A slurry is a suspension of fine particles in a liquid. Coal must be pulverized and mixed with water to form a slurry. The resulting slurry can be handled, stored, and burned in ways similar to those used for residual oil, a heavy fuel oil from petroleum accounting for 13% of U.S. petroleum imports. One hope is that coal slurries might replace solid coal and residual oil as fuels for electricity-generating power plants. However, the water needed for slurries might place an unacceptable burden on water resources, especially in the western states. 

Despite the well-known association and trapping of liquid hydrocarbons within the coal structure, liquid hydrocarbons apparently are continuously generated and expelled from coal. Nevertheless, residual quantities of liquid hydrocarbons are normally trapped within the coal macromolecular matrix. These trapped liquid hydrocarbons are probably converted to gas during continued coalification. 

Alkaline fuel cells required very pure hydrogen. That was problematic when hydrogen was produced from common fuels such as natural gas or coal. Any residual C02 in the hydrogen reacts with the liquid alkaline electrolyte, gumming up the electrodes microscopic pores and slowing the overall chemical reactions. 

Carbon oxide yield, std. cu. ft./lb. Feed hydrogen reacted, std. cu. ft./lb. Coal residue, lb./lb. coal Liquid products, lb./lb. coal Net m.a.f. coal hydrogasified, wt.% Carbon gasified, wt.%... 

The properties of manufactured graphites are determined by the microstructure of the carbonaceous mesophase which is formed during pyrolysis, usually between the temperatures of 370 C and 500°C. The characteristics of the final product can be measured in a qualitative way by examination of the mesophase micro-structure. Several coal liquid asphaltene and petroleum pitch samples have been screened in this way to determine their suitability as precursors for graphite materials. The physical and chemical properties of the mesophase formed from the samples and their pyrolyses residues were studied(1). It was found that the phenolic oxygen present either in the precursor or by addition during heat treatment suppresses mesophase formation by crosslinking and preventing the development of fluidity(2J>... 

The effect of additives on the asphaltene from the Catalytic Incorporated (Cat. Inc.) coal liquid product was studied. Asphaltene is defined as the pentane insoluble but benzene soluble part of the coal liquid. The fractionation procedure has been described in detail elsewhere(l) and is shown schematically in Figure 1. Some work was also done with A240 petroleum pitch. Elemental analysis for the Wyoming sub-bituminous coal. Cat. Inc. coal liquid product, and Cat. Inc. asphaltene and A240 petroleum pitch are shown in Table I. Measured amounts of the additive compounds to be studied were added to the Cat. Inc. asphaltene and petroleum pitch. The samples were pyrolyzed and the pyrolysis residues examined by cross polarized light microscopy. Elemental analyses of the residues were done. 

The cross polarized micrographs of the pyrolyzed residues of the Cat. Inc. original coal liquid and Cat. Inc. asphaltene are shown in Figure 2. The microstructures are primarily coarse mosaic textures. The following subsections describe the different additives of elemental and organic sulfur, organometallics and their combined effects on Cat. Inc. asphaltene during pyrolysis. 

Figure 2. Micrographs of pyrolyiei residues of Catalytic Incorporated (Cat. Ino.) coal liquid. Cat, Ino. asphaltene and the effect of elemental sulfur on mesophase formation in Cat. Ino. asphaltene.

Table VI. Elemental Analysis of the Sample Residues at Different Pyrolysis Temperatures Sample Cat Inc Coal Liquid Asphaltene + 6% Organic Sulfur + 800 ppm Nickel...

Power generation plants worldwide utilize various types of fuels (Figure 3.1), including low-price fuels to boil water the steam so produced is directed toward a turbine, which turns a generator (International Energy Agency 2008). Solid and liquid fuels like coal and residual fuel oils are used to obtain the required temperatures. Municipal solid waste (MSW) is also used for energy production (Lee et al. 2007). The steam at the low-pressure exit end of the turbine is condensed and... 

L. Bai, Y. Nie, Y. Li et al., Protic ionic liquids extract asphaltenes from direct coal liquefaction residue at room temperature. Fuel Proc. Technol. 108 (2013) 94-100. 

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