Liquefaction processing, effect

Accounting of the work in the liquefaction process—effectiveness of various functions... 

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). 

Coal Characteristics and Their Effects in Liquefaction Process... 

The formation of these thermal fragments is necessary to catalytic liquefaction processes before the catalysts can become effective for hydrogen introduction, cracking and/or heteroatom removal (10). ... 

The present authors studied the solvolytic liquefaction process ( ,7) from chemical viewpoints on the solvents and the coals in previous paper ( 5). The basic idea of this process is that coals can be liquefied under atmospheric pressure when a suitable solvent of high boiling point assures the ability of coal extraction or solvolytic reactivity. The solvent may be hopefully derived from the petroleum asphaltene because of its effective utilization. Fig. 1 of a previous paper (8) may indicate an essential nature of this process. The liquefaction activity of a solvent was revealed to depend not only on its dissolving ability but also on its reactivity for the liquefying reaction according to the nature of the coal. Fusible coals were liquefied at high yield by the aid of aromatic solvents. However, coals which are non-fusible at liquefaction temperature are scarcely... 

The recovery, regeneration, and repeated reuse of the active catalyst are of prime importance in substantially reducing the overall cost of coal liquefaction. The used catalysts usually remain in the bottoms products, which consist of nondistillable asphaltenes, preasphaltenes, unreacted coal, and minerals. The asphaltenes and preasphaltenes can be recycled with the catalyst in bottoms recycle processes. However, unreacted coal and minerals, if present in the recycle, dilute the catalyst and limit the amount of allowable bottoms recycle because they unnecessarily increase the slurry viscosity and corrosion problems. Hence, these useless components should be removed or at least reduced in concentration. If the catalyst is deactivated, reactivation becomes necessary before reuse. Thus, the design of means for catalyst regeneration and recycle is necessary for an effective coal liquefaction process. Several approaches to achieving these goals are discussed below. 

Effect of Liquefaction Processing Conditions on Combustion Characteristics of Solvent-Refined Coal... 

Although SRC-II was basically a thermal liquefaction process, it was most successful using bituminous coals with a high native pyrite content. Iron sulfides are well known to have catalytic properties for coal liquefaction. Recycling part of the ash-minerals-containing bottoms had two beneficial effects (1) it increased the pyrite concentration in the reactor feed, and (2) it increased the residence time for heavy components, thus giving them more time to hydrocrack to distillate products. A block flow diagram of the SRC-II process is shown in Fig. 19.19. 

Effect of Recycle on Liquefaction and Product Distribution. It Is Important that the product oil from a coal liquefaction process should have a low viscosity so that It could be used for preparing coal-oll slurries for recycling In a continuous liquefaction process. The product oil should also exhibit reactivity or solvency for the coal so that the viscosities do not deteriorate with prolonged recycling operation. 

Although the residence time of plastic melt in the dehydrochlorination process is very long, the amount of HCl gas evolved is less than in the liquefaction processes of Niigata and Sapporo. This may indicate that PVC and PVDC materials are removed effectively... 

Do a parairretric shidy for the Claude liquefaction process treated in Sec. 9.6 and Ex. 9.3. lir particular, show irrurrerically the effect of chairging tire draw-off ratio x oir other process variables. Perry s Chemical Engineers Handbook (footirote 7 is a source of data for irrethaire. 

For the conversion of biomass resources into useful chemicals and bio-ener, three major process types, direct combustion, gasification and liquefaction, are effective. Among them, liquefaction for liquid transpiration fuels is, in particular, important because it is difficult to replace them with other energy forms. Thus, a study of the liquefaction of biomass is of interest. ... 

Tomlinson, G., Gray, D., and Neuworth, M., "Effect of Coal Rank on Direct Coal Liquefaction Processes Solvent Refined Coal (SRC-II) Process Experience," The MITRE Corp., 84W00308, July 1984. 

Recently, a new liquefaction approach based on the magnetocaloric effect has been proposed [115]. The method is based on the characteristics of some magnetic materials that heat up when placed in a magnetic held and cool down when removed from it. The magnetic refrigeration can develop its potentialities in terms of overall efficiency for liquefaction process, as it is theoretically able to exploit... 

For example, preheating coal at ca. 200°C (ca. 390°F) tends to have an adverse effect on the caking properties but may also increase ease of, say, gasification (insofar as caking coals can be difficult to gasify efficiently) (Chapters 20 and 21) and may also increase the ease of dissolution by organic solvents during liquefaction processes (Chapters 18 and 19). 

In the presence of a solvent that has hydrogen-donating capabilities, the free radicals may abstract hydrogen from the solvent and, thereby, achieve stabilization (Gun et al., 1979). Thus, processes that produce char or coke are limited because the reactive intermediates lose their reactive capabilities and yield lower-molecular-weight species. Coal pretreatment also appears to have a beneficial effect on the liquefaction process (Rindt et al., 1992 Shams et al., 1992). 

Health Effects of the Products and B-Products of Coal Liquefaction Processes... 

The slurry in their case was treated as a homogeneous phase and the solid distribution was not taken into account. The model parameters were estimated from the correlations proposed for the case of no solid suspension (two-phase system). The coal dissolution, hydrogenation and hydrodesulfurization were considered as the key reactions, in the model. Also, the effect of mass transfer on the liquefaction process has been investigated. The model predictions were found to be in good agreement with the experimental... 

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