Liquefaction reaction parameters

A successful two-stage liquefaction process will need to maintain a relatively consistent H-donor cs ability in its recycle solvent arnl should react positively to rectify variations in the consistency outside acceptable limits. In order to react to these variations, the process will need the ability to adjust reaction parameters (e.g. pressure, temperature, throughput, catalyst activity), probably according to its H-donor ability. Hence there is a need to monitor the H-donor content of the solvent. 

For a better understanding of the liquefaction reaction in water, especially during the heating up period, we investigated a comparative study of different parameters as follows the influence... 

Fundamental studies of coal liquefaction have shown that the structure of solvent molecules can determine the nature of liquid yields that result at any particular set of reaction conditions. One approach to understanding coal liquefaction chemistry is to use well-defined solvents or to study reactions of solvents with pure compounds which may represent bond-types that are likely present in coal [1,2]. It is postulated that one of the major routes in coal liquefaction is initiation by thermal activation to form free radicals which abstract hydrogen from any readily available source. The solvent may, therefore, function as a direct source of hydrogen (donor), indirect source of hydrogen (hydrogen-transfer agent), or may directly react with the coal (adduction). The actual role of solvent thus becomes a significant parameter. 

It is difficult to determine an optimum time or temperature for the liquefaction process because reaction time and temperature are interactive variables. Reaction temperature is the most important factor according to our research, in agreement with work reported by Corbett and Richards (68) in terms of the amount of volatile products formed from cellulose. Inclusion of lignin and hemicellulose in a wood substrate may alter the optimum temperature, but should not alter the fact that reaction temperature is controlling. However, oil yield itself may not be a suitable parameter for measuring the efficiency of the liquefaction process. A high yield of oil may... 

Oilj water and gas exit the cooling lock and enter the collection vessel In all, over 30 runs have been made, and of these 13 have been completely analysed in terms of carbon balance, elemental analysis and quantification of the various phases For chipped poplar, the varied parameters have been steam temperature, injection time, water level in steam generator and total reaction time The liquefaction of non-standard poplar in the form of dowels has also been studied ... 

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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