Effect on coal conversion

Different coals have been observed in the electron microscope when two pore-size ranges appear, one of >20 nm and the other <10 nm (52). Fine pores from 1—10 nm across have been observed using a lead impregnation procedure (53). Effectiveness of coal conversion processes depends on rapid... 

Many studies on direct liquefaction of coal have been carried out since the 1910 s, and the effects of kinds of coal, pasting oil and catalyst, moisture, ash, temperature, hydrogen pressure, stirring and heating-up rate of paste on coal conversion, asphaltene and oil yields have been also investigated by many workers. However, few kinetic studies on their effects to reaction rate have been reported. 

The effect of coal conversion and the reaction conditions on the composition of the solvent. 

Figure V. Effect of heat-up rate on coal conversion using presulfided catalyst precursors.

Experiments were run using 0.9%, 2.0%, 3.0%, and 5.0% sulfided molybdenum naph-thenate (as the percent of molybdenum in the resid) to select a catalyst level. Standard conditions of 30 min at 420°C at a 3 1 tetralin/resid ratio, 3 wt % sulfided molybdenum naphthenate catalyst, and 1500 psi of hydrogen pressure were selected for determination of the relative reactivity to hydroconversion of the coal-derived vacuum resids. It was found that both catalyst concentration and hydrogen pressure have strong effect on the conversion of coal to hydrocarbon. 

While there has been some discussion (Chapters 13 and 16) on the influence of physical process parameters and the effect of coal type on coal conversion, a note is warranted here regarding the influence of these various parameters on the gasification of coal. Most notable effects are those due to coal character, and often due to the maceral content... 

Implementation of the 1998 Kyoto Protocol, which is designed to reduce global carbon emissions, will have dramatic effects on fossil fuel usage worldwide. The Kyoto Protocol mostly affects delivered prices for coal and conversion of plants to natural gas, nuclear and/or renewable resources. However, as pointed out by the International Energy Agency, increased natural gas consumption in the United States may likely have the effect of increased reliance... 

However, coal reactivity as measured by total conversion to liquids and gases becomes less dependent on coal parameters as processing severity increases. The effect of process temperature in the hot-rod reactor was studied using three coals of varying properties. These were Waterberg, Sigma and Landau. At 650°C the conversion yields of these coals were 89, 90 and 88 per cent of the coal (dmmf) respectively. Within experimental error the conversion yields had converged to the same value, whereas at 500°C the conversion yields were 85, 75 and 65 per cent respectively. 

Figure 12 clearly shows the effect of iron sulfide content of the coal on total conversion and liquid product yield during hydrogenation. The conversion increased from about 52 per cent to 70 per cent using the hot-rod reactor with no added catalyst. The yield of toluene soluble product (oil plus asphaltene) increased from about 30 to 44 per cent with total sulfur increase from 1 to 6.5 per cent. Thus it would appear that iron sulfide can act catalytically in the dry hydrogenation reaction as well as in slurried reactions (15). 

Pyrolysis. In this context it is relevant to consider initially the effect of hydrogen contents on tar yields during pyrolysis (carbonization). This is particularly so, since, in all coal conversion processes little happens until the coal is at a temperature above that where active thermal decomposition normally sets in. In other words, all coal conversion processes may be regarded as pyrolysis under a variety of conditions which determine the nature of the primary decomposition and the reactions which follow. 

Also, many of the effects mentioned relate to the overall conversion. In coming to grips with the effects of coal characteristics, attention must be given to the quality as well as the quantity of liquid products obtained during conversion as well as to the rate at which the conversion occurs under various conditions. These aspects, which have not been considered in this presentation, call for careful experimentation where the emphasis is not on maximising conversion but on careful control of experimental conditions with termination of experiments at only partial conversion. 

The Effect of Coal Composition on Short Contact Time Conversion... 

SOLVENT EFFECTS ON SHORT TIME CONVERSION OF BELLE AYR SUBBITUMINOUS COAL (800°F, 3 min., 1500 psi H2)... 

Alcoholic KOH. We have reported on the use of isopropyl alcohol as an H-donor solvent in coal conversion, and specifically on the effects of the addition of strong bases such as KOH to the system (la). We found that i-PrOH brought about a conversion of Illinois No. 6 coal very similar to the conversion level obtained by Tetralin under the same conditions. These results are listed in Table IV in text, along with the results of more recent experiments using methanol as the solvent and adding KOH to the system (lb). 

SI. The effects of coal characteristics on conversions are generally much less pronounced under high-severity conditions en a combination of vehicle solvent, hydrogen overpressure and catalyst is employed. 

Conversions to pyridine-solubles for non-THF-extracted Linby coal were much greater with naphthalene than with phenanthrene and pyrene (Table m, pre-soaking at 250% has little effect on conversions) and, even after THF extraction, naphthalene conversions are comparable to those of pyrene. 

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